A PORTABLE ENLARGINGCABIN

EDITOR F.J.CA1v1A4 APRIL 1948

USING A " DESIGNOGRAPH." FOR CONSTRUCTIONALDETAILS SEE PAGE 227.

PR/NC/PAL CONTENTS

A Practial Watch -repairing Bench A Handy Radiator World of Models Elements of Mechanics Making a Telescope Reflector Trade Notes Schoolboys' Own Exhibition Studies in Electricity and Magnetism Cyclist Section it naW'memiii4e eeke 40mamyAh4th 0 CLI

$300

People are amazed when they learn of the variety of CLIPS we make - steel clips, bronze clips, stainless clips, bigclips,smallclips...clipsinevery conceivable shape and pattern ... clips for every possible use. We can make to print or specification or our Research Department can design a clip for that particular job of yours. B.I.F. (Castle Bromwich) Over 92 years of clip -making is at your disposal. Stand No.B.424. HERBERT TERRY & SONS LTD., REDDITCH London, Birmingham, Manchester; April, 19.48 NEWNES PRACTICAL MECHANICS 217

BALL THE ZYTO MOTORISEDBEARING SAW BENCH Forcrosscutting, ripping,grooving,mitre- nig,bevelling,etc. Takesloin.saw. Spindlerunsin heavyball -bearings, parallel rise and fall Table with rackfeed and canting for bevelling, etc.Right and lefthand mitreslides,approved saw - guards. Vee belt drive, built-in dust chute, swivel motor base. Supplied A.C.200-220., 230-250. Three-phase 400-440. Direct Current. Price and illustrated leaflet free and post free on application.

Threeof-overFIFTY! * We now offer from stock in Northampton, London and Manchester, a THE ZYTO r CAPACITY

range of over Fifty SHIPS' FITTINGS, in two sizes ()in. scale and 1 scale), beautifully finished and nickel plated and ready for easy assembly. PRECISION BENCH DRILLING MACHINE * THE MARINE MOTOR for motor boats up toI metre works on dry 3 jaw, self centring chuck, capacity o -r battery or accumulator, 6-8 volts, weight 15 ozs.Price 3716. * SCALE MODEL STANCHIONS in hard brass, unequalled for accuracy 3 -speeds, drills to centre of 6".Max- and strength-scale -4in. to I foot. imum distancebetween chuck and * STREAMLINIA (Electric Drive) FIBROUS PLASTIC HULL, unpainted, base,to". 5" diam. for building 3ft. 3in. model. Size of table, Price, £3 I7s. 6d. This can be swung clear of work. * For particulars of these and other models now available, write for (SF/12), Price Size of base machined,5/"x5". " Model Ships Catalogue," for Model Ship Builders. Price Complete, £10/17/6 Ex Stock. Write also for (MY12), price 6d. How to Sail your Model Yacht. (Lll2) price 6d. With 3 -jawkeytypeself -centring BASSETT-LOWKEStock List of Model Supplies. LTD. chuck, £11/18/6. NORTHAMPTON TOOL AND London Showrooms : 112, High Holborn, W.C.2. S. TYZACK & SON SPECIALISTS Manchester :28, Corporation Street. 341-345 OLD STREET, -LONDON, E.C.1 You are invited to visit our London or Manchester branches, where our Telephone: Clerkenwell 4004 -5 6 Telegrams :Tyzgar, FInsquare Staff is at your service.

AZOL

0' 4%)

THE DEVELOPER 44 FOR AMATEUR -64',/x4W PHOTOGRAPHERS A VERY highly concentrated liquid How fortunate that you can bestow, at developer. Is most economical. such low cost, a present of such high A little goes quite a long way.Only intrinsic and lasting value as a Smiths has to be diluted with water.Gives Clock. This happy fact is solving the 'gift well -graduated negatives, full of detail fromstainorfog. Fully problem ' everywhere today. Obtain- andfree detailed Time and Temperature tables- able from your local Smiths Stockists. sent with each bottle-make it an easy matter to control development scientifi- cally.AZOL has been popular with amateur photographers for forty years. SHITIIS CLOCKS Ask your dealer for AZOL. Itis onsale everywhere. 'SECTRIC' AND HANDWOUND JOHNSON & SONS, MANUFACTURING CHEMISTS LTD HENDON. LONDON, N.W.4 ESTABLISHED 1743

SCM 126 F 218 NEWNES PRACTICAL MECHANICS April, 1948 I.C.S. TRAINED MEN arein Greater Demand than Ever-Maximum production depends onhigh technicalskill,such asthat acquiredbyI.C.S.Students TENS OF THOUSANDS MORE TRAINED MEN ARE URGENTLY NEEDED NOW-BUT THERE IS NO WORTH -WHILE PLACE FOR THE UNTRAINED Output suffers as soon as you have one severe cash of Ambitious men everywhere have succeeded through dermatitis. Workers lose confidence-and withreason. I.C.S. Home -Study Courses.So also can you. Don't wait until oils have started oil rash orother skin troubles among your operatives.Give them the The man with an I.C.S. Training in any one of the subjects listedbelow knowsitthoroughly, completely,practically. protection of Rozalex, the barrier -cream of proved Andhe knows how to applyitinhiseveryday work. efficiency. Rozalex is easy to apply, savessoap, and is most economical. Accountancy Diesel Engines Motor Engineering Advertising Draughtsmanship Motor Mechanic Aeronautical (State which branch) Motor Vehicle Elec. Engineering Drawing Office Practice Municipal Eng. Air and Vacuum Electrical Engineering Plastics Brakes Electric Power, Light- Plumbing Air -Conditioning ing, Transmission, Quantity Surveying R OZALEX Architecture Traction Radio Engineering Architectural Drawing Eng. Shop Practice Radio Service Eng. 5550 BRAND Auditing Fire Engineering Refrigeration Boiler Engineering Free -Lance Journalism Sales Management Rozalex Limited, 10 Norfolk Street, Manchester, 2 Book-keeping Fuel Technology Salesmanship Building Construction Heating and Ventilation Sanitary and Domestic Building Specifications Hydraulic Engineering Engineeriiig Business Training Hydro -Electric Sheet -Metal Work Business Management Illumination Eng. Short -Story Writing Carpentry Industrial Management Steam Engineering Chemical Engineering Internal Comb. Eng. Structural Steelwork Chemistry, I, & 0. Joinery Surveying Civil Engineering Lettering (State which branch) Clerk of Works Machine Designing Telegraph Engineering Coal Mining Machine -Tool Work Textile Designing Colliery Examiner's Marine Engineers Welding, Gas and Elec. Colliery Overman's Mechanical Drawing Woodworking Commercial Art Mechanical Engineering Woollen and Worsted Concrete Engineering Mine Surveying Manufacturing Cotton Manufacturing Mining Engineering Works Engineering And most of the Technical, Professional, Commercial and Civil Service Exams. ;also C.I.I. Elements of Nat. Insurance. (I.C.S. students preparing for Examinations are coached tilt successful) If youneedtechnicaltraining,ouradvice on any matterconcerning your work and yourcareer isyoursforthe asking-free and without cbligation.Let us send you full information regarding the subject in which you are specially interested.DON'T DELAY.Make ACTION your watchword. The successful man DOES to -day what thefailure INTENDS doing to -morrow. Write to us TO -DAY

Use this Coupon NTERNATIONAL CORRESPONDENCE SCHOOLS LTD Dept. 95, International Buildings, Kingsway, London, W.C.2 Please send me particulars of your Courses in

