The Model Locomotive : I Ts De Si Gn an D Con Struction

,THE

M O D E L LOCO MOT IVE .

ITS DESl GN AN D CON STRUCTION

A P ractical M anual on M e B uil ding and M anag ement of

' ' ’ M zmature R ail w ay E ngz nes

H E N RY G R E E N L Y m g,

’ ’ Contaz mng 370 I l l ustrations and 9 F aiding P l ates

1 A A A A A

L ON D ON

PE R CIV AL M AR S H AL L 8: CO.

’ — E T E C. 26 29 POPPIN S COU RT,FL E E T ST RE , .

AUTHOR’S PREFACE

I N submitting this volume to the general reader a word or in . ‘ two b hn is e explanation of its o jects d scope p rhaps necessary. The book deal s primarily with working model locomotives in all sizes,and, for the most -part,with those built for the instruction and amuse a e I ment of their owners,both during the making and ft rwards . h ave endeavoured to treat the subject thoroughly,and although I fear I have not altogether exhausted the possibilities of miniature locomotive construction,it is to be hoped that th e details and e il th e to component parts severally describ d w l enable , reader . design and build any type of locomotive model to any desired onl its scale . The book is the y one of kind,and may also be recommended to the model engineer who does not exclusively go A l in for locomotive work . s model railway engines in the arger sizes may be made to serve commercial ends,several detail ed l s drawings and two designs of engines of this c a s are included .

A M I . M h G. M r . R t I have to thank obins, . for e photograph r M l A I M on page 1 0,and M Percival arshal , . . . E ,the editor of The M odel E ngineer,for permission to use many of th e il lustrations n s I h contai ed herein . Several of the de igns which ave from time to time prepared for various model- making ﬁrms are reproduced, d M M r J notably the mo el idland locomotive and details for ees s W .

k . or h m ton a t Lo w e o N t a L T. R C . B sse t of p the S . design for W E h W N . W M . H t e Co . R t L . . oc . ar in of est am, ; tank l omotive

- ou - n W d . a G. E for Stuart Turner of Shiplake Thames ; the . tank engine and th e engine depicted 011 the frontispiece,built by Flooks Smithies o f Watford,castings of which they respec l tive y supply. I u e M H H r H. r m st also acknowledge my indebt dness to . ar ison,

M D . ow M D r E . L r 0. G s . len, y,and other ,for the help they h ave afforded me in various directions.

HE NRY GRE E NLY .

L D E C ON ON , . .

1 8 07 00 I NTRODUCTORY - N OTE

BY W. J . TE N N AN T,

B U ILDERS of model locomotives are so frequently asked in con versation the prefatory question, Oi what u til ity are your models that a justiﬁcation of th eir value seems to the writer to be a ’ M nl pardonable prelude for r Gree y s book . It may at once be conceded that th e evil -smelling,dribbling,ten -and - sixpenny model of the type familiar to generations of schoolboys is of use only to such extent as it may serve to encourage in its proud possessor a possibly useful sympathy with things mechanical . The real utility of the model begins for th e amateur mechanic when its construction induces him to exercise and improve his craftsman

ul ship and to c tivate an interest in modern locomotive engineering. For th e novice engaged in practical engineering work as an engineer student or as an apprentice,a model manifests its utility h h by making him view locomotive design as a w ole . In t e fore ground oi' his daily life the detail of engineering is so prominent, and therefore bulks so large in the view,as to tend to obscure the broader aspects of engine design with which,among other matters, the beginner sh ould be preparing h imself to deal ; and it is in the production of models,and particul arly in the production of working models,that he may usefully be led to think intelligently upon problems of the kind that his chiefs h ave to solve,and that h e

' himself will h ave to grapple with if in due time th e mantle of responsibility descends upon him . Incidentally,the young pro fessional will probably ﬁnd that model- building will bring him into touch with the n oniprofessional amateur,and if he attains to any considerable degree of familiarity with amateur work he will be likely to receive a salutary stimulus from observation of the N N I TRODUCTORY OTE. surprising quantity and excellence of a large proportion thereof ; this will assuredly be useful to him,and it will be likely to lead both amateur and professional to prope rly appreciate,and maybe to worthily imitate,the work of such men as th e gifted brothers Cbates and other skilful model - makers whose productions are treasured in the unrivalled collections to be found in the southern galleries of th e Victoria and Al bert M useum,the M ecca of the a mateur of engineering. Coming now to the trade,ready- made model locomotives have been greatly cheapened in cost and improved in design and con: struction within th e last few years ; this improvement is largely due,it is suggested,to Th e M odel E ngineer journal and to the Society of M odel E ngineers,with both of wh ich our author has A been honourably connecte d for some time past . great deal of e xceptional experience has been afforded him in this connection as a designer of locomotive models of all sizes,from commercially i valuable engines of 7 cwt. ,downward,and s recorded in the following well- illustrated pages,in which many useful and interest ing evidences of originality,neatness and ingenuity of design and unique completeness of treatment will be found,together with a regard for elegance of externals which is admirable . That the proportions of a successful working model are not obtainable by slavish reduction of the scale of its prototype is made clear in this volume,which lays down very plainly the lines along which success may reasonably be sought,and thereby would seem A to well justify its existence . ttention is particularly directed to i ” Chapter III . ,on The Principles of Locomotive Des gn, and I ” Chapter V . ,on Boiler Design . C ON TEN TS

m p c .

I I TR D TI . N O UC ON I L oco m 'r n I . o rv TY PE S III TH E PRI N CI P E E . L S or L ocou orrvn D SI GN

H E I V . T GEN ERAL CONSIDE RATIONS or B OI L ER DES I GN H V . T E CONSTRUCTI ON or MODEL L ocou orrvns : FRAM ES, B ooms , RADIAL Axnns oxns AN D Tnvcxs,AN D OTHE R DE TAI LS

- V I . WHE E LS ,An ne,CRAN K Axnns,AND a mo ap nmo ARRAN GE ME NTS V I I N . CYLI DERS AND VALVES V V E III . ALV E G ARING I X M TI DE T IL . O ON A S X B OI L ER C TR TI N . ONS UC O XI B OI L ER M ounrmc s AN D T E R FITTI S . O H NG C B T N TEN D E RS B OI L ER FEED I N G D FI R I N G A R R N GE XI I . A S, A KS, , AN A ME NTS

— r x D1 .smxs F OB M N R E L comorrvns Ap p nnm . I IATU o

LI ST OF PLATES

PL ATE PL ATE r rr n n n V I a Detai s an i I ene a a eme t of M otio . d uts e View o f . G l A g ( ) l O d ‘ ’ - for a 1 0 in . au e Tank L oco G . N . R At antic L oco 1 g g . l motive motive . .

- A Desi n f or a -in sc l e M o e (b) Ten wh ee e Trai in B o ie I . a I Q . d l l d l g g ' Tank motive L oco . N ort E astern Railway L oco i e o c A Desi n f or a -in a ar e mot v N . sc e ( . ( ) g g l l g Ten -wh ee e L ocomotive - l d . III . De i ns f r in s e o s o . ca M e s g g l d l . - - V A M o - n i h h ee r n I I e i . sca e a e onia (a) E g t w led F o t coupled . d l i l C l d n Tank L ocomotive Rai wa L ocomotive N o . l y ( . 902 (b) B ogie Single E xpress L oco )

motive. - S . Passen VIII a l in sca e L T . 8: R . ( ) . l . . - n o om ive c A Desi n for a in sca e Mi er Ta k L c ot . ( ) g g . l d g an E x re L o o ’ ss c motive. b A M o e Fair ie E n ine l d p ( ) d l l g .

- - I V A Desi n for a in 0 A Desi n for a 1 5 in . au e . g i . scale ( ) g g g

L 8: N W R Tank E state L ocomotive . . . . . L oco

motive .

I X ro o f L . 81, . C ss Sections

- V . A Desi n for a in s . ca e G N R . . . . d T 8: . an S . g g l G N . R L . R . tl antic L ocomotive N o . M o e s P ates I V . V VI A ( d l ( l , . , . 251 ) and TH E MO DEL LOCO M OTI V E

[TS DESIGN AN D CON STRU CTl ON

C H A E R I P T .

IN TRODUCTION .

[HE AT the miniature locomotive is one of th e most popular

E R A T A R .

5 1 . n i n t . Page 2 U der l l ustratio ,read 3 5 ,no ﬁ

5 Pa e 50 Sixth line f ro bottom read not . g . m , 3 5 , 5

supply the reader not only with fully- worked - out designs for models of various scal es and types,but to in clude more or less standard details of boilers, machinery, and superstructures, together with rules and formulas,all of which have a practical basis,so that without the expenditure of valuable time in trial experiments ultimate success may be assured . Where a beginner is anxious to try h is h and at a working model locomotive,the write r would urge him not to be too ambitious,and, 8 THE MODEL LOCOMOTIVE : I TS DE SI GN AN D CON STRUCTION . in preference to taking a design involving an immense amount o f n work,to attempt quite a simple e gine . If circumstances dictate,and there is a lik elihood of the con struction proceeding without insuperable diffi c ul ties,the reade r may confidently rely on the rules and drawings herein given ; an d where these are carefully adhered to,failure should not occur. M odel engineers approach the construction of a miniature ff n o t locomotive from many di erent points of view . Some care one whit whether the model they are makin g will turn out a practical efiicient steam - engine,the construction to a given scale being the principal pleasure they derive from the task . Others love to see the model careering round a track,and to this end make an engine with the exterior to scale,sometimes, but not always,copyin g some well -known prototype,cutting down ni um and simplifying the working parts to the mi m . There are,of course,a large majority who combine the two objects,and it is in th e model- maker requiring information on the subject of the design of the working model locomotive that the t writer is more especially interes ed . In stating that a successf ul model locomotive is desired there are,of course,measures of success and different results to be aimed at ; however,throughout this work the designs should result in the reader obtain ing engines which shall be capable of running continuousl y with fairly heavy loads. The history of the working model locomotive would be difiicul t N to trace. o doubt,ever since the railway locomotive came to ’ — - stay,models have been built in out - oi the way places ;but whence came the Ajax type of model locomotive or the magnifice nt sl ide valve express engine upon which many youthful hopes have been laid,has yet to be discovered . Amongst the miniature locomotives of note made in the early 1 days of steam transport on land,the model shown in fig. is a very good example . Sometimes scale replicas are made to serve historical and educational purposes,and the number of models in museums 1 H and private collections (all over E urope) 8 very large . owever, this work will not describe the construction of such models,which , it may be mentioned,are generally made by skilled workmen to N N I TRODUCTIO . 1 0 TH E V r DE AN D S T N MODEL LOCOMOTI E : rs S I GN CON RUCTI O . the working drawings of the original and without any great regard to c ost.

THE H I C r S A D G C O E o CALE N AU GE.

The sizes of the locomotives with which it is proposed to deal with in these pages will be to a large degree limited to those built for the amusement of their several owners . Some of the design s

’ Fi 2 — TH E D E or WE S T I TE R L I T L ocomon vn g. . UK M NS S GH .

Gau e 1 5 ih M aximum s eed 20 mil es an h r g , . p , ou . will be of such proportions as to render the ﬁnish ed machines u i t s capable of really seful work for exh bi ion or estate purpose . The Duke of Westmin ster some years ago built a miniature

' railway of 1 ft. 3 in . gauge on his estate at E aton Hall,which n ot only serves to interest th e Visitors to his house,but has proved a commercial success,connecting as it does the residence with the neighbouring main line of railway,and saving a considerable e amount on the previous annual expens of carting.

2- in h e r n The . scale engine illustrated by t f ontispiece is inte ded for exhibition purposes,to pul l two or three dozen school -children

1 2 M V T D D THE MODEL LOCO OTI E : I S E SIGN AN CON S TRUCTION .

at a treat ground,and to some extent take the place of th e

- - time honoured roundabouts,donkey rides,and swings . With no previous experience to guide him,the model locomotive builder is not advised to go in for an elaborate engine of a scale

n in . hi s e u der 1 to the foot. T s and smaller cales are more suitabl A s n hi e for the simplest of designs . model expre s engi e to t s scal will measure some 25 to 3 0 inches long and weigh from 1 8 to

- be 25 . 4 f lbs With a very free wheel base,curves of t. radius may

' f negotiated,but the writer does not advise less than a 5 t. radius .

9 -in 1 g . scale is a very good one to adopt for those with limited ﬁn n iz space and tools . They will d an e gine of this s e present no great difﬁ cul ties in manufacture,and at the same time be small,

- portable,and comparatively efﬁ cient as a working steam engine .

6 f t - - s The minimum radius should be about . Five eighths inch cale R is another excellent scale for small models . eally powerful models capable of pulling a boy of eight or ten years of age may be con structed to this scale ;and if a small four- wheeled engine is built, the minimum radius of curve which may be traversed will work 5 ft n ul out to about . For larger e gines the minimum radius sho d 8 ft be 7 or . ;indeed,it may be said generally that the small types of engines,owing to the shorter wheel- base,will run on curves of 5 7 per cent. of the minimum radius necessary for express engines .

A - in c g . scale renders it possible to model a lo omotive very closely to scale as regards the machinery and at the same time to preserve th e i e working qual ties. It is a rather large scale in some resp cts, but although enough power can be obtained,it is not possible to design a suitable engine behind which one may conveniently is f 1 5 ft. C 1 0 . t . ride . urves should never be less than radius a better ﬁgure,and should lessen the number of derailments,as

- in ta models of g . scale often at in speeds of ten miles an hour, and,having no one on the footplate,may easily get out of control . One - inch scale produces another in between size that is, regarding it as a useful scale for working models ; however,it is one which allows the manufacture of a real ly scal e model, and can be recommended for historical and exhibition engines . 1 1 inch to the foot is the smallest scale givin g an engine which may be ridden upon conveniently ; and its adoption is to be recommended to those who wish to construct a locomotive of the IN TRODUCTION . 4 EL O : rrs DE SI GN AN D N S N 1 THE MOD L COMOTIVE CO TRUCTIO . smallest dimensions and of sufﬁ cient power to carry one person l at least,at a high speed continuous y. One - and - a- half inch scale is suitable for those who wish a little e ﬁfteen a u larger engine . Spe ds of miles n ho r with three passengers t behind such a model may be at ained with ease .

- in is n Two . scale is the smallest size adv able where the engi e is u A n to be really seful and of commercial value . total load of o e ton (including engine) should be within the capabilities of a really

2-in . c well designed and built scale model lo omotive . Stee l

I GH 7 m 1 ”C o ro 20(h .

i — E F . 5 . R L TIVE S I Z ES D W E IG T or M DEL E XPR E S M TI g A AN H S O S L OCO O VE S . boilers may be used,and the cost of s uch an engine sh oul d not be

. 5 excessive . Fig gives a good idea of the differences in th e sizes of model locomotives,and also indicate s th e probable weigh t of

express engines built to the respective scales . Th e next point that requires attention is the question of gauge .

Th e M odel E n ineer The interesting correspondence in g (vol . ix . , 1 903) on this subject shows the diversity of Opinion that exists in settling the gauge of railway for a given scale of model , N N I TRODUCTIO . 1 6 THE M L como'rrvm: rrs S N AN D C ODEL o DE IG ON S TRUCTION . and the difi cul ties of arriving at a definite standard gauge for th e model locomotive are greatly increased by the fact that th e c ircumstances are not invariably alike. ’ Ge orge Stephenson s advice to the south- coun try railway engineers at a time when isolated lines of rail way were unde r construction was to make the gauge the same as in the north, “ saying that they were then a long way apart,but some day wou ld be joined— a prophecy which,as we all know,h as been ful fil l ed to its utmost . This cannot be acted upon for the reason of th e ff varying sizes of models . However,di erences in gauge for give n scales,which some model - makers may imagine tides them ove r otherwise insuperable diffi cul ties,are to be deprecated,and th e writer can only recommend that such alterations be made where a large number of models have been made to a gauge which is no t E s f 8 a scale equivalent of the ngli h standard of 4 t. 5 in . between the rails. Some model loco builders favour a considerably increase d gauge,from the point of view th at the cylinder bore of an inside cylindered model is very much limited if the standard gauge W t x no is adhered to . hilst o a slight e tent this is true,it is t th e greatest obstacle in model locomotive design,and can be surmounted in exactly th e same way as in th e real engine by th e placing the valve chest on top or below cylinders .

n 9 in - The real trouble i small scale (5 and 1 3 . ) inside cylinder model locomotives with l 'ink- motion,is in the matter of the crank S ufﬁcient th e and axle . room has to be found for four webs eccentrics,and,to make a really serviceable job,widening seems

H - in necessary. owever,the writer does not advise link motion such small locomotive models,and therefore this difﬁ cul ty is mitigated .

- I th e firebox difficul t . U s n gin . scale engines is the chief y nles some method of increasing the width of the inner box is adopted, the use of a silent Primus burner is impossible,th e maximum 2 in fir x if distance between frames being about 1 . ; and the ebo , placed in the orthodox manner,cannot be wider than 1 5,th e h 4 o greatest amount of squeezing in of t e No. burner bringing it t 1 n . I th e t 2 i . somewhere abou 1 3 wide such cannot be employed n writer’s opinion a little widening is an advantage,but should not

1 L LO M V : rf s E S I N AN D N S N 8 THE MODE CO OTI E D G CO TRUCTIO .

e quivalent) between,in actual practice . It will be seen th at it is necessary to encroach upon the distance between the tyres wh e re sufficient play be tween flange and rail and thickness of flange are provided,and note should be taken that in al l cases— to a le ss degree in l arger engines— a gauge correctly to scale reacts on th e

- all important distance between tyres. Another way of ﬁxing the gauge would be to start from th e boiler,arranging this to scale,and letting the width between rails

come what it will . The remaining point is (2) That those with limited space for curves wil l not ﬁn d salvation by building models of eXpress engines to small

~in u f as . o scales,such § or Q in” but with the adoption

3 - medium scales ; for instance, 1 6 ,g,and,perhaps,gin . , s e l smaller type of locomotives b ing mode led . With reference to this matter,it often has to be pointed o ut that

-in - or -w n e a g . scale four wheeled ( six heeled e gine,one pair of whe ls being on a pony truck) will be found inﬁnitery better on such

5 f t. 4 G N R . sharp curves as those of to radii than,say,a model . . ’ Atlantic or Caledonian Railway Dun alastair,alth ough with the latter types much can be done in the way of modify ing the prototypes by ﬁt ting small bogie wh eels,pony trucks,and

cutting away the main frames . As previously mentioned,some favour a very wide gauge,but the writer must 2 3 point out that a strict adherence to this 4

u s — W -m mm s or . Fi 7 . policy will give an gly,di proportionate g. t 1 1 1 000 TO n engi e,and although he has seen several 3113 3 good-looking models made on this prin cipl e,the most important features have been so proportioned as

-in o to really alter the scale,and instead of having a g . scale loc

1 - motive built to a 21 or 2§ in . gauge,the model has,in its general

ﬂ - in s h th e dimensions,become a j g . cale engine,and t erefore has correct gauge of this scale— in fact,is more or less of th e standard

proportions. Other modellers take the opposite course,and,ii they h ave l ong since ﬁxed th e gauge and are possessed of valuable rolling stock N N 1 9 I TRODUCTIO .

and other models suited to that gauge,-it woul d be a pity to have to render these latter useless by altering th e gauge when more

p owerful engines are required . — ’ C a f . 6 in c The ape Government standard g uge of 3 t . the So iety s — r n crs gauge of 35 in . being used e d it possible to use locomotives

f -i if his o l n . e t scale . The writ r would,however,recommend hat t ( G R course be adopted, 1 . ail way types of locomotives

should be copied . An increase of scale and gauge does not always in crease the price of a properly made model locomotive in i direct proport on . A refer ence to the catalogues of any good ﬁrm of model locomotive builders will show that the

- ih 1 - wi11 . Je n “: é scale mode cost on the average one-half the price

m m : 2 -in u of a § . ga ge engine,and n ces Of 8 m a — the p k . sc le F i 8 . R E g. E L ATIV SIZ E S or REAL AND . 9 - W RKI M DEL Trans T I N . T 1 1 a O NG O O 2 O model and a 1 3 1 . sc le are TH E FOOT“ 1 to 2 also in the ratio of . Therefore,the author can again advise small types of engines of moderate gauges in stead of tiny eXpress engines,wherever cost must be kept low,and at the same time a powerful locomotive o d btaine . To reduce size,cost,and the radu of the curves of the railway, G W E p rototypes may with advantage be chosen from the famous . . .

- hi fu l b road gauge locomotives . T s not only lﬁ s the abo ve recom ma res n ndation. but the exp s passenger engi e may be modelled

3 -11 1 in an d for a 5 . gauge eng e such a locomotive shoul d be very short and portable. Returning to the recommendation of George Stephenson,seeing that there are several gauges in common use,adherence to those ﬁx already ed may be advised . Th 1 in No 0 e . small gauges are respectively termed 1 ( . gauge), 2 in 2 u 2 i o 1 . N . n . N . 3 a N o. and. 1 2in . ( gauge), ( o ga ge) , 5 ( g uge), 20 M M V : rrs S N AN D N S N THE ODEL LOCO OTI E DE IG CO TRUCTIO .

3 in N 4 d s . ( o. gauge) in mo el locomotive catalogues . The la t

n in . h amed gauge,however,is not 3 ,but between t e rails .

ta u 1 1 ﬂ —ih a e These s ndard gauges are sed for i,3,1 6 ,5,and l g . sc l m odels,respectively . There appears to be a wide difference in th e gauges employe d

- in o s for g . scale model l comotives ; but as far as can be di covered

3 -in - in th e there are several i . gauge g . scale locomotives in possession of the members of the and one or two prominent ﬁrms have also suppl ied engines and ﬁtted up several railways C r a to the same gauge . onside ing,therefore,the diversity th t exists in some quarters,there shoul d be no hesitation in recom

ff i- - ui . mending the amateur who cannot a ord to b ld a i in or 1 in . i m s ce scale locomotive,to lay his ra lway to this di ension . The di tan r 3 in between the ty es should be . ,which only exceeds the scale 1 in n n dimension by about 3 5 . ,and the wide i g is not in any way ﬁnish ed a chicﬂ h n oticeable in the engine . Its advant ges, y in t e matter of burner arrangements and crank - shait dimensions,are many .

- -in 9 sh ou For i in . scale model,31 . gauge (laid or 31 g) 1d be employed,and the writer cannot see his way clear to advise anyon e

A 4 -in m . e to alter that gauge either way. 5 gauge is used by so ,

- in ul . e and wo d appear to be a good gauge for a scale locomotiv . One-inch scale locomotives have in the past been made largely

- 4 in ﬁ ur o 5 in i . e t . gauge ( nstead of § ,the round g for the scale equ ivalent of the standard E ngl ish measurement) ; but this is

N R 8 - f - h t. G. . largely due to the . single w eeler having been the most popular type of this scale,the methods hinted at earlier in this chapter of keeping the boiler to scale and letting the rail s H gauge come what it will,being u ed . owever,the consensus of opinion appears to be that the distance be tween tyres sh ould be — i . 4 in . 4 in . or kept to scale viz , 5 (bare), the gauge being . i (

- - 413 in . laid) .

l - in From what the writer can gather, i . scale locomotive s

r t u 6 in 1 - a . in l are in la ger number buil to ga ges of and 5 . sca e ’ in - M r H to 7i . Two inch scale engines,following . older s (th e Pitmaston M oor Green Railway) practice,are in al l cases o f

deﬁnite to to l O - in which information is hand, built a i . rail d 9 - 111 gauge,the istance between tyres being 3 . The next popular N N 21 I TRODUCTIO .

1 5 in A to u h l gauge is . s the loading ga ge,the aut or wou d always advise the standard British one that is,for models designed on the free lance principl e,which in their main f eatu res f ol l ow the practice l ocomotive engineers of this country ﬁ (see g.

— 9 M X IM M DI G G G E ED BY e rsn R IL . Fig. . A U LOA N AU US A WAYS

l n o o ca e i . t th e ot (S ,is f . ) “ 5 3} H C A P T E R I I .

L ocou o'rmn Y S T PE .

THE model locomotive builder,before he commences the preparatio n of the working drawings for his prospective engine,should acquain t himself with leading features of the now numerous types of loco motives used on our great railways,and even where his mind is

‘ already made up by a particul ar fancy for any given class o f engine,the inh erent advantages and disadvantages of th e chose n design with respect to the rendering in miniature shoul d be care fully considered . The following outline drawings,together with the description o f the possibilities of the several types comprised therein,are intende d to help in this direction . The sketches are to uniform scale o f

1}in . to the foot,and where drawings of actual locomotives are no t given,designs have been made with an eye to the requirement s of the model more especially . Lo comotive types may be cl assified generally under two heads TEN DER E N GIN ES,having a separate carriage for fuel an d water ;and TAN K EN GIN ES,being self-contained locomotives with wate r al l tanks and fuel bunkers on the one frame . Tender ehgines are used for long distance trains,and tank engines for local passenger,goods,and shunting purposes. There are passenger engines,goods engines and shunting engines,but these cl assifications depend largely upon th e size o f F r n the railway company owning them . o i stance,a locomotive ' used solely for shunting operations by a large company woul d b e i employed for passenger work on a very small ra lway or on a. fflm d r coun trygbranch of a railway o o e ate size . 22 L ocomo'n vn S 23 TYPE .

We also have passenger tank engines,goods tanks,both tender passenger and goods engines,and al so engines suitable for either f o . class work. Shunting engines are never provided with a tender The majority of locomotives employed on express passenger trains consist of the type known as four wheels coupled bogie express

Fi 1 — N RT - E TE R R IL N o: 201 5 0. . g. O H AS N A WAY,

Fi 1 1 — L 0N 1) N D T -WE TE IL ID - LI D E R . 0 S U RN R O T E C N g . AN O H S A WAY U S Y L oc mo'rrvn o s.

' h . 2 Ih 1 0 t t e No . 01 5 N h e ngines. g illus rates class on the ort R E astern ailway . The cylinders and frames are inside and th e bogie is at the lead ing end,a six-wheel tender of the usual British standard pattern 33 23 . 5 n . (fig 7 ,p . ) bei g attached A variation of this design is th e outside cylinder engine 1 3 fi . 1 o 59 th L . e N . on e as illustrated by g ,a typ r N 24 THE MODEL Locomorrvn : r s DES IGN AN D CON S TRUCTIO . almost universal in American practice until quite recently ( se e fi 1 2A g. ) The chief objection to both of these kinds as regards their possi bilities in model work is the fact that the firebox is limited by the distance between the coupled wheels; This is not,however,so

detrimental in the case of small

1 - in model locomotives ( . scale and under),which as a rul e employ for ﬁri lated spirit in a wick lamp or petroleum in a vaporising burner,as in larger engines where a deep grate— for — burning solid fuel is essential. The smaller model may be pro vided with a shallow ﬁrebox,and this can then be extended d th e backwar s over trailing axle . Another drawback to both types is that th e bogie wheels are generally of fairly large diameter,and if the model is built to scale

26 M : I TS S N AN D N THE MODEL LOCO OTIVE DE IG CO STRUCTION .

The four - coupled bogie engine was the outcome of an older an d still more E nglish type of engine,th e four- coupled six - whee le d r h l locomotive with the carrying wheels leading. The car ying w e e

’ Fi 1 — Gm r E S TE R N IL RE B ILT 60 CL 5 7 . g. . A RA WAY U ASS in type is often provided with radial axl ebox, and wh e re models are designed with cylinders having valves on top o r below,it is then possible to set in the frames,and by this mean s A to allow a large amount of lateral play to the leading wheel .

Fi 1 6 — L ONDON B R I T D S T C T IL S I L E E XPRE S g. . , GH ON,AN OU H OAS RA WAY NG S m rl vn L oco o . locomotive thus arranged should be quite as free on a sharp curve as most fo ur - coupled bogie engines,and even if a radial axl ebox is n ot employed, a plain axl e box with side play only being

- substituted,th e wheel base should not prove to be very rigid . 4 a d 5 i t t s e 1 n 1 . Figs . respectively llus ra e engine of this typ M 27 LOCO OTIVE TYPES .

Here also a deep firebox is restricted by th e length of the coupling rods,and except where small driving wheels are used as in mixed traffic firebox engines ( fig. an unlimited length of of the ui firin is depth req red for coal g impossible . The next type of locomotive which may be considered is th e once popular class known as the single engine . This type may be divided into those having only six wheels and those with a leading bogie .

ﬁ 1 6 - The engine depicted in g. is a six wheeled single engine h n r Stroudl e wit inside cyli ders and frames,designed by M . y for

B S R . . C. the L . ailway The chief advantage of this type as regards model work is its simplicity,and ,as in all single engines, the ﬁrebox is more or less unlimited in length,the small diameter ' of the trailing carrying wheel oﬂering no obstacle to this procedure — an important consideration where the model is intended to burn

r - solid fuel . Inside cylinde s of over all dimensions not too large in width (similar to the design on page 1 1 5) being employed,the leading wheel may run in a radial axl ebox or in a pony truck,and by this means,together with some side play in the trailing wheel, curves,if not as sharp as possible with other types of engines,of the minimum radii advisable for high speeds,may be traversed by this type of engine with ease . A large amount of the weight can be placed on the drivingwh eels,making the model quite as powerful as some types of coupled engines,with,of course,much less friction t A a of moving par s. gainst the above advant ges,however,the reduction in ﬂue - heatin g surface,water and steam spaces,due to

’ th e limitation in the diameter of th e boiler barrel by the large r vi h as d i ng wheel, to be considered . By supporting the leading end upon a bogie truck th e class of

- h R c t e G . N single wheeled engine re ently brought out on . . is fi obtained ( g. This engine h as the good points of a single e ngine,but,like all leading bogie engines,means must be taken to provide th e maximum swing of bogie by using bogie wheels reduced in scale,narrow cylinders,and cutting away or setting in th e main framing. Similar precautions are necessary with the outside cylinder h bogie single s own in fig. 1 8 ; indeed,the truck in this locomotive, if built exactly to scale,has even less chance to swing than in an 28 THE MODEL LOCOMOTIVE : I TS DES IGN AN D CON S TRUCTION . inside- cylinder design,because of th e crosshead passing so very h close to t e tyre of the rear bogie wheel . A longer firebox is possible with outside cylinder engines o f any design,and,in spite of the limitation of the diameter of th e barrel in a single- wheeled locomotive,a very powerful free- steam

— - E E l . E R E E R B o m S N G E Fi . T T IL ID LI D I L I g 7 GRE A N OR H R N A WAY I NS CY N o NG N .

Fi 1 8 — R E T N RT E R N R IL A O T IDE -CY LIN DE R B oo m S I LE E N I E g. . G A O H A W Y U S NG G N . ing engine should be obtained by modell ing locomotives of this th h . H , e i t e type owever low p ston . speed consequent on use of large driving wheels renders a high steam pressure,cylinders of not too large dimensions,and superheating of steam,advisable, s otherwi e cylinder condensation wil l be excessive . Later developments in locomotive engineering have produced two new classes,the six- coupled bogie express and the Atlantic

ﬁr ﬁ 1 20 st s. 9 types . The is depicted in g and ,and the second

ﬁ s 21 22. in g . and I V T E S LOCOMOT E YP .

In th e outside-cylinder design,because of the reduction in the distance betwee n the rear bogie wheel and ﬁrst coupled wh eel, the connecting rods are attached to the middle axle of the three ,

whe reas th e Caledonian engine is the outcome of simply lengthen ing the ordinary four - coupled bogie express locomotive already b ﬁ s 1 0 descri ed (see g . to With regard to the merits and demerits of the six- coupled N N 3 0 THE MODEL LOCOMOTIVE : rrs DES IGN AN D CO STRUCTIO . express type in model work,if a powerful engine is require d for hauling the owner,it would seem better to adopt a large r scale and gauge and employ a simpler design of locomotive,such as a small tank engine,but there are no doubt . many readers wh o will choose to model six -coupled locomotives for other reason s, a viz. ,a personal fancy for the type or through having a railw y z of small gauge already in use,with rol ling stock of a given si e .

-ﬁred e s For .coal or charcoal models the type presents no advantag as although a long ﬁrebox is possible by extending it over th e axles of the coupled wheels,the necessary depth is not obtainable .

In . the outside cylinder type (with centre wheels as drivers) th e ﬁrebox cannot be any larger than may be arranged in an ordinary

- - ﬁ 1 1 I n outside cylinder four coupled locomotive as shown in g. . engines of small size using a methylated spirit- lamp or an y system of oil burning where two or more burners can be employed

' and a shallow firebox alone is necessary, th e inside - cylinde r ( Caledonian) type is certainly advantageous,especially more in the matter of length of firebox than anything el se,as the sketch 243 on page will demonstrate . The Atlantic type and the E nglish modification embodied

- L . Y R t in the . . ten wheeler may be considered as a developmen of the bogie single - wheeled locomotive,the pair of coupled wh eels between the bogie and th e trailing carrying wheel taking th e a h pl ce of the single pair of drivers . The latter type, bot in real and model practice,combines all the advantages of a single and coupled express engine,giving a long deep ﬁrebox, and by reason of the smaller driving wheels usually employed, h R n L Y . a muc larger diameter of boiler is possible . The . . desig makes a longer boiler barrel necessary (as the front coupled wheels are the drivers),which,together with the lengthening of wheel base,is not an unmixed beneﬁt ; curves of larger radii will be required,and the extra heating surface in th e tubes will as a rule t be of little prac ical value . Before passing on to goods locomotives there is one type of engine,although not in universal use for passenger work,worthy

d - of consi eration by model engine makers. The type is known as ‘ the front- coupled express engine,and was ﬁrst brought into m n n S r udl th pro i e ce some twenty years ago by M r. t o ey, e engineer LOCOM OTIVE TYPE S

B R u t SC . to the L . ailway,on the prod c ion of the very power ﬁ 2 3 . ful Gladstone class depicted in g. By taking this locomotive as the prototype,a short model of

simple character can be designed, and as a large proportion of the weight of the engine may be placed on th e coupled wheels and a long firebox of any depth is easily arranged,the model may be made quite as powerful as one built on the h lines of t e more prete ntious types previously referred to . The 3 2 THE L OOOM OTI VE rf N AN N S T N MODEL : s DES IG D CO TRUC IO . engine has a rather small total wheel -base,and with some side play in th e trailing axl eboxes,curves of moderate radii should be e negotiat d . Locomotives of this type with smaller driving wheels are use d for both goods and passenger services,and for th is reason are e oft n called mixed traffic engin es (fig. The arrangement of the wh eels of mixed traffic engines is in some cases reverse d,the type being simply a modification of th e six- - fi 1 4 i w n wheel four coupled type (see gs. and Th s is sho fi G. E R 420 L r in the . . class (see g. a ger models which require

— FR T - UPLE D E xrm s L ocomorrva L ONDON B R I T N 23 . AN D Fig. ON CO , , GH O S T C S T R IL OU H OA A WAY. solid fuel— adopting this class as the prototype— c an be provided with deep ﬁreboxes without regard to the distance between th e h coupled w eels. By far the greater number of tender goods engine used within the British Isles are of the very symmetrical design shown in

ﬁ 6 - th e i 5 i 2 . t . Six coupled wheels of moderate d ameter of . are g . usually employed,and in general outline and proportions these engin es are much the same as th e two last- mentioned types,the leading wh eel of the four- coupled trailing and the trail ing wheel

- l of the front coupled engines being rep aced by a coupled wheel . The whole weight of the engine is, of course,available for adhesion,but curves upon which models built in accordance with this design are to run must be of about twice the radius necessary

- in other examples of locomotive practice . E ight coupled engine s are now largely employed on E nglish railways for hauling heavy

34 THE I S S N AN D N S N MODEL LOCOMOTIVE : T DE IG CO TRUCTIO . mineral trains, and two well-kn own types are illustrated by ﬁ 26 s. 2 g and 7 . With regard to the possibilities of modellin g such locomotive s the remarks made in considering th e standard six - couple d

o h - go ds engines may be applied in t e case of eight coupled engine s . Th e type provides a long boiler barrel and ﬁrebox,but it is

— > ' - ' Fi . 26A Com oum) oons L oco u or vn D D g . G r ,LON ON AN N onrn c sr unn R IL A WAY.

i — - F . 27 . R E T N RT E R IL E I T PLE D oons L OTIVE g G A O H N RA WAY GH COU G OCOM . doubtful whether any beneﬁts will accrue from th e adoption of an

h t - eig or ten coupled design . Such a large amount of adh esive weigh t is seldom required in model work ; and again,the pro po rtion of maximum tractive force and adhesive weigh t may be m 1 varied from the custo ary to 5 in dealing with the average model.

t u in t Tank locomo ives are a very n merous class . his country V S 35 LOCOMOTI E TYPE . and on the Continent (more so than in America),and,as the name implies,consist of a locomotive with the wate r tank and fuel bunker placed on th e one frame instead of on a separate vehicle . The wheel - base,boiler,and cylinder arrangements are of course much the same as in tender engin es ;indeed large tank engines, except that an extra pair of wheels is added aste rn to increase the bunker capacity,are ofte n built to th e same drawings as traﬂic mixed engines. A 8 s n ﬁ 2 . simple type of passenger tank is show in g. Thi engine— not regarding th e tanks— is a copy,on a much reduced scale ,of the now old - fashioned six - wheeled four - coupled tender

Fi 28 — R E T WE TE R IL SM LL T K E I E g. . G A S N RA WAY A AN NG N .

n Al t th e w in engi e. hough heels are small diameter,without resorting to excessive overhang at the back or the provision of

ﬁr b x t little bunker space,th e e o cannot be of very grea length . The type has, however, excellent points,and is one admirably Th e suited for a beginner to model . leading wheels may be mounted in a pony truck,and sharp curves negotiated . Wh ere th e builder desires a powerful engine with as little trouble as i possible— for instance,a model l ocomotive to pul l one or two

to sa l - in — h pe rs ons, with coal or ch arcoal fuel, , y, i . scale t is design should f ul fil the purpose admirably . The cab is Open,and l th e regulator,etc . ,can be easi y manipulated from a separate truck th s Th e th e upon which e driver ride . same remarks apply to fi 2 b design shown in g. 9,as radial trucks may e used in either type,perhaps,for some scales,more easily in the first- mentioned 3 6 THE MOD T V : I TS S N AN D N S R EL LOCOMO I E DE IG CO T U CTION .

a cl ss of locomotive . The capacity of bunker of a tank locomotiv e may be increased by adding another wheel,which should as a ru le

' fitted a radial axl ebox fi be with ,at the rear end of the engine ( g. fi 28 30. ) as shown in g. s 3 1 3 2 3 Fig . , and 3 comprise designs which are simply modific a

— - Fi . 29 A DE IGN F OR Sl x wn nu nn T K E N GIN E g . S A AN .

