Oiiragm Lt` R2

ALTITUDE TESTING CHAMBERS NEWNES @V[Ig OiiragM Lt`r2 EDITOR : F. J. CA MM AUGUST 1949

A CONTROL -LINE JET-PROPELLED MODEL AIRCRAFT IN FLIGHT. SEE PAGE 346,

Studies in Electricity and Magnetism Elements of Mechanics World of Models Jet Reaction Power Models Woodturning Letters from Readers Model Engineering Practice Simple Electronics Cyclist Section CleVPS etc.,etc. %AOWE dips, stainless produced. clips, wehave bronze range ITSS,VOIS clips, ownspecification. steel theenormous your and size from clipto shape selection any inevery tiny design show a can yourdisposal. Herewe Department is at Research e-Aperience Our of clip-making (9-3 years

Two popular types. In range of sines to grip from

Delivery from Stock.

No, 80

No. 300 A drawing boardslip.

Platedfinish' delivery ( Stock. 4/- dovz. z. Plus P.T. The roost

informativepsstvefr:.:enrxedt-. bookhe n yet 2,.Wings 10/6 ".shed

Sole Makers :

HERBERT TERRY & SONS LTD. REDDITCH. London Birmingham Manchester August, 1949 NEWNES PRACTICAL MECHANICS 325

THE " ZYTO " I5in. MOTORISED SAWBENCH IFYOU TAKE PHOTOGRAPHS WITH TOTALLY ENCLOSED MOTOR GET THIS JOHNSON 1-20 TANK AND FOR CROSSCUTTNG, RIPPING, DEVELOP YOUR FILMS INDAYLIGHT MITREING, BORING, GROOVING, etc. You lose half the fun of photography if you do not develop Brief Specification: Saw -table 24in. x t8in., with rise and your own negatives and make your own prints.Itis much fall motion for grooving, etc. Takes cheaper to do the work yourself and you see your results 15in. saw. Long ripping fence with more quickly. fine adiustment: Heavy spindle bored to take dowel bits, etc. J-20 TANK, az illustrated below, is for all size -20 roll films.Holds h.p. motor provided. 10 -oz. of solution. Enables you to develop, fix and wash a Suppliedsinglethree-phase or D.C. current. filmindaylight. Price 211-. PLEASE STATE VOLTAGE. PRICE AND FULL DETAILS JOHNSON ADJUSTABLE TANK for amateurs who require FREE ON APPLICATION. a tank for more than one type of camera spool.This tank takes six sizes of film: 16 mm., 35 mm., x 21 x 21, 21 x 31 and 2'4 x 41.Price 2716.Ask for it at your dealers. SPECIAL OFFER For three pence in stamps we will send you a book on Home Photo- graphy. Itwillinterest all amateur photograph- ers. forittells how to developfilms,how to make contact prints and how you can do your own Pro of S. 2 YZACK SON, Ltd. enlarging. Thereis a THE " ZYTO " BENCH HAND- 11111r - chapter on takingpor- FEED DRILLING MACHINE Drills to centre of 8in. circle. traitsbyartificiallight. Chuck to table,71in. Hand -feed depth, tin. Mark your envelope clearly Weight, islbs. Practical Mechanics offer. Chuck capacity, o -)in. PRICE 57'- (carriage paid) .JOHNSONS OF HENDON LTD. LONDON N.W.4 S. TYZACK & SON, Ltd., 3LONDON,LE.C.1. Established 1743 Telephones: CLERKENWELL 8301 ,Ten lineal. Te!eg:arns: TYZGAR, FINSQUARE.

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s-7 Niltal0/10". Manufacturers of DRAWING and SCALE MODELS SURVEYING of every description INSTRUMENTS for every purpose SLIDE RULES Are you INTERESTED in . . . Model locomotives, railway equipment, ships (full -hull and waterline), motor -boats, sailing yachts, engines and boilers ;architectural, display and museum models ; drawings, castings and parts for the amateur model - DRAWING MATERIALS maker ? If so. . send Id. stamp for (BP/I2) " BASSETT-LOWKE PUBLICATIONS" a NEW Brochure giving details of all catalogues, booklets DRAWING OFFICE etc. devoted to models and modelmaking. Drawings, Castings and Parts supplied by Bassett-Lowke Ltd. are of the STATIONERY finest quality. BASSETT-LOWKE LTD ''"''x NORTHAMPTON A. Q, T14 0 TO N LTD LONDON SHOWROOMS: I12, HIGH HOLBORN, W.C.I. zEzzuving .9n4t/uunetzt Specialioti MANCHESTER .28, CORPORATION STREET. 41 GAR.TJIDE/T.MANCHEITER 3.I Visit our London arid Manchester Branches, where our staff isat your service. 326 NEWNES PRACTICAL MECHANICS August, 1949

,,,,,,,W.WIWAASS,WaY.M.V.V.VVV.N.,,,WAAVO.W1,,,Wkw..m,,,,,,,,, Largesstocks' I.C.S. TRAINED MEN bestselectionst L.1 and Bargains in Ex -Services Radio and Electronic Equipment Brand New in maker's carton. Brand New MINIATURE arein Greater Demand "SIROCCO " BLOWER, WITH SHUNT MOTOR 230 v. A.C. MAIN l MOTOR 27voltsD.C. 1.5 a. Not a convertecrimit 1/50h.p.3,000r.p.m.. operates from 230 than Ever-Maximumproduction continuous running,multi- A.C. mains.Single Phase, 5'o cs. A bladedfan,outletdia. beautifully made depends onhigh technicalskill,such 2lin. Size overall 7 x 5 x synchronous frac- 6in., mnt. size 7i x 5 x tional H.P.-miniature 4Iirs. on rack 16 x 12in. motor.Dimensions, asthat acquiredby I.C.S. Students with fixing screws, hody :overall length aluminiumconstruction. 2fin.; dia.2:in.; CLYDESDALE'S Spindle length_iim ; TENS OF THOUSANDS MORE PRICE dia. ;in; black crackle ' finish. TRAINED MEN ARE URGENTLY ONLY CLYDESDALE'S each.POST PRICE ONLY 17/6d. PAID 21!-each NEEDED NOW-BUT THERE IS POST PAID NO WORTH -WHILE PLACE FOR VOL -OHMMETER.OHMMETER. Brand New, Portable.E336, with Sling.Scale o-5,000 ohms, c -ho a. o -r 5 V. 0-3 v.Range o- yoo ohms, 0-5,000 ohms,6 ma. 6o ma. 1.5 v.In blackplastic case, size 37 x x 2.1in.Instructions on back. THE UNTRAINED CLYDESDALE'S POST PRICE ONLY 16/6 each. PAID Brand New in tropi- Brand New in maker's cartons. Ambitious men everywhere have succeeded through cal packing. Ex-R.A.F. MINIA- A UNIVERSAL MOTOR I.C.S. Home -Study Courses.So also can you. TURE ELECTRIC By simple external wiring, full data supplied, for 220-250 MOTOR volt A.C. or D.C. mains. New method gives better than E524,for 24 volts t/6 h.p.Ideal for light ben:h The man with_an I.C.S. Training in any one of the subjects D.C.Small dimen- work, a tin. spindle is available listedbelow knowsitthoroughly, completely,practically. sions:length 2.1in., (when the fan is removed) for diam. itin. driving.Motor Generator type .Andheknows how to applyitinhiseveryday work. 29, sized X 51 X 5;i11. CLYDESDALE'S 24 V.16 a.Output 1,200V. PRICE 200 ma. Acccuriancy Diesel Engines M ming Engineering ONLY CLYDESDALE'S S, 0;0 Using Draughtsmanship Motor Engineering 5/11 each PRICE ONLY 251- each Luc Engineering (State which branch) Motor Mechanic POST PAID CARRIAGE PAID Air Ern Vacuum` Drawing Office Practice. Motor Vehicle Elea All goods advertised or in our list can he ordered from any of our branches, in England rules Electrical Engineering Municipal Eng. and Northern Ireland. 01 direct from :_ Air-Cenditimn.ng Electric Power, Light- Plastics sum, G2LEAGIDGEOW ST. REcE.T5' Architecture ing, Transmission, Plumbing CO. LTD Architectural Drawing Traction Quantity Surveying CL IDESDALE Auditing Eng. Shop Practice Radio Engineering 'Phone: SOUTH 2706/9. Eoiler Engineering Fire Engineering Radio Service Eng. Send now for new Illu3trated Lists. Please print Name and Address. Pock -keeping Free -Lance Journalism Refrigeration ...... Luilding Construction Fuel Technology Sales Management Euilding Specifications Heating and Ventilation Salesmanship Eus ness Training Hydraulic Engineering Sanitary and Domestic business Management Hydro -Electric Engineering Carpentry Illumination Eng. Sheet -Metal Work Chemical 'Engineering Industrial Management Short -Story Writing themislry; 1. & 0. Joinery Steam Engineering Civil Engineering Lettering Structural Steelwork offer you more Clerk of Works Machine Designing Surveying Coal Mining Machine -Tool Work Telegraph Engineering for your money Colliery Examiner's Marine Engineers Television Technology Colliery Overman's Mechanical Drawing Welding, Gas and Elec. MINE DETECTOR AMPLIFIERS Commercial Art Mechanical Engineering Woodworking Drawing A complete R.C.3 -stage amplifier in Concrete Engineering Mine Surveying Works Engineering aluminium case with battery compart- ment. Less valves but chock full of And most of the Technical, Professional, Commercial and Civil Servica components,including r2 -IMidget Examinations; also U.C.T.A. Exam. in Salesmanship. transformer, ceramic button bases, condensers and resistors. BRAND4/6Post (I.C.S. students preparing for Examinations are coached till successful) NEW. Reduced in price to Free DUAL LOUDSPEAKERS ROTARY CONVERTERSType 195 Ifyouneedtechnicaltraining:ouradviceon any matter concerning A Parmeko to -watt speaker as used by in BLUE -GREY STEEL CABINET your work and your careerisyours fortheasking-free and without the Admiralty on board all types of craft. as illustrated. Input _.74.v. D.C. obligation. Two Sin. dia. P.M. Speakers mounted Let us send you our special free booklet on the subject -in which you back to back and complete with matching Output 230V.,50 C, S., too arespeciallyinterested. DON'T DELAY Make ACTION your watchword volumecontrol. Housedinblack watts Single phase. Complete moulded frame andfittedwith base withplug,leads,, clips,and fixingplate. Idealforallpurposes The successful man DOES to -day what the failure iz to o to callers.Add lot- for can. fittedwith3 -way15 amp. and pkg.if required byrail. socketandcontrolswitch. INTENDS doing to -morrow.Write to us TO -DAY BRAND NEW FOOT CONTROL SWITCH .10 just what you have been waiting for ... Carriage Paid. Use this Coupon and offered at a fraction of the original Slightly soiled (Exterior) Models cost. Made to Government specifications at £3 to o. INTERNATIONAL CORRESPONDENCE SCHOOLS LTD. fromheavybrasscasting,accurately machined, will take the heaviest load, and circular metal disc with 3 fixing holes Dept. 95, International Buildings, Kingsway, London, W.C.2 can be used to control machinery, model A connectingterminaliialsopro engines, etc.Ideal for the amateur and vided. THE WHOLE professional Carr. ASSEMBLY FOR ONLY10/ Pus Please send me the free booklet describing your Courses in photographer. ONLY22/6Paid Free INTERIOR LIGHTS FOLDING AERIALS A robust lamp approx. 3,1iin. dia., with A very useful aerial comprising seven pearl domed glass cover and fitted with Name Age sectionsof copper tube aerial, which standardB.C.fittingforlow poWer (USE BLOCK LETTERS) extends to 74. feet. The aerial folds downillumination. A heavyduty on -off Address to a compact parcel of approx. 2ft.length. switch of the push type projects through Each section is permanently connected the case. to the adjacent one by a flexible cable Black BRAND 7M Post running through the centre of the tube. enamel finish. NEW 'Is'Free Addresses for Overseas Readers The aerial is assembled by push -fitting M.O.S. NEWSLETTER - Australia :140, Elizabeth Street, Sydney. one section into another and the assembly the paper for the handyman. Pacleed Egypt :40, Shari: Malika Farida, Cairo. is painted khaki green.We supply in with genuine bargain items and useful Eire :Anglesea Street, Dublin, C.4. addition a solid rubber insulated base " gen."Send 6d. for specimen copy or India:Lackshmi Bldgs.,SirFherozsha Mehta Rd.,Fort, into which the aerial fits.This base will 5/- for a yea,r's subscription.

Bombay. - - fit anywhere asitis provided with a Terms :Cash with Order. New Zealand :182, Wakefield Street, Wellington. 33, Tottenham Court Road, i-ondon,VY.1 N. Ireland :26, Howard Street, Belfast. ICS MAIL ORDER SUPPLY CO., Telephone : MUSeum 6667-8-9. South Africa: 45, Shortmarket Street,. Cape Town. August, 1949 NEWNES PRACTICAL MECHANICS 327 MONTHLY NEWSLETTER Redbrook Works, Gawber, BARNSLEY. August, 1949. HAIL! 3

Perhaps the - hardest thing in advertising is to convey pride of achievement without betraying a vestige of smugness.However, we are no strangers to " P.M!' and hope to prove worthy of the confidence of a widening circle of friends." Friendliness " is the operative word in all our dealings, we are privileged to share the engineering hobby of countless enthusiasts at home and overseas. Our particular pleasure is the supply of first quality hand and machine tools direct to users, backed by policy of sound service. For instance, our Lathe Department concentrates solely on MYFORD products backed by stocks of accessories and replacements second only to those of the factory. Similarly, the same test is applied to every item of stock with the accent on speedy and safe delivery. A further step has been the provision of our Personae Hire Purchase Plan which operates on any transaction over f25 value ;a sane commonsense arrangement for those who wish to pay out of income. Space does not permit further details but we would like to extend this brief acquaintance. A copy of our house journal " Tool News " or " Current Machinery Quotations " will gladly be sent free on request (stamp will be appreciated) to any address in the world. Alternatively, should you have any immediate requirements, we shall be pleased to quote upon receipt of details. We look forward to hearing from you. Yours Sincerely TGARNER & SON LIMITED

Hand 8 Maclaine Tool Division

HOUSE TELEPHONES HOUSES SHIPS ASHTRAYS BOOK- WALL OR DESK MOUNTING ENDS SIGNAL CABINS RAILWAY Suitable for intercommunication between Office'. Workshops, Stores, Garages, Big houses, Kitchens. STATIONS AIRPORTS DOCKS etc. Each station consists of normal size Bakelite handsets as illustrated, and desk or wall mounting cabinet with built-in Selector switch, buzzer and RELIEF MAPS PLAQUES MODEL push. All stations can communicate with one another independently,Each installation is absolutely complete and internally FURNITURE INKSTANDS PAPER wired.All you do to Instal is to run the multi -core cable between stations, join green wire to terminal A, reds to Terminal B, blacks to terminal C, etc., etc. WEIGHTS MODEL FIGURES AND 3 station' installation complete with 50 yds. 5 core cable. 18/100.Ref. 318. 4 station Installation complete with 50 yds. 6 core cable, 28(1.0,0-Ref. 319. ANIMALS ETC. 2 station installation complete with 25 yds. 4 core cable, 23117/8.Ref. 320. Absolute satisfactMn guaranteed or money refunded. SIMPLETO HANDLE INEXPENSIVE =-_-_--KLAXON HORNS how 11.1.1. STRAP OPERATED.-Ideal for Boats. Scaring Crows, TheInstructionBookillustratedtellsyou Street Vendors -works signals for alarms. etc.List price. 88 8;0. our price, 25 Unused, perfect. to make such models as above, without special tools or in Sankey's. " Pyruma "Plastic Cement.This .AiNS/BATTERY MOTOR FITTED WITH GEARBOX. skill, Ideal for driving large -sized models or with gearbox removed for operating a small material, modelled while plastic, dries or bakes to buffing wheel, or similar. These motors measure 71in. x 311n. high, they will run off D.C. between 6 and 24 volts or from A.C. or D.C. mains, any voltage. Speed Is 2.000 stone -hardness,readyforpaintingaccordingto revs. approximately. Price. 15, Post free. Order item No. 134. instructions. Obtainable at local ironmongers, hobbies A ONE -VALVE RADIO RECEIVER If you are anxious to make a set for your den or shops and art material dealers. to listen in at night when the main radio cannot be used, then you will be interested in the One - Valve Radio Kit which we have available at the Get Instruction Book by sending 4d.in stamps to the exceptional price of £1,plus 26 postage and insurance. The set works entirely from dry address below batteries and gives good headphone reception on the medium wave band. The complete Kit consists of :Chassis, Tuning Condenser. Trim- mers, Volume Control. Valve, Valve Holder, small Condensers,smallResistors.FlexWire and Earphones. everything, in fact, except batteries. We also supply detailed instructions showing - you how to assemble wire, and work the Receiver. (Note -the diagram below is part of these instructions reproduced here to show you how clear the diagrams and instructions are.)This is an offer which cannot be repeated once all stocks have been cleared, so you should order by return of post. Itcannotbe YOU CAN MAKE A TELEVISION RECEIVERdeniedt hat PYRUMA there is a lot of work in making a Television Receiver, but if you are sufficiently keen, there is no reason why you should not be able to successfully complete a really PLASTIC CEMENT good Televisor which will give you and your family hours of enjoyment. We are certain that you could follow the diagrams if they were all presented In the same easy and straightforward manner, as the one of the One -Valve Receiver above; and this is the way we are presenting the data for our new Mark III Televisor. If you feel you would like to make this up, then send 7/6 Immediate!) for the the constructional data. Dept. 9 Even if you haven't any of the components. the total cost will be less than £20 and these can be purchased H.P. if desired. J.H.SANKEY& S ON,LT? PRECISION EQUIPMENT, (1)Electron House, WINDMILLHILL, RUISLIP MANOR, MIDDLESEX ILFORD Est. 1857 ESSEX 328 NEWNES PRACTICAL MECHANICS August, 19 49 IT'S HOME ENGINEERING WITH MACHINE -SHOP TECHNIQUE I CAW80/17; Buildyourownradio Guillotine for shearing metal ALMOST ANY- chassis and lot other gadgetsfrom r to2"and up to12" TN/tic 1V/TN forthe home ; construct long.Alsoattachmentsfor PRISTACON perfectworkingmodelsto piercingroundandsquare - FROM a yourownplans.Infact, create to your heart's content ;holes and for cutting circular RADIO CROWS you'll see your work materialise and rectangular slots as well 70 411 SORTS into perfect precision produc-as for bending metal to almost OF 1112701 tions.The PrestaconPress any angle.All with absolute GADGETS ./11 isthe instrumentthat,for accuracy. thefirsttime, brings home r. engineering to the handyman. PRESTACONPRESS, 55:-. Complete model making out- Prestaconisthe COM- fitwithworkingdrawings, PLETE Press with all neces- 84:-. Specialitykitsalso sary attachmentsincluding available.

MODEL ENGINEERING

Obtainable fromthe Toy Deportmentof leading Stores and Model Supplies Dealers

Illustrated leafletdetailing in full the scope of the PRESTACON PRESSavailable on request from

SoleConcessionaires : L. REES & CO.LTD. (Dept. 20), 31/35, WILSON STREET, LONDON, E.C.2. THE BRITISH MADE PRECISION SMALL TOOLS :lirMisOstrm Nurolus WILKINSON'S

ALTIMETER . , Reading to 20,000k.An accurateBritish instrument by OF CROYDON Smiths, Kelvin, etc.DiameterP,in.'Depth, 2)in. ii_ BRIDGES ,!'------, A.C. INDUCTION MOTORS. Single Convertible to barometer pressureswitch, etc. Made to top R.A.F. standard. , phase.1,425 r.p.m. All voltages. Ideal 516-' , for workshop (Post and packing, 6e1.) -,...._._, i and industrial uses. Heavy duty. Bt Wires HIGH POWER TELESCOPE Silent run- Itrilla are electron- ning. No ically hardened, and te Brand new. Ex -Army -Navytripleextendingtype radiointer- kiftcally checked and tented, Power approx. 40, object glass 50 mm.Ideal for rifle ference. to satisfy theort. rract- ranges from 25yds.to1,000yds.(.22 shotsat100yds. i111( seed, of the11 kleil- h.p., £6-5-5 easilyvisible.)Eminentlysuitableforbirdwatchers h.p., £6-15-8 1,1llkerI1.1 engineer. military and naval cadets, coastal observation and a hundred and one other uses. This telescope is a solidly constructed 5h.p., £8-7-0 PIVOT DRILLS instrument built torigid government specifications by Carr. & pkg., For drilling very small leading British optical manufacturers.Brand new, 101 - holes. Range of sizes: CONTACTOR 1N17'.A precision clock completewithleather case. Length closed, 11 ins., movernent 3IM. x 2iin. mounted on a 3 -stage .05 mm. (.002") to filter used for sending impulses by means .5 mm.(.0197'). open, 31i". £6 10 0 (postCarrying and packing, strap, 316 216.) extra. of a switch operated by the escapement. This valuable instrument is/fitted in a sound- proof case :12 or 24 volts.With thermos- FLAT DRILLS tatic control of heater to maintain constant Similar to pivotdrills. 12 VOLT ACCUMULATOR temperature. Brand new. 15/6. Range of sizes: .25 mm. Capacity at 10 hour rate13 A.H. to 1.75 v., capacity at THERMOSTAT SWITCH. Bimetal type (.0090")to3 mm. in sealed glass tube, 2Iin. x lin. 30 deg. cent. 5 hour rate 10 A.R. to 1.7 v.Weight 21 lbs.Fine value. 54- each. (.1181"). heavily made. Brand new. 1 50 (Carriage and MICROAMNIETER. Full scale deflection packing, 31..) 25mic:oamps, scaled 0-500. Dial 2(". STRAIGHT FLUTE DRILLS 57/6 Post free. Recommended for brass. MICROPHONE and HEADPHONE SKr. VOKES OIL FILTER Moving coil with switch.7/6. Range of sizes: .35 mm. 8' GOODMAN SPEAKERS In wall case (.0138")to3 mm. Heavy duty,suitablefor all types ofvehicles,1 Oin (Post and with transformer. 22/-. (.1181"). launches, etc. `60'packing, 113.) ROOM THERMOSTAT. Adjustable 45 to 75 Fahrenheit.42/6 each. STANDARD THERMOSTAT. Satchwell 121n.stem, SPIRAL FLUTE DRILLS FLEXATEX TUBING 0/250 volts A.C./D.C.. 10 to 90 deg. cent.35/-- Improved design for easy Brand new in 24 VOLT MOTOR with reduction gear and Mfr. 6in. lengths and ideal for fuel, oil. water, paint, etc.Outer vicaornrk-o.peit5at6ed suitable for ModeMode(.switches ejection of swarf. Range cover of strong P.V.C. enclosing thick reinforcing spiral and bonded P.V.C. on of sizes: .lm m.(0039") canvas inner lining.Ilin.,1 iiin., tin. bores at 17/6, 21/. and 27/6 (carriage paid.) COCKPIT LAMPS with obscured domed to 3 mm (.1181") glass for S.B.C. Bulbs.Brand new with switch.Elam. 3in.5/- each. VOLTMETERS. 0/300 A.C.Moving iron. SINGLE SPIRAL FLUTE DRILLS CHART BOARD 21in. flush.17/6 each.0/15 vt., For drilling to extremely I7in.square with hinged perspex sheet and elbowed TELEPHONE SETS at a fraction of their fine limits.Range of parallel arm,givingcompletecoverage. Board original cost, will operate up to 5 miles. sizes: .1 mm. (.0039") stronglyreinforced and the whole makes a 25/_ suitable for office, garage, farm, etc.Com- to3mm.(.1181"). ... plete with calling buzzer, batteries,etc. IL fine,light portable drawing machine. 5716 per set.75i- per pair. (Post and packing, 113.1 HIGH SPEED RECORDER, Marconi type UG9 with Klaxon geared Motor 220,240 Cluainable fromyourusual supplier; --,-. in case of difficulty write for name of your volts, 80 r.p.m. variable resistance. Westing- \ ae AERO SPARES CO house Rectifier type HTI5. etc.. £5-5-0. neareststockist. DetailsofBridges (Dept. 215) Complete List of Electrical and Radio precision Tccls and Speciality Instruments, \ Goods available. 411. sent on request. 71, HIGH HOLBORN, LONDON W.C.1 L. WILKINSON S. N. BRIDGES & CO., LTD., \ Tel.: AMBassador 4856(all depts.) Parsons. Green Lane, Leaden', S.W.6 204, Lowe,AdditcombeRoad Croydon August, 1949 NEWNES PRACTICAL MECHANICS 329

" THE MODEL ENGINEER " EXHIBITION AUGUST17,11 -27th 1949 Special Attractions include:

Enlarged competition section showing the year's best models Fully equipped workshop carrying out a daily programme of work Model cars, boats, and aircraft in action on the circular track Radio controlled itodels Working model railways with full scenic effects Steam traction engines of all types operated under working conditions Two passenger -carrying model railways. NEW ROYAL HORTICULTURAL HALL, WESTMINSTER, LONDON. Admission 2s. 3d. (inc. tax).Children under 14, ls. Weekdays 11 a.m. (12 noon Aug. 17)-9 p.m.

HIGH FIDELITY The Modelcraft. REPRODUCTIONPLANBOOKS MODEL OIL ENGINE 2/2 Anentirely new model engineering S. C. BROWN, Type ' techniquehasbeen evolvedfor making this mode!.Only tools that are in every Moving Coil Headphones supply home andmaterialsthatare alwaysto that High Fidelity Reproduction hand are needed. The model runs on air. EX RAF demanded for DX work, monitor- MAKE -A -CLOCK3/9 Pose 6 VALVE With Valves ing and laboratory purposes, etc. Most peoplewouldtellyouthatan SUPERHET " ordinary man," without fine tools and much skilland experience can't make a Easily converted to 296 OUTSTANDING clock. Well, the " Flipclock " is different BroadcastReceiver.2f6Post & Pckng. Complete with CHARACTERISTICS Many haVe been made onthekitchen valves. Full circuits and modification table with the help of this plan book. details -2/3. Aboveset,less valves, 101-post free. D.C. RESISTANCE 47 Ohms. A SIMPLE MODEL LOOM EX -RAF ALTIMETER contains Aneroid Baro- in Plus 9d. IMPEDANCE 52 Ohms at 1,000 c.o.s. 2/8 POST rich E; meter Move men t.gigo Post & Pkg. There is something deeply satisfying in SENSITIVITY, 1.2 x 10-12 watts at IIcc. handling a device yOu have made yoursel 12 ASSORTED MAGNETIC RE- .0002 Dyne/cm". LAYS for experimental 1A/9 which also does something.Ties, scarves, purposes. Post free. g tablemit,etc..canbemade onthis NUTS, BOLTS, WASHERS, perfect little working mode!. small sizes for model malt-7 /6 PRICE£5.5.OPER PAIR ing. Three gross assorted.gaI MIDGET TYPE GLASS, Descriptive Literature on request. BUILDING A GALLEON PRISM, beautifully 13/-POST FREE 1/6 TYPE' K' gund,ro perpair. This book has become aclassic and is EX-GOV. UNIVERSAL Your local dealer can supply. now knowntomodelmakers theworld POWER PACK, givingI20v. over.Plans for the Golden Hind, the ship H.T. 7v. L.T. ideal as an elim- in which Drake sailed round the world, inator and trickle charger.Can (prices be used on any voltage between \1.,,, *Fordetailsof other S.G. Brown Headphones are included. 9 0 -2 5 0 v.A.C./D.C. from 30;- to 77 6) write for illustrated Brochure "P.M." post free.41 /- * Many other planbooks are included in SEALED GLASS TYPE THERMO- the Modelcraft CompleteListfor1949. STATIC SWITCH which, for II- post free or from. your model Breaks automaticallyat 86 shop. lists over 603 items of vital interest deg. Fah. Post Free, 3/6 e to modelmakers. Telephone :Watford 7241 tliKW Mo. Write (Dept. K) INSTRUMENT CO.SHAKESPEARE STREET, WATFORD, HERTSMODEIALltA FT 244 HARROW ROAD, LONDON, W.2 77(1_1, Grosvenor Rd., London, S.W.I. 33Q NEWNES PRACTICAL MECHANICS August, 1949 (riff TO AMBITIOUS kirAri4 ENGINEERS This enlarged and entirely new edition of the valuable Handbook "ENGINEERING OPPORTUNITIES"

For21years this unique book has been a guiding light to Engineers all over the world.More

than r,000,000 copies have been distributed . . . there have been 104 editions.Still the demand continues !After months of research, we have been able to produce a better and .even bigger " ENGINEERING OPPORTUNITIES " packed from cover to cover with vital, up-to-the- minute information that every engineer requires-information you must have if you want rapid promotion, higher pay, and one of the many worth -while appointments open to technically trained men. 176 PAGES OF PRACTICAL GUIDANCE " ENGINEERING OPPORTUNITIES "explains the modern, quick way of preparing in WHICH IS YOUR SUBJECT? your sparetimeforrecognisedengineering Mechanical Engineering examinations, outlines hundreds of examination A.M.I.Mech.E.-CITY & GUILDS-General Mechanical Eng.-Maintenance Eng.-Die- and non -examination courses in all branches of sel Eng.-Sheet Metal Work-Welding- Metallurgy-Machine Drawing & Design- Engineering, describes the benefits of our Em- Refrigeration, etc. ployment Dept., and enables you to visualise Electrical Engineering A.M.I.E.E. - CITY & GUILDS - General a secure, better paid and more important position Electrical Eng.-Installations-Illuminating for yourself. Eng.-Electrical Science-Electricity Sup- ply-Meters & Measuring Instruments- Mains Eng., etc. We definitely Guarantee Radio & Television A.M.Brit.I.R.E. - SERVICINGCERTIFI- CATE-C. &G. Telecommunications- GeneralRadio Eng.-Radio Servicing- "NO PASS-NO FEE" TelevisionServicing-Sound FilmPro- jection-Electronic Eng., etc: B.I.E.T. has helped thousands of ambitious men. We can Production Engineering and will help you.It will cost you no more than a stamp to A.M.I. P.E.-Works Management-Fore- inquire, and in any case " ENGINEERING OPPORTUNITIES " is well manship-Staff Supervision-Planning Eng. worth having. It will reveal many opportunities you are now missing and, -Costing, etc. if you are earning less than Llo a week, will be of special interest to you. Automobile Engineering Make sure of your FREE copy by posting the coupon now. A.M.I.M.I. - CITY & GUILDS - General Automobile Eng. - Automobile Repairs - High Speed Diesels-Garage Management, ItIME .211N POST THIS COUPON TODAY !_-- etc. (Write if yea prefer not w ,at page) Building & Civil Engineering A.M.I.C.E. - F.R.I.C.S. - L.I.O.B. Please send me FREE and entirely without obligation a copy of the new and General Building - Architectural Draw- enlarged edition of " ENGINEERING OPPORTUNITIES." ing-SanitaryEng.-GeneralCivilEng. -Surveying-Specifications & Quantities -Heating & Ventilating-Painting & NAME Decorating - Plumbing - Carpentry & Joinery-Timber Technology, etc. ADDRESS PLASTICS - DRAUGHTSMANSHIP- AERONAUTICAL ENG.-FORESTRY SOME LETTERS AFTER YOUR NAME A.M.I.Mech.E. A.M.I.E.E. A.M.I.C.E. F.R.I.C.S. A.M.I.Struct.E. L.I.O.B. A.M.Brit.I.R.E. A.F.R.Ae.S. A.M.I.P.E. HUNDREDS OF OTHER COURSES (Tell us what interests you) I am interested in

(State subject, exam., or type of appointment that appeals to you.) BRITISH INSTITUTE OF ENGINEERING TECHNOLOGY 4I0A Shakespeare House, 17-19 Stratford Place, London, W.1 BIET THE B.I.E.T.IS THE LEADING INSTITUTE OF ITS KIND IN THEWORLD. August, 1949 NEWNES PRACTICAL MECHANICS 331 CTICALMEC Owingto thepaper shortage "TheCyclist," " PracticalMotorist,"and "Home Movies "are temporarily incorporated.