-Nfa, Name Age SPECIAL (USE BLOCK LETTERS) HANDY CARTON Address D

Addresses for Overseas Readers Australia :140, Elizabeth Street, Sydney. Egypt :40, Sharia Malika Farida, Cairo. India : LakshmiBldgs.,SirPherozsha Mehta Rd.,Fort, ENOUGH FOR Bombay. 200 AVERAGE New Zealand : 182, Wakefield Street, Wellington. ICS JOINTS South Africa :15, Shortrnarket Street, Cape Town. MULTICORE SOLDERS LTD., MELLIER HOUSE, ALBEMARLE STREET, LONDON, W.I April, 19 48 NEWNES PRACTICAL MECHANICS 219 TwoMODE'SNowOF Here's good news :the D.L.P. Eight -in -one Youjust Tool is now available in two models-the D.L.P. Major and theD.L.P. Minor (the Majoris larger). Eight different tools in one compact DIPmake it and unit that will handle scores of different jobsh. Ail/177-PURPOSE FOOL bake it- IN0 hardened jaws. grips Toot.s reversible vice With sI Parallel hardened vice with bender. 2 Piperod andstrip 3 Tube; pin cutter. rod andanvils. 4 Cable,d conical 5Screwing machine. 6 stripper. 7 Cable 8 Punching.

D.L.P. Major Has a Sin. Parallel Jaw Vice. Screw -cutting up totin. diameter. Fitted with geared, detachable handle. D.L.P. Minor 31in. Parallel Jaw Vice. Screw -cutting up to in. Whit, Sin. gas,lin. conduit. The D.L.P. is a precision tool for Engineers, designed and built by Engineers. In use by many famous firms, public utilities, etc. Write NOW for illustrated leaflet. HAMILTON MOTORS, LTD. tritA az& 466-490, Edgware Road, London, W.2 Tel :PADdington 0022. HEr DHB MODELLING MATERIAL MODEL railwaybuildingsand platforms, A Wise Investment ! n model ships and houses, animals and many usefulandpermanent objects S. G. BROWN, Txpe K' Mowing Coil Headphones, with can be made with Pyruma Plastic Cement. the following outstanding You just "make it and bake it" to stone - characteristics,supplythat hardness, and afterwards, according to our High FidelityReproduction demanded for DX work, instructions, paint innatural colours,i.e. monitoringandlaboratory with enamels, poster -paints, etc. Pyruma purposes, etc. is comparatively inexpensive, and is obtain- NOTE THESE CHARACTERISTICS. able in.tins from Ironmongers, Art Material D.C. RESISTANCE, 47 Ohms. Dealersand HobbiesShops. Send Id. IMPEDANCE, 52 Ohms at 1,000 c.p.s. stamp for illustrated instruction sheet on Pyruma modelling to the address below. SENSITIVITY,1.2x10-12 Watts at Ikc,.--.0002 Dyne/cm2.

PRICE 15.5.0 PER PAIR Supplies now available. 'Order from your Local Dealer. For details of other TYPE ' K ' S.G. BrownHeadphones (prices from 30/-to 63/-) Descriptive Literature on request. ask for illustrated Brochure "P.M." HEADPHONES WHICH UPHOLD BRITISH PRESTIGE Write : Dept. tl.H. SANKEY& SON, LT? ,'Phone: ACOrn 5021. *CW744 VICTORIA ROAD, NORTH ACTON, LONDON, W.3.ILFORD EST. 1857 ESSEX 220 NEWNES PRACTICAL MECHANICS April, 1948 DELIVERY FROM STOCKYou have only to press the trigger