- l - tions of te nder four coup ed bogie and six coupled goods engine s . One poin t is worthy of mention with respect to the ten- wheele d bogie tanks,and that is,whereas the four- coupled express 1000

‘ ’ — ~ - ' m D s L n E m r D rn Wnsr m ILW Y ou N m. i . L o1 non N on F g. 30 AN RA A motive generally lacks adhesive weight unless th e rear part is

c h ﬁ heavily loaded by cast footplates,e t . ,when t e type is modi ed b y placing the extra pair of wh eels be h ind the coupled wheel s th e centre of gravity of th e engine generally falls at a point betwe e n th e coupled wheels,and it will be found possible to arrange that V S 3 LOCOMOTI E TYPE . 7 the major part of the weight of th e engine shall rest upon th e th e coupled wheels. Again,the additional weight of engine,due th e c f to tanks,etc . ,will render this type very mu h more power ul th an many express locomotives with tenders,and at th e same time

the model will be very much smaller and more compact . The writer h as found that by judicious selection of springs th e weight can be taken off the carrying Wh eels almost entirely ; of course this is not advisable or necessary,bu t sh ows th e inherent advan t t h h t ages of the ype . Certainly,th e tank engine as t e meri of ‘ N 38 THE MODEL LOCOMOTIVE : 11 s DES IGN AN D CON S TRUCTIO . being a self-contained engine and with a removable roof in th e smaller sizes,th e locomotive,where such is not intended to be ridden upon,will be quite as easy to manipul ate as any express engine . For sh unting purposes and sh ort journeys,goods and passenger

— - Fi 3 3 L N D N D N ORTn Wnsr rnN IL oons T N E I N E . g. . O O AN RA WAY G A K NG tank engines with four or six - coupled wheels only are often used, h ﬁ 5 ﬁr bo x h s. 34 3 e as s own in g and . In both types lengt and bunker space are l imited,although th is may in a large

— A D E I F OR FOU R - W H EEL S N TIN T N K E N I i 34 . E F . g S GN A HU G A G N . degree be overcome in the four - wheeled engine by modiﬁcation s sh own in th e simple design for a model 011 page 253 . Th e fo ur wheeled tank locomotive is much th e best type to adopt wh ere very sharp curves are a necessity . There are oth er types of tank e ngines, notably th e G E R: LOCOMOTIVE TYPES . 3 9

- N R . h 1 1 D G. co N o 6 ecapod and the . eig t upled . ,but these do n o t ese t to - pr n any advantages the model maker . Some tank e ngin es h ave the water tank on top of the boiler instead of at ’ th e d are s - n si e,and then known as addle tank engi es .

— E IL I N E I E Fi 35 RE T S TE R S T T . g. . G A A N RA WAY HUN NG A K NG N

Concluding this chapter on locomotive types,special reference must be made to one spe cies,largely employed in this coun try, which embodies many features of more than passing interest to

— T P LIT IL TR AILI B oom P S EN GER T N Fi 3 6 . M E R g. O O AN RA WAY NG A S A K

L OCOMOTIVE .

- - At d Th e t v t h . th e mo el maker . ype gi es a shor coupled w eel base th e cylin ders th e maximum width of frames is available ; th e ﬁre bo x,in length and width,and th e bunker spaces,may be of th e largest dimensions,and also the weigh t on th e coupled wh eel s D N 40 THE MODEL LOCOMOTIVE : rf s DESIGN AN CON S TRUCTIO . sh ould be considerabl y more than hal f the to tal weight of the engine . Such an engine will be found to work out much shorter in over - all dimensions th an a ten- wheeled tank locomotive,and will

- t be less costly. The rigid wheel base in h is type of locomotive,an

ﬁ 6 . . 3 example of .which is shown in g ,is never very great

Fi 3 7 — L N S H I RE AN D Y S I E I - L E g. A CA ORK H R RA L WAY TE N WHE E R , FR N T V mw O .

42 V : rrs S N AN D N S N THE MODEL LOCOMOTI E DE IG CO TRUCTIO .

—in l a practical case for a {z . scale railway as an examp e,we may formulate as follows Th e load to be pulled is to tractive force

as 20 is to 1 . h 1 Therefore if engine weig s 40 b. ,and a train of ten coaches of 1 0 1b 18 . each is to be drawn,the sum

40 1b 1 00 1b. T F . + is to . .

as 20 is to 1 . 1 T. E is Therefore as . . 125 of load to be pulled, = 0 1b The tractive force required 1 .

— A S E T I TH E E I N M D L I Fi 3 8 . R T E or E g. K CH SHOW NG HOW S S A C A O TRA N B E M E S R E D MAY A U .

The formul a universally used for ﬁnding the theoretical tractive force of a locomotive is D 2 x L x P Tract1ve force D W Wh D C ere ylinder bore in inches . DW D t h iame er of driving wheel in inc e s .

L Length of stroke in inch es. P u ih . s . Steam press re in lbs . per q

This may look formidabl e,but simpliﬁed,it is l D . Tractive force ia. of cylinder x dia of cylinder x ength of stroke x steam pressure the diameter of driving wheel, all or l dimensions being taken in inches ( ike terms) . 1 In the case in point the tractive force equals 1 0 b . ; an engine d S t with a cylin er gx kin . driving wheels,and an average s eam l th e ufﬁ ce h pressure oi,say,3 0 b . in cylinder should s ,as t e follow ing will prove : 7

F . T. 1 0 . nearly lbs 3)

It will be seen upon a few examples being worked out that an THE I N S OF M S N 43 PR CIPLE MODEL LOCO OTIVE DE IG . increase in the diameter of the driving wheel will diminish,and any increase in cylinder diameter,length of stroke or ste am pressure,will augment the tractive force. If only one double-acting cylinder is employed,the result of the working will have to be halved,the same procedure applying if

- ed two single acting cylinders are us . The tractive force of compound l ocomotives is best calcul ated by arriving at the mean pressures in the cylinders with imaginary a o indic t r diagrams. D 2 x L x P B the use y of the D W formula,not only can the values o f various cylinders and driving wheel dimensions be compared, but th e proper ratio of th e tractive force to weight on th e driving w e h el may be determined . In real locomotive practice the maximum tractive force exerted is generally arranged to bear a proportion of 1 to 4 or 5 of the weight avail able for adhesion,that is ,weight on driving,and coupled wheels,if any. In small work the author has found that slipping wil l not occur on the average model rail if the tractive force does not exceed one -third o f the adhesive weight,and as a guide,the designer is referred to C I h h t hapter . ,in w ic the average weigh s of model locomotives are given,the probable adhesive weigh ts being estimated by references th e l th e to the loads on severa wheels in prototype . Th e total weights of engine and tenders are given,and a ded uc tion of about half to one - third must be made from th e ﬁgures given,to get an idea of the weight of the locomotive itself . Th eoretical considerations such as the foregoing may be thought unnecessary,but as so many disappointments have occurred th rough absolute reliance upon dimensions which have been as nearly as possible simply scaled from working drawings of prototypes,it appears advisable to urge model engineers to go to the root of the matte r and to design their models with a strict eye to the mechanical laws involved,which remain the same whatever may be h e of h h h th t size the mac ine in w ic ey are concerned. I t is not the best course to ﬁx th e size of the cylinders without consideration of all th e points,otherwise the result may be that th e cylinders are so small that a very high pressure is required (although this is a lesser evil,and is not a common occurrence), 44 D : rf s S N N S N THE MO EL LOCOMOTIVE DE IG AND CO TRUCTIO . or so large that they unduly drain the boiler and that th e latte r n th will o ly upkeep a comparatively low pressure of steam . In e former case a very strong boiler wil l be necessary ; in the latter absolute failure may result by reason of the excessive cylinder condensation which follows the employment of a low pressure,and therefore a low te mperature,steam . A good rule is to make th e dim mion of th e scale of the model the bore of the cylind er,the stroke being a scale reduction of that of 1 - h r . in th t e p ototype In Q . scale,engines will,under is rul e,work

1 i 2- 2 n 4 . out at i x . ,and in inch scale at x M odifications sh ould only be made in special cases,and in th e be A — in . smaller locomotives the sizes should not exceeded. g scale engine having a boiler of sufficient power may be provided with cylinders up to g in or larger if the adhesive weight will t allow . Generally,in the event of superhea ing not being possible, v s L such liberties with the rule are inad i able . ocomotives with big driving wheels may have greater cylinder capacity, th e increase being mainly obtained by the use of the maximum piston s troke . When the subject of steam pressure is being considered it must be noted that although th e steam pressure at which a model is to work is often arbitrarily predetermined,th e steam pressure main tained will depend upon many things— c ylinder sizes,speed, evaporative power of boiler, amount of cylinder condensation, h firing arrangements,fuel,and t e completeness of the combustion . R l o h t eference to sca e pressures is the wr ng met od . For ins ance , the scale pressure of a f in . scale model locomotive would be 1 1 50= 6 1b — a t u t u t . abou 9 ; of about qui e nsui able press re for a practical working steam locomotive. By reason of th e exposed positions of th e cylinders of a small model l ocomotive the minimu m pressure would seem to be abo ut 0 25 l b 2 to . The table on the following page gives suitable pressures for models of various scales . The chief value of th e higher pressu res is the fact t hat the consequent increase in the temperature renders th e engine le ss wasteful,decreasing th e loss by initial condensation,and for th is very reason model engines wh ich have their cylinders reduce d

1 o m d rn l o omotives ran from 24 ih 2 iston stro es f o e c e . to 6 ih The p k g . THE . S OF V S PRIN CIPLE MODEL LOCOMOTI E DE IGN . and the nominal tractive force correspondingl y decreased are in p ractice really rendered more powerful because of the h igher steam pressure maintained by the boiler and the reduction in the losses through initial condensation and priming,both of which contribute to the amount of work obtained from the engine per u nit quantity of steam consumed . Too h igh a steam pressure,besides requiring the use of a very strong boiler,presents no equal advantages,as it will be found after a certain point,that the losses by leakage and radiation (owing to the greater difference in the external and internal efﬁ cienc temperatures) nullif y further y.

T B r B S E SS A LE o SUITA LE T AM PRE URE .

— I nch l bs Tem eratu re of Steam Fah r. . . p 3 20 to 25 259° to 267 ° 5 25 to 35 267 ° to 280° ° ° g 30 to 40 274 to 287 30 to 50 274° to 298° 1 40 to 70 287 ° to 3 1 6° 1 5 60 to 80 307 ° to 3 24° 2 1 00 33 8°

It nee ds no special mention that a model steam engine is very w aste ful as a heat engin e ;indeed the smaller the engine becomes in ﬁici nt th e more e e it is. This is in a large measure due to the following circumstances . Geometrically the cubical capacity of a solid does not vary in direct proportion to its external surface,and from this it will be seen that the cooling surfaces of a steam cylinder will be greater proportion to the capacity contained therein in a model than in a large engine . To emphasise this fact,and to show the cause of the excessive cylinder condensation ever present in miniature steam locomotives, the writer some time ago prepared th e accompanying diagram . ﬁ di t a in ( g. The agram shows hat where s the large engine the proportion of heat in a cylinder full of steam is to the radiating surfaces of the cyl inder about 1 to 1 ° 1 ,in a small engine the propor tions are entirely different,one unit of heat having about 85 square 46 THE I TS S N AN D N MODEL LOCOMOTIVE : DE IG CO STRUCTION .

it Th inches of cooling surface to dissipate . e point is to a large degree proved in practice,by the fact that the cylin ders of large

- A it petrol engines are not air cooled . bove a certain size is impossible to provide sufﬁcient cooling surface,the heat in the cylinders growing in much greate r proportion to the increase of th e radiating surface as th e power and size of the engine is aug men ted h th e t h . T erefore was e of heat (w ich is required in petrol engines) does n ot increase directly with the power of the engine t a wi h given cooling rrangements.

R e a; M O25;

' c r m 1 !" ' l ? zz 1 a 6 5 6: ar m ” . 1l 3 5 Id: arms czl ﬁ em s

Cu b m:

Fi 39 — DI RAM sn owmo C E or E xces g. . AG AUS s1 v11 CY LIND E R CONDE NS ATI ON I N MODEL, I P R I wrrn L RGER E I E S N COM A SON A NG N .

B k ortions sh ow h eat at 25 l b team ( l ac p . s p ressu re in real engines this works out to aboitt 495

fi l th In the above diagram ( g. 3 9) lower rectang es repre sent e amount of steam in cubic inches,and the black portions th e units of heat,whilst th e upper shaded squares indicate th e number of square inches of cooling surface,all th e figures being plotted to scale and resol ved to a common size . Cylinder condensation to a greater or lesser exten t being inevitable,th e question then is : What can be don e to increase the efficiency of th e model by the mitigation of this fault ? I n th e following paragraph s th e various methods which can be adopted to prevent or reduce cylinder condensation may be cited ( 1 ) Increasing th e pressure of the steam above the scale h w s s t pressure . (T is ill of cour e neces i ate the reduction N S or MO S N . 47 THE . PRI CIPLE DEL LOCOMOTIVE DE IG

of the cylinder bore,or else the boiler will prove in fﬁ i n su c e t ; also the slipping of wheels will be probable . ) 2 th e v n ( ) Superheating steam . Superheating is gi i g the steam a higher temperature than that of th e corresponding

pressure ; see table on page 45 . (A lower pressure can be used if th e superheating is carried to a considerable

extent. ) (3 ) Lagging all parts which contain steam with non - conducting

material . 4 h e his b ( ) Increasing t e piston spe d . T can be attained y using a small drivin g wheel and employing a cylinder with a

moderately long stroke . The increased speed gives less to time for the condensation take place . Oi course the above remedies are more effectual if used in c o difﬁ ul njunction with each other . It is very c t to lay down h ard and fast rules,but in any case a judicious choice and careful h th p roportioning of t e preventatives will give e best results .

- To revert to th e subject of suitable steam pressures : a gin . o r - u gin . scale boiler is not sually provided with lagging,and th erefore with models of this size a very high pressure cannot

' b e employed so economically,because of th e greater diﬂerences in the temperature of the steam in th e boiler and th e atmos h ere A p , as already mentioned. noticeable reduction in the q uantity of water evaporated by the boiler will be experienced o u t u l of doors even on a day which wo ld not be ca led a cold one . Th e loss by radiation would be proportionate to the difference in temperat ure of th e boiler and th at of th e air,and therefore if a h igh pressure steam with its corresponding high temperature be used,it will be seen that the loss due to the bareness of th e boil er barrel will be greater . The writer has not up to the present been able to record any

- n case (excepting in 1 } and 2 i . scale model locomotives) where the expansion of steam in the cylinder by means of increasing the lap of th e slide valve,linking- up,or compounding in small ste am engines of any type,has resulted in any appreciable saving in ste am,bu t this may be th e fault of those responsible for th e expe riments n ot constr ucting th e apparatus in a proper mech ani cal manner or th oroughly understanding the nature of th e ﬂuid 48 L comon va : rrs S N o nsra o'rl n THE MODEL o DE IG AND o u o .

they were dealing with . It must be urged,however,that the compound or oth er model locomotive provided with means of expanding the steam will not be a success unless it is worked scientiﬁc n out in a man er . It would appear that although a certain percentage of gain can be obtained by expanding the steam on more than one cylinder,this increased ou tput per unit of steam consumed by th e engine is more than counte rbalanced by th e power required by the extra parts of ff t the machine . If real saving is to be e ected,it seems hat the most simple way to do it is by the use of a simple engin e ﬁtte d with some semi- automatic device which will link up the valve gear and

can be operated after the engine has started . With reference to this there however appears to be a limit to the expansion if ordinary saturated steam is used,and it has been found that the initial con densation is increased to an alarming extent when the cut-o ff

n ﬁv - - is earlier tha e eighths to three quarters of the stroke . To prevent this rendering any saving in steam null and void,some h met od of preventing liquefaction in the cylinder must be adopted . The only effectual cure is in the provision of a superheate d — i. e supply . the use of steam of higher temperature than that of

' i - saturation . The gain in a s mple engine arranged with a cut oﬁ 1 at half stroke, or in a well- designed compoun d model,should t t 20 5 theoretically amoun to abou to 2 per cent. In the latter instance the extra gear (where three or four cylinders are employed) would,the writer thinks,reduce this saving to nothing,and except for many oth er advantages of compounding (wh ich,by th e way,are not marked in model locomotive practice) t no beneﬁ will accrue . In th e former case th e question is,Is it worth the trouble in 2 tiny locomotives ? and it is left an open one for th e ingenious

reader to solve. However,one or two general hints may be

given on this intensely interesting point . A two—cylinder compound would appear to offer th e best chance

' 1 Th e cut- oﬁ must be quite th re e - quarte r stroke in ful l gear,el se th e engine

t al wa s start Th e earl ier cu t- off sh oul d be obtained b l in in - u onl wil l no y . y k g p y, rovision of a considerabl e amount of l a in th e ﬁ rst case not by th e p p . 2 Ou engines upon which th e owner may ride,l in king-up is a sine qua non, eas to do th is com oundin is not worth th e x r r bl and as it is so y , p g e t a t ou e .

H A P E R V C T I .

T C N R N r BOI I J R S HE GENERAL O SIDE ATIO o E DE IGN .

TH E chief diffi cul ties of model locomotive making usually arise in connec tion with the provision of a boiler of sufficien t power to drive th e engine continuously,and therefore in this chapter th e writer will deal with the question of boiler design exclusively, giving rules for fixing the amount of heating surface required for various dimensions of cylinders and other conditions .

A u e t be th e ltho gh great lib r ies may taken with . regard to internal arrangements of a model locomotive boil er where the orthodox type is retained, the same care m ust be taken in providing proper means to ensure the maximum evaporation of z t th e water,vi . ,in smokebox arrangements,grate area,perfec i n th e combustion of the fuel,and steam t ght ess,as in real engine . Again,the dimensions of th e boiler of a railway engine being bounded by certain limits of height, length, and width, th e “ designer of the model will be handicappe d in the same way as the locomotive superintendents of this country are,more especially in

this decade . The limits of h eight and width are called the loading gauge , 1 the dimensions of the E nglish standard be ing included in th e ' - a h an ﬁ . 9 C I A n . d i scale diagr m, g , apter . In merica on the Continent,whilst th e rail gauge for the main lines is the same,th e allowed height and width o f th e vehicles are very much greate r,

t ﬁr - 1 5 the maximum heigh in the st named country being about f t . — th t . 6 ih . and e over all wid h about 1 0 ft It would appear at ﬁrst sigh t that th e l oading gauge does not

1 E ngl ish rail way companies l oading gauges Gary sl igh tl y ; th e l arge st di nsions of al l are embodie in th e ia ram me d d g . 50 B S N OILER DE IG . 51

affect the boil er materially (except as regards height),but in fact it so th actually does . The diameter of e boiler can be considerably increased in size,and the width of the ﬁrebox very much augmented, where the distance between rail level and boiler centre is un e restricte d . For this r ason it is best to consider this matter at th e outset by making a cross- section of the proposed model through any point where it is possible for th e machinery

fir box or frames to foul the boiler or e . At th e driving Wheels it will be found that m fi 41 th e dia eter of the barre1 (b, g. ) is limited by the distance between th e tyres of the Wheels ( a) and the heigh t of boiler centre from the rails (h ),and of course the firebox cannot be any wider than th e rail gauge will allow unless th e foundation ring rests on the main f rames (see

l r v Plate IX . ) or is p aced behind the d i ing wheels

Fi . 41 w th i g . as sho n in e design descr bed by Plate III . , or over the wh eels,as can be arranged in a small - wheeled type of locomotive . The ideal requirements of a model boiler are as follows It sh ould provide a good circulation for the water,compl ete ventilation of the ﬁre ;sh ould be of the proper strength, have ample heating s urface for its size,a large range of sufﬁcient water,and capacity for a good reserve of steam . Th e grate areashould not in any case be smal l,and the m m I s okebox arrange ents should be perfect. t should be

designed with due regard to the fuel to be employed . The proportions of a model boiler depend upon one another, and the designer should beware of the common pitfall of providing plenty of heating surface but curtail ing the water and steam spaces n d s to a degree borderi g upon absur ity. Ca es might be cited where the boiler h as fairly large surfaces combined with an extremely small firebox ; others,whilst having plenty of room for burners or fire,have so little tube area th at half th e heat evolved is wasted up the fu nnel . fi 42— A very common mistake is depicted in g. one which t u the writer is constantly correc ing in designs s bmitted to h im. Instead of keeping the crown as nearly as practicable down to th e 52 O I V : rf s S N AN D N S N THE M DEL LOCOMOT E DE IG CO TRUCTIO . level of the top of the flue tubes,it is shown,as indicated,some distance higher than it need be ;and instead of the range of water

- i in s o n. in a g . cale l comotive being,say,g or ,it is reduced to in h i . ,which means that the time during whic the locomotive can is t mi be run without replenishing abou a third of what it ght . A tabl e is here included by th e help of which,with out calculation, desirable proportions of h eating surface,grate area, ste am and wate r space (measured from crown of ﬁrebox to roof of barrel) for l Th ﬁ given scales and cy inder dimensions may be obtained . e gures ff may of course vary slightly under di erent conditions. A very good rule for settling th e heating surface of a model locomotive is to mul tiply the cubic capacity of both cylinders by 7 0 in large engines and 1 20 in small engines,the result equalling

' W f r ?e wa l q h o s c a e a I 15 ’ W r f Ao n ae o/ a ﬂ 73 m o gen

r meth o meth o Th e co rect . Th e wrong d . d

2 — I E X D E S I Fi . 4 F R B . g . O GN

f h s n . the required heati g sur ace in square inches T is rule,of cour e . may be u sed in th e Opposite w ay,and the cylinde r diameter an d stroke determined from th e heating surface of a give n design o f l boi er . If superh eating is to be adopted,th is rule may be used with some degree of latitude,and a la rger cyl inder capacity than it provides

m l - en i s h u not d d th employed . S a l wheeled g ne s o ld be provi e wi cylinders so large as to cause th e wheels to slip owing to excess o f tractive force at starting,n ei th er will it be wise to make th e cylinders of such a diameter even if th e procedure is warrante d h n a by a consideration of th e eati g surf ce alone . Another good guide which works admirably in practice,especi al l wh ere the cylinders are ﬁxed by th e rul e given on page 44,is y “ Heating surface : 300x scal e x scale ) which in th e case of an

r s l s uare O ca e q d . B N OILER DES IG . 53

u 1 in as engine b ilt to a scale of 5 . to the foot,works out follows H S . . 3 00x 1 5 x 1 5 = 6 5 H . S ih . . s 7 q .

There are,of course,cases where a variation from this rule will

- not be attended with failure ;for instance,a gin . scale locomotive

- t 90 s in with a water tube boiler (see Pla e III . ) need only have q. . and yet be perfectly successful ,whereas the last - mentioned rule 1 2 h 0 in . woul d dictate a eating surface of sq.

= l n 0 n a . i R S . 0 20 s 3 e r y 1 q .

This success is due to these small boilers being suited to the kind of ﬁring (me thy1ated spirit wick lamp) usually employed in conn ection with them .

B 10 R N S TA LE 0 BOILE PROPORTIO .

S ca e 1 I in . 1 1 in . 2 in l , } i } .

L oco typ e

B oiler diameter, 22 35 61 7}1 1 0}1

w md “em 1 2 1 5 1 3 22 31 41 ggﬁzesj

- - - Tubes,diameters, - t H : { r ﬁ 8 1 8 2 2 1

— — — — — numbers, 8 5 1 2- 7 1 3 7 1 6- 9 1 6 1 1 24 1 8 30 20

H eating surface , 1 20 700

Cylinders, 5 x 1 3 x 1 1 {43 x 1 5 l i x 2 1 3 x 2}1 1 § x 3 2i x 4

Water -tube typ e

ﬁ x l 3 x 1 2} i x l g 1 x 2 l i x 2}a l 5 x 3

3 1 61

I nner sh ell, 2}1 45

Water tubes, dia 4 3 meter,

H eating surface, 4 THE I S D N 5 MODEL LOCOMOTIVE : TS DE IGN AN CON STRUCTIO .

i 2- in s Again,it is easy to provide a large model o ,say, . cale 2 h 5 er . 3 er c with p cent or 3 p cent . more heating surfa e t an the rule gives (this should be done) ; and,at the same time,difﬁ cul t to

ffi h a c -in l a in obtain su cient e ting surfa e for a Q . sca e model, ccord g to result the rule would advise ; nevertheless readers can be

recommended to keep on the right side of the rules just given. If this is done the builder will know that it is not in sufficient heating surface that is the cause of his model failing — supposing h u that unfortunate circumstance s o ld arise . Simple boilers for engines more or less of th e toy variety may be made by obtaining a piece of light brass tube and fitting it with ends in a strong manner ;and except it be that some two or three ’ small in - and- out wate r tubes are fitted,this type of boiler will fi x fi require no rebo , nes or smokebox . The flame of the spirit lamp u sually employed with such genera tors burns in the open air,not depending on draught,and very

w - in sca1e s fuer much better often ill,for Q . and smaller model ,do y than the same lamp placed in a nominally more powerful boiler fi b x fi m x h having the orthodox re o , ues and s okebo . T is is solely ' ’ because the flame of a spirit lamp is better ventilated,and com n I bustio is more complete . t burns in the open air,and requires th e c m firebox no induced draught. In ne essarily s all of a loco n fl motive type boiler of Q i . or smaller scales the ame is generally ’ choked, and as the heat given out from a methylate d spirit ’ lamp is local,the method of outside firing is in tiny engines

very successful . Th e next step in small engines is to box in the flame of th e m fine fi 43 b la p by providing a and a smokebox as shown in g. ( ) .

' This is a simple way to get over th e obvious objection of the out side - ﬁred model locomotives,but attention must be immediately u paid to th e question of dra ght. This is not,of course,an ideal arrangement,as the heating surface is small and radiation surfaces are large ; but where the cylinder capacity is reduced (as in single - cylindered engines),success is no t at diﬁicul t tte — d all a ma r indee ,it can be assured . Thanks are due to the perseverance and ingenuity of a well — F — a M r. t t known model m ker . Smi hies of Wa ford,to wit for a s very great improvement in thi class of boiler . The invention has '

BOI L E R DE S I GN . 55

’ received the writer s close attention for some time past,and by scientiﬁc arrangement and slight alteration in general construction, the author can,under certain conditions,recommend it for models

- 1 in . as large as 1 . scale ’

M r. ﬁ 43 Smithies improvement of the type shown in g. consists of providing a shell,to all intents a copy,externally,of the loco

— Fi 43 . S I L IL E n M DEL L c u rxvss MP E B R ro o o o . g. O S O motive boiler,with the plain cylindrical boiler proper and its wate r tubes inside,as shown in the cross—sections of the drawing, ﬁ 4 g. 4 . It would at ﬁrst sight appear that the arrangement is a bad one for various reasons,amongst which may be urged that the shell

S ecti S ection at A A. on at B B .

’ 44 — S E WATE B - E B E i . IT I T D L TIV IL F g. M H S UB E M O E L OCOMO O R. will absorb a greater part of the heat and th e boil er itself get little, t and also that a large hea ing surface is impossible . These difﬁcul ties,however,are neither encountered in practice t t nor are so formidable as hey look . Th e shell ge s fairly warm in small engines,but not so h ot as one would imagine,the painting,

- t if done in a dark colored enamel,standing very well . The wa er tubes,which are directly over th e flame of the lamp,absorb a large proportion of th e heat,and the total heating surface if it is smaller th an that obtainable in a fire- tube generator,is of a much more 6 M : rrs E S N N S N 5 THE MODEL LOCO OTIVE D IG AND CO TRUCTIO . effi cient character,and is in the most suitable place,especially as

- regards liquid fuel and spirit burning engines. The barrel of the boiler proper is not subj ect to l osses by radia tion, being slung in the heated gases,and as the ﬁnes are of l arge cross sectional area (compared with a ﬁre- tube engine),and the resistance to heated gases very small,the h ame is well ventilated and drau ght very free under natural conditions,particularly during steam n raising if the smokebox door is left Ope . ’ The write r s experience,however,recommends that the follow ing precautions should be taken in designing boilers on this principle 5 3 The water tubes should not be too small or too large ; 1 6 to 1 6

in z . . outside diameter are the best si es for small locomotives Water tubes should have a good rise;and should,where one row only is ﬁtted,all but touch the throat plate and ﬁ 44 barrel joint as illustrated at a: in g. ,and in the

- A A. cross section on . ﬁrebox ul n l be The sho d be as lo g as possib e . The tubes may slightly bent with advantage,and should also be hard soldered in place in small engines,at least at the front

joints . Downcomers of ample cross- sectional area shoul d feed th e t tubes at he lower ends . The diameter of th e inner barrel should bear a proportion o f 3 4 3 to or to to the outer shell. The lamp in small engines should be as low down as

possible . I n large boilers the outer shell will need to be in two th icknesses with non - conducting material between,and th e tubes will require a different mode of ﬁxing (see Chapter Solid fuel is not suitable for this type of ﬁerce th e boiler,owing to local heat at the sides of box . These boilers provide a sp l endid circul ation,and also have a very l arge range of water level,both of these advantages contributing h u u r greatly to t eir s ccessful career and pop la ity. To return to th e ordinary locomotive boiler,a few hints are worth mentioning with regard to the design of this type of generator in miniature

M N 58 THE MODEL LOCO OTIVE : I TS DE S IGN AND CON STRUCTIO . treated,or at least prevented from leakage even when th e wate r w h happens to be allo ed to become lower t an advisable. Boil ers intended to be fired with solid fuel (coal or charcoal) should have deep grates ; this wil l generally nee d th e pro fir box t t vision of a separate e shell plate . Otherwise h e founda ion ring need never be lower than th e footplate level, and may be placed on top of the frames,when an increase in the width of firebox will be general ly possible, as shown in the cross R W . L N . te . section of . design on Pla IX It is essential to success that th e steam sent to the cylinders should be as dry as possible,and to this end the steam should be collected by perforate d collecting pipes or from domes provided with either perforated or other baffles,the area of the holes in ’ 1 th e collectors being such as will slightly wire draw the steam, s it and in thi way superheat also . One of the most important considerations in model locomotive boiler design and working is the provision of an efficien t yet

N atural drau ht is en tirel simple method of inducing a draught. g y imufi cien t to promote th e necessary combustion— for one reason, that locomotive chimneys are comparatively very short— and the use of exhaust steam in the chimney by way of a blast pipe,which marked th e greatest step in th e early progress of the actual locomotive,cannot be disregarded in a model boiler with an e fire fiues enclos d and small . Th e best care is recommended in the matter of smokebox arrangements,and as a general rule, experiment is necessary to determine th e most efficien t proportions of exh aust nozzle (or orifice blast ,to use an alternative term) and chimney . During the last two years th e auth or has paid particul ar attention to this branch of model locomotive design,and the following proportions, deduced from practical and successful examples,should enable anyone to settle u pon th e most suitable proportions for any given scale of model . As th e area of th e blast pipe plays an important part in the question,th e following rules will be found useful

d h : For engines with cylin ers of less t an 2in . bore Area of blast ﬁ = h i . or ce 3%t area of cylinder

1 ’ ’ Wire - r win is th e te rm used for th rottl in th e steam d a g g . 59 B OILER DES IGN .

1 2- in : A i e = th For large engines up to . scale rea of blast p p 9 6

area of cylinder . 1 F r h m h . o t e edium sizes,9 5 t is a good proportion Practical examples are as follows

S cal e C l inde r Oriﬁ ce . . y .

‘ 2- 2- 1 in in . d . 1 6 iam . 1 1 ' 7 i 15 3 4

8 n hi 1 3 Q 3 5 bare .

For smokebox and chimney arrangements,th e accompanying sketc h shows propor tions for real l ocomotives put forward by V o n B orries,the great authority on compound locomotives,and also two examples from models built to my designs.

- 45 2 in . Fig. (a) represents the blast pipe and chimney of a ’ scale model,(b) Von Borries rule,and (c) th e arrangement in ’ r E as a ro h M . t b ok s tank locomotive,and t e drawings are resolved

to in t. t . i t t a common scale,3 . to the foo I w ll be no iced hat the smaller the model becomes,the lower down it is necessary to place th e blast pipe,and that th e best proportion between th e diamete r of the chimney and the height from nozzle to the top of th e ’ chimney,in the real engine would appear,by Herr V on Borries 1 4 diagram,to be as is to 3,see ﬁg. 5 (b) ;in model,success h as been i o 5 obtained by a proport on of about 1 t . If the height is limited, then th e chimney should have a smaller inside diameter . This is o ne the th e A ﬁ 45 of the reasons for use of liner in example at , g. .

' Whilst these diagrams sh ow th at th e linear dimensions of s uccessful arrangements are different to those a scale reduction of a given prototype would prescribe,it must be understood that these variations do not prove that the principles are in any way altered by a reduction to scal e,but they make very clear th at scale reductions,strictly adhered to,are delusive and fraugh t with danger

c th e h h m t to the suc ess of model to w ic such e hods are applied . With regard to the importance of th e position of th e blast pipe,th e writer cannot do better than here recite th e conclu sions consequ ent

ﬁrst th - in e on one of his experiments in is direction with a g . scal

Th is size th ri r f o d e w te un too smal l . 60 MODE L V : 11 s S I N A D ON S N THE LOCOMOTI E DE G N C TRUCTIO .

model oil—ﬁred tank locomotive,which was reported in the pages of Th e M odel E n ineer J 1 st 1 902 g of une , . The engine in question is that shown on page 268,and whether it was worked at 500 or 1 00 revolutions,th e production of steam was a directly varying quantity and automatic,as in a real loco h h h motive,by the ejector action of t e ex aust steam in t e chimney .

’ The boiler,in spite of its ampl e heating surface,was not made to

_D . f i n! b ( ) o 33 m L

Fi 45 — C IM E AN D BL T PIPE Paoron'rxos s 6 g. . H N Y AS n ( ) I N E L AN D M DEL L ocomor' rvs s R A O . steam until some ﬁnal adju stments had been made,th e burne r not giving out its fullest heat until the proper height of blast pipe (see A l 46 was . ﬁg. ) found experimentally ny fue requires oxygen to compl etely burn it,and as a locomotive boiler requires forced draught almost more than any other type to enable it to perform the work required of it,the source of th e draught must be attended

t o t t o f to. In the real locomotive the propor i ns and rela ive posi ions the blast pipe and th e chimney are important factors,and so with

r models,more especially those using oil burne s and solid fuels . If the working of an oil burner be watched,it will be seen (the steam blower being shut off during th e experiment) that it will smoke when the engine is stopped,signifying that sol id unconsumed carbon B S N 61 OILER DE IG .

is being given off if th e engine is run at slow Speed the smoking will stop,but the evaporation of water wil l not be so great as when

t en ine is worked at a much hi h er s eed he g g p . The reason of this is that the blast brings only a sufﬁcient amount of air into the ﬁrebox to transform the carbon into 00,carbo n- monoxide,a colorless gas, n h givi g out fourteen units of eat. If the engine is made to run faster,the more oxyge n brought in allows th e products of combus 00 h tion to approach or attain to 2,whic evolves out in the chemical

- change twenty two units of heat . These extra eight units of heat,

— M E or rnoronrl onmc Fi . 47 . T D Fi 46. g. g HO CHIMNE Y, AN D BLAST IPE S P .

of course,produce a correspondingly greater amount of steam and

meet the greater demands of the engine . The original and ﬁnal arrangements of bl ast pipe are sh own in

c f o r th e t t was n th e sket h . The necessity al era ion found by putti g

- n t th e a short piece o f l i . brass ube in top of chimney,making an

— was extension stack the effect upon th e steaming most marked. A very simple graphic method of arriving at chimney and

4 . tt s petticoat pipe proportions is shown in ﬁg. 7 Pe icoat pipe are to be recommended wherever possible, these additions greatly

’ improving th e e fficiency of th e apparatus . In a coal or charcoal - bu rning model the blast of the engine 62 MO V : rrs E S N consraucrl on THE DEL LOCOMOTI E D IG AND . should keep the fire absolutely bright and clear,lifting the flame n at every beat,and mai taining a full head of steam at all speeds. Oi course to do this the val ves must be properly proportioned and the valve gear accurately set,otherwise,in spite of possibly excellent arrangements in the smokebox,a good draught will not be t 1 created . Th e beats should a ,say, 00 revolutions per minute be absol utel istinct and at re ul ar interval s y d occur g . The smokebox sh ould be quite airtight,and it sh oul d n ot be p ossibl e f or one to see the rails by looking down th e chimney,as in ’ instances which have come under the writer s notice in the past . The blast pipe should also be exactly in the centre of the chimney,th e exhaust pipes meeting to form a single jet th e dirco h tion of w ich should be truly vertical. Under good conditions a coal - fired locomotive boiler working at

m 2 in 1 . t 0 0 s . its maxi um will evaporate about cub . of wa er per q

in u . ﬁr . of heating s rface per minute Smaller boilers ed by oil will

— 1 5 in evaporate less somewhere about cub . . per minute,loco in motive type boilers of about f . scale evaporating about }1 of ’ in t u 1 in er a cub . . per minu e,and Smithies type abo t cub . . p

1 i . s n a . minute per 00 q . of heating surf ce

F THE STREN GTH O BOILERS .

Th e strength of the boiler for a model locomotive should be i w considered in preparing the design . O course ith given thick nesses of material and diameter a plain cylindrical boiler made from a piece of solid drawn tu be will be the strongest,and in th is respect the water- tube boiler scores very high ,very few joints of t Wh h a weakening charac er being necessary . en the s ell is made from she et mate rial rolled into shape with a longitudinal join t,th e h l efﬁcienc A strength of t e boi er depends on the y of this joint .

e - 50 singl riveted lap joint will work out at about per cent . of the strength of the solid material,and a double- riveted lap joint at 5 1 h 7 per cent . Flat ends should be made }times the t ickness of the shell plates,an d tube plates thicker still. To ﬁnd th e bursting pressure of a given cylindrical shell,the following formul a may be employed 1

1 Terms in l bs. and inch es . B L S N 3 OI ER DE IG . 6

CO er i - t pp bo lers : x plate thickness x 2 diame er.

2 - Brass boilers x plate thickness x diameter .

e : 2 St el boilers x plate thickness x diameter .

Where single - riveted longitudinal joints are employed,divide the

- i resul t by 5,and for double riveted seams divide by i. To ﬁnd th e working pressure,it is assumed that th e boiler will be safe if worked at a pressure which,if multiplied by a con stant or factor of safety (a number arbitrarily ﬁxed according to the ideas of the designer,and which varies from 6 to will h equal t e bursting pressure . Therefore for a boiler which has a bursting pressure of 1 000 l h the working pressure may be either 1 00 6 : 1 66 l 0 b. 1 000 l b or .

or 1 000 1h .