Editor: F.J. CAMM

VOL XVI AUGUST, 1949 No. 190 FAIR COMMENT Whitworth senior scholarships are for can- The Novelty of Patents THE death ofMrs. Charles Kingston By THE EDITOR didates who possess an engineering degree Welch recently and the celebration of or a higher national certificate with two dis- the diamond jubilee of the marketingpatent can be contested in the Law Courtstinctions, or are in the last year of a course of the pneumatic tyre remind me of a curi-and set aside, and this has often been done.leading to one of these qualifications.The ous position in patent law disclosedsoon So when the Patent Law was changed itannual value of the awards is £325, and they after the pneumatic tyre was launched on thedid not go quite far enough. A patent shouldwill be tenable for two years for a course of market. be allowed tolie open for a much longerfurther training in industry or for research Dunlop had patented his tyre in 1888, andperiod the grant is made to allowwork.Candidates are required to submit a it had not been on the market very longpossible contestants to state the basis of theirthesison oneofanumber ofsPecified before it was discovered that R. W. Thomp-opposition. Failure to do so' within thesubjects. . son had patented substantially the same ideaspecified time should disqualify them from-Whitworth scholarships . are for students in 1845.Thompson's pneumatic tyre was infurtheraction. The pending changesinwhose further education has been limited to connection with horse-drawn carriage wheels,patent law and procedure, which I explainedevening classes.Their annual value is£200, and they were actually marketed and sold as inapreviousissue,will go a long waythoughthisamount maybeincreased, a commercial product for a number of years.towards eliminating some of the anomaliesdepending on the cost of the course and the They did not, however, catch on, and theyto which I have referred. means of the holder.They are tenable for finally disappeared from the market. Whitworth Scholarships three years either in industry of at an educa- Some may wonder how it was that with tional establishment.They will beawarded only one other patent for air tyres on fileDETAILS of the Whitworth scholarshipson the results of the Whitworth Scholarships in engineering to be offered forcom-Examination to be held in April, 195o. at the Patent Office it was possible for Dunlop . petition in 195o were recently announced by Furtherdetailsof toobtainapatentwithout Thompson's the awards may be patent being discovered by the examiners. the Ministry of Education. obtained from heads of colleges of further The fact is that at that time an inventor Two senior scholarships and five scholar-.education or from the Ministry of Educa- did not have to prove originality, nor didshipswillbeavailablefor candidates oftion, Curzon Street, London, W.I. The Thus itBritish nationality who are not more than 26closing date for the competition is Janu- the Patent Office make a search. years of age.They are required to have hadary 15th, 1950. was possible for several people to patent the practicalexperienceinengineering before same idea and they were left by means oftaking up an award. litigation to sort out in the Law CourtsAvho New British Diesel Locomotive was the true and real first inventor.In fact, THE interesting news is announced by the unscrupulous people took full advantage of SUBSCRIPTION RATES including postage for one year Railway Executive that there is now this loop -hole in the Patent Law, and a poor under construction at the Derby Locomotive inventor aggrieved by this flagrant infringe- Inland - -- 10s. 6d. per annum. Works a new type of main line diesel loco- ment had little redress unless he -could find Abroad - - - 10s. 6d. per annum. Canada - - - 105. per annum. motive. in which the power from the engines the thousands of pounds necessary to fight is Editorial and Advertisement Office :" Practical transmitted mechanically to the driving a powerful company. Mechanics." George Newnes. Ltd. wheels instead ofbeing electricallytrans- Tower House, Southampton Street. Strand, W.C.2 mitted as in the majority of other existing Change in Patent Law 'Phone : Temple Bar 4363 Telegrams :Newnes, Rand, London. main line diesel -driven locomotives. It was the seriousness of the position dis- RegisteredattheG.P.O.fortransmissionby The locomotive will be operated by- four closed by the Dunlop imbroglio that virtually Canadian Magazine Post. engines,each capable of developing soo h.p. caused a change in the patent law.For, of Copyright in all drawings, photographs and articles published in "Practical Mechanics" isspecially It will have two driving cabs, so that it can course, the Dunlop patent was proved to be reserved throughout the countries signatory to the be driven from either end, and a 4-8-4 wheel worthless.It was the addition of the wired - Berne Convention and theU.S./I. Reproductions arrangement. edge to pneumatic tyres, plus the fitting of or imitations of ard of these are therefore expressly forbidden. By comparison withcomparable diesel the Wood's valve -rubber valve which forti- NOTICE TO INTENDING CONTRIBUTORS locomotives,the new locomotivewillbe fied the position of the Dunlop Rubber Co. THE EDITOR OF PRACTICAL MECHANICS is always lighter in weight and the power losses in The wired -edge tyrefittedto Westwood - pleasedtoconsider manuscripts suitablefor ofCharles publication in the columns of this journal. As a transmission will be less. typerims wastheinvention general guide, articles should be about 1,200 Kingston Welch, and Harvey du Cros, the words in length, although where the subject The locomotive is expected to be ready for founder ofthe Dunlop Rubber Co., who warrants it, the article may be extended to 2,000 trials in the early part of next year.It has words.Short articles of 500 to 750 words are been numbered to,too, and will have a maxi- bought up the Welch and the Wood's patent also accepted. which, for practical purposes, gained patents To avoid the possibility of overlapping, mum speed of 84 m.p.h. of addition to the Dunlop patent. intending contributors are advised to write Due to the comparatively lightload on in the first instance to the Editor giving a To -day an inventor states his claims and a brief outline of the article they Intend to the axles, the locomotive will be able to run very rigid search is conducted by the Patent write, andatthe same time enclosing over most main lineroutes and will be Office examiners before a patent is granted. details of their qualifications. readily adapted for a wide range of duties MSS. should be typewritten, using one side of If any of the claims have been anticipated the paper only, and double spacing.Preferential from heavy goods to high speed express in prior patents such claims must be struck consideration will be given to those MSS. which passenger services. out, or a disclaimer inserted. are accompanied by sketches and/or photographs, The locomotive is being constructed to the and these should be properly captioned. Even so, occasionally a patent is granted The Editor dOes not hold himself res- -design of Mr. H. G. Ivatt, chief mechanical to -day which islater found to be invalid. ponsible for the safe custody of manuscripts, engineer,LondonMidlandRegion,in but every effort will be made to return collaboration with the Fell Developments, It is not possible to sue the Patent Office for unaccepted contributions if a stamped and negligence. The invalidation of a patent can addressed envelope is enclosed.All corre- Ltd., and Ricardo and Co. place a company in a serious financial posi- spondence intended for the Editor should The system of transmission, as wellas be addressed :The Editor, PRACTICAL _ features, non.It launches its business upon what it MECHANICS, Tower House, Southampton various ancillary have been considers to be ahall -mark of originality, Street, Strand, W.C.2. patentedbytheinventor,Lieut.-Colonel namely, the granting of Letters Patent.A L. F. R. Fell. 332 NEWNES PRACTICAL MECHANICS August, 1949 Altitude TestinA Chambers Technical Details and Operating Notes By H.E. HATTER, A.M.I.E.E.

THE problems of high altitude flight arehigh degree of efficiency of great importance in connection withand instrumentation. military aviation and can be divided into two spheres, man and machines.TheLow_ Temperature man problem has been overcome in com-Effects on Materials mercial aviation by the use of pressurised The effect of low tem- cabins, but thissolutionisnot applicableperatures on some ma- to single -seater and other machines too small terials is remarkable. to allow pressurised cabins. Ordinary rubber will At zo,000ft. the pressure of the oxygen shatteronimpactand intheairislessthan halfthatatseasome metals will become level, and so a smaller amount is absorbed asbrittle as glass, while at each breath and, further, the oxygen is the difference inco- not so efficiently absorbed through the liningefficients of expansion of the lungs.The cold at high altitudes --can cause endless trouble. 67 degs. Fahr.at 35,000ft.-can be over-Apparatusmade with come by heated clothing, but the limit assimilar metals in close fit regards oxygen in theairisassumed atmay besubjecttoam- abouti8,000ft.to zo,000ft.,above whichbient temperatures of consciousness islost.The modern oxygenovertoodegs.onthe mask under the control of the wearer atground, and at tempera- alltimesandfittingcloselyaround thetures of -6o degs. and mouth and nose has overcome this particularbelowthedifferencein trouble. theirdiameters may

Fig. 2.-Main door of chamfer. Electrical equipment suffers in a similar way, greater clearances having to be provided to prevent sparking over and corona discharge in the rare air, heavy insulation being frequently required.In the case of electrical machines excessive wear of brushes has been found to be due to the extreme dryness of the air.Normally the moisture in the air would appear to act as a lubricant and reduce this wear. Many other problems can be tackled in suitable equipment chambers, such as. icing and fogging of windows, seals for pressurised aircraft and also super- charging problems. De Havilland Altitude Testing Chamber A very fine high altitude testing chamber in this country is that built by the De Havil- landAircraft.Co., which is capable of being evacuated to a pressure equivalent to that of operating at 8o,000ft., while the internal temperature can be controlled within the limits of +4o degs. C. and -7o degs. C. A general view, of the complete equipment

can be seen in -Fig.I, and to give a better indication of the sizeofitFig. 2 shows the large door being placed in position. The Fig. t.-General view of De Havilland testing chamber. overall length is 35ft. and the diameter tztft., but the internal dimensions are only tzft., the other being lagging.One end of the Investigationscoveringboth man andchange to such an extent that vital partschamberisprovided with asuitableair- machine can be carried out by actual flights,of gun -turrets, etc., may seize solid. lock to allow men to enter or leave the a method most expensive as regards time Lubricating oils and hydraulic fluids maychamber without loss of pressure, while to and money.The obvious solution to thisbe equally subjectedto such temperaturepermit large fuselage to be inserted the other is the testing at ground level in a suitablechanges with considerable effects on theirend of the chamber is completely removed, chamber where temperatures and pressuresviscosities to such an extent that they areas shown in Fig. 2. can be varied at will.The first tests wereuseless at high altitudes, and very extensive As can be seen from Fig.1, a number made averylong timeago,and muchresearch work has been needed to enableof men are engaged when a test has to take development work has been required to bringsuitable grades to be produced for use inplacv.Full recording and controlofall the modern altitude chamber to its presentaircraft under any conditions. gear is actually carried out from the control August, 1949 NEWNES PRACTICAL MECHANICS 333 wood boarding.The refrigeration system adoptedisnotmechanical,butemploys solid CO2,a method widelyemployed in the United States with great success.In this systemmethylatedspiritissprayedover crushed, solid CO2 which is contained in a large insulated cooling tank ;this tankis shown in Fig. 5 with the CO2 crusher unit mounted above it.At the bottom of the tank isa sump containing the cooled methylated spirit. Circulationofthespiritisfrom the bottom ofthis tank, throughagilled cooler inside of the chamber and back again to the top of the cooling chamber.The air inside of the chamber iscirculatedat the rate of 31,000ft.per min. over these two coolers.Sufficient allowance has been made so that the chamber can be cooled to-- 6o dogs. C. in 8o mins. and atthe same timeallowadissipationof8o,000

Fig.3.-Thecontrol desk of the De Havilland altitude t!sting charOer. _Vote the pipe entry gland in the right-hand corner. desk, shown inFig.3,andthispermitsthe chamber.Full provi- operation of all the valves for the refrigera-sion is also made inside for tion and vacuum systems to be worked byconnections for the opera- push -buttons,whileindicatinglightsandtors: electricallyheated instruments show pressure,rateof climb,clothing, oxygen supply and temperatures, etc.A further detachable unitintercommunicating tele- incorporatesinstrumentswhichmaybephone system.A 24 -volt required for one particular test only.Com-DC supplyisalsopro- munication between the operators inside ofvidedtoenableaircraft the cabin and outside is done by means ofunitstobe tested under loudspeakerequipmentand,should anoperating conditions. emergency arise, the internal operators have priority over any communication. Insulation A large number of components have o Theinsulationofthe enter into the chamber, and for this purposechamber is carried out by a special entry panel-the position of whichfitting a wooden framework can be seen in Fig. 3, and which is showntoprovideasupport for in more detail in Fig. 4-is provided.Thisthe thick kapok lining, the enables electrical connections, oxygen pipingwhole insulation then and other required services to be passed ins)beingfacedwith coda: -

Fig.4.-Pipeentry gland which enables electrical connections, etc., to be passed into the chamber. BTU. Intermediate temperatures are obtained by controlling the rate of circulation of the spirit. A considerable source of trouble in these tests is the excessive formation of ice, and to overcome this,air whichisallowed to enter the chamberisfirstpassed over a cooler so that sufficient'dehumidiaation is obtained to prevent excessive icing up.To simulate the tropical conditionssteam heaters are provided over which the airis circulated by the fans previously mentioned. rtifietalsitaglateinofaTtudeis obtainedbyte' -Useo,a- Aouble-actiui, vacuum pump with the capacity of ZOoott. per min.Control of this degree of vacuum is obtained by double sets of mechanically operatedvalvesgivingfineandcourse adjustment.By prior setting of these any degreeofrateofclimbcanbeeasily Fig.5.-Therefrigerating unit, showing thelarge insulated cooling tank, with the CO. obtained. Reduction back toatmospheric crusher unit mounted immediately above it. The tank contain; the crushed solid CO pressure is obtained by allowing fifiered air over which methylated spirit is sprayed. to re-enter at the required rate to simulate diving conditions. 334 NEWNES PRACTICAL MECHANICS August, 1949 maximum capacity of 49,000 cu.ft. per min. The double inlets serves to connect to the two ducts which are formed one by the floor and the other by the ceiling.Each duct is large enough to give a 9 sq. ft. area. Due to the large internal volume and the very rapid circulation of air there exists a considerable danger from fire because of the large amount of combustible cork used in insulat- ing, and td protect against this a complete Cog fire extinguisher installation of the automatic type is fitted inside. While both these chambers described have been of large size there is a considerable field for small units used for testing instruments and smaller components. Some of these are simple refrigeration equipments to provide varying degrees of cold, while others 'are

Fig. 6.-General view of the North American chamber.

Largest Altitude Chamber requirements of a capacity What would appeartobe thelargestof 500,000 BTU per hour altitude chamber at present in existence iswhen cooling 3,50o lb.of that built by the North American Aviationairper min.from- 90 Co. and in operation in 1946.The chamberdegs.F.to- toodegs.F. as finally constructed was made of steel plate,-Insideofeachheatex- but considerable investigation was made firstchanger is mounted a bat- as to the use of reinforced concrete.Theteryofelectricheaters, doubts as to the reliability of this materialthere being a total of 18-36 when subjected to severe changes of tem-kW units, permitting a total with vacuum, conditions,maximum heating rateof forced the final decision in the use of steel. 736,000 BTU per hour. The overall dimensions of the unitare The high rate of circula- very large,the shell beingr7ft. diametertion ofair over the heat by 53ft. long, built up of fin. plate withexchanger was essential to externalstiffeningatfrequentintervals,maintainuniformcondi- additionalreinforcements providedatthetions throughout t h e point of support.An idea of the overallchamber when holdinga dimensions can be obtained from Fig.6,fixed temperature.Further whichshowsthemaindoorinopenProvision is made by means position. ofducting. frointhefan The equipment associated with this cham-nutlet for delivery of ro,000 ber was designed to permit dive tests at thecu.ft. per min.atasuit- rate of 7,soo ft. per min., with an auxiliaryable pressure for icing and `arrangement to permit a reduction at the rateheat exchanger tests.Over of 20,000 ft. per min. Should any of thea very small area anair operators be in difficulties the ceiling limitvelocity of 15o m.p.h. can was set at 6o,000ft., equivalent to a vacuumbe obtained. of 27.8in.A temperature range was fixed at The main door into the - roo deg. F. with a top limit of +zoo deg. F.chamber isrift. square in thisgavea considerable margin for anythe form ofalarge box, future developments. Due to the wide rangeand this is shown in moreFig. 7.-Doot and air -lock unit for the testing chamber shown in of temperatures permitted this would appeardetail in Fig. 7.Inside of Fig. 6. to be one of the few chambers in which pro-this box constructionare vision has been made for humidity control,two smaller doors, one of which can be seensmall chambers of 2 or more cu. ft. in which and 'desert conditions can be reproduced asas an opening, and these form an air -lock forvarying degrees of cold, heat and humidity easily as fogs. Artificial conditions of snowenteringthe chamber. The door is pivoted, ascan be obtained within fairly close limits. and sleet can also be provided. seen in Fig. 6, and the counterweight shownIt should be mentioned that in some cases it As much work will be done on pressuris-there is a 15 ton steel block. Opening andis much more difficult to obtain satisfactory ation of cabins, air for the pressurising andclosing of this main door is done by meanscontrol of humidity and temperature com- heating is provided by atmospheric air, which ofa geared motor, rubbersealingbeingbined in a small chamber than it is witha isfiltered,dehumidifiedbyrefrigeration,adopted to make theface airtight. Themuch larger unit, due to the minute amount compressed in a special compressor free ofwindows, of which there are a number alongof water which has to be provided to raise water and oil, and finally passed to a receivereach side, consist of six panes of glass, thethe humidity because of the limited amount in which the requiredconditions can beinner pane being fin.thick of safety glassof air present. obtained. with five others 4in. thick with +in. spacing in which is contained a dessicant. Refrigeration The method of refrigeration adopted in thisVacuum Pump REFRESHER COURSE chamber is the same as in the previopsly men- A reciprocating pump of Jo° h.p. is pro- IN tioned unit, with the exception that methylvided forthe production of the required alcohol is used instead of methylated spirit.vacuum and has a displacement of nearly MATHEMATICS The liquid from the refrigeration system is3,000 cu.ft. per min., which may be compared passed to cooling coils which are mountedwith the 8,600 cu.ft. volume of the chamber. By F. J. CAMM. above and below the fan. The total faceThe fan is of the double inlet centrifugal 8/6, by post 9/- area of 47 sq. ft. was based on the designtype driven by a 15o h.n. motor, and has a August, 1949 NEWNES PRACTICAL. MECHANICS 335 2nd Article of a New Series 11`41D11)1111'

11.-BENCH TOOLS

filesvariesaccordingready for filing.There is a correct file for to the character of theevery class of work. metal on whichitis Each type of fileis generally suppliediti used, the amount of pressure exertedfour different cuts, namely, bastard, second for each cut, and the cut of the teeth. cut, smooth, and dead smooth.There are When filing a roughcasting,foralso rough and middle cuts, but these are less example, it may be necessary to use afrequently used. succession of files, such as a rough file Special handles are available for files and first to remove the major portion of itisimportant tosee, whatever handleis thestock,thenabastard file,used, that the tangiswell driven into or BEFORE explaining workshop processes gripped by the handle.A loose handle can itis necessary to deal with the tools cause injury if when using it comes off, and mentionedinthepreviousarticle. the tang is driven into the palm of the hand The commonest of all the workshop tools is with the full force used to thrust the file. the file, and these are made in a variety of sizes, shapes and cuts to suit various pur- Filing Faults poses. The usualshapesareflat,hand, knife-edge,square,round,rat -tailed,tri- One of the first faults encountered in filing angular or three -square, half -round and riff - is the dragging of the file blade backwards lets.Additionally, there are very fine Swiss over the metal on the return stroke, with the files, so fine indeed that they do not appear exertion of filing pressure.This is as bad as to have teeth.These are used for extremely to run a circular saw the wrong way round. fine cuts and for giving a burnished finish. ' Filing should always be done forward, never backward.Itis often difficult to convince the beginner, and sometimes even the experi- Types of Files and Cuts enced man, of the weakness of this practice The ordering offilesrequiresattention. of filing on the return stroke.The reason is Do not confuse a bastard file with a rough probably that the large number of teeth on file.They are two distinct types, the roughFig. t.-Typical model engineer's work bench.a file blade make the occasional fracture of file having about five teeth an inch fewerIt should be of such height that the elbow withone or two of them appearinsignificant. than the bastard type file.Also do not con-the arm bent just touches the top of the vice.Nevertheless,itcannotbetoostrongly fuse fiat files with hand files.Files for brass A drawer for tools is an advantage. emphasised that every tooth of a file is valu- are of a different cut from those used for able and does good work. steel.All files are made in varying lengths, The next common failingisthe leaving so when ordering keep this point in mind.thenahandfileandfinallyasmoothof the teeth without protection, when they A 6in.file,for example, would be almost file.In some cases it may be necessary toare put away after use or purchase.Thrown uselessfor filingalarge surface,say, oneuse a hammer and cold chisel to chip awayinto atool bag or drawer, they are almost more thanin. wide. The nature of the workexcrescences and roughly to level the surfacebound to come sooner or later into contact to be undertaken must decide the lengths, with hard metallicsurfaces, and thiswill the quantity and the type of files.A small result in cracked or fractured teeth.Each selectionisuseful to start with, adding to tooth of a file has a part to play in efficient them as the work progresses.Do not make filing, and whenever a file tooth is broken or the mistake of using one file for all metals,_ damaged, a point where no metal is cut is for tests have shown that the work done by created.In consequence, not only will more time be needed to complete the work in hand, but also excess labour cost will be incurred. It must be remembered that it is not a matter of one tooth only.If these bad practices are