Nolongerisitnecessary to go No.1 OUTFIT 75,- Co'mprisiuethe in- about jobs of painting, distempering, valuable Prestacon Press and Tools. whitewashing, etc., in theold complete 55/- laborious way. As Britain's No.1 Mail Order HouseforModellers,we can supply all you want in Prestacon, Now you only need to connect the from a strip of metal to a complete outfit, from stock. Prestacon is a " Crystal " SprayGuntoyour realengineeringjobthatno modeller can work without. electric cleaner, and press the May we send you the Prestacon Leaflet ? trigger,tocomplete such jobs No: 10 OUTFIT without mess or effort and at the includes press, tools, strips, plates, axles, gear and other wheels, etc., same time obtain a much superior as advertised. 84/ - ADDITIONAL MATERIALS finish.Forre-cellulosingcars,cycle Prestaconplates,stripsandother frame's, etc.,itisideal. parts available separately.aslisted. SPECIAL MODEL OUTFITS The " Crystal " Spray Gun will be Each complete with all necessary parts HOW TO ORDER forwarded byreturn,postfree,on to make a realistic model. Send advertised price, or pay No. 44. Four-wheel Lorry 27/6 C.O.D., plus2/-for packing, No. 66.Six -wheel Lorry.. 37/6 receipt of remittance with order. No. 88.Eight -wheel Lorry....47/6 carriage and insurance. EtVGINE-: No. 55. Jeep ... 31/6 TROUBLE71 N.B.Please state make and type of o""fserb:It cleaner wben ordering. A special con- MODELLERS, PLEASE NOTE! Ifollowing nector. desirable with all and essential We carry large stocks of Solarbo Balsa, Dopes, Cements, I makers Ship Kits,Hart's Accessories, Plane Kits,Engines, and with some cleaners,isavailable at Accessories-infact everything modellers need. I E.D., FROG, I MILLS I 316d. extra. Ito repair their I engines up Dept. P.M. I tomaker's I (standards,'and give un- DOMESTIC SUPPLY COMPANY HENRY J.NICHOLLSD equalledser- vice on all, ROAD, 308, HOLLOWAY OALI,LONDON,N.2engine pro- 341, REGENT'S PARK LONDON,N.3 blems. Telephone e 0 PEN ALL DAY Two minutes from (Near Finchley Central Station) Tel: FINchley 5190 NORth 5161 SATURDAY Holloway Road find, 11111111111IMMMIS RECEIVERS-INTERCOMMUNICATORS BARGAINS and DATA - Communications Receiver Type R208 This is a very fine set built with precision ;the frequency coverage is in Ex -Government from to -6o mcis, e.g., 5-30 metres. The receiver with power supply for Stocks working off mains or 6v. battery and TRIPODS, 3ft. high when 6in. loud -speaker is built on a steel erected. Fitted brass thread chassis and housed in a steel cabinet. and bap, web sling for carry- The chassis slides into the front of ing. Inwoodormetal. Suitable for Surveyors. pro- thecabinetand hashandlesfor jeCtors, cameras, dm-14 in withdiawal.The circuit is :Stage playpurposes,etc. of R.F., combined frequency changer PHOTO -ELECTRIC CELL. andmixer,twostagesofI.F. Dozena of applications, e.g., detector, A.V.C. and first A.F. and burglar alarms - 6V6 output.The range 10-60 mc/s counting-door-open-19/6 is covered by a three -position wave - ing, etc. etc. change switch. - Other control* PRESSURE PUMP forex- include Muting,' Phone jacks, Battery GAUGE hausting,com- mains on/off switch, A.F. gain, R.F. Higher and pressing o r gain and B.F.O. The set will work reads 0-150 lbs. liquid pumping Fitted good -heavy brass with open aerial or dipole. The sets, lengthofCop- construction - which are in tip-top 6ondition, weigh 8olbs. and measure 23 in. by 12* in. by rn in. per tubing. 7/6 spring loaded - Higher fittednon-return AlsoLi/o/oshOuldbesentfor PYROMETER valve,and Carriage packing case, this will be refunded stands the reputation of TYPE THER- manual valve. extra past as soon as the packing case is MOMETER Length 61n., L1211010 received back. Harbutt's "Plasticine." For reads 0-100. diameter 7/6 Centigrade 10/ 11n. BC.348. This much coveted receiver has a frequency range of Zoo -Soo Kc and more than fifty yearsithas 1.5-18 Mc/s.Six position switch brings separate frequency calibrated dial into position been the only reliable material DOUBLE GONG BELL.Very loud. and superfine Vernier tuning unit gives 90 turns of tuning for each band-two stages Ideal for garages, workshops. for model makersof all ages. etc. 200-240 volts,A.C. 24/6 R.F.-three stages I.F,-crystal filter-voltage stabiliser-automatic noise compensation mains. -constant sensitivity on all bands-phone and speaker output-all standard 6.3 volt Whetherfor lipme amusement 0-1MILLIAMETER. Fer4anti. valves-complete with plug-in Dynamotor for z8 volts.Note this can be removed Bakelite case, flush mounting. 1.2/6 and standard A.C. mains equipment can easily be fitted in its pike.(We will supply - designing - experimenting Diameter 211n.Moving coil.I v details, or do the job if required.) Brand new and complete £28/1o/o plus io/- carriage, -or the handyman, "Plasti- " TINY TIM "' 1-VALVEI RADIO plus io/- packing (case returnable). for medium waves(bightand INTERCOM.A1134 complete with valves cine "isindispensable. Be- Home Programmes).Kit, includ- ts/-.Or if you want to build a loud - ing.Valve,Tuning' Condenser, speaking intercom. we can supply a complete kit comprising two loudspeakers in causeitisever -plasticand Chassis, Coils, in fact everything veneered cabinets, the amplifier 1134 and diagram with full instructions £4 post'paid. except dry batteries.Full, easy - hygienic, " Plasticine " has to -follow instructions, which 25/. Rii55. We can supply this famous receiver, which is doing good service the world will ensure good results. over, complete with ten valves and in tip-top condition, tested before despatch. Price hundreds ofother uses, and it Plus packing and insurance,2/6. in/solo plus Lx carriage, to/- of which we will refund if you return the transit case. Suitable H.T. Battery 9"-. never deteriorates. DATA BOOKS.Copied from official publications, giving circuit diagrams, component MULTIMETER, 17 ranges. A.C./D.C. volts, m/amps & ohms. New and i7 valuesandusefulnotes ; BC.342-BC.348-BC.3 I 2-BC.22 I -R.2013-R.1o3A- perfect.Ail i-R.ii55-W/S.22-RT.18-W/S 1 6A-all at 2/3 each, also Walkie-Talkie 58, 3/6.-" Demobbed "Valves,2/6. WINTER LIST free on 'Plasticine CarriagePaid (Dept. K) application with stamp. HARBUTT'S PLASTICINE LTD., INSTRUMENT CO BATHAMPTON, SOMERSET. W. D. SALES (FormerlyBull's Ex -Government Dept.) LONDON: 68, Victoria Street, S.W. x. Harrow Rd., London, WI/Section PM, 42-46, Windmill Hill, Ruislip, Middlesex April, 1948 NEWNES PRACTICAL MECHANICS 221 HIGHSTONE UTILITIES CRYSTAL SETS Our latest Model le itREAL RADIO RECEIVER, which isfittedwitha CRYSTALPXRMANENT DETECTOR. ,WHY NOT HAVE A SET IN YOUR OWN ROOM OR AS A STAND-BY --2/6,post6d. DE LUXERE CEI'VRII inpol- ishedoak cabinet. RATCHET SPANNERS 18/6post 1/-. SnarePermanentDetectors,2/.each.When ordered separately, 2/8.Postage, 3d. .0003 Pre-set Condensers, post 3d. Headphones, HUGE demandenables us to brand new, S. G. Brown, G.E.C., etc., 15/-, 23/-, offer " Leytool " Ratchet Spanners at and super -sensitive, 30i. a pair, postage6d. priceslittleabovethosepaidfor A Brand -New Hand -Driven MICROPHONES ordinary good quality spanners. They Just the thing for impromptu concerto, room to save time and Money because they GENERATOR for ONLY 251 - room coniinunication, etc.Bakelite table model, work faster, operate more easily, and 6/9;Suspension type,8/6, post6d. Super Model get into those inaccessible places where Will giveoutputof300v. H.T. and 6v. on stand, 12/6. Fittinginstructionsincluded. ordinary spanners will not go. 3.5 amps.L.T.Geared 43.1.With fixing Mike Buttons, 2/6. Transformers,5/.. Public plate.Handle required,easily made or Address Transverse current Mike, 37;6, post 1/.. They are a sound Britisfi engineering All microphones have transformer incorporated. job,made of carbon chromesteel, obtainable. MORSE KEYS AND BUZZERS hardenedalloverandnegradised. ENGINE DRIVEN ALTERNATORS. Standard size keys wired to work Buzzer or Lamp, Availablein8standard sizestofit Type U2-1,200 watts. Excitation 24v. 1,200-2,400 3/-., post6d. Slightly smaller keys,2,6,post4d. zsonutsizesinB.A.,.Whitworth, D.C.As used in aircraft. Plugs (for Jacks) with short length of twin tlex, B.S.F.,S.A.E.,Metric andsquare. cycles. Brand new -ONLY 251-. 1/6,post4d. Special sizes made to order. ADMIRALTY SMOOTHING CHOKE. BELL TRANSFORMERS Alsoavailable, Mechanic's Set of 5 Very heavy duty 2 Henry 800 m'a. D.C. These guaranteed trans- " Leytool " Ratchet Spanners in Canvas Brand New. ONLY 2216. formers work from any Wallet. 10 Henry A.C. Mains, giving 3, 5, WriteforIllustratedI.e.afletgiving SMOOTHING CHOKE. or 8 volts output at I sizes and prices. 250 mla.Chassis mounting impregnated amp., operate bulb, tropically, ONLY 151-.