The most usual factor for model work is 8,a lower ﬁgure being used only where th e boiler is of the be st design,and made of the th e best material and in most workmanlike manner . Wh en it is required to ﬁnd the plate thickness for a known diameter of boiler the following formula may be used,an allow a t u nce . for de erioration from r sting being made where steel is employed D x WP x F x R Thickness in inches , S x 2 where

S : Strength of material copper, brass, steel), = r . WP Working pressu e in lbs per sq . in F = Factor of safety (6 to R = Al l owance for riveting ( 1 4 for double riveting, 2 for single), = 1) Diamete r of barrel in inch e s .

- a h Flat surfaces of over 3 in . rea,w ere the plates are of abou t the same thickness as the shell,shoul d be stayed with screwed stays,th e total ultimate tensile strength of which should equal the area of the plate to be stayed one and a half to twice A l th the workin g pressure of the boiler . l owing for e threads, H N N S N 64 T E MODEL LOCOMOTIVE : 11s DES IG AND CO TRUCTIO . screwed copper stays of the following diameters wil l support l in 2 B . A 2 b t . 5 . c . 1 . opper or brass s ays, threads 5 3 3 g 00 3 1 g 400 i 500

3 273 0 steel stays,Whitworth threads . 1 4800

ﬁ ox 6 4 i Thus a reb side measurin g x n. , the working 6 x 4 x 1 00 1 00 2 x 1 2 3 —in pressure being ,would require stays . 400 1 3

m r d1a ete .

1 in 1 in Stays in models up to . scale should be from ?g to . ﬁ o apart. I n larger engines using steel reb xes the stays may be

- 2 4 in . 2 in th th e to apart ; for instance,a . scale boiler wi sides ﬁ box 1 2 in l on 9 in h t re . x of inner g . hig may be s ayed by four

- 3 in . in t ff Q steel stays,the plates being 1 6 . hick ; the natural sti ness th e ﬁrebox of these in itself helps to prevent the bulging of .

i 48 — RTL I I D -1 N F . A F E E . P S LE M D E . L E X PR L ocomorrvn g A Y N SH 2 CA O SS .

MO V rf s S N N S N 66 THE DEL LOCOMOTI E : DE IG AND CO TRUCTIO .

’ monetary) are th e assets of th e maker,the author s advice is to build the engine,both externally and internally,as much like the original as is possible,altering onl y to suit practicable considera tions of manufacture or design . Wh ere the model engineer desires a reliable working model,the component parts should be comparatively simple and th e locomotive th need only be to scale externally . E very ing that is hidden,or needless from a pictorial point of view,may be omitted or modiﬁed . For instance,frames need no t be shaped in accordance with those of the prototype where they are not seen ; cy1inders and motion may be of very differe nt design and construction ;th e boiler can be radically altered so long as th e external dimensions are adhered to indeed,the object of this vol ume chieﬂy lies in giving some idea as to h ow much it is advisable and necessary to modify in the

workin O h se construction of a perfect g model locomotive . t erwi , t t d suﬁice any of the s andard works on the locomo ive shoul .

- in to in . Frames the smaller models, say those g scale ,and h nt smaller,may be of s eet brass . Small qua ities of this mate rial are readily obtainable,and it will be found very easy to work . I t may be procured in strip form,and rolled or hard brass should be asked for . Th e following thicknesses have been found most suitable for W h ornbl ocks model locomotives . here are not used,the thicker material shoul d be employed

7 —in t 1 6 . scale hickness 1 9 i s

’ . ?’ g or zﬁ g 3? 1 3 ’ 1 6 3 s

Soldering is possible with steel plate,but brass joins very much more readily,and as in th e tinier engines,parts are commonly afﬁ xed to th e frames with solder in addition to screws or rivets,

Th 7 - . e in . brass is invariably adopted frames of 1 3 and Q scale N S N F S 6 CO TRUCTIO O MODEL LOCOMOTIVE . 7 models of the simpler type may be made of tinned steel ( or iron) plate of the thicknesses given ; this material of course takes s s ff older as readily as bra s . The bu er planks may be of the same material as the main frames,and are be st attached with angle plates and screws or rivets,this depending on whether inside or outside cylinders are empl oyed,it being usually necessary in th e former types to make this portion of the frames removable for purposes of piston packing and repair . Wooden buffer planks are to be recommended for small models, as the engine may be more comfortably handled than one in which ’ t Oi for ol — ii me al is used throughout . course s idity s sake the frame of the engine is not considerabl y strengthened by other

' parts— a metal buﬁer beam placed behind the wooden one shoul d h connect t e two main frames rigidly together. As wil l be seen in the designs contained in these pages,stretcher plate s of the same material as the frames are commonly used to

Fi 49 — T U E D FR M E r s c s ns R. S n r n . g. . N A transversel y connect the main frames together and to stiffen the d th f l fi whole structure . In mo el work where ese stretchers u l no other duty (such as that borne by the transverse plate behind the cylinders known as the motion plate then the builder will fin t r fi 49 d the turned dis ance bolts or frame b aces shown in g. us h as serve j t as well . The writer employed these in models of fi t th all scales and nds them quite sa isfactory. It is easier for e amateur to turn these bolts to the right length over th e collars than to flange a steel plate truly square in all directions,or to fi n prepare a patte rn and nish a casti g. Cast brass ( or gun- metal) is sometimes used for main frames, ’ but as a rule the material is not worth the amateur s considera tion ;it is very suitable where models are to be made in bulk

Lu afﬁxin t h ornbl ocks commercially. gs for g footpla es,and also , 68 THE MODEL LOCOMOTIVE : rrs DESIGN AND CON S TRUCTION . may be cast in position,thus saving a considerable amount of

H - n c labour . owever, the pattern maki g ne essary will usually dete r th e maker of a single engine from adopting th is course . To test frames for squareness,the length s and width s be ing found correc t,a rule or other measure should be stretched across diagonally,and if the structure is n ot truly rectangular in plan,th e lines A B and C D will be of different lengths,as h 5 l . the sketch ﬁg. 0 wil s ow Fi 50. g. A11 centre l in es sh ould be marked clearly on frames,more especially those relating to cylinders and ‘ ’ motion,and th e usual method of centre popping at inte rv als along these lines is advisable,so as to prevent the total obliteration of the marking . In the accompanying detail drawing th e frames for a mo del

- in D C R d . scale unalastair aledonian ailway locomotive, esigned E h b M r . L . H se y . Pearce,are s own ere the prototype is very clo ly followed and a plate stretch er is employed in th e front of th e

ﬁr box e , a cast footplate being adopted as in the original . The h h —in frames s ould be cut out of mild steel s eet, f g . thick . Th e outline of th e two frames should be carefully set out on a 3 l i . 2 in . on 1 n M th e t piece of steel g x 0 wide . ark cen re of t h e nd a in ch h pla e at eac ,and t a distance of 2 . ea side of t is scribe two parallel lines th e full length of plate ;th ese will be t ll l 4 in . apar ,and wi be the centre ines of cylinders and coupled axles,from wh ich all the dimensions for th e varying depths of A h n to h h frame are given. t rig t a gles t is t e centres of th e d h cylin ers and of t e driving and trailing axles . should be marked off B th e th . y setting out the two frames at same time with e top edges towards the centre of th e plate,all the centre l ines at right to th e h th e two a angles lengt can be scribed across fr mes at once . The centres from wh ich the various curves are struck are sh own by a black dot ;and th e centres of most of th e holes for rivets, screws,or bolts,used in ﬁxing th e axl ebox guides,cross frames,and cylin ders,are shown by a small When th e outline is complete,holes should be drilled all roun d the outside,clear of th e line,th e plate put on an anvil,and the a h th h met l cut throug wi a hammer and cold c isel. Then drill N S N OF M S 69 CO TRUCTIO MODEL LOCO OTIVE . : I N 7 0 THE MODEL LOCOMOTIVE I TS DES IGN AHD CON STRUCT O .

' in th e holes 5 . diameter at several points along . two frames,and rivet them together with copper rivets,ﬁrst seeing that the centre h e d s ed lines,which should be outside,coincide at t e ge . The ges

‘ can then be ﬁl ed down together to the exact outline,and th e holes marked out for rivets or screws can be drilled through the two e plat s at once . The axl ebox guides,footplate casting,motion plate and bogie pin casting,should all be cast in gun- metal,and the holes in them

3 - W in t in . h w th e will be drilled 3 2 . diameter for apping ﬁ it orth,

screws being put in from the outside . I t wil l be noticed that the frames are set in near the motion plate to give more lateral play to th e bogie wh eels, and are further set at angles in front of the cyl inders u for the same p rpose . The cyl in ders and motion li in plate,s de bars,etc. ,are this design carried on an 1 — XILI R FR M E 5 . . Fig. AU A Y A auxiliary frame (sho wn in ﬁ 51 h d g. ) whic is bolte to the main frame,and therefore can more easily be erected and readily removed from the main frames for packing or repairs without upsetting the relative alignment of h s oi th t e . ese important portion . engine This arrangement is certainly advantageous,where inside cylinders with four bars

and valves between are employed . The cylinders in small engin es— more especially single -cylinder engines where the ordinary commercial type of cylin der is adopted may be fixe d to a flanged horizontal stretcher passing from side frame to side frame as shown in the single - cylinder design , the outer end of the slide bar being supported by a similar but smaller stretcher,or to a turned frame brace,or l eft without any fixing at this end whatsoever (see page The h ornbl ocks or axle guides for the Caledonian engine shown

ﬁ 54 h ornsta s— in g. are of the orthodox design,the y which,by the way,are sometimes erroneously called keeps — being of cast brass,lipped at ends to render th e frames less weak at th e axl ebox n s to u d s ﬁ s 53 openi g,and secured by crews the g i es ( ee g . and S 7 1 CON STRU CTION OF MODEL LOCOMOTIVE .

The rear end of th e frame is ﬁtted with a cast footplate . This is used very often to add weight to a four- coupled bogie engine,and to keep th e centre of gravity well back,as in these engines it Wil l k generally fall in front of the driving wheel, when a greater weigh t than is advisa ble will be thrown on the bogie, and th e adhesive weight considerably

’ h s lessened . T i casting is cored for draw a ff . b rs and bu ers — 4 H L O0K S . 5 . ORN B Fig. In contradistinction of the more com pl ete method of building th e frames adopted in th e model just

ﬁ ten - referred to, g. 55 shows the frame of a model wheeled tank

E k E V AT l O N

- 28 o ver

— - - S L E TE N E E L E D T TIVE . M E 1 N . Fi 55 . FR MI OF D L g. A NG A O 2 CA WH ANK LOCOMO

2 m locomotive furth er described on page 68 . The fra es here are

- t an d w h few of f g in . mild steel pla e,and are arr ge it as deviations from the straigh t line as possible. 72 THE M L VE : I TS E S N AN D C N S N ODE LOCOMOTI D IG O TRUCTIO .

To save pattern - making and to simplif y construction,the axle

m - in h e n box guides are si ply pieces of i . plate riveted on to t mai frame,the h ornstays being castings or pieces of stout angle brass shaped as shown in ﬁ 56 g. . Th e bogie wheels being th e scale equiva t 3 f it len of about t. in the real engine, is possible, in this design , to cut away the m m , frames and allow both pairs of bogie wheels to swing under th em,as recommended in

Ch apter 1 1 . Al so,to give sulﬁ cient lateral play to the trailing radial truck,the frames

i - h are set in beh nd the rear coupled w eel . Th e motion plate is cast brass,and carries

the pivot of th e Bissel type leading bogie . A hole is cut in th e frames for th e face of Fi 5 6 . g. th e connected steam chest to pass th rough, and th e leading guard iron forms also an angle bracket to take ff the thrust of th e bu er spring. One of the chief points in this design is th e meth od of obtaining th e t th e firebox A h fi rebox all maximum wid h for . s allow being that is necessary,the frames are cut down to footplate line behind th e driving axle,the foundation ring of the boiler resting on the th 5 e fi . t a top of frames as shown in g 7 and Pla e IX. ; and to obt in th e greatest length o f firebox without unduly increasing the coupled wheel- base,th e back plate of the boiler extends over the h th r v h ut trailing axle . T is of course,wi large d i ing w eels,c s down he th e th fi t depth of frames at e point X in g. 57 to a dangerously weak degree,and to reinforce th e frames the axl ebox guide is carried over th e top of th e opening in one piece and a plate riveted W on the inside as sh own in upper part of th e sketch . ith the strength given to th e structure by the hornstay,this otherwise weak point is made quite as strong as it would be if it followed th e t a more ordinary practice . In fac ,it may be s id that the plate frame is changed to th e American bar system at th e portion under o c nsideration . Axl eboxe s form a feature in th e construction of a model loco t wh h h r od mo ive in ic t e e is a very great possibil ity of m ification .

74 THE mob st L M T E : rrs ES GN AN D OCO O IV D I CON S TRUCTION .

road,and does not bind in horns with an excessive up- and - down ec if movement,esp ially the bearing face of the flange is slightly rounded at the top and bottom faces of the shoul der,as indicated fi . 61 , th e n by g than usual ki d with two flanges . Axl e b x o es may be made with only one flange and fitte d to m h ornbl ock fra es having no s. A bearing having a spring pin

5 “ s a c r um : E . F

T I l N A . S E C O N . B . S E C T O C D

Fi 58 Dmvmo g. . AND COU PL ED - Axnnnoxrs ,2 1 N .

SCALE.

— w ' i 1 i 6 — i 62 AX L E B X E S rrn ovr KEE P F 6 F 0. S I PL F O . . . E g. . S g g. M L AX L E B X oco O . un derneath it,must be placed on th e axle (ih inside - framed en gines) before th e wheels are attached ; but for carrying wheels axl e boxes can be made without any keep whatever,the hornstay preventing h h i t e wheels falling from the frames altoget er. Th s arrangement provides plenty of drop for the wheels,which is essential in small ni S h engines run ng at high peed over comparatively roug roads. ﬁ 62 ﬁt in axl The sketch, g. ,also shows another method of t g eboxes

W m i - in th e . n . frames here fra es are about l g i thick a saw cut V 5 consrsvcn oN or MODEL LOCOMOTI ES . 7 is made in the sides,and with a warding fil e cleaned out to size as h h ornbl k ce s own . No oc s or other guides are ne ssary other than an oblong opening in the main frames and a hornstay, fi 64 6 . An even simpler device is described in gs. 3 and Here the axl ebox is not provided with any flange,being placed between the wh eel and the frame,in which a slot of th e same width as the diameter of th e axle has been cut . Axl eboxes made in this way are suitable for models of g,4,

- and gin . scales,and will be found a

- great improvement over th e old fashioned ' S fec i pl a l e method of providing no bearing springs i 63 — S r'r M E S F . 1.o s n FR g . A whatever . D H oansm r AN .

B oe ms.

Before describing the various methods in which bogies are constructed,a few words as to the principles involved

' shoul d not come amiss . A bogie is a wheeled carriage entirely separate from , but attached by a centre pin or pivot to, the main frame of the engine,and in locomotive work is generally supported on four wheels of small dimensions . The use of the separate truck gives flexi Fi 64 — AX L E BOX I bility to th e wheel - base of the locomotive g. . N POS ITIO N . wh en it is passing over curves and cross ings,but it must be distinctly understood that th e fitting of a centre pivot,under the majority of circumstances,will not,alone, T . he 6 B accomplish the required object accompanying fig. 6 ( ), shows in plan what is likely to happen to an engine with a partly rigid wheel- base and a bogie with a centre pin only,if th e leading

u th e u wheel of the bogie tr ck and co pled wh eels keep the road . Diagram A shows the engine provided with a lateral sliding movement as well as a revolving movement,all th e wh eels keeping the road on a curve . ’ ’ Th e sliding- box type of bogie is known as ‘ Adams paten t, and 76 THE L L M T : rrs S GN AN D C N S R N MODE OCO O IVE DE I O T U CTIO .

use s is in universal . For model work it is the very best,and allow th e A utmost freedom of the locomotive on sharp curves . nother form which is suitable for models which are not intended to run over excessively sharp curves,and is much the same in action — li t — b with mi ations is the Bissel ogie (see ﬁg. 67,C) ,which is pivoted some distance behind the rear bogie wheel— about half wa n y betwee the latter and following rigid wheel . ﬁ 6 The diagram D , g. 7,shows a method which may be adopte d for single engines not expected to negotiate curves of compara tivel A t v e y small radii . cen re pi ot only is used for the bogi

Fi 66 g. .

h i uo ro n y

Fi 6 g. 7 .

(th e pin may be placed a triﬂe out of the longitudinal centre— a little nearer the rear bogie wheel),and th e trailing wheel,which must not be a coupled wheel,should be given a certain amoun t o f i e l axl eboxes side l a th e s d p ay in the . This p y allows the body of engine to swing over in th e direction of th e curve,and re nders th e

- slide block slot unnecessary . For a high—class model th e standard practice sh ould be followe d , suitable arrangements being given on pages 69 and 83,and Plates t C . VII . and VIII . ,for the aledonian and designs respec ively Both of these examples closely resemble that of th e prototypes,an d h e n t are also very much alike . T e controlling of the lateral movem 69 . s of th e sliding box is accomplished by spiral springs . Fig show a simpliﬁed form adapted more especially for the design for a model

W - s E . N . L . . type ten wheeled tank locomotive included in thi N t l n n ﬁtte d n ad volume . o con rol i g spri g is ,and the slidi g box or p L CON S TRUCTION or MODE LOCOMOTIVES . 77 may be either as shown or h ave a circular boss (see dotted lines in plan of detail ),according to the sharpness of the curves of the l railway and th e amount of sidep ay required. Th e cover of the steam chest forms the bogie pin casting in this hi be th e design. T s course may adopted in many designs where cylinders are directly over the bogie .

i 68 — TH E Boom F OR M D E L L D N D T - W L F . T I g. A O ON O AN SOU H E S E R N RA WAY L M TIVE M DE BY M e ssns Con es OCO O , A . .

Th is vie w sh o ws th e arts se arated and th e l aminated sid e -con rol l in r ( p p , t g sp ings . )

’ Adams type of bogies for smal l models of a simple character may be made by simply slotting th e cross stretcher or bed - plate of the bogie to ﬁt a centre pin attached to a similar plate on the main

fi . 71 n t frames as shown in g ,which more or less explai s i self. Another simple method is depicted in the accompanying sketch fi n C . I I ( g and comprised in a desig on Plate I . ontrolling springs may be employed without much trouble,and no castings are required to be affi xed across the main frames,two turned t A braces on which the pivot block slides being substitu ed . cast - o l bogie cross frame is of course not abs lute y essential . 8 VE rf s D 7 THE MODEL LOCOMOTI : DES IGN AN CON S TRUCTION .

l a . N S F D M S CO TRUCTION O MO EL LOCO OTIVE . 80 THE M M rrs S N AN D r' ' x ODEL LOCO OTIVE : DE IG cos s sucn o .

On some railways it is the practice to control the lateral move d ment by slinging th e bogie on links (see ﬁg. and this shoul u ds work o t very well for models. The links should be set in towar h d e the centre at a slig t angle . For bogies nee ing a considerabl side l a th e as b amount of p y links should be as long possi le . There are very many methods of arranging bogie attachments, but these must be left to the reader to work out for himself, and the question of suspension of the bogie wheels on springs

’ proceeded with . Tiny models may be built with bogies having no springs,the

' axles simply running in plain holes in th e framing, a spiral spring or a comparatively large piece of indiarubber being placed

‘ f ra m e J /r aﬁ'h e

B o q t e s f r c/b h c r i 4 Fi 5 F . g. 7 . g 7 .

between th e cross plates of the bogie and main frames respectively. s is ﬁ s 4 and 5 r b er An example of thi method shown in g . 7 7 ,the u b h the te pad in th e latter being protected by was ers of tin . In volu spring arrangement the lower tray prevents th e spring fouling th e

an Th e t f or slot d keeps it quite central . best rubber is tha used cushions of india - rubber stamps used in ofﬁ ces,this material being

u cell lar in structure . Larger and more complex model s shou ld have better arrange ments than th ese,and one giving th e least trouble in manufactu re, and generally th e best resul ts in running,is shown in th e accom h ﬁ panying photograp ( g. Locomotive engineers in E ngland are divided in th e use of th e equalising or compensating beam,both for bogies and rigid wheels ; but wh ere railroads are not so perfect as they are in th is country, h u u M t e eq alising beam is niversally employed . odel railways do not as a rul e attain a proportionately high degree of smooth ness, and th erefore,for bogies especially,th e equal iser is to be recom mended .

N 82 THE MODEL Locomorl vs : rf s DESIGN AN D CON S TRUCTI O .

Any pattern of axl ebox may be employed,and th e equalise rs should be provided with rounded projections where they bear on

‘ ’ - — E L ooon orrvs . A I E L B oe rs s on I N . S OAL n M D L Fi 8 . B g. 7 SS A g O

the tOp of th e box,or the latter ﬁtted with a vertical stud engagin g

a corresponding hollow in the beam .

n d w Q rs Q r c . M

— E N B 79 . C P TI E M D S PRI F OR B oe rs H WN I N G 6 OM SA NG A AN NGS S O FI . 9. N S N or M V S 83 CO TRUCTIO ODEL LOCOMOTI E .

T h e S t the prings may be ei her laminated or of spiral pattern . S piral springs give greater life to the engine,and being more easy o f wa A adjustment,are to be recommended in every y. solid e qualiser may be also employed,in place of th e usual built- up s t truc ure having lami . E n ated t th e V springs be ween I T ﬁ O plates as shown in g. o 8 0 s c ,a de ign which on a o L w orking model is not advised f or scales smaller than one inch to the , foot,and even then it E may be dispensed with in favour of a simpler pattern . Th e buckle of the spring is carried in the latter instance from a heavy stud afﬁ xed to the bogie side plates . It shoul d be noted,in set

' ting out bogie arrange ments, that sufficient c learance must be allowed 80 at point X,fig. ,for the rise and fall of th e com pen sating beam . Here th e axl ebox guides are o f necessity placed out sid e, and cannot very we ll be extended over th e top of the opening in th e side frames. Bissel o t fi bogies are very easily constructed fr m shee material (see g. 7 6) without the use of castings (except where a controller is e mployed) . The pivot bracket may be attached to or cast with c fi 84 h w th e motion plate (see fig. the sket h ( g. ) s o ing the b racket used as first mentioned and with the co ntrolling gear 84 Locouo'n vs : rrs S N AN D n r c on THE MODEL DE IG co s su n .

ﬁtted . This gear,by the way,is not necessary in models smaller h i t an { n scale .

R ADIAL TRUCKS .

Single pairs of carrying wheels are very often fitted to the main frames in such a way th at they can take up a radial position wh en un u the engine is running aro d a c rve . The simplest form of arrangin g this to a model locomotive is indicated below (fig. The truck is pivoted from a convenient bracket or bar at P,the axles being fitted into plain holes in th e A i t upturned portion . Spiral bearing spr ngs in ervene between the main frames and the pony truck as illustrated in th e sketch and in fi 2 5 5 . th e g. 3 8,page 5 The nuts on the spring pin prevent truck i l falling away from the engine when it is l fted up from the rai s . The axl ebox may be separate from the bed - plate of the truck ; the elevation of this portion in relation to

th e main frames is il lustrated in ﬁg. 8 1 , sufﬁ cient distance being all owed between the axle and the main frames for th e maximum compression of th e spring, th e

Fi 81 . ° g. lateral swin g of th e truck being controlled by th e upright bearing piece,which should strike th e frame and u h m v th e D ﬁ 8 prevent f rt er o ement of wheels as shown at in g. 2. A constructively superior arrangement on this plan is illustrated l V in the tank locomotive (P ate III . ) Here the pivot end has a ball - and - socket joint, for purposes of increased strength,and the other is prevented from rising too high and fouling the main frame by the transverse stretcher just behind the wheel centre,and from falling away by th e pronged collar which at its centre is afﬁ xed to a squared stud,attached to th e aforesaid stretcher,passing th rough a slot in the bed-plate of truck The prongs should not quite reach each side frame,th e distance between them regulating the play of the truck,and to control the arrangement spiral springs of the same length may be n placed one on each pro g as shown . A construction wh ich may be considered stronger is to allow no t th e side n th e L N . W R . ver ical movement to truck ( the desig for . . ? M T S CON STRUCTION 01 MODEL L OCO O IVE .

“ - in i ten wh eeled tank,Plate IV . ) shown the accompany ng detail Th e e drawings (fig. controlling arrangement us d for the fi 8 r Bissel type bogie ( g. 7 ) may be employed, the bea ing spring gear being wholly contained in the pony truck. The fi 8 5 r perspective sketch ( g. ) shows a slight va iation from the drawin gs above referred to,sheet material being in tended,and

Tu g c u r w ar) ; o r

tm s M r

OM I TT E D f R O M VI ! ”

— Fi 82 A S I PLE P N TR . g. . M O Y UCK

Fi 3 — - S M E . 8 . N I N LE D L A P R F R . g O Y T UCK O A i . CA O

the lug on the end of th e spring bar being replaced by a projection x x ﬁ i on the top of the a l ebo . A modi cat on of the usual form of l a ax ebox ﬁ 86. is r dial is shown in g. It cons ts of two curved slides with correspondingly curved axl eboxes,with a plate at th e top to n and bot m rigidly connecti g each . The controlling gear is very

clearly explained by the sketch,and needs no further description. One point which must not be overlooked with this type of radial 6 HE : rf s S N AN D n 'r ' 8 T MODEL LOCOMOTIVE DE IG co s auc n ou . axl ebox is,th at if one wheel is depressed and the other whee l raised by the inevitable unevenness of the track,to any considerable extent,the axl ebox will bind ;indeed,if the box were made what is called a working fit in the slides,it woul d be found incapable of t v e even the sligh est tilting movement in a ertical direction. Ther fore,as it is in the real locomotive,the boxes must be made a very slack fit in the guides. This seems to be the chief disadvantage of the arrangement,which,by the way,should not in any case be fi i i l t n . ted to engines under i sca e . To remedy its faults,the write r the fi 8 s 8 . suggests arrangement shown in g . 7 and 8 The curved frame is here fixed as regards vertical movement in the slides,small

— Fi 85 — S m'cn or B R N G . n E I Fi 84 CON TB OL L I N G GE R F OR . g. . A g A ‘ B I BS E L D P N Tauons SPR I . AN O Y . NG bearings capabl e of u p- and - down movement and connected to th e h is springs working in t e frame . Freedom of action essential, h owever,in all parts of the arrangement ;and where the work is not done with machine tools,th e grinding of th e frame in th e curved slide should secure the desired result. To save screwing the top and bottom plates of th e curved frame,these may be silver ﬁ soldered to th e axl ebox guides (see g.

K BUFFERS AN D D RAWHOO S .

Buffers for model locomotives should,as a rule ,be ﬁtted with springs,and,wherever possible,steel (or german silver) should be h ff used for the eads. Two kinds of bu ers are common to British A B ﬁ locomotive practice (see and , g. each railway company b having its own particular pattern . The standard distance etween F S CON STRUCTION O MODEL LOCOMOTIVE . 88 THE : I TS S N AN D N S N MODEL LOCOMOTIVE DE IG CO TRUCTIO .

ff 5 f 8 ff i . r bu er centres is t. n ,and from the rails bu er and d awbar 5 3 f in . centres measure t. 5 The type of buffer B is,in small models at least,best arran ged ff T as wn ﬁ . 1 h with the spring behind the bu er plate, sho in g 9 . e

- L N D N D N R T WE TE R R IL Y R E T CE TR L . O O AN O H S N A WA . G A N A

— - Fi B E PE S Sca e ih to th e foot. 89 . R TY g. UFF . ( l ,i . )

Fi 91 g. .

ar wa s h e r

' — - Fi 92 D R AW H OOK S . Sca e in . to th e foot. g. . ( l ,2 ) other kind may contain a spiral spring in th e casting,after the

fi 90. usual manner,as il lustrated in drawing, g. D rawh ooks for small models need only be screwed and riveted h e ff h the into t bu er plank. In eavier engines,however,one of A C in fi 92 two methods shown at and g. may be employed with t advan age . Side ch ains are often fitted to th e buffer planks of real loco

C H APTE R VI .

WHEELS ,AXLES,CRANK Am s,AN D BEARIN G- S PRIN G A E N S RRANGEM T .

W — Th i HEELS . e size and kin d of wheels employed on a locomot ve min to are dete r ed by the general design . They may be divided in three classes 1 v h ( ) Dri ing w eels. 2 C wh ( ) oupled eels . 3 C h ( ) arrying w eels. Wh eels in actual practice are made in two portions,the tyres being separate from the centres and different materials being C t me employed. oupled wheels are of course of exac ly the sa diameter as the driving wheels,the chief difference between the two being in the disposition of the balance weights. For outside - framed and inside - cylinder single engines a circular boss (or knave) is usual,whereas the wheels of inside framed outside - cylinder locomotives and inside - framed coupled

- engines have pear shaped bosse s to take the crank pins . Great care should be taken in proportioning th e wheels of a model locomotive,as nothing will more easily spoil th e appearance of an engine than wheels of inferior design ; for instance,an insufficien t number of spokes,spokes of incorrect section,tyres too thin or too thick,and balance weights pl aced in impossibl e t posi ions . Th e spokes should not be too square in section,and should flow into the boss and rim of a wheel with suitable radii and flowing

curves . To save expense in moulding,patterns have generally to be made with the spokes and rims tapering to allow of an easy 90 W S S AN D BE N - S N N S 91 HEEL ,AXLE , ARI G PRI G ARRANGEME T . w h th e a fi H it drawal from s nd ( see g. owever,the front of the pattern may almost exactly conform to the pro fil es of the finished wheel ,the filing up of the spokes being done at the back,as is nd ca the a t th e i i ted by sh ded par of section .

' WH L E ms FIVE Fr. s1 x I N . EE WH E L F OB. Ours 8 1 1 Fr.

LI DE F OB IDE C LI DE RS . CY N R S . INS Y N

‘ ’ FT S I X I N ~ WH E E L F OR m ' F' S I N GL E WH EEL E ur r. I N IDE CYLIN DER T ID LIN DE S S OU S E CY RS .

— Fi . 95 . T PI L L ocomorl vs D IVI W LS g Y CA R NG HE E .

Dotte d l ines indicat e b al ance wei h ts for co u l ed wh l S l -in o th e f t e ca e . t oo . ( g p e s. ,i )

The best rule for ﬁnding th e number of spokes in a locomotive . w heel is to multiply the diameter (in fe et) of the wheel of th e

o 3 l 3 e w pr totype by for small whee s and 1; for larg r heels,making

the t t to - th e in . c o al up an even number. Taking 2 s ale C aledonian design on Plate VII,as an example,the driving and 92 L L ocomo'mvs : rf s S N N S THE MODE DE IG AND CO TRUCTION .

in . coupled wheels are 4; in the model,which works out to 6 ft.

6 i th t . 6 f n . in e pro otype Therefore 5 t. x spokes,the 2 nearest even ﬁgure being 2 . This is th e num ber used in the

prototype . The carrying (bogie) wheels 3 ft 6 i . n of the original engine are . d M iameter . ultiply this by 3 and the 1 result is 05. Ten spokes are employe d t in the pro otype . The cross - section of the spokes of a — Fi 96 . T RE E FT s . . 1 x I N g H . real locomotive varies according to th e BOGIE WH EEL - material used . Cast iron wheel centre s

( hi n w ch are not common) sometimes have spokes of I sectio . W - h rought iron w eels are provided with S pokes sligh tly more

a — 5 ' ﬁ é .

L B ‘ S C R d r a wn ? M I D L A N 0 S t a n d a r d t y r e t y r e

Fi . 98 g .

— LL IZ T RE S E TI N S F OR M DE LS Fi . 99 F S E . g . U Y C O O rectangular than those cast in steel ; see A and B respectivel y

ﬁ 9 - - s . in g. 7 for the wrought iron and cast steel spoke section Wh eel centres of cast steel are now universally used in large h ﬁn At th practice,and ave a very e appearance . the ends of e spokes where they join the rim,the section should measure th e

1 ih scale equivalent of about 35 x 2 . and at the boss about 2 in 5 2 . 45 x i in . or x % To enable the model maker,wh o does not as a rule use a separate tyre,to determine the depth of the rim,th e above sections of E S LES AN D B RI N - S P N E E 3 WHE L ,AX , EA G RI G ARRAN G M NTS . 9 th e standard rims and tyres used by two railways are included h erewith .

- For a gin . scale model,therefore,the depth ( D ) should be about

h - in . I in . ,but the best widt for models of g scale and above is a l 6 in i W e s n . sca e quivalent of . in tead of The dimensions ( )

- - n i in . w i . in n 1 ill be by this rule,g for g . scale ;1} . for in and g

-in c for scale models . For ﬁ . s ale locomotives the tyre should 5 9 i in . n . be 1 3; or 3 ; wide ;that is,if the engine is to do a fair amount of running over points and crossings . It will be noticed,by reference to the drawings of standard tyres, that the driving wh eels ﬂanges are made thinner than those of th e carrying or coupled wheels . This is to to allow a greater amount of sidepl ay and to prevent strains on the crank axle during s the passage of the engine over point ,check rails and crossings .

‘ The face of the tyre of a model wheel should always be turned in C ﬁ 9 h section as ill ustrated at in g. 7,to give the observer t e idea that the rim and tyre are not of one piece of metal. The balance weights will look better if made ﬂush with the face Y and not with th e face of the Spokes or the tyre,unless eith er h th e of t ese courses are adopted in prototype being modelled . A good appearance is gained where the counterweights project hi h sl ightly from face Y . T s projection,however,s ould not extend so much as to bring the face of the weight into a plane parallel to

h in - t e face of the tyre . Where,as inside cylinder engines it is required to obtain the maximum width between wheel seats (and th erefore between main frames),it is common practice to recess the back of th e wheel at the boss,also coning the front face of th e spokes . The front of the boss of the wheel will then extend out wards a considerable distance beyond the tyre face,in some as see ﬁ instances often much as half the width of the tyre ( g. This method,besides increasing the available space for cranks, eccentrics and bearings,lends an interest to the appearance of the wheel, and the coning of the front face and the out ward extension of the boss may be recommended in all model

locomotives . Reverting to the subject of tyre sections,the proﬁl e of a tyre will become less a scale reproduction of the real thing as the model c in l . 1 th becomes smal er in size For instan e,premising . as e 9 E M VE : rrs S N AN D N S N 4 THE MOD L LOCO OTI DE IG CO TRUCTIO .

ﬂan 1 th thickness of the ge of an actual locomotive and in . as e

- 1 t i in . an d dep h,these dimensions in a é n. scale model work out to 9 4 1 . o d 9 5 in respectively,and it will be seen that a very good railr a ' woul d be necessary to ensure the safe running of a model lo c o v fl h se motive pro ided with anges of t e dimensions. In practice,th e fl ul i an e in . in mo re g depth sho d never be less than gg ,g . being a suitable size,and to lengthen the life of th e wheels the thickn e s s h 1 in s ould not be less than 1 3 . A d f u i n fi set of tyre sections rawn to ll s ze is illustrated i g. 9 9 , from which templates may be made for use in turning wheels of

- - l 2 i . in n d . g . to sca e mo els If a careful comparison of the diagrams in this figure be mad e , th e reader wil l find that slight variations in profil e (irrespective o f depth an d thickness) are indicated . This is more noticeable in th e

‘ 1 2-in 5 and . scale examples,the latter having less rounding of th e edge of th e ﬂange,and a smaller ﬁll et or radius in th e angle o f

an t W fl ge and read . here the railway is not laid very closely to gauge,the section of the tyre had far better be more angular however,supposing the best quality of permanent way is e m ployed,and the railway is not out- oi—doors and does not have to with stand the rigours of an E nglish climate,then a much greate r amount of rounding may be given to the profil e of the flange wit h t n the advan age of a co siderably reduced train resistance . The treads of the wheels should;in all cases,be very slightly cone d , the angle varying in small models from 1 in 30 to 1 in 20 in larger engines . h Specific examples of w eel designs are given in fig. 95,page 91 , th e various siz es and types being drawn to a common

in . . scale,viz . ,i to a foot The diameters of carrying and tende r 3 f 6 n t. i 4 f t l . 6 n . i wh eels are general y from to . ; bogie wheels

4 f t. 6 f f . t 6 3 t to driving wheels of coupled express engines . in . ft 3 . in f t . to 7 . ,with two notable exceptions of 7 and i h in . ft f t. 7 . 7 S ngle engines have driving w eels from 7

R . 6 f . S O. t 6 i ft L B . . n . to 8 . ; the singles having drivers,and the W E ft 6 i E C L N . . . 8 . n . ornwall on the . xpress goods engine s

f t 6 in . 5 l 4 . ft have almost universal y to . wheels,and shunting

f 6 in . f 4 t . tank locomotives 4 t . or drivers . Passenger tanks are

l v s 4 f t. 6 in o general y pro ided with driving wheel varying from . t W S L S AN D B N - S N M N S 95 HEEL ,AX E , EARI G PRI G ARRANGE E T .

5 f t . 9 in the E b the . in diameter, L T. S . . engines eing exception w f 6 6 i . t. d ith n. couple wheels The practice nowadays in the case of in side - cylinder coupled e ngines is to reduce the throw of the coupling rod crank pin s to a i n d me sion somewhat less than the throw of the inside cranks .