Fig. 2.-Ball- pane, straight - pane and cross - pane hammer heads.Methods Fig.3.-T hr eepunches.Left,a of wedgingare round pin punch; centre, a taper drift; shown above. A handle wedged as on the right soon andright,acentre punch. Automatic Fig. 4.-Above, a raw hide hammer, used on works loose.Methods shown at the centre and leftcentre punches which do not need thepolished or finished partsto avoid marking. are best. use of a hammer are available. Below, a repousse hammer. 336 NEWNEF PRACTICAL MECHANICS August, 1949 indulged in, a tooth or teeth will go on each occasion, until soon the blade is but a jagged wreck of what it should be. Brushing the File Teeth It is always good practice to brush the file teeth carefully before the tool is placed aside at night or when its work is finished for the moment.Only a careless worker leaves his files with pieces of metal clogging allthe teeth.To leave them in this condition means that their efficiency will be seriously impaired when next they are put to work. Pieces sticking to file teeth frequently cause pinning, resulting in deep scratches on the work.If there is no other means of, preventing it, this can be reduced by thoroughly chalking the file, though inthisconditionitishardly likely to cut so freely.If a brush will not serve to eliminate the filings from between the teeth, the best plan is to rap the edge of 2 the file against the vice, which will probably 3 4 5 6 shake out the majority.Otherwise, a piece Fig. 5.-Various pliers.r, side -cutting pliers ; 2, round -nosed pliers ;3, long -nosed or of file carding will prove effective. When snipe -nosed pliers ;4, taper -nosed pliers ;5, gas pliers ;6, another type of round - filing wrought iron and steel, the best plan nosed pliers. is to employ a soft iron or copper scorer. with complate success for iron and steel willnon-ferrous metals.A sharper fileisalso If the files become completely clogged withnot meet with the same success if used onadvisable fora broadsurface,lesssharp dirt and grease, a wire brush should be used.brass. Steelisbest filed with second -cutserving for narrow surfaces.The new file This comprises a wooden backing to which filesrather than those with coarser teeth,should, therefore, be employed, in the first is affixed a piece or strip of file carding.Inwhileif,on occasion, an extrafinishis instance, for broad cuts on brass or cast efficient workshops, drawers are provided in iron, andi then only on narrow surfaces of which files may be placed with some protec- these metals, and on edges.No new file tive covering round them. should be put to work on edges' because The majority of files in ordinary use are the teeth bite into the metal too quickly and double cut, i.e., the teeth are serrated by a firmly and may be wrenched off, thus damag- diagonal cutting.Only too often the novice ing the tool. uses afiletoo large or too small for his The next use of the now somewhat worn work. For example, he will use a medium file should be on steel, and it will give better size 6in. to 8in. in a medium cut or second results here, as stated, than a perfectly new cut, whereas it would be far better to buy file. When itslifeis coming to an end it a join. second cut and a6in. smooth file. can be put aside for use on removing sand The first will enable him to eliminate metal sand scale from castings and forgings, a job rapidly, while the second will put a good that would rapidly destroy new files without finish on the work. any improvement in results.The scale on these parts is extremely hard, and as a rule only a rough finish is needed.The edges of Using a New File a flat file, rarely employed for anything else, When a file is new, itis advisable not to will efficiently perform this work. bear too heavily upon it with each stroke, as It has been stated that allfiling should this may lead to fracture of a number of be done in the forward direction, but this teeth at their bases.The correct method is does not mean that the worker must lift to file lightly until the fine points are worn thefileoffthe metal with everystroke, down, after which a greater pressure can be unlessspecialfilesare beingused. The exerted with the increasing bluntness of the principal point to watch is that as the file is teeth.If the fileis pressed too heavily at drawn back for the return stroke, no pres- the outset, it may be completely ruined.It sureisexerted on it.The most effective is likewise bad practice to employ a brand work will be done on the forward stroke if new file on a weld, where borax or some the fileis given a slight motion sideways, vitreous flux has been used, and it is equally alternating to right and left with every few unwise to use it on the chilled and gritty strokes. skin of castings.Itis more expedient to employ an already rather worn file for this Correct Method of Holding a File work, so that the hard scale can be filed off, One of the first things any beginner must after which the new file can be employed toFig. 6.-Hacksaws. Above, adjustable hacksawlearnis how to hold the file. -Bad habits finish off. frame ;below, two other types. acquiredearlywilltakeagreatdealof The correct method is, in short, to remove eradication later, and will cause much waste desired, the finer cuts will be found indis-of time and effort.The proper filing grip is the scale with an old file, then follow up withpensable. a bastardfilefor removing the main bulk attained in the following manner.Look for of the material, and to finish up with a 2in,Milling File for. Lathe Filing Work cut or smooth file, according to the degree For normal lathe filing work, a milling file of finish desired.Should it be necessary tois the most satisfactory, and it is sound policy end with a very finefinish, then a deadto retain this type of filespecially forits smooth file can be used. own work, carefully cleaning itafter each As statedinthe previoussection,the period of use.When good work is needed, rightfileshould be chosen fortherightit is bad practice to put a file that has been material.Thus, afilethat has been usedused for vicework on to lathe work, while the lathe file should not be used for vice work, A standard bastard file is more economical, as a rule, than a wider bastard file for the majority of work for which a bastard file isused.With identical weight applied,it files off a greater quantity of metal in a given period. The non -fibrous materials, such as brass and cast iron, callfor a sharper file than do wrought iron and steel.In fact,the reader should note ,that there are files spe- Fig. 7.-Hand-power machine hacksaw. cially cut for operation on brass and other Fig. S. -2i z vices. August, 1949 NEWNES PRACTICAL MECHANICS 337 terns are illustrated in Fig. 6, and of these the tubular one is generally considered the best, provided that it is of good make. In nearly every case the frame is made adjustable in length, to receive blades from 8in. to t2in. long, and the different methods of adjustment will be evident from the illustrations. Besides the main lengthadjust- ment, provided by moving the two parts of the frame or by sliding the handle along the backbone of the frame, there is a wing nut or similar adjustment for altering the tension on the blade.A certain amount of experience is necessary to judg$ the most suitable tension, but in general the blade should be so taut that there islittle tendency towards bending, and yet notso tightthatslight twisting while sawing causes it to snap. This matter is regulated to a certain extent by the the thick part of the file, allow it to rest on the work, with the first two fingers or the - - base of the thumb directly over the work. The handle is then graSped with the other Fig. 14.-Various types of shear. - hand, and filing begun. The hand resting on the work must not leaveiteitheratthe The usual width of hack -saw bladesis beginning or at the end of the stroke. lin., and the thickness .o25in.; here again, Files should be so gripped that the end however, thereare variations according to of the handle fits into and rests against the make.Additionally, there is an extra -thick - fleshy part of the palm below the joint of the pattern which is intended for slotting screw little finger, with the thumb lying along the headsandsimilarwork. One makeis topof the handle inthe directionofits obtainable as 8in. blades, 14 teeth per inch, length and. the finger -ends pointing upwards. and in four thicknesses from .049 to .to9in. When the jobto be filedisheldina Correct Use vice, the height of the holder from the floor In using a hack -saw itisfirst necessary is important. As a rule, the vice jaws should to decide on the most suitable type of blade, be on a level with the elbow of the filer.A according tothedetailsgiven above, and good average height is 42in. from the floor, Fig.I0.-Soft vice jaws or clams, used tothentofitittothe frame and carefully and this will prove suitable for the majorityprevent the serrations between thevice jawsadjust thetension. The blade should be of operators.If the work to be fittedis marking the work.Top left are made of tin orfitted so that the teeth point toward the front delicate,sothatthefiler need small and sheet iron ;top right of I8 gauge sheet brass;of the frame ;thatis,sothatthe cutis only move his arms slightly, or may need bottom left, of thick brass or copper ;bottommade on`the forward stroke. to move only one hand and arm, the vice right, of spring steel. Where possible, set up the metal in the should be higher.The reasonisthat this vice so that itis held rigidly and prevented makes itpossible for him to hold himselftype of blLie in use; this point will receivefrom vibrating.Hold the handle with the more erect, and also makes it easier for himmore attention later. right hand so that the forefinger points down to inspect the job.If, on the other hand, the blade.Hold the front of the frame with the workisheavy and bulky, callingforHack -saw Blades the left hand and take up a position similar considerable exertion,itssurface should be Blades are generally -made in three lengths: to that for filing, but preferably withthe below the elbow joint.In this manner the8in., loin., andain., and are of two princi-work at a rather lower level.It is generally weight of the body is brought tobear onpal types.One is hardened throughout theagreed that. the best rate of sawing is about the stroke of the file. width, the other having hardened teeth and a3o strokesa minute, but there cannot be soft back.Alternatively, the latter may beany hard and fast rule about this. Hack -saw Types a double -sided blade with a soft centre; this It is of the utmost importance to keep the The hack -sawisthe only typeof saw saw in a straight line on both forward and generally associated with metal working, but backward strokes,fornot only doesthis there is another type Which is widely used simplify the work but it reduces the chances for more delicate work,, and especially when of the blade being broken.Apply weight producinganornamentalfinishinsheet with the left hand during the forward stroke, metal.This isthe piercing saw.The use removing pressure when drawing the saw of both typeswill be dealt with, but the back. When the cut has been taken almost hack -saw claimsfirstattention. through the metal the downward pressure Ifasaw ofthistypeisto be bought should be reduced untilitis only that pro- there is a wide choice of patterns.As with vided by the weight of the saw. allother tools, the higher -pricedarticleis (To be continued.) the better value if it is intended for hard and continuous use.A few of the principal pat - Fig. Ir.-Small bench anvil. is widely used for sawing brass tubing, but amongotherthingstheall -hardback has a longerlife,of course, butis more brittleandtherefore less suitablefor the semi -skilled worker; the soft back blade is better when sawing in an awkward place, where there isdifficulty in keeping the saw in a perfectly straight line. The teeth of all blades are given a certain amount of " set "-that is, the teeth are bent slightly outward in opposite directions-so that the kerf, or cut, made is wider than the thickness of the back of the blade.This prevents the blade from jamming in its cut. Blades intended for use with mild steel have 18 teeth to the inch ;those for hard steel I 2 3 4 5 6 2 3 4 5 6 and brass have 22 teeth to the inch ; ,andFig. 13.-Further types of chisel.1, chisel for Fig. 12.-Types of chiseL)1, chisel for lightthosefortubing,sheetandlessrobustgeneral use ;2, chisel with cutting edge, slightly chipping ;2,chisel for' heavy chipping ;3, material have 32 teeth to the inch.Thesecircular ;3, side view of 2 ;4, diamond-poini round -nosed chisel ; 4, cape chisel ; 5, diamond - are general figures and there may be slightchisel as shown at 5 (Fig. I2);5, chisel for point chisel ; 6, chisel for working in close places. deviations from them in some cases. cuttingoil grooves in bearings ; 6, side view of 5. 338 NEWNES PRACTICAL MECHANICS August, 1949 - - A smallspring -loadedsteeringwheel controls the steering.This consists, in effect, of two separate make -and -break switches, so that turning the wheel 30 degrees to the left A Radio -controlled (when it reaches a limit -stop) operates the cps. relay in the transmitter and turn - mg to the right operates the 40o cps. relay. Four push -buttons control the ship propul- Model Battleship sion motor and the turret motor is switched en by means of a push-pull D.P.D.T. switch. The operation of both of these controls is as Further Constructional Details By JOHN J.CHANTRILL, A.M.I.E.E. follows: Associated with the push -buttons is an impulse motor similarto that used in (Concluckd from from pager 3or, July issue.) the ship but energised by the18 -volt dry battery. This has been modified by the ASIX -VOLT r5 ampere hour " Gel-cel " pentode as modulator ;H.T. toallstages addition of asix -position Yaxley switch so accumulator supplies current for'he is108 volts.The anode current 'of, each that it will " home " to any one of six equally three motors and the stud -switch solenoid, a stagecanbe measured by meansofa spaced positions-moving, -of course, in one two -voltsupply for valvefilamentsbeing switched milliammeter on the frOnt panel. direction only.The buttons are connected so tapped offthe same battery.A separate L.F. Oscillator as to " home " the impulse motor on to the switch is provided for the two- and six -volt This uses two PMzDX type valves and following positions: supplies, and eachisindependently fused, consists of a two -stage R.C. amplifier with Buttonr (" Stop ")-Positionr;But- Average sunning time on one battery charge output coupled back to input.The oscil- ton 2 (" Half speed forward ")-Position 3 ; is about six hours. lating frequencyisdetermined by a tuned Button 3 ("Fullspeedforward ")-Posi- H.T. forthe receiver is..supplied by a circuit connected across, the grid circuit of tion' 5 ;Button 4 (" Half -speed astern ")- miniature 69 -volt battery, with' an additional the second valve, one of these tuned circuits Position 6. 45 -volt battery in series, for, the supply to being provided for each of the threefre- Pushing the turret motor switch to the the anode -bend rectifiers.This latter, bat- quenciesused. Output fromtheanode " ON " position changes buttonsrand 2 tery,asitisonly called upon to supply circuit of the second valve is fed throughover to positions 2 and 4 respectively.(It 3 m/a for very short intermittent periods, is of the deaf -aid type.Bias for the output tetrode andrectifiersisobtained froma small x2 -volt battery made up from pen - torchcells. The receiverincludingthe acceptor circuits and rectifiers,isbuilt on a wooden chassis and is easily removed for adjustments,ifnecessary. Suppliesare picked up via an eight:pin plug and socket. Shore Equipment This is divided into two parts contained in identical carrying cases t4in. x Join. x 7in.The first contains the transmitter and L.F.oscillator, while the second contains thebatteries and controls, with compart- ments fortools,spares and an Avominbr. An eight -core flexible' cable connects the two units, Jones -type plugs' and socketS' being used on the cable ends. Transmitter Unit The transmitter (left)and the control box. The R.F. section of the transmitter uses a transformer to ,three volume controls, one will be noted that these 6, positions corre- aconventionalcrystaloscillator(LP2), associated with each oscillator frequency. spond to those on the stud -switch on the followed by two frequency doublers (LP2 Three relays contained in the transmitter ship.) and P2).The second doubler, whichis unit are used to connect the required tuned A six -point cam carried on the impulse - modulated, feeds the aerial via a single -turn circuit to the oscillator, and additional con- motor shaft momentarily closesa pair of coupling coil.The aerial used may be either tacts on these relays connect the oscillator contactshalf -waybetweenthe" home " a vertical 1 -wave or horizontal dipole ; both output, via the appropriate volume control, positions:these contacts supply current to types have been used with equal success. to the modulator input.Thus, the modula- the t,5oo cps. relay in the transmitter unit. Choke modulation is employed with a PT2 tionlevel on each toneisadjustable.A Thus, ifa push-buttonispressed or the fourth relay, which turret -motor switch moved from one position operates when any of to the other the control -box impulse motor the other three is will " home 7 to the corresponding position, operated, serves to apply and a pulse of 1,50o cps. tone will be trans- cut-off bias to the L.F. mitted for each position passed ihroUgh.It oscillatorvalveswhen followsthat,ifthis motor and thestud - no tone is being trans- switch aboard shipstartoffinthe same mitted;this prevents position, then they will keep instep and random oscillation and the stud switch will move tothe correct economises in H.T. positionto give the conditionsselected- by consumption. A moni- the controls.The stud -switch moves slightly toring jack isprovided faster than the control -box impulse motor, so so that the transmitted that in operation it pauses at each position tone may bechecked until the arrival of the next impulse. with headphones. This may 'sound a rather slow process, but in actual fact the most lengthy opera- Control Unit tion, i.e.,movingthe switchthrough This contains a two - five positions, takes less than two seconds. volt " Gel-Cel" accumu- General latorforfi 1 amen t The ship clips intoa wooden crate for supply, a ro8-volt H.T. transport,thiscratealsocontainingthe battery, an r8 -volt dry aerial rods for the transmitter and aspare battery for relay opera- stud -switchfortheship. Ithasbeen tionandbias,control operated for many hours and has proved, mechanism,andtools, after the usual " teething troubles,'to be etc. A switched meter perfectly reliable. No serious "snags " arose Rear view of the control, box. The impulse motor is seen at the top on the frontpanel duringconstruction,which occupied 15 left with the associated push -buttons (topcentre). The flat boxes measures L.T. and H.T. Months of spare -time work-most of this mounted on the inside of the opened. lid contain tools, and a selection voltages and total H.T. being carried out on the inevitable kitchen of spare parts. consumption. table. August, 1949 NEWNES PRACTICAL MECHANICS 339 Simple Electronics A Brief Expination ofthe TheoryInvolved DURING the war the vital importance the nature of the conductor, but for a given of " Radar " resulted in rapid strides By A. LINFORD material, the current is proportional to the inthescienceofelectronicsand, e.m.f.Thisfactissummarisedinthe during recent years, these developments haveIt will be understood that, when dealing withfamiliar Ohm's Law, which states that the been applied with success to the production these theoretical considerations,itisneces- ratio, e.m.f. divided by current,is constant ofelectronicinstrumentsforpeace -time sarytostart from the basic principles of fora given conductor.The constantis requirementsinalmcstallbranchesofelectrical technology. called the resistance of the conductor and is engineering. measured in ohms while the e.m.f. is measured The reasonsfor theever -widening usesPlanetary System in volts. which are being found' for electrical apparatus An atom consists of a positively -charged In practice, various forms of resistors, i.e., of this description may be summarised brieflynucleus around which spina number of conductorswithaknownresistance,are as follows:I.Purely electronic apparatuselectrons, in a similar manner to the planetsutilised ;the most familiar, of course,is a has no moving parts and hence there are norevolving round the sun (Fig. a).The elec-coil of fine wire, but rods of carbon are also source;ofwear. 2.Generallyspeaking,tronsare negatively -chargedand may beused (Fig. za).The latter material conducts electronic instruments operatesofast thatregardedasminuteparticlesofnegativeelectricity in the same way as a metal, but they may be regarded as instantaneousinelectricity.It should be noted that the termshas fewer loosely bound electrons and, there- action.However, when required, time delays" positive " and " negative " are used merely fore, a higher resistance for a given diameter. can be introduced into the electriccircuit.to distinguish between the two kinds of elec- 3. With electronic valves, it is readily possibletrical nature shown by the nucleus and theA.C. and D.C. to obtainvery great power amplification.electrons ;infact,it would have made no That isto say, a very small power inputdifference to the theory if the electron had So far only electric currents which flow can be converted into a large power output,been referred to originally asapositively - continuously in one direction have been con- which isdirectly proportional to the input.chargedparticleandthenucleusas a sidered, that is to say, direct (D.C.) current, By mechanical means, such power amplifica-negatively -charged one. but of course alternating (A.G.) currentis ti is not easy to obtain also used to a very great extent and, as the and necessitatesalarge name suggests, this form of current results number of moving parts. from electrons surging backwards and for- Tin Foil wards in the conductor. A generator of A.C. produces an e.m.f. -ye which, starting from zero, builds up toa Electron maximum or peak, fallsto zero and then in Paper becomes negative sign, reaching a maximum Insulation negative value, which has the same magni- (Dielectric) tude as the peak positive value, and returns to zero ready. to start on a new cycle.In the usual A.C. main supply, the cycles follow each other at a frequency of fifty per second. *ve Resistor Cnoke -AI-- The graph of the A.C. voltage variation Nucleus c3oaenser (a) (b) (c) has the same characteristics as a sine curve Fig. I.-An atom, showing (a) and the voltage can be expressed by the the positivenucleus andFis2.-Circuitcomponents, showing(underneath)thesymbols equation V= V sin.z:tft,wherefis negative electrons. -used to represent them in circuit diagrams. the frequency (say 5o cycles per sectind as mentioned above), tisthe time in seconds, 4. Nearly allelectroniccircuitsconsist of The planetary system forminganatom isand V. is the height of the peak reached by acombinationofresistances,condensers,held together by the electric force ; any twothe e.m.f. and is measured in volts (Fig. 3a). coils and valves, and these components areparticleswithunlikecharges,attract one Theeffectiveor" root mean square " mass-produced in large quantities.There-another and vice versa, thus the positively - Vr = fore, they can be bought cheaply from stock, chargednucleusattractsthenegatively -(R. M. S.)value of thevoltage, and once anelectronicdevicehasbeen charged electrons, thisattraction balancing 1/ designed,itsmanufacture, to a very greatthe centrifugal force of the electrons, so pre-When an A.G. voltage is applied to a resistor, extent, is a series of assembly operations. venting them from flying off at a tangent.the alternating current set up also varies in The -above remarks are not intended toIn other words, the charge carried by thea sine wave form. The peaks of current occur convey the fact that an electronic instrumentelectrons is equal and opposite to that carriedat the same instants as the voltage peaks and isalwayspreferabletoamechanical orby the nucleus and the atom, as a whole, isthe current issaid to be " in phase " with electro-mechanical one, but there are manyelectrically neutral. - the voltage.Ohm's Law still applies, pro- instances where an electronic device can per- In metals, some of the electrons are heldviding the R.M.S. value of both current and form the requiredfunction more quickly,together by weak forcesso thatitisnotvoltage are used in the formula. cheaplyandefficientlythananyother difficult to detach thorn from their nuclei and form ofapparatus.Infact,as isthethatiswhat happens whenabatteryis casewithallmechanicalandelectrical attached to the ends of a wire.The battery Voltage punit = Time of mechanisms, the choice of the most suitableapplies an electricfield(also known asa 'Peak Volts" I cycle type of apparatus finally depends upon thepotential_differenceoranelectro-motive particular application.For example, in some force) to the atoms. in the wire.This field V cases the risk of electric shocks or sparks, detaches some of the electrons and starts them Time which may cause afire or explosion in anmoving down the wire.This results in some atmosphere containing inflammable vapour,of the atoms which have lost electrons being may weigh heavily in favour of mechanicalleft with anet positivecharge, and these instruments, or even preclude any apparatus attract more electrons from the neighbouring Lead I which needs electrical power for its operation.atoms to restore the electric balance.The of Currenti It must not be overlooked that an electronic processis continuous anda steady stream Ofttottltainti valve may fail without any previous warn-of electrons flows down the wire and back ing, and this is a disadvantage which cannot through the battery.The battery functions be ignored. as an" electron pump," the process being Electriccircuits,andespeciallythosevery similar to that of a fluid being pumped making useofelectronic devices,tendto through a pipe.The rate of flow. of elec- appear somewhat complicated to all but thosetrons is measured in amperes and is referred who areprofessionalelectricalengineers.to as an, electric current. However, the principles of electronics are not The magnitude of the current produced, in (b) difficult to comprehend and the following isthe wire or other material by applying -given 3.-Graph showing an A.C. voltage, with a brief consideration of the theory involved.electro-motive force (e.m.I.), depends uponthe -currentit would produce in a condenser. 340 NEWNES PRACTICAL MECHANICS August, 1949

Capacity and Inductance capacity to be a low impedance to the A.C. A diode (Fig. 4a) which is the simplest The use of alternating current brings intowhile they are open circuit to D.C. type of valve, consists of a cathode and an play two additional properties of conductors, Coils of wire are used in A.C. circuits toanode, mounted in a glass bulb which has these being capacity and inductance. introduce inductance, which property resultsbeen highly evacuated. The cathode is a Capacity is the most important property offrom the relationship between electricity andmetal tube containing a heating filament. A a condenser, which consists of two plates ofmagnetism. When acurrentispassedcurrent passed through the filament gener- metal mounted close together but separatedthrough a loop of wire, a magnetic field isates heat, which raises the temperature of byaninsulatingmaterialordielectricproduced at right angles to the loop.On thecathodesurfaceuntilelectronsare (Fig. 2c).The commonest type of condenserthe other hand, if a magnetic field is directedemitted.The anode is a metal plate, usually is made by rolling together two strips of tinthrough the centre of a loop of wire, thenin the form of a hollow cyclinder, surround- foil separated by wax paper. any change in that field introduces an e.m.f.ing a cathode.When a voltageis applied round the loop. When an A.G. voltage isbetween the anode and the cathode making When an e.m.fis applied across a con-applied to a coil, the current flowing through the anode positive, the electrons emitted by denser, the plate on the negative side collectsthe coil sets up a magnetic field, which variesthe cathode are attracted by the anode, where electrons, and these repel electrons from thein proportion to the current. The variation they are collected. An electric current, there- other plate.As the number of electrons onof the magnetic field induces an e.m.f. in thefore, passes through the valve which then thefirstplate increases this plate becomescoil, which isin the opposite direction tobehaves as a resistance.This current, called more negativelycharged, while theotherthe original applied voltage. This reducesthe anode current, must be distinguished from plate becomes more positively charged. A the effect of the applied voltage, and the cur-the filament or heater current, which latter state is eventually reached when the appliedrent which flows is, therefore, smaller thanis used only to eat the cathode and is not e.m.f. cannot force any more electrons into would otherwise be the case. Hence, a coilpassed through the vacuum as is the anode the condenser owing to the repulsion of those has greater impedance to A.G. than D.C.A current. held there.In this condition, the charges,onpure inductance would be a short circuit to If the anode is made negative, the electrons the condenser plates exert an e.m.f. exactly D.C. but, in practice, a coil always has someare repelled by it and remain close to the equal and opposite to the applied e.m.f. andresistance. cathode, eventually falling back on to its sur- no further change takes place. As in the case of a condenser, the impe- face, so the anode current is then zero.This The time taken for a condenser to become property is used when the diode is applied fully charged depends upon the magnitude Anode Control Suppressor torectification,i.e.,for changing A.G. to of the current which is allowed to flow into Grid Grid D.C. it, and hence upon the resistance of the circuit Screen If an A.C. voltage is connected across a applying the e.m.f. ;usually the time isa - Grid diode through a load resistance, current only small 'fraction of a second.When a D.C. Cathode passes during alternate half cycles cf the voltage is applied, there is an initial rapid supply. This currentisin the form of surgeof current, and then the condenser Heater pulses, i.e., intermittent, but all in the same - However, when behaves as an open circuit. Diode Triode Pentode direction and it can be considered as a D.C. a condenser is placed into a circuit supplied current with an A.C. current of distorted with an A.G. voltage, it no longer acts as (a) (b) (c) wave form added to it.A choke is put in an open circuit but behaves as a kind ofFig. 4.-Diagram of the three basic types ofseries with the load and one or two conden- resistance, the action being as follows:-The electron& valve. sers are connected across the load. voltage first tends to charge the condenser in Due to the special properties of, these com- one direction, then to discharge it and startdance of a coil varies with the frequency,ponents, explained in the foregoing, the A.C. charging itin the other direction, so thereand the coil also puts the current " out ofpart of the current' takes the easiest path isacontinual flow ofelectrons back andphase " with the voltage ; the phase changethrough the condensers and the load passes forth from one plate to the other, resulting isin the opposite direction from that pro-a D.C. current.The reason for referring in an alternating current. duced by a condenser.The value of the impedance of a pure inductance is 2afl, whereto the choke and condensers as a " smooth- On A.C. the condenser differs from a simpleI is inductance measured in henries, and thating network'' will be apparent.(Fig. 5 (A), resistance in two aspects.In the first place, (B) and (C).) the current it will pass, using a given voltage,of a coil is R2 + (2f l)2 where R is the varies with the frequency ofthe voltage. D.C. resistance in ohms. The Triode Large inductance values are often obtained The next type of valve, in order of com- ; Volts by putting an iron core through a coil, whichplexity, is the triode (Fig. 4b) which incor- increases the magnetic field. Coils of thisporatesthreeelectrodes,thesebeing a type are usually called chokes (Fig. 2b) andcathode, an anode_ and a control grid.The (A) they are used in opposing sudden changescathode and anode are similar to those in a of current. A simple extension of the chokediode, but the control grid is a spiral of fine is a transformer, which is constructed in thewire, interposed between the other twu elec- Time same way, but has two (or more) separate coil trodes.The introduction of this grid causes Molts windings. An A.G. current passed througha considerable modification to the manner in the primary winding sets up an alternatingwhich the valve operates and considerably magnetic field in the iron core andthisincreasesits value. (19 induces an A.C. voltagein the secondary winding.If the two windings have differ- To explain the operation of the triode, it ent numbers ofturns of. wire,a voltagemay be supposed that the grid is made a Time change results.Thus, if a transformer has Volts a primary winding of atoo turns and a secondarywindingof5oturns,thenif 2o volts A.C. are applied to the primary, (c)i. to volts A.G. will appear in the secondary The power in each winding is the same, so that if one ampere is drawn from the second- Tim; ary, only half an ampere is taken from the Fig. 5.-Rectification of A.C. to D.C., showingprimary. The figures given above refer to a A-Half sine waves produced by a diode valve.perfect transformer, but since it is not diffi- B-The effect of adding a condenser.C-Thecult to make a transformer with an efficiency D.C. output after passing through a choke.of 95 per cent., verysimilarresultsare obtained in practice. Fig. 6.-Circuit diagram of a simple triode Ohm's Law must be altered, replacing resist- amplifier with battery supplier. ance by the impedance of the condenserThe Electronic Valve Having dealt with the partplayed byfew volts negative to the cathode, while the which has the value of where f is 2 f C ' electrons in the basic circuit elements, theanode is kept at a constnt positive potential operation of an electronic valve may be con-of a few hundred volts.The high voltage the frequency in cycles per second and C sidered.Most valves are based on the phen-on the anode still' draws electrons from the isthe capacity infarads. Secondly, theomenon called " thermionic emission," whichcathode but the grid, being negative, attempts current is not in phase with the voltage, thetakes place when a metal is raised to a highto repel these electrons back again. The peaks of currents occurring when the voltagetemperature in a vacuum. The heat energyresultisthat the anode current is much across the condenser is zero and vice versa. agitates the atoms- in the metal to such ansmaller than it would be if there were no (Figs. 3a and b.) extent that some of the loosely held electrons grid.If the grid is made more negative; the . .Condensers are often used for separating are thrown out of metal into the space sur-anode current becomes stilllessuntil the A.C. from D.C. by making them of sufficient rounding it. pointis reached when the anode current August, 1949 NEVNES PRACTICAL MECHANICS 341 ceases altogether ;thisis referred to as theThe Pentode momentum cal? ies them on. Due tothe " cut-off " point.Changes in the grid volt- Another valve, which isvery. frequentlyscreen's accelerating effect, the anode current age between cut-off and zero grid volts, causeused, is the pentode (Fig. 4c), having twochange produced by a given control grid changes in the anode current, which aremore grids, making a total of five electrodes.voltage change, is increased and amplification almost proportional. The extra grids, which are again spirals ofis higher. The importance of the triodelies in thefine wire, are placed between the control grid The third grid, known as the suppressor, fact that the grid itself, so long as it remainsand the anode. is connected directly to the cathode. It is negative to the cathode, does not collect any The control grid of a pentode modifies theused because, with a screen grid, the electrons electrons and Passes no current. Theoreti-anode current in the same way as in the striketheanodewithsuchforcethat cally, it requires no power to change the grid triode.The next grid is termed the screenthey knock more electrons out ofit. The voltage, whereas the changes of anode cur-grid and is connected to a constant positive" secondary " electrons would, ifthe sup- rent enable power to be drawn from thevoltage, a condenser frequently being con-pressor were absent, fly back to the screen anode.In practice, it is necessary to connectnected from the screen grid to earth or togrid and the anode might lose nearly as many a resistor or grid leak between the grid andthe cathode, to prevent any change in volt-electrons asitcollected.The suppressor the cathode, to prevent electrons lodging on age.The purpose of the screen grid istorepels the secondary electrons back to the the grid and causing it to collect a charge.accelerate the electrons which pass throughanode surface. The resistor can have a high value, however,the control grid and assist tlaem on their The method of operation of a pentode, and will not pass much current, so a lowway to the anode. In the process, somedescribed above, is the normal one and i, power input is sufficient to cause compara electrons are collected bythe screen gridused in the majority of circuits. However, tively large power variations inthe anodeitself which, therefore, passes a small current,other methods are also utilised ; for example, circuit. This is the basis of power amplifi-but most of the electrons are moving so fast the screen current is sometimes used to give cation with a triode.(Fig. 6.) by the time they reach the screen, that their the output power.

Scale Prevention Quantity of Initial Charge Additional Scale Prevention and us'd of Micromet charge of Micro - per day met per month 500 galls. 2.1 lb. 12 OZS.

Corrosion Control t,000 5 33 lbs. 2,000 to 3 I., Particulars of theMicromet Treatment Corrosion Control 250 galls. 21 lb. 12 OZ.

THE formation ofscaleinhot waterHow to Use Micromet 500 IA lb. The treatment is most conveniently applied 5 ,, systems is often a serious problem, s,000 TO by the installation of a Micromet dispenser 3 33 especially in districts where the water If the daily consumption of water is greater supply is hard.The presence of scale causesat some suitable point in the water system.than the maximum quantities given above, waste of fuel;increased maintenance and Ape from then two or more Micromet dispensers can cieaning costs, and sometimes actual damage storagerank. be connected either in series or in parallel to boilers and heating equipment. On the togivethe requiredcapacity,e.g.,two other hand, with soft water supplies, corro- dispensers with an initial charge of solb. sion of pipework and hot water tanks free each, would treat 4,000 gallons of water per quently occurs. Mcromet These problems ofscale and corrosion dispenser day for the prevention of scale.Smaller have been solved by the use of Calgon (sodium feeders, known asscale reducers, are also available.Thesearesuitableforprivate metaphosphate) in many water undertakings houses. and industrial plants. An alternative method is to put the Micro - In smaller hot water systems, such as are met in the cold water storage tank, preferably found in some hospitals, factories, pit -head in a basket made of perforated metal or wire baths, schools, hotels and private houses, it gauze, which can be hung over the side of is more convenient to use another form of the tank and suspended in the water.Unless metaphosphate known as Micromet, which the storage tank is easily accessible, however, is marketed by Albright and Wilson, Ltd., the Micromet dispenser is to be preferred. 49, Park Lane, London, W.I. The effect of Micromet treatment in hard How to Install the Micromet Dispenser water districtsisto prevent the formation of hard deposits of scale or " fur " in water The diagram shows how the Micromet heaters of all kinds, e.g., hot water boilers dispenserisinstalled.Thisisasimple heated by coal, coke or oil, steam -heated job and is usually done by an engineer or calorifiers,gas and electric water heaters. plumber. (Micromet is not recommended for steam - The dispenser is installed at some conve- raising boilers for which a ,special method nient point on the water main supplying the of water treatment using Calgon and other water heater, calorifier or condenser.The phosphates has been developed ;.see the book- point chosen should be such that the dispenser let," Phosphates for Boiler Water Condi- isreadily accessible and can easily be re- charged with Micromet. Two isolating valves tioning.") are fitted, one at the outlet and one at the In soft waterdistricts, where corrosion How the Micro - troublesreplacescaleformation,theuse inlet, as shown, and itis good practice to of Micromet will control corrosion and thus met Dispenser is fit a by-pass so that the water supply could installed ina not be interrupted in the event of the dis- lengthen the life of water heaters and pipes. To water heater A small vessel or dispenser charged with water system. penser having to be dismantled or repaired. Micromet is connected to the water main atWe can supply a dispenser (see diagram) some convenient point.The water passingwhich consistsof a gun-metal cylindricalRecharging the Micromet Dispenser through the Micromet will dissolve a smallvessel with connections to the water main It is necessary to replenish the Micromet amount of metaphosphate ;three or fourand an opening at the top for charging theregularly once every month.The quantity parts per million aresufficientto preventdispenser with Micromet. to be added is given in the table above.For the formation of scale.When corrosion is The size of the Micromet charge dependsexample, if a dispenser is fitted to a water the problem, greater amounts of metaphos-on the amount of water to be treated.Theheater to prevent scale formation and the phatc are required ;the amount is regulatedfollowing table gives a range of quantitiesdaily consumption of water is 2,000 gallons, by variations in the charge of Micromet. for the dispenser described above : 3lb. of Micromet shouldbe added each Micromet dissolves very slowly in water ; month. the grade which is usually employed dissolves Close the isolation valves A and B (see at the rate of about 30 per cent, per month. diagram) and open the filling plug at the top RANI FEARED'S POCKET BOOK ofthedispenser.Pourintherequired The rate is largely independent of the 'flow An invaluable work for all engineers responsible for of water over the Micromet. the installation, operation or supervision of engineer- amount of Micromet, close the filling plug C Medical authorities, hospitals, water engi- ing plant and equipment in works and factories. and open the air release cock D.Slowly neers and municipalities in Great Britain open valve A and shut air release cock D Of allBooksellers,6/-net, or by post616 as soon as water begins to flow from it. and America have satisfied themselves that From GEORGE NEWNES, Ltd. (Book Dept.), the presence of metaphosphate in drinking Tower House, Southampton St., Strand, W.C.2. Open valve B.The dispenser is now re- water is harmless to health. charged. 142 NEWNES PRACTICAL MECHANICS August, 1949 New Series W0001- 711P17110 The Lathe By FREDERICK JACE

for the hands to resist, and varying thick- neises of shaving and varying stress make Fig. 1.-ThemotorisedM.L.8.Myford this dangerous.Therefore the rest must be wood -turninglathe-an excellenttoolfor kept as close to the surface of the work as wood -turners. convenient. The wood -turner's restisquite different THEREis a considerabledifference indeed, that one may easily be constructedfrom that of the metal turner.The usual between the methods employed inby the amateur. designisshown inFig 3.It consistsof wood -turning and metal -turning, not The position of the lathe should be suchtwo main parts-the rest itself and its base- only as to the methods of cutting the work,that a good light will fall in front of, thewhich is clamped to the lathe bed.The rest which is, of course, rotated between centres,worker and on to thework. A windowitself, shown in the upper part of the figure, but also concerning the methods of mountingwith a northern aspect would be bestas has a rounded top edge for the tool to rest the work. In metal -turning, for example, the cutting tool is usually fixed in the slide -rest which is traversed along by means_ of a lead screw. Moreover, the cutting edge of the toolis mounted at centre height or just below it. With wood -turning, however, most of the cutting is done by hand tools, except in the case of mass production factories where the tool is fixed as with metal -turning. The cutting tools used for wood -turning are really wood -workers' tools, and the cutting angles are similar to those used for chisels,plane -irons,etc.Also thecutting edge of the tool is applied to the work con- siderablyabovecentre,andthecutting consists rather of a shaving action than a direct shearing action as with metal -turning. The wood -turning lathe is, of course, much simplerindesign. A goodcommercial example of a motorised wood -turning lathe -the Myford M.L.8-is shown in Fig.r, Fig. 2.-Front and sideelevations of simpletreadle -operated wood -turning lathe ; A, and where electric power isavailableitis standards ; B, feet ;C, upper ends of standards ; D,, bed ; E and F, bearings ; recommended that a lathe of this type is G, leather belt ;H, mandrel ;J,counterpoise ;K, board platform ;L, brackets used, for it saves the considerable amount of for platform ;M, lathe headstock ; N, tailstock ; 0; holding-doWn bolt, P, T -rest ; labour necessary when a treadle or foot motor R, socket ;S, T -restclamping wing nut ; T, pinching screw ; U, work mounted provides the power, and also one does not between centres ;V, tack centre ;W, tailstock feed wheel ;X, tailstock' clamping lever. have to acquire the knack of treadling and operating the, cutting tool at the same time.being free from the glare of sunshine whichon, and from there its surface slopes down-. Of course, it is possible to have an assistantcan be trying to the eyesight. wards away from the work.It is provided to do the treadling, but thisis not always with apost'which fits into a socket in the. desirable, as with certain work he would be Briefly, a wood -turning lathe consists ofbase, and when adjusfed for height and for in the way. a horizontal wooden or iron framing termedhorizontal angle it, is clamped by a set -screw. A simple wood -turner's lathe is shown inthe lathe bed, which is supported on woodenThe base can also be' adjusted to any angle Fig.2, and its various parts are named inOP iron standards, and carries the headstockon the lathe bed, and moved in or out to the caption.It will be seen that the con-and tailstock. The standards are provided withsuit the diameter of the work. It has a structionis of simple character,so simplebearings to carry the flywheel (in the casesocket, as shown, which receives a suitable of treadle -driven lathes) and also feet pro-bolt for clamping.Adjustthents for height longed at the back to carry the tail -pins for donot vary much, but some amount of thetreadlepivot -bar,and thesefeetareadjustment is necessary. Fig. 3.-The T -rest. I. splayed to form an efficient base to ensure On face -plate work, thatis,flatdisc - that the entire framework stands rigid andshaped articles,the top ofthe rest must steady when work is being performed on it.usually coincide with, orbe very slightly For additional securityitisalso advisablebelow, the lathe centre height, when the face tofix the lathe feet to the floor, either by,of the work is being operated on.In turn- means of angle plates or by, means of lettinging the edges of such work and in cylindrical them into the cement. articles between centres, the turner adjusts The lathe may be conveniently rigged upto any height he finds convenient, his own at the back with a bench or tableattach-height in relation to the lathe having some- ment, which is useful for keepingthing to do with it.Usually the top of the chucks and other small appliances at hand. 'restis kept a little above the lathe centre Turning tools cannot be used without aheight. support or rest for them to bear on, for The T -rest P which supports the turning the downward pressure on the cutting edge toolisadjustable for height in the socket is much more than could be resisted by theby means of the pinching screw T, and the hands alone.The work, of course, revolves socket R is also movable both longitudinally towards the operator, and the support should and laterally . tosuitthework, whichis be as near the cutting edge as possible.Iflocked by means of the wing nut S. too far back there is more or less leverage (To be continued) August, 1949 NEWNES PRACTICAL MECHANICS 343