buzzerorbell. Will supply light in bedroom or POST OFFICE MICROTELEPH ONE. larder, etc. PRICE 7/-.Post6d. A complete brand new head and breast set BELLS for use with either the %Oa to atCrie00/S'FORTHE MOST UP-TO-DATE consisting of breastplate microphone with above or batteries,6/-. Post W. pair of 60 ohm headphones on a stainless SOLDERING IRONS steel headband with connecting leads and AdjustableBit,allpartsreplaceable and fully AND EFFICIENT jackplug. ONLY201-. guaranteed. 200;300 v., 60 watts, 9/6;150 watts, POST OFFICE RELAYS. 12 assorted 12/6, post 6d. Small Soldering Irons,for use DESIGN on gas, 1/4.Post4d. Resin cored solder for easy Post Office type Relays with change -over soldering,6d.packets,or11b. reels,6/-. Postage contacts. Brand new and boxed for 241-. extra. All Leytoolsareentirely MORSE TRAINING OSCILLATORS. Sparking Plug Neon Testers,very sensitive, original and patented de- with vest pocket clip, 313, or with gauge, Precision Ratchet Universally 4 -bladed A complete battery -operated 2 -valve Pocket signs.Write for illustrated buzzer with artificial interference circuits. 3/8,post3d. Hand Drill Spanners Jointed (Mechanic's Socket Screwdriver leaflets. The R.A.F. aid to learning Morse ! Pro- Ex-R.A.F.2 -valve(2 -volt)Microphone Set) Spanners vision for batteries in cabinet (size 9in. x Amplifiersas used in plane inter -corn., 8in.x 81in.). Suppliedwith 2valves, in self-contained metal case, which in Export Agents in all countries. Names and Addresses on application. guaranteed for12 months ! ONLY 271 - turn is housed in a useful wooden box, LEYTONSTONE JIG & TOOL CO., LTD., High Road, Leyton, London, E.10 (Carr. & pkg. 216).Morse keys 216 extra. 10/- each (less valves), post1/6. . Telephone :LEYtonstone 5022-3-4 Headphones SI-extra. Transit cases 216 Field Intercommunication Sets,ready for extra.Jack Plugs 116 extra. use, complete with ringing hand generator, bell, signal lamp, worse key, relay and all necessary jacks and switches. ,Con- tained in a strong metal ease with circuit diagram,25/-each,carr. 2/6 ;47/6 pair, carr.2/6. Similar instrument, less generator and bell, but including Buzzer, 15/-,carr.2/- ; 27/6pair,carr.2/6. New hatidcomb sets, for use with above, 7/6,post6d. G.P.O. Twin Telephone Bells, mounted on box, complete with induction coil,7/6,post8d. Telephonehand generator, with handle giving 100 volts A.C.,9/6,post1/6. Bell,4/6.post6d. Relays, useful for many purposes,2/6, p6st4d. Hand Microphones,with switch in handle and lead,4/-.Similar instrument moving coil,7/6,post6d. Headphones,reconditioned and in good order, 5/6 a pair, post6d.(better quality, MAGNETIC RELAY TYPE APW 6123. 7/6pair). As illustrated.Coilforoperation on New Headphones, 10/-a pair,post6d. 230v. 50 cls. A High Speed relay at the Balanced armature type (verysensitive, fantasticallylow price of St- (Carr. & pkg. and very suitable for use with crystal sets), Manufacturers of 116). 12/6a pair, post6d. NewSingle Ear- pieces, 3/6.Bal. armature -type,5/-,post TRANSMITTER RECEIVER UNITS 4d: Headphones withmoving coil mike, DRAWING and FOR AIRCRAFT RADAR. Complete 15/-.Similar phones with throat mikes, with 12 valvesand rotarytransformer 12/6,post8d. Headphone cords, 1/3a SURVEYING I2v. input, 480v. 40 mla output. Frequency pair, post3d. ( £4per 100).Replacement coverage 58-210 Megs.Valves supplied : bandsforheadphones, 1/3,post4d.( £4 2 of EF50, 6 of SP4I, 3 of DI, I of E I 148. per 100).Wire bands, 6d.per pair( £2 INSTRUMENTS ONLY 3916 (Carr. & pkg. 716), per 100). HANDYMAN'S PARCEL.An oppor- Rotary Transformers, 12 v. D.C. input, tunity to obtain 50 useful and valuable radio in sound -proof cabinet, for Car Radio, etc., and electrical components worth atleast will also light two 25 w. lamps in series, or SLIDE RULES £10foronlyEll-. Allnewgear.A as a motor,22/6each, earn2/6. typical parcel will contain :-P.O. Relays, Goodmans10in.P.M.Loudspeakerin electrolytic condensers, headphones, cabinet with, volume control and trans- meters, potentiometers, insulators, micro- former,35/-, carr. 2/6. phones, switches, spirit level, valveholders, DRAWING MATERIALS vibrators, coils, rectifier, plugs and sockets, METERS,600rn.a.,Sin., 15/-; Double reading 40/120 m.a., Sin.,ni/e., variable condensers, etc. etc. 8/-;20 amp., 2f in.,nail.,7/6 ;15 volt SEND 6d. STAMP FOR LATEST LISTS. iu., ni/c.,9/6 ;30 amp.,6in., Ind Switch- board mounting,35/- ;6,000v. in., DRAWING OFFICE Post Orders ONLY to 3, Robert St., HOC..23/10.All postage extra. Hampstead Rd., London, SEND ld.S.A.E. FOR ILLUSTRATED LISTB.P.OF USEFUL ELECTRICAL STATIONERY ACCESSORIES. Money refundedit'not completely satisfied. Letters only. Please includepostage; anyexcesswillbe re funded. A. G T-140 RN TO N LTD HIGHSTONE UTILITIES Sper4:144-to 41 GAR.TIIDEIT.fAANCHEfTER. 3, MAIL ORDER SUPPLY CO., 58, New Wanstead, London, Dept. PM., 24, New Road, London, E.I E.I1 TS Stepney Green, 2760-3906 222 NEWNES PRACTICAL MECHANICS April, 1948

PREPARE FOR COMPETITION NOW ! As the Engineering Industry swings into its normal stride, the inevitable competition for the secure and well -paid posts will return.Itis the man who stands out from the rest because he is technically trained who will be in the happy position of taking over the more responsible, more secure, and better paidpositions. " ENGINEERING OPPORTUNITIES " will show yea how to get this all-important technical training quickly and easily in your spare time.This 100 -page book is full of valuable information and explains the simplest way of preparing for recognised Examinations.Among the courses described are : MECHANICAL ENGINEERING GROUP ELECTRICAL ENGINEERING GROUP A.M.I.Mech.E. Mining Practice A.M.I.E.E. Electricity Supply A.M.I.E.D. Estimating City & Guilds Electrical Meters City & Guilds Foremanship General Electrical Eng. Electrical Design General Mechanical Eng. Jig & Tool Design Alternating Currents Illumination Diesel Engines Viewing & Inspection Power House Design Installitions *Draughtsmanship & Tracing Welding Traction Telegraphy Works Management Sheet Metal Nork Mains Eng. Telephony Press Tool Work Maintenance Eng. Mining Electrical Engineering Pattern Making Metallurgy Foundry Practice Refrigeration WIRELESS GROUP A.M.Brit.I.R.E. Advanced Wireless COMMERCIAL ENGINEERING GROUP C. & G. Telecommunications Radio Servicing A.M.I.P.E. Cost Accounts General Wireless Television Commercial Eng. Languages Short-wave Wireless Sound -film Projection Eng. CIVIL ENGINEERING GROUP AUTOMOBILE ENGINEERING GROUP A.M.I.C.E. Mining Surveying A.M.I.M.I. General Automobile Eng. Inst. Mun. Engineer Road Eng. City & Guilds Garage Management A.M.I.Struct.E. Hydraulics Automobile Repairman Eleetrical Equipment M.R. San.l. Municipal Eng. Course High Speed Diesels City & Guilds General Civil Eng. Sanitary Inspector Structural Eng. Specification Reinforced Concrete AERONAUTICAL ENGINEERING GROUP Structural Design Railway Eng. A.F.R.Ae.S. Aero Engines R.A.F. (Maths.) Navigators' Licences Pilots' Licences Aeroplane Design SURVEYING ANDBUILDING GROUP A.R.B. Licences Meteorology A.R.I.B.A. Costing & Valuations F.R.I.C.S. Heating & Ventilating A.M.I.H. & V.E. Clerk of Works UNIVERSITY DEGREES L.I.O.B. Surveying & Levelling London Matriculation University Entrance F.A.I. Building (all branches) School Certificate Intermediate B.Sc. * Our Diploma is accepted for Graduateship of theInst. of Engineering Draughtsmen and Designers. WE DEFINITELY GUARANTEE "NO PASS NO FEE " If you are earninglessthan £10 a week you cannot afford to miss reading " ENGINEERING OPPORTUNITIES" ;ittells you everything you want to know to make your future secure, and describes many chances you are now missing.In your own interest we advise you to write for your copy of this enlightening guide to well -paid posts NOW-FREE and without obligation. BRITISH INSTITUTE OF ElGINIMING HOROLOGY 410A, SHAKESPEARE HOUSE, 17, STRATFORD PLACE, LONDON, W.1 THE B.I.E.T. IS THE LEADING INSTITUTE OF ITS KIND IN THE WORLD April, 1948 NEWNES PRACTICAL MECHANICS 223