- This procedure has been ad Opted in the gin . scale model illustrated 9 b I I I in . and y Plate . ,the outside crank pins being 1 6 out of centre, th - e in . inside cranks g . throw In outside 1 c ylinder engines they must be the same . Th e bosses for th e wheels in coupled e ngines with outside frames and all inside cylinder single locos being circular,the balance weights may therefore be in any position on the pattern,th e wheels being set in their proper places during the fix operation of ing them on the axles . Fi 95 91 g. ,page ,shows the driving wheel balance weights in the correct position for inside - cylinder engines having the right hand crank leading, the coupling rod crank pins being diametrically opposite to t n the inside cranks . The dot ed li es sh o w the position and approximate magni tude of th e weights for coupled wh eels of both inside and outside—cylindered single and double framed engines . There is t 1 no necessity to have the surface of th e spokes of carrying or bogie wheels coned other than for th e purpose of appearance, and the inside face of the bosses of th ese wheels may also be made h th e t ush with the surface of yre . There is no operation in which model practice varies so much as in the fixing of the wheels upon the axle,and it is hard to t O recommend one me hod or the other in all cases . ne of the best ways is to fix the wheels by boring the boss for a driving fit on th e axle,which should be turned with a shoulder or have a collar as fi 1 00 illustrated in g. ,the wheels being secured by a grub screw

’ 1 Th r are exce tions notabl th e N e e G. R A . . tl antic l ocom i p , y ot ves. 96 THE M E L C M V : 11 ' DE S N AN D N N OD L O O OTI E s IG CO S TRU CTI O .

th e o fr th e bac The t d driven through b ss om k . wri er has foun , however,that this method of se curing the wheel,whilst it facilitate s the removal,is sometimes troublesome,and may be substituted in d fixin fi 1 01 larger mo els for the g shown in g. ,where the grub scre w is driven parallel to the axle,h alf into th e axle and f t o H thi hal in o the b ss. owever,as s makes a more or less permanent fixing,a grub screw arranged in the first—mentioned manner may be used as well,an d shoul d suffice for th e securing of the wheel during t the construc ion of the model. Fi . 1 01 g . If mach ine tools of th e necessary accuracy are to hand,and if the maker is equal to the task,the wheels may be completely finished before fitting to the axles,the turning being

h - M accomplished on a mandrel or in t e self centring chuck . any readers will,however,prefer th e surer way of fitting the wheels truly on the axle by turning th e whole job between th e centre s t w first d of the la he,the heels being rough turne and bored. With coupled wheels great pains should be taken to get th e crank pins on each pair of the wheels involved exactly at righ t angles with one another,and also to see that the outside crank pins of an inside - cylindered engine are directly opposite to th e main crank pin s,although this point is not of so great importance to the fitting of the rods as th e first,th e position of the outside crank pins in relation to the inside pins affecting the balancing o f the motion only . Some model mechanics think that the driving wheels should be screwed on to a shoulder or collar,as by this means th e wheels s t may be taken off repeatedly . It mu t be poin ed out that ffi di cul ties arise where coupling rods are present . It is almost impossible to ensure th at just at the point where the wheels screw tightly h ome against the shoulder or collar on the axle,th e crank pins wil l be at the proper angle with each other and to the main

- l e crank of an inside cyl indered engine . Therefore,whi st this m thod of securing the wheels to the axles has some good points,it cannot be unreservedly recommended . However,for single driving whe els and carrying wheels,and through out in small locomotives,it forms one of the most suitable ﬁxings. The wheels should be rough turned on the back,bored an d tapped at the one setting,and for

: 98 THE MODEL LOCOMOTIVE I TS DES IGN AN D CON S TRUCTION . screwed part must be a very good ﬁt in the wheel,otherwise the pin will be constantly slacking back and falling out,but all th e

- same it wil l be found quite suitable for small models up to gin . scales . Separate collars fitted to a reduced end of the pin may b e employed for large engines,and the best practice is to fit a plain i fi collar,securing t with a split or taper pin (see g. A screwed col lar may be employed,but in addition to the screw ing a pin seems necessary . If an ordinary cheese-headed screw is used as a crank pin th e slot in the head shoul d be fil e d out when the model is absolutely fini h d s e . In all large models the crank pins shoul d be turned with a collar next to th e boss of the wheel,so that the coupling or con necting rods do not touch the wh eel on their inner faces . Th e crank pins for the coupled wheels of outside-cylindered locomotive s in wh ich the connecting rods are inside,nearest to th e wheel,mu st be extended to an amount equal to approximatel y the width of th e h fi 05 c . onnecting rod brasses,as s own in g. 1 Outside - framed engines having coupled wheels require outside .

a h n ﬁxed h ﬁ . 1 cr nks into whic the crank pi s are ,as s own in g 04 .

' Th e crank should be backed off towards the pin,and may be secured to the axle in the best manner possibl e by a pin passing through the axle and the crank,both of which should ﬁt each othe r perfectly .

B A E RING SPRIN GS .

Generally speaking,for essentially working models,spiral springs s h should in all ca es be employed . T ey are easy to adjust,simple

e S in ar to make ;tempered st el prings down to k . outside diameter e commercial articles,an d endless time will be saved where they are M used . odel plate springs are diffi cul t to make,and besides being h ff d muc too sti if ma e to scale,have little range of action . Slipping 1 8 very often caused by th e use of laminated springs on carrying wheels only,more especially in the case of bogie single x driving express locomotives . The e tent of the deflection of laminated springs being so limited wh en the road falls hollow at E S D B - S S 99 WH ELS ,AXLE ,AN EARIN G PRIN G ARRANGEMENT . th e centre of the wheel - base,practically the whole of th e weight of the engine is th rown on the carrying wheels,which do not h respond and equalise th e loads on all t e wheels . To give laminated springs more life than is obtainable if they are made to scale,and at the same time to allow of the over-all dimensions of those of the prototype to be adhered to,th e con t h d fi 1 06 th e t s ruction indicated on t e rawings ( g. ) for ender

m bearing springs for a model i in . scale Caledonian Railway loco motive,th e spring of the original having some ﬁfteen plates,is

F — - i . 1 06. B E RI SPR I S AN D H N GE R F OR 1 N S LE M DEL g A NG NG A S 2 . CA O CALEDON IAN RAILWAY L ocomorrvs TE ND E R.

Fi 1 0 — B E I - I A E E T . R P 7 . 8 R R R N G M N g A NG NG A S .

Th e — — suggested . back plate the longest plate of th e spring should be annealed at the ends,and be either carefully and slowly to bent form the eyes to receive the pins of the hangers ; or,which is perhaps a better meth od,have a piece of tube silver- soldered on

i . to t The ends of th e back plate,and also th e two plates above, must,before the spring is re - tempered,be forked to allo w the Th e hanger to work freely . e numb r of plates adopted for the

- model is seven,cut to the proper length from i in . thin clock spring,and to preserve the scale size of the spring,packing pieces s ih . x in of bras plate,about 5 i . thick,may be placed ' D c 1 00 THE MODEL LOCOMOTIVE : 11 s DES IGN AN onsraucn on.

h s in between eac plate . The plates should be ecured the buckle

- by a set screw driven from the top as shown. Laminated springs for driving and coupled wheels,where they ﬁ A ﬁ 1 are underhung,as is usually the case,if xed as shown at , g. 07, n t B cannot very well be adjusted . If the arra gemen shown at is

Fi 1 08 — DUMM L I TED P I . . Y M N S R g A A NGS.

p pe d

— Fi 1 09 SPRING PI N F OR 4 11 . S LE g. . 5 CA L TIVE OCOMO .

H a f size l .

— — 0 Ax1.s s 1 0 A AX L E B OX D SPR I S F OR Fi . 1 1 . ox D Fi . 9 S p n g . AN NG g AN mos s on - - S LE TIV l O I N . GE L TIV 1 1 31, L E . E 5 CA OCOMO i GAU OCOMO .

adopted,th e amount of weight to be borne by each axl e can be regulated by th e nuts B ,and should th e springs n ot exhibit too ’ much life, Spiral Springs may be placed between the hangers

and th e nuts as shown at C.

In Plate VIII . the use of compensating beams in connection with h t l aminated springs is illustrate d . T is cons ruction can be heartily

recommended for model work . From the drawings it will be seen

M DE L M rr S N D N S 1 02 THE O LOCO OTIVE : s DE IG AN CO TRUCTION .

- for a i in . scale model, e x S = s x s= sz = say e m 1 1 1 ﬁ . 1 1 Fig shows a straight axle for an inch scale model,and g. 2

-in h one for a i . scale bogie tender or other carrying wheel,in whic

Fi l l l — E I E AX LE g. . NG N .

— ms BE AR ENDER X LE F OB. vrs I Fi 1 1 T O . g. 2 A NGS

axl box u th A the e es and frames are placed o tside of e wheels . h ﬁ 2 w . 6 suitable box for the latter axle is s o n in g 3 ,page 1 84.

K A S CRAN ED XLE .

The manufacture of the cranked axle has no doubt dete rred many from buildin g an inside - cylinder model locomotive,and it is perhaps for this reason,and the fact that the difficul ties of fitting and erecting are increased,outside - cylindered engines are most favoured H by model makers . owever , “ ” needs must sometimes,an d the many ways in which a crank axl e can be made re n quire co sideration . The simplest method of Fi l l 3 — SK E T r C D I . o R N R G g . CH U A K N exem l ified C TR U TI construction is p by ONS C ON . fi 1 1 3 g. ,and should prove t i 9 - in . qui e su table for gr in . or 1 3 scale model, th e fol lowing

N 1 04 THE MODE L L ocomorrvs z 11s DES IGN AN D consraUcrl o .

description be ing arranged for th e crank axle of the single cylinder

design illustrated on page 251 . ’ The axle should be cut from a rod of Stubbs steel and be centred as accurately as possibl e,so that no turning will be required except

- 1 at th e Two x x in . wheel seat . pieces of mild steel fi flg 1 5 ,to form the webs,should be fil ed square,and in each two holes sho u ld

be d t r in ti h tl ' th e drille ,one at ei he end 5 . apart,to take,rather g y, axle and th e crank pin ; the latter can be cut off a piece of the same h l rod as t e axle . The crank pin and webs can be p aced in the ’ correct position ,and the whole sweated with tinman s solder. After th e preliminary sweating together the pins shoul d be fitte d as shown in the sketch,when the whole job may be again subjecte d t fl m h be o fit to the hea of the a e . T ese pins should a g od ,the holes h th e being carefully broac ed . To complete the work the pieces of axle remaining between th e webs may be sawn out and webs fil e d ’ u h p to the best of t e maker s ability . Oi course if a gas blowpipe of sufficient power or a paraffin blow lamp is available,then th e job may be brazed righ t away,the pins b fitted f l the re eing be ore the work is p aced in fi . Another method of building such a single- throw cranked axle is sh own in fig 1 1 4,and very good results can be obtained with a t v A compara i ely small amount of labour. flat bar of mild steel x 1 in {3 1 ); . in section (for the engine under consideration) should be procured,and with a hacksaw all superfluous metal at each side of th e webs should be removed ; th e axle can then be turned to its Th proper diameter . e piece of metal between the webs being cut away,th e crank pin may be turned by means of th row plates screwed fixed the or otherwise on to the ends of axle . A double - throw cranked axle can be made in a similar manner to the above,but in this instance it will be necessary to heat the axle at the centre and to twist the cranks at right angles after

tt n th e su erﬂuous m th e d r cu i g out p etal at axle as already esc ibed . The appearance of the axle subsequent to heating and twisting is d ﬁ 1 1 6 . illustrate by g. In a built up and brazed cranked axle for engines of larger

i 3 in and in c v h e . 1 . dimensions ( . . 4 scales) e centric shea es,where t ey are between th e webs,may be placed on th e middle piece before ﬁ tin a A h t g the p rts together for brazing. ll joints to be brazed s ould

1 06 VE : rrs S N AN D N S N THE MODEL LOCOMOTI DE IG CO TRUCTIO . some model manufacturers have already availed themselves of th is d A to metho ,and castings in several sizes may be procured . pho graph of a typical casting from a design by the author ( ﬁg. on which the centring lugs (or throw plates) are cast on th e axle,

2 — A ' C L E F - Fi . 1 0 CAs r R N X OR on I N S LE L ocomorl vs g A K A 5 ff . CA . i fi 1 20 fin h s sh own on g. ,the is ed axle being illustrated in th e 1 photograph on page 67 . The throw plates are cut off after th e fin ish ed crank pins and webs have been .

— - CRANK AX LE F OR 1 0 I N . GE L C TIV E . 16 1 21 . g. 1 GAU O OMO

- n s Cranked axles for 1 1 and 2 i . scale engines should alway ﬁ 1 1 be f orgings,or cu t out of th e ﬂat plate as shown in g. 6,the webs being twisted after cutting out . A crank axle suitable for

- ﬁ 2 in . 1 1 . a 2 . scale model is shown in g Webs should be 4 S - WHEELS ,AXLES,AN D BE ARIN G SPRI N G ARRANGE MENTS . 1 07 in thickness (S equalling th e dimension s of the scale of th e

m - - o i e . 2 . . in in . in in in . del), . for . scale 3 or { 61 for 2 scale 1 ,and L in . u th e scale 45 in. thick . If sq are webs are used face width sh o d ul be 1 1 times the diameter of the axl e . Th e crank pin journals should be the same diameter as the b e arin g journals,and the length of pin (width of journal) sh o uld be

1 - S i . n o r e in in in i . 2 , . 5 . or { g . for inch scale,i . for f scale . The ' C d iameter of crank axles at the journals should be 3 S . rank ax les of the built- up variety,the strength of which depends upon

th e r 1 -in brazing,should not be used for models la ger than . scale, e c t u l x ep nder specia circumstances .

— - B o N o E R . V w or THE I . L oc mor vs 1 22. A m PLATE or A Q r BOIL C H A E R P T V I I .

C N E S AN D V S YLI D R ALVE .

BEFORE the buil der can even decide on some of the vital points in th e design of a proposed model locomotive the cylinder bore mu s t be determined,and to accomplish this the reader is referred bac k

to Chapter III .

t l c t h n — i e rs Bri ish o omo ives ave as a rule i side cylinders . . cylinde placed between the frames— and ' a cranked axl e ; and it is obviou s that th e difficul ties of construction are to a large extent increased in a model by this arrangement,especia11y when it is accompanied t he n by valves be ween t cyli ders . Whilst some of the model locomotive designs herewith embody this arrangement,th ose who wish to lessen labour may adopt alte rna t w m tte t th e t n tive ypes ith advantage . In this a r,as in o hers, ques io the maker must decide for himself is,shall th e efficien t working govern the design,or is a scale model the chief object in view d With working models built to scal es of g in . an upwards it is possible to place th e cyl inders together,with th e valve chests abreast but ou tside instead of between th e cylinders,the whole not h exceeding th e width of th e frames . T is system confers two benefits which will be deemed considerable by all wh o will look fi s 1 23 to 1 28 th e first th e into the accompanying g . , being accessi bility of th e valves for repair and setting . Secondly,the eccentrics S n sheaves need no plitting,bei g on the outside of the cranks . Again,this method produces a very smooth running engine,the n th e th e n centre of motion lyi g so near to centre line of e gine .

1 2 m in 1 n ﬁ 3 . Th e des g ( g. ) is arranged for a 52 scale model having

- 5 3 1 in x in . a 35 x 5 . cylinders,steam ports 1 3 3 5 ,and exh ust ports 1 08

: I T D c 1 1 0 THE MODEL LOCOMOTIVE S DESIGN AN onsraucrmN .

Th e passages can all be made with a drill,th e ends being plugged

where necessary . Cylinders of this pattern may be fixed to the main frames by being attached to a cross beam ( or bogie pin casting in a bogie engine) as will be necessary if the ste am chests are of the pattern shown in Fi . 1 24 g . fi 1 24 th e g. ; or methods implied by fi 1 23 m g. may be e ployed,another and a larger example of this type of cylinders

2- in suitable for a . scale locomotive being il lustrated in 1 25 fi . g . It will be seen by the draw ings that th e latter cyl inders and steam chests are in one casting and 2 (or 21) bore by 4 in h e flan e s stroke . T g for fixing the cyl in ders are cast on the sides of th e steam chest,and are suffi c ie n tl y deep to allow of a good joint for the cover find plenty of metal xin t for the fi g bol s . The ports (steam 1 x } in exhaust

1 x } in . ) are of ample proportions, and can be ‘ cast ’ c ih . To fa ilitate m ach ining, th e 1 1 CYLIN DERS AN D VALVE S . 1 cylinders have n o projections on the four ﬁnish ed sides,and the the hole for steam pipe shown on the plan view is not . pro vided for in the patterns,being drilled ( at an angle,it will be n oted) afterwards . The slide valve face of the cylinder is raised, this face being machined with a milling cutter and ﬁnish ed by

s v stuffin craping. The val e spindle g box is a separate casting fi 2 h A 1 l . (see g. 7) and t e va ve is clasped by a buckle s the drawings are very complete the writer may leave this design and a fi p ss on to another example of model inside cylinders ( g. H ere the valve chest may be below or above according - as circumstances dictate,th e drawings showing th e various ways ' 1 1 2 THE MODEL L ocomo rrvs : rf s DESIGN AN D CON STRUCTION .

w ma l Th e h st in hich they y be emp oyed . c ief point of intere th h as I n h is e arrangement of t e steam and exhaust p sages . t e ’ valves below set th e exhaust passage is drilled in the castin g, th e t a ta n t dril h n en r nce to the horizon l hole bei g plugged af er g. A short piece of tube forms th e blast pipe,this being th e only tubing necessary except the steam pipe,which simil arly com e s straight down to th e cyl inder casting without awkward joints o r th e is bends. The passage to steam chest drilled on the same

$ 5 0 4 8

Va ve S in e an V a ve S in e Stufﬁn B ox. l p dl Gl d. l p dl g

Va ve B uck e l l .

— DE T ILS or 2 x 4 I N LI DE R - Fi 1 2 . C RS F O 1 0 I N GE g. 7. A Y N 1 . GAU L TI VE OCOMO .

’ centre line as th e exhaust but with a slight fore and aft rake, bringing it at th e lower end well inside th e wall of th e steam h t Th e th c es . cylinders wi the valves on top render a slightly different arrangement of piping necessary,but th e same general n t e Th e st simplicity is mai ain d . exhau pipe,as will be seen in a h ﬁ 1 3 1 a s . g. ,has to p ss through the te m c est To prevent leakage from one to th e other,the screwed end of the exhaust pipe is

1 1 4 THE MODEL LOCOMOTIVE : I TS DES IGN AN D CON S TRUCTION .

° chased taper,so that if smeared with a little red lead and oil it

t t - t A nu t sc t o will screw up qui e s eam ight . gland rews down on

n ut roﬁl e th e e r the cover at the top. This has a concave p on und side,and with th e countersinking of the hole in top of th e cover,a turn or two of asbestos string -placed into th e recess thus formed w il l h a th e t in complete t e joint . The ste m pipe may enter s eam chest t i 1 34 ll te s h t . w atever posi ion is found most convenient . Fig i ustra

- in - n k in . a larger size of cylinder (for a ﬁ . or g scale engine),the li t h h 1 3 mo ion for w ic . is shown on page 6 . The ﬁrst arrangement of cylin ders with the valves below rende r s valve setting a simple matter it is only necessary to turn engin e upside down and remove the bogie (ii any) and take off the valv e ma chest cover . Not a single pipe is disturbed,and the boiler y

— 29 C LIN DE R S wrrn V LVES B ELOW . S ca e h a f f l size Fi l . u . g. Y A ( l , l l )

n u ﬁt remain in its place . A spri g sho ld be ted on the steam ches t cover to keep th e valves on their faces ; this is not required when th e . ﬁ s 1 2 an the valves are above cylinders For both designs ( g . 9 d

1 3 1 ) only one set of patterns is necessary . Turning to the orthodox types of inside cylinders— copies in a — ﬁ 5 h more or less degree of actual examples g. 1 3 illustrates t e

M r - . in C cylinders designed by Pearce for the g . scale model ale

o 902 - donian locomotive N . (the so called Dunalastair The only drawback in this arrangement wh ere a practical working model is desired,is th e accurate workmanship required and th e inaccessibility of the valves for purposes of setting and other adjustments,to say nothing of th e restriction of cylinder diameter a and steam pass ge area . Th e following notes on th e construction of these cylinders should be of use to th e builder,many of th e processes being the same t whatever design is adop ed . S 1 1 5 CYLIN DERS AN D VALVE .

One pattern will do for th e two cylinder castings,and th e d imensions given below in clude an allowance for shrinkage and m a i 9 L 2 l in . i . . t in n chin ng eng h, 1 . ; depth, 1 g ; valve face,{7} t i 5 in n n . from cen re of cylinder ; side fla ges, . from centre and 5 9 1 th 1 r l i in . n . ick ; the body of cy inder is 1 ?) ; core prints,5 diameter an d in fi . x d h 5 long. A box for the exhaust passage is e on t e side o f d valve face on top of the cylin er where shown on plan . The e n d flan h 3 h ges s ould be 1 3 in . ,and should project beyond t e rest of t 1 a in . p tern 1 5 . for a depth of {gin as shown on section of cylinder Th e fl n i in h th flan top of side a ge s 1 . igher between e end ges than

1 — A S E T or C LI DE R wrrn V LVE B ELOW Fi 30. g. Y N S A S .

th e rest of pattern . This is to bring the line of top bolts above the footplate . u 5 n The cylinder cover patterns sho ld be l i g i . diameter,and 5 3 in . in in . t 3 1; . thick,with a projection of 3 5 on the inside,4 diame er for checking in to cylinder,th e back cover h aving the stufﬁng box

- and slide bar lugs cast on . The steam chest is a plain pattern,the same length and depth 9 i . i h as cylinder pattern,1 3 n wide and g n . t ick all round,having a b stufﬁ n oss at back for valve spindle g box . The cylinder castings sh ould be ﬁrst lined out,the cylinder being plugged at each end with a piece of hard wood and a circle t t . H?in . diame er scribed round in correct posi ion of bore Then place the cyl inder on a surface pl ate and pack it up to get centres at each end true with a scribing block,and th e valve face and 1 1 6 M V : rrs S N AN D N S I N THE MODEL LOCO OTI E DE IG CO TRUCT O .

flan es T side g square with plate . hen set out the lines at top and flan nd n i es a n i e . bottom of g rou d valve face,2 . each s de of c ntre Next turn the cylinder over so that it will rest on the side flanges,and adjust the packing till the centres are again true,and the lines just scribed round are square with the surface plate then set out and scribe the l ine of valve chest

seating gin . from centre of cylinder, and the a 5 in side flanges 4 . from A centre . portion of H end flan es t T the g projec I W 1 in 1 3 . for a depth of S R i fit E g h . to in the D N e I op ning left in the L Y ux li . I C a i ary frame t should be mentioned h ere that an extra in piece about i . by in 1 . must be cut away at end of opening in these frames to clear th e back cylin de r covers, and a slight groove may have to be fil ed out to clear heads of the two screws in cylinder cover that come close to the

frames. The cylinder can now be bored out either by chucking on the face plate or by bolting th e ﬂan Th it to an angle plate by side ges. e latter method will,

1 1 8 M : rf s S GN AN D N S N THE MODEL LOCO OTIVE DE I CO TRUCTIO .

-i l the i n . hole being en arged sideways to the same width as

the port. Th e steam passages can now be drilled out from the flange ends and cu t into 1 in m cylinder 1 3 . fro face of flange the holes coming through to th e face can be fil l ed up with a piece of 1 in . in 1 3 brass soldered . The back cylinder covers can be held in a self - centring chuck for turning the in are H side face . They T IW checked into cylinders S 3 h in . T e R nearly 3 5 E D n N hole for the pisto I rod should be started centrally with a hand

. 3 o e 3 t ol or a square centr for a depth of about 1 in u t e 1 3 . to ens re h ill dr running true . Then fix th e turned face of cover in a boxwood chuck turned up to receive it,and enlarge th e mouth of h 5 in the ole to 1 6 . 5 in diameter and 1 6 . deep to form the stuffin box Th e g . slide bar lugs wh ich project from side of stuffing box sh ould now be

fil ed th th e h h - in up parallel wi ole last bored ; a s ort piece of fi . fil i H round brass could be put in as a guide in ng. oles should N S AN D V E S 1 1 9 CYLI DER ALV .

3 -in e then be drilled through the lugs for 3 1 . bolts or tapp d for screws. Th e front cylinder covers have a recess inside for the nut at the en d of the piston rod,the outside being turned to the section shown . Th e box forming the valve or steam chest should be ﬁl ed in n o r t . h d i planed up to a wid h of 1 ,t e epth being 1 1 . and 2 in 5 hi in . le ngth 1 . ,the t ckness of metal being 1 6 . all round It sh ould be ﬁxed to an angle plate for drilling the holes for valve S th 7 in 3 in pindles ; ese are 3 2 . centres,3 1 . diameter,and counter

5 - d r ll i stu fiin . i ed to 3 1 n. full for g box gland These holes should b e set out and drilled as accurately as possible. This will not be a very difficul t matter if th e casting is fil ed up exactly square an d fixed to the angle plate in correct position for drilling one o f A - in ul be d o the holes. strip of 1 . brass co d bolte n angle p late close up to the sides of casting,and after drillin g one hole, th e casting can be turned over for drilling the other hole instead o f hi hi the s fting angle plate . T s will ensure the holes being same d D istance from sides of casting. rill the hole for steam pipe in the position shown on top,and the holes for screws at each side

a o in - in ﬂan e b ut 1 . deep for 1 . screws for securing the g of steam

ill - in pipe . Dr a hole in centre of front end and tap for a 1 . screw, w hi in ch can be removed when setting slide valves . The cyl ders and steam chest can be bolted to

- gether with four 1 in . bolts with n uts at each end as shown in drawing ;or the holes in steam chest may be drilled and tapped

f or - in i 1 . screws, w th clearing ﬂan e h oles in the g . Four holes

3 - in to ll for 3 1 . screws are be dri ed in each of the cylinder side ﬂanges to correspond with the position

o f holes in frames. Two extra

i 1 34. F g. h oles should be drilled in each

- in fixin flange for 1 . screws for g cylinders to the auxiliary frames, ' the heads of screws being countersunk in th e frames and fil ed ofi fl h us . The cylinder covers are fixed to cylinders with six D N 1 20 THE MODEL LOCOMOTIVE : rrs DESIGN AN CON S TRUCTIO .

-5 W W “ P ,C Y L | N I J E R Y L l N D E R c o v s mxl F RA M E

" E f l d N AL P L A N L P P L A N O F T O P

' ° 7 ' r s: - . 4 k 2 8 ' 3 2

— LI DE F R 5- 1 14 I 3 C R O . S LE DE C L E D I N L Fi 1 5 . M L N g. Y N S 73 CA O A O A RA WAY L TIVE OCOMO .

1 22 THE MODEL LOCOMOTIVE : rrs DES IGN AN D CON S TRUCTION

which h as just previously had its valve adjuste d may be removed, taking ou t th e valve also,and making note of the way it stands on

h t e spindle. other side may then be correctly set,and the r i cylinde last taken down replaced . O course accuracy depends on th e true ﬁtting of the ﬁxing screw clearance holes in the D S 1 23 CYLIN DERS AN VALVE .

ﬂange s of the cylinder casting ; and care should be taken to see h l t at these are not unnecessarily arge.

M 63 1 E . R 2 . E . N N. o . For some designs,notably the . compound , ‘ ’ - R o A . N . utside cylinder engines,and th e tlantic type G . locomotives, ﬁ 1 a saddle (as g. 37) cannot be employed to hide the exhaust pipe,

an ﬁ . 3 4 d therefore the arrangement given in gs 1 9 and 1 0is suggested . The placing of the horizontal connecting passage in the body of th e steam ch est very much simpl iﬁes the piping arrangements,and also a 1 llows of the shortest possible piece of tubing for the blast pipe . A further improvement embodied in this design is in the method o th f facing e cylinders at the steam chest joint. This may be done ul between the centres of the lathe,as the projecting spigot is circ ar. It may be urged that the exhaust passages should not come in

— - r mn E R Fi 1 3 9 FI I E D x 1 1 N . Ou s C LI D . g. . N SH g 1 Y N S

t contact with vessel s holding live steam . This precau ion is very necessary in large work,but is hardly tenable when dealing

with such diminutive engines as model locomotives. The varying temperature of th e live and the exhaust steam is very small,and i ot considering the mass of metal in th e cylinders,there s n likely ff to be much variation in the temperature of th e di erent parts of

the cylin ders and steam chest whilst th e engine is running. I n larger models it is advisable to h ave other means of removing

1 t o con fuse th e l ast The writer h as n oticed th at model engineers are ap t b ’ l ast. i e h th e bl ow r I t is not strictl correct to cal l th e bl ower the b p p wit e . y N 1 24 THE MODEL LOCOMOTIVE : rrs DESIGN AN D CON S TRUCTIO .

1 26 M T : I TS N D N R N THE MODEL LOCO O IVE DESIG AN CO ST UCTIO .

t 5 i - 3 n t n t i . n por s less han 3 1 . in width for gun me al and 1 3 for iro i cyl nders . To render the casing outside the frames for th e covering th e E h e . . e ex aust pip in the L T. S design (see Plat 1 1 m li ﬁ . 4 a cy nders arranged after the manner of g y be adopted .

- h G. R 8 t N . ft T is pa tern is employed in some of the . . singles .

Th e t t i uit 1 - in c e drawing which illus ra es cyl nders s able for 1 . s al locomotive is exactly half full size . The steam chests are placed at an angle to allow the valve face to lie closely to the cylinder, and are quite separate from one another,being served by tw o steam pipes .

C N YLI DER DETAILS .

h v e t Passing on to cylinder details,suc as pistons,val es,glands, c . , with regard to the former,for small locomotives having gun - me tal cylinders of diamete rs up to,say,o n e inch ,the ordinary methods of packin g a grooved piston cannot very well be improved upon— that is,if th e pisto n is sufﬁcientl e Th made y wid . e groo ve h Fi 1 42 also s ould be as deep as possible,and g. . can be packed with asbestos yarn, darning cotton,or lamp wick,laid ﬂat or bent up in the shape o f t m t an inver ed U ,the extre ities in ei her case being sewn togethe r .

s z e n a n

— m S E V E Fi 1 43 . F1 x o LID LV ES T T IR SPI DLE g. A O H N S .

A suggestion for packing small pistons,which woul d appear to ff c ﬁ 1 42 c s o o er good hances of success,is shown in g. ,and onsi ts f winding a piece of clock spring in th e groove of the piston,afte r

n ﬁbr u wards overlayi g ﬂat lamp wick or other o s packing.

t - l Pis on rings are said to be unsuitable for gun metal cy inders . Th ere are several methods of afﬁxing the slide valves to the valve Spindles,and a variety are indicated in the foregoing cylinde r designs and accompanying sketches . The different methods of N S AN D S 1 CYLI DER VALVE . 27

fitting springs behind the valves to keep th em up to th e port faces— a course strongly advised in positions where the valves are to ofi— fi likely fall are to be seen applied in Plate IX . and gs. 1 29 1 3 1 41 , 8,and . Piston valves,as usually fitted to models,allo w no escape for

‘ trapped water . A slide valve will lift,but a solid piston valve cannot,and the Starting of a model locomotive provided with the tt a H la er v lves may often prove troublesome . owever,where a so lid piston valve has no lap or lead,such difﬁcu l ties will not as a e th e rule aris ,as there is no compression stage in stroke . Small models need practically no lap,and if lap equal in amount to one quarter of the width of port in engines up to three - quarter scale is provided,th e engine will be found to work quite sweetly,no i .e t lead ( . port opening when the engine is on dead cen re) being n t necessary . In larger engines the lap should o exceed half the

- 3 - W th in . t e . in . idth of port,viz ,for f g steam por s provide 3 1 lap . The valves for cylinders of th e Dunalastair model on page 1 20 are provided with a large amount of lap,and if an engine were built exactly to drawings it would be found that th e eccentrics would have to be very large to open th e port sufﬁ cientl y,and that

’ th e admission of the steam woul d almost certainly become ‘ late,

‘ after the engine h ad been runn ing a short time,owing to lost motion — the many joints in the link motion, e ach with its necessary working slackness,giving a travel smaller than the drawings indicate . The best remedy for this is to reduce th e lap to half the amount sh own on the drawings,which should prevent loss of power,and ’ th e anh o ance v h t u y of ha ing w a is termed a blind r nning engine . The recesses of the stuffing boxes of model steam engin e cylinders should be as deep as possible,so that a good body of packing may be installed,and sh ould be ﬁtted with short glands so that any binding action on th e rod,d ue to th e unequal screwing t t up of th e s uds,is preven ed,or at least lessened . — For th e same reason viz . ,the liability of binding th e rods or — th e ﬁ 1 3 spindles the use of common screwed glands (see g. 9) is to be deprecated in many cases,and unless th e glands can be accurately screwed and the recesses truly tapped,shou ld not be employed at all . 1 28 THE MODEL LOCOMOTIVE : rrs DES IGN AN D CON S TRUCTION .

’ From an amateur s point of view th e studded gland is easier to a make,and is also more in ccordance with actual prac tice . Where it is desired to do away with a motion plate (see th e design on Plate III . ) dummy glands for the tail end of the valve a Th e difﬁcul t n h i s in spindle are dvisable . y of getti g three ear ng a line precludes the use of dummy glands where a motion plate is to be used,and it should be borne in mind that unless the support of a motion plate or a dummy gland is given to th e valve spindl e,gl ands will constantly be in a leaky condition .

M AN D N S STEA PORT PIPE PROPORTIO .

Owing to the ve ry l ow piston speeds even at the highest rates

N of travel,the ports of model locomotive S P 8 WE F a ws l' ‘ T 1 W engmes need not be so large as a me re ca s reduction of s le would render neces ary . Again ,as the cylinders of the model are much smaller than the scale size,ports may be made less in width and length than 1 1 44 F ' 8 ° at ﬁr h o r st sig t would appear advisable . F model s a good rule is For model s of one inch scal e and smal l er l = l f r in L h a diameter of cylinder x scale of model + 1 5 . WS = 1 th e 1 § of stroke .

: WE 1 of the stroke. = th PB of e stroke. F or l arger model s = L h al f diameter of cylin der .

WS,WE ,and PB as above .

- in h x 1 -in r th e Therefore for a g . scale model wit 1 1 . cylinde s, dimension s would work out as follows

in or i . , ,say,4 n PB = 1 1 = 3 in WS and 1 3 x 1 3 § = = —3 in WE of 1 . 1 1 1 § Steam pipes sh ould have an internal diameter at least about

- one fourth of the diameter of th e pistons ; therefore for L in .

- - in e in . cyl inders 1 . pipe (internal bore) should be employ d,and for 1

1 0 E O M V : I TS E S N AN D N S N 3 TH M DEL LOCO OTI E D IG CO TRUCTIO .

— ‘ ' ’ i 1 4 L D E R s n o m. S OM P O . F . C I o M n mm C U N D g 7 . Y N S Desi b M r ea en n J P. M ( g ed y . d . )

i 1 — L ON D N N D o r - s F 48 . C L D E RS ro n M DE L O A N a n W srn N IL Y g. Y I N O n RA WA ’ ‘ B B COM OUND WE P . N S AN D S 1 3 1 CYLI DER VALVE .

i h W l P . h cyl nder,thence through holes into the L . steam c est i st th is is an ingenious way out of the difficulty,the writer would prefer to leave the jacket space quite free from contact with the exhaust steam,a course which can be easily arranged as shown in ﬁ 1 46 g. .

- W . R A L . N four cylinder compound of the . . Black Prince u in ﬁ 1 4 type may be b ilt having cylinders arranged as shown g. 8,no a difﬁ cul t speci l y of construction arising. The drawing is prepared

- sl i ccent to suit a gin . scale locomotive,and p e ric valve gear is I strongly recommended . f a gear capable of reversing from the

Zz n ff c'o n n ec t ed to

A l? V5

— ‘ ’ Fi 1 49 R I G SH FT F OR M ons r. Wns s COM POUND g. . OCK N A . cab is desired,then the best course will be to follow the prototype, ' P th e L . H P v using J oy s gear on connecting rod, the . . alve obtaining its motion from a rocking lever attached to th e tailed P n end (front) of the L . valve spi dle . As the design stands,a single eccentric outside the cranks (see f 1 6 ul h ﬁ 1 4 ig: 9 ) sho d be attached to a rocking lever as s own in g. 9, P th e uppermost arm working the L . valve and th e lower one th e

. f H P o . P . H . P valve of the cylinder The cranks the and L . cylinders on each side respectively sh ould,of course,be exactly opposite one another,each pair of engines being placed at 90 degrees with each other .

O N C N S CILLATI G YLI DERS .

Small oscillating cylinders as a rule control th e distribution of th e steam without separate slide valves,and as th e vibrations which open an d close the ports are at righ t angles to axis of the

i e. th e cylinder at th e dead points ( . to centre line of the motion work) ,it wil l be seen that no advance in steam admission and exhaust is possible,and therefore oscillating engines sh ould be 1 32 M M V rrs S N AN D N N THE ODEL LOCO OTI E : DE IG CO STRUCTIO .

i h used only for the smallest models. Aga n,as t e steam pressure at certain points in the cycle tends to force the cylinder off the face of the steam- distributing block (no closed steam chest be ing employed) the steam pressure and the size of engine is limited,and

- in ul be models larger than g . scale sho d not provided with such cylin ders.

- The up- hnd- down movement of properly spring borne axles, affect ing the steam distribution of oscillating cylinders,plain bearings

r 7 0 0 y e s P as t o :

CRs S E CT I O N X

C ROS S S s c n o N Y

n 1 50 alo e should be used. Fig . shows single -acting cylinders suit

-in 1 - able for a 1 . or 1 6 in . scal e ﬁ 1 51 model,and g. an arrange ment where the cylinders are inside and have to be placed

between the frames . In th e steam-distributing block ' — I LE - TI Crt mnnns Fi 1 50. S g. NG AC NG 1 S E M DEL o o or' s two holes are necessary one 1 4 11 C L L c n rv . 1 01 1 . A O connected to the boiler and the other to the exhaust pipe in th e chimney,or to a reversing block (see next chapter) where the engine is to run both backwards and forwards. Th e crank pins for single- acting locomotive cylinders should be placed at 1 80 degrees apart, that is,directly opposite to one h anot er.

- Fig . 1 52 illustrates a design for a double acting cylinder the steam block of which renders the engine capable of being reversed from k n the cab. This property,while ma i g it possible to dispense with

' a regulator— as in the mid position of th e lever steam is shut 011

T N N HE MODEL LOCOMOTIVE : I TS DESIGN AN D CO S TRUCTIO .

In setting out the ports and erecting oscillating cylinder models it must be borne in mind that the passage to the cylinder shoul d not in any case allow communication be tween the two ports of the steam block ; thus the space between the latter ports should u l in j st cover the hole in the cy der face . The cylinder should be placed so that the ports are in the central position (when th e

I nco rrect Po r ts m ' M eth o m b l o c k o r k d . S tea m biac/Y P

Fi 1 53 g. .

1 50 the engine is on its dead centre),as shown at S and E in fig. , centre dotted circle representing th e position of the cylin der port. Care sh ould be taken to see th at two faced portions of the cylinder and block are so disposed that the pull of the spring on the pivoting stud ensures perfect contact between th e port faces . This point is provided for in the cylinder by fil ing away one of th e faces coming together at the pivot in such a manner that the bearing is beyond the pivot and farthest away from th e steam h fi 1 50. faces,as s own in the plan, g.

— A C LIN DE R wrrn SLI DE CR N . Fi 1 54. g. Y A K C H A R P T E V I I I .

V G ALVE EARING.

WH ILE many makers of model locomotives have clear ideas upon the subject in general,a complete kn owledge of the action of the l th s ide valve and e design of the required gearing is often lacking. There is hardly a more important feature in the whole engine,and upon the design,manufacture and adjustment of the valves and A valve motion the ultimate success of the machine depends. very slight defect will either render the model less efﬁcien t as a n n — i e m steam e gi e . . it will use more stea than the power developed —or should warrant cause the engine to fail absolutely .