Studies in Electricity anc. Magnetism "Maximum Power" High -resistance Load Constant -voltage Sources High -resistance Load ICAME across a hoary old problem the By H.REES,A.M.I.EE. other day-one of those that constantly Suppose we gototheotherextreme, crop up in one form or another. current is approximately 1.5 volts-:- i ohm=connecting ahighresistanceacrossthe Someone had readthata" generator " 1.5amperes(stillforgettingeffectslike terminals,i.e.,moderately high-say 1,0o0 (an " imaginary " one of a type never foundpolarisation). ohms. in practical work !) would supply " maximum" The current discharge would now be quite current to a load, if the resistance of the loadNo Dropped Volts small-a mere 0.0055 ampere or 5.5milli- was made equal to the internal resistance of But 5.5 amperes in a wire of zero resistanceamperes (actually alittleless).The drop the source. will cause no voltage drop, and no conversionacross internal resistance will be somewhat Whether or not this was the actual statementof power intoheat.The currentisataless than 0.0015 volt.We arc getting almost made in a book, I cannot say.As it stands,maximum, but encounters no opposition inthe full 1.5 volts across our external resistance. I daresay, you can easily see why the theorythe external circuit :no volts are " dropped " But it does no good from the power point isridiculous. in the short-circuiting wire, and no energy isof view.There are plenty of " volts "-as A battery-and some types of " generators "expendedindrivingcurrentthroughit ! many as a given battery can supply-but the -or, generally, any " supply source," willAlternatively : currentisnegligible. deliver greatest current when the two terminals Watts = volts x amperes Watts = volts x amperes, which works out are short-circuited with a piece of wire-a --(amperes x resistance) x amperes to something like o.0025 watts or 2.25milli - highly foolish proceeding ! =(amperes)= x resistance watts. =PR. This is hardly " maximumpower," " Maximum Power " R= o, so the power isnil, however largecompared with the 51 watts wasted 'nternally What was probably saidisthat, under under short-circuit conditions. certain conditions, the power in a circuit will Small dry cells cannot be expected to deliver be maximum when external resistance - the much power, but itis possible to obtain a internal resistance of the source. more impressive figure than this-at least, That isa very different principle.As I for brief intervals. have often explained to readers :Power= iL volts x amperes,though,ifthe" volts " can be kept constant, greatest power will be r The " Optimum " Load Resistance the same as maximum " amperes." The foregoingsuggeststhere must be Hencethereservationabove," under a " best " or " optimum "load resistance : certain conditions."The principle applies to one not too small or too large, but of an apparatus whose output voltage isfar from (a) (b) exact value which will give maximum product constant ;wherealargedrop occursin of volts x amperes. internal resistance ;or where, therefore, the P = r (Optimum bad While difficult to carry out an experiment terminal volts fall rapidly with load current. on ordinary cells, Fig. ib shows a set-up for In such cases, largest current would be got verifying thefact. undershort-circuitconditions.But,then, Watts Starting with afairly large value of R, almostallthevoltswouldbe dropped Output readings of terminal volts (V) and amperes (I) internally,leavinglittle" watts "inthe are taken for various load resistances, and outsidecircuit. multiplied to give the watts output. Let us look at a typical example. R might consist of separate known resist- (c) LoadResistanceP ances, ora decade box where values are Dry Batteries indicated.Short -perioddischargesshould In Fig. la is shown a single " cell " hav:ngFig. r.-Is there an " optimum load " whichbe made on the cell by closing switch s only an internal resistance r = i ohm. will take greatest power from a battery or aduringthebriefintervalswhentaking Primary cells (" dry," or" wet," Leclanche,generator ?The question is discussed fully inreadings. etc.) have resistances of this order-much this article. A variablefactorwillbetheinternal iftheybecomereally" dry "or resistance r.If the e.m.f. is accurately known more, in the firstplace, any changes of internal otherwisedeteriorated. Also, " internalthe amperes. The " volts " referred to are resistance "isnota very constant figure, resistancemaybenotedbyusingthe the volts dropped across a resistance, which relation : but varies with the state of a battery, polari-is here nil. sation, and so forth. But the battery itself has t ohm of internal internal resistance, We shall suppose ouri ohm to be theresistance-the resistance of the electrolyte re.m.f.-terminal volts same at all load currents. and chemical constituents. amperes discharge First, let us inquire what sort of results Hence the whole of the e.m.f. (1.5 volts) A power curve (Fig. rc) of watts output might be expected if we shorted the terminalswillbe dropped internally,indriving5.5 against loadresistance R would show (if with a piece of wire of zero resistance.Everyamperes through i ohm.The heat generatedmeasurements could be accuratelycarried piece of wire has some resistance, but it caninternally will be the equivalent of a powerout) that the power isa maximum when be o.000 . . .something of an ohm-nearof 5.5 watts. R=r :the optimum load is one whose resistance enough to zero, compared withi ohm, as This is a " maximum power "-the greatestis exactly eqltal to the internal resistance of the will make no difference. power which can be lost in internal resistance !supply source. If we had an ammeter in circuit, it wouldWe would hardly buy batteries for verifying Note, however, that this curve falls off slowly show maximum current.Thus, if the e.m.f.that fact experimentally, so let us inquirefrom the m iximum-or isfairly " flat "- of thecellis1.5volts,theshort-circuithow toget maximum energy expendituremeaning the power will not be much less than where we want it-in the external circuit.the rt aximu n if, for example, R= 2r-twice 'n' Cells ConcentricLines /n ward Outward _A_In Series Around One Field Field Fig. .2(left).-Methods (b) Conductor and (c) of grouping primary Concentric Lines cells are apt to cause a lot Of Force of trouble owing to unequal Clockwise sharing of load current, but are sometimes used for supplying larger currents thanis possible with (a).Here ttv EMF: Per Cell .e are interested in " maximum Curi..;;;i`,,... lot. Res.:: =r power "output. Direction -/-

- + Fig. 3 (right).-More" Fun- (a) damentals" :Findingthe Inward Outward (a) (b) (c) polarity of a magnet. Field Field .344 NEWNES PRACTICAL MECHANICS August, 1949 the internal resistance.Thus, the resistancevoltage source.The same istrue of d.c.Magnetic Polarity of Coils need not be very accurately adjusted to get agenerators, etc.,havingconstant -voltage When drawing coils wound on iron cores, power near enough to the maximum. characteristics. we may show complete turns with current - We may say that such sources will deliverdirection, as in 3b and 3c, or imagine the wires " maximum power " if a load resistance wascut in section as in 3d and 36. Arrangements of Cells connected across the terminals equal to the In this latter case, a + denotes the tail -end If you have a number of cellsavailable internal resistance. of an arrow-a downward current ;. shows a (Fig. 2) they may be arranged (a) in series, Theoretically it is perfectly true, but no Onecurrent coming towards the observer. At end (b) in parallel, or (c) in series -parallel. would dream rof connecting such a " load " toB (Fig. 3a) we have a -H sign, and at A a Which particular arrangement is" best " any generator or accumulator.Think of a . sign. depends on the ratio of your circuit resistance2 -volt accumulator whose internal resistance To find the magnetic polarity of the iron in to the internal resistance of the entire battery.is perhaps considerably less than 0.05 ohm.the examples shown we may either consider Supposeitisaquestion of obtainingWhatsortof" load "wouldhavethisindividual turns or conductors, or apply the maximum power-let us say, generating theresistance ? screw -rule to the coil as a whole. greatest amount ofheatinaresistance element, " heat " being directly proportional Clearly it means shorting the terminals ! In Fig. 3b we have a current going from to the watts dissipated. No secondary cell is designed to supply any-right to left in the parts of the turns shown. A battery should be made up(series,thing approaching the maximum current andLooking at either " end " of this piece of a parallel, or series -parallel) whose total internalpower expressed by R=r.Neither are anyturn, we have a clockwise magnetic field, one real generators. whose lines of force enter the iron atits So when you do read in radio textbooks oftop end. conductor Lines of force enter S poles, hence the top Field Main Field " imaginary generators " whose loads must be matched toequal theinternalresistance,end is a S pole.Alternatively, looking at the I remember thattheyarelargelyfictitiousbottom end, lines of force emanate, giving us things-or, rather, generators which (if made)a N pole. would have an internal resistance of some thousands of ohms. Still, when amplifying, a radio valve is an (b) exact equivalent of a high -impedance a.c. Cur;;'';''A. generator. Direction (a) (C) About the " Corkscrew Rule " Fig. -4.-What will happen if the conductor Turning now to magnetic questions. The firstisthe familiar rule connecting AB having a concentric fieldas shown,is current -direction with magnetic polarity. placed in an independent " main field" due Showing to a pair of poles NS ? The " positive direction " of a magnetic Distortion field (the N to S direction) is related to the Of One Or Downward Force More Lines current direction in the same way as the Of Force resistance is as near as possible equal to themotion cf a right-handed screwisrelated (a) (b) resistance of your element. to the direction of turning the screwdriver- In the general case (series -parallel) we haveor a corkscrew, or a spanner. Fig. 5.-Magnetic forces which cause a motor N cells, grouped in m parallel rows, with Inward or downwards motion (a current armature to rotate. n cells in each row (Fig. 2c). Let the internalflowing away from the observer) requires that resistance of each cell be r ohms, and thethe screw shall be turned in a clockwise Actually, what we are doing is e.m.f. of each e volts. (right-hand)direction: alsothepositivesingle conductors. In Fig. 3d is shown Then : direction -of a magnetic field around a wire. exactly the same coil, where a few lines of e.m.f.=that of one row= ne volts Thus, looking at end B of the conductorforce are drawn to show more clearly that they Total internal resistance = nrjm ohms in Fig. 3a, the current is going downwardsenter at the top end and " emanate " from the External resistance (towards A), hence the field is clockwise asbottom end of the iron. Of course, thetotal field For greatest power : shown an imaginary isolated N pole wouldwill be due to all the concentrated " lines " nr/m = R, be repelled in a clockwise direction. around each conductor (or " turn "), com- or, n = mR/r Alternatively, looking at end A, the currentbining to act upon the magnetism inherent Also, m = N,'n, giving finally, is upwards (towards us), equivalent to turningin the molecules of the iron,i.e.,the per- -NR r, or n=1/NR/r, meability of the latter greatly augments the where n is the number that must be put in Scale total " flux." series in each row.If R isconsiderable But as far as finding the resultant magnetic compared with r, the answer will work out to polarityisconcerned,itissufficientto such a number in series as to permit only of consider individual conductors, as explained. Pointer one row, i.e., in effect, all the cells should be Permanent Fig. 3c and 3e similarly show the reversed connected in simple series (Fig. 2a). Magnet polarity when the current is reversed, or if In fact, calculations of " cell groupings " the " sense " of the winding is reversed, or are of more theoreticalinterest than any FixedSoft:I:dr,)[-Iron if the coil is turned upside down. real practical utility, but the principles of Core I Alternatively, we may apply the screw rule optimum loads are quite important in other to the entire coils. branches. In Fig. 3b, the current is circulating down- Thus, as in the battery case, radio and wards, from the top end.Here, our screw - audio -frequency loads have to be " matched " rule " reverses " its conventions. to the internal resistances of power valves- To turn a screw downwards requires clock- sometimes for maximum power, but usually wise motion. In Fig. 3a, this clockwise motion for maximum undistorted power, whichis was- the positive direction of the field.Here, equivalent generally to R=zr (a power slightly in Fig. 3b, however, the clockwise motion less than the maximum). denotes the direction the current is circulating ; Telephone and music lines, radio -frequency Control Radial Field Al -S 7b " downward motion "(ofaright-handed feeders, and so forth, have generally to be -Spring Give Uniform Tongue screw), then indicates that the top end of the matched to the inputs or outputs of amplifiers OnMoving -Coil magnet is a S pole-lines of force going for maximum " power transfer," i.e., R= r. inwards. Fig.. 6.-The simplest application (in theory !) In the same way if we regard the bottom of the motor principle.A coil, carrying theend :currentiscirculatinganti -clockwise Constant -voltage Sources current to be measured, will be acted upon(left-handed motion), equivalent to drawing So, altogether, the principle we have beenby forces Ft and F2 to give clockwise rotation.out a screw, hence lines of force emanate Because of theradial field -distribution,thefrom this end. discussing has highly important applications : sides of the coil will always be moving at right - primary cells are useful asad.c.illustra- It isall very simple once grasped.The tion. angles to the flux. change in conventions is a little confusing, But we have already given a warning about and itshould be noted when considering generalising too far-extending the principlea screw anti -clockwise, with upward motionindividual " turns " or " conductors " that to cases where it does not apply. of the screw itself. Hence we reach the samewe are applying the convention of Fig. 3a. For instance, an accumulator cell has anresult as looking at end B-a field whose+It is for the whole solenoid that the assump- extremely low internal resistance. For all loadsdirection is anti -clockwise (relative to end A)tions based on aright-handed screware within its capacity itis almost a' constant --clockwise at end B. switched over. August, 1949 NEWNES PRACTICAL MECHANICS 345 The " Motor Principle " L =active length of conductor in ems. (positive) direction. Therefore, the conductor I have dealt at some length with generator I = current in amperes. field will be in the same direction as the principles. The electric motor isequally For example :if a piece of wire to ems.main field on top-strengthening the resultant interesting as an application of fundamentallong, carrying too amperes, was placed in afield, but opposing it underneath the con- magnetic rules. ductor-causing a weakening of flux on this field of intensity to,000 lines per sq. cm., side. Consider asingle conductor carryinga it would be acted upon by a force (at right Lines of force will be bent or distorted out current oft ampere (Fig. 4a).It will beangles to the field) of approximately 2 lbs.of their normal straight-line paths, to take surrounded by concentric lines of force-aweight. " thepath of leastresistance " fromthe clockwise field, by the above rule ;if the Evidently a large number of such conduc-N pole to the S pole. Also, because lines of current is reversed, the positive direction oftors embedded on the periphery of a motorforce going in the same direction mutually the field will be reversed as in Fig. 4b. armaturecangiverisetoaverylargerepel, this distorted flux will tend to straighten Next, we have another strong field, positive" torque "(=Force x Radiusatwhichitout-again, to take the shortest possible path direction N to S (Fig. 4b). This is set upacts). from N-S. by an electromagnet such as the shunt field If the current in the conductor was re- Clearly this is equivalent to a force acting circuit of a motor. versed, or if, keeping this current -directionon the conductor-a downward force (Fig. What will happen if we place the current -the same, the main field polarity (positive5a).In Fig. 5b are shown two conductors of carryingconductor,Fig.4a,inthisin-direction of the main flux) was changed, thean armature, respectively carrying downward dependent field ? direction of F would be reversed. and upward current, e.g., the two " sides " Obviously,if,having reversed the main It will be found that a magnetic force actsflux, we alsoreversethecurrentintheof a " turn." downwards, tending to push the conductorconductor, the direction of the force will be The field will be altered in the manner out of the field,its magnitude (indynes)the same as we started with. shown, giving equal forces F, and F, tending being given by to turn the armature anti -clockwise. BLI,. Here we havethemagneticprinciples A fairly simple example of a single coil in F= governing reversal of rotation of a motor :a two -pole field is an ordinary moving -coil JO reverse either the armature current, or theinstrument, Fig. 6.With the current direc- Or, field current, but not both. BLI tions shown, a clockwise torque is developed. F= lbs. wt. To conclude this article :draw separate to x 453 X 981 Interaction of Fields sketches for these various cases, showing why (1 lb.xt t. = 453grams,andtgram Fig. 5a shows roughly what happens in therotation will be reversed by changing the " gravitates " with a force of 98t dynes.) case of a single conductor-that of Fig. 4a. direction of either field-the main flux, or the In this equation : The mainfieldisdirected N-S ;theconcentric field around the conductors. B----- magnetic density lines per sq. cm. field around the conductor has a clockwise (To be continued) Electrz zeci FenceConstruction Details of Installation and Working By FORBES M. MILNE, A.M.I.C.E. WHILE still somewhat of a novelty on6-12 volt coils will run this side of the Atlantic, the electrifiedquite well on 2 volts fence has achieved great popularityA.G. current, though in America.Thisisdue,principally,toif itis desired to use its many useful qualities as well as to its easeD.C. it is probable that of erection.While it is possible to buy thea slightly higher value fence ready-made, home construction is boshwill be needed.In the cheap and simple. latter case a selenium The supply for the fence may be takenrectifier is inserted either from an accumulator or, via a trans-between the transform- former, off the A.C. mains.Voltages supplieder and spark coil. by the accumulator run from 6 to 12 and The " live " wire of from mains transformers from 2 to 12 volts.the spark coil is then If possible, it is better to use a transformerjoined tothecopper asthissavesthetrouble ofre -chargingwire which istobe accumulators. electrified and a connection from the frame Using a Spark Coil of the spark coil lead to The fence depends for its action on ana well conducting earth. induction or " spark " coil.This increasesIf the fence has twin the voltageinthe lineconsiderably,thewires, say, a barbed wire amperage being, of course, very low.Theabove and the insula- high voltage imparts a sharp sting to anytor -carried copper wire 'animal coming incontact with the wire.below,the" earth " Whiletheeffectis,ofcourse,entirelywire may be connected, Compt-Lcsi. r a home -c-Jrs.iruc:edence,including plug for A.C. momentarily, after one experience animalsif desired,tothe mains, wa:ertight kw -value fuse,transformer and spark -coil in studiously avoid approaching the line.Tobarbed wire, the " live " waterproof box. owners of easily -raided orchards an electrifiedconnectiongoing,of fence may prove a boon. course, to the copper one. Finally,the transformer and sparkcoil Coming down to costs, a 6-12 volt induction must be protected from the effects of rain or coil can be bought for about I2S. 6d., a trans-Testing damp, and an easily -readnotice,such as former with three taps -2, 6, 12 volts-will After switching on the current the fence" CAUTION-ELECTRIFIED FENCE," cost about 25s., copper wire for the fence atshould be tested by holding a rake or othererected in a prominent position. 2s. per soft. coil, insulators 4d. each, whiletool with a wooden handle between the wires. 2 -volt accumulators will cost approximatelyWith one end of the. iron rake touching one 9s. each. wire hold the tool so that a small gap is left NEWNES' RADIO ENGINEER'S In the cable carrying the A.C. currentbetween it and the other wire.If the fence from the mains a low -value fuse should beis in working order a continuous spark should POCKET BOOK inserted to ensure that under no circumstancesbe seen across the gap.If this does not By F. J. CAMM can the dangerous position arise of mainsoccur the trouble is probably due to faulty 3/6, or by post 3/9 voltage passing through the fence.Near theinsulatitm of the " live " wire.No attempt proposed fence a switch should be insertedshould be made to obtain " fat " sparks by Obtainable from booksellers, or by in the mains wires, so that the current mayheavily increasing the voltage or amperage. post from George Newnes, Ltd.. be switched on andoff when required.The fence would then become dangerous and (Book D e p t.), Tower House, From this switch the cable goes to the trans-might involveits owner in serious conse- Southampton Street, Straiicl, W.C.2. former and hence to the spark coil.Mostquences. 346 NEWNES PRACTICAL MECHANICS August, 1949 Jet Reaction Power Models Spark plug for Various Types of Jet Power starting only - Air is Exhaust tail pipe EnginesforModelAircraft sucked in and Boats By C.E. BOWDEN, A.I.Mech.E. The length of this pipe controlsthe rate of pulsations.A long pipe makes FULL-SIZED military aircraft are Petrol for easier starting rapidlybecomingjet -poweredand as a gen- Crocodile eral rule, there is already an airliner flying with clip jet engines. This development is not surpris- ing when it is considered how fundamentally The air for initial more simple a jet engine is than the compli- starting is blown Both are in by an air pump cated reciprocating piston engine. which is removed internalcombustionengines,butthejet as soon as the engine eliminates many moving parts besides motor starts getting away from that limiting factor of the 6 volt trembler 6volt accumulator propeller at speeds of approximately cot/ (Ford, providing starting 450 m.p.h. and over, when propeller drag current becomes a serious problem.Furthermore, a jet engine has no torque reaction trying to Fig. 2.-The basic principle of the model pulse -flap valve jet motor. turn the aircraft around the propeller's axis. This latter point is most important from theright lines instead oftrying to bancult to encourage a suitable low -powered jet aero modeller's angle, for atleast 8o perfree -flightjets,forthefactmustbeengine, apart from the rocket type, by sensible cent.crashesareduetotheupsettingfaced upto,that whateverobstaclesarcrules. forces of propeller torque.Itis simple toplaced in its way, the jet is the coming power There are one or two venturesatthe design a model glider to have great stability, moment which will doubtless provide smaller hut as soon as an engine with its propeller and less powerful jet motors in the future. isadded,stability problems occur dueto Our present engines have developed from the torque reaction. very powerful American jet motors, and all Apart from this advantage of jet propul- atpresent offerover34lbs.staticthrust sion for models, the fact that full-sized craft which builds up to greater thrust due to ram will mostly be flying by jet propulsion in the effect as the model flies or travels faster. Such next few years, with perhaps the exception of a thrust is vastly more than we require in thesmallest personalplane,isbound toFig.r.-The basic principle of jet forwardthiscountry, exceptforracing speedsin cause the modeller to follow suit. reaction. control -lineflight, when arecordis being sought. Unfortunately thereareatthe moment (Left) An explosion in a sphere creates an equal force on This ultimate speed craze has evi- certain limitations, for the model jet engine allsidesinternally. dently appealed to the Americans who have (Right) Ifa vent atone side is opened there is a lowput the world's speed record for control -line is in its infancy and has lagged behind itspressure here, and the force will remain momentarily full-sized brother, not so much in efficiency,high at the opposite side, thus giving the sphere a push flying model aircraft up to over 170 m.p.h. which is high, but in a useful size and power in the direction of the large arrow.This is the force of by a jet engine. output to suit this country's peculiar over- reaction employed by jet engines. When we consider that the most popular crowded conditions.There is not the safeunit and cannot be supressed in the future.sized piston reciprocating (propeller) engine space to fly high-powered model free -flightThe old " red flag" failed to stop the motor-in this country to -day is the diesel, having a jet aircraft in safety, and most of the model car and motor -cycle.It should not be diffi-thrust of approximately 15 to zoozs., it will be clear what I mean.Such a thrust suits Fig. 3.-The Dynajetour model purposes in general.Naturally flap -valveengineis greater. thrusts are required for special pur- here shown with theposessuchasfree -flightand control -line nose removed. Behindmodels of the large type, and also for radio - the nose can be seencontrol models, but it has been found that the flap or "flutter"the average boy or young man is best suited valve which has tenby the lower -powered engines, and this in my petal -like arms ofopinionisthe power that thejetengine spring steel which openshould be designedtoproduce atalow and shut with rearwardweight. movement controlled byPrinciple of Jet Reaction iddinced "button." There are many people who still do not understand the general principleofjetreaction. They think that the eflux or exhaust gasei roaring out from the tail push on the air and so propel the craft. Ajetreactionmotor jetunits of the internal combustion operates on theprinciple type as opposed to rocket, are of a of Newton's third Law of very powerful and noisy set up. The Motion, which states that power is so great that even control - to every force there is an line flying can be dangerous to spec- equal and oppositeforce. tators ifthe operators are not care- A flow of gas through a ful about the strength of lines and so nozzle, orjet,requiresa on. Naturally, most local residents force to give its high velo- object to the noise which, although city, and there is' thus an stimulating to the enthusiast, is annoy- equalforce onthecon- ing to those without any interest in tainer, driving it forward in the subject. the opposite direction to the This is, however, a matter of de- Fig. 4.-The writer's. American Dynajet is seems mounted on a test block jet outlet.In other words velopment, and in my opinion it would with fuel tank.The British juggernaut is resting on the ground below. we may say that the force be better if the F.A.I. and S.M.A.E. The starting air nozzle is beside the fuel pipe. in front of the air intake of the expanding gasesis were to control development along the which is finned to .keep the flutter valve cool.- - actually taken by the August, 1949 NEWNES PRACTICAL MECHANICS 347 engine's body and thence transmitted to theof which affects ease of starting and powerflutter -valve whichisopened by the air airframe or the boat's hull.Fig. t shows theoutput as well as the exhaust note.Air isblast where itmeets the stream of sparks general principle by the well known spheresucked into the nose where there is a venturifrom the coil. An " explosion " results which or balloon idea. (i.e., a restricted tube) which creates suctionshuts the flutter -valve and gives the forward - In this sketch it will be noticed that if anover a fuel jet.The suction created raisesreaction push to the .engine's internal body, expansion or " explosion " of gas takes placefuel from a tank situated just below the jet.atthe same time the expanded gases rush in a sphere, an equal pressure takes placeThe fuel is ordinary car petrol, and there isout of the open rear tube thus causing an internally on all sides.If one side is openedno lubricating oil used, for there are nt otherextractor effect or a partial vacuum in the suddenly the gases will rush out from thatmovingpartsthanaspringysteelflap - combustion chamber.This opens the flutter - side,andthepressurewilldrop,butis valve.Petrol is easily vaporised and burnsvalve petals and draws in a further charge momentarily maintained at the opposite side. sufficientlyfasttosuit the high pulsationwhich is fired this time by heat created from rate. The flap -valve,the first " explosion."The air pump and Air compressor Combustion chamber orflutter -valve as the electrical gear are removed and the motor theAmericanscallruns until the fuel ends or becomes too weak it,is located in theor too rich through possible maladjustment. Air nose behind the fuel It is hard to think up a more simple engine jet. giving greater efficiency.Certainly there is Thepetrol / airfar less complication than the reciprocating intake mixture, in the formpetrol motor with its piston, connecting rod, of an explosive gas,crankShaft and bearings to be carefully fitted is sucked or blownand lubricated.But, on the other hand, the Turbine wheel driven Bearing by a pumpforpulse -jet engine has to be carefully designed by exhaust gases starting into theto get the right harmonic balance between The turbine is attached to the air combustion chamber compressor by a shaft and therefore length and thickness of pipe, flutter -valve sucks inair. throughthisvalve.thickness and springiness, and limiting stop, There is a spark plugetc. Any one of these featuresif out of Fig. 7.-The principle of the " turbo jet " orgas turbine engine. fitted in the wall ofphase may stop the engine working. The t h e combustiononly moving part is the flutter -valve springing Therefore, the spheregetsakickinthechamber facingtheintakeorifice.Thisback and forth. opposite side from the open vent. isforstartingonly.Behindthe flutter - The length of thetail -pipe control, the Every boy will have noticed that when avalvethereis aradiused" button "tofrequency of the pulsations, and therefore child's toy balloon is blown up and the ventlimit the movement of the valve's petal -likethe time of ignition,is controlled by this suddenly released,theballoonwillshootarms.The combustion chamber is extendedresonance frequency,subjecttosubsidiary violently off in the opposite direction to theinto a long exhaust pipe which is restrictedfactors such as fuel strength and the thick- released vent.This is the principle of jet indiameter.Thislongpipegivesanness and springiness ofthe thin tempered reaction, for the front of ajet engineis extractor effect like the long pipe of a racingsteelflutter -valve. Ifthetailpipe is virtually closed in varying ways and the rearmotor -cycle's exhaust. Fig. 3 shows the noseshortened the frequency of the explosions is open. of an American Dynajet engine taken off and increases.A long pipe usually means easier Last year I gave the first B.B.C. Televisionthe flutter -valve's ten littlepetals in view. startingandalittleless power. The broadcast on model jet engines, in which I A trembler coil is generally used to createAmerican Dynajet (see Fig 4) has a pulsation showed . thereactionprinciplebyatoy theinitialstartingsparkafter whichthe frequency of 280/300 per second, which balloon which duly leapt across the camera'sengine runs by its own heat. An old T Fordaccounts for the noise! front as the vent was released.I then flewtrembler coil using six volts makes a useful a small jet-engined model across the studiounit as there is then no need for a make -and -Pulse -jet Engines Available much to the interest and amusement of thebreak and contact breaker, for the Ford coil There are two pulse -jet motors onthe operators.Fortunately it flew to order, land-gives a constant stream of sparks when theAmerican market which have lead the way. ing among the rafters of the studio! current is switched on.A car hand -pumpBoth are the same in general principle but is used to introduce the initial blast of air. vary conspicuously inthe form of flutter - A Popular Type of Model jet Engine To start, the air pump The most usual engine for full-size workis connected to the starting is the gas turbine, because this type can betube on the engine nose, run up on the ground and throttled backand air is pumped by hand within reasonable limits in the air. insteadyblastswhich The Athodyd, or the Ram Jet, is the mostdraws up the fuel from the simple jet engine and, in fact, the most siMplefuel jet and, mixing with prime mover in the world; itis suitable forthe petrol, forms an explo- supersonicspeeds,but hastheverybigsive mixture. This mix- limiting factor that in order to start,it hasture is forced through the to be moved through theairatbetween zoo to 500 m.p.h.This is generally doneFig. 6.-A Dynajet-powered Naturally, such amodel is seen being started up by the means of rockets. by hand -pump tointroduce jet is not suitable for normal aircraft. Thethe initial blast of air. Note Athodyd is just a tube with a diffuser at thethestarting Ford trembler forward end and a ring of fuel jets behindcoil and its six -volt accumu- the diffuser.There is no air compressor and turbine to drive the compressor as in the gaslator is carried in a box by turbine (see Fig. 7.) these voting men. A further type of jet motor is on the lines of the German "Buzz Bomb" in the last war. This is the Pulse Resonance Flap -Valve jet engine,andistheone which hasbeen developed by the Americans for model work. The British have followed their lead, which Fig.5.-TheBritish has resulted in the very powerful and noisy Decojet is an exception- engine I mentioned at the beginning of this ally easy starter, having article. a long tail pipe which This type of engine is a highly scientific usually assists this fea- achievement although it is so simple in con- ture.These jet motors struction.It is a most efficient power pro- have a greater power ducer giving over311bs.staticthrust on than the " hot " so c.c. the ground for an approximate weight of xlb. typeof model petrol As the speed rises through the air there is a engine seen below the jet considerable risein thrust.There are no engine as a comparison complications of compressor or turbine as in forsize. The fuel the turbo -jet, and yet we have this most consumption is approx- important thrust from rest which makes it imately' three times useful for model aircraft.How is it done ? greater. The general principle is shown in Fig. 2. The engine is essentially a tube, the length 348 NEWNES PRACTICAL MECHANICS August, 1949 valve used.The Dynajetisperhapstheadequate cooling.These engines all run very The model seen in Fig. 6 is shown being best known to modellers in Phis country. I hot and rely upon forward motion to keepstarted up by two young men, and atthe have one of these motors which I use on myreasonably cool.They therefore should nottime when Itook the photograph they had Models.Fig. 4 shows my Dynajet mountedbe run up for more than a few seconds ondone over 3o hours flying using the same on atest block with a British Juggernautthe ground.In the failing light of evening flutter -valve.Even then there was no sign lying below it.The Juggernaut is approx-they emit a lurid red glow with licking shortof ragged edges through excessive heat.The imately the same length and hasa petalflames from the exhaust as they fly aroundAmericans use some excellent steel for the flutter -valve reminiscent of the Dynajet. on a control -line model.This glow addedpurpose. A recent comer on the British market isto by the noise makes the whole performance The following dimensions of leading jets the Decojet, which Ihave found to be anmost intriguing and adds a spice of excite-may interest readers : - exceptionally easy starter.One or two pumpsment to the high speed at which the models Ame rican-Dynaj et: Length 21 I ins., and the engine is booming away.This motor fly. Fig.5givesa view of the Decojetmax. diam. 2.1ins.,tail pipe diam. a ins. ; has alonger and thinnertailpipe whichwhich I use, with a " hot " to c.c. petrolMinij.t: Length 281 ins., max. diam. tins., probably accounts forits outstanding easymotor below, to show a comparison betweentail pipe diam starting.There isa shrouding discfittedsize,etc.The toc.c. motor isgenerally behind the flutter -valve on the Decojet whichconsidered to be the racing class for control - British-Juggernaut: Length 214 -ins., protects the valve from excessive heat whenline work in the reciprocating engine line.max. diam. 21ins.,tailpipe diam. Dins ; the engine is fitted to a slow model or runSpeeds have been reached around the 140Decojet: Length 3oiins., max. diam. 28 ins., up on the ground.This can be removed ifm.p.h. mark against the 170 mark of the jettail pipe diam. tins. the engine isfitted to a fast model, givingin America. (To be concluded)