SUBSCRIPTION RATES (including postage) Inland - - - 10s. 6d. per annum. Abroad - - - 10s. per annum. PRACTICAL Canada -- - 10s. per annum. Editorial and Advertisement Office :" Practical Mechanics," George Newnes, Ltd. Tower House, Southampton Street, Strand, W.C.2 'Phone : Temple Bar 4363 Telegrams :Newnes, Rand, London. MECHANICS Registeredat the G.P.O. for transmission by Canadian Magazine Post. Owing to the paper shortage "The Cyclist," "PracticalMotorist,"and "Home Movies" are Copyright in all drawings, photographs and articles temporarily incorporated. published in " Practical Mechanics " is specially reserved throughout the countries signatory to the Editor :F.J. CAMM Berne Convention and the U.S.A.Reproductions orimitations of any of thesearetherefore expressly forbidden. VOL. XV APRIL, 1948 No. 174

FAIR COMMENT BYTHE EDITOR Science in Industry INDUSTRIES have developed as a resultcomes from the University Branch Committee,been approximately two-thirds of the total of the advancement in applied science.but this does not preclude the Departmentfor1946, when the average was 964.A The invention of the steam engine wasof Scientific Industrial Research from mak-satisfactory number of vacancies has again responsible for the industrial revolution ofing grants to assist individual research workersbeen notified by employers, the total for the the last century.The discovery by Williamin the university in pursuing items of researchyearbeing1,048.Despitethereduced Murdoch that gas distilled from coal couldwhich seem to have special prominence. number of engineers available for nomina- be used for illumination established what is The D.S.I.R.alreadyreferredtowastions, the income from appointment fees still our largest chemical engineering industry,formed during World War t, and it wasincreased by to percent.compared with the production of coke and coal gas. Tennant,charged by the Government with the impor-the previous year, the sum of £1,179 being a century ago, by the manufacture of bleachingtant task of encouraging science in industry.received from 254 engineers. powder, created a new industry, and Nelson's Now in D.S.I.R. there are13national Thisreducednumbercanpartlybe invention of the hot blast in the manufactureresearchestablishments,financedentirelyaccounted for by the fact that there are fewer of pig iron revolutionised smelting. frompublicfunds ;thatisto say,thatengineers actually out of employment and The distillation of oil from shale was awherever they may be situated geographicallythat the demobilisation rate from the Forces discovery of James Young, and he virtuallythey work for the country as a whole-forhas been decreasing.Itissatisfactory to foundedthepetroleumindustry. TheScotland aswellas England.Their workbe able to report that the decrease in numbers surfacing of roads is due to Macadam. Thediffersfromthatofuniversitiesmainlyhas been evident in all age groups, although waterproofing of fabrics was due to the discov-because their taskisto apply science tothis was slightly more noticeableinthe ery by Macintosh that naphtha dissolved indiaparticularobjectives,tothebuildingofgroups undertheageof 35. The rubber.Most of these developments tookbetter buildings, the making of better roads,average of the men on the Register has place over a century ago when industry andthe better use of fuel and so on. Our researchincreased from 34.4 to 35.6, and the average science were detached. Both science andstations have, of course, occasion to carry out aof the men placed from 30.1 to 31.5 years. industry, however, have developed in com-great deal of fundamental research-objective An analysis indicates that less than to per plexity since that time, and they now runfundamental research, in other words.Theycent. of the engineers on the Register are ancillary to one another. dothisbecauseithasbeen abundantlyactually out of employment, and most of The means for bringing science to bear onproved that fundamental research on a prob-these are over 45. years of age. Inthe industrialproblemsis highlyorganised.lem is often the quickest way of finding amajority of these cases, other factors which Industrial research has to -day become a busi-practical solution to it.For example, a fullrender the engineers difficult to place include ness in itself. understanding of the way bacteria and othereithera requirement that work must be The scientific effort in Great Britairit is inmicro-organisms affectfish and the physicalwithintravellingdistanceofaspecified the hands of three branches-research inphenomena which take place when fishis address, a high salary indicated as a minimum, industryitself,Government research andfrozen are often the Most direct methods' ofor work required in a specialised field. research in universities and technical col-discovering the bestpractical methods of In the final quarter of the year there was, leges.It is in the universities and technicalpreserving it.Again, a fundamental studyas might be expected, some decrease in the collegesthat really revolutionary industrialof what happens when a metal corrodes willrate at which vacancies were being advised, advances have their origin.The discoverycertainly help in finding the means of prevent-and in a number of cases, after the Bureau of X-rays was made in the pursuit of funda-ing corrosion. hadnominatedengineerswho appeared mental knowledge, and it was only after their From these brief observations it will besuitable, the employer advised the Bureau discovery that the possibility of their manifoldseen how very important itisthat firmsthat the question of making an appointment applications in medicine and industry wasshould make use of the assistance providedwas being held in abeyance in view of the realised. for them.Most large firms to -day have theirreductions incapital expenditure. own experimentallaboratories,butitis The number of offers made to engineers Location of Aircraft desirable that every firm of any magnitudeas the result of the Bureau's introductions THE first attempt at the location of aircraftshould have such a department, in view of thegreatly exceededthenumberofactual consisted in trying to detect them bycompetition we are meeting in the industrialacceptances, and the housing situation must the sound or the heat they emitted.Thesemarkets overseas. be recognised as the most serious obstacle in direct methods were unsatisfactory, and it We want new methods and new processesthe filling of vacancies.This factor not only was by combining a technique used for andiscovered. There are plenty of men availablepresents itself in this country but overseas, entirely different purpose, namely, the studywho are qualified to start such departments,and numerouscaseshavearisenwhere of the electrical layers of the upper atmospherewhich will provide an opportunity for employ-engineers have indicated that they would by wireless reflection, together with the chancement tof those whose education suits themhave accepted posts for which they were observationthatshortradio waves werefor filling scientific posts. nominated were it not for the fact that living reflectedbyaircraft,thatpracticalradar accommodation for their families could not was founded. ProfessionalEngineers'Appointmentsbe promised in the near future. Itwas Clerk Maxwell who placedthe Bureau Since it commenced to operate the Bureau sciences of electricity and magnetism on a DURING 1947 the average number ofhas succeeded in filling some 5o posts overseas, quantitative foundation, on which the radio engineers on the Register was 634,but, although a number of engineers on the and electrical industries of to -day are based. 127of thesebeing. primarilycivil,260Register areanxioustoemigratetothe The main provision made by the Govern-mechanical and247electricalengineers.Dominions, the Bureau has had difficulty in mt.ntfor the support ofthe universitiesThe number of registered engineers has thusfinding candidates. F.J.C. 224 NEWNES PRACTICAL MECHANICS April, 1948 A Portable Entar. Cabinet Constructional Details of a Compact Appliance for the