E xh a u s t

Fi 1 g. 56. — Fi 1 55 Tl n SIMPLE D S LI DE V LV E. g. . A

Therefore it behoves the beginner to thoroughly understand the principles governing the action of slide valve, and study the variations in the working of the locomotive that slight differences in the proportions and setting will make . A locomotive slide valve may be lik ened unto a hollow rectangular box with thick walls, one side of which has been removed and th e cavity exposed, section s at right angles to the open side being similar to the letter t D turned on its side. For his reason it is commonly called

the D slide valve . The open side of the valve slides up on the ‘ valve face of the cylinder,which is provided with three ports,the central one 1 35 1 36 THE M D L M V : rrs AN D N S O E LOCO OTI E DES IGN CO TRUCTI ON .

’ exhaust port, the largest in width) being connected to th e 1 atmosphere by the blast pipe, and the others steam ports) A e each with the respective ends of th e cylinder . s the valv moves backwards and forwards in the closed chamber call ed ’ the steam chest, which is placed in communication with th e ’ steam space of the boiler at the driver s will,it alternately Open s ’ and closes each steam port to the steam in the chest,neve r n i I l u der any c rcumstances opening both at the same time. t wi l be seen that the steam passing through the port when it is opened by the valve and entering the cylinder will press on that side o f i n the p ston doing work in propelli g it forward . The piston being, as it were,fastened to the wheel by the crank,connecting rod an d d piston rod . causes the engine to be moved forward or backwar according to the relative positions of these parts,and also to which port is opened . At the same time that the steam chest is Open to the one steam port the other will be in communication,by means of the cavity o f the slide valve,with the large central exhaust port,and th e piston wil l,at the same time as the steam is passing away,be m receding. The importance of providing a free exit for the stea from the cylinder will be evident,and just as much care must be taken in allowing the exit of the steam to take place at the prope r time and in a proper way,as in arranging its admission to th e cylinder. 55 of Fig . 1 shows a valve more suitable for the smaller classes model locomotives in which th e edge of the valve only just covers the steam port,projecting a trifle over the steam port on to th e valve face beyond,to prevent . th e blowing through of steam to the th exhaust cavity as indicated by e arrow . The slide valve is also ill ustrated,turned upside down to show the cavity,and, in the other perspective drawing is shown resting on the valve face of the cylinder with the port nearest to the reader open to fi u steam ( g. The manner in which the exha st passage is h conducted to the outside of t e cylinder casting is also indicated . These remarks and sketches,the write r thinks,explain the elementary difficul ties in the construction and arrangement of the

1 Th e extre mity of th e exh aust pipe in a l ocomotive is al ways cal l ed th e bl ast i p pe .

1 38 THE MODEL LOCOMOTIVE : rrs DESIGN AN D CON S TRUCTION .

n i Th e e hand side of the pisto ,forc ng it to the right. valve is op n P C. to its maximum at this point of the cycle,and th e crank pin . ’ being at the top centre, is in the position when the turning ff lin e ort on the shaft will be greatest. The other end of the cy der, it must be note d,is exhausting any steam remaining in the s D 0 t cylinder from the previou stroke. iagram ( ) shows the exac ly k is e opposite position to diagram (A) . The cran on what is call d ’ in locomotive work its back dead centre,and simultaneously with the movement of the piston th e opening of the right-hand o r back end of the cyl inder to steam,and the exhausting of the steam previously admitted to the left-hand side of the piston will h h commence. The openings of the valve to bot ex aust and steam on each side of the piston respectivel y are shown at th e maximum

1 —A ' Fi 58 . OD s on W I LID LVE RO . M EL R N G ou r S E V P B LEM S g O K A . in diagram which is the opposite position to that depicted in B drawing ( ) . It must be noted that the eccentric leads th e crank,and th e

’ amount of its advance is exactly one quarter of a complete revolution,

i e 90 . . . degrees If a paper or wooden model of the gear be con structed,it will be seen that the valve does not cut off the steam until the end of its stroke,that it does not admit or exhaust until th e stroke has commenced,and also that a comp l ete cyl in derf n l of steam at boiler pressure is employed at each stroke,th e expansive properties

of the steam not being in any way utilised by this valve gear . Postponing for the time being the further investigation of the movements of th e slide valve in relation to the piston and crank, the writer will describe the construction of a valve- gear mo del which enabled him as a beginner to th oroughly graSp the action of the slide valve and to work out various problems in valve gear m N which from time to ti e presented themselves . o miniature locomotive builder should be without one of these models unless h e possesses some arrangemen t which will serve a similar purpose, VALVE GEARING . 1 39 and the excuse that such a model is difﬁcul t to make is uht in this case tenable. 1 The valve gear model consists primarily of a 7 x in . board, which should be planed at least one side,and will be better if it h as two or three cross battens on the back to prevent it a w rping . Th e revolving T-shaped piece of wood should be dry and of hard mate rial,and although an ordinary wood screw passed through a h ole in the wood will serve as a pivot,the bushing of the centre with a piece of brass tube is an improvement . Th e pivot screw should be ﬂush with the revolving T- piece,and be provided with

- o xa th e is a small centre p p e ctly in centre . From th compasses may be used to set out various eccentric throws,angles of

- advance and other points. The point of the T piece should just to uch a large circle which is to be used as the crank-pin path, an d from this point to the centre pivot a line should be marked o n th e T- piece which shall coincide with a horizon tal centre line

to th On T- from end end of e apparatus . the piece a line vertical to the foregoing should also be marked in a manner which will e r nder it indelible. At th e outer end of the board two V strips of ' hard wood should be fixed to the board,and be tween these another piece of hard wood shoul d be truly planed up so that it will slide to and withbu t A ff fro easily,and shake . rod as long and as sti as possible should connect the sliding piece and the revolving T piece,the length being such that when th e T- piece is in th e posi in fi 1 58 tion sketch, g. ,the sliding piece upon which a section of the valve should be marked,is in its central position . The lower of the fixed V - pieces should have the ports marked upon it as also indicated in th e sketch .

' All the variable parts of the model may be arranged to receive cards for the various problems which may from time to time arise,these cards being removed and ﬁl ed for future reference . Indeed there are many possibilities for the improve ment and embellish men t of this model,but th ese will be left

h - to the reader to accomplish . Above t e crank pin circle a conveniently divided line the length of the stroke shoul d be incised on th e board,perpendicular lines being dropped to 1 40 M : rrs S N AN D N S N THE MODEL LOCO OTIVE DE IG CO TRUCTIO . cut the crank pin circle,by the aid of which,for any position

" of the crank,th e position of the piston may be read 011 at a glance . The possession of such a model will allow th e reader to readily study the intermediate happenings not shown in th e four 1 l m diagrams in ﬁg. 57,as we l as to settle the ore important problems of link reversing motion,as will be shown later in this chapter . The steam- engine is rendered much more economical if the admission of live steam from the boiler is cut off at a point in th e stroke earlier than is possible with the simpl e valve ; the steam being imprisoned in the cylinder and forcing the piston along by its expansive action and without further supply . Whil st this method of economising steam cannot be carried very far in a minia ture locomotive,there are many reasons why,in the larger models

‘ especially,an early cut-oﬂ shoul d be em Th e — ff ployed . early cut o and expansion of steam are obtained by a slight addition to th e outer edge of the simple valve . This

Fi 1 59 . g. ’ increase in size is known as lap, because it overlaps the ports when the valve is in mid position (see ﬁ g. and,by the way,involves considerations of vast import th e in design of steam engines . If the model already described is to h and and upon it is drawn the simple valve together with its ports,it will be seen that without altering any other part of th e gear,if lap to the extent oi,say,h alf the width of th e port be added to the valve,n ot onl y will the port opening be reduced bu t th e admission will also ’ be late, and according to th e amount of lap added,will n ot occur until af ter th e crank has passed the dead centre and th e 0 wa n th e . 1 6 n piston is well on its y alo g cylinder Fig. will explai this . Th erefore th e alteration of th e eccentric sheave throw and

t t ﬁrst posi ion on the shaf is required . The step is to give an increased travel h . To arrive at t is,the dimension representing the

m d r amount of lap ust be a ded to the po t opening. In models it t h o e. is generally advisable make th e t row of the eccentric (i. the distance from th e centre of the shaft to the centre of th e eccentric

142 ' THE MODEL LOCOMOTIVE rf s DES IGN AN D cousrsue rron. distance is found by adding the extra advance necessary for the amount of admission (called the lead of the valve) to that already provided for the lap . Therefore,where such an early admission is required the advance of the ecc entric over and above the advance of 90 degrees shoul d equal

L ap lead .

H owever,it will not be found nec e ssary,except in model loco

- motives above 1 1 in . scale,to provide l ead,and even then only 1 in . about 3 1 is required . Th e addition of lap to th e valve and the advance of th e eccentric give to the valve several new duties,which may be enumerated

’ 1 E -oﬂ ( ) arlier cut . 2 ( ) A period in which the steam is imprisoned in the cylinder . 3 An ( ) earlier release or exhaust . (4) Closes the exhaust earlier,and by this means imprisons the remaining steam in the cylinder whilst the piston recedes,

n co givi g a period of mp ression . (5) Where the valve is provided with lead the next admission occurs before the piston commences its stroke,increasing ff the cushioning e ect. For a deeper study of th e effects produced by lap and lead the ’ W n n author must refer the reader to M r. . J . Te na t s handbook on 1 The Sl id e Val ve, and urge the use of th e described model,upon which problems should be worked out,arranging different angles of t n advance with varying amounts of lap . To help in this direc io , however,the writer includes herewith a diagram similar in general ou tline to that on page 1 37 , showing ﬁve relative positions of crank,piston,valve and sheave,at each of which someth ing different is h appening in th e cylinder,and the only instruction that may be given in explanation is that th e beginn er should at ﬁrst only con sider th e action of th e valve on one side during a complete cycle h of operations. This met od will cause less confusion than if an attempt is made to grasp wh at is going on on both sides of the piston at the same moment . Imagine for th e time being that the cylinder is a single - acting one,and when the movements and the

1 The Slide Val ve im l E x lai d i S p y p ne ,pr ce 6d . V G R 1 43 ALVE EA ING . results of the movements of th e valve over the ports for a given e l s side are mast red,the rest wi l be an ea y matter . M any readers may consider some of the foregoing remarks of a character simple to an absurd degree,bu t th e writer fel t it was better f or him to start at the begin ning,assuming that nothing is known of the subject,than to give th e tyro credit for even a slight kn owledge of the slide valve and its functions . Prospective model locomotive builders may perhaps ask, How much lap shall be provided ? In small models this sh ould never be 1 in h . , more t an 3 2 Fi 1 62 g. . and wh ere revers ing gears of a type which do not all ow of an angul ar ad v ance ,1ap cannot be th e v added to val e .

- in I n engines of 1 . sc ale and above, th e lap should be Fi 1 63 g. . a b o u t h a lf the W e width of the port. here a great r amount is given to the valve, th e engine will most likely not start readily— that is,with valve m gear dimensions common to odel locomotives . Whilst in large practice the valve never opens th e steam ports to the ful lest ex tent,it is,however,advisable to allow the valve to uncover the n W whole of the steam port when the engine is ew. here link 1 44 VE : f S N AN D N N THE MODEL LOCOMOTI r s DE IG CO S TRUCTIO . motion is employed the writer generally sets out the motion to v B give an even greater mo ement in full gear. y this means it is possible to arrange the full gear notches on the reversing lever or screw a little closer to the centre one than otherwise wil l be found necessary ;and if at any time,th rough the wear of th e pins,

. c etc ,it is desired to increase the valve . travel,the full gear not hes e may be ext nded . This course will render large sheaves and links imperative,and to make the parts proportionate the eccentric rods should be as lon g as possibl e ; indeed,in reality all this means is that the lin k motion should be made larger than a scale reduction

would admit. A good example of this practice is shown in the valve

- 2 in . motion for ,a small tank loco motive (see Plate which,by the way,was found to work e xcel len tly in practice . The engine could be notched up three

Fi 1 65 points (the next g. . notch to the centre), ’ where it would run with a perfectly regular beat. The increase in the scale of the motion may be judged by th e fact that whereas the scale throw of the eccentrics of a real engin e in of the same type works out to about 1g . ,and the length betwee n the end pins of th e curved link and the length of eccentric rods in to 21 and 81 ins . ,the respective dimensions in the model are H; . ,

1 0 in . 4 in . and 1 Amateur engineers when setting out the link motion of a model locomotive are often at a loss to ﬁx the proper throw of eccentric W sheave n ecessary for a given travel of the valve . here the

1 46 Locouo'rm : n‘ s ES N AN D N S N THE MODEL D IG CO TRUCTIO .

8 ul in ﬁg. 1 6 ,to a scale of half f l size,the maximum movement of th e die blocks being indicated. Taking as an example a valve gear where the dimensions of

v in . s the cur ed link are in . and H re pectively and the required h 9 travel of t e valve say 3 5 ,the problem may be worked out arithmetically thus o w so is E T to VT As y is t . Where y is the distance between the eccentric rod pins, 2: is the working distance of the die in the slot, E T is the required eccentric travel, VT is the valve travel .

‘ The terms of w,y,and E T are known,and the sum is solved thus VT x y E T w 9 x 1 } E T 3 5 Hr n E T 33,or Q i . full. A method which wil l appeal to those practical men to whom the simplest problem in math ematics is a task to be avoided is given ﬁ on the diagram ( g. This diagram may be of any dimensions — twice, four,or ten times full size— and may be applied to the valve - gear model il

1 38 . lustrated on p . The example to be worked out is one where the propor tions of w and y of the link are {L to 1 1, 3 5 or to . Fi 1 69 — SE TTI T E E TR I g. . NG OU CC N C R avin g d ra wn the centre lines a b and C c at right angles to each other as shown,0 being the centre pivot,and C P th e crank pin position , A V G ARIN G 1 V L E E . 47

1 determine the amount of the advance A and at th is distance b l draw the line my parallel to a . The ine must,of course,be on the opposite side of a b to the crank pin ,except in special cases,as,for instance,where a rocking shaft is employed. From the centre 0 mark points E and F,the distance from both points one-hal o the travel o the calms D to the centre 0 being f f f . ivide ' the distance between E and F into three parts (as there are th ree quarter inches in the distance the die block moves in the curved link) . The dimension between the eccentric rod pins being 1 1 in — ﬁve — all the case in point i e. quarter inches that is necessary to ge t the required travel of the eccentric sheave is to add another part to the l ine my,one upward and one downward from points E a d F B li n . This gives points and D on ne wy,th e distance from B C D 0 and being the required throw of the sheave . The action of the link motion may be studied with the aid of the model by drawing on the revolving T- piece or on a piece of card which can be attached to the T- piece,th e lines a b,a:y and C 0 shown in the previous diagram,and also addin g,not regarding what kind of curved link is employed,the points E and F,th e di E C 0 stance and F being,of course,half the travel of the valve. Divide th e my line between points E and F in to as many notches as th e reversing lever contain s,and then the action of the valve may be studied in back gear or fore gear,and also .when the gear ’ is linked up . The changes in the expansion,exhaust,and com pression stages may be observed with out the trouble of making e w h elaborat diagrams. The small circles on the line y s ow the different positions of the lever,and,by means of a movable stud or pin in the eccentric rod,the latter may be inserted in holes

ll T- e di dri ed in the revolving pi ce as in cated by the numbers . Position P shows th e engine in fore gear,the third notch from the in centre,Q, full back gear. The writer would urge his readers to make this addition to the described valve model and note what

1 ’ As l ost motion,due to sl ackness of j oints,gives a l ate port Opening,the l ap may be of th e f ul l est dimensions with same amount of advance,the buil der cutting o ff th e lap if afte r th e engine is buil t th e travel is reduced very much by th e inevitabl e sl ackness or if th e admission occurs at a l ater period than it sh oul d

- 1 d Anoth er wa is to ﬁx th e l a for a in . scal e en ine sa at o. i n r y p, i g y, 9 6 . p o 1 i ad ance f th, Thi of course sh d I n v ding an v o 1 5 s, , oul give lead . practice, h th e l ead wil l be nul l iﬁed b th e aforesaid l o m ti n oweve r, y st o o . 1 48 THE MO O M V f D I N AN D ns'r 'r DEL L CO OTI E : r s E S G co auc mN .

c s e is u O hi ul o cur as the engin linked p. ne t ng sho d strike him forcibly,and that is that th e time of admission is practically not changed for any position of the reversing lever ; but the cu t- off, extent of the expansion period,moments of exhausting,and the commencement of the compression stage,vary widely with different positions of the lever.

Fi 1 0 g. 7 .

Whilst the inventive genius should not be discouraged,th e writer would not advise attempts to put into practice a reversing h M r t . valve gear based upon t is model . The la e David J oy patented a gear 1 in which a single eccentric is moved along the line E F in an ingenious manner,by ﬂuid pressure,but no such arrangement has yet been devised embodying greater advantages than those of the ordin ary l ink motion and Which is capable of being actuated whilst th e engine is running. An arrangement which on small model locomotives gives all th e

1 ’ . R n in L . B S . C . e e l tri d on a . J oy s oil va ve gear e g .

1 50 THE MODEL LOCOMOTIVE : rrs DES IGN AN D CON STRUCTION . referred to th e several drawings depicting this type of valve gear contained within these covers, which wil l,with the sketc hes, 2 1 3 ﬁgs. 1 7 and 7 ,help towards a clear idea of the general ’ arrangements of Stephenson s link reversing gear as applied

to locomotives. 2 Fig. 1 7 gives Val ve t m n t s o n l y an a m o u n t u m a r. the names of c c . 0 1 4 P O M the variou s parts,

and ﬁg. 1 73 shows the gear in the positions a m o u n t “m a t: of full gear for ward,mid gear and full gear

backward . ﬂ maawn o m; x 1' f ro S c at ! The e ar e i . several points with regard to the setting of valves actuated ’ Fi 1 3 — STE PHE N s0N s L I M TI N I N T RE E g. 7 . NK O O H by link motion PO I TI N S O S' which have been found by th e writer to conduce to a good distribution of th e steam,and may be enumerated as follows ( 1 ) E ccentrics shoul d have the proper throw (with l ink gear if they are p rovid ed a l ittl e in excess of the theoretical throw, troubl e with regard to l ost motion,and wear and tear of

' ins and st a s wil l not rese t itsel p r p , p n f ) . (2) The eccentrics must be in the correct positions on the shaft

th M easure the l and have eproper angle of advance . ( ap of the val ves afi er the cylinders are fi nished,in case of variance rom the desi n f g . ) 3 The c ( ) e centric rods must be of exactly the same length . ( The meth od of adj usting eccentric rods at the val ve setting is not a ood one and shou l d in no case be em l o ed g , p y . ) (4) The link should have the right curvature and the die should fit l accurately the s ot. 5 The v d n in ( ) val e spindle must be capable of a justme t length . G ARIN G 1 51 VALVE E .

( Various meth ods are p ossibl e,a screw adj ustme nt being the best . ) (6) The lifting l in ks must al l be of exactly the same length ,and

- bar the arms of . the weigh shaft must lay in the same

O course the wei h - bar sha t itse in rel atixm to plane. ( f g f lf, c u atel the rest of the val ve motion,must be erected a c r y. ) Th e first step to take in the operations of valve setting, supposing that all th e work 1 s finish ed and only requires erecting, is to fix up the crank axle on V blocks on the surface plate (or, in outside cylinder locomotives,with no crank axle to temporarily attach the wheels to th e axle at the right angles to each other), and by the most convenient method set the crank pin on one s 'vert'ie al l s n e ide y. The eccentric havi g a c ntre line produced to their edges (A),it will be then necessary to determine th e a amount of dvance of the J in an sheaves at these points, th e two sheaves lying close together and preventing the setting being done from the centres. Having set the arm of the scribing — m mcs E TT E cc . Fl 1 4. S I G g. 7 N bl ock at th e level of the centre of th e axle- lin e B, drop the point as much as the angle of the eccentrics determines (C),and having the sheaves loose on the axle,turn them until the centre pops on the sheaves at A coincide with the point of th e scriber at the lower level . Then fix the sheaves tightly for the time being,and proceed in the same On th e manner for the other side. erecting the motion,if arms of the weigh bar shaft are in the line with each other,and the lifting

’ links an d the eeeentme q ods of dead l ength,then all that will be required will be to set the valve 1n its proper position on the spindle, i I f giving t an equal opening for both front and back ports. the eccentric advance proves to be too much or too little,then th e sheaves mu st be given smaller or greater advance in proportion,as 1 it is generally found that owing to the angularity of the rods the port opens to lead when it is not intended to,and if additional lap is

1 This is onl so with en d E n ines rovided y gines having open eccentric ro s. g p with crossed rods ive l ess l ead in mid ear g g . ' 1 52 THE MODEL LOCOMOTI VE : 11 s DES IGN AN D CON S TRUCTION .

not desirable,then the advance of the eccentric must be lessen ed . Oi course there is no reason why th e differences in the port open in g which arise in this way should not be taken in to account at th e

- 2 . a t e. in c e E e e . setting of the eccentrics . xc pt in larg models ( s l engines) and locomotives with short eccentric rods,the earlie r ' admission ,due to th e angularity of the rods,is not noticeable an d ’ h o t need not be considered . It is the write r s duty, owever,to point u

th e l n - all probabi ities present in li k reversing gear. ' The weigh - bar sh aft and lifting arms and l inks,if al ready ﬁxe d, must be checked to see that,when the reversing lever is in full forward, backward,or mid gear,the curved links on each side places both links in simil ar positions at the same time this bein g so L ,the valve may be coupled up to the spindle . ater,several devices will be described by which the valve may be moved alo ng to Th e e its spindle adjust its relation with the ports. b st meth ods are those where screw threads are employed at any rate th e valve sh ould not be ﬁxed in the manner common to large

VI Z hi locomotive practice, . , the method in w ch the distance between the centre of the valve and the die block in th e curved links is ﬁxed,adjustment being made by shortening or lengthen ing

th e eccentric rods . The average amateur is sure to come to grief if he adopts this course,especially where th e eccentrics are loose on the axle an d are not ﬁxed by the positive methods already described,as both eccentric rod length and sh eave position have

to be determined at one and th e same time . Whilst the valve setter is ﬁnding th e proper place for the valve on the spindle,means should be provided to temporarily hold the reversing lever (where such is used) in the various positions,the notches not being cut until the last th ing,and to ensure a good ’ distribution of steam and a clear,regul ar beat, the valve should h be set wit the lever in the usual running position . As the motion should be designed to give,when in full gear,a greater port opening than is re quired,plenty of clearance may be allowed between th e die block an d the end of the curved link,and under n o consideration sh ould it be attempted to run th e engine With 1 ﬁxed o the the lever as far as it will g . To ensure the accuracy of

1 Oth erwise th e pins of th e motion wil] be subj ected to sh earing strains and ma fail F or amoun t of cl earan ce e ﬁ 1 8 and Plate I se . 6 . y . g

1 4 : N 5 THE MODEL LOCOMOTIVE rf s DESIGN AN D CON S TRUCTIO . valve can not be ﬁtted with this reversing arrangement,as whe n live steam is admitted to the exhaust port,the val ve wil l be lifte d off H s be of its face. owever,thi can overcome if some method holding the valve down is adopted, but this entails increase d friction of the moving parts . Another arrangement in which a single eccentric may be used,

u d - in th e suitable for small models of n er g . scale,is shown in a ﬁ 1 6. ccompanying illustration, g. 7 N0 lap or lead is allowable,and the eccentric must be either 90 degrees in advance or be hind the crank, according to Whether the top or bottom posi tion of the die block (radius lin k) is to be forward or backward

Fi 1 — A M 5. SI PLE a nnsma . 7 and g gear. The lower position

AB M N GE M E N T‘ the advance of the eccentric gives t w a forward motion to the engine in th e above instance . The hro in of the eccentric is worked out as in the case of l k motion . There is not,however,any great saving of work in this motion,ex d cept for the eccentric,and in larger engines it should not be use . The gear is really a portion of the famous Wal s c h ae rt g e a r shown in ﬁg. 1 78,in which advance of th e valve is obtained by

“ ‘ use of a second series jfi fgxfi gfj rfrf w f o m w wm d of levers, actuated — i 1 A SIM PLE a nnsmc E R . F . 76 g . G A from the piston cross A h modified head . model valve gear w ich may be said to be the Wal sch aert turned the other way about is illustrated in diagram in atical fi . form in g 1 77 . For mechanical reasons the curved link wh ich is pivoted to th e frames at the centre must be shaped as shown,so that the eccentric rod pin doe s not actuate h O n the link w en in mid gear. therwise the curved li k would be forced off its pivot and the valve would,With the lever nearer to the central position,have more travel than in ful l gear,the opposite of what h appens in ordinary link motion or in the valve - gear V V N 1 5 AL E GEARI G . 5

in ﬁ 1 6 u depicted g. 7 . Therefore f ll forward or full backward ea nl g r o y is permissible. By making a cardboard model the author foun d that although the eccentric can not be advanced,lap and lead may be given to th e valve,the necessary advance being obtained by the use of a M h long curved link and short eccentric rod . at ematical accuracy in th e opening of the valve is not attainable,but a gear made as

ul - described sho d be quite suitable for small locomotives up to in . l x scale . The driving ax ebo es in engines having sh ort eccentric d h ul ro s s o d not be provided with very much vertical movement . ’ To set out Wal sch aert s valve gear,consider for the time being th e total travel of the valve only . The eccentric should be placed at 90 degrees to the crank,and arranged to give the maximum port

— A SIM PLE SIN GLE E ccmrr' mc V LVE E R REV ERS I BLE F R M Fi 1 7 . g. 7 A G A O TH E CAB .

n th e opening. The advance depends on the proportio s of vibrating l a l a 2 A D fi the a A B e d . lever ( g. dist nce equalling p + x To obtain a small travel at A B is the diffi cul ty in model work, as the required lead is generally ‘ nil and the amoun t of lap small ; therefore with the relatively large pins necessary it will not be found easy to get points A C close enough . With the design given,this trouble is not present however,the levers are somewhat complicated in construction . An t is fi 1 9 other me hod shown in g. 7 ,where the distance between h the points B and C may be reduced almost to not ing. As the function of the cross - head levers is to control the admission and th e cut- off , a little greater movement than that which th e drawing would dictate shoul d be allowed in practice . ’ J oy s gear may be used with success in model locomotives,an d neglecting the care necessary in th e manufacture of the curved 1 5 6 MO E O I E : I TS SIGN AN D N S N THE D L LOCOM T V DE CO TRUCTIO .

difﬁcul t e t slides,no great y will be encount red . The me hod of e s tting out is rather complicated . Beginners may be inclined to do without levers A and B an d

’ Fi 1 — WAL S CHAE RT S 78 . V L E g. A V GE AR R R E D F OR 4 11 SC LE I ID E A ANG A 2 . A NS C LI DE R L TIVE Y N OCOMO .

’ i 1 80 — SETTING T WAL S CHAE RT S F . . GE R g OU A . M pin lever 0 directly on to th e connecting rod,but they will no t i ﬁ din out h proceed far w thout n g the necessity for t ese levers . n t th e d Their fu c ion is to correct irregular movement of point . C due to the angularity of lever . To give the reader an idea of th e u sual proportions th e writer cannot do better than to pu t th em in tabular form in terms

CHA E R PT IX .

M N D OTIO ETAILS .

THE motion work of an inside - cylinder locomotive having th e valves between th e cyl inders— an arrangemen t common in this country— requires a very great amount of skill and care even in the case of a large model,an d it will not be found possible to obtain sufﬁcient room for really sound working model construction in models smaller than {L in scale,as will be seen from a glance ﬁ 1 83 n d. at g. ,u less the gauge of the railway is widene This ’ drawing is especially arranged for the Dunalastair Caledonian Railway model (Plate and in its details closely follows the prototype. Th e motion plate carries the slide bars and forms a guide for

e d Th e - bar the circular int rme iate valve spindles. weigh shaft is h supported by two plummer blocks attac ed to the frame. The reversing arm of this shaft is cranked to allow of the reversing rod being quite straight and clearing the side of the ﬁrebox as it ﬁ passes to the cab (see g. Owing to the restriction in th e width of the space available for the machinery,which is felt mostly at th e motion plate,the link motion must be of slight proportions,and it will be noticed that the lif ting (or suspension) links are provided with lugs to prevent n the parts jamming each other when the engine is movi g. The eccentric rods are quite straigh t,the necessary set- over being obtained by the forked ends of the rods,which,by the way,are separate pieces riveted ou . Th e intermediate spindl e provides for the further settin g-in of the motion to the centre line of th e valve spindles,and may be 1 58 MOTION DETAILS . S 1 60 THE MODEL LOCOM OTIVE : rf s DESIGN AN D CON TRUCTION .

made by turning up a piece of steel from three centres . The 1 3 drawing (ﬁg. 8 ) shows also an ingenious method of arranging the valve spindle adjustments,it not being possible to accompl ish

a s.

Si e View d .

P N Scal e f s LA . ( ,ul l ize f or Ca e onian mo e l d d l . )

— E E I G on WE I -BAR S FT Fi 1 86. R V RS N . g. GH HA this in the valve chest,the buckle of the valve being permanently d ﬁxed . M to the valve spin le This method was devised by r. W H D b ﬁne C . . earden,the uilder of a very model aledonian t th e h express locomo ive,shown in p otograph on p. The intermediate spindle is recessed to take a circular adjusting

1 62 THE MODEL LOCOMOTIVE : I TS DES IGN AN D CON STRUCTION . rolled brass,rod material was adopted to save case - hardening and grinding,an d to avoid th e use of similar materials of th e same r hardness wearing upon each other . The renewal of the b ass pins is little trouble,and no wear on th e steel parts is probable ;

- thus any subsequent reamering out of th e holes will be saved . The dies are of gun - metal,and th e intermediate valve spindl es of l tool stee . Builders of large engines such as th e one now under considera tion will often ﬁnd it advantageous in the matte r of lining- u p,to arrange the intermediate yal ve - spindle guide quite separate from

ﬁ 1 8 . the motion plate as sh own in g. 7 The eccentric sheaves are large,and are provided with a central

care r

Fi 1 88 — SEPAR ATE g. . Fi 1 — E V U 87 . SEPARATE Gu r I N TE R E DI T LVE G IDE F R S LL g. mns‘ on M A A O M A SPI N DLE S Ha f size for 2-in sca e ocomotive L M TIVE S . ( l . l l . ) OCO O .

rib . This saves space and enables the provision of larger wearing surfaces . The sheaves are cast iron and the straps of best

n un - t ﬁ 1 99 e gineering g me al (see g. ,page As this engine h ad to be completed in a great h urry,most of the parts of th e motion are made of stock bar and rod material with h e . on t e all boss s,lugs,etc ,brazed . The forks of eccentric rods are formed by riveting and brazing on separate pieces as shown in d the detail rawing. To alte r th e position of th e valve with relation to th e spin dle, th e vertical pin in th e intermediate valve spindle,which engages a groove in th e valve spindle,prevents any end movement,allowing it to be rotated only,and to effect th e adjustment th e two lock nutted set- screws should be slackened,and th e nut on the spindle t th th a h w th e l urned wi e sp nner. T is screws or unscre s va ve s pindle in th e buckle,the tapped part of which is made as long I S 1 63 MOTION DETA L . 1 64 THE OD N D N S RU N M EL LOCOMOTIVE : I TS DESIGN A CO T CTIO .

- s ul as possible. To lock the spindles the two set crews sho d be tightened up.

l - in This design of motion is very suitable for engines of 1 to ﬁ . scales also,and within limits can be scaled down to suit the size of h i R . eng ne being built. ound webs for the crank axle are s own However,these can be modiﬁed to save expense in forging (see

ﬁ - g. The crank pins in a square webbed axle may be made i h n . n t 1 in in length i s ead of . ,and the eighth of an inc gained th e h th e may be added to t ickness of webs. A large diameter of cylinders,inside the frames,generally renders the placing of the valve chest either above or be low the li s th t n cy nder inevitable . Wh ere e eccentrics are placed be wee the crank webs,and the centre line of the valve motion coincides with

Fi 1 90 — Dum as or Roomno g. S T V LVE E R Fu HAF A G A . ( ll

size . ) that of the cylinders,a rocking shaft is required to transmit the Fi 1 9 . 8 motion of th e intermediate or guide spindle to the valves . g

- - - l in . shows a fully worked out example ﬁgure for a sca e model . It will be noted th at the eccentric rods being short,they are pinned to the expansion links behind the slot,and the eccentric sheaves,because of the rocking shaft ch anging th e direction of the ° 1 i . 89 valve movements,are placed 1 80 from the usual position . F g is a half full - size general arrangement,and includes the guide 1 90 u - spindle shown full size . Fig. comprises f ll size drawings of link,rocking shaft and bracket.

n l - i n n . A model locomotive to a scale of }i . to the foot with ﬁ cyl inders shoul d prove a powerful engine,and to ensure success a

1 66 THE MOD L I VE rf s E EL OCOMOT : D SIGN AN D CON STRUCTION .

the crank pin,to the required degree . This illustration demon

1 - in . i in strates that for an advance of 3 5 the g n . pin must be . from the axle centre . If on the completion of the model it is found that less advance is advisable,then the pin may be ﬁl ed away until th e best resul ts are obtained,but with careful work

1 94 — TO C LL ron I N ID E — . S P R i 1 95 S EAV E F . H F OR Fig. O A S g. LI N DE R L ocomorl vn w rrn -I N S LE E I CY i . CA NG NE . nc 'r TI a e Dm M . P t I V O ON ( l . ) manship and design no such an adjustment shoul d be found — at n necessary least when the e gine is quite new . ‘ By arranging th e pin in th e cerxtre line of the eccentric, the valves are very easily set by ﬁxing th e ﬂat face of the stop collar at righ t angles to the crank pin and adjusting the valve on th e spindle to give an equal port opening on either side . Very often, with inside - cylinder engines especially,the pro

— E m c F - N E i . 1 6 GENE AL RR E T or S L MODEL F 9 . R E ccn m s OR I g A ANG M N g . CA ie s aken ookin f rom th e eft -h n nd of h e crank ax e (Plate (V w t l g l a d e t l . ) vision of a separate stop collar is impossible owing to lack of space,and a plate attached to a crank web has to be substitute d . fi 1 94. e This may be arranged as shown on the sketch, g. Wh re a rocking shaft and inside cyl inders are employed,the pin in the eccentric must be placed in a position 90° behind the centre line of its greatest eccentricity,and th e stop plate shifted through an arc of similar degree,owing to the practical consideration of fi fixing the plate to the crank webs (see g. 1 MOTION DETAI LS . 67

The accompanying photograph shows this arrangement 1n actual fact,and represents th e wheels,crank- axle eccentrics,straps and connecting rods for a design,much the same as that given on t Pla e III . ,a rocking shaft being used to transmit the motion to th e valves,which are in the design mentioned placed above the li s cy nder . E ccentric sheaves may be made with a central rib instead of

— - Fi l 9 W E E L XL E AN D M TI F OR 1 N . SCALE MODEL T N g. 7 . H S,A O ON A 2 A K L C M TIV E O O O . outer ﬂanges,as shown on th e accompanying detail drawing of th e

- n t t sheaves,straps,and rods for a 2 i . scale ank engine (Pla e

l — - w t n ut The sheaves are ﬁxed by a sing e i in . set screw i h lock

h - c placed in t e cored out spa es in the sheave. Th e straps are of gun- metal,and have a slot milled out in th e end to take th e rod,which is riveted in place with tw o brass pins,

r or countersunk screws,riveted ove . ‘ ’ 3 - 1 8 th e t th e in . C Fig. 9 shows s raps for scale aledonian loco Th are m r E . L . e otive as designed by M . Pearce . sheaves provided with two ou tside flanges, but sufficien t width of strap for th e 1 8 HE L 6 T MODEL ocomon vm: rrs DES IGN AN D CON S TRUCTION . secure connection of the ecce ntric rods is obtained by allowing fl the straps to partly extend over th e anges. The length of rod is adjus table ;however,the writer would advise a permanent fixing

after the dead length,accord ing to th e drawing,h as been arrived at. The method of constructing the sheaves is one which de E h serves attention . ac pair of sheaves is intended to be cast in one piece,cut in two on th e line A B,and joined again preparatory to the ﬁnal machin ing by two screws hav ing their heads recessed in th e ﬁxed casting . The sheaves are by a single grub screw

T . L . . . R shown The . S design shows the eccentric rods ﬁxed in accordance with th e usual locomotive practice,a T - end being employed,facing on th e strap,and connection made by two studs or screws . Instead of a forked end to th e rod th e links are attach ed to

- a plain eye,which should be case hardened . Owing to there being

1 0 MOD M VE 1‘ s E N AN D N S N 7 THE EL LOCO OTI : 1 D S IG CO TRUCTIO . plenty of room laterally,the straps are not recessed to cover the flan es th e A two g of sheaves as in the previous example . thicker curved link is required where a forked end is not used,and this ffi to some extent increases the di cul ties of making th e link . The photograph of the valve motion of a small model shows anoth er method of making the eccentric straps,viz out of steel fi 1 1 t plate in the same form as shown in g. 9 page and withou s ul th e any means of adju tment . It is doubtf whether saving of Splitting the straps is not co unterbalanced by the fitting of the extra plates to the single -fianged sheaves employed in this example . This photograph is really inserted to warn th e reader against securing the rods to th e curved link by a screw on one side of th e h A n link,this screw working a plain hole in t e rod . s a certai amount of play is necessary between the parts, link motion buil t up in this manner will be found to be very liable to twistin g it strains,and soon become much out of line in s movements. The weigh- bar shaft is in this case supported on two bearings attache d to th e footplates,and a single arm is employed for lifting the is n links. This a very good method in small engines,but the pi s h and t e bearings in all cases should be as long as possible .

SPIN C S S A S VALVE DLE RO HE D .

th e t h 2- n The details of mo ion for t e in . scale design give on

Plate 1 . depict a very good meth od of attach ing the intermediate spindl e to th e valve spindle,by which the adjustment of the o t position . i the valve on the spindle is rendered qui e a simple A m n w matter . si pler form,suitable for a smaller engi e hich does l fi 202 th e not employ a separate guide spind e,is shown in g. , one set- screw working in the grooved rod and the oth er locking it in position when the correct setting h as been accomplished . The photograph last referred to illustrate s another arrangement by which a set- screw locks th e valve spindle in any position to which fi 2 t it may be moved, g. 03 being a modification of the same at ach

- C ment designed for an inside cylinder engine of the aledonian type . 2 05 e . Fig . is a further method of attaining the same obj ct I t goes without saying that the screw adjustments are prefer MOTION DETAI LS . 1 2 MODEL M I V : I TS S N AN D N S N 7 THE LOCO OT E DE IG CO TRUCTIO .

able to any other,as small movements at a time are possible and a i higher degree of accuracy of setting read ly obtainable .