has been completed and limited train opera- tionis possible. Lecture meetings are held on thefirst Club Reports Wednesdayin each month, in the Lecture Room,CentralLibrary,Portsmouth,at Preston and District Society of ModelParticulars shouldreachthesecretaryby 7.t5 p.m. Engineers t7th September. Further information is obtainable from the The society is a member of the S.M.E.E. hon.sec., F.J.ALLISON, 2t, Carmarthen SINCE thebeginningoftheyearthe Avenue. Cosham, Portsmouth. Society has enjoyed the use of a roomaffiliation, and the support of the affiliation kindly rented. to us by the W.E.A. Thishas also been promised.Hon sec., W. T. has been quite a change after the uncertaintyHOWARD, Technical College, Shrewsbury. of the previous year.For the benefit of any Books Received model engineers in the Preston district whoPortsmouth Model Engineering SocietyLathe and Shaping Machine Tools. By may be intending members, the society now THIS Society now has in hand the publi- " Duplex." Published by Percival meets every alternate Friday at 23, Chapel cation of a periodical newssheet maga- Marshall and Co.,Ltd. 72pages. Walks, Preston, at 7.3o p.m. zine which it is hoped will contain articles of Price 3s. net. So far this year, visits have been made tointerest for all members. A monthly bulletinIN order to produce accurate and a cotton mill, the Ribble power stations,informing members of the business trans- finished work in the lathe or shaping andPrestonlocomotiverunningsheds.actedatcouncilmeetingsisalreadyinmachineIwelt- the tools must be of correct form Shortly, a Sunday visit will be made to thecirculation. for the operations undertaken, and they must British Railways locomotive works at Hor- At the moment, a very ambitious pro-also be properly sharpened.The object of wich. Further visitsto places of interestgramme is being executed.The gauge " 0 "this book is to deal primarily with the practical are being arranged to take place afterthebailwayusedinthe1947exhibitionhas side of this important subject, and interested society visit to the M.E. Exhibition on she een dismantled, and a new track is beingreaders, desirous of improving the quality 26 -27th August.This tripwill be madeconstructed by the model railway section.of their work, will 'find in this handy little by motor coach, specially booked for theNew stations,signals, permanent way andbook much that is both helpful and instructive. occasion. scenic effects are gradually being introduced,The book is illustrated with numerous line A start has been made on a5in. gaugeand itis hoped that the plans will be fully drawings. locomotivebyvariousmembersoftherealised before the end of the year, in time Newnes Engineer's Reference Book. society, with the idea of a running track offor the 1950 exhibition.The layout will3rdEdition. Greatlyenlargedand fully our own. Atthepresent momentthebe portable, being divisible into eight inter-revised, 45/-, or 46/- by post from George society does not possessa workshop, andlocking sections. Much of the trackworkNewnes Ltd., Tower House, Strand, W.C.2. members are machining the loco intheir cwn workshops. Future meetings:5th and 19th August ; 2nd and 16th September.Hon sec., M. A. COLLARD, 46, Brackenbury Street, Preston. Shrewsbury and District Society of Model and Experimental Engineers THE above society was formed in May, 1946, and has a membership of over 40. Meetingsareon Monday evenings, 7-9 p.m., at the Technical College.Our president is A. Moore, Esq., Principal of the 1144131teWt*****4,} College. We have the use of the very 041/11." extensiveworkshops,including7centre 11111411.4411 ataidttatsttn lathes, shaper, universal and vertical milling machines, 1in. capstan lathe, radial and pillar drilling machines, engraving machine, preci- sioncirculargrindingmachine,fly -press, etc. In addition, both oxy-acetylene and electric welding equipmentisavailableto members.The total annual subscription is t9/6 for members over 21, reducing to 3/6 at 15. Exhibitions were held in 1946 and 1947, supported by theOswestry and Wrekin Societies.Our exhibition this year will be in the Walker Hall of the College on Friday, 28th October, 7-9 p.m., and Saturday, 29th October, 2.3o-9 p.m. Approximately tooft. of 3' in. and 5in. gauge track willbe inoperation. The exhibitionis Final assembly stages of the superstructure of the lin. to the foot scale model of the R.M.S. non-competitive,andentriesareinvited " Queen Elizabeth," made by Bassett-L=1m, Ltd., of Northampton.This fine example of fromall model engineersinthelocality. British craftsmanship is reputed to be the world's largest ship model. August, 1949 NEWNES PRACTICAL MECHANICS 349 The Elements of 7\4'I and Mechanisms 22 Water Wheels (continued)-Applied Mechanics-Geneva Mechanisms

Alteration of Wheel Acceleration ByF.J. CAMM projecting from the slotted face of the wheel TENTATIVE methods of decreasing the enables a much smaller locking plate to be acceleration of the wheel in the Geneva (ALL RIGHTS RESERVED) employedandeffects efficientlocking. mechanism considered must necessarily Accurate location of the lugs on each side aim at the reduction of the value C-r, since thegreat care is needed in the fitting of rollersat the extreme outer ends of the slots is easily maximum velocity ratio is given by r (C- r),and groove and in the location of the rollers.effected and the load on a lug when resisting a and the crank radius r is constant.In other A second method of locking the wheel isparticular torque is about 3o per cent. smaller words, the locus of the roller centre must TABLE I.(REFERRED TO LAST MONTH) than the corresponding load on a roller in intersect the common centre -line of driving DESIGN FACTORS FOR STANDARD DRIVES. the arrangement of Fig. 9, since the locking and driven shafts at a point more remote from is more efficient. Thisisfulfilled by a the wheel centre. Maximum Uniform Wheel Velocity shallowcurve betweentherollercentre Configuration Sfsft.7:7nrecev,V;p1 positions at slot engagement and disengage- atrollerentry When the movement of the driven wheel ment, which is tangential to the centre -lines c ;57 of intermittent gearing is required to be at of the two slots at these positions. constant speed bevel or spur gearing of the A method of realising the above require- -...,, form shown in Fig. 7 can be employed. -2r Such gearing is kinematically identical to ments is illustrated in Fig. io.The roller is 30 60 243- the Geneva mechanism, since the rolling of mounted on a pin fixed to one corner of a 73- the roller along the slpt corresponds to the triangular frame which is pivoted at one other :11541....6.4630 corner to a link pivoted to the fixed frame of i rolling action of mating spur teeth. The the machine. The triangular frame is actuated i-aw ' method of lockingisalsothe same.It by the pin of the driving crank and the represents a convenient method of effecting / intermittentrotarymotionatveryshort resultant locus of the roller centre, which is ZdArliTai' I-2- r 1-271-7 indicated by the continuous chain -dotted line, intervals which may be regular as at (a) or fulfills the requirements outlined above. °/-4/4r:2.4/39 irregular as shown at (b).Fig. 8 shows the The method of incorporating a locking / Geneva mechanism in a simple form. plate shaped as a circular sector is illustrated 'i The Inverse Geneva Mechanism in Fig. r 5.The locking plate is keyed to an The above title refers to a form of inter- auxiliary shaft which is driven from the main mittent gearing based on the Geneva principle, driving shaft by means of three spur wheels Icpithk,'"- "ilk-/.70/r.1.426 in which the directions of rotation of driven 5, 2 and 3.The numbers of teeth in the spur and driving shafts are the same.A typical wheels must be arranged to effect correct example of a mechanism employing a four - relative motions of locking plate and driven slot wheel is illustrated in Fig. 52, which gives wheel in opposite directions. the configurations of the mechanism.The `re* corners formed by the intersections of the '"kre.dri. 2r .1000 slots must be cut away at least to a radius -4* 22io

- r1#1--t%-iii4 26/3r.0.6203 71S

Ire° 11 .A' Fig. 6 . - '1...r'n'tlim- .05208 Alternative 2923r methodlocking of ?itk! stationary 18° wheel. 44- (b) MP.%- 3236r.04472 Fig. 7.-Types of intermittent gearing. equal to the distance of the driving shaft axis Alternative Methods of Locking Wheel from the crank pin or roller.For ease of Two alternative methods of locking theillustrated in Fig. 6.The above objectionsmanufacture the surplus material between the wheel during itsstationary period of theare overcome by this design, which is muchslots is cut away as indicated by the dotted intermittent motion are illustrated in Figs. 6cheaper to manufacture ;the use of lugsstraight line. and 9. 0 The action of the inverse mechanism is The locking plate D (see Fig. 9) is in the kinematically identical to that of the ordinary form of a sector with a circular arcuate groove Geneva mechanism ;the crank pin or roller which is engaged during the crank idling engages successive slotsin the wheel and period by rollers mounted on the outer face drives it through a fraction of a revolution of the wheel.This arrangement has great according to the number of slots employed. disadvantages ;itisrather bulky and the No drive is transmitted while the roller is wheel must be placed on the end of the traversing the circular arc connecting succes- drivingshaft,otherwise the lockingplate sive slots. would foul the shaft extension.Also, the The rollerenters and leaveseachslot lockingeffectof therollercontactinga tangentially, and hencethe idling angle 4, circular -arc surface described -about a centre of the crank rotation during which period no considerablyoff -set from therollerpitch driveistransmittedis(580 -9o) deg. A centreis much reduced and consequently Fig. 8.-Geneva mechanism in a simple form. general formula for the crank idling angle is 350 NEWNES PRACTICAL MECHANICS August, 1949 cos A sin B V R max - ..(10) Sector ' '-x+cosA I+ sin Note that the angle A is one-half the idling angle stof the crank rotation. For example, for a five -slot wheel the angle between two successive slotsis 36o--5=72 deg., and the maximum velocityratio given by V.R.(5)-sin 36' (max.) 4- sin 36' .5878-0.3701 1.5875 Maximum velocityratiovalues for several wheel types are given in Table II. To determine the velocity ratio at Lockingany intermediate position, consider Rollersageneralconfigurationofthe mechanism,such as is shown - diagrammatically in Fig. 14b. The velocityratioisthe ratio of theFig. 1L-Method o)incorporatingalockingplate in distances of the line of action of the a modified Geneva mechanism. roller thrust from the crank and

(t3) Geneva wheel centres, and therefore can be expressed Ek=EB tan 0=r sin a tan 0 Wheel as It remains to determine the value of tan 0 V.R.-oA in terms of C, r and angle a Fig. 9.-Exploded diagram of a compact form OB where o is the crank centre and 0 is the centre sin 0=rsin a= r sin a of Geneva mechanism. OB V r2H C2 -1-2r C cos Oscillating ( n-2 and since cos 0=1/I --sine ct=I80 --n360 =18o degrees (8) /ever -n ) r sin a tan 0 where n = number of wheel slots. Roller r cos a Forexample,theidlingangleforan eight -slot wheel is r2 sin2 a r2(t -cos'. a) 8- 2 C+r cos a C+ r cosa 4,, 1.135 deg. rcos a +Ek (-8 As with the ordinary Geneva mechanism, a Drivin C+r cos a+Ek circular -segmentalplateintegralwiththe crap r(C cos a +r) driving crank can be used to rigidly lccate the zr C cos a+r2 (14) driven wheel during the crank idling period. The convex edge surface of the locking plate As a check consider the mid -position of the mates with the wheel face, located midway configuration, that is, when angle a =O. The between each pair of slots, and effects locking velocity ratio calculated from equation (14) of the wheel.It should be noted that the Path of roller gives the maximum value of equation (9). arcuate mating surfaces must be described J The similarity of equations (4) and (14) for about a centre at the crankshaft axis, and mustFig.o.-Method of reducing acceleration ofthe ordinary and inverse Geneva mechanism subtend an angle4, (see equation 8) at the wheel. should be noted.The wheel velocity for the same axis.The method of locking inverse inverse form is obtained from Geneva mechanism is shown in Fig. 13. of the wheel.Since the lines oA and OB are rC cos a +1-2 The direction of the roller thrust, which isparallel, then W w0+2rC cos a+r2 (is) perpendicular to the centre -line of the slot, is ok ok indicated on a diagram of the configuration V.R.= - - (It)and the acceleration equationobtained by illustrated in Fig. 14a. The velocity ratio, as Ok C(-ok differentiation is with the ordinary form of Geneva mechanism ok = oB cos a4 Ek (12) [Cr sin a(c2+r2) = r cos a +Ek Acc=w2 ....(i6) already considered, is the ratio of the distances C2+2r C CO3 a r2 of the line of action from the crank and wheel Since r = oB = crank radius centres. a = angle of crank from mid -position.where W =angular velocity of wheel, w= uniform angular velocity of crank. The maximum velocity ratio, which occurs Also0-angle of wheel from mid -position at mid -position when crank and slotare (To be continued) collinear (see Fig. 12a) is given by : = angle BOk or Aok or plate EBk Angular velocity of wheel Driving V.R. max. -Angular velocity of crank crank = (9) I C + r where r = crank radius C = centre distance of shaft axes. The maximum velocity ratio can be found by the method used in the determination o the maximum velocity ratio for the ordinary Geneva mechanisms.Since (tansM A) C = r cos A+ where Br A=angle of crank from common centre- line, and B=angle of wheel slot from common centre- line, both atthe instant of roller engagement or disengagement. Also B=3 angle between two successive slots, and A + B = go deg. Therefore (a) Wheel midposition (1) Beginning Of stationary period Ccos A_ sinBand I2.-Inverse Geneva mechanism. August, 1949 NEWNES PRACTICAL MECHANICS 351 THE WORLD OF MODELS The "Barnes Model Shipyard": An Electrically Controlled "0" Gauge Railway By " MOTILUS"

alongside the Leeds and Liverpool Canal at Maghull &ring PASSERS-BYthe last two years have occasionally seen electrically -controlled model ships skimmingthrough thewater,zealously Watchedby twoorthreeschoolboys,in company with a man who was criticising or appraising the performance as keenly as the boys themselves. Had anyone stopp:,1to enquire, they would have discoveredthat they were witnessing trials of one or more oftheproductsofthe" Barnes Model Shipyard." This unusual venture was started some- time in 1947 by Mr. W. E.Barnes, an engineer'sfitter, who was thenlivingin Maghull.His idea was that his 12 -year -old son, William Martin, together with two or Fig. 1.-The " Barnes Model Shipyard " :the team goes " full speed ahead:"Master three schoolfriends, should make model. ship- William M. Barnes is on the far right. buildingtheirhobby,underhisown guidance. Part ofthe Barnes' home was hull.The ultimate thickness of the hull isSuperstructure and Fittings turned into a miniature shipyard, equippedtin., calipers set t6 this measurement being Superstructure is built up from 16 s.w.g. with the usual workshop tools.Before longused continuously during the hollowing -outaluminium sheet, windows being drilled and it was flourishing, the boys and Mr. Barnes process:chiselandglasspaperensurea thenfiledsquare and backedwith green doing thewhole of the work themselves,smooth finish. celluloid.The decks are of plywood, fixed to the superstructure with panel pins, as no glue isused.Tinplate (24 s.w.g.)is used for the funnels, which have bands of wire soldered on.Lifeboats the boys carve from solid wood.In the interests of economy, Mr. Barnes collects as much " scrap " tinplate, wood and other useful odds and ends as he can.The power units, propellers and shaftsand smallfittings,such asvents, navigation lights, anchors, chains, ,sidelights, etc., have to be purchased, as the shipyard has no facilities for making these items. Mr. Barnes insists on the best possible finishforthemodels, andseesthathis workersuse plentyofgla'sspaper, From three to five even coats of paint are applied to the models with camel hair brushes, the plywood ' decks beinglinedand then , varnished. One of the difficulties Mr. Barnes has 'had to overcomeisfinding an easy method- tohelpthe boys determinescale proportions when dealing with the super -

Fig. 2 . -S " a free-lance design p.m' the model shipyard.This oil -tanker is 2ft. 6in. long and electriially-driven. from designing and. building the vessels to the launching and water trials on the canal. Before the boys start building any model, Mr. Barnes schools them well innautical terms, ensuring that they know the difference between bow and stern, what is meant by displacement and sheer of hull, the names for the numerous deck fittings they will have to make and where they are placed on a ship.Next he suggests that they build a shipto the boys' own design, bearing in mind thatitis to be a working model, yet with as much true detail as possible. The model hulls they _usually make from white pine, using templates of card, cut in half -patterns, so that they are reversed for the second half of the hull.Card templates Fig. 3.-A general view of a portion of Mr. G. Stainton's gauge" 0" model railway, showing are again used for shaping the sides of the one of the stations. 352 NEWNES PRACTICAL MECHANICS August, 1949 structure and fittings. His ingeniousning of the last war, solution to this problem is to cut up -match-he lost all his original sticksto represent a scale -size man:withoutfit through enemy the aid of tweezers, the model -makers canaction. Likemany insert the matchstick alongsidetheir workother modelmakers, ,for comparison on any part of the ship. however, he was un- daunted, and as soon Model Liner " Ocean Queen " as circumstances Mr. Barnes had made the construction ofallowed he set to work theseship models sosmooth -running andtobuildup anew efficientthatitonly took the team three gauge 0 railway. weeks of evening and week -end workto At the timeIlast completethefree-lance liner, " Oceanheard, the lay -out was Queen," shown in the illustration (Fig.f). Soft. long and about During the two years that the shipyard was6f t. wide, a portion at operating at Maghull they built models ofone end being extended tramp steamers, paddle steamers, cargo boats,tosoft.inwidthto ocean liners, rug boats, oil tankers, a clippertake the main railway after the styleof the well-known " Cuttystation,engine sheds, Sark," and a model warship designed byturntable,etc. The 12 -year -old William Barnes. two main tracks were In May thisyeartheBarnesfamily 2f t. 6in.radius,al- moved to Wilmslow, Manchester, where theythough later it is lookforward torenewingmodelmaking hopedtoextendthe activities and increasing the range oftheirlay -out to provide for work. When I last heard from Mr. Barnestracksof5ft.radiusFig. 6.-A skilled craftsman puts final details on four models of the new he was busy drawing plans for a model of curves. Beforethis Peron." Thescaleofthese the magnificent Dutch liner, " Nieuw Amster- Argentine -ownedvessel, Presidente can be done, however, models is 32/i. to sin. - dam,"sothatIanticipate with pleasureMr. Stainton will have furthernewsfromthe" Barnes Modelto make some structural alterations in the tion,hehasbuilt up distanthillsand Shipyard." portion of his home where the railwayis mountains with the aid of mortar and cement; housed! other scenery is built round the outside, and An " 0 " Gauge Model Railway All the track is permanent way, installedin the centre of the layout, including a small Some time ago I was pleased to receive with wooden sleepers on a base-model village with a school, house, shops, a board and slide -on chairs.Thechurch and an hotel. sleepers (vin. by fin) were cut After much perseverance on the part of from old Venetianblinds,as himself anda keen model -making friend, Mr. Stainton's aim is, as far asMr. Stainton has made this layout reliable possible, to make all the lay -outforelectricaloperation.The photographs himself.The two main tracksI have been able to obtain do not, I fear, are divided into four sections,really do justicetothisexcellent railw iy each controlled by section layout, of whichall but the rolling stock switches in circuit, with trans-has been built by the owner himself.The former andrheostats. Thepictures do, however, give readers some idea sidingsarealsocontrolled byofthis comprehensive scenic railway that switches in circuit, with a trans-is the result of so much time and interest former.The control board hasdevoted to patient craftsmanship. three control areas: No. mainModel " Royal Scot " Loco in Hollywood track, No. 2 main track, No. 3 It is interesting to note that many model sidings. The three roadsenthusiastsoutsidethiscountryare keen through the main station can beon having models of the popular types of cut out individually withlocomotive that run over British Railways. switches and the same appliesOne of the most popular is the Royal Scot tothesidings. Thesignals,of the London and Midland Region.This made by Mr. Stainton, are twois often the choice of Swiss model -makers, light type and are operated fromand there are also several such models in the control board. the U.S.A. Mr. Stainton is keen to have One of the well-known Royal Scot models good scenic effects for his rail-is operated in the U.S.A. on a'7 tin. gauge way, so has covered the brickrailway owned by Mr.', C. N. Rinek, of wallsofthe room with wallEaston, Pennsylvania, who is most enthiasi boards on which he has paintedastic about his British -made model locomo- a realistic background.In addi- tive. Anotheristo be found in the far West,owned byMr. DavidRose,ofHolly- wood, California.In Mr. Rose's sub -tropical garden he has a fine 7,4in. gauge layout, on which he runs Fig 4.-Mr. Stainton's " o" gauge railway a Roval,Scot model lo .:o- the mouth of the tunnel that passes under the motive made specially to his orderbyBassett- model village. Lowke, Ltd., of North- a letter from Mr. G. Stainton, of Liverpool, ampton. Most of Mr. who has been developing a gauge 0, elec- Rose's passenger -carrying trically -controlled, model railway at his home wagons and other vehicles, in the Liverpool suburbs. The whole scheme however, are of American Mr. Stainton has in mind isnot likely to production. be complete for another 18 months or two In the illustration, Fig. years:even then, I do not suppose itwill 5, Mr. Rose is seen with reallybe" finished,"asInever knew a hisBritish -made loco- model railWay owner who was not always motive on the track. I am planning further additions or improvements indebtedfor thisphoto-, to his lay -out. graph to Mr. C. Derry, Mr. Stainton started his model railway who; during a recent visit hobby some 3o years ago at the age of six to U.S.A., called on Mr. and his enthusiasm has never waned with Fig. 5.-Mr. David Rose, of Hollywood, standing by his British -madeRose and took the oppor- passing years.Unfortunately, at the begin- 711n. gauge " Royal Scot " loco;notive. tunityofphotographing August, 1949 NEWNES PRACTICAL MECHANICS 353 thislayoutandthevariouslocomotives. this first ship isthe Presidente Peron, andWater -line Models she has accommodation for74first-class The illustration, Fig. 6, shows four water- Scale Models of the "Presidente Peron"passengers and large, -insulated -cargo capacity. line models of this new ship being made A modern liner of unusual external designHer overall length is629ft., breadth 71ft.by a professional craftsman, to ascale of has been built recently at the narrow ship- Shehastwinscrews,eachdriven-by yard of Vickers -Armstrong, Ltd.This isParsonsdoublereductiongearedsteam32ft.totin.By the time this magazine the first of three new Argentine -owned shipsturbines,developingabout14,50os.h.p., reachesreadersitisexpectedthatthe for a fast passenger -cargo service betweenwith steam supplied by two oil -fired water -Presidente Pcron will have made her maiden London and Buenos Aires.The name t:ftube boilers. voyage.

to the increased paper allocation more copies of Tool News are promised, commencing Trade Notes with the next issue, dated August. World's Largest Ship Model A Side -filling Battery It is claimed for the synchro switch that VERY attractive and wellillustrated ON manycommercialandpassengerit has proved highly successful in operation,Abrochure giving a comprehensive vehicles there is often little head -roomthat it clicks easily into each position, beingaccount of the construction of a large model above the battery, and access from above forratchet -operated for exact, positive and easyof the R.M.S. Queen Elizabeth, has been Filling or topping up is difficult, or imposs- action. issued by Bassett-Lowke, Ltd., of Northamp- ible.Operators must have yearned for an ItisfinishedinHerculeshigh -lustre ton, the makers of the model.Intended for Easier battery -filling arrangement under thesechromium plating of the same high standardexhibition in the offices of the Cunard White conditions. as all other Hercules chromium -plated parts.Star Co. in New York, the model is built Specialfeatures arethatthesyn- chro switch is suitable for any make ofcycleandfor any3 -speedvari- able gear, and that itfits any handlebar,andcanbe secured to the handlebarinany position to suit the rider. This fitment, now available toany cyclist as a separate unit, is priced at 8s. completewith pulley. Garner's Tool

News Especially useful for the small workshop is this14/b. cast THE May issuesteel anvil marketed by the K.andL. Steelfounderr and The new Exide side -filling battery. of this handyEngineers, Ltd., and T. C. Jones and Co.Ltd., 25-29, booklet,published Bulwer Street, Shepherds Bush, London, W.12. Mindfulofthisinaccessibilityofthe by T. Garner and Son, Ltd., of battery on many vehicles, The ChlorideRedbrook Works, Gawber, Barnsley, containsto a scale of +in. to the foot, and is 2rft. Tin. Electrical Storage Co. Ltd., have designeda review of small tools and equipment, eachlong overall.The weight of the model is a new lidforExide-Ironclad and Exide-classoftoolbeingpresentedinalpha- Iton 7 cwt., and the total man hours ex- batteries.This embodies an inclined fillingbetical order for easy reference.There ispended inbuilding the model was 6,900. aperture so that it is easy to top or fill upsome useful information about the GarnerThe text and illustrations, showing the model from the side. hirepurchaseplanandseveraldetailedliner in various stages of construction, give quotations for lathes and other tools.Owingthe reader a good idea of the work involved In this new lid the filling evening is located in producing such a fine example of the at one side andisinclined outwardsto model -maker's craft. facilitateside filling, while the gas vent is centrally situated.As the side -filling plug is blind there is no risk of acid splash when THE the vehicle is cornering. Batteries with the normal vertical filling MODEL AEROPLANE opening arrangementwillcontinue to be HANDBOOK made andoperatorswillbe abletofit batteries with either central or sidefilling, An Important New Work depending on the location of the battery on By F. J. CAMM the vehicle. 312Pages, 303 Illustrations, 12, 6, by post 13/-. A Short History of Model Aeronautics :Principles Ripmax Ltd. of Design ;Airscrews :Wings :Undercarriages : Folding Airscrews-Retractable Undercarriages - /IR. C. A. RIPON, who has over 4o Fuselages :The Elastic Motor ;Gearing and lvl years' experience of air modelling and Special Mechanisms ;Making Model Wheels ; Geared Winding Devices :Model Aeroplane Sta- is one of the leading lights of the Northern bility :Downthrust : ModelPetrolEngines ; Heights Model Flying Club, hasrecently Adjusting ModelPetrol Engines Compressed Air Engines ;How to Form and Run a Model Aero commencedbusinessunderthetitleof Club ;F.A.I. and S.M.A.E. Rules :S.M.A.E. Com- petition Cups :A Lightweight Duration Model ; Ripmax, Ltd., 39, Parkway, London, N.W.r. A Wakefield Model :A Farman Type Model Mono- He can supply all model -makers' ,requisites. plane A Composite Model :Ornithopters-or Wing -flapping Models ;A Low -wing Petrol Mono- plane :A Duration Glider ; Winch -launching Model Gliders ;A Streamlined Wakefield Model Synchro Switch Handlebar Gear Control A Model Autogiro A Super Duration Biplane .Flying Model, Aeroplanes ;A Flash Steam Plant PRODUCTION of this precision -engineer- Model Diesel Engines ;" Weights of Wood ;Plano ing component, successfully introduced Wire Sizes. Areas and Weights ;Schedule of British by the Hercules Cycle Co.last - year, has Records.Fully Indexed. now reached apoint where the synchro Published by switch can be offered through the trade as CEO. NEWNES LTD, TOWER HOUSE, a separate unit for fitment to any make of SOUTHAMPTON ST., STRAND. LONDON, cycle, in addition to being fitted as standard w.c.2. to Hercules 3 -speed machines. The Synchro Switch handlebar gear conn ol. 354 NEWNES PRACTICAL MECHANICS August, 1949 Letters from Readers Cycle Rear Lights part of methanol combines with 96device, being very easily made.It gives years SIR,-Withreferenceto A.R.Jones' 64of trouble -free service.The only materials letterin the May issue of PRACTICAL.parts of oxygen. required are an old dynamo yoke and a strip MECHANICS on the question of rear lights,And, since air is'5th oxygen of mild steel or strap iron min. by tin. by I have thought of an idea which does not part of methanol combines with approxi- ,in.Mine has been in constant use for over entail much work and which eliminates themately 7 parts of air: to years, with different pressure stoves.- uncertainty of wondering whether the rear It maybe inferredtherefore from the Ihave been,since1936,anadmiring lamp isalight.Itisto connect the rearabove figuresthat methanol -mixturesforreader of PRACTICAL MECHANICS and lamp in series with the front lamp, as showninternal combustion engines require twicelookforwardtoevery issue.-G.W. in the sketch.A dynamo rear lamp which istherecommendedfuelconcentrationforHOUGHTON (Chester). insulatedfromthe frameisused and apetrol. lead attached which is connected to a battery However, it is inaccurate to effect a com-Repairing Broken Records in the saddle bag, the other lead being takenparison between the two fuels unless each is SIR,-Here is a method I use for repairing toaswitch mounted onthe handlebars,compressed to the maximum possible pressure broken records, and itis much cleaner then to a front lamp, which is a battery -typebefore ignition.This reduces the proportionthan the sticky paper method.Take four converted by fixing a wooden block in placeof unburnt gases to a minimum, and thus thepins and cut the heads and points off with a of the battery with abrasscontactstripexplosions more nearly approximate to thepair of pliers.Get someone to -hold the pieccs screwed to it';the circuit is completed viaideal equations given above. Itis commontogether (the grooves can be adjusted under a theframe. knowledge that beyond certain pressures fuelsmagnifying glass) and then hold one of the have a tendency to detonate, giving rise to the Front lamp Rear .lamp phenomenon known aspre-ignition.The limiting pressure inthe- case of petrol is 01191 Sovitch approximately9olb.persq.in.,whereas methanol may safely be compressed to as Brass strip mounted much as 18o1b. per sq. in.Hence to run a on block min petrol engine efficiently on methanolitis Battery or dynamo ..1..., essential to raise the compression ratio until -0---- Frameearth VP the compression pressure approaches r8o1b. Front and nar lamps of a cycle connected inper sq. in.This point, I feel sure, has been series. neglected by your correspondent and is the cause of the poor starting, slow running and Failure of the rear lamp will be_ noted bylow mileage to the gallon he mentions.It the front lamp also going out.There isalso accounts for the rich mixtures he has to just one more point-if a 3 -volt battery isuse to get his zFrigine to run at all.I am used two 1.5 -volt lamps should be used, orawarethatitisdifficulttoincreasethe if a 6 -volt dynamo, two 3 -volt lamps.Thecompression ratio of two-stroke engines with current rating should be the same for botha deflected top pistonwithout altering the lamps.-R. VERLANDER (Theydon Bois). position of the top of the piston relative to the ports, but Mr. Asher makes no mention of the Methanol as a Fuel point at all.I can only assume, therefore, that he has not considered it. SIR,-MayIdraw attentiontocertain inaccuracies which appeared in a letter In conclusion, my ownexperienceswith A simple method of ret airin; I ro':en r, cords. from Mr.S.Asher, Gorleston-on-Sea,inmethanol have shown that my motor -cycle the June issue.I feel prompted to do this inwill run much quieter, cooler and give mepins in the. gas with the pliers until red hot view of the large number of your readers whogreateraccelerationthanpetrol. I canand push it into the outside of the record, may be misled as to the capabilities of methanolobtain a little over half the mileage to themaking sure not to touch the grooves. Repeat as a fuel for motor -cycles. gallon that I used to obtain with petrol. with other side of the record, and then do the Hoping the above information will be ofsame on the inside near the paper, again Mr.Asher's carburation figuresareuse to any of your readers contemplating themaking sure not to touch the grooves ;the theoretically unsound, and I suggest that heconversion of their motor -cycles to methanol.repair is then completed.It will be found isusing far too low a compression ratio.-S. A. SPOUSE (Chippenham). after four or five playings that the clicking The equations for the relevant reactions may noisereducesconsiderably.-A. COMBER be represented as follows : (Wallington). (t) Petrol:This is a mixture of hydro-Workshop Soldering Stand carbons, but the main constituents are pentane SIR,-The accompanying sketches show aFountain Pens (C,,H,2) and hexane (C611,4). simple soldering outfit for those having (a) CsH..80.,oxidises to 5CO2-: 6E1,0.workshops without gas or electricity.The SIR,-I feel I cannot let a statement of Mr.E. W. Baigent (Juneissue)go Hence, substituting the molecular weights :device is a most useful, almost indispensable,unchallenged. 72 parts of pentane combine with 256 parts Vee Sown Out Of oxygen. He says. " why not pour the ink into the part of pentane combines with approxi- Yoke To Prevent barrel-petrol lighters do not have self -filling mately 3.5 parts oxygen. Soldering Iron gadgets,so why fountain pens ? " (b) 2C,H190,oxidises to6CO, Rolling OP I am a user of both fountain pen and lighter 71120. and my wife does not care to see patches of Again, substituting the molecular weights : ink on the carpets, nor do I care to fill my 172 parts hexane combine with 304 parts of pen over the kitchen sink every time this requires doing.When Ifill my lighter by oxygen. pouring in petrolI frequently drop petrol part hexane combines with approximately Strap Iron Bracket on the carpet but this does not bother me 2 parts of oxygen. Bolted To a scrap-it soon dries up.-C. B. Lancaster Since it may justifiably be assumed that 3ynimo )43 petrol, a mixture of approximately half pen- (Lattenbury Hill). tane, half hexane, will require a proportion of oxygen intermediate between the above values,itfollowsthat A NEW VEST POCKET BOOK part petrol combines with 2.75 parts of Brush Inspection oxygen or, since airis 5th oxygen NEWNES METRIC & part petrol combines with approximately Holes As Air Intik? 14 parts of air. DECIMAL TABLES (2) Methanol or methyl alcohol (CH,OH) oxydises to form carbon dioxide and Water, By F. J.CAMM viz. : Legs OF Primers 3/6 or 3/9 by post from 2C4 -10H -! 30, oxidisesto 4H.,0 ' 2CO2. Substituting the molecular weights Cut Off Here Geo. Newnes, Ltd., Tower House, 64 parts of methanol combine with 96 parts Southampton St.,Strand,W.C.2. of oxygen. A hat dv solderirq stand rot the wor'd-ench. August, 1949 NEWNES PRACTICAL MECHANICS 355

SPECIALISTS CJA BLES IN LIGHT r' MY FORD MACHINE BEESTON TOO LS ' NOTTINGHAM (ENGINEERING CO. LTD. BEESTON NOTTINGHAM ENGLAND)

DO NOT FAIL TO VISIT THE24thANNUAL MODEL ENGINEER EXHIBITION NEW ROYAL HORTICULTURAL HALL, VESTMINSTER AUG. 17th to AUG. 27th inclusive DEMONSTRATIONS OF MYFORD METALWORKING AND WOODWORKING LATHES AND ATTACHMENTS WILL BE GIVEN DAILY M inFOR1D) 3J HEAVY DUTY LATHE TYPE M.L.7.