Arriateur Photographer. ByL. C. MASON

5 theolddamagedsurfacehadbeenfirst to give access to the drawer.This was planedoffthefinalthickness camerealised before building was started but it down to about Bin.So the coveredwas decided that the advantage of a clean frame idea was abandoned, and a plainand symmetrical appearance when not in use box type of job started from the solidwould outweigh any slight disadvantage in timber.The length of the sides necessitated an edge Picture Cheir to edge join, but as these are subject to little bend- ingstrainagluedjoint withareinforcingstrip insidehasprovedquite satisfactory. The bottom consists of a sheet of hard- board supported by a 6in. wide plank front and back. The weight supported by the bottomisallwidely//.. Fig. r.-The completed cabinet with bench flaps distributed - consisting erected as set up for enlarging. mostly of the enlarger baseboard -so that a fairly light floor is sufficient here. The back is Felt Covering cut down the amount of time wastedmuch the same, being covered Glued over in preparing for an enlarging session,by another sheet of hardboard End and to keep all the apparatus readyin the same way that a picture to hand in one place, it was decided to buildfranie is backed.The back is a mobile cabinet which would hold everythingfurther stiffened by a strip of necessary, and at the same time provide spacethin wood running diagonally for working. The accompanying illustrations across, which gives rigidity to 1114, show the design finally evolved.Facilitiesthe whole structure. Further Mtn Felt Pad Glued on which it provides are: storage for all neces-help inthis direction is given sary bottles up to 4o oz. size and for dishesby a shelf bracket fitted each up to t5in. by r2in., a paper storage drawer. side in the angle between sideFig.3.-Detachable bracket forsupportingtheside flaps big enough to take up to t5in. by rein. paper and bottom. of the bench top. lying flat, space for the enlarger and masking The drawer arrangement may be open to having to open the doors to get at the drawer. frame withoutdismantling and, finally,a criticism in that the doors have to be opened One visible drawer exti pidin; from one side folding bench -top 48in. by r6in. Other abouttwo-thirdsofthe features are the provision of castors, enabling way across the front would itto be moved easily from room to room, look distinctly odd.Partly and an external appearance when not in use for this reason, too, it was which gives no indication of its real purpose. decidedtofittwohalf - The outside finish can be arranged to match widthdoorsratherthan other furniture in the room whereitwill 12. one large one. Another normally live. consideration-in viewof The whole job was designed in conjunction /9. where the cabinet would with the other pieces of apparatus to be used Draw be used-was that narrow with it, so as to produce the most serviceable Dish Pack 4 Bars of Runners doors would ,take up far article possible.The inside dimensions were /-X lessroom whenopened fixed chiefly by the size of the enlarger; thus than would one the whole it was made high enough to take the enlarger width of the cabinet. So column and deep enough from front to back far,thisarrangement has to take the baseboard, with some half an inch - rxi" not seemed atallincon- to spare in each case, giving measurements venient, as both doors can of 36in. high by t6in. deep. be left open when working. The width decided on was half the length The doors meet edge to of bench -top required, for a reason which Kinserloser Sufficient edge down the middle of will appear presently.The paper drawer is to Cleat (Norge, the cabinet, with as close located on the right, as to work from left Column ajointaspossible.The to right is-to me, at least-the most natural RH.Beerers left-hand door shuts' on a way. This means accommodating the en- Screwed to spring -loadedball Cabinet Snye. catch, larger on the left, where the space for it can 12- the line of the two door beseen by theshelf arrangement inthe edges being concealed by photographs.This layout can be reversed, All Bearer a vertical strip glued and of course, if the other way is preferred. Strips 4 X pinned to the front edge of theleft-hand door. Details of Construction Thestrip ispositioned When itcame totheactualbuilding, material was unobtainable.It was originally intended to use plywood to cover a frame- work, but this proved out of the question. Fig.2.-The frame- Eventually, after a long search an old office work ofthecabinet, cupboard waspurchased whichprovided showingthearrange- more than enough material.This was rather ment of shelves. thicker than was necessary, but by the time April, 1948 NEWNES PRACTICAL MECHANICS 225 exactly in the middle of the front, and in enough below the drawer additiontoproviding some relieftothe toaccommodatenicely otherwise plain front,servesto keep the thebiggestbottle in right-hand door closed. This strip coulduse-in this case a 400z. well be of a different kind of wood or finish bottle of hypo. The bot- from the rest of the cabinet as an aid totom shelf was raised high appearance, although it is all the same in theenoughtogiveample cabinet shown (Fig.t).No handle for the roomfortheenlarger door has been fitted, as it was found that the baseboardtoslidebe- strip down the middle provided adequateneathit,with acoiled finger grip for opening. However, a singleflex lead as well. So the drop handle mounted on the strip wouldlocation of the shelves is no doubt add to the appearance if thoughtto a large extent automa- worth while. tically fixed. The dish Shelves rackontheleftwas fixedat a height which The shelves are small pieces of hardboardjust clears the top of the supported on racks.The left-hand edges ofenlarger lamphouse when the shelves approach to within an inch of the enlarger column to provide the largest pos-in its lowest position. sible area; this means that nearly half of theBench Top enlarger baseboardis accommodated under Attention can now be the bottom shelf.Consequently the shelvesturned to additional fea- cannot be supported from the bottom of thetures affecting the work- cabinet, nor is the back designed to take any ingoftheapparatus, weight, sotheirleft-hand edges are fixedconsistingofabuilt-in workbench and the ques- R.H Side tion of mobility.Various of Cabinet arrangements of detach- ableandfoldingtops were considered and dis- carded until the presentFig. 5.-Cabinetwith doors open,showingthedispositionof Optional system w a s evolved, sh :lves and contents. which works very well. Brass Bush It has the merits of simplicity and sturdiness,in Fig. 3, these each consist of two lengths and does not add appreciably to the size ofof wood linked together with a short length the cabinet.The only addition made to theof picture chain.One piece is clamped ver- bare cabinet is a second top.This is in thetically to the side of the cabinet by a kin. form of two flaps, each half the size of thebolt through its top end, while the lower end main top, and each hinged at its outer edge.carries a step on which the strut piece rests N. B. L.H. Plate The flaps open out, as shown in Fig.u, towhile leaning out and supporting the flap. Need Not provide a workbench 4ft. long.As some sortThe step is a block cut off the same strip and be Recessed of a detachable support for the flaps seemedscrewed securely to the end of the vertical the best arrangement, it was considered in- strip.The end of the block on which the .4/1 Dimensions advisable to have these overhang more than strut rests is slightly angled inwards to ensure According to t2in. as one at least would probably have tothat the strut lodges securely.The bottom Material Available bear most of theweight ofthe enlarger.end of the strut is cut at an angle to match Fig. 4.-Details of the bracket -bolt anchorageThese two when folded in make a dividedthat of the step, and the top end rounded off on the side of the cabinet. top to the cabinet 2ft. wide, thereby fixingwhere it contacts the underside of the flap. the width -of the cabinet itself, as was men-The weight of the flap is thus converted to a straight pull on the chain, the end of which Ationed earlier. The hinges for these flaps are to vertical .rails suspended from the top. sunk into the cabinet top and into the flaps isanchored near the bolt.This bolt isa tin. by tin. strip is screwed to the undersidethemselves so that the flaps lay perfectly flatlength of kin.steel rod having both ends A the top from front to back and the upperwhen folded in, and form a working surfacethreaded kin. Whitworth for a short distance. ends of the rails screwed to this.The com-as free from projections as possible, whenOn one end isfitted a wing nut, which is plete assembly of racks forming the shelvesextended. With careful fitting the dividingrun tightly down to the end of the thread can very well be made up as a whole andline across the top when closed is not veryand the end of the bolt riveted over, fixing treated as a unit for fixing in the cabinetnoticeable. the nut solidly in one with the bolt.This is (Fig. 2).The right-hand edges are supported passed through the upright member of the on similar strips screwed to the cabinet side.*Supporting Brackets bracket and through a hole in the side of the A narrow " fence " of the same hardboard The supporting brackets are somewhat un-cabinet, where it screws into a hole tapped as the shelves isfixed to the vertical railsconventional, but quite successful.As shownin a small metal plate about 3/16in. thick, along the left-hand edge of the upper shelf to prevent small articles being knocked off the shelf on to the enlarger.The upright Flush Riveted rails also carry atin. by kin. strip running from back to front of the cabinet to serve as to Plate one runner for the paper drawer. A similar strip attached to the inside of the right-hand wall of the cabinet forms the other.These should, of course, be exactly opposite each other so that the sides of the drawer do not bind. The drawer is gin. deep although the sides Swivel -Pin k;PI slope down to only sin. deep at the back. Lightly Washers This allows the drawer when halfway open Riveted .Over Split Pin in to tip downwards in the front, providing easy 4Hole access to the contents.There is no visible handle on the drawer ; this omission is delib- erate in order to provide the greatest possible 11" size of drawer. The space available is utilised To Suit Fixing to the full, as the doors actually touch the Screws drawer front when closed.In place of the usual drawer pull thereisasmallfinger bar under the front edge ofthe drawer, attached by two screws through the bottom. The shelves are spaced according to what they have to carry, and as it seemed reason- able to have developer and fixer bottle to hand on the tonshelfthis was positionedfar Fig. 6.-Details of the double castors. 226 c4EWNES PRACTICAL MECHANICS April, 1948 attached to the inside of the cabinet (see alsomark thebracketsLeft and Right whensteelbar, flushrivetedina'lin. square .Fig.4). This provides a simple but veryadjusted, to be sure of having the top alwayspiece of 3/16in. steel plate.The links are secure fixing.The chain isattached ata level. sin. square mild steel, and are just a straight point near the bolt by a screw thfoligh the sawing and drilling job.A smear of fairly end link.Small pads of green baize or feltPainting and Finishing heavy oil on the spindles when assembling are glued to each end of the upright on the When all the construction work is finishedensures free running under load. side bearing against the cabinet, so as to avoidthe bench top should receive a good under- damage to the polish.A similar covering iscoat and a top finish of white enamel or hardElectrical Connections glued over the end of the strut wheie it comesgloss paint to facilitate wiping down.Let the On the back of the cabinet, midway along into contact with the underside of the flap,paint dry thoroughly hard before closing thethe top edge, is fitted a two -pin socket. This as this surface is the top of the cabinet whenflaps down. The rest of the cabinet wasis of the flat type and is actually the socket the flaps are folded in.The length of thestained dark oak and polished with shellachalf of a pair of connectors.The two halves chain is determined by adjUSting the anglevarnish in the manner of french polish. of the socket are held together by two 6 B.A. of the strut resting on its block so that a screws ;thesearereplaced bytwothin ruler edge laid along the flap and the cabinetCastors round -headed wood screws which attach the top shows the two to be in line horizontally. It was originally intended tofitaset ofsocket to the back of the cabinet. A flex lead The position of the end link of the chain issprung castors of the dinner -wagon type, butfrom the socket hangs coiled on a hook just marked on the strut when its working positiona change was made for three reasons:thebelow, and when setting up is plugged into has been fixed, and the chain screwed to theweight of the cabinet when in action waseither a lighting point or a lampholder and strut. On dissembling, the collapsed bracketsdeemed to be somewhat heavy for the smallerconnections for the enlarger, safelight, and are stowed in the shallow space under thetype of castor ; as solid a support as possibleany other electrical apparatus are then taken bottom shelf beside the enlarger baseboardwas required for the enlarger and, lastly, asfrom a multiple adapter socket plugged into (Fig. 5). the height of the bench was very convenientthe one on the cabinet.Light rubber -covered The left-handplate into which the boltfor working, it seemed undesirable toraise cable is advised for the permanent socket, as holding the bracketisscrewed isattached it much more.So a set of special castorsthisisless likely to lead to trouble in the straight on the inner side of the cabinet, butwas made. These areallthat could beevent of chemicals getting splashed on it. that on the right has to be sunk flush intodesired, and drawings in Fig.6 are given In use, all that is required to convert any the side.' This is to avoid fouling the right-should the constructor consider their produc-room into a fully equipped darkroom is to hand side of the drawer.The plates can betion worth while.It will be seen that eachwheel in the cabinet, attach the two bracket any odd piece of strip steel or brass somecastor isfitted with twin wheels, which notbolts and plug in.The time and effort saved 3/16in.thick, having a countersunk holeonly makes them a " heavy duty " type, butin getting ready and clearing away has made either side of the $in. tapped hole.In thesimplifies construction. A valuable feature isthe job well worth while. cabinetillustrated,theholeintheside that they raise the cabinet only I4in.The If a cabinet of the dimensions shown is through which the bolt passes was bushedmaterial throughout is mild steel, with theused in the bathroom,itwill probably be with a short length of kin. brass tube forexception of the wheels which are tin. slicesfound that either flap is high enough to over- the. sake of appearance. A neat plate on theoff sin. round aluminium bar and the spindleshangthewash -basin. By standingthe outside would look equally well, but whatever which are silver steel.The wheels are sawncabinet sideways on to the basin prints can fitting is chosen (and such a fitting is purelyoff the bar, faced and drilled at the one set-be transferred from a fixing bath on the flap optional) it must be flush with the cabinetting in athree -jaw chuck, reversed in thestraight into the basin for washing, thereby so as not to interfere with the location ofchuck and faced back to thickness. Thesaving room on the bench and avoiding drips the flap support.It might be advisable tocolumns are plain turning jobs out of mildof hypo across the floor.