- T h . . w t L R . e l ih . n t t o For . scale S desig on Pla e VIII , e u methods are qually to be recommended . The device ill strate d on the general arrangements requires th e cutting of a righ t- h an d an d left- hand screw thread of ﬁne pitch in the crosshead end and the

valve spindle end of the intermediate or guide spindle . Th e cross heads and valve spindles are respectivelyscrewedwith right and left hand threads and have locking nuts,and th e guide spindle is ﬁl ed

Fi . 202 Fi . 203 g . g .

Fi 204. g.

I TE RM E DI TE V LVE PI DL i 205 S E F . . N A A N S. g

to a hexagon shape at its forward extremity to take a spanner . To adjust the valve on the spindle,the buckle being permanently ﬁxed,the aforesaid locking nuts should be slackened,and the intermediate valve spindle turned round one way or th e other, according to whether it is required to lengthen or reduce the distance between the centre of th e die of the curved link and the centre of the valve,the locking nuts making all fast after th e fi 20 . t 4 setting operations The detail herewi h ( g. ) is an embellish ment of the idea,the object being to strengthen the joint between the guide spindle and the crossh ead,and to avoid th e use of right

- Th and left handed threads . e shank of the crosshead should be

1 4 MO TS D SIG D N 7 THE DEL LOCOMOTIVE : I E N AN CON STRUCTIO .

without a thread for some distance,and exactly ﬁt a plain hole in

the guide spindle,the hole lower down being tapped Wh itworth . 3 i n 2 B . A. The valve spindle being 1 3 . diameter,may be tapped No . . The difference of th e pitches of these threads will create a diff er ence in th e distances be tween th e centre of die and valve,if the intermediate spindle is rotated,the arrangement being capable of ﬁne u very adj stment indeed . The lock nut on the valve spindle would alone securely prevent the intermediate guide spindle from ' revolving after the setting had been accomplished,but as an additional safeguard a set- screw is sh own ﬁtted to the crosshead dl e end of the guide spin .

M N S OTIO PLATE .

The function of the motion plate is to support the slide bars,val ve guide spindle,and other parts of the motion of a locomotive engine . One of the simplest form consists of a plain bar stretch ing transversely from frame to frame,and may be made as shown ﬁ 20 in g. 7 . In more elaborate engines with inside cylinders,the accom ﬁ f panying illus tration ( g. which depicts the motion plate or th e model Caledonian locomotive (Plate will give an idea of the sort of casting th at is required where four slide bars for each cylinder are to be supported and the valves are situated h between t e cylinders.

h 2- 08 t e in . Fig. 2 is a detail of the motion plate for scale engine already referred to in th is chapter,and clearly shows the extension carrying th e slide bars,th ese and the intermediate valve

- spindles being cross h atched as if in section. For outside- cylinder engines it is only necessary to support the valve S pindles,and th e motion plate,apart from this,is employed t th m 21 1 only as a means of s reng ening the main fra es . Fig.

- i L T 1 n . R t . shows the mo ion plate for the model scale . S . engine (Plate VIII) ,th e valve S pindle guides being separate cast a i 21 2 t . ings and th e mo ion plate m de out of sheet material F g. is

r - in n another form suitable f o a g . scale,usi g a Bissel bogie or single l truck leading and outside cylinders. The p ate,with guides and brackets,is in one casting.

1 7 6 THE MODEL LOCOMOTIVE : I TS DES IGN AN D CON STRUCTION .

Outside - cylinder engines are as a rul e provided with two motion plates,one outside and one inside,although, as h as been hinted,the latter can be dispensed with,and the valve S d h ﬁ 1 88 m pin le supported eit er by a bracket ( g. ) from . the fra es, use or by the of a tailed spindle and dummy gland . The outside motion pl ate should for a two - bar suspension be ﬁ arranged someth ing like in the accompanying sketch ( g. this example being intended for manufacture from plate material .

C T I R AS ON.

The writer,in single - bar outside - cylinder engines,generally uses a bracket which serves bo th to support the footpl ates and the single slide - bar ; th e bracket may either be a casting or bent ﬁ up out of bar material (see g.

C SS S AN D S I BARS RO HEAD L DE .

The design of crossheads depends almost entirely upon the arrangement and shape of the slide bars,and also the form of the little

en d of the connecting rods . Where the ordinary single bar placed on

V D S N 1 7 8 THE MODEL LOCOMOTI E : rrs DE SIGN AN CON TRUCTIO .

ﬁ 2 21 8 A o s. 1 head as shown in g 7 and . very simple m del of a single- bar crosshead may be made by adopting the device show n ﬁ 21 5 n th e in g. ,supports for the end of the rods formi g slide bar n l n not bei g absolute y necessary in ti y engines .

— - T RT E R IL Y Cnossnm n i 2 2 N SCALE R E N . F . 2 A 1 g . 2 . G A O H N RA WA

fi s 21 9 222 and 223 t two t o f The sketches, g . , ,illustra e ypes two - bar crossheads,one for where the forked little end is used th d and _th,e o er for eyed en s . h x G W E . t and The . . employ the former me od very e tensively, th e latter is more or less a copy of th e crosshead used on th e h G R ft. . N . . t e 8 singles . In former (l -inch example the gudgeon pin is fi xed in th e little end, and th erefore oscillates in th e crosshead,and in h R e . N th e n t G . . example gudgeo pin is fixed in th e crossh ead,being tapped into one cheek of th is fi n tti g. From a model making point of view th e adoption o f Fi — - R . 223 A TWO B AB C OSS H E AI ) g . . R N . G . t th e . ype of crosshead means that either the recess in th e crosshead must be carefully cored out,or milled out (this,however,would not be altogether satis factory),or th e crosshead may be built up as indicated in th e sketch,suitable pieces of steel being first pinned together and th e n brazed up as shown . With the two and four - bar slide bar arrangemen ts th e motio n plate need not be attached righ t at the back end of th e bars,bu t may be placed nearer the centre,this method allowing of a greate r l length of eccentric rod and link motion of amp er dimensions .

21 6 l - . in h v Fig i lustrates the crosshead for a g . scale model a ing M OTION DETAILS 1 80 MO M : 11 ‘ s SIGN AN D N S R N THE DEL LOCO OTIVE DE CO T UCTIO . four slide bars,the crossh eads and slide- blocks being of one piece the e rt a e of metal instead of in separat pa s usu l to larger practic .

C N N N AN D COU P IN G R n O ECTI G L o s. Whilst connecting rods for working model l ocomotives general ly resolve themselves in to modiﬁcations of th e marine type,a drawing of the orthodox strap - ende d rod , which is almost universally used by E nglish engineers for inside - cylinder l ocomotives, is t th ﬁ t i illus rated herewi (see g. The connec ing rod forging s lightened at the big end by the circular piercing,and th e

" o u t a/ I x 6X6 5 /é e 1

— - Fi 226 CONN ECTING Ron F OR l O I N . GE L TIVE g. . i GAU OCOMO . brasses are attach ed by a strap which contains th e oil cup an d holds the cotter,the strap being afﬁ xed by two well - ﬁtting

turned bolts. The use of a cotter in a model big end not being imperative, as adj ustment for wear and tear is necessary only at prolonged

ma t - intervals,this portion y be omi ted . As no set screws for 2 securing the cotter are shown in ﬁg. 24,the cotter (ii used) t sho uld be of very sligh t aper. ‘ On some railways a form of marine big end is employed,and

h a - th e modification of t is making it suit ble for a Zin . scale model t n t fi 228 . is shown in g. S ill simpler arra gemen s are illustrated in fi 226 and 227 th e t c to gs. , la ter conne ting rod being designed be a

- single casting in gun metal . Ph osphor bronze and German silver may be mentioned as very suitable material s for connecting rods, the former more especially for inside - cylindered engines and

G t f r - erman silver in place of s eel o outside cylinder locomotives . Th h as a st u e latter the appear nce of eel,and does not r st .

M N S 1 83 OTIO DETAIL .

i 1 0 types of locomotives connect ng rods are frequently ft. in length . Other dimensions may be obtained from the examples shown,which are all drawn more or less to scale . I section are generally slightly larger in width and depth of section than plain " rods,and for a given weight of metal are of course much stronger .

1 — 0U 1> L 1 N o on E N DS Fi 23 0 R . g. .

— - SCALE LE D I SI X - COU PLED E xp anss Fi . OU IN R 1 N C . 3 PL G F O g 2 2 C 2 . A ON AN TIVE L OCOMO .

COU P L I N G R o n

i 2 — Coue o on F OR - I H SCALE o F . 33 . m r n . co r g R g TANK L o v .

Coupling rods ﬁtted to engines h aving cylinders placed between the frames,are as a rul e attached to crank pins which are given slightly less throw than th e main crank pins,and it is now th e practice to almost exclusively employ solid ﬂushed e nds instead of

Split brasses . M s ﬁtted t d odern engine are also generally with I sec ion ro s .

3 3 232 c f ~ Figs . 2 and show respectively oupling rods for a our 1 84 THE MODEL LOCOM OTIVE : I TS DESIGN AN D CON STRUCTION .

ore coupled express and six ( or more) coupled engines. Where m th an four wheels are coupl ed,to allow the up- and- down of th e axl eboxes,each section of coupling rod must be sepa rate fro m the oth er and connected by a pivoted joint. For small models th e brass bushes and ﬁuting may be omitte d ,

p m — — Fi . 3 2 4. Cournmo Fi 23 5 Cournmo Ron E N D ron g Ron E N D ron g. . ‘ ’ - N G E . OD G. T NTI E T V M EL . A LA 1 0 I N U G L M I R. C . . 1 A OCO O

- fi M - wh o and the ends case hardened (see g. odel makers fi 2 u . 1 favo r th e use of plate material may use ends as shown in g 3 . V th e G N R A t . In model . . . tlantic locomotive design (Pla e ) th e forward end of th e coupling rods having to be of very small width in plan,to clear the connecting rod,the construction shown fi 234 th in g. h as been adopted,it being impossible to copy e be arrangement used in the prototype . The crank pin should hardened,and the pin which secures the rod from falling o ff d atten ed to at inte rvals and renewed if necessary.

2- i . 3 n Fig 2 5 is a detail for a coupling rod for a model . scale

- u l ﬁts th e front co p ed tank locomotive . It has brass bushes,and orthodox crank pin having an inside collar to keep the rod away from th e wheel and a screwed securing collar -on the outside .

(Co ve r 1; lid

S E C T !0 u

P EA N

3 6 — DE R ns oxn F OR - I N L i 2 . TE Axn s . SCALE TIVE F . g N Q OCOMO .

N 1 86 THE MODEL LOCOM OTIVE : I TS DE SIGN AN D CON STRUCTIO . knife edges as shown in th e sketch,and the boiler ends turned to a d s diameter slightly larger than th e bore of the tube . The two en shoul d then be ﬁtted on to the central stay,one being per manently ﬁ xed before placing in th e tube,th e nut b being used to

p Za / e

— — m E R T U B E 3 . 1 B OILER E N DS . Fi . 241 . F1 x o W T . Figs. 23 7 and 2 8 F1 x N o g A

Fi 242 g. . D -T B E B O I LE — - R . Fi . 23 9 . FI I HE D B I L E R wrrn SPU N OV ER E NDS g N S O . U

Fi 240 — P1xmo B OILER E D g . N S

Th the t jam th e ends in the barrel . e centres in s ay being pre served,th e whole may be put in the lathe and the boiler barrel

spun over the ends with a smooth tool. The parts should be tinned with solder,when a final sweating will result in a boiler h u whic will never fail n der ordinary usage . Instead of making the boiler shell with knife edges,three screwed OIL R N S N B E CO TRUCTIO . 1 87 pins may be " let in a little way from the edges at each end so that they project and form a support for th e boiler end during th e subsequent operation of spinning over the barrel . Where cast flanged ends are employed such as are shown in fi 24 3 i g. 7,and the barrel is under inches in d ameter,no stay is necessary,and to prevent the ends from parting from the barrel rivets or screws (brass) can be used . To determine the size of the rivets or screws securing a boiler end,the shearing strength,multiplied by at least six (factor of l A safety) shou d balance the total pressure on the ends . s an in th e st example,say the end is 3 . diameter and working eam 5 l b r in 0 e s . . pressure . p q ,and taking the shearing strength of

l . i b s n . hard brass at . per q ,then l h t 6 0 N . x 5 . x area of boiler end o of rive s x shearing strength of

one rivet. 6 x 50x area of end No . of rivets sh earm h i g strengt of one r vet. 1 2 - - in Now the cross sectional area of an . brass pin is 1 000

to l . in sq . , and therefore the force required shear it wi l be 1 2 1 0000 1 2 l b x 0 . ,and the sum works out as follows 1 000 1 6 x 50 x 7 3 5 — _ l ‘ No. 7 1 . of rivets 1 ivets,or rivets at é in pitch . 1 20 2 However,if the boil er can have the edges of the tube spun over the ends in the manner already described,a fewer number may be 6 used,as the large factor of safety of in this case is not needed . Where water tubes are employed to increase the evaporative power of a boiler,the methods of ﬁxing th e tubes will have to be carefully considered . Undoubtedly the best means of putting together a water - tube boiler more especially,is to braze or silver t t n solder the whole of the join s . The former sys em of jointi g consists of soldering with a species of brass solder which fuses at nearly the same tempe rature at wh ich the work to be operated h u upon will melt. There are, owever,vario s grades of brazing ’ spelte r, but even the kind th at has the lowest melting point wil l not prove so easy of manipulation as th e amateur wo uld " wish,and therefore the next step nearer to the use of soft ( or 1 88 MO M V E : rf s SIGN AN D N S C N THE DEL LOCO OTI DE CO TRU TIO .

pewter) solder is to adopt the method of jointing known as silver l ’ so dering. ° sol der mel ts t e 1 200 Silver . at an average emp rature of about ’ u n at o Fahr . , hard spelter f si g about and the joint f rmed, except that it can be seen against the brass or copper work upon which it is used,will be found quite as strong as the surrounding ’ t l n t h h me a . This ca not be said of soft ( inman s) solder,w ic melts 3 0° 0 ° at from 6 to 5 0 Fahr . ,and which is always liable to run if th il e bo er is allowed to become short of water. Silver solder is,therefore,a useful all - round material,and if facilities in th e way of a sufﬁcientl y powerful blow- lamp o r gas blowpipe preclude its use on larger work,all small pipes,etc

should be so jointed . The flux used is borax,and after soldering,the work may be a h cle ned by dipping a diluted solution of sulp uric acid . Whilst it is always advised to fix th e water tubes ot fia small boiler by silver 1 ’ solder in preference to any other method, the en ds of a Smithie s affixed wa 1 8 fi s boiler may be in the y described on page 6 and in g . 239 and 240,and soft solder used to sweat th e joint,the stl 'ver sol de ed work ein done rst b r b g fi . The boiler barrel should be uried in coke to allow it to retain the heat,and the flame of th e lamp h h k s ould be directed toward the more massive portions of t e wor . Should it not be possible to use silver solder at al l ,th en th e h fi 241 tubes may be burred over on t e inside as shown in g. and the h joint well sweated Wit soft solder . A type of boiler which th e writer experimented with some years ’ ago,suitable for very small scale models in which th e Smithie s

W it is fi . 24 boiler ith s double tube is not advisable, depicted in g 3 . A larger water and flue space than in the kind j ust mentioned may be provided,and although the boiler may n ot be so strong and there may be greater losses by radiation,no diffi cul ties should be occasioned in the matter of the steaming qualities of the generator

- h if small bore cylinders and super eating are employed . Th e thickness of th e shell of th e boiler illustrated should be 1 no t 25 l b in s . 9 3 . and the working pres ure should exceed The continuous crown sheet may have th e water tubes silver- soldered in

. 1 Th e j oints o f th e water- tube boil e r wil l al ways mel t befo re a properl y ‘ ’ v r en d ﬁtte d an d spun o e .

1 0 TH 9 E MODEL LOCOMOTIVE : I TS DESIGN AN D CON STRUCTION .

h o outer shell at t e front end (fig. 244) and fitting a cast smokeb x front,which should not be permanently fixed When the engin e is

completed . The back of the smokebox is fil l ed by a plate,also fi 244 B shown in g. ( ) ,a flanged bottom plate (0) ensuring an air i Th — — a e t ght smokebox . e inner barrel the boiler proper is att ch d to outer sh ell by a short stud fitted with a nut in th e space inside

The u l u the dummy dome . reg ator is a plain pl g cock,and is intended to be actuate d by the smokebox door handle, this having a square eye hole, th e wh eel locking it in h o f position . T is type regulator has been found very convenient for tiny models,and as the type R h E . t e N. o . Fi 244 f cab used in g. . loco motives creates dith cu l ties in th e way of manipulating ﬁttings,the heterodox method of arranging the regulator shown in this design is in some measure excusable . The ﬁrebox is very long,and a sl ot must be cut in the sides to allow

to m the trailing axle pass. The stea pipe also must be bent to clear the blast pipe . If a piece of tube is used for the outer shell, then the sides of the ﬁrebox will require adding to,in the methods A to be shown hereafter . s the model is intended to be as nearly

9 - in t 2 . as possible to scale,the outer shell is 1 g diame er and inner

m - one 1 2in ;h owever,in other designs of locomotive s to é in . scale,

1 - - . 2 t . boilers having 22in outer and in . inner barrels are ob ainable ’ L h - in l arger Smit ie s type boilers s uitable for g . scale model oco motives are illustrated in the designs described on pages 254 to 260.

- W G . E . In the six wheeled . type tank locomotive a T downcomer is

‘ ’ W M E th e t- . u employed, hilst in . compo nd and fron coupled tank locomotive designs,cast downcomers are advised . Th e boiler of th e front - coupled engine is the better of the two last mentioned,although the heating surface is nominally less,five water tubes being employed in place of seven in the M idland locomotive,the increased room in the firebox,the provision of a hole BOI R N S N 1 9 1 LE CO TRUCTIO . in the downcomer and a corresponding opening in the backplate, smaller n umber of water tubes,and the slightly increase d outer h fire barrel,improving t e ventilation of the . ’ I t wil l be noticed that in the smaller designs for Smithie s type boilers the cast downcomer of square shape has been as a rule sub t stitute d for an arrangement of down tube s. The reason for his is w t ofold . The cast downcomer was designed by the writer as a very ready means of firml y securing to the barrel of th e boiler,by rivets (or screws) and sof t solder,a solid fitting with few joints, to provide a large body of water at the lower ends of the water tubes for ensuring a go od circ ulation and no likelihood of dry tubes, and to allow th e tubes to be easily screwed into the downcomer .

— — omm. om zn. ﬁ 246 TE E D owxc Fi 245 CA8 T D owxc . . g. . g

I t h as certainly accomplished these requirements in practice,but in the smaller sizes of model locomotives it is found that unless a hole is cored in the downcomers as shown on the sketch,the draught and th erefore the ventilation of the fire,is considerabl y retarded, and steam raising without the use of auxiliary fittings or opening m d Oi of the smokebox door occupies a longer ti e than it shoul . course th e hole in the downcomer sh ould correspond with an open ing in the back plate,as already referred to,a movable door being t fitte d to th e la te r in a convenient manner . Such a fireh ol e and door is a simple matter with a downcomer built up of tubes,and the latter also may be made to take up less h An ma room in t e firebox. inverted T downcomer y be more easily silver- soldered into the barrel,that is,if the joints of the

- plugs and tubes are also silver soldered or brazed . Otherwise,the downcomer may be screwed into th e barrel with a ﬁne th read,and N 1 92 THE MODEL LOCOMOTIVE : rrs DESIGN AN D CON STRUCTIO .

t ’ d A subsequently sweated with inman s sol er. cast downcomer requires a little more skill and larger appliances to satisfactorily silver - solder or braze on to the boiler barrel,especial ly in the case

- of a gin. scale model. The value of the cast downcomer is seen in boilers for engines

d o w n t o m a r s nom n g d o o r

f u e l f o u r M I bu m ar:

— - - . G U GE M DE L . Fi 24 A G m. . A W TE R TUB B L R F OR g 7 . A E OI E i A O

4 t o . 2 of larger scales . Fig 7 is a design by the wri er for a b iler for an old model locomotive in which the original locomotive type sufﬁcientl boiler was not y powerful . The model,a four-coupled six- wheeled express,was provided with x a very sh ort coupled wheel - base,and instead of having a ﬁrebo 5 in at least 9 x 4 . outside, and 600

s in . q . of heating surface,had only a 6 x 5 ﬁrebox and a total heating sur 8 — TTI UT TH E Tu nas or LARG E Fi . 24 S E g . NG O A f 28 s in face O 4 q. , n- B B E WATE TU E OIL R. As an extens1 on

' of the ﬁrebox would have entailed a great deal of alteration in the structure of the model,a water- tube boiler worked by oil fuel u was u (Primus b rners) s ggested . 5 22 in The boiler proper measures x . and the outer sh el l Th 3 -in h in e . t 71} . former is of 3 2 ick copper,and th e latter

1 4 MO M : 11‘ s SIGN N S N 9 THE DEL LOCO OTIVE DE AND CO TRUCTIO . water- tube boiler to the model locomotive,attention may now be directed to the modelling of the type of steam generator in un1versal use for locomotive purposes,from which it earns its t th e and t name . Wi h general reference to merits demeri s of the loco boil er for models,it may be said that small er engines

- n (models of gi . scale and under) will do very much better with a water- tube boiler than with an ordinary ﬁre- tube boiler, more

Fi 250 — A M L - B . SI PLE T PE ILE R g . OCO Y O .

1 — Fi 25 A SI LE FL E OI I W TE R B E . . U B LER T TU g . NG W H A S especially in th e hands of a novice, and when ﬁred with methylated spirit Wick lamp. For larger engines the w ater - tube generator wil l of necessity have to be more complicated in construction,and although a properly designed boiler of this type will have less heating surface than a

- r loco type boiler,the value of the heating surface will be highe . But wh en ever th e engine is to be ridden upon and sufﬁ cient grate

-ﬁ d v i area is obtainable . a coal re locomoti e boil er w ll prove superior

- to any of the previously described water tube generators . fi 25 0 The accompanying g. shows what may be considered as the simplest possible form of locomotive boiler,th e most important modification being that instead of it h aving a large numbe r of small diameter flue tubes passing th rough the barrel,it is provided OI N N 1 95 B LER CO STRUCTIO .

N with one big tube onl y. 0 great results must be expected from such a model boiler without the use of wate r tubes,and even then t the power of the boiler is very small indeed . Simplicity is ob ained efficienc flue at the cost of y. The single ,as well as providing little heating surface,all ows a l arge amo unt of the gases of combustion to escape without giving up the heat contained therein,the central fl core not coming in contact with the walls of the ue . An alteration which will render a single -fiue boiler more power ful co fi in flu e nsists of tt g cross water tubes to the e . (Wat r tubes

Fi 2 2 5 . g. in the ﬁrebox improve most model boilers,and th erefore may be

t . s see ﬁ 52 left out of the question for the momen ) Thi course ( gs. 2 and 253 ) is open to the serious objection that the boiler must be pul l ed to pieces if the joints (A) at any time fail,and leakage is certain to occur sooner or later if the tubes are only soft- soldered ﬂue into the .

A n -in further improvement suitable in e gines up to i . scale,is the u se of D or O shaped ﬂue having a number of small vertical water 2 ﬁ . 53 tubes as shown in g . The water tubes not only increase heating surface but break up the central core of heated gases which woul d otherwise be wasted up the chimney . Another method is to arrange water tubes running upwards from the front to the 1 9 r 6 THE MODEL LOCOMOTIVE : rs DES IGN AND CON S TRUCTION .

' crown at the firebox end of th e flue,or into the back end of th e firebox crown if flue and firebox are buil t up before they are placed h into the shell . The tubes s ould not be inclined from right

to left,for obvious reasons. None of the foregoing designs should ’ be in any way over-cylindered,and except that an efficien t supe r heater pipe is easily arranged and the draught is naturally a little freer,th e greater number of joints,inherent weakness of the D- flue and smaller heating s urface,all detract from the few advantages to be gained by the employment of any of the various forms of single l flue boil er. Again,the bottom ha f of the single flue is of littl e

or no use for evaporative purposes. As multitubular boilers are quite practicable even for th e smalle st model locomotive if a suitable siz e of ﬂue tubes is used

Fi — F E B x D T B E F O - S LE E I E m o R m. C 254 . g. . AN U S A t A NG N

(see table,page although the water- tube boiler may be con sidered in some respects superior for tinier models,a few designs of ﬁre - tube generatdrs are included herewith,different methods of

construction in each case being employed . 254 u n Fig . illustrates to a scale of 3 full size a s itable arra ge

l - n ﬁred t ﬁrebox in . ment of ubes and for a 2 scale engi e to be by an

W Th e - A ordinary spirit ick lamp . cross sectional view ( ) shows a ﬁrebox bulged out so as to get the maximum area of tube plate (and therefore the greatest number of tubes) and provided with

- t h t- fir box —in B n t stra e . five é i . ubes . With a y sided and fi tubes ( ), larger h eating surface can be obtained,which most l ikely could l fir box te A be further increased by bu ging the e as indica d at ( ) . Incidentally the drawing depicts one way of arranging water tubes

b x th - in the ﬁre o . The tubes emselves,if silver soldered in place, shoul d prevent the inner ﬁrebox from failing, and th e stays .

1 98 THE MODEL LOCOMOTIVE : I TS DESIGN AN D CON STRUCTION .

As the boiler should be ﬁred with a spirit wick lamp,and th e pressure need not be 3 0 1h th e more than . , tubes should be of th e . thinnest material pro curable, and as th e principal adhesive used in the construc tion will no doubt o ’ u be tinman s solder,in o c o manipul a ting th e L Y boil er, or any loco A W l d , L type boi er so ma e A be R care must exercised

1 e 1 to see that the wat r m is never allowed to 1 1 become too low and H T , se R expose the crown el O N leakage will surely re

. 1 1 . Of 1 sult course silver 1 1 0 soldering is the only preventative of th is, R an h t the O d it is here t a F - o h R wate r tube b iler as E L h t e . I decided advantage O It is possible to get at

L A all joints of a water C S tube boiler in a few minutes if th e back

A pl ate is arranged to come off and all steam pipes to th e cylinders are disconnectabl e by

unions. The roof of th e ﬁrebox should be sup ported by two stays and pieces of angle brass screwed from underneath with brass OI R N S N 1 99 B LE CO TRUCTIO .

c m s rews,the whole being sweated with soft solder. To for the smokebox,the boiler barrel is continued to the smokebox front, which may be a flat plate with door,a cast and turned angle ring fittin fixed r A g the barrel being to the f ont plate . wrapper plate conforming to the shape of the prototype shoul d be placed over the barrel at the smokebox and secured by flu sh screws ; th e space at the back under the boiler being fitted with a throat t t plate it thought desirable . With his design of smokebox fron it will be foun d very easy to model the front plate in accordance C L S R t E C . wi h aledonian, and . and . practice,where

i 2 9 F g. 5 .

?u b e I J ad e It’d “ p l a t e

Fi 25 . 8 . Fi 25 . g. 7 g

this ﬁtting is spread at the base and rests on the footplate ( see l ﬁg. The boi er would of course be improved by the use of

a ﬁ reh ol e,as in the last example described . The two foll owing designs for locomotive boil ers are culled from ’ L M odel B oil er M akin E . . M r. Pearce s g}the construction of which

in a large measure adheres closely to actual locomotive practice .

- n 260 a i . Fig . depicts a boiler suitable for a small type z scale

3 - 3 in . model ,in which the barrel of boiler is made from a piece of 1 g ts ﬁrebox n . drawn tube 26 i . thick The ou ide plate may be made from a piece of sheet copper,bent round to proper shape,and

1 b th e ubl ish ers of th is vol ume . M odel B oil er M aktng,price 6d . , y p rf s N A 200 THE MODEL L OCOMOTIVE : DESIG N D CON S TRU CTI ON .

l u riveted to the barre . The smokebox t be plate and front plate

- in t flan es flan e fit the may be g . brass cas ings,with g ,the g to out side barrel being turned,and a ligh t cut taken over the whole

a u th e h t The pl te on both sides to red ce t ickness sligh l y . inside ﬁrebox is t 5 in . t of sheet copper,the ube plate being 3 ; hick and 1 t . Ou h the res 5 6 referring to t e section of the ﬁrebox it will be noticed that th e tube and back plates are widened ou t at top to

' 202 mm11 11111 . LOCOMOTN E : rrs nmsran consrnucrl n 0 AND o .

- A fi . 262 i marke d out as shown at , g ,and n the other (the i in . scale B h fi ure boiler) as at in t e same g . In most model boilers the joint be tween the barrel and the fire box may be dispensed with by making the shel l in one piece,and whilst the common method of splitting a piece of solid drawn tube 44 1 h fi . 2 0 as shown in g ,p . 9 ,cannot be employed for a boiler w ich must have a dee p firebox (except by putting an extra piece on one side of the outside shell of the firebox),one plate for the boiler as w fi 264 be us and firebox shell,marked out sho n in g. ,may ed

' — - ' Snm na ou r WR PPER PL Ams. i 262. F g. A TY PE r T R T PL TE o H OA A .

ba l n ? .

. Sil ver ercd

Fi 4 — A S I LE -PL TE L oco Fi 265 — E T D or . 26 . . A S mp L E M g . NG A g i HO ol nnn S E LL x T TE P PL . B H . x mo TH E THROA A

h of with advantage . The p otograph the partly finish ed locomotive fi 4 64 exem l ifies t 8 . . ( g. ,p ) p his construction

A m -in r t loco otive type boiler of a size suitable for a g . scale f on ﬁ 2 ﬁ box in e 6 . r coupled tank locomotive is illustrat d in g. 6 The e this example is purposely made shal low,and may then exte nd th e B a partly over frames behind the driving wheels . y this means

firebox fi - in wide internal is obtained (see g. wider than on a i . scale coupled express (Plate and in consequence the crown of the firebox may be kept very low and a silent Primus burner 1 t th e u employed withou overcrowding f rnace space .

’ 1 U nder ordinary circumstances it is impossibl e to use a Primus burner of

i -in l i n e n a scal e mode . th e s l e t typ g . OI R N S N 203 B LE CO TRUCTIO .

As in actual practice the staying of the firebox of a large loco motive boiler with girder stays has been found,amongst other things,to affect the cle ans ing of th e crown of the firebox, and direct staying of a flat crown to a round topped shell being open to objec tions, the type of firebox shell known as the Bel paire h as recen tly become ul pop ar . The photo graph of the shel l of

1 - in model . scale boiler on th e next page will give a good idea of the plate fianging and jointing h of t is type . One po int of difference over the ordinary boil er which wil l be noticed,is that the throat plate extends over the top of the h boiler . T is plate is a l ittle diflicul t to flange,but of course a casting may be em ployed for all boilers built of brass or copper . Its use does away with the three ply joint at the throat plate,barrel and wrapper necessary in th e 2 MO rf SIGN N S N 04 THE DEL LOCOMOTIVE : s DE AND CO TRUCTIO .

u t ordinary type of locomotive boiler . Fl at s rfaces are s ayed by bolts to flat surfaces in the Bel paire firebox,full detail s of which h are shown in t e accompanying design . This boiler is extremely well stayed,and,if properly made,may be worked at pressures up 1 l h fi b x to 20 . The length of the barrel and re o can be altered a h e to suit any p rticular engine . T grate is arranged for solid fuel, and nine fiel d tubes are provided,together with a brick arch of cast iron. No dome is shown ; this may be added if required,but no advantage will be gained .

‘ ’ — OD PAI R E B ILE DE BY M R W OB IN C. i 2 A M EL B E L R M . L F 6 . R . 7 . g. O , A

M ild steel boilers sh ould not be provided with pl ate s of less than 5 in th e 3 2 . in thickness,owing to necessity of an allowance for rusting,and therefore will not be found suitable for engines of

- l in . Oi under g scale. course,steel boilers are very much cheaper than those built of copper,the difference being very noticeable in

- i l 2 in . the case of generators for L n . sca e and locomotives,which,if made in copper and steel respectively,would come out to about the 269 is d same price . Fig . a etail of the joint of the front tube plate l and th e barrel and smokebox p ates .

9 2 4 t 2- in l 6 . Fig. 3 ,p 7 ,illustra es a design for a . sca e boiler of simpl e but very strong construction,one of wh ich is in use in th e h h model locomotive s own in t e frontispiece . This boiler

m r has proved a marked success,upkeeping 1 00 l h . of stea unde

206 THE MOD M : 11 ‘ s D SIGN N S R N EL LOCO OTIVE E AND CO T UCTIO . repeatedly allowed to run very low in the boiler ; and should any leak occur at the front end,it can always be made good with little u Th l h tro ble . e col ar,which increases the strength of t e joint at the front,may be slightly recessed into the front tube plate with

Sam oa ! 5

— Fi . 269 . Fi 2 F1 xm LU UB 0. c F E T E . g g. 7 S

Fi . 2 3 g 7 .

Fi 2 1 g. 7 .

fixed advantage . Tubes in this manner can at any time be h removed . Tubes may eit er be arranged in vertical rows as V n h H fi 2 1 shown at or in horizo tal rows as s own at in g. 7 . However,th e number of tubes in tube plate of a model boiler being comparatively small,the shape of the tube plate and the size of th e tubes will very largely dictate th e arrangement of OI ' ' 20 B LER consrnucrmN . 7 tubes ; and often it will be found worth while to vary the rule for size given in the table on page ,53,to obtain a better disposition of 54 h t flu A fi . 2 the es. reference back to g will show w at is mean by A this,the method of placing the tubes . shown at in illustration being very much more scien tific than that at B in the same figure ; h h —in and in spite of the larger eating surface provided by t e g . tubes, the former is to be recommended— that is,if the bulging of the fire box tube - plate in the example B will not lend itself to a stil l more advantageous arrangement of tube spacing . F1g 272 ill ustrates a very good spacing for an inch scale engine

- with a 5 in . boiler barrel,and it will be noticed two longitudinal The tube plate stays are possible in this case. rounded top of the

ﬁrebox adds considerable strength to the crown.

WATER TUBES .

Of late years the use of water tubes in the firebox of model h boilers has been adopted with success . T ere are several meth ods fi 54 1 96 of fixing,and the one described by g. 2 ,page ,is one of the i t H to - s mples methods. owever,if the tubes are be silver soldered in ,as they always should be,difficul ties will arise during this operation owing to the tendency of the firebox shell to warp t i wh ilst in the fire and upset the join s . The stra ght tubes cannot be inclined to an ideal degree,and except in special cases it will be found worth while to use bent water tube s of the patterns shown 24 fi s 25 344 1 99 3 . in g . 7 and ,pages and Field tubes present an improvement over the straight an d slightly inclined cross tubes,and at the same time may be very easily fixed by screwing into the crown with a taper thread in th e d same way as the flue tubes already referred to . A etail of a ’ - fi 3 . 2 1 in . fiel d tube suitable for a . scale model is shown in g 7

in i d . For smaller models ﬁel d tubes may be 5 . d ameter outsi e

f o ra n K rap

— L s i 2 4 T K rn . F . g 7 . AN CHAP E R T XI .

BOI R M N N S AN D Frrrm s LE OU TI G OTHER c .

HAVING explained the construction of the boiler,and in Chapte r h e I ul . t e wi l V. given r es,etc ,to help in d sign,we l now consider the numerous ﬁttings necessary to the safe working and the manipul ation of the model locomotive boiler,dealing with each item separately,and commencing with

F SA ETY VALVES .

Th e Ramsbottom duplex safety valve is by far the most common t t m e in to locomotives of his coun ry,and is usually co plet ly cased . I t is not possible to make a good working model Ramsbotto m

- in — valve for a locomotive to a scale less than g . indeed the writer does not advise them for that size of model . Th ere is no nee d f or th e two valves,and the means for adjusting the spring cannot be 2 6 — . . t in e satisfactorily arranged Fig 7 illustra es a design for a i . scal C H aledonian model . ere the tension of the spring is altered by the nuts on the under side of the base of the valve (the ste am joint must be broken to do this),and th e movable pivot on th e il forward point of the lever is necessar y omitted . The points sh ould be very sharp,and the valves should be countersunk so that th e the contact is below level of the seating of the valve . Fig. 277 shows a type of safety valve in which the adjusting nut is not th e placed inside boiler,and in which no upper casing is employed . — L . W. R . N . in . Plate IV . (i scale model locomotive) illustrate s to half full size a valve in which th e external appearance is is Th retained and a single direct loaded spring valve employed . e lever is no t entirely an ornament,but can be used to ease th e 208

21 0 MOD M V 11 's SIGN n rn n THE EL LOCO OTI E : DE AND co s ucrro . riveted to the shell,and the dome cover should ﬁt the pad quite ff tightly,so that it will not fall o . E M id W N . The type of safety valve casing used on the G. . , . , N G. R e land and . ailways,is very often favour d by model makers because of its simplicity,neat appearance,and the fact that it may t ﬁnish ed l be to a large ex ent in the lathe . The ful size drawing

- in R N . . G. for a g scale valve shows a method of making a . valve, no outer casing being employed . The body of the valve is in halves with the bottom portion secured to the barrel of the boiler by ﬂush th e pins,the upper part screwing into latter. The draw back to this valve is the liability of damaging th e polished exte rior b and Th of the removable portion y screwing it in out. is evil is IV e somewhat mitigated by the valve shown on Plate . ,the upp r part of which is not circular and can be unscrewed with the

ﬁn ers G N . R g ,but as the circular column is a feature in design of . . locomotives,the only way of overcoming th e trouble . is to make

h ﬁ 280. the casing entirely separate,as s own in g.

To make this valve,a piece of stout tube 1 in . in diameter is pro cured and one and closed by silver - soldering in a disc ; the inside t th s ﬁ t of the other end is apped wi a bra s thread. To this a piece of brass rod should be bored for the steam way and screwed outside t h h wi h a continuous t read to ﬁt the tube . T is nipple is screwed into th e boiler and sweated,the hole being prepared at the top to receive the valve . The remainder of the work is simple,the spring being of steel with the ends nicely squared and the valve

’ - in - h being thoroughly ground quite steam tig t. To increase the pressure on the valve the tube should be screwed further down h h on to the nipple. T e closed end of t e tube is intended to be perforated with three holes for the escape of the steam and h e s n fits one for t central valve stem . The ca i g the tube and fixin should require no g. The valves of larger model locomotives may with advantage be quite separate from the stem as sh own fi 28 2 u h in g. ,which ill stration depicts anot er substitute for a cased n i Ramsbottom valve . This type of valve is to be recommended for all sizes of model engines . Another kind of safety valve similar in general arrangement, t I th e accom if not form,to h e type shown on Plate V. ,is shown in fi panying illustration ( g. The spring is inside and yet does

2 THE ' 21 MODEL LOCOMOTIVE : 11 s DESI GN AN D CON STRUCTI ON .

r not in any way interfere with the staying and piping of the boile . Covered with a casing,the ﬁtting may represent either a Rams

G R . N . . bottom or . type of safety valve

w Do ns.