Mk STAND6. 356 NEWNES PRACTICAL MECHANICS August, 1949

ELECTRIC ENGRAVERS. -Powerful instruments in flat case.Suitable for GALPINS TAKE UP PELMANISM dot collars, tool marking.Writes on glass, metals, plastics. Plugs into any ELECTRICAL STORES lampholder.A.C. Mains model, 200-240 408 HIGH STREET,LEWISHAM, For Courage and Clear - Thinking volts or 8v. battery. Price 42/8. Post 9d. TELEPHONE SETS,comprising 2 LONDON, S.E.13 G.P.O. hand phones, 2 bells. 2 pushes Telephone : Lee Green 0309. Near and 80ft. twin wire.Price 4816, post free.Makes an excellent inter -office, Lewisham Hospital The GrasshopperMind. WhatCan You DoAbout It ? works or domestic installation. Really TERMS : CASH WITH ORDER. NO C.O.D. professional instruments. Brand new. YOU know man withthe Take up Pelmanism now ! A not rubbish,Single instrument. 11/11. THURSDAY EARLY CLOSING Grasshopper Mind' as well ascourse of Pelmanism brings out the MOTOR. -4-6v.drybatterydriven, MAINS TRANSFORMERS, Input 200- wliset11 3mdda. e, powerful, 1143.Illustrated 250 v., 50 cycles. in steps of 10 v.Output you know yourself. His mind nibblesmind's latent powers and develops 450101450 v. 250 mla., 4 v.4 a.,5v. 4a., at everything and masters nothing. them'to the highest point of efficiency. BATTERY CHARGERSfor A.C. 6.3 v. 8 a., 6.3 v. 8 a., 6216. Ditto 450101450 Itbanishessuchweaknesses and MAINS. FOR CHARGING 2 -volt accu- At home in the evening he tunes mulators at 4 amp. Parts with diagram, v., 250 mla., 6.3 v. 4 a., 5 v. 4 a., 4 v. 8 a., defects as Mind Wandering, Inferior- 15,-. Complete. 211. Postage 10d. 4 v. 8 a., 601-. Another 50013501013501500 inthewireless -tiresofit -thenity and Indecision, which interfere FOR TRICKLE CHARGING; CAR v.. 250 mla.. 6.3 v. 8 a.. 0, 4, 5 v. 4 a. twice, glances through a magazine -can'twith the effective working powers of CELLS, parts with diagram.Output 6.3 v. tapped at 2 v. 2 a., 6716.Another get interested. Finally, unable to 11 amps. for 6v. cells. 26,6 set. For 350101350 v., 300 mla.. 4 v. 8 a., 4 v. 4 a., the mind, and in their place develops 12v. cells. 28,8 set.Post 100. concentrate on anything, he eitherstrong, positive, vital qualities, such Complete on Open Metal Base. 15 6. 6.3 v.4 a.. 6.3 v. tapped 2 v.2 a.,5716. goes to the pictures or falls asleep Post 11-. See List for larger sizes. Another 500101500 y., 303 mla., 6.3 v. 8 a., as Optimism,Concentrationand PHOTO -ELECTRIC CELLS. -For. all 6.3 v. 8 a., 6.3 v. 4 a., 4.4. a., 5 v., 4 a., 6716. in his chair.At his work he alwaysReliability, all qualities of the utmost sound films, high fidelity production. EX-R.A.F. MICROPHONE TESTERS takes up the easiest job first, puts itvalue in any walk of life. speech and music. Small tube size. down when it gets hard and starts xx anin. 22dirt8...28 8. Midget tube, (new). These consist of aFerranti 0 to The general effect of the training is lfn.COMPI,KIE 450 rnlarnp. scale meter shunted to something else. Jumps from one thingto induce an attitude of mind and a OPTICAL SYSTEM for 1 m)a incorporated Westinghouse Recti- to another all the time. 35 or 18 min: sound film. 2in. long. fier,the whole encasedinpolished teak personal efficiency favourable to the umv 2i.4iceis 0.00051n. light case,calibratedatpresent 0to 10v., There are thousands of these peoplehappy management of life. line,Price 251- each. with Grasshopper Minds' inthe ELECTRIC LIGHT CHECK METERS world. In fact, they are the veryHalf -fees for serving and ex -Service ECONOMIC ELECTRIC CO., (Watt -Hour). A.C.50cys.,2001250v. people who dotheworld's most 64,London Road,Twickenham, 5 amp. load, 1816, post 21-.10 amp., 211-, membersofHisMajesty'sForces. tiresome tasks -and get but a pittance Middlesex. Tel.: POPcsgrove 1313 post 2)-; 20 amp., 251-, post 21- ; also a few (Apply for Services Enrolment Form.) only Pre -Payment 11-slot type, 20 amp. for their work. They do the world's load,lesscoin box, complete withsyn- clerical work, and the routine drudg- The Pelman Course is. fully de- chronous Motor, 351- each, carriage 376. ery. Day after day, year after year - scribedinabook entitled," A SUPER SPECIAL OFFER METERS,allnew, endlessly -they hang on to the jobs The Course is boxed. Moving Coilfirstgrade instru- thataresmallestsalaried,longest Science of Success." POLISHING HEAD ments. 0 to 20 v.,101- each, or 3 for 251.; houred, least interesting, and poorestsimple and interesting, and takes up 0 to 40 v.,1216 each ; 0 to 10 amps., 151 - very little time ;you can enrol on the each,all 2in., scale, 0 to 20 v., A.C., cali- futured ! most convenient terms.The book brated 50 cycles, 251- each; 0 to 40 amps., will be sent you,'gratis and post free, Al±k therrno-coupled, 251- each. MAINS TRANSFORMERS, all 2031250 WhatisHoldingYou Back ? on application to :- AS ILLUSTRATED. v., 50 cys., I pi -wise, input, output 700101700 Ifyouhave a Grasshopper PELMAN INSTITUTE, v., 70 mla., 4 v. 21 a.,12 v. 1 a., 301- each. Mind' you know that this is true. 27/6 Another 5251525 v.,ISO rnia., 6.3v. 5a., 130, Norfolk Mansions CARRIAGE PAID. And you know why it is true.Even _ 5v.3a.,37/- each.Another 2,350 v. at (without chuck 20 1 500mla.,85/-each. MainsSmoothing the blazing sun can't burn a hole in aWigmore Street, London, Dila:DrivingPulley.fullyshrouded. Chokes,10 Hy.103 mla.,61- ;150 mia., piece of tissue paper unless its rays (Edablished over IN years) Callers welcomed SelfLub.icatingBushes, 3 Jawtin.

816 ; 350 mla.. 251- : 5 Hy., 250 rnla.,1716. are focused and concentrated on one PELMAN (OVERSEAS) INSTITUTES : PARIS Capacity Chuck.(The case is sprayed 176 Boulevard Haussrnann. AMSTERDAM : an attractivemetallic blue). From EX-R.A.F. ROTARY CONVERTERS, spot. A mind that balks at sticking Damrak,88. NEW YORE : 271.North 12 v., D.C., input 230 v. A.C., 50 cys.I phase to one thing for more than a few Avenue. New Rochelle.MELBOURNE :396, M IR 'I' (1 XS, at100 w. output. 851- each, carriage 316. minutes surely cannot be depended Flinders Lane.JOHANNESBURG :P.O. Box 13, CAMDEN ROAD, Ditto 24 v. input, 651- each, carriage 316. upon to get you anywhere in your 4928. DURBAN :Natal Bank Chambers WALTHAMSTOW, LONDON, PRE -PAYMENT II- SLOT ELECTRIC (P.O. Roc 1489). DELHI :10. Alipore Road. E.17. LIGHT CHECK METERS, 2001250 volts, years of life ! CALCUTTA :102, Clive Street.

50 cys. I ph.2)amp. load.301-each, carriage3)6 ; 5 amp. load, 351-, carriage Mallorders10 : 316. 10 amp.load, 4216 each. carriage 316. THE LATEST TYPE MAINS TRANSFORMERS INPUT, WALTON'S WIRELESS STORES THE WORLD'S 2001250 voltsin steps of10 volts output FIXED CRYSTAL DETECTOR 203,STAVELEY ROAD, tapped6, 12 and 24 volts at 25 amps., GREATEST BOOKSHOP 651- each, carriage 316.Another 230 volts THE CRYSTAL VALVE WOLVERHAMPTON input with 3, 4 volt windings at 5 amps., as used in radar receivers. Remember all is Carriage Free to any 251- each. Another 200)250voltsinput address in GreatBritain. output 6,12 and 20 voltsat415 amps., Overall size tin. x lin. 2716 each, post 116. AMAZING RESULTS MOTOR ALTERNATORS, ex-R.A.F., Industrial Type 4FOR.BOOKS ' as new, 230 v. A.C. 50 cys. I ph. input. 31- each, postage 214. Adjustable Lamp. New and secondhand Books Output 250 v. 625 cys. I ph. at .24 amps., complete with 751- each. Ditto1,725 cys. output, 851-. Protective Tube and Fixing Brackets, Reflector. less on every subject.Stock of Please note both these machines require a 3d. each. 0Lampholder and 3 million volumes 24 v. D.C. excitation. Wiring instructions for a cheap, simple Wiring.22/6. Large Dept. ror Technical Books SYNCHRONOUS MOTORS 2001150 but high quality Crystal Set included 4 119-125 CHARING CROSS RD. VOLTS, 50cys. I ph.,convertibleas with each Detector. Clock Movement, 1216 each. Resistances LONDON, W.C.2 350 ohms to carry .25 amps. (fixed) but can 50v. 50 cycle 3 ph. Gerrard 5660 (16lines) easily be fitted with a slider, 816 each. CRYSTAL SET Motor. complete in Open 9-6 (inc. Sots) EX-R.A.F.I.F.F. UNITS CONTAIN- INCORPORATING THE LATEST Transit Case. 131 - ING 10 VALVES, EF50s, SP61s. EA50s, CRYSTAL VALVE etc.,power supply Motor generator 12 volts D.C. input 450 volts. 50 Miami's. Adjustable Iron Cored Coil Magnificent Gun output, and many other useful components RECEPTION GUARANTEED Sighting Tele scope. PERFECT PASTIMES FOR as new, 3216 each. Ditto with a 24 volt complete in PLEASURE AND PROFIT input Generator Valve sequence slightly Polished wood cabinet, 151- post 9d. Stowage Box. 67)6. different. Generator can easily be converted Send S.A.E. forlists of copper wires, The Magazine Craftwotketlists to run asa Motor off A.C. mains, 301 - screws,nuts,paxolintubes, ebonite. Send S.A.E. for ourlatestIllastraled Tools,Materials, Equipment & each. tufnol rod and panels. etc. You 011 be amazed at SHORT WAVE COUPLING AERIAL Bargain List. Fittings for all profitableCrafts the value we offer. UNITS (Wayemeters), absorptiontype POST RADIO SUPPLIES atHome ;and Instruction wound with 20 and 12 gauge Silver plated 33 Bourne Gardens, London, E.4 Cal ler, on1.4: WALTON'S WIRELESS wire, 2'to 51.meters, 316 each.No. 19 STORES, 48. stanord St ree 1.1V ton. Books, Booklets, and Leaflets on VARIOMETERS containing H.V. Condenser Leatherwork, Lampshades, 4 Instrument Rectifier,useful for parts,316 Plastics, Toys, China and Glass each. EX -NAVAL TELEPHONE HAND- CHEMISTRY APPARATUS Painting, Art Jewellery, Toys, SETS BAKELITE PATTERN (self - Send Stamp for Models and a hostofother energised), no battery required, complete COMPLETE PRICE LIST PATENTED Crafts that are Different. with wallbracket (new), 151-perpair, WORM DRIVE post 116. Ditto complete with Buzzer Send Illd. forspecimen ringing mountedinweather proof box, Booklets: CLIP andfull liststo :- 24voltrequiredforenergisingBuzzer only, complete with Hand -set,151- each, "Experi- Dept. 2, HOMECRAFTS, or 251- per pair. ments" 7d. Albion St., Broadstairs, Kent EX -NAVAL NAVIGATION INSTRU- "Formulas" MENT Containing F.H.P. 230 volt A.C.I cod. D.C. Motor, first grade ,3lin.scale ohm- " Home INSULATED COPPER WIRE. meter.Standard Potentiometers 2, other Chemistry " Enamel, silkor cotton covered.all Resistances both variable andfixedalso gauges 13 S.W.G. to 44 S. W.G. Lea there'd some very useful Gun-metal -Gears (new), 2/3 insulation.Empirecloth.armature 651- each. carriage 101-. Post Paid sleeving, commutators, etc. * wn,. N roa. THE FINEST MAINS VARIABLE STUD SWITCH - R r/ 12. cur IN THE SPECIAL OFFER.-A.C. Sinxi0 IVORLD. Pilvsn Electric Motors. New. I h.o ARM TYPE. Resistances 25Studs, SO BECK0,4d. A) £5 10s. i h.p. £6 10a. 1 h.p. £7 12s ohms to carry1.4 to 9 amps., 301- each. 60 HIGH STREET, ::end for Ms). 10 ohms, to carry 9114 amps., 3216 each, L. C. NORTHALL. 18. holly it".. many other types in stock, please forward Stoke Newington. London, N.16 L ROBINSON&CO. LTD Quinton, !firming:1min. 32. your enquiries. g.iiinqbaynhunt August, 1949 NEWNES PRACTICAL MECHANICS 357 Removing You should read one of the several modern textbooks CarbonDeposits fromI.C.on the principles of colour -photography, such as: Engines D. A. Spencer:_Colour Photography in Practice. T BELIEVE that certain preparations are obtain- R. M. Fanstone :Colour Photography. able for removing carbon deposits from the K. Heney : ColoUr Photography for the Amateur. QUERIES0,4 interior of internal combustion engines withoutThese 'should be available in your nearest reference dismantling. library. I shall be glad if you will inform me where I can get one of these preparations.I should also beFire'proofing Fabrics interested to know how they work, as I have always CAN you supply me with the names of chemicals ENQUIRIES understood that carbon can only be removed by used for fireproofing clothes, also instruc- burning with an oxygen flame or by mechanicaltions how to use same, and where they can be methods. -D. G. Preston (Bury). obtained. -T. Menamay (Millerston). THERE are no preparations which are capable of7`HERE are various chemical solutions which may be Astampedaddressedenvelope,threepenny A used for fireproofing fabrics.Some are better stamps, and the query coupon from the current dissolving carbon from the interiors of internalthan others for any given type of fabric, but since you issue, which appears on page 88 (THE CYCLIST), combustion engines. At the best, any such preparationsdo not mention the type of fabric which you have in must be enclosed with every letter containing a can only loosen loosely adherent carbon masses andmind we can only advise you to make your own trials. query. thereby dislodge them. There is no known solvent of Every query and drawing which is sent carbon (apart from molten iron and a few other similar In every case, the fabric material is soaked in the cold must bear the name and address of the reader. impossibilities), so do not be deluded by statements tosolution for four or five hours, after which it is with- Send your queries to the Editor, PRACTICAL the contrary. drawn, passed through a'mangle and hung up to dry. MECHANICS, Geo. Newnes, Ltd., Tower House, Note particularly that no chemical solution will confer SouthamptonStreet,Strand, The carbon " solvents " to which you refer comprise London,W.C.2. nothing more than alkaline solutions.They vary fromabsolute fire resistance on a fabric.If the surrounding strong solutions of caustic soda to mildly alkaline solu-temperature is high enough the fabric may smoulder tions such as various mixtures of sodium metaphosphates,and thus become destroyed, but it will not inflame.The Glazing Plaster Casts metasilicates and percarbonates, with or without suitableonly too per cent. fireproof fabrics are those which are admixture with a wetting agent, such as Teepol-X.woven from asbestosfibre.These will withstand POULD you please give me some information Such solutions are effective inasmuch that they serve towhite heat. `-regarding plaster casts, and in particular:dislodge loose carbon particles, but they do not dissolve Any of the following solutions may be used for your (a) What is the process of glazing plaster casts ?such particles. Hence, the loosened matter has to bepurpose: Also, do the glazed casts have to be baked in a removed by swilling or by scraping. (a)Sodium tungstate a part kiln ? If you want to experiment with one such preparation, Water .. 9 (2) Are there any books on the subject ?-here is a suitable formula : (2)Borax .. t2parts H. Phillips (London, N.W). Sodium carbonate ..6oz. . Epsom salts.. (,) PLASTER casts (and by the term" plaster " Caustic soda .. .. 20Z. Water .. 8pa(3> kJ) we presume you refer to plaster of Paris) are not (3)Alum partsS Trisodium phosphate.. 20Z. Sodium phosphate usually glazed in a kiln.Their glaze is merely an Sodium silicate .. a oz. .. a applied enamel, a base or ground enamel being brushed Water .. .. a gallon. Water .. .. 20 ,, or sprayed on, and the decoration hand -painted on theTo the abOve may also be added a fluid oz. of a wetting (4) 15 parts cast. agent such as Teepol-X, which is now being produced BoricSalarnmaciodniac .. 6 ,To prevent the absorption of too much of the enamelby Shell Chemicals, Ltd., Strand, London, W.C.2. it is a good plan to brush over the cast a warm gelatine Water .. 100 solution, one containing, say,no parts of gelatine When making up any of these solutions use hot water dissolved in 90 parts of water.After the cast has dried,Laying Cement Paths and dissolve the ingredients one by one. it should .be painted with a flat white paint, and, after All the above ingredients can be obtained from a that, with any enamel paints which you may haveT AM contemplating the laying of cement paths local pharmacist.If you have difficulty in obtaining available either as oil paints or as cellulose enamels. 4. around my house and garden, butI cannotsodium tungstateapplyto your nearest chemical For glazing purposes the base material must be ofestimate the amount of material which will bewholesaler or to Messrs. Vicscns, Ltd., 148, Pinner baked clay, which is much more enduring at highrequired to complete the work. Road, Harrow, Middlesex. temperatures than mere plaster. (2) There are no books specifically on the subject Lens for Home Cinematograph of painting plaster casts, but the following books will, Readers are asked to note that we have AM desirous of making a home cinematograph. mostlikely, be of interest and use to you : discontinued our electrical query service. Could you advise me as to the type of lens S. W. Anthonies : Pottery and Modelling. Replies that appear in these pages from requirlkd to make a picture about aft.square C. F. Binns : The Potter's Craft:APractical Guide at a distance of about 'oft. from the lantern ? for the Studio and Workshop. time to time are old ones, and are pub- Also, could you tell me if any ex -Service gadget R. Lunn: Pottery: A Handbook of Practical Pottery lished as being of general interest.Will now on the market would provide a suitable for Art Teachers and Students. readers requiring information on other Modelling with Self -Setting Clay.(Dryad Leaflet). lens ?-A. Troupe (Sunderland). Modelling and Casting for Children. (Dryad Leaflet.) subjects please be as brief as possible H. and D. K. Wren : Pottery : Finger -built methods. with their enquiries. Itispossible that Dryad Handicrafts, Ltd., St. Nicholas Street, Leicedter, may also have some pamph- THE P.M. BLUEPRINT SERVICE lets of the same or allied subjects. The area to be laid is approximately :Length, sooyds. ;width, aft. 6in. ;depth, sin. 12FT. ALL -WOOD CANOE.* New Series. No. I. Can you give me an estimate of the amount of 3s.6d. Treatment of Old Furniture material required, also a mixture which, would make strong and durable paths ?-S. Copeland 10 -WATT MOTOR. New Series.*No. 2.3s. 6d. T HAVE an old chest of drawers which was (Ilford). COMPRESSED -AIR MODEL AERO ENGINE. 4.mahogany stained and polished. To remove New Series.No.3. Ss. this colour I washed the chest with strong caustic A GOOD cement mix for your purpose will be : soda dissolvedin warm water.The drawers Portland cement .. a part (by volume) AIRRESERVOIR FOR COMPRESSED -AIR AERO ENGINE. New Series. No. 3a. Is. now are dry and perfectly free from stain and Sharp sand .. 2,, " SPORTS " PEDAL CAR.* New Series. No. 4. Ss. polish, but on examining the wood Ifind the Fine sand or grit grain is comparable to that of ash or elm. The Half the depth should be filled loosely with i rregularly- F. J. CAMM'S FLASHSTEAM PLANT.* New information I require now is how to treat theshaped stone fragments, but each fragment must nor be Series. No. 5. 5s. wood so as to get as reasonable a furniture finishmore than approximately tin. diameter orwidth. SYNCHRONOUS ELECTRIC CLOCK. New aaslipgitsiobal, asopptohaartatnhoeo.chezt IrdAerya will have Before attempting the path proper try out the above w(Brisrtre mix on a spare piece of ground, this being a sq. ft. in Series. No. 6.5s. IT is not common to find these chests in ash or elm,area.Find out the weight of the trial sample and, ELECTRIC DOOR -CHIME. No. 7.3s. 6d. but possibly it may be made of birch which was, atremembering that one -quarter ofthis is composed of ASTRONOMICAL TELESCOPE.New Series. one time, used for furniture -making in this country.cement, you will be able to work out the amount of No. 8 (2 sheets).7s. cement needed for the whole job. We cannot do this CANVAS CANOE. New 9. Since the chest is an old one, we do not think that youfor you in view of the fact that you will be using larger Series.No. 3s. 6d. will ever get it back to a light oak shade.In fact, in DIASCOPE. New Series. No. 10.3s. 6d. our opinion it would be a pity to make any such attempt, stones, which will reinforce the material and whose since by so doing you would destroy whatever antiquepresence in the concrete will render less of the material EPISCOPE. New Series.No. II.3s. 6d. value the chest may have. necessary. PANTOGRAPH. New Series.No. 12.Is. 6d.. By &eating the chest with strong caustic soda you 120 CAR* will have lightened the wood almost to a maximumColour Photography (Designed by F.1. CAMM), extent.You must now give it a thorough and patient 10s.6d. per set of four sheets. sandpapering all over until you smooth down the roughT. WISH to undertake a little experimenting in surface which the caustic soda treatment must have colour photography, and shall be pleased if MASTER BATTERY CLOCK. you will inform me on the following point : . given to it.Then, if you wish to keep the wood at its What is the formula for the active emulsion Blueprints (2 sheets), 3s. 6d. lightest colouration, simply give it two thin coats of aused on films and plates (all colours), and the Art board dial for above clock,Is. clear cellulose varnish. method of applying this emulsion to glass plates ? OUTBOARD SPEEDBOAT On the other hand, if the chest has to have an antique-F. K. Morton (Leyton). 10s. 6d. per set of three sheets. appearance, give it a liberal treatment with a mixture of SUPER -DURATION BIPLANE* raw linseed oil andturpentine(applied hot).Let theIT will be impossible for .you to prepare for yourself Full-size blueprint, 2s. oil soak in for a week or more, then give the wood a photographicemulsionsfor natural colour light varnishing with shellac polish.Finally, give it aphotography.In the first place, all successful emulsions The 1-c.c. TWO-STROKE PETROL ENGINE' rubbing down with any good household wax polish or,of this type are made up to highly secret formula, and Complete set, 7s. 6d. better still, with a solution of beeswax in turpentine.their method of preparation is also secret. Again, plates STREAMLINED WAKEFIELD This treatment will, of course, darken the wood. and filmsfornatural colour -work are mostly of the MONOPLANE -3s. 6d. If you insist on the wood being whitened brush over " composite -emulsion " type.That is to say that the LIGHTWEIGHT MODEL MONOPLANE the bare woodwork a thin paste of chloride of lime andfilmorglass substratum receivesseveral separate Full-sizeblueprint,3s.6d. water.Let this dry on.Then brush over the surfaceemulsions, one on top of the other, with all sorts of either dilute hydrochloric acid or dilute acetic acid.inter -layers of varnish, etc.,between them.Unless an P.M. TRAILER CARAVAN* One part acid in three parts water is the strength to use.individual was highly skilld in this delicate work, and' Complete set,10s. 6d. Do this out of doors and preferably in the sunshine,was in possession of factory methods and secrets, he P.M. BATTERYSLAVE CLOCK* -2s. since the latter facilitates the bleaching action.Repeatwould not be able to prepare any such emulsions for the process if necessary, then swill off thoroughly withhimself.Even textbook descriptions of principles will Theabove blueprints areobtainable, postfree, plenty of water.Allow to dry slowly. Sandpaper well,hardly help in this connection. froM Messrs: George Newnes, Ltd., Tower House, then finally give a light coating of a clear cellulose Again, the processes of developing andfixingof the SouthamptonStreet,Strand,W.C.2. varnish:This will give the lightest possible effect onnatural -colour emulsions depends greatly on the actual the oodwork. nature of the emulsions and the process which is being At the same time, if your chest is of any artistic orused.There is no general process for developing An *denotesconstructional details are available,free, antique value, this bleaching treatment will ruin it from colouremulsions.Each type of emulsion needs special withtheblueprint. these standards. conditions of development. 358 NEWNES PRACTICAL MECHANICS August, 1949 YOU can use any type of projection lens or objective What further treatment do you recommend ?-magnetiser which will magnetise one pair 'of adjacent for your purpose, and since you ask for usefulK. Holdsworth (Bradford). poles only.The poles of this magnetiser should bed data on this matter, we append below three formulaYOU have been wrongly advised in applying eitheras closely as possible to those of the Alnico magnet from which you will readily be able to calculate projection lime or a sealing compound to remove tar from aand should have an area practically as great as these requirements under any varying conditions. woodwork surface.The tar should have been scrapedof the magnet.The distance between the poles of Let or dissolved away before any fresh paint was applied,the magnetisercould be made as small as a lain. or lilt., D =-Distance of lens from screen. since the oils in tars are very penetrative and will makethe magnetiser being shaped so as to allow for a very F- Focal length of lens. their way through most paints. large number of ampere -turns being used. X -Diagonal of frame (i.e., of single picture) of The only radical way open to you now is to remove film. the whole of the paint, tar, etc., by stripping the entire Y =Diagonal distance of projected picture. wood surface and exposing the bare wood.To do this Then :- you can make use of a proprietary paint -strippingPlaster Mould Lubricants D =YxX composition, which softens the paint and thus allows THAVE been making ornamental models from it to be scraped off readily, or, alternatively, you can use plaster of Paris, and am experiencing con- F a solution of caustic soda made by dissolving one partsiderable difficulty over the " greasing " of the Y =-D X of caustic soda in four parts of water.Add a littlemoulds.The latter are also made of plaster of F ammonia to this solution so that it smells faintly.ThenParis.I have been using soap and water for F =D

circuit of the permanent magnet should not be inter-connection, that the incorporation of up to to or 12 rupted until this is placed in the apparatus in which it per cent. of powdered asbestos into any of the mixtures Removing Tar from Woodwork is to be used.In your case this might be accomal iched imparts strength to the products and greater freedom T HAVE a country bungalow, some of the woodby placing a soft iron or mild steel disc on each sidefrom cracking, although a rougher surface is produced. of which has been smeared with tar.Onof the magnet before removing it from the magnetiser, Powdered asbestos may be obtained from Messrs. applying fiat paint, the tar penetrated the paint.or sliding the magnet into a mild steel or soft ironTurner Brothers Asbestos Co., Ltd., Rochdale, Lanes, I was advised to apply lime to the affected parts, cylinder. We presume the poles of the magnetiser areor from Messrs. Jas. Milne Cooper and Co., Ltd., but finding this unsatisfactory the surface wasin contact with the Alnico.As the current is onlyKobar Works, Bradford, Yorks. treated with a sealing compound, after which arequired for very brief periods it may be possible to Other stone -making materials (lump or powdered) finishing coat of hard gloss paint was adlei.in7.rease the magnetising force considerably by arranging may be obtained in relatively small amounts from This is now peeling off, possibly due to the in:eneethe coils in series -parallel instead of series. Messrs. A. M. MacCarthy, 37, Sandfo d Road, Moseley, heat of the sun. Another suggestion is that you construct a power.ulBirmingham, 13. August, 1949 NEWNES PRACTICAL MECHANICS 359 ACRALAC Other extremely good CELLULOSE THINNERS ACRA finishesare for thinning, and cleaning ACRALAC ART ENAMEL kralac 0.P. P. brushes and hands 2 oz. 2 oziar I/4and ACRALAC N. 4. POLYCHROMATIC ()MODEL DOPE METALLICCELLULOSE opectallitiptfrudaza LACQUER, 2 oz. jarl Ask to see them, and for the very best FOR ALL POWER MODELS ;74 Glueing job, always use ACRABOND Highly Resistamt You will get brilliant results with these fine 111160 Petrol, Diesel Oil, Ether. dopesinBlue,Yellow,Vermilion, Marigold,also ACRALAC Black,Ivory,Gold andSilver. Suppliedby yourCLEAR "HIGH FLASH" usual Model Shop withdetailed instruction folder SHRINKING DOPE The last word in Model Dopes Made 2 oz. Jar1/71and Apint Tin 2/6 2 oz. jar 116 by the makers of ilcragira ACRA PRODUCTS LTD. ACRA HOUSE, SHEPLEY,NEAR HUDDERSFIELD