accuracy to three places, which, of course, is ten times the accuracy.You may be able to Mathematicsasa Pastime read .66 inches for your third part ;you are very unlikely to read .666 inches. Reaching Towards Accuracy. By W. J. WESTON We must reconcile ourselves to the existence of incommensurablesin our mathematics. AN interesting and most instructive seriesfirst sight, puzzling conclusion. You describeThere are measurements that we cannot, ofletters published recentlyina circle on the diameter X Y (Fig.r) :thewhatever our skill and our patience, express PRACTICAL MECHANICS dealt with thecircumference is.7r times X Y.You describe trisection of an angle.To what point oftwo circles on the two halves of X Y.Then accuracy can we pretend ?The correspond,thetotalcurveofthe twoequalsthe ence brought out again this inescapable fact,circumference of the first,equals, thatis, that absolute accuracy in our measurementsrtimes X Y. You proceedfurtherto is attainable only by happy chatice.For thesmaller sub -divisions, four, eight, and so on. '8 most part we must content ourselves withThe length of the curve remains constant.Fig.2 (Above)-Tri- approximation ;and for the practical affairs But you come to such a division as makes secting a line. of lifeapproximationsuffices.You havethe curve merge into the straight line.It never drawn a real line, however fine a pointwould almost seem that the length of the on your pencil ;for a line is length withoutcurve has shrunk to less than a third of itsFig. 3.-What length breadth;and under the microscope yourfirst length, that 7t equals I. But, of course, is the diagonal? line is a broad black groove. . You have neverthatisonly because the limitation of our made a point on your paper, either for apowerspreventsusfrom discerningthein terms Of another measurement.Here, for point has position but no magnitude.Yetcirclesthatareyetthere ;our so-calledexample,isa one -inch square (Fig.3). your lines and your points serve well enough" line " has the breadth of a diameter of a What length is the diagonal ?It is A/2 in practice. circle. inches ;but how many inches is that ? It is the inadequacy of our powers and of That no exact method of trisecting an angle You patiently work it out, to 1.414 perhaps, our most exquisite drawing instruments thatisavailable was the conclusion reluctantlyeven to 1.414214 ; -you then re-echo Macbeth's reached in the correspondence referred to.exclamation, " What !will the line stretch Yes ; but even when you get what you call anout to the crack of doom."It will, indeed. exact method of divisionabsolute accuracy is not there.Here is ['CB, a two-inch line (Fig. 2). WORKSHOP CALCULATIONS You trisect it by marking off three equal divisions on a line at an angle and by drawing TABLES AND FORMUL/E parallels.And Sir Oliver Lodge declared Eighth Edition that your measurement of the length of each by F. J. CAMM thirdcannotbeexpressedwithinfinite A' handbook dealing with methods of calcula- accuracy in figures ;for figures go by jerks,, tion, solution to workshop problems, and the by stops, whereas a line is continuous." No rules and formula necessary in various work- measurement of length," ,hesaid, " could shop processes.It contains all the information X0000Y ever be expressed asa whole number of a mechanic normally requires. Fig. 1.-Diagrams illustratingthe probleminches, nor yet as a whole number plus a From all booksellers, 6/- net, of circles and circumferences. by post 6/6 from the publisher, definite fraction of an inch."You may get GEORGE NEWNES, LTD. (Book Dept.), constrains us to be content with approximation.accuracy to two places of decimals you are Tower House, Southampton Street, W.C.2. The inadequacy is well brought out in this, atskilledfar above the ordinary if' you get April, 1948 NEWNES PRACTICAL MECHANICS 227 Makinga" DesiAnoAraph Y Y Smooth surfaced Lead weights reta,ned Details of a Novel and Instructive Appliance paper -pinned to by nut and bolt. large wheel. for Producing Harmonographic Designs __----G/asspen. d By W. J.C. Flexible cord Adjustable arms made from motor -cycle THE appliance shown in the accompany- spokes ing illustrations is capable of drawing an infinite number of designs, and can be constructed with odd scraps of material usually to be found in any amateur's scrap - box. For materials include part of a pack- ing case, three motor -cycle spokes, a piece of broken car hinge, a few screws, and ter- minals from old electrical apparatus. Details of Construction Jockey arm The base, as shown in Fig.2,is made pivot. fromthe endofthepackingcase,and measures ttin. by 9in.Mounted on it are Clamping screw the large grooved wheel A, to which the Jockey pulley. paper for the design is fixed with drawing pins, and the two smaller wheels B and C. These are made with a double thickness of Fig. 1.-General c view of the designo- it" Spring adjuster graph showing how Cord the pattern is traced on the paper.