Domes are used to provide a means of taking the steam as far as possible from the water level,and whilst in larger engines the dome will generally contain the regulator,for the tin ier model it will be

? l a gged

b‘ 5 f f p1 M PI/

- — i e for in sca e. Fi 283 DOME STE M PIPE R R E ME T . Ha f s z . ) g. . A A ANG N S ( l i l

’ ‘ ‘ G W G t a ’ De G N R . . C. . ca o . . . R . R ntics G. E . R . . . p d A l . B o ie Sin es g gl .

4 — TY PICAL D E COV ERS in sca Fi . . e 28 . . g. OM (f l ) found convenient to simply take the steam from the uflpermost part of this fitting by a piece of pipe . This method lends itself to th e use of baffling arrangements such as are

fi . 283 fi 3 shown in g ,these sketches (and g. 05 , page 223) also illustrating four methods of fixin g the dome to the boiler. Th e dome in a water- tube boil er,if fixed in the ordinary manner,preventing the ready .

Fi 285. g. removal of the barrel from the outer shell,it will be found better practice,wh ere th e feature 1 8 not used solely as an ornament,to arrange that the inner dome may be easily

' VE : l i AN D N I N 21 4 THE MODEL LOCOMOTI s DESIGN CO STRUCT O .

h e r induced by the exhaust . C imneys in real practice are eith i buil t up out of plate mater al or cast in iron .

i 2 — L Y F 87 . . . K g. -in sca e (g . l . )

Fi 28 ST N D RD C IM E . g. 6 A A H N Y

R . 2 8 . Fig. 8

Fi 2 — i . 90 1 9 OL D G E B F . 29 Fi 28 ...... g. g g AN D L W R . S . . .

E t G N R h xcept in the case of the la est . . . c imneys,which have the shoulders indicating separate pieces,a cast iron ch imney h as li di i i no nes st ngu shing base,stalk and cap . OI R A D F 1 5 B LE MOUN TIN GS N OTHER ITTIN GS . 2

CAB A R N S AN D Fl I G R A GEMEN T TT N S .

I n th e cab of th e smallest model locomotive two ﬁttings are always advisabl e — a water gauge ( or other means of ascertaining

th e th e e level of the water in boiler),and a steam pr ssure gauge . A regulator is usual,but in some cases may be dispensed with if a . 21 6 THE MODEL LOCOMOTIVE : I TS DE S IGN AN D CON STRUCTION . reversing gear actuated from th e cab is employed,or the smoke

- R . l in . . N e door regulator shown on Plate II (Q scale . E ocomotiv ) adopted . The cab ﬁttings for a simple model (see page 25 1 ) will be explained

h ﬁ - t . 2 H by a reference to e accompanying g 92. ere a water gauge is not used,and in its place two try cocks,one to indicate the l a highest and the other the owest water level dmissible . The regul ator box (see detail on page which is on the outside of the back plate of the boiler,aff ords a means of connecting the ste am h gauge to the boiler,the pipe for which is bent to form a syp o n .

- i th te The gauge is Q n . diameter,but wherever possible e wri r advises that these useful fittings should be of the largest diamete r possible . Instead of coiling the pipes to make a syphon,which by the way is essential,inasmuch as the accuracy of the gauge is preserved for a longer period,very neat special fittings ful fil l ing th e same purpose are now obtainable . As l arger model locomotives almost always have a fireh ol e,even when oil- fired,some sort of a door is essential,and th e lift-up o n and slide d or patterns are to be recomme ded as the best.

2 ﬁ e- ﬁ in - Fi . 9 e r tt s in g 3 illustrat s the door and g for the cab of a i . scale engine in which both brakes and blower are provided for . To save dril ling a large number of holes in the boiler,a casting

- s ul co r may be made for a three way boiler junction . Thi sho d be rectl y faced,sweated on and furth er secured by two brass screws

- a to the curve of the back plate ﬂange . The right h nd branch should have the steam- brake pipe screwed into it,a stopcock being placed in a convenient position on this pipe . The centre branch e should be screwed for a union for steam gauge pip . The position

u th - of the steam gauge is abo t e only one convenient for the Q in . scale model in a model to a larger scale the steam gauge can very wel l be placed in the usual position,the right- hand junction being used for this,and the centre one connected to the brake . The steam gauge in th e position shown will be more easily seen than is if it placed up near the roof of the cab .

T - h e left hand junction is the blower connection. One of the t th e — oi 3 —in longi udinal stays through boiler should be hollow 1 3 . solid- drawn tube — and the nut at back plate should be a special one,and project beyond the end of tube -stay,so that a bent cbck

2 1 8 THE MODEL LOCOMOTI VE : rrs DE S I GN AN D CON STRUCTI ON . for tubular boil ers are diagrammatically sketched herewith,al l o f ﬂ which give the desired exibil ity. Where a retardation of the steam in its passage to th e cylinder is not advisable,a contin uous coil superheater should be

— t i - in k on avoided al hough in small eng nes of g . scale wor ing sh arp curves without governors or any other system of automatic control this is not a disadvantage,as dangerou sly high speeds or to should in some degree be prevented . Therefore,f engines be h ridden upon,the types of superh eaters (D ) and (E ) are t e best. The orthodox system of steam piping may be provided with a single union at th e top in place of two,the pipes being attached to fl fi th e steam chests by ordinary anged joints (A) ( g. In the other designs two unions are advisable,one each side of the supe r heater and if this course is adopted,steam - pipe fixing will never

(D )

— STEAM PIPE D S PE R E TE R R RA E E TS Fi 295 . . g. AN U H A A NG M N present serious difficul ty,and ex periments to test th e value of the superheater can at any time be readily made by substituting the ’ ‘ h supe rheater for a sh ort piece of tube . The gridiron and air pin superheaters sh ould be designed and fitted in th e smokebox so that the small tubes do not come in the way of th e blast- pipe , and also in such a way that they are just above th e level of th e top t i row of tubes and allow the la ter to be eas ly cleaned . ’ As in the methylated spirit - fired engines flame superheaters ’ are th e best,th e Smithie s type boilers will be found to allow o f this kind of superheater better than any oth er,and this is wh y th e water - tube boiler is to be recommended,with fewer q ualifica h t Smokeboxes ui . ions for small work . should be q te airtig t

S PIP S BLA T E . The chapter on cylinders describes various methods of arranging th e exh aust pipes of a model locomotive,and for an o utside - cylinder BOIL R M N N S AN D FI T'riN s 219 E OU TI G OTHER G .

c i 1 21 fi 1 3 model the onstruction ndicated on page , g. 7,is a good one where th e blast - pipe orifice need not be very l ow down in th e Th e smokebox . two pipes are halved at the junction as shown in o ifi fi 296. the z r ce g. If correct si e of blast is obtained by the use of suitable exhaust pipe,

‘ noz z l ing will not be required ; but shoul d th e same prove necessary,th en screwed caps may be Fig 296 ﬁ 2 . made as shown at (A) in g. 97

M any of th e cylinder designs in Chapter VII . requiring only short straight exh aust pipes,the caps just mentioned may be used to bring the oriﬁces to the proper diameters given by the rule on pages 58,to wh ich the reader is referred for fuller information as to size and position of blast pipe and to the arrangement of the petticoat pipes and chimney .

u t h Plate IX . ill s rates another met od of connecting the blast

- i h th e u pipe of an outside cylinder eng ne,and Plate VII . s ows sual meth od adopted for inside cylinders having th e valves between, a ﬂanged joint and a plain piece of pipe being employed . Any crevices in the smokebox shell,caused by the passage of steam and exh aust pipes,which would draw air shou ld be stopped with asbestos .

W S BLO ER .

Although the single jet blower placed by the side of th e blast pipe has the merit of simplicity,and if it is kept suffi cientl y low ' in th e smokebox will,in small models,serve its purpose very well, fi 29 h an improvement is indicated in g. 7 ,in whic th e th e th e jet emerges from centre of blast pipe . For larger model s a more effi cient arrangement fi 8 . fi is illustrated in g. 29 This is a modi cation

29 . Fig. 7 of the common ring blower, and is formed by bending a tube as shown,plugging the extremity,and ﬁtting several jets . The length of the tubes may be very m uch sh ortened if they are soldered in in the righ t direction,or plain h oles care l fully dri led may be employed if preferred . The longer jets allow of bending after th e blower is con structed,and may for this reason n be retai ed . Th e total area of th e blower jets in models often being made 2 MOD M V : 11 's S N S N 20 THE EL LOCO OTI E DE IGN AND CO TRUCTIO .

much too large,as a guide the following suitable sizes are give n

below . B or TA LE BLOWER J E TS .

ri 1 in o ﬁce . Small models. Single of 3 5 . in diam

1 - l 1 1 in . in . e . 14 sca e,thr e jets 4 6 to 3 5 in diam 1 1 in . four 3 9 in diam . 1 1 1 2 5 1 1 1 2 6 2 1 n 1 6 n

K SMO EBOX FRON TS .

As the orthodox smokebox door does not,in models of small h t scales,allow of muc room for get ing at the pipes,etc . ,the doors may with advantage be imitation ﬁttings,the whole front being C a capable of ready removal should occasion require . ircul r smoke boxes will generally be found to facilitate the ﬁtting of such smoke

. A box fronts ll large engines should be provided with . absolutely air - tight doors,and to prevent the rapid bliste ring of the paint on the smokebox of the model,a lagging of sheet iron and asbestos may be arranged both inside the door and around the inside of th e ﬁ 26 g smokebox wrapper plate ( see g. 8,pa e

R S EGULATOR .

’ ’ These ﬁttings,as th e name implies, regul ate,at the driver s will,th e passage of the steam to the cylinders,the lever operating

the steam valve being situated in the cab . There are innumerable patterns available,but as there is no one which can be satisfactorily

employed in all cases,several will be described . I t the builder does not trouble about a realistic arrangement in the cab a plain plug cock outside the backplate of the firebo x may be fitted,the steam pipe passing down through th e flame and

fi . 30 the plug having a long lever attached to it as shown in g 7 . The plug cock may be pl aced in the base of the dome,as t fi 02 th indica ed in g. 3 , e rod passing through a gland in the back plate and the orthodox handle employed,or it may be put in the smokebox and worked by a rod passing through a tube,as depicte d fi 3 00. in g.

222 THE MODEL LOCOMOTIVE : 11 s DESIGN AN D CON STRUCTION . a simil ar arrangement of ports partially rotate s ; and when these are moved opposite to each other,ste am is allowed to pass from h e h ﬁnish ed t dome to t e steam pipe . A regulator is shown in the n 2 6 accompanyi g photograph on page 2 . The valve is actuated by two ve rtical l inks attached to levers on the regulator rod,which

S E C T 'O N

— i 9 E . 2 . A M P G F g. 9 SI LE R ULATOR

Fi 0 — 3 02 . 3 0 X L T Fi . A S . E B E R . g . MOK O R GU A O g

' J no rl

passe s in th e usual manner through a stufﬁng box in the backplate h h to the h andle in t e cab . T e drawing of th e regulator is hal f size for an inch - scale model ,and shows the column made from a cored casting. It may,of course,be built u p from tube and rod n th e l t ﬁ 4 3 0 . brass in a similar man er to regu a or illustrated by g. This is of th e usual slide valve type,th e pilot valve used in l arge

224 THE MO I VE : I TS S N AN D N S N DEL LOCOMOT DE IG CO TRUCTIO .

A ﬁtted l work being omitted . ﬂat brass spring should be to a ways s ul n keep the valve on to its face. Thi reg ator is desig ed to suit a

2- in . scale locomotive . W E e G . c For engines built after the lat st . . practi e,where boiler with high Bel paire fireboxes and without domes are employed,the u o reg lator shown in Plate V . is a very good ne . fi 3 03 exem lifies h The detail drawing, g. , p the construction of t is kind of regulator,and at the same time indicates a modification of some val ue,the valve,instead of being permanently fixed to the regulator rod,being a separate piece of metal slotted to fit the fla h ttened end of the rod . T is freedom allows the valve to make proper contact with the face at all times . In making regulators on this principle,care should be taken to see that the valve and port faces are recessed so that they do not touch each other at the out l side edge or in the centre. The necessity for this wil make itself

- - evident when the valve is being made steam tight by grinding in .

N R - G. The majority of . . locomotives have pull out regulator handles in the cab,and therefore slightly altered arrangements are necessary according to the type used . In Plate III . a slide h on 011 valve regulator is s own in which the rod is pulled and . ﬁ 266 2 m iﬁ ation . 3 9 . 03 od c Fig 0 herewith,and g ,p . ,show a of this type suited to engin es employing the dome in th e legitimate manner.

ﬁ . 4 G . N . R To actuate the regulator shown in g 3 0 by a standard . ’ driver s handle instead of the regulator rod rotating,the rod should

- ﬁ 3 06 be ﬁxed to one arm of a bel l crank lever as shown in g. , when the pulling and pushing of the handle will lift and lower the t slide valve,shutting and opening the valve o steam .

IC CH S AN D MISC AN OU S N S FIRE GRATES,BR K AR E , ELL E FITTI G .

E ngines burning solid fuel sh oul d be provided with a suitable grate made up of rectangular bars placed a distance apart equal to h th eir t ickness . To preserve these air spaces distance pieces fi 3 1 1 may be employed as shown in g. ,which also illustrates one fix firebox t i meth od of ing a grate to the . Some imes it is adv sable to arrange the grate so that by the with drawal of a pin th e whole of the fire may be dropped on to the floor in case shortness of t n fi water occurs and here is no mea s of replenishing (see g.

2 T E 26 H MODEL LOCOMOTIVE : I TS DESIGN AN D CON STRUCTION . the passage of th e delivery can be stopped from en tering the boiler and trapped in the pipe s should be allowed,otherwise the failure of the pipes or the pump will soon er or later occur through the driver forgetting to open the valve or cock when the engine is u abo t to be moved .

L AGGIN G . The lagging of the boiler of a model locomotive with asbestos , ﬂannel soaked in al um or other substance,covered with sheet metal ( tinplate,Russian iron or thin hard brass) is not always a satis factory or interestin g task,and in smaller models the absence of such covering wil l not be felt in any marked degree (th e losses from radiation in an uncovered model boiler generally amountin g to about 1 0 per except when models are worked out of h doors in the cooler seasons of t e year . ’ The outer metal covering is called the cleading, and in real engines is laid on in several piece s,th e joints being hidden by

in h not f ul ﬁl lagg g bands . T ese bands in models do usually the same object,but as they form important features in th e external

ﬁnish ,should not be omitted. The widths of th e bands employed 1 1 2 in Fo r d l in actual practice vary from 17 to 1 . mo e s,strip brass 1 in th 3 in from 3 2 . ickness may be procured in widths from 3 3 . 3 1 4 3 1 5 h two m t at Figs . and s ow ethods of join ing the bands the l under side of th e barre .

’ F 3 1 6 — S rnoun i . . A MODEL L E Y RE G L T R g U A O . CHA R PTE XII .

CABS, TAN KS ,TEN DERS , BOILER - FEEDIN G AN D FI RI N G A N S RRAN GEME T .

AMONG the mate rial s which may be used for the superstructures of model locomotives hard rolled brass plate which can be obtained ﬂat and smooth,will suggest itsel f as the most suitable,although

- u for large engines of 1 in . scale and pwards,the use of sheet steel will reduce the cost of the work considerably. Aluminium or brass castings and stamped tinplate are also em man ufacturin ﬁrms e m ployed by g wh re models are to be ade in bulk . With the ﬁrst- named,however,it must be remembered that good threads are not always easy to cut in aluminium ;and where it is used,th e parts made of this material should be those with the greater number of clearing hol es,rather than tapped holes, t th in them . Brass and tinpla e lend emselves to the use of soft solder as a jointing material ; but for better work hard rolled

l Tin sheet brass and angle brass wil give the strongest structure .

-in plate may be used for small models of Q . scale or thereabouts with great success,solder alone being employed as the join ting

material .

f - in and 411 o . Plates 1 . 3 thickness are employed in prototypes, and care sh ould be taken not to use very heavy stuff on th e model, especially in th e matter of footplates,which show their th ickness at th e edges,otherwise the appearance of the model wil l be

-in d l l - in spoiled . In 2 . scale mo e s ? b . plate is very suitable for such l d h work as cabs,tanks,footp ates,ten ers . W ere wate r is to be d containe ,brass will prove to be the cheapest material in the end . Along the edges of the footplates of a locomotive webbing strips are employed,and in al l cases the footplates overlap this webbing 227 2 28 MOD M : 11‘ s S N AN D N S N THE EL LOCO OTIVE DE IG CO TRUCTIO .

d fi - or e ging (see sketch, g. The model maker will find angle brass serve the purpose admirably,and where a shaped finish at “ the buffer plank is required,the method of construction shown in fi 1 3 . g. 7 is suggested The vertical plates which carry the steps up to the footplate are often made flush with and form part of th e edging,but whereve r n fi 3 1 9 possible the steps should be set back as i dicated by g. . They wil l then be found very much less in the way,and will not be damaged so frequently. In building up th e spl ashers,tanks and cabs of small model locomotives,in ste ad of using continuous pieces of angle brass for

Fi 3 1 8 g. .

i d e 6 /a fé 9 a 1 Fi 3 1 9 — S TE PS g. . - I N F OR A ﬁ .

i 3 20 M D E L . 1 F . . SCALE Fi 3 2 . g. g O the joining of two plates together at righ t angles,short lengths of say one inch may be employed,at intervals,the first operation being to sweat and flush pin,or screw the angle to one plate ; then the two pl ates may be brought together and similarly secured,the whole joint being subsequently soft - soldered from the inside with to a bit,through out its length . If any accident should happen the model,wh ereby it is subjected to flames,or if furth er solderin g is to be done to th e work,it will no t fall to pieces in the way it would if no oth er positive fixing o ther than soft- soldering were d employe . — It is possible to procure half round brass wire from gin . wide, i h n which forms very suitable edg ng or eadi g for tanks and cabs .

Similar material of section is also obtainable . Disproportion ate sizes of beadings sometimes used give a clumsy,coarse appear

MO rs S N N S ON 230 THE DEL LOCOMOTIVE : r DE IG AND CO TRUCTI . is used for the whole side,it wil l be found that the plate is diffi cul t h fi 23 to handle,and unless a joint is made at t e top (see g. 3 ) the A 3 1 be ‘ best e f bottom part marked in fig. 2 will l t intact until the fix ou The t roof of the cab is ed . design of en lends itself to the retention of this connecting piece,owing to a raised footplate inside the cab being used,when th e narrow connecting portions may be t nd l th streng hened by strips a ang es soldered on to e inside . However,where flush side sheets are not imperative,separate side tanks,bunker and cab are advisable,as in the designs in Plates th . IV . e I II , ,and VII . ,otherwise,during repairs,the whole of superstructures must be removed together— that is,if the paint is not to be damaged by breaking flush joints .

- in . t Fig . 325 is a detail of the cab for a 2 scale tank locomo ive

W E th - at t L . t . e of the N . . ype, weather board the back being qui e

Fi 325 — AB D E 'r s g. . C AI L .

th th e - plain at the edge . Both e front and rear weather boards are ﬂanged horizontally,so that they may be screwed down to the to p

of the side and back (bunker) tanks . To enable the cab ﬁttings of the model to be easily h andled a large hol e is cut in the roof plate,and to cover this up when

th e use fitted n model is out of a separate roof plate is as show . This may of course be made to fit flush with the main roof, where a more or less exact scale model of a given prototype is

desired (see Plate VIII ) .

h t ﬁ -ﬁ h T e pho ograph ( g. 33 1 ) illustrates the partly nis ed cab and

h - in . splas ers of a model . scale model locomotive The roof of this cab has a large portion of its after end cu t away,this Open - ov h ing being covered by a steel c erpl ate . The side s eets of the th ﬂu h cab and those of e splashers are quite s . This method,as in th e already referred circumstance in tank engines,makes the superstructure rather unwieldy to handle ;and if a roomy cab is AB A - F I N N N 23 1 C S,TAN KS ,TE N DERS , ND BOILER EED G ARRA GEME TS . d e sired, the splashers must be extended laterally to the same m a ount,and may in some cases look rather too wide . The chief poin t the picture illustrates is the extension of the rear sp lashers into th e cab,th e reversing lever rack being made from

- T t h e inner side plates of the right hau d splasher . h e edging of the

w o 1 - i t . s n indows is also shown by the pho graph Strip of 1 3 x g .

Fi 3 26 . B g. UILDING Smok ns ox S DDLE A S .

t l se c ion brass wire eft bright are intende d to edge the Splashers ; an d to allow th e coupling rod and crank- pins to clear the splashers, e ou t A 28 h pi ces must be cut as indicated by ,ﬁg. 3 ,t e covers 0,for which castings in brass,with the edging strips cast ou,are recom e in afﬁxed B m nded,be g as shown at . Saddles to carry smokeboxes and to cover- in steam pipes are advisable wherever they are possible ,and can be made in a i t ao var e y of ways Fi 32 . g. 7 cording to the require

the Fi . 328 . ments of design . g On e good method is sh own by the several ﬁ 3 26 sketches in g. . 3 2 Fig. 7 shows a

Fi 3 29 Fi . 330. g. . g s1 mpl e method of TE NDE R Top s making th e front por tion of a typical leading front-coupled engine,a circular smokebox

an d cast door being used,and th e latter made ﬂush with th e saddle .

. t s as s When models are . to be made in quan itie , c t bras and aluminium may be employed for all portion s of the superstructure, 1 S W G N 6 . 1 5 . . metal patterns of say o . or material being used,all 2 2 MO E : l ‘ s SIGN AN D N S C N 3 THE DEL LOCOMOTIV i DE CO TRU TIO .

tc and edgings,copings,window openings,e . ,lugs,angles ears for th t n putting e parts together being incorporated in the pa ter s . C a ﬂat t ﬁxin ab roofs can be c st and be ben to shape before g. M any excell ent model s the writer h as had the pleasure of view h h ing have been spoiled by t e use of t ick handrails . In actual

r t 1 - 111 p ac ice 1 . tube is employed,and therefore steel wire for model handrails should be obtained of a gauge as nearly as possible a

Fi 33 1 — B D S PLAS H ERS F OR -I N S LE MODEL OA . . g. . AN A i CA

1 - n l N 1 2 t i . scale reduction of this diame er . For . scale mode o ,for

- ln N 1 5 - n N 1 S W G i . 6 . . . o . ,and for g . scale o . material should be th i to used ; o er s zes in proportion these .

N TE DERS .

Th e function of a locomotive tender is to carry the fuel and water required by th e engine,an d,as th e name implies,a tender is h quite a separate ve icle . The standard British tender is a six - wheeled vehicle as shown

ﬁ 3 3 th e t wh - n in g. 5 , otal eel base,wh ich is rigid,varyi g from about 1 5 f h W E . 1 f t. t e G . ﬁ . 1 t. to in . example ( g

234 THE MO V : I TS S N AN D N S N DEL LOCOMOTI E DE IG CO TRUCTIO .

M th - in latest idland tender, dimensioned for e g . scale model

' describe d ih th e Appendix .

- in e A design for a i . scale double bogie tender is shown in Plat i VII . The bogies,of course,do not requ re lateral play,being moy men ts th e pivoted only . It will also be noted that the e of bogie are very limited,owing to th e position of the compensating beams and bogie frames in respect to th e main frames of th e t 23 3 tender. For sharp curves the type of ender shown on page

6 - REAR CORN ER or Fi 33 . g. A STAN DAR D i 3 E F . 5 E D D 3 . T R . g N TE N E R .

would be much better,as,by the use of small wh eel s and low bogie t d frames,the utmost freedom is ob aine . Inside- framed bogie tenders look very well in conjunction with inside- framed engines,and also may be very easily made,th e work to the frames, springs,and axl eboxes being simpl iﬁe d in th e various ways already referred to in describing the construction of

engine bogies .

PU M PS AN D N J S I ECTOR .

Hand pumps are to be recommended for replenishing th e boilers of small models,although they are n ot so necessary where water ’ tube boilers of the Smithie pattern are employed,as these

r sufﬁcient a n run generato s hold water for le gthy .

A v t t fi . 3 ery good pa tern is hat shown in g 3 7 . In this example ’ th e d th t - no pump is rowned, e suc ion valve box needing pipe . th e passage being drilled th rough the casting and emerging at th e base,wh ich is fil ed away to allo w the water to enter th e m it n t to t th e a t passage. Someti es is o possible adop bove me hod, as the pump cannot be placed inside the water tank,and therefore a pipe will h ave to be carried from the suction valve—box to the main supply,or to th e communicating pipe in th e case of a side CABS N N S B R- F E N N E S 235 ,TA KS ,TE DER ,AND OILE E DI G ARRA GEM N T . an I I I h n t n a I . V o k engi e,as indic ted in Plates I I , . ,and V I . W ere water at all is carried by th e engine or tender,a piece of flexibl e (indiarubber) tube of sufficient length to reach a tank placed beside th e line may be fi tted to the suction box,and when not in use th is pipe may be coil ed up in the tender or bunke r . Hand pumps may be placed in one of the side tanks if th e bunker is used wholly for the fuel supply, or can be fixed at a con v enient place on th e railway and the delivery pipe attach ed by a screw union when ever the boiler requires replenishing . The above type of pump should not be made With a ram

n -ih larger tha g . dia meter, otherwise at high pressures it will be found diffi cul t to force th e ram down . Larger hand pumps should be fitted with a lever ,as illustrated in fi g. 33 9 . I f th e engine is desired to run a long time without atten

‘ tion,force pumps may be worked by means of an eccentric placed v n on the dri i g or coupled axle . 23 THE M O 11' D N D 6 DEL LOCOMOTIVE : s ESIG AN CON STRUCTION .

An - in arrangement suitable for a or gin . scale model is shown ﬁ . to g 338 . To ensure success it is necessary to design the pump throw more water than is required by the boiler,turning some of B it back into the tank . y this means the pump will always auto

matical l r - y e start. Large engines sometimes have a very small hole drilled in the ram chamber communicating with the outer air

— — Fi . P 3 3 AUTOM ATI Fi 33 L EV ER UMP. 8 . C PU M P . 9 . g . g

et- hi ma m and forming a permanent p cock. T s course y be e ployed

- in model practice. However,if a bye pass cock is used as hinted above, and arranged so that it is not possible for it to be shut off and th e

amount of the Opening capable of adjust . ment,the supply to th e boiler may be t regulated to a nice y. Pumps actuated from th e crossh ead are not to be recommended,and it should not be possible for communication to the boiler from th e del ivery of pumps operated by the engine to become closed,therefore clack valves of the pattern illustrated in ﬁ h a 3 1 3 t . g. are not sui able in suc c ses Donkey pumps may be employed for feeding the boilers of larger- sized loco — . 3 40 A g . SMAL L motives,a suitable arrangement for a 1 0} D ON KEY PU M P 1 5 - in or . gauge engine being one injector,

- - th e a donkey pump,and a hand pump . Steam pumps,imitating

h - 1 - in Westing ouse air brake pumps,of a size suitabl e for a . scale

238 MOD L M : I TS S N N S N THE E LOCO OTIVE DE IG AND CO TRUCTIO . cone,and F the delivery cone,both contained in one piece of h v ﬂ verﬂ w r ow H o o . t . e n o e G me al T er is o ly one hole, . is the pipe

M r L ‘ 022-in t . ea found that whereas the . injector would s art, without adjusting the steam jet by simply turning on the steam, too 0 1 8 so if not turned on suddenly,the injector would not do .

e m l t Bu t h Probably the extr mely s al size accoun ed for this. e found that if a pet- cock on the delivery pipe were opened before starting,th e 01 8 injector would start well,without adjusting the steam j e t,and upon closing the pet - cock th e water would at once

o t He - g in o the boiler . therefore made an automatic pet cock or valve in which the valve,opening downwards by its own weight, afforded an escape for air,but as soon as the water reached it,it r e n ow h ose and clos d the aperture. There is,therefore, not ing to be done but to Open the water valve in the te nder,and to turn on the steam,and th en to close th e two valves when sufﬁcient water h has been sent into the boiler . The injector works well,wit out t 20 l b readjustment,from the safe y valve pressure of . per square 2 h inch,down to between 1 and l b . per square inch,w ich is rather remarkable .

N A N M N S BRAK S N S FU EL,FIRI G RRA GE E T , E ,AND OTHER FITTI G .

Upon th e fuel to be empl oyed many important considerations m t on in the design of a odel locomo ive depe nd . Whereas ,say,a

3-in t 14 . scale engine charcoal may give excellen results,oil fuel may be found less suitable, and methylated spirit, burned in the Th ordinary wick lamp,utterly useless . e fuels from which we have generally to choose are as follows M ETHYLATED SPIRIT (or spirit of wine),used in a wick lamp,or

vaporised and burned in the same manner as coal gas . l PETROLEUM (lamp oil) . This fue may be consumed in a Swedish Primus stove burn er as first used in connection with H b M r. E M M r model locomotives y . . orriss,or in one of . L ’ C . . . Palmer s steam Spray burners (see p CHARCOAL,COKE ,and COAL in ordinary deep sided fi reboxes with U ' the usual grate . nion coal briquettes make excellent fuel for larger engines,being smokeless and of high cal orific

value . - 2 CABS,TAN KS ,TEN DERS ,AND BOILE R FEEDIN G ARRAN GEM EN TS . 39

M l N U E L ee r. PATE T F has b n suggested by Pa mer . Th e latter is made for foot - warmers,and is said to be an ideal i I fuel for model steam eng nes. t is smokeless and nearly odorless,

n 1 A and under natural co ditions burns slowly . small piece once fairly ignited will . burn to ashes without going out. It makes a little ash ,like red sand,unlike th e feathery ash of charco al,which t i flies over every hing. To use t,it should be broken up small,and thorough ly ignited before putting in firebox ; it should then be l Un th x urged by a be lows or blower. der e blast of the e haust it fierce S kindles to a white heat. It burns without parks or smoke, off r and when steam is shut ,will remain at a dull heat for hou s. t t M L h 1 0 M r . e . Palmer says ha essrs man Brothers, Bond Street,

N Y o C t th e t r - m ew rk i y,supply fuel for hei foot war ers .

u - in c h - For engines p to g . s ale,whet er provided with a loco type or with a wate r- tube boiler,the best f uel is methylated spirit,con m su ed either in a wick lamp or by means of a vaporising burner. ‘ Otl uel in u a f a Primus burner may be sed in speci l instances.

L t s -in h in ﬁrebox ocomo ive of g . scale wit water tubes the and ample heating surface should be ﬁre d with P etrol eu m on the

s th e t S ra otl Primu system,if leas trouble is desired . p y burners d t t t n may be use ,but hey require a li tle more a te tion . Ch arcoal will be found a very good fuel if th e boile r has in suffi th e firebox h A fire cient heating surface and if is deep enoug . made up of this fuel Will req uire constant replenish ing,but the ’ heat obtained is very much su perior to th at given out by a Primus oil burner.

1 -in h t ﬁr x M odels of . scale aving wa er tubes in the e bo may be il ﬁred by o in Primus burners with great success. Under other circumstances ch arcoal or coal,or charcoal,cinders and steam coal U c t t admixed,or nion ompressed blocks,will be found sa isfac ory .

L arger engines,except those with water- tube boilers, having more than 3 0 square inch es of great area and capable of being ridden upon,are best not ﬁred With anything bu t Welsh steam coal or

u s ra otl burners coal briquettes . Powerf l p y may be employed in

ﬁr iz 1 - W e . s e and l in conjunction ith a coal The smaller s ( 1 ﬁ . scales) may be fed with a little coke,charcoal,cinders,or oth er

l ight fuel in addition to th e coal,or briquettes alone . Water tubes are not so essential in an engine consuming solid 40 E 2 TH MODEL LOCOMOTIVE : I TS DESIGN AN D CON S TRUCTION . fuel as in cases where methylated spirit lamps or Primus burners are ee used,but a d p grate is indispensable . The author has,it will perhaps be thought,rath er forcibly stated the case of the water- tube boiler for tinier models in previous chapters ;and while their superiority is not at ﬁrst apparent,it is the fuel (spirits) used in small locos that really decides the ques

M t i -in n . tion . e hylated spirit may be used with success ,say,a ﬁ scale model with a loco - type boiler ;but to ensure this it is neces

o ﬁr b x -in sary t make the e o and tubes of very thin metal . Screwed tubes are th erefore impossible,and other valuabl e accessories,

fiam - n fi d such as e surrou ded superheaters,cannot be so easily tte . Water tubes in th e firebox are necessary,as most of the work is done by th e surfaces in contact with th e flame,the methylated spirit wick lamp having th e peculiarity of evolving. more vapour h confined n An t an,in positio s especially,it will consume. ill ventilated fire will burn quite blue,and it is n ot until the color of the flame has an orange tinge th at anything approaching complete h combustion is taking place . During the time that t e engine is standing,choking will be very noticeable,and the smokebox and tubes will be found to be covered with beads of condensation, showing also that no usef ul work is being done at the end farthest fire box h O m from the . The remedy is a good draug t. ne ethod of ventilating the fire of a small loco- type boiler having a big fire fi 44 m n . 3 h h . box and a co paratively large lamp is show in g . W en t e engine is steam raisin g and is not running,th e induced draught caused by the exhaust being inactive,the auxil iary flue should help matters considerably .

- h e For the before mentioned reasons,viz . ,t more or less local ’ heat supplied by the methylated spirit flame,a Smithies water - tube boiler has greater advantages in that the most efficient portion of the heating surface is in contact with th e fire,and during steam raising th e fire may be readil y ventilated by opening the smokebox h n t door . T ere are certai rules in making spiri lamps which,if observed,will tend to perfect success in the working of a model t locomotive and lessen the liabili y of accident. Wicks sh ould not be placed too high or close togeth er,but evenl y

ﬁ 334 . distributed ;see g. for example The reservoir shoul d be con nected h n ﬁ 343 to the wick tubes by small pipes as s ow in g.

242 MO D E L Locomorrva I TS E S N N THE : D IG AND CO S TRUCTION .

have none of the objectionable features of those of methylate d ﬂam spirit. The e temperature is certainly much higher in the

former ;and whilst an induced draught is indispensable (see p . t n more complete combustion is ob ai ed with less air . Flue tube surfaces therefore have greater evaporative value,and superh eaters in th e smokebox may be employed with advantage, as under ordinary circumstances th e smokebox temperatures are su fﬁcie n tl y t r high to warran thei use in this position . Swedish burners require ordinary lamp oil,vaporising it in the burner, the jet of gaseous petroleum being passed through a ’ Bunsen tube and emerging from a series of silencing holes on atﬂ s th to the b e ,which complete e ignition of th e gase s . To give an impetus to the jet and to keep the burner full of oil,the tan k is sealed and air is pumped in on top of the oil ; the output of th e th e burner depends on pressure of air in the reservoir .

A 2 -in No 4 w su - t 1 . ( . ) Primus burner ill con me about one hird of a pint of oil per hour,and therefore it will be seen that with parafﬁ n

- at a penn y per pint an inch scale loco will not prove costly to run . For small locomotives it is necessary to bend up the conducting tubes of the burners (this can be done easily in the vice) so that the union spigot stands at right angles to the vertical centre line of th e A th e E n h burner. s the threads of burners are not of standard glis pitches,special reducing sockets must be made or else the pipe sil ver- soldered directly to the burner (see Plate Soft solder cannot be relied on nearer than six inches to these burners,unless the joints are also screwed ;for instance,the wheel valve shown in to th e as a Plate IV . should be screwed tube,the solder acting

caulking material only . Soft soap smeared on unions and other packed joints will

- I t h effectually make them oil tight . will also be found t at great care is required in making joints for Primus pipe work— o l d t i A v s gasﬁttings are worthless in h s connection . ll swi el joint

must have packed glands . V th A very suitableburner arrangement is shown in Plate III . , e u t n burners being screwed into a rectang lar sec ion tube . The o ly improvement worth mentioning would be to provide a release valve near the burners to drain away the oil when the burners ﬁ h s to are not working ( g. T is i an important point,and

2 THE MO M V : I TS S N AN D N S N 44 DEL LOCO OTI E DE IG CO TRUCTIO .

V . be minimise the evil in the designs on Plates IV and . it will noticed that the wheel valve is placed near to the burners ; how h t e ever,t e drain valve is in some respects the be t r arrangement. The ﬂo oding of the burner with oil whilst it is cold sh ould always be prevented, as the impurities present in the fuel although some of these may be kept out of the tank by straining — n f r w the supply ofte ind thei ay into the nipple,and stop it up . Therefore,even if a drain valve is not used,a good screw - down v h l t th e wheel val e s ould regu a e passage of the oil to the burner . Another thing that may occur to make a burner fail is that the loose cap on top,which must be removable to allow of n ozzles being taken out when occasion may re quire,may come off,and the burner

Val ve

— A — U I I R O Fi . 3 51 . R Y B R E R I CTI . 350 A X L A Y BL WER F OB , g SP A Fig. . U N N ON STE AM RAIS ING .

h smoke ; so it is advisable not to remove the wire w ich is put on by the makers to prevent the cap being lost in transit ; if it is removed it should be replaced,or other means taken to prevent

the cap from falling away .