MIDLAND INSTRUMENT Co. HIGHSTONE UTILITIES CAPITAL REALISATION SALE Meters. 0-7v., 21in., m/c, 9/6 :15v., 21in., Brand New Govt. Surplus Stock. m/c, 9/6 ; 150v. 2in.. m/c., 10/-.: 300v., 2jin., IMMERSION HEATERS, for water, New, guaranteed valves :EF50, ECH35, m/i., 13/6 1 3,500v., 31in., m/c, 20/- etc., 230 v. 250 watt., fitted thermostat '6K8,. 6K7, 607, 6V6. 25A6, 25Z6, 6F6, 6,000v., 6L7. 6SN7, 6J7, KT33C, 5Z4, 5U4. MU14, 31in., m/C. 57/6: 15/600v 2in., m/c, double to cut out at 111 deg. F., 2in. dia. hole reading,8/-; 100m/a., 2in., m/c., fitting with securing flange, depth of F/W4500. 7/6 each ;HVR2, 6L6.-10/6. 7/6 New Gramophone Equipment :Collaro 40/120m/a,2in.,m/c.,doublereading, element 41 in superior job, 15,-. post 9d. 3.5 amp., sin. ; FLEXIBLE DRIVES, 4ft. long, dia. AC47 induction motors, var. speed with 8/- 1 T.C., 5/- 4 12in. turntable, £5 each. Collaro AC49. amp.,211n.T.C..in case withswitch, outer casing On.. will transmit Ih.p., 7/6: 20 amp.,21in.,m/i,9/6. 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Tuner, with large horizontal dial as- in self-contained metal case; can be used pumps, garden fountains,etc.,24v. sembly. 28/10/,Full Constructional to make up a deaf aid outfit, intercommuni- A.C./D.C.. 25', post 1/4. ACCUMULA- NEW ILLUSTRATED Manuals of above Amplifiers :No. 1. cation system, or with crystal set, complete TOR CUT-OUTS, in bakelite cases 2/6 :No. 2, 4/6.Tuners : T.R.F. or with valves, 20/-, post 1/6. Useful wooden with cover, two models, 12 or 24 v., both CHEMICAL Superhet,3/6. N.R.S. 3 -wave iron - box with partitions to hold amplifier, 2i - 60 amp., each 7/6. Post 9d. BURGLAR cored Coil Packs, a very high " Q " extra.Ditto, less valves, 10/-. One valve ALARMS, closed circuit type,will job, 21/, iron -cored I.F.'s 465 Wes, 13`6 amplifier, complete wth valve. 9/6, Post1/.. protect large or small premises with APPARATUS pair." 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TELEPHONE SETS, mains, showing " live " side of switches, consists of two combined microphones 148, PINNER ROAD, 102, PARKHILL ROAD, etc., 3/6, post 4d. and telephones. 25ft. twin connecting HARROW, MIDDLESEX LONDON, N.W.3. Soldering Irons. -Our new streamlined flex, provides perfect 2 -way communi- Iron is supplied with two interchangeable cation, self -energised, nobattery bits, one each straight and curved : 200/250 required, set complete ready for use. v.,51) watts, 9/-. Standard Iron with adjust- 7/6, post 9d. BOX KITES, dinghy able bit, 200/250 v., 60 watts, 9/6.Heavy antenna type, aluminium tube frame, Duty Iron, 150 watts, 12/6.allpost 6d. opens up to 36in. x 17in. x 17in., closed MODEL ENGINEERS Crystal Sets.Our latest Model is a real to approx. 19in. long, 2lie dia., a grand radio receiver,fitted with a permanent flier, brand new, 12/6. post 9d. SANTON FOR THE TURNER : crystal detector.Have a set in your own ROTARY SWITCHES, mains 20 amp., room. 9/6, post6d. 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New Single Earpieces, fishing rod, 2/6, post 6d, 3 for 6ffi, post 9d. 3/6.Bal. armature type, 4/6 :ex-R.A.F. Also hundreds of other interesting Pedestal Jig and Fret Saws. earpiece,2/-'p6st 4d. Headphones, in Radio,ElectronicandMechanical good order, 4/6 and 5/6 (better quality, items ;send for our new July -August 7/61. -all post 6d.Headphone Cords, 1/3 lists. 2d. with S.A.E.Orders. 30- and Perspex - Allsizes and coloursinstock. a pair,post 3d. Replacement Bands, over, up to 15 lbs. post-paid.Carriage 1/3,post4d. Wire Bands,6d.(All orders extra in all cases.Our C.O.D. Headphones listed are suitable for use service is cancelled for the time being, with our Crystal Sets.) NUTTALL'S (LATHES) LIMITED, Money refunded if not completely satisfied, MOORPOOL CIRCLE, BIRMING- 58, New Wanstead, London, E.11. HAM 17.Tel.: liarborne 1308 or 2604. MANSFIELD, NOTTS. New illustrated List sent on request with id. stamp and S.A.E. Letters only. SOMETHING DIFFERENT !YOU Radio Remote Control for Model Aircraft, Boats, Trains, etc. With no previous can become a first-class radio knowledge whatsoever, you can build your own control.Complete instructions, circuits and wiring diagrams for only 2/6.Also price list.All necessary parts in stock. RADIO ENGINEER MIDGET ENGINES -petrol, diesel and compression ignition,for model aircraft, boats, hydroplanes, etc., in stock from 45/-.Send stamp for price list. We areSpecialistsinHome- StudyCoursesinRadioEngineering, YOUR VERY GOOD RECORDS made at home to your very good liking! Servicing, Transmission, Television, Mathematics and Radio Calculations' Make your own wire or tape recorder for only Lis, or anything up to£sif you already have an amplifier.Constructional data 5/-.All parts in stock, including Postcoupon now " Crown " high fidelity recording wire and " Diamond " plastic backed -not for free booklet T. & C. RADIO COLLEGE, paper -tape. andlearnhow KING EDWARD AVE., AYLESBURY. R.A.F. MOVIE CAMERAS -1 6mm., brand new in sealed cartons. Work from you can qualify a 9v. battery, which can be carried in your pocket. Each camera complete with for well -paid one film, 47,6, post 1/6.Spare films 2- each. employmentor n Pleasesend me freedetailsof your Home -Study I profitable spare - 1 Courses in Mathematics,Radio and Television FANS -converted ex -Govt. stock, 23ov. A.C./D.C.These fans need mounting time work on a stand (wooden block) and a wire guard for the blades.If the blades are Name removed, the motor can be used during the winter months to power models. (Postcoupon in 12/6 each, post unsealed envelope Address PARK RADIO of MANOR PARK, 67618 Romford Road, London, E.12. -1d. stamp.) M.50 360 NEWNES PRACTICAL MECHANICS August, 1949 The >Wt. t kind of TYRES 'et you4-kind of a/din

SPRITE SPRITE TANDEM The ups and downs of club -work ? Reliability Effortless dual -harness work without the sacrifice of at speedcalls for atyre de. speed? Then fit the trans- signedtominimise rolling lucent -sided Dunlop Sprite, resistance andprevent side- the first choice of knowing slip - the Dunlop Sprite clubman. Cover 8.'9 Tandem. Cover 10,I6

- OR TANDEM

SPORTS TANDEM If your sport embraces everything from an ener- The tyre for more general getic evening spin to a hard tandem work. The Dunlop week -end's rniling, use the Tandem has gained a dis. Dunlop Sports. Long- tinguished name both for easy lasting and lively. riding and durability. Cover 7.4 Cover 1012 All by DUNLOP 91-F327 Valves out THE OILER THAT'S realistic DIFFERENT

Yes - it'sthe new soft FIBRAXred brake block- I specially de- /r.. signedto he 'rindtoalloy rims !Just as tough and 'Plasticine' hard-wearing as the FIBRAX Made only by HARBUTT'S black block, it gives safe stopping and smooth action at any speed. Coloured Almost any type of model red for easy identification-an ideal can faithfully be modelled in partner for alloy rims. ' PLASTICINE,' whichis so NOTE.-The new FIBRAX red, easy to handle that modifica- blockis made fora special job- tions can rapidly be made as for steel rims the black block is still the work proceeds. For the best. prototypes, " mock-ups " and other uses there is no FIT more practical medium. A n oiler that is quite different and Long-lasting, hygienicand wonderfu II y helpful. A twist of the available in 16 attractive screw at the end of the spout enables the colours. BRAKE BLOCKS .z.k4 HARBUTT'S PLASTICINE Ltd., Fibraxoiltoflow-areverse twistclosesit BATHAMPTON, BATH, SOM. 4.0a/feiaere s hermetically. No cap to lose.A choice of .4frnee Max a to, 41,the shapes and five spouts. FIBRAX LTD.,2TUDORST., Sole Distributors MARKT & Co. (London) Ltd., Of all good dealers LONDON, E.C.4 Portpool Lane,Grays InnRd., ,,V).` London, E.C.I. andironmongers Au7ust, 1949 THE CYCLIST 81

All letters should be addressed to theEditor," THE CYCLIST," eorge Newnes, Ltd., Tower House, Southampton Street,Strand, London, W.C.2. Phone : Temple Bar 4363 Telegrams : Newnes, Rand, London VOL. XVII AUGUST, 1949 No. 329 Comments of the Month By F.J. C. Sixty Years of Air Tyres sixtieth of the foundation of the industry. Theon the grounds of anticipation.Dunlop was SIR ARTHUR DU CROS was the guestprinciple was invented twice :first by Robertnot a cyclist then, and stated publicly that had of honour atthe Roadfarers' dinner'William Thompson, at the age of 23, in 1845,he known of Thompson's patent he would not at the Savoy Hotel on June 21st towhen our railways were still having theirhave taken the trouble to register his own. celebrate the diamond jubilee of the marketingteething troubles. He patented it in France inYet, while its publication was a knock -out of pneumatic tyres.Sir Arthur is the sole1846 and in America in1847,but un-blow for him and the pioneer company, it was surviving member of that famous family :fortunately or fortunately disguised his patentto the crude re -invention of this Scotsman Harvey Du Cros, Senior, and his four sons,under the names of " elastic bearings " orthat the world owes the pneumatic tyre. The Harvey, George, William and Arthur (now" hollowbeltsforwheels." The wordfounder company did a great deal to amend Sir Arthur). There 'were many distinguishedpneumatic did not occur to him. and to validate the Dunlop patent, but without guests, including Lord Courtauld Thompson, Thompson overlooked nothing.His patentsuccess.It was the Thompson tyre, but that K.B.E.C.B. (son of R. W. Thompson, thecovered all rolling bodies, and he could havedoes not lessen the debt we owe to him as the original inventor of air tyres, who patentedcontrolled everything from a railway train topioneer of air tyres. Thompson's tyre, although the pneumatic tyre principle in 1845) ;Lorda hobby horse.The original scroll of theperfect in principle, was clumsy in practice. Kenilworth, one of the early employees of theletterspatentissuedtoThompson wasIt languished and died of inanition.It re- Dunlop Rubber Co., Sir Miles Thomas,Sirpresented by Sir Arthur recently to the Citymained dormant untilits second debut in Richard Jenks (son of a former Lord ayorof Coventry, where it hangs in the publicBelfast 44 years later.It was not a new of London), Colonel J. J. Saunders, O.B.E.,library. Contrary to popular belief,Thompson'sinvention by Dunlop but a discOvery designed Mr. George L. Du. Cros (nephew), Williamtyre was marketed, and it was under constantfor a new purpose.The cycle provided the Biackwood,C.B.E.,Dr.H.A.Bulman,trial on heavy vehicles from 1845 onwards.answer. Dunlop stated that his tyre would not Douglas C: Ingram, Richard Viner, H. A.He used it on his own brougham, and in 1871be practicable for heavy vehicles.It was Wines, H. R. Cook, T. W. Knox, P. Allardyce,demonstrated it to the Emperor of Brazil inDunlop who pressed the button which started B. 0. Davis, Stanley Burchett, James A. the machine and set Wilson, Bob Carlisle ;whilst members present many minds to work includedLordBrabazonofTara,the on the problem.He president,the Marquis of Donegal], The foundthemissing Marquess Camden, Lord Waleran, Roy Du market in the bicycle, Cros (Sir Arthur's son), Major F. Bale, O.B.E., the only silent vehicle Mr. C. G. Grey, Professor A. M. Low, ontheroad,and Donald Campbell (son of the late Sir Malcolm laterintheever- Campbell), W. G. James, Jack Barclay, Harold expanding motor Lambert, L. W. Lambert, A. H. Bentley and industry. Thompson Harry Payne. and Dunlop present It was indeed a memorable evening, notable a typical case of the not only for the standing of the members and firstbeidg last and guests assembled, but also for the quality of the lastbeingfirst. the speakers. Lord Brabazon, in introducing Thompson was a loser Sir Arthur, paid a glowing tribute to the great on hisvalid inven- work of the Du Cros family in commercialising tion,while by a the idea of the pneumatic tyre, an invention margin of less than which had benefited the whole of mankind. six months Dunlop The Du Cros's displayed their genius not only made a fortune from in the world of commerce, but the sons Went his. forth into the sphere of competitive sport, and by their successes broke down the apathy William Harvey towards the new idea.There was plenty of Du Cros was 43 when opposition in those days, for the early tyres he was converted to were not the perfect examples which we use the new idea by his to -day.Some of the guests, including Bob son's successes on the Carlisle, were not only present at the birth of race track. air tyres, but had been associated with the The coming of age company ever since. It was an historic of the pneumatic tyre occasioninanotherrespect-SirArthur An historic picture.Sir Arthur Du Cros, sole survivor of the pioneer was celebrated4o Du Cros, the only survivor of the Du Cros tyre company; and Lord Courtauld Thompson. years ago by a family which pioneered the tyres, sitting next banquetto do to Lord Courtauld Thompson, now over eightyEdinburgh. Carriage users, however, did nothonour to him as founder of the industry. and son of the man who took out the firsttake kindly to pneumatic tyres and it was All pneumatic tyres all over the world have patent for air tyres in 1845 ! withdrawn from themarket,althoughifemanated from this source, and it is pleasant Lord Brabazon went on to detail the greathorses could have spoken results would haveto recallthatits advent harmed no other experience of Sir Arthur, the adversity of thebeen very different !Thompson's patent wasindustry and gave birth to vast new enter- early years, and the developments, such as thenot altogether forgotten, said Sir Arthur, for motor -car, the cycle industry and the aero-it was published in leaflet form one or twoprises. plane, all of which owe their present state ofyears before the date of Dunlop's patent in But it was Charles Kingston Welch, whose advanced development to pneumatic tyres. 1888, butitdid not come into Dutilop'swidow died almost on the eve of this diamond possessionuntilsome monthsafterthejubilee celebration, who supplied the missing The Tyre Industry flotation of his tyre in 1889. link which successfully harnessed the principle Sir Arthur, in his reply to the toast with of compressed air by a series of basic inven- which was coupled also the tyre industry,Foreign Patent Applications Rejected tions which are still in general use.It was he said that we are now, in fact, in the hundred Dunlop'sapplicationsforpatentsinwho first made, them detachable. Had he not and fourth year of the invention and theBelgium, France and America were rejected (Continued on page 82, coltorn 3.) 82 THE CYCLIST August, 1949 forthe1949 senior,junior,New Zealand to Leicestershire and ladies' championshiPs, and representatives from most of fjjR. JACK WRIGHT, well-known in the Midland clubs took part cycle -racing circles inLeicestershire The senior championship wassome 4o years -ago, is back visiting his home won by E. Thompson {Derbytown of Coalville from New Zealand, where Mercury)in3h.. 5om. overhe now lives.Mr. Wright regularly acted as 821miles,withB.Craigpacemaker for George Harry Hardy, a Coal- (Notts Olympic) second, andville cyclist, who broke many records and was J.Walsh (Woodville)third.well known for his speed on the track all The winnerofthejuniorover the country.Mr. Wright's impressions event was H. Page (Leicesterof his home town ?He thinks it has shrunk Pegasus)first,followedby-and when he saw the narrow streets, after E. Furniss(Woodville C.C.)the wide roads of New Zealand, he thought second, and C. Talbot (Trenthe had got out of the train in the wrong Olympic) third ;the winner'stown? timebeing2h. 19m. G. Clements (Wolverhampton R.C.) won --theladies' cham- COMMENTS OF THE MONTH pionship in 49m.,, followed by (Continued from previous page) J.Humphreys(Stonebridge)intervened on the side of the pioneer company and D.Welsh(Woodvilleit would have been snuffed out at birth. C.C.). Therewere closeLater, he was first to apply weftless fabric finishes in both the ladies' andto tyre linings and to introduce the non-skid the junior events, while in thecover.He was thefirst to put wire into senior event thewinner gottyres. intwominutesbeforethe sec.) d rider home. The Non -return Valve FREDERICK WOODS contributedhis excellent non -return valve in 1891 and Pedal Outboard for Boat Frederick Westwood his perfect cycle rim KENTUCKY firm,thein1893. The inventions- of these three AA,. Aquacycle Co.,' Inc., of W's 'are still in standard use and survived Covington, hasjustput onallassaults upon the patents.There was the market alighttype ofplenty of litigation in those days, and it cost =-1-7 Weekley outboardmotorforsmallthepioneer company about £550,000, so Norkampton.swire. boats which ispedal -driven.that even avalid patent ishardly a poor Pedals working a circularman's dowry. To show itsappreciation A picturu9ue small village gearcasedrivethepropellerof the unbeaten record of Welch's invention a few miles from Kell -enact throughbevelgearsandathe company in September, 5904, celebrated shaft. TheAquacycle is itsexpiration by making a bonfire of the The church is mainly Early English attached to theboatbypatent at a banquet attended by over Soo but also eoirtairts some llorman. clamps, 'inthe same way asleading members of thecycle and motor work_ . . . ordinary outboard motors, andindustries. by moving his weight in the Sir Arthur went on to trace the history saddleattachedabovethedrivingof the company from 1889 up to the present shaftthe" Aquacyclist "steersthetime, and gave many hitherto unrecorded boat.. facts of the vicissitudes through which the company passed. The company, of course, No Falling Off From Wales to Walsingham moved from Ireland to Coventry as it grew AFTER readinga newspaper reportofin strength, but chiefly because of the com- CO that the young idea can get used to a cures said to have taken place at theplaints from local residents of the smell of bicycle and have no fear of falling offShrine of Our Lady, Walsingham, 16 -year -rubber. His speech was packed with anecdotes the Huffman Manufacturing Company, ofold Robin James left his home in Abercynon,concerningallthosewhose nameshave Dayton, Ohio, have put on the market anGlamorgan,withouttellinganyoneandbecome famous in the spheres of cycling, outrigger device to be attached to the rearcycled the 25q miles to Norfolk to get amotoring and aviation.He went on to state wheel of a bicycle ridden by a child betweenbottle of water from the shrine in the hopethatthereisno memorialatpresent to the ages of 3 and 7.The attachment carriesof being able to cure his 77 -year -old grand-Charles Kingston Welch, and he suggested two light wheels, about 6ins. in diameter; andfather who was dying. No news was receivedthat it would be a graceful act if the Road- of the type used on kiddiecars, and oneat his home until the boy stopped at a cottagefarers' Club were to move the city fathers of wheelison eithersideof the rear cyclein Guyhirn, in the Isle of Elf, for a drink.Coventry to commemorate this great man by wheel. By meansofthisdeviceitis A telegram was sent to his home, white Robinan appropriate plaque upon the house in claimed that children can teach themselveswent on, without waiting for any food, inwhich he lived and worked and died.Tele- to ride in a very short time. an attempt to complete his self-imposed task,grams inappropriate terms were sent to but he had barely reached Walsingham whenDunlop's daughter, Mrs. Jean McClintock, Who Can Blame Them? his grandfather died. and to Mrs. Charles Kingston Welch. MARKET RASEN (Lincs) Urban Dis- Judged bypastachievements and the trictCouncilhave beenreceiving certainty of more to come the pneumatic complaints about the habit of local cyclistsA Little Learning ! tyre and all that flowed from it was only just riding on the footpathin Mill Road, to WHEN a 16 -year -old boy cyclist appearedone more advance in an age of tremendous the danger of pedestrians.During adis- before Oakham Juvenile Court theactivity. We preserve the records of our cussion of improvements necessary, to roadsChief Constable said the charge was broughtgreat sailors, soldiers, explorers and states- inthe town the chairman of the councilbecause of the boy's attitude to a constablemen, yet comparatively littleis recorded of said Mill Road gave any cyclist who rodewho called on him to stop.The boy went oninventors and industrialists who provide the down it an alarming few minutes.`.! There for 5o yards before stopping and then gavebenefits which are indispensable in our daily are potholes so big," he said," that theythe constable a wrong address.When thelives.Pioneers, in whatever field, are among might cause you to break your neck or legs,"constable took out hisnote -book the boythebenefactorsof their times, and their and another councillorsaidthe only safeasked if he' was on duty, as he could notachievements should rank as highly as those place for a cyclist there was on the footpath,have someone " pulling " him who was notin any other field of national service. and so everyone seemed to use the footpath.on duty, and he also asked the constable The toast of the Roadfarers' Club was The Highways Committee is to be presentedwhy he had his cycle with him.He saidproposed by Sir Miles Thomas, D.F.C., who with the problem. he would go and see the Chief Constable.drew attention to the importance of its work, The boy, who told the magistrates he thought and Professor A. M. Low replied in a witty Hinckley Road Rath!!! that when a policeman left the police stationspeech.The guests were toasted by Lord THOUSANDS of spectators were attractedhe was offduty, was said by hisschoolDonegall with responses by various guests, -to the. road -racing events held over areport to have rather a high opinion of him-including Bob Carlisle, who has been with 164 mites course at Hinckley, Leics,-on Juneself. The usual fine was increased to it,the pioneer company fromitsinception. 12.The East and North Midland Section ofand the boy's knowledge ofthe law wasThe toast of the president and chairman was the British Racing Cyclists chose Hinckleyalso increased. in the capable hands of C. G. Grey. August, 1949 THE CYCLIST 83

Speakers at the Diamond Jubilee Dinner given by the Roadfarers' Clubat the Savoy Hotel on June 21st, when Sir Arthur Du Cros was the guest of honour:r, Sir Miles Thomas proposing the toast to the club ;2, Sir Arthur C./ Du Cros ;3, Professor A. M. Low ;4, Lord Brabazon, president ;5, C. G. Grey ;6, Bob Carlisle; 7, Marquis of Donegan, ;8, Lord Kenilworth.

84 . . THE .CYCLIST August, 1949 car as an oldcyclist, for the purpose of seeing, hearing and smelling the countryside, watching the great cloud shadows sail across Wayside Thoughts the weald from the summits of the downs, By F.J. URRY and lingeringinthe comely villagesthat nestle among the hollows and are so often friends. Thefactembraced, asit were, by the gentle rivers. is,ofcourse,thatSome day I must roam this land when the onlythefolk whocorn has been harvested and allthe tinted hatetolosetheirfields run in joyous colour schemes to the activity and thattawny strand ;but in the meantime I have individual freedomassignationstofillinScotland, andthe ofmovement asso-introduction of the Wye country to some of ciatedwithcycling my young friends, and for the moment my are keen enough orcommitments are going no further.How I brave enough tolonged for a bicycle-but I daren't say so, defy the medicalindeed it would not have been kind, for the advice and prove tomemory of the old days was with us when- themselves that quiet,ever we went out,thosetimes whena sensibleriding is tandem was our mode of wandering from amongst the greatestone end ofthe- land totheother.Old healersextant. Itcyclists can getalot of quiet joy out of is naturalthatittheir holidays of yore, even if the method of should be,for heretravel has changed for them, and that is an you have gentle acquisition denied to the folk whose touring exercise, fresh air inand journeying has been confined to the car. abundanceproperlyI always feel on such occasions as this how inhaled, sunshine andfortunate I am and how grateful I should the scents of a be to the bicycle that has kept me fit and countryside added tofairly nimble right up to the three score and tomaketen and, I hope, for long beyond that measure. ne White Hart Ion., itssights life much mere ofasmilingBut how good it was to get back to the A Good Example MOR.ETOM-114J-THE.-MAR.St1 selfpitysaddle, to go roving round the home lanes Glow. progression than the welcoming the spring, making contact with T HAVE been riding a that mightsoeasilyovertake The unique hall - once the cobbled the grace of itall ; and with the knowledge bicyclemost days youiftheadvicetodesist fcr 6o years.So has coachway eatranee to the ;no yard. had beenaccepted. Iknow thatthe southern sunshine had worked a Mr. Victor Breyer, the Charles I lodged here oothe night nothing about medical matters,small miracle, for the breath of the season of July 2. 1644. was a balm to my partner, so that both of doyen of French cyc- exceptthatnomedical men lists,but thejolly old a us are happier and, each in our sphere of ofmyacquaintanceride interest, more contented. Parisian is nearly a de- bicyclewithanydegreeof cade my senior.Listen to his latest letter:-regularity ;butI doknowenoughto " With the help of the Almighty I will berealise that seven weeks' absence from the The Old Trail 8o years old next September, and hope tosaddle last year brought home to me, as pedal as long as I live, having never foundnothing elie could, the kindly health value HUMAN nature is very frail; even after a more exhilarating,healthful and joyous say nothing the experience of three score years and I obtain from the pastime, to ten. exercise than cycle touring. Many years ago,of the pleasure of whichIshall never .be I should know better, but preferring to as with most young people,I went in forable to tell enough.I do think some doctorsbe optimistic than otherwise I half expected amateur racing and thoroughly enjoyedit;are inclined to look upon cycling as the lastthe Easter weather to preface a summer of but nowadays scorching is, of course, out ofresort of the impecunious andtotreat itglorious sunshine and warm showers, and the question.On give and take roads myaccordingly.Because I am an enthusiast mythe nip that followed those delightful days average speed per- hour is 15 to 16 kilometresrecommendations inthis matter are givengave the '" old miseries " the satisfaction of (rather under ten miles an hour), and I can warily ;I know it is good for me, and so Isaying, " I told you so; sure to have to pay always run up too kilos (63 miles) in a day-thinkitmust beequally goodfor otherfor it," and so made thein happy in retro- without undue exertion; and atthat takepeople, always providing they will use the spect.I believe in taking the good things as things leisurely, two hours for lunch with a pastimewithdiscretion,gearmoderately,they fall and finding in the enjoyment of quiet drink before eating, and a stroll roundpedal correctly and sit comfortably.Itis them any needed solace for the things to the place when there is anything worthy tonot always easy to act counter to a doctor'scome, which may not be a wise way to live, visit. Nothing finerexists,Isay again."advice ;thereare the family folk to con-but itis at least a happy one.I went into Do you believe it ?I do, and my hopesider besides your own desire to remain anthe Cotswold country with an old friend, a is that when and if another decade has goneinhabitant of this earth as long as possible ;man connected with the trade, and after a over my head, I can still do these things andbut I do seriously believe that much suchlapse of nearly a' decade found that area as revel in them. It is a refreshing thing to readadviceisgiven without knowledge of thedelightful as ever.I warned my companion such a testimony to cycling from an indivi-excellence of cycling, and the very delightthat my passage would be annotated as it were dual who has practised it for sixty years, forof the freedom on the mental condition ofwith frequent stops to stand and stare, and, if it gives me the desire to run on along time apatientunderthehandicapofhealththe weather was favourable, many a road -side untilIhave completedseventyyearsofrecovery. lounge to better hear the birds sing and see cycling, and then IexpectIshall not be " cherry hung with snow."Further Isaid satisfied.Most of the people with whom IGoing Without I would introduce him to the drumming -up am in touch in the cycling sense are of theT RECENTLY went along on a recuper-method of lunch and tea if he would carry later generation, and therefore have to dis- ative1-holiday without a biCycle, one ofhis portion of the necessities; he agreed before cover still the delight of cycling when speedthe few times in my life when I have been sohe saw the necessities, created at an addi- and distance have become matters of second-circumstanced.Illness at home and the hopetional burden of under four pounds, made aryconsideration,whentheindividualof. a recovery made the journey necessary, freedom of the game has developed into a a horrible job of packing, but at the end of and indeed desirable, even from my point ofthe adventure became enthusiastic. The pricelessacquisition. Yet the promise of view,fortheprocessofwitnessingthe that development is within the compass ofreturn to reasonable fitness of an affectionatemeals were better, you had them where and every one -of you, and if you care for it andcompanion for 44 years is a joy beyond thewhen you desired; a Primus can cook things, cherish it you will, not grow older than yourtelling. We were notwithouttraveland the delight of this nomadic sense of free, years, but mellow into a wanderer seekingfacilities, for the powers that be recogniseddom made you forgetthe fewadditional beauty by the wayside and carrying some ofthe need for the journey and granted thepounds of baggage.Besides itis so much it home with you to comfort rest and makenecessary fuel, so I have seen a little morecheackr; suchwerehisreactions,andI memory a very charming background to life.of._ the South Downs when the spring madeconcur.After one trial under instruction he thema perfectpictureofthepeaceful Do Doctors Know ? managed to pack the appurtenances without English scene. And how beautiful they are!rattle and in the minimum of space, and the NOW enlightening it is to read of fellowsNo wonder the poets who live and have lived who, in the face of illness, have onunder their shelter sang their praises, andminimum oftime,soourlittlejourney recovery and against doctor's advice, taken tothe books on Sussex teem on the theme ofstarted propitiously after the first arguments cycling, and found a sense of fitness and well-their loveliness.Because my companion washad been composed and order restored to a being which has astonished them and theiran old cyclist she was content touse therather agitated mind. August, 1949 THE CYCLIST 85 APEX The World Famous 'SUPERLITE' BAILEY'S CELLULOID PUMP `SUPER 15 x i" BLACK PUMP 15 xrBLACK Thick Celluloid Steel Lined Celluloid Covered Beautifully Polished Lining is Solid trawn cartridge fashion,the ends Light of Weight but of being solid with the barrel. robust construction Cannot warp nor leak ' SUPERLITE' I5in. 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THE" FLUXITE QUtNS" of a special friction material that is practically AT WORK unaffected by weather and can be relied on I'm makingalampshade," to give you safe, positive control for long said 00, Come on and help me, you two, hills or emergency stops. Holdthatwireniceand tight ,The price of standard sizes is now While I get our FLUXITE Don't let go whatever you do." D. A PAI R For all SOLDERING work -you need FLUXITE-the paste flux -with whicheven dirtymetals are soldered and "tinned." For the jointing of lead-without solder ; and the " running " of white metal bearings-without " tinning " the bearing.It is suitable for ALL METALS-excepting ALUMINIUM-and can be used HUB BRAKES.Ferodo Linings are with safety on ELECTRICAL and other sensitive apparatus. supplied in boxed sets, complete with With Fla.rite joints ean be7"wiped" sueeessfally that are impossible rivets, for all makes of hub brake. The by any other method size is exact, and the friction character- Used for over 40 years in Government works and by leading istics correct, for each type. Also avail- engineers and manufacturers.Of all Ironmongers-in tins, able in roll form. 10d., 1/6 and 3/-. AghT0 CYCLISTS! For stronger wheels that Wwill remain round and true, here's a time - tested tip.Tie the spokes where they cross with fine wire AND SOLDER.It's simple- with FLUXITE-but IMPORTANT. FERODO THE"FLUX ALL MECHANICS WILL HAVE\ GUN puts-FLUX- ITE where you ALL WEATHER BRAKE BLOCKS want it by a simple pressure. AND LININGS FOR HUB BRAKES Price 2/6 or filled FLUXITE 3/6 ITSIMPLIFIES ALL SOLDERING REG D TRADE Maki( FERODO LIMITED, CHAPEL -EN -LE -FRITH WritelorRook onhe ART OF SOFT SOLDERING and forLeaflets an CASE -HARDENING STEEL andTEMPERINGTOOLS withFLUXITE. A memberof the Turner & Newall Organizationri ALo WIPED JOINTS.' Price Id. Each. FLUXITE LTD., Dept.P.M., Bermondsey Street, S.E.I 86 THE CYCLIST August, 1949