Th e method of starting a Primus burner is simple. Having previously shut off oil- supply and ﬁl l ed tank with oil about

half-full),place under th e burner a tin pan containing a dessert t L h spoonful of methylated spiri . ig t this,and then insert in l h ﬁ 3 50 com the chimney an auxiliary b ower, s own in g. ,

246 THE MO E : I TS S N AN D S N D L LOCOMOTIVE DE IG CON TRUCTIO .

Spray burners are in principle really oil ejectors,and are dependent on the steam in the boiler . They will,the author 1 l h n 1 0 h . 6 i understands,evaporate of water per . of oil,and cub . . t 460 s t per minu e from q. ins . of hea ing surface . Th e be c t fi 34 burner should onstructed accura ely,as shown in g. 7 th e n E with hole in F perfectly centred in all positio s with . The E l 0 1 e B 0 2 in hole shou d be in and the hol in cap . in diameter . e D an d at C The st am should enter at , the oil . The cap should be t r fine adjusted until the burner h ows a ,clean spray . It should operate easily enough to work moderately by blowing w D ith the mouth in the end of the steam pipe entering at . It w li h t th a ill ft oil an inch or more above t e ank . If e tank h s to be o be ab ve burner,a cock must placed on the supply pipe. This burner should blow into firebox at or below door,on to a grate covered with perforated tin,with broken soap stone above a brick arch of soap stone or firebrick may be employed with adf anta e A fire d u of g . coal may also be use for the p rpose flame igniting the . This burner requires a strong draught, or dense smoke and failure will result . To start the burner,com pressed air is necessary until steam appears,and a bicycle inflator

h - ﬁ h s ould be attached to a non return valve xed in t e boiler . The steaming of engines consuming solid fuel must be regulated t th e o f in other ways han by supply . The most useful method checking the evaporation is by means of an enclosed ashpan having a ‘ damper door,the opening and shutting of which alters the

h fir Th e fireh ol e amount of air passing to t e e . door may be used in conjunction with th e damper,but this should not be kept wide open when the blower is full on ,or when th e engine is working h ard,as by doing so a considerable amount of cold air will get to h ff c th e h t th e t e tubes and a e t tig ness of boiler . If the fire is sluggish,then with the damper wide open and th e e fi reh ol e door quite close,it may be urged by the use of the blow r . If th e circumstances are opposite,th e injector should be put o n , the firedoor opened,damper closed,and th e blower shut down to m the fi ues h u the inimum . To ensure engine steaming,the s o ld be swept at frequent intervals,and th e smokebox door sh ould be kept

- absolutely air tight . For ste am -raising pu rposes an enlargement of the arrangemen t CABS AN S N S B -F N AN EM N 24 ,T K ,TE DER AND OILER EEDI G ARR G E TS . 7

3 50 illustrated in ﬁg. should be used,a footblower taking the place l of th e hand bel ows . Instead of an extension stack a small pipe

in 2- in . (about i . diameter for a scale loco) may be inserted in the smokebox,the extremity turning upwards and acting as an auxiliary blower,the outer end being coupled by a flexibl e pipe to the foot blower. Do not in any case attempt to couple the foot th e blower to boiler to work the steam blower by air . This arrangement has obvious drawbacks,and the ste am blower orifices will,or should,if they are correct in the first pl ace,be found much l ow r too small for the pressu es obtained by a foot bellows . The most usual cause of failure in model locomotives where th e design is good,is in the matter of smokebox arrangements and E h th e valve setting. ngines often fail throug valves being badly i faced and allow ng the steam to blow through to the exhaust. Where such a blow is present,it will also indicate that either the pistons are faulty and wanting new rings or packing,or else that th e cylinder is not truly bored . Again,the valves may be rusted on the spindle,and be o ff their faces if th e engine has not been worked for some time previously. An irregular beat shows that

' th e valves require setting,and an engine with a wet sluggish puff sh ould be provided with either a superheater,or a smaller blast nozzle,or perhaps both . Inability to steam where the engine h as been working all righ t generally suggests a leak in th e boiler or in th e steam connections , such a leak,h owever small and unnoticeable,interfering with th e h n l draug t and reduci g the evaporative power of the boi er . 1 i L n . n a t For engines of £1 and scales upon which the ow er c nno ride,elaborate systems of control from th e line may be devised,and where such are not used and the line is laid alternatively with long straight runs and comparatively sharp curves togeth er with th steep inclines,some me od of control is advisable. Throttle valve governors are therefore suggested ,these acting when a S h c ertain peed is reac ed . t t M r H Le a To regulate the produc ion of s eam . enry used an ﬁ ﬁ in 349 . tt automatic jemmy (see g. ) with great success This g is worked by the steam,wh ich at given pressure lessens the inductive

h e h r s action of t exhaust on t e ﬁ e . Fixed to one ide of the smoke

v - B 0 th e box is a val e box and cylinder . Steam is led from 48 THE MO M V : I TS S N AN D N S N 2 DEL LOCO OTI E DE IG CO TRUCTIO .

boiler to the under side of valve E ,which is held down by a Spring of such a strength that it rises at just below blowing- otf pressure G and allows the steam to press on the piston . This moves the arm I ,o n the top of which is a flat plate K ,and batfles the je t,so fi W that it is prevented from continuing to urge the re . hen the steam pressure falls,a spring (not shown ) brings the baffle back

g i a ain into its normal posit on . Brakes and regulators may be actuated from the rails by roller

‘ levers working on incl ined contacts,and steam may be shut off

’ Bw he ba n g [ I v0 WE w

3 5 — B R F R S E Fi . 2 STEAM E O 4 11 L MODEL g AK A 2 . CA .

over certain portions of th e line and put on again by suitable

v de ices too numerous to mention here .

-i Steam brakes are recommended for all engines of n . scales and a above,and in larger engines are indispensable . The di meter of be the m t l d the ram should about 3 of dia e er of the engine cy in ers . 2 Fig . 3 5 shows a jacketed cylinder worked by a cock on the v Th h back co er. e screw on t e under side of the jacket should be adjusted so that th e leakage is just sufﬁcien t to keep the jacket an h free of water . The cock d passages s ould be arranged so that the supply is drawnfrom the jacket,which is in direct connection with the boiler,and also in such a way th at the jacket may be d h draine . T e sketch shows th e handle placed outside th e footplate and the inclined dotted line corresponding with its full on ti th posi on ; e reverse inclination will release the brake . An

2 0 N 5 THE MODEL LOCOMOTIVE : I TS DES IGN AND CON S TRUCTIO . scale model undergoing such a te st but without rollers,the axl ebox being ﬁxed in the guides and the engine lifted and worked With th e ou for n steam brake . Free rollers may be employed showi g models working at exhibitions,compressed air or else an electro n motor bei g the motive po wer.

Co un ts

ma ﬁa

of term}: or {3 13

’ — m’ L m s L oco w n' va x a Fi 3 54 11 11. H ax x Tnsr x g. U S APPAR AT .

Roscoe displacement lubricators will be found the most con venien t for miniature locomotive cylinders and valves,an d may be ﬁtted to the cylinder covers in inside - cylindered engines as illus trated in Plate III .

— i 3 55 CONNECTI ON or W TE R AN D F U E L PIPE S m o m TE D E R . F g. . A N X 1 APPEN DI . 25

D N OR M N A URE LOCOM O E E SIG S F I I T TIV S.

N I X (See Folding Plates, os. II . to . )

A MO N N E N N SIMPLE DEL SHU TI G GI E .

au e 2 ih (G g 15 . ) Those who desire to build a model locomotive of the very simplest character for use on sharp curves cannot do better than adopt a

- difﬁ u lt four wheeled shunting engine as a prototype . The only c y with such a locomotive is the provision of a ﬁrebox of ample h n dimensions . If it is placed behind t e trailing wheel,it is eces m ffi saril y li ited. To overcome this di culty,it will be noticed that in the design submitted herewith the whole of the propelh ng — machinery 1 s placed l n front of the leading wheel all th e space

i firin behind the crank s then available for means of g. fi The boiler adopted is of the type described on page 54 ( g. To assist in the matter of draught a separate vertical flue tube th rough the boiler from the furnace is advised,this being shown on the sectional elevation,the flue cofi necting with what appears

- m to be a safety valve colu n . Th e boil er should be made from one piece of a solid drawn brass 2 t t e tube 4 in . diame er,three urn d brass castings serving for the f t At back and ront pla es of the boiler and the smokebox front. the smokebox a square hole must be cut in the under side of the the t ﬂu tube to communicate with horizon al e.

' r 1 in wo The frames may be cut from b ass or steel plate 1 3 . thick in t

1 in 1 ih g fin w - 2 . n is . strips, 1 . deep by 2 lo ( h ed size) The heel base h n 4 in th a n e i . e of t engi e is 1 . equid stant from the ends For le di g axle— springs not being used,because if such are employed in con nection with oscillating cylinders the distribution of th e steam will w t — a in d th e be interfered i h plain i . hole is all that is nee ed for h axl ebox axle. To lengthen the bearing, owever,a brass should be to t fitted t screwed the ou side. The trailing wheels are wi h spiral bearing springs (see fig. 64,page The cylinder illustrated in the general view is of the double acting oscillating pattern already described in Chapter VII. It may be fitted with reversing gear as shown,when a regulator will not be 252 THE MODEL LOCOMOTIVE : rf s DESIGN AND CON STRUCTION .

required,the three positions of th e reverse l ever in the cab,viz . , forward,backward,and centre,sending the model either forwards off t d or backwards or shutting the s eam from cylin ers respectively. Should objections be raised to th e adoption of an oscil latin g

- 3. ﬁ 1 54 cylinder, slide valve cylinder of the type illustrated by g. may — be substituted. The drawings are more or less self explanatory, and from a prac tical point of view there is not much to choose be tween the two arrangements as regards the m At running of the odel . . - ﬁ the right hand corner of g. 1 54 is shown a diagram of the arrangement of the crank in rel ation to the ‘ side

n h rods . The crank pi s for t e coupling or side rods must ° be at 90 apart ; therefore,to preserve the best balance it seems preferable to place the ° crank at 1 3 5 from each . A downcomer of either of the patterns described in Chapte r X d . may be use , preferably 3 5 — CROSS -SECTI ON or S TIN 6. HUN G the cast one as th en no back L o omorrvn c . W111 re ul r d plate be q e . It

- - n fiv 3 - i . i in s e n . should be attached by g . bra s screws at fi pitch, 1 3 to t th holes in the barrel connecting its water space tha of e boiler . Th e The tanks and cab are relatively simple matters . former are dummy structures,and do not h ol d water ; in this case they present an advantage,in that they can be fil l ed with asbesto s cotton,and so prevent radiation over a good proportion of th e v surface of the boiler . They also pro ide a protection against burning the fingers when manipulating th e model ,as they are t t th e t disconnec ed to a grea extent from hot er parts of the engine . The sides and ends of the side tanks are of one piece ; a top plate ma fit e d h d th may or y not be t ,as t e maker deci es. To protect e trailing wh eels from th e asbestos cotton,a splasher of tin plate

254 MO M 11 s N THE DEL LOCO OTIVE : DES IG AND CON S TRUCTION .

- t l - in The spirit tank should be made of tin pla e,and measures g .

- 2 in in . A x 1 . x ﬁ t the back two strips projecting upwards o should be soldered u . The strips should have a hole shaped like an inverted keyhole cut in them,so that each may be able to pass over th e head of a slightly projecting round-headed screw ﬁtted ff h h u into the rear bu er plank . The weig t of t e lamp wil l ca se the

‘ shank of th e screw to engage the slot of the keyhole,when the w head of the scre will keep the lamp securely in its. required position . The front of the lamp is supported by th e parts of the conducting pipes passing through the throat plating,which should t sufﬁ cientl l ow o w be ex ended y t allo this to be done.

A MO N - Y N N L V DEL SI GLE C LI DER TA K OCOMOTI E .

- ih scal d 3 4 3711 . e an au e (g 1 . g g . )

A model made to this design should ste am very well indeed,and, due to the short total wheel- base and the presence of the pony u t truck,traverse sharp c rves with the grea est of ease . A single cylinder is intended,although the model may be fi d tted with two cylin ers,as shown in Plate III . The kind of cylinder sold for model horizontal steam engines may be employed, a wedge- shaped piece of metal,to give th e cylinder the required inclination,intervening between it and th e footpl ating as sh own in h fi Th f o l a in e t e detail ( g. e otp t g at the end as far as the sid tanks— which,by the way,are imitation and do not hold water are should be of one piece to allow of this. The frames,if castings obtained,should be screwed to the footplates by the lugs provided, the necessary setting- in to allow of the swingin g of the pony f truck being given to them previously,the castings being lat . The horns are sh own cast solid with th e frame plates,and after th e axl eboxes have been fitted,vertical holes may be drilled and tappe d to receive the h orn stays,which should be flat strips of 1 1 in in in . t . x . me al about 1 . 1 5 and 4 long ’ Th e boiler is of th e Smithie s type,with a J_downcomer,and to imitate the prototype has a dummy Bel paire firebox casing This fitting is useful in that it preserves the paint at the hottest h e n d portion of t boiler a prevents excessive radiation . h 2 ih di The driving w eels are 3 . ameter and the leading wheels

6 HE MOD M V : rf s DES N AN D N S N 25 T EL LOCO OTI E IG CO TRUCTIO .

. 2 m ff ma as fi 91 1 . The spring bu ers y be arranged shown in g. , five page 88 . If two cylinders are employed, water tubes should x e w be employed. The saddle in the e ampl sho n in the photo graph is made by fixing the front and the back castings to the footplates and attaching the sides,which are made of thin plate, te l by counte rsunk screws . The front pla of the sadd e should con tain a stud for fixing down the boiler as in dicated Th e valve Spindle shoul d be supported by a guide as shown in the plan,the eccentric rod being pivoted to a movable block on th e spindle,a

- set screw holding this block in its proper position.

- E S RN M V . A MODEL NORTH A TE LOCO OTI E (Plate II . )

ih to the ot au e 2 ih le . o (Sca ,1 f g g , 1 . )

A fu rther step towards the construction of the more pretentious

‘ ’ o s e scale m del is depicted to a cale of half full siz in Plate II . The design is for a model of the North- E astern Railway Smith v 1 1 9 d compound locomoti e No . 6 to provi e a simple reliable work s h ing model,two cylinders only are advised . The e are of t e stock s ﬁ 3 58 ar pattern already referred to in de cribing the design g. ,and e attached to the main frames by a casing which completely encloses 1 h 1 in . th e cylinders,as t e 1 5 x cylinder usually procurable h as covers of very small diameter and cannot be used as they stand with out altering the scale appearance of the model. The covers of the cylinders should be ﬁtted with countersunk screws to clear the casing ends,which may with advantage be discs of thin brass,nickel - plate d to represent the polished steel

fi . cylinder caps of the original engine . The details ( g 3 59) also show how the slide bars may be fitted to the circul ar stufling-box of the ordinary pattern cylinder,the rear end of the bars being silver- soldered to a collar which sh oul d be bored to fit the stuffing box . To couple the eccentric rods to the valve spindle,holes in th e main frames are necessary,as shown by the frame drawings on the

S n l th e Plate . The frames should be plit horizo ta ly at front ends, lower portions being set in to give a greate r amount of lateral play to the bogie. ﬁ 1 The bogie is detailed in g. 77,page 8 ,and the safety valve

258 MO : rrs SIGN AN D N THE DEL LOCOMOTIVE DE CON STRUCTIO .

- v e same time with,for a gin . scale model,the comparati ely larg 2 1 in . heating surface of 4 sq . ,it is not necessary to encroach on

n o q x:

th e t s ac s th e a to wa er and steam p e of b rrel an undue extent .

I n d the ﬁrebox be at in eed,the crown of may least i . below the 2 9 DES IGN S FOR MI N IATURE LOCOM OTIVES . 5 centre line of th e boil er barrel without cramping the tubes (see ﬁ g. 360) The cylinders of the model (see full- size drawings in Chapter

-i 1 41 . 1 VII ) are g n . by 1 ,slip eccentrics of a simple pattern being employed,the sheaves being steel, and the straps and rods of gun metal cast in one piece,and attached to a rocker actuatin g the valves

above the cylin ders . The main frames are of the simplest character and have no h ornbl ocks,the extra thickness of the material making up for these ﬁ in tt gs. The bogie is worked out ﬁ on the principle described by g. 2 9 7 ,page 7 . The main spirit tank occupies rather more than half the back bunker and feeds a supplementary tank of cylindrical shape placed under the footplate s behind the

bogie . A force pump may be located in the left- hand portion of the bunker,th e suction of which should be connected to th e cross connecting pipe of the tanks,and the delivery pipe to the clack valve on th e back of th e boiler . The cab shoul d be entirely separate from the side tanks and bunker,and should have a hole in the roof with a cover which may be taken off during the running of the engine . If a double dome is

ﬁ 285 a e mployed (see g. ,page then the pattern of regul tor il t ﬁ 309 223 203 lustra ed in g. , page , and on page ,may be h e mployed,the andle in the cab remaining as shown on the Plate .

A MO L . DEL M IDLAND OCOMOTIVE . (Plate III )

l 11 ih au e 3 ih ca e . (S ,8 . ;g g , } )

t i ﬁ s 333 3 61 . The draw ngs, g . , ,and on Plate III ,represen a model M idland Railway four coupled express engine, the prototype 260 THE MO M : rrs S N AN D N S N DEL LOCO OTIVE DE IG CO TRUCTIO .

is - of which a three cylinder Smith compound . The locomotive, however,is intended to work as a simple engine,and with two out

- l in . li ﬁ s 1 3 9 side 3 x i cy nders (see g . and slip eccentrics and

- a water tube boiler,it will be found an excellent working model . The te nder has a double bogie,and holds the water and spirit sup

— One - ﬁfth s of mo e Fi 1 MODEL M IDL D L TIVE . i e 36 . g. AN OCOMO ( z d l . )

d v ﬁve t t plie . Se en or wa er ubes may be employed . This model may be made completely of castings,and can be very quickly u built p .

A MO SIN G - WH E EXPRE SS L V t DEL LE E LED OCOMOTI E . (Pla e III . )

i e ih . au e h (Scal ,3 ;g g , . )

By reason of the increased gauge o ver and above the scale

n - n - equivale t,a gin . scale si gle wheeled locomotive may be built

— - D ETAILS OF M D E L SIN LE E E LE D E X PR ES S L TIVE . 3 62. Fig. O G WH OCOMO

’ a - h el t hie with a fairly l rge sized w e . In conjunc ion with a Smit s

4 - h in . h in boiler,th e wheel may be as big as 5 wit a . outer s ell,

2 2 MO VE rf s S N AN D N S R N 6 THE DEL LOCOM OTI : DE IG CO T UCTIO .

engine . The larger diameter of boiler barrel obtainable by the omission of the lagging,whilst in some degree creating losses by radiation,allows more tubes to be used without reducing the steam and water Spaces above the crown of the ﬁrebox,and,together with better steam distribution,due to the adoption of the single eccentric

’ gear,renders the model,as a whole,not less successful than a more elaborate engine having all the reﬁn ements of modern locomotive practice.

A d 4- in point of inte rest in the esign is the use of one piece of . solid drawn tube for firebo x shell,boiler barrel and smokebox . The outside firebox is a casting (with foundation ring),and is riveted over a hole in the under side of the barrel,the back end smokebox front and front tube plates being turned flanged castings .

— MODEL LO D N D N R T -WE TE R TE N - E E LE D T Fi 3 64 A N O . g. . AN O H S N WH ANK

’ The fiel d tubes,which are five in number,and h alf inch in diameter,are screwed into th e crown,and cross one another,as shown in dotted lines,an alternative system of firebox water tubes h n being indicated on t e drawi gs . The boiler is provided with two longitudinal stays,both of which serve oth er purposes— one being th e blower tube,and the second the steam pipe which emerges from the regulator box on th en d in e backplate . The back of the boiler be g a turned gun metal casting,h as th e advantage of providing plenty of metal for affixing the boiler fittings,which may be screwed in to the back t pla e without the use of collars. Steam is collected by a long pipe having twenty h oles (or there

1 in u abouts) 3 ? . in diameter drilled in its upper s rface,the dome being merel y an ornament. Th ere is,however,no objection to a more orthodox arrangement S N S FOR M N S 263 DE IG I IATURE LOCOMOTIVE .

th e i l o to th e t t if maker w l g necessary rouble . To fur her ensure th e delivery of perfectly dry steam to th e engine— even at the expense of reduced pressure in th e cylinder due to th e th rottling th e e — a of st am coiled superheater is intended . The smokebox front is intended to be a solid iron casting with a dummy door and h inges,and should require no machining except on the ﬂange ,if cleanly cast,th e strip round th e edge of h h t the door and the inge straps being polis ed brigh . The m chimney,do e,and safety valve are brass castings .

The in h l - in t cylinders are H} . in diameter and ave é . s roke,and

r - a e screwed to a connector steam chest with four gin . screws,thus having a circular hole of the l argest size possible cut in it on th e t a th e bot om side . The circular door forms the be ring for bogie, an d h b - c to t e t in . is attached s eam chest y six g . s rews Into the circular steam- chest a stud is fixed,and as th e cylinders are inclined th e centre pop for drilling for this stud must be m r 1 in d th e a ked about 1 3 . behin the centre of boss on the cover,so that the centre line of the bogie will be directly under the centre line of th e chimney (see page This boss must also be fil ed parallel with th e rails,and should be flush with th e o t n b ttom edge of the s eel framing. The stud also should be drive in truly vertical,and n ot at righ t angles to th e centre line of the A i th e t a th e th e motion . deta l of radial ruck t rear end of 85 fi locomotive will be found on page ( g.

A MO C N R L I W Y . DEL ALEDONIA AIL A OCOMOT VE. (Plate VII )

h u . (Scal e,4 ih . ;ga ge,3 5 i )

‘ ’ M J M I n o h nd This design,for a miniature of r F . t s s third a largest class of Dunal astair locomotive,should satisfy th e model maker who desires to show his skill in workmansh ip,and at th e same time wishes to be possessed of a reliable working model loco A motive of moderate size,built cl osely to scale . s mentioned in th e

h - in t th bi ﬁrst chapter,t e . scale locomo ive is ra er a g engine, 1 f requiring curves of comparatively large radius ( 8 to 20 t. in th e model in question),and although such a locomotive can be made to pull one person easily,it is h ardly one which would be chosen

The s n th e t fr the for this purpose . de ig in major par is om pen 2 4 THE MOD M : I TS . S N AN D N S N 6 EL LOCO OTIVE DE IG CO TRUCTIO .

L h E . e the n of M r . Pearc , aut or bei g responsible for some of . the the engine details and arrangement of the tender . 3 9 in ma . The gauge y be laid 1 3 where the railway is out of doors . The engine vel y closely conforms to the prototype, th e most important deviation in the machinery portion being in th e diameter th e of cylinders . o f c lin By reducing the diameter y ders to {3 in . ,it is possible to

' get th em together with the slide - valves comfortably between the frames,and the relativel y small diameter will be compensated for 5 h c 0 l . h by arrying a boiler pressure of per square inc .

Fi 6 — - S LE C LED N I N I L L ocomorrv 3 5 A MODEL I N n. g. . i . CA A O A RA WAY

The frames, axl eboxes, and oth er details are described in Ch t V Ch x ap er . ,the cylinders in apter VII . ,and the crank a le by 1 1 1 . figs. 8 and 1 9 Th e boiler is provided with a deep firebox,but as oil fuel is intended,it may be shallower and have water tubes in the firebox, V h or t . as s own in Plate IV . in Pla e

A MO G N R V and DEL . . . (Plates VI

- i u e ih . (Scal e,i h . ga g ,3 5 )

To obtain a powerful working model with the exterior to scale in its main dimensions it is almost invariabl y necessary to ﬁx upon a l V has a m l e . prototype of ample size . In P at this been cco p ished,

- R . N . the engine chosen being one of th e latest G. ten wheelers ,

‘ n rebo n having a Wootte ﬁ x a d a very large boiler barrel .

MO s S N AN D N 266 THE DEL LOCOMOTIVE : rf DE IG CO STRUCTION .

1 1 - in - . in The cylinders are x 51 ,the usual diameter for a i . scale in Th engin e being 4 to g . e bogie wheels are slightly smaller than scale to allow them to pass under the frames when th e engine is on a curve ;but wh ere this is n o t a point to be considered,th e be wheels may larger,as in the original . With th e top row of tubes omitte d and th e ﬁrebox crown lowered over 1 m,th e cylinders being reduced in diameter to +3 or 5,a perfectly free ste aming engine having a large range of water wil l 1 Th e i be the result. heating surface will be st ll large compared with ordinary model locomotives of this size,and where the sup er 2 l - in t h eater is employed the . diame er cylinders may be retained, the maintained steam pressure falling in proportion to the re th e h t s h duction of ea ing surface . A will be seen by t e drawings, are h 1 24 Ch t th e cylinders of t e pattern described on page , ap er VII . , the steam chest being provided with a circular door or cover on the under side,this cover carrying the bogie (see page The main framing of the engine stops at th e ﬁrebox and is continued outside the trailing wh eel of the locomotive,thus al lowing h the maximum room for t e burner . Instead of using a casting for this frame,the laminated spring being a dummy and included in the one piece of metal,an alte rnative method of construction may be adopted,using sheet material throughout (see Plate The eccentric rods are long,and must be curved to clear the h h T axle of t e coupled wheel as shown in t e pl ate . he inter mediate valve spindle is supporte d by th e motion plate,and to allow of th e two enlarged ends,should be made in two pieces h the A screwed together as s own in plan . nother method of accomplishing the same object would be to enlarge th e circular

S th e - in part of the pindle where it runs in guide to 44 or g . diameter,lengthening the guide also,and forming th e forked end t out of th e circular sec ion . As th e pro totype is provided with a complex reversing gear and the wide ﬁrebox renders th e ordinary arrangement of reversing lever difﬁcul t, therefore the simple method shown on the drawings was adopted ,and instead of a notched quadrant in the cab,

l t - r a s ot link wi h a set wheel locking ar angement devised . The

1 m h i e About 3 1 0 s . of eat n surfac . q. g ‘1 i - i c l i der l d be ad i bl n s wou v sa . Oth erw se ﬁ u . y e S 2 DESIGN S FOR M IN IATURE LOCOMOTIVE . 67 reversing arm of th e weight-shaft being between the main frames

- 3 and the tyre of the front coupled wheel,a width of 1 3; in . only being available for the joint of the reversing rod and the weigh arm,a curved slot should be cut out of the mam side sheet on the

- t V to right hand side (see sketch on Pla e . ) make room for this t to j oin . The design having been prepared with an eye the cost of the model,th e dome is merely an ornament,and the regulator of a simple pattern . The best course with the higher firebox crown woul d be to use a proper double dome and either of th e regulator patterns described 3 5 2 3 fi s. 304 and g 0 on page 2 . The superheater is of the hairpin type,and allows great fle xibility of the pipes in the smokebox,as well as little loss by th e

th 'in a d friction of e steam its pass ge to the cylin ers . The smokebox front may be cast in iron in one piece and di ﬁrebox ﬁ d arranged to be rea ly removable . The may be tte with cross water tubes as shown,or with Field tubes as in other de signs .

’ A MO E ‘ F E N N I D L AIRLIE GI E . (Plate VI I . )

u i (Ga ge,35 n . )

To suit a model railway with heavy gradients and sharp curves, ° R W W h t M r . N . right of orwic some ime ago suggested to th e e l d h writ r the bui ing of a double bogie Fairlie engine. T erefore

e n I - A th . desig Plate VII is submitted as a worked out example . o f u 9 1 f p wer l model should be obtained,and curves of or 0 t. radius

- f o r in . t a za scale loco quite easily raversed. With the wide fireb ox the use of two burners may be accomplished,and an u r flue a xilia y very simply arranged . One of the side tanks may o th e araffin wa Th c ntain fuel (p oil),and the others the ter. e two b o ile r barrels should be connected by a single firebox,an d all th e

fi ttin s at th e 9 n g arranged the side of latter. Four 1 3 x L}i . cylinders e fl are suggested . The st am pipes should be of exibl e metallic tu bin g,and the exhaust pipes sh ould be similarly connected up,the en d of th e flexibl e tube being made of plain tube sliding in th e Th ul blast pipe . e footplates sho d be made to take a part in the con s truction of the frames . 268 MO L V : 11 's S N N S N THE DE LOCOMOTI E DE IG AND CO TRUCTIO .

A MO E F L TE N - W E E T K LO E D L O A ARGE H LED AN COMOTIV .

a VI (Pl te . )

Scal e ih au e ih . 3 ( ,1 g g , 1 . )

n h ﬁ w The accompa ying photograp ( g. and the dra ing

- - . u in on Plate VI ,ill strate a . scale model ten wheeled tank locomotive of ample proportions, and repre sents in miniature th e endeavours of locomotive engineers of to - day to provide the largest an d most powerful machin e th e loading gauge wil l

. E . Th e , V allow model is in I T its O main features,much M O th e h t C same as t a just O b IV L descri ed (Plate . , K t N ank), except A T that it is provided with

L a 3 1 in A a l gged boiler 1 . C S diameter of the same pattern as that depicted in th e ph oto on page 64,

n h h t t o w ic illus ra es a tender M engine of exactly similar A - design and siz e, and ’ Stephenson s link motion . The frames for this loco are described in Chapter

V see ﬁ . Th e . ( g

- driving wheels are 4gin .

diameter. The shell of the boiler

in is { 3 . and the seams are chain or zigzag, t 5 riveted wi h 3 4 rivets

270 MOD M : I TS SI N AN D N THE EL LOCO OTIVE DE G CON S TRUCTIO . enables the faces to be milled,and the valve,with its buckle,to be placed in position . The large cover,besides providin g for ﬁnishing the ports,allows the erector to see the valves durin g the operation n t b of setting,lighteni g presen labour and saving future trou le . Th e The centre line of the whole of the motion is horizontal. piston rod is guided by a single slide bar,the end nearest to th e driving axle being brought to a feather edge on the under side to allow th e connecting rod to clear it,and is afﬁ xed to a lug on a bracket from the main frames ; th e other end is supported on th e

m 11 -in e t and cylinder cover. The main fra es are of 3 , . mild st el pla e, axl box t instead of a radial e a pony ruck has been adopted. The bogie and bogie framing is of the orthodox pattern,and no l hi h further description of this seems necessary. The on y point w c may with advantage be noted is that the model is provided with means of adjusting th e weight upon the bogie spring (see page 83 , ﬁ s g. Such adjustment is of great importance,otherwi e the model will not work at all well upon the springs,and the appearance will most likely be marred by the footpl ating and frame not being parallel

- v The i. e. th e with the rail when iewed in elevation . back plate ( longest plate) of the Spring should have a steel bearin g pin hard soldered on to it at th e end,and this should rest in a hollow made t by drilling a hole right hrough in the box fork.

The upper part ‘ of the box should be drilled and tapped to h to receive the vertical eye bolt whic is pinned the equalising bar . To adjust,the spring is removed from the box and the fork turned one way or the other,so that th e length of the complete h anger is increased or shortened,according to requirements . The driving and coupled wheels are supported by an equalising e bar between them . The hangers are articulat d,and . are of similar construction to that used for the bogie .

ul 1 -in The footplates sho d be correctly cut to shape from 1 6 . stee l plate,and may be in two or more pieces,so long as the joints are made to butt to each other in a workmanlike manner . The square piece in front of the smokebox must be made separate, and should be ﬁxed to angle brass,which has been previously th e riveted to the main frames at proper level . It seems desirable that the backpiece forming the bottom of the back tank be made separate from the sides,the two side plates coming as far as th e D S N S F R I N 2 1 E IG O M IATURE LOCOMOTIVES . 7

c n l can entre li e of the trailing coup ed wheel . The joint be made very

v t i . c on eniently at his place,as the plates are only 1 n wide. The s cut c the c at ides will have to be to lear rods,crank pins,et . ,and points where they butt upon the main frames they should be sup o t r th e t O h h p r ed by angles iveted to lat er. ver the cross ead a ole must be cut,and a lid,which can be easily removed for oiling and t d ﬁ ted h at ending to the crosshead and sli e bar, t to t e space .

th e n f t. 6 in The diameter of the boiler of original e gine is 4 . , h and outside th e cleading a trifle short of 5 ft. W en settling th e outside diameter of the shel l this latter figu re was taken as the limiting dimension ; the absence of telescopic rings,separate firebo x sheet, butt strips, and other detail s which vary th e d iame ter at different points in th e length of a large locomotive boiler,enabled th e model to h ave a barrel which is appreciably

h « ih A . larger than t e scale size . llowing 1 all round for total th ickness of cleading sheet and lagging, the diameter of the a 4 in b rrel may be 4 . outside .

Th e t in h - 1 in longi ud al seam s ould be chain riveted at 5 . pitch, t 3 in with copper rivets abou 3 5 . diameter . The wrapper of the fi rebox will need to be pinched in to pass between the frames, 4 in t A in which are . apar . clearance of {a . must be allowed at i t the w fire o t 3 in this po nt,which limi s idth of the b x o 4 . It must be remembered that th e two bottom rows of side stays will h ave to have countersunk h eads . The inside firebox is shown on th e drawings with the upper part swelled out so that the maximum number of tubes may be n arra ged . The crown is elliptical,and is stayed by a peculiar arrangement of girders and direct stays. The girders which are in side,should first,after filing to a proper shape,be riveted and h fir bo I t t h th t sweated to t e e x. will be no ed t at e cen ral stay of

h - l all has for its support at the ead the safety valve boi er seating. Th is should be turned up solid,and have holes drilled around the

to th e - v u stay hole, allow steam to pass by to safety val e col mns . th e the The throat plate is shown joining inside of barrel . The fron t tube plate of the boiler is a casting in gun - metal,and has th e th e o t ﬂanges to take barrel and sm kebox wrapper pla e .

The tubes,nine of which are gin . outside diameter,the remain

1 e t ﬁxed th ﬁr x ing two being }ih . outside,are b s in e e bo tube plate, V ES N 272 THE MODEL LOCOMOTI E : I TS D IG AN D CON STRUCTI ON .

od i which sh ould be made from go brass plate i n . in thickness , 3 reduced at th e lower part and flanges to 3 2 in . ,by screwing with fi a t t a ne thread chased t per. The wa er ubes are six in numbe r, and are placed so that they will,with th e help of a small plate attached to the tube plate,form an excellent baffle for the flame s.

Th ﬁr b x 3 - in e u ut o n e ordinary e o stays,1 3 . diamet r,sho ld have n s th Th e t l difﬁcul t e inside only . smokebox presen s ittle y in con t d r t th e struc ion,and needs no detailed esc ip ion . The joints of drag plate,front tube plate and wrapper plate sh ould be carefully

- t e of made,so that the smokebox shall be air tigh . The front plat smokebox should be countersunk,screwed to an angle riveted to n d th e wrapper,a red lead joint bei g use .

o th e d ﬁ 305 u o The regulat r is in ome (see g. ,p. the reg lat r rod being of bronze,and requiring to be se t o ff over ﬁrebox,so th at n ta it may clear the ce tral s ys . Th e section of th e side tanks can be obtained readily from th e drawings ; the recesses for th e driving and coupled wheel shoul d be noted,and th e splash ers to hide th e trailing wheels in the

d th e r h - h d th cab will have to be provi ed . To ig t an one of e latter t the rack for the reversing lever is a tached . The reversing rod h it th e afﬁ x has also to be set ere,so that will clear splasher. To h t c ut th e tanks,which should,w en communica ion pipe,etc . ,are adrift,be capable of being lifted,with th e cab,bodil y from th e frames,stout angle brass should be riveted at th e bottom of the side sheets,so that th e screws may be driven upward through

th e angle edging into th em . In th e real engine the back tank is provided with water as well ' e in th e as coal space. This could not have b en arranged model without some trouble being necessitated when erecting th e engine and to en able th e oil tank to be made as capacious as possible,the th Th e n water space at this part was dispensed wi . two side ta ks

- h th e are connected by a gin . brass pipe,whic joins side tank by a special cast junction screwed by two set- screws to th e under side h h th e of th e tanks . Splas ers are s own for bogie and radial wheels ; as these,to some extent,l imit the ﬂe xibil ity of the wheel - base,if t 20 ft t the railway is laid with curves of less han . radius, hey h t t t may be dispensed with . T is de ail of construc ion as wi h oth ers which may be modiﬁed— depends largely upon the poin t of

274 M : I TS S N AN D N S THE ODEL LOCOMOTIVE DE IG CO TRUCTION .

th e view of erector . If he requires to keep the external appearance c l c l ,h e th m t lose y to s a e will retain e ; otherwise he will no .

Th e n c - f drawi gs are all reprodu ed one third ull siz e.

A M N N L M I IATURE TA K OCO OTIVE .

Gau e 1 0 in scal e 2 tu ( g , } ; , . )

On th e frontispiece and cover of this volume will be found illustrations of a miniature bogie tank locomotive to a scale of two to th e . e i h as 2 inches foot This ng ne cylinders x 4 ih . stroke (see page and was designed,built and in steam in a very

a t it was ﬁrst t u of cr short time f er ho ght . Th e d rivin W h eel s are

Fi 3 6 — A D E S I GN F OR 1 0 -I N E M TI . 9, T L E g A 1 . GAUG ANK OCO O V .

Sca e 1 fu size ( l ,1 , ll . )

9 in t th e h t a 1 40 r th e . in diame er, ea ing surf ce 7 squa e inches,and Th e grate area 80 square inches . link motion is detailed in Plate d I . t an t The gra e is very long, the boiler of ample diame er . Coal briquettes are used for fuel,and the smokebox arrangements are such that a white - h ot ﬁre can be maintained,and at the same

e al l rk r time a full head of st am,under conditions . The w o ing 1 l h h o pressure is 1 0 . per square inc . The engine is n w in regular service on a 200- yards track,and th e writer has repeatedly driven ad d fif n this engine with lo s upwar s of tee adults . The total gross amount th e engine will pull is 1 5 tons,and the highest speeds h fifteen to eighteen miles per our . A steam brake with a cylinder d th e h fitted 1 1 ih . diameter is employe , coupled w eels only being 2 5 DESIGN S FOR M I N IATU RE LOCOMOTIVES . 7

w t with blocks. A sight feed and t o Roscoe lubrica ors are em ﬁ 45 1 hi s. A 1 0 1 21 ployed . For details of t s engine,also see g , , ,

1 99,208,226,23 5,282,3 03,and 3 1 3 .

AN E L VIII S E . TATE OCOMOTIV . (Plate )

1 u (Gauge, 5 t . )

This design embodies the use of a cylindrical ﬁrebox and ﬁre h Th e th e l t box s ell . latter is eccentric with barre ,to ob ain a

3 0 — - E T N L TIVE D E R I 7 . TH E 1 0 I N G 1 . GAU A K OCOMO UN GO NG A ST TI R TE S T A ONA Y . larger number of ﬂue tubes and to keep th e crown as l ow down as h ul i . T e 3 5 n possible cylinders sho d be 5x . and the driving d m t c m 1 in . n A a wheels 2 i ia e er . radial tru k ybe employed for the trailing wheel ,and if th e driver is to sit on th e back of th e engine, a well should be sunk below the footplate for his feet,and th e boiler and cylinders sh ould be thrown forward at th e front as h c shown . Ot erwise the boiler may be pla ed six inches further 2 6 M : rrs S N AN D N S N 7 THE MODEL LOCO OTIVE DE IG CO TRUCTIO .

. - s n back and the wheel ba e of the driving and traili g wheels reduced . The design of the firebox renders th e use of link motion a simple matte r,and the motion may be protected from flying stones and grit by a plate fixed to the frames under the motion and parallel A to the surface of the rails . ny of the radial valve gears commonly used for this class of engine may be empl oyed instead of link motion,and th e whole of th e gear made get- at- able by being placed

outside the frames and wheels .

1 — A DE I N F OR - E X i 3 G l m S LE OD E L PR E ss L M TIVE . F 7 . M gl . S A i CA E OCO O

vanta es of th e t e— sh ort- cou e wh ee -base and on ﬁ rebox (Ad g yp pl d l l g . )

E AN PRI N T D BY N E I L L D L TD E DI N B URGH .