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And another member ofthe thenest example of 14"'cent, work. party, "just back from a tour in Shropshire in the count[{. . . and Herefordshire, stood up valiantly for the matchless beauty of those shires.But Devon carried the day .. . and there was much talk of Lynmouth and Lynton, and Clovelly, and of all the romance of Drake's land, and the glamour of Plymouth Hoe.As I rode away from the inn, in the purpling dusk, I thought of other shires, and fell to musing upon tours Ihad made, in- thelongago,inquiet, homely Suffink, where the spirit of Constable broods- upon the meadows, and his genius seems to haunt the streams and lanes... Welcome Return HOW good it is, after so much indifference (and even discourtesy) during the war years, tosee a return tocivility and good manners in our shops!In asmall cycle dealer's shop the other week,I was plea- santly struck by the courteous manner in which customers were served and attended to.One man required only a pair of trouser clips, but his need was met with a smile.I have always felt that efficient shop -keeping rested on courtesy ... and it is good indeed toseethisreturntoformer modes and Call of the Sea oneknowseveryoneelse,and" parishmanners.Life can be drab enough without EVERY year one reads complaints aboutpump " politics assume an enormous signifi-theaddedandunnecessaryburdenof the concentration of holidayOnto thecance. And I have found, asI knew Iimpoliteness in our -shops:, month of August.And every yearitisshould, that the bicytle in the country is no patiently pointed out that as Augttst is theluiury, but asheer necessity ! Impossible ThisisOur Heritage school holiday month,itisinevitable thatto contemplate lifeina village without a EVEN in this age of scientific planning, most families will select the month for theirbike, and I 'am glati that I as keen a the- vandal isstill with us, and itis annual trip to the seaside.It is an awkward,rider as ever, forIlook forward to manystill possible to see areas of England which, business, but nobody has yet succeeded inhappy rides around that good country"-alongare being needlessly spoiled.Our heritage solving the problem, and I am afraid that theDerbyshire -Staffordshireborders,withof scenic beauty is something more than a Foamville-on-Sea will continue to receive itsUttoxeter and Derby as centres for my runs.romantic thing:.itis one of our best com- hordesof holiday-makersinAugust, andRetirement from the hurly-burly of Londonmercial assets. We read much of the " Come beacheswillbecrowded,andboarding-,Town has its compensations, I find! toBritain " movement, and ofthe efforts houses full.But for the happy cyclist, who to attracttourists to our shores.But we can slip away when he will, August, is per-Those Old Catalogues must remember that they come, largely, to haps as good a month as any.True, some MY recent references to am old " Mead "see our panorama of scenic grandeur; they ofthefreshnesshasdepartedfromthe cyclecataloguewhich -I'unearthedwant to see rolling fields, and little farm- countryside, and the green of June gives wayhave brought me one or two letters fromsteads, and noble trees in ancient parklands, tothe dusty -brown of later summer; butcycling men who evidently share my ownand stately homes ... and all that makes the it is summer still, and it is good to ride downlove for old papers and documents and price -essential English scene.Let the vandal des- to the coast, and find some spot where the listsand thelike.,One referstoan oldtroy these gems, and the lure to see England waves lap lazily against the rocks; and theDunlop leafletpublished "about 1898,is no more . . . and we lose a most valuable seagulls cry overhead, and the little fishingwherein the virtues of the pneumatic princi-source of revenue.Every cyclist who loves boats set out, manned by tawny -faced oldplearedescribed in quaint language, andbeauty,andhasmemoriesofthereal men who know the ways of wind and tides,where the address of the Company is given asEngland, should support the excellent work and whose eyes are clear with long gazing outAlma Street, Coventry.This is going backof those bodies which battle for the preserva- to sea. . . indeed! But ofallour great companiestion of our. heritage. This year, I plan to ride down into Dorset,and industrialenterprises, - Isuppose that where there are coastal villages which havenone has a , more romantic history than the remained unspoiled-where " development "Dunlop Company . . . and few folkin is unknown, and where, in some little, inn1898 could have foreseen the gigantic develop- Workshop Calculations rejoicinginsomesuch nameas" Thement of the concern, or visualised its present- Lobster Pot," one may drink good ale, andday ramifications.Among great inventions Tables and Formula chat with men of the sea, and forget for awhich have revolutionised human habits the Ninth Edition time the frets and fumes of the city.Saluteinvention of. the pneumatic tyre must always byF. J. CAMM to August, and the restless sea l have an honoured place. A handbook dealing with methods of calcu- The Indispensable Bike The BestCounty? lation, solution to workshop problems, and the rules and formulae necessary in various SINCE my retirement from the Dunlop IHAVE lost count of the number of times workshop processes.It contains all the Service my plans for residence in the I have listened to discussions about the information a mechanic normally requires. heart of .my beloved Derbyshire have beenvaried virtues of the counties of England. In Fromallbooksellers,6/-net, progressing, andIhave recentlyspenta little old-fashioned inns, in tea-shops in re- by post 6/6 from the publisher, couple of happy weeks not far from ancientmote villages, and at club meetings I have GEORGE NEWNES, LTD. Ashbourne, almost under the shadow of theheard riders extolling the beauties of Sussex, (Book Dept.), Peak. . . preparing for the days '"When and Devon,- and Warwickshire,; and Kent,, Tower House, Southampton, Street, shall be a villager, caught up in all the variedand Westmorland . . . and I have smiled at W.C.z. activities of a little community where every-times at the passion with which this question 88 FHE CYCLIST August, 1949 roads on a large scale. ham istrue, in varying degrees, of many Thus ifwecyclists other populous 'places. My Point ofView shouldeverseeka motto, it might wellThe Borrowed Bicycle "WAYFARER " be " Ubique," mean- ing " Everywhere." THAVE always maintained that borrowed These thoughts are or hired bicycles do not, as a rule, give prompted by a chanceone cycling fever. Probably they don't fit, meeting with an oldand it may be too much trouble to carry friend last Good Fri- outsuchadjustmentsaswill makethe day. He is a brother-mount more suitable to one's purpose. And, Anfielder whom I firstin the case of the borrowed bicycle, it would encountered in my be only right to make he necessary readjust- Birkenhead days overments, so that, in returning the machine, it 25 years ago.After- isinthesarele, conditionas when taken away.- Recently, however,Iborrowed a wards hetrekked inbicycle which might very well have brought 411111 search of bread andon cycling fever, had I not already possessed butter to Scotland and it.I was away from home, and, confronted then to Yorkshire, with the need for making a few calls in out- and now he livesin let.- he -way places, I looked round for some Essex. Well, I was very busy sunning way of avoiding the cost of hiring a car.A myself, sitting on thefriend to whom I spoke willingly agreed to lend me herbicycle. For one horrid gardenwallofthe moment Ithought little Herefordshire itwould bealady's inn where I was stay-model, but it was not. It was a qu'ality thisstill male bicycle wi h fret -wheel and a rather ing,when steeply dropped handlebar. The" saddle was young man (one of thenot quite my choice, but then I can ride any last of the fixed-creirsort of saddle without discomfort. brigade)rolled along So off I A. glimpse of King's Chapel from the lovely Clare Eridge . the road and gentlywent, and thoroughly enjoyed the experience, dating from 1640. doing my business quickly with a minimum drifted to a standstill.of expense, whereat I was gratified.I must Objectless He looked up at theconfess that I do not like cycling in long TT must be admitted that while I haveinn .signand thenatme, and we bothtrousers, but be:ter-that than not cycle at all! Ialways hadalikingfortheprocess said: " Well! Dash me! "-or words to that known as" messing aboutinbOats,"I effect. He sought lunch and I saw to itFlaw deplore the same process in its applicationthat he did not seek in vain.When did we last meet ? Just a year ago, according OUR- -Parliamentarydraughtsmen have a to bicycles.Please do not mistake my mean- great deal to answer for, and it is to be ing.What I condemn is the aimless activity totheChurch'scalendar. On the day - before Good Friday, 1948,I- was makingpresumedthattheyarethebestfriends ofadolescents who, veryoftenpossessed possessed by members of the legal profession. of attractive new bicycles, seem to be con-mywaytowardsChirbury,alongthe tent with a cycling programme which canWolverhampton-Bridgnorthroad,when I Take the case of that motorist who was " par- was overtaken by my friend (an easy enoughdoned " for a sin he did not commit.He best be described as " twice round the block had been fined £2 for driving a motor -van and home."To my mindthissortofjob toovertakemenowadays!),who thoughtherecognisedfromadistance with negligence, his offence being that, when cycling programme isa prostitution of a stationary, he had opened the door of the magnificentpastimewhichoffersinfinite"those shoulders." And three or four years delights and advantagesto anybody whobeforethat we met again by chance onvehicle and a boy cyclist ran into it. The will use the bicycle properly, and I mustthe Ludlow -Leominster road, when, underLord Chief Justice- has held, on appeal in a the protection of his wife, he mildly remon-similar case that,asthe vehicle was ata say that the sight of young people " messing standstill, the man could not be held toz be about onbicycles "-content witharunstrated with me for" dancing "(asitis round the houses, followed by' indulgencewrongly called) on the pedals in the negotia- driving it.Of course, it was never the inten- in a few more or less" clever " tricks-tion of a little hill. tion of Parliament that thoughtless motorists peeves me.What waste of time ; what loss should " get away with it " in this manner- Discovery andthecarelessdraughtsmanachieves ofopportunity-when justbeyond the another victory. -On a strict reading of the corner is to be found the Romance of theTHE other Clay I read an advertisementAct, the Lord Chief Justice was right, and Open Road ...the joy of the lanes. . . issued by the London Transport Execu-there can be no manner of doubt that Acts the sublime beauty of the countryside. . . tive which ended as follows: " You will find and the constant possibility of adventure.that the country is nearer than you think."of Parliament (and Orders in Council, for Adventure ?Yes! all sorts of little adven-That is a thought which all cyclists mightthe mater of that), must be so read ; and I, turesbefallthe cyclist-provided he doesfitly bear in mind: the country is nearerfor one, cannot quarrel with the decision to to " twice round pardon a person who has not committed any not confine his activities than you think, and how much nearer it is,offence in law.But the law must be altered the block and home." and how quickly it can be reached, if we useas quickly as possible, for the protection of our bicycles sanely. cyclists against those social pests who fling Ubique On the evening -before I saw this advertise-open their car doors without the slightest WE cyclistsdo getabout, don't we ?ment, I had a cha: with a friendly bus driver,regard for other road -users. Visitors' books kept by the cottages,who professed to be astonished becauseI farms and little inns at which we put upwasnot,asusual,ridingabicycle. He From the cycling point of view, I suppose are an interesting study, fortherein, as asaid that he had just had a run' into the thatthe most famous example of faulty general rule, we shall find familiar names. country, taking advantage of the opportunitydraughtsmanship is con-ained in an Act of " Old Bill " was staying atthis place lastwhich split duty gave him, and he had thor-Parliament which I thinkis no longer in week,washe ? And" Dusty's "nameoughlyenjoyedhimself,potteringaboutoperation.It said that the cyclist must give recurs so often in another book that onesome of the lovely spots within very easywarning of his aoroach, in named circum- imagines him never to spend any time atreach of the city. He asked; " But how stances," by bell,whistle,or otherwise." home.Here are the names of a familiarmany people knew about them ? " and theIt was never intended, of course, that the married couple and their two boys (the latterquestion was pertinent.Yes ; what percen-cyclists could do the needful by word of having now reached the Stage when theytage of the million -odd folks who dwell inmou h, but the law is-or, rather, was- ride their own -singles and are no longerthe city where I live know that within suchquire clear. There was no compulsion to carted about by the parents), while anotherready access is a great mass of loveliness,carry a bell:there was compulsion to let page carries the names of an enthusiasticwith delightful lanes, glorious long-distancepeople know you were coming.If you did band of club stalwarts who, at Bank Holidayviews, and a ring of shapely hills to inspirethis in a way included in the category of week -ends,indulgeinanironing -outof the passer-by ? What is true of Birming-"otherwise," you were safe!

Published about the 30th of each month by GEORGE NEWNES. LIMITED, Tower House. Southampton Street, Strand. London, W.C.2, and Printed in England by W. Spealght & Sons. Ltd.. Exmoor Street, London. W.10.Sole Agents for Australia and "Practical Mechanics " Advice B COUPON New Zealand-Gordon & Gotch (A.,sia), Ltd. Sole Agents for South Africa-Central News Agency. Ltd.Subscription Rate This coupon la available until Aug. glst, 19-19, (including postage): For one year, Inland and Abroad, 10s. 6d. (Canada 10s.Registered at the G.P.O. for transinission by and Must be attached to all letters containing Canadian Magazine Post. CONDITYONS OF SALE AND SUPPLY :This periodical is sold subject to tto, following conditions, namely, that it shall queries, together with3 penny stamps. A not, wit' -nut the written consent of the publishers first given. be lent, re -sold, hired out or otherwise disposed of by way of. etatoped,addressed enrelope must also be en-lowl. 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Data Sheet, 3/-, post free. with laminations and wire, 500 watt size, realvalue. 1716. stones, paint, print, inanu- MaITIN/I Mans Noinstru- MANY OTHER TESTED AND WIRE.D.C.C. magnet wire,19 gauge, scripts, biologicaland botanical ment you can GUARANTEED DESIGNS 416 lb., 36 gauge 216 lb. specimens, cutting edges, fractured buy will more AVAILABLE MOTOR PUMP, 400-v. 3 ph.A.G., surfaces, raw materials, powders, granules, quickly justify Send 21d. stamp for Latest List, or see motor fitted submersible pump, 600 g.p.h., and innumerable other purposes, the ULTRA and pay for itself. previous issues of P.M. £5.12 volt D.C. for Caravan or boat lift. LENS is invaluable, and presents in many Instances Fullparticulars 3ft. throw, 10ft. handle, 100 g.p.h., 141151, hitherto unsuspected data which can be used to advantage. on request. WINTER EVENINGS PRICE 14 I5s. Od., complete in casewith spare bulb, TELEPHONES. House and office.Con- battery and transparent Now is the time to start on that Radio- structors'partsforyour own set up. measuring scale. gram you have promised yourself, so Ex-G.P.O.walltype comprisingbracket that you will obtain perfect enjoyment mike transformer and condenser, magneto Tull; ULTRA LENS COMPANY, ofyourfavourite broadcastsand 75, Finsbury Court, Finsbury Pavement, London, E.C.2. records.If you want the best, without bell, in walnut case 8in. x 6in. x 3)in., fitted paying dearly for it, you should con- terminalsandconnectionsswitchhook sider my " CRITERION " RADIO- and contacts, hand magneto generators and GRAM.This design Is for Quality single receivers, 251- per pair, with wiring Reproduction of radio and records, the diagram;carriage and packing 51-extra. circuit incorporating 2 T.R.F. stages : GREAT SUMMER OFFER Infinite Impedance Detector DIMMER RESISTANCES. Totally High Sets 0. clear Diagrams and Instructions and Low Note Tone -correcting Stage enclosed,panel type,100 ohms, 1 amp. for making easily from readily obtain- (withConstantOutput): Voltage or 50 ohms, 1 amp., 216 each,post 6d. Amplifier :Phase Splitter and Two Open type, wire wound, porcelainbase, able materials only. Triodes in Posh -pullin the Output Stage, giving 8 watts :Negative Feed- 10 ohms, I amp., 216. 1. Toy and Model Makers' Lathe 3/6 back ;Medium- and Long -wavesA.C. RELAYS, ex-G.P.O. stock,100 -ohm coil, 2. Toy and Table Model Fret Jig only :3 Large Sheets of Full-size Plans, operate from2.!volts, ISm.a. bank of Saw Machine .. 3/6 plusfulldescriptive matter and all component values, 7/6. 20 relays, in case, 151-.G.P.O. type 3,000, 3.Ball Belying Circular Saw.. 3/6 as new, 150 ohms, 2 m. I C.O. contact, 5. TableModelTorchBattery BEGINNERS HAVE ACTUALLY MADE 416. P.O. relay in circular case, 30 ohms, Operated Cigarette Lighter and THIS DESIGN WITH COMPLETE 500 ohms, 1,000 ohms, etc., 216 each. 6 Lengths of Element Wire .. 3/6 SATISFACTION G.P.O. Table type magneto ring telephone 6. Tubular Furniture (all kinds) 2/6 with hand com. Telephone on rest, mag. EASILY MADE FROM OUR CASTINGS PROMPT COMPONENT SERVICE bell generator, with wiring diagram, 401-, Any TWO for 3/6 only. Post to -day to : carriage 51-. J. HALLAM & SON What they say: "YOU ARE SURE MORSE KEYS. Precision made ex-W.D. UPTON, POOLE, DORSET, OF A SQUARE DEAL FROM on bakelite base with heavy insulated knob, P. M. BARHAM SPARKS" Practice buzzer 21-. BRIDGE AVENUE, MINIATURE PETROL ENGINES for 116, post 6d. Aeroplanes, Boats and Race Cars. THE DEM. CONTINUITY TESTER, ST. SAMPSONS, GUERNSEY, C.1. self-contained Govt. model, 6) x 31 x 2), tend 6d. for New I ist L. ORMOND SPARKS (M) for circuits,totally BOOKS: useful allelectrical Railway Modellers Handbook 9, PhoebethRoad,Brockley. enclosedinpolished wood box carrying 2/6 ADANA PRINTING MACHINES S.F.4. L.M.R. & Se.R. Shed Nos.... 2/ . (Nearest Station : strap and contact switch, 816 with battery. Print in the odd hours with an Ladywell S.R.) Civil Engineering Work " 4/6 Adana -still the most absorbing (Phone: Lee Green 0220) LIGHTING AND CHARGING SETS. " Min. Loco. Construction "... 8/6 Sample L.M.S. or G.W.E. Train Postcard of crafts. No.1 11/S Villiers 550 watt sets 2 h.p., single cylinder, & List 7d. Machine £4.10.0. air cooled,verticalpetrol engine direct No. 2 1LS Machine coupled to 18 -volt, 20.5 amp. D.C. Crypto USEFUL PARTS 000 £9.15.0. Will Scale Bakelite Wagons - 10/6 quickly pay foritself. generator, speed 2,000 r.p.m., with petrol Scale Bakelite Vans... tank and guardrails,£171101-. 3 -circuit - 12/6 Sead for illustrated FOR PRINTING Green Grass Paper, 22in.xllin, 1/- 1/6 folder to Dept. P.M. 25. charging switchboard for above plant,in Scale Station Figures...... 6d. 71d. pressed steel cabinetfitted variable Pea Bulbs on Base 2.5 v. ... 6d.6d. Adana (PrintingMachines),Ltd. LETTER chargingresistances,Fieldregulatorfor 20-v. Lamps for Hornby - 1/21 6/18. Church St.. Twickenham, 1111dx. 5 SW. Block 20 Amp. ... 2/62/6 dynamo, 3 circuitammeters andmain Model Shrubs ... 6.L6i1.. HEADINGS, current ammeter, voltmeter,3 enclosed cut-outs,terminals and 3 -polecoupling Postage extra." 00 " or " 0 " Parts Lis RATCHET & REVOLUTION BILL HEADS, Immediate delivery. 3t1. per post. plug, £6.All as new. TYLDESLEY & HOLBROOK (M.E.T.A. HEADPHONES. SingleL.R.phones 109. DEANSGATE, MANCHESTER, 3 COUNTERS FOLDERS, with headband andcord, 116, post6d. Askfor Double headphones for crystal reception, Leaflet No. 18/6 LEAFLETS, 51-, 9d. postage. SAILOR SAM'S SECRET How to Make Speed up to WIRELESS CONTROL UNITS, ex- SHIPS IN BOTTLES 6,000 r.p.m. CARDS,Etc. R.A.F., contain Yaxley switch and knob, H.& F. CARTER THE connectionstrips,fuseandholder,coil Kits, 5/6 and 6/ - & CO., Ltd., Bolton 5 socket and connections,21-, postage 9d. Flying Fish Solid Gliders The Super Kit, 4/3 FORREST PRINTING WORKS, Larger model with 2 Yaxley switches and Stocked byModel,Sports and ToyStores WEBLEV AM PISTOLS pilot lamp, 31-, plus 11- postage. Please write for details Marvellously 240, Holloway Rd., London, N.7 PRESSURE GAUGES. Bourdon Boost COOPER - CRAFT, LTD. accuratefor Opposite Tube Station NOR 2004 Gauges plus 8 minus 7 lbs., luminous scale, The BRIDEWELL, NORWICH targetceoracs bakelite case, new and boxed, 51-. DYNAMOS. C.A.V. 12 volt 10amp. No licence required to 60011,000 r.p.m.totallyenclosed,shaft purchase. REYNOLDS RADIO. - Mall order extensionatboth endsforprop.for EARN MONEY SeniorMark I specialistsforallspares,testgear, carriage51-. Leese making Scale Models at television, and gram equipment. Send windmill work, 401-, home. We JuniorWebley Air Rifle for lists.All brand new equipment by Neville 30 -volt5 -amp. shuntdynamos, supplyPlans,Instructions,andbuy reputable makers at the right price. 1,500 r.p.m., 35l-, carriage 51, yourwork. Details free. Write Write for List. WEBLEY & SCOTT LTD., Latest Plessey mixer -changer,218 ; VARIABLE RESISTANCES, slider type, Box C19, 06. WeamanStreet.Birmingham. Eng. Amplifiers 4 watt, £6 ;10 watt, £1.1 ; 25 watt. 226/5/0.B.V.A. and surplus 3 ohms 10 amps. 1216, 6 ohms 6 amps. 151-, *Multicratt CATALIN Material* valves of all types, pickups, motors, 1.2 ohms 15 amps. 716.Rotary resistances, BILTEX MODELS etc. -H. C. REYNOLDS, 21, Sleuth comprising resistance mats and radial stud CHISWICK, LONDON, W.4 Rods,Cylinders,Sheets,Sections, Street, London, N.W.3. switch and contact arm, 10 ohms 18 amps., Kits for Book -ends, Table lamps. etc. 2216 carriage 216. The most versatile of all materials. Beautifulcolours,easilyworked. TERMINAL BOXES. - Bakelite power MYFORD LATHES AND Sample Box 10/-. Parcels 25/- & 50/-. terminal boxes 3/in. x 21in. x 22in. highly TRANSFORMERS ACCESSORIES (Ex -Stock) Details, Stock List, Sample 6d. polished black with tin. ML.7 Model, 31in. x 20in. Bench Model, Thompson Transformersofvarious Dept. PM, COULDEN & SMITH, outputstosuit your requirements. centre fillet and screwed £421519, or with two fitted chucks and Special Sizes for Trains and Motors. cover 2 -pole 51I6in. con- motor, £59/19/6: ML.8 Model Wood or 17. The Mead,' West Wickham, Plastic,Sin. Swing x 30in.,£18/15/6 Kent. 12 v. or 20 v. 11 amps...... 21/- nection studs and nuts. " Super Adept " 1-5/8in. Lathes, £41101- : 12 v. or 20 v. 21 amps. ... 26/- Admirableterminalor " Flexispeed"Ditto.27/5/- 2Iin. 6 V. 7 amp. Ground Heater ,..25/- branch top on large Chucks, 32/- :"Adept" Hand Shapers, The "THAMES VALLEY" Step-up or Down 60 watts ...21/- transformer, 2 -pole £71101-: "Biumerd" and "Crown" Rectifiers from 13/6. lights, power or charging Chucks.All Model Engineers' Tools. Stamp for List and quotation. L. TERRY. FISHERS LANE, COLD BATTERY CHARGER T. W. THOMPSON & CO.. 176, Green- circuits 10150 amps.Wall or ceiling fixing, ASH, NEWBURY. HERmitaae 254. 116 each, 151- per dozen. 2 - 6 - 12 VOLTSI AMP. wich High Road, Greenwich, S.E.10. PARCELS. 10Ib. useful oddments for the with AMMETER junkbox. Allclean,dismantledfrom for 200-250 volts 50 cycle mains Weatherproof, Aluminiiim, Two Blade Government and other surplus apparatus, BOMB -SIGHT SIGHTING 42/6 post tree 716 post free. (Not for Overseas buyers.) HEADSin original steel cases. WIND CHARGER PROPELLERS Thames Valley Products Please include postage For mail orders Length, 4ft.to ins. Weight, 23 Weight 4o lbs.15/- carr. paid. 28 Camden Avenue, Feltham, Middx. ounces. Price 20/- each, including ELECTRADIX RADIOS FOR SALE full set of constructional details for BROWN making Turntable Mast -headand 214 Queenstown Road, Battersea, Cycle. Gents Raleigh Sports. 3 -Speed. Gear case.Dynamo Lighting from Front other parts. Careful packing and London, S.W.B 102, CLEVELAND STREET Hub. Cable Brakes. Special Saddle. Used postage, prompt dispatch. No duty, Telephone: MACoulay 2159 DONCASTER few times :as new. Cost £20, price £15. - nor P.T. to pay. Peerless,58,Gloucester Place,W.1. P. Robed, 64 Hauteville, Guernsey, C.1. WELbeck 1228. One of the following Courses taken at home in your " PRACTICAL ENGINEERING " said- spare time can definitely be the means of securing We recommend all readers interested in improving their position substantial promotion in your present calling, or entryto apply, for a copy of thisvaluable book. " Successin into a more congenial career with better prospects. Engineering"isnot a pamphlet. It is c .132 -page book, containing valuable and vital information on all branches of ENGINEERING, AERO, ETC. engineering.... There are many engaged in engineering who Plastic-Radio-Aero Engines-Aircraft Design -owe their success to The National Institute of Engineering. Welding-Aerodynamics-Electrical Engineering-The FREE GUIDE explains Television-Electric Wiring-D i e s e IEngineering Openings, prospects, salaries, etc., in Draughts- -Generation and Supply-Works Management- manship, Inspection, and opporttinities in all other Metallurgy-Refrigeration-Planning. Estimating. branches of Engineering and Building. Rate-fixing-Time and Motion Study-Aero Inspec- (!)How to obtain money -making technical qualifications tion-Automobile Engineering-Sheet-metal Work- through special RAPID FULLY -GUARANTEED Engineering Draughtsmanship-Aero Draughtsman- COURSES. ship-Jig and Tool Draughtsmanship-Press Tool and Die Draughtsmanship-Structural or RIF ConcreteWrite now for your Draughtsmanship-Sanitary Engineering. copy of thisremarkable publication. GENERAL Matriculation-CollegeofPreceptors-A.C.C.S.-A.M.I.E.E., A.C.I.S.-AircraftApprentice. A.IVI.BrILI.R.E., A.M.I.P.E., A.M.I.C.E., MUNICIPAL SERVICE A.M.I.Mun.E. M.R.San.I., A.F.R.Ae.S., School Attendance Officer-Handicraft Teacher- London B.Sc., Degrees. Registrar-Housing Manager-Sanitary Inspector- Fully guaranteed postal courses for Weights and Measures Inspector-Inst.of Mun. alltheaboveandmanyother Engineers-A.R.I.C.S.-L.A.B.S.S. examinations. Fullydescribedin the Free Guide.

THE BUILDING BOOM- THE ACID TEST OF TUTORIAL EFFICIENCY SECURE YOUR SHARE I SUCCESS --OR NO FEE The Free Guide also gives particulars of our extensive range of modern Building and Structural Courses, Building Draughtsmanship, etc.The great post-war Building programme offers un- We definitely guarantee that if you fail to pass the examination for limited prospects to technically trained men. which you are preparing under our guidance, or if you are not satisfied in every way with our tutorial service-then your Tuition BECOME A DRAUGHTSMAN Fee will be returned in full and without question. This is surely QUALIFY AT HOME the acid test of tutorial efficiency. AND EARN BIG MONEY If you have ambition you must investigate the Tutorial Men and Youths urgently wanted for well paid and Employment services we are able to offer. Founded positions as Draughtsmen, Inspectors, etc.,in in 1885, our success record is unapproachable. Aero, Jig and Tool, Press Tool, Electrical, Mechanical and other Branches of Engineering. Why not fill in and post the attached Coupon NOW for further Practical experienceisunnecessaryforthose details and Free Authoritative Guide to openings in Engineering who arewillingto learn-our Guaranteed and Building ? "Home Study" courses This book contains a mine of valuable and exclusive will get you in.Those information and may well prove to be the turning point in your alreadyengagedinthe career. GeneralDrawing Office should study some PROMPT TUTORIAL SERVICE GUARANTEED specialisedBranch such as Jig and Tool 'or Press Tool Work and so con- FREE COUPON I siderablyincreasetheir scope and earning capacity. To NATIONAL INSTITUTE OF ENGINEERING es (Dept. 29), 148, Holborn, London, E.C.1. Please Forward your Free Guide to NATIONAL INSTITUTE OF ENGINEERING NAME ADDRESS 148,HOLBORIDNelp,t.L 2.90NDON,E.C.1 My general interest is in : (i) ENGINEERING (Placea cross against (2) AERO(3) RADIO(4) BUILDING theou OVER SIXTY YEARS OF (5) MUNICIPAL WORK arebrancie.snttenrewstherdcb) CONTINUOUS SUCCESS The subject or examination in which I am especially interested is

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