thethinsides 'ofthe shaped out 'ofa small piece of brass and packing case glued to-drilled to take the glass pen or pencil which 3" gether, with the grainis clamped in position by means of a brass atrightangles. A milled -head screw. One end of the pen- handle, shaped from aholder is filed to fit into a slot in the block 4 strip of sheet brass fin. d " and is soldered in place, which is also Jockey arm wide and On. long, isdrilled to take the ends of the double arm. pivot. attached to wheel B, aThe part D is made from hardwood, and is small knob being fitted,slotted, as shown in Fig. 3, to take a clamp- Offset as shown in Fig. r. Iting screw.A shaped block E is glued and shouldbenotedthatscrewed to one end, and is provided with a wheel Aismounted small screw -eye in which the end of the rod Jockey pulley lin. off centre, as indi-" b " slides freely. cated in Fig. 2.Wheel (Continued on page 232) C hasanumberof Spring adjuster smalldiameter holes drilled partly through at Clamping varying distances from screw the centre of the wheel. The pointed end of the rod " b " engages in one of these holes when the 4 - applianceisoperated. Each of the three wheels should be provided with a thin metal or wooden 7-Ho/es 76' deep Y4 centres washertoraise them J-74 slightly above the sur- Fig.2.-Planofthedesignograph showingthelayout of theface of the baseboard in Locking handle various parts. order to eliminate un- for necessary friction. -Dia 0.0 suit Adjustable Arms glass pen. The adjustable arms (see Fig. t) are made Lead weights from cycle spokes, the brass block " a " being drilled and fitted with a clamping screw for the rod " b," which is bent at right angles at one end, and pointed, as shown, to drop into one of the holes in wheel C, as already men- Rods 7 tioned.The block a is also drilled to take long a clamping screw for the bridge piece and double arm which carries the pencil or glass pen.An exploded view giving detailsof this fitmentis given in Fig.3. In Fig. 4 details of the weighted penholder fitment are given, the centre brass part " d " being drilled to take a bolt for clamping the two leadblocksinposition. TheseFig. 3.-Exploded view Fig. 4.-Details blocksareprovidedtoensurea suitableof clamping screw and of the weightedpressure being maintained of the pen orblock, and details of slot- penholder. pencil point on the paper. The penholder isted hardwood fitment. 228 NEWNES PRACTICAL MECHANICS April, 1948 Studies in Electricity and Magnetism -2

Ohm's Law : Voltage : Potentials to "Earth" The BLv Formula : Alternating E.M.F. HOW would you measure theinternal By H. REES, A.M.I.E.E. If V = n times v = nV, where n is some resistance of :(a) a voltmeter, (b) an *convenient round number such as to or too, accumulator cell ? (Continued from page 91, December issue). I choose these laboratory experiments for n -- discussion because they embody and extend1.0 volt across r causes the terminal voltage It may be interesting to note that this is important principles touched upon in the firstto fall by r.o volt.If you fully grasp thethe formula for finding the resistance of an article. But while you are thinking aboutimport of the question, you will see there is aammeter shunt, if R = the resistance of the them, I want to say a bit more about " voltage -little more to it than arithmetic. ammeter.Unless a decade box is available, drop."I want you to recall something which The cellstillgenerates1.5volts, andit will not be easy to get v = 1 / toV, etc., for Isaid regarding potential -difference(p.d.)everything looks as if the I .0 volt across r isthe present test.But note one way which being. ofopposite sign " to. the e.m.f. in a indirectopposition-actinglikea" backdispenses with formula or calculations :if circuit.. e.m.f.", We have1.5volts opposed byin 6c we insert an R which reduces the reading If you are interested in radio technical1.0 volt, hence the effective e.m.f.in theto half (v = IV), X = R. problems, you will know there has been a greatrest of the circuit becomes 0.5 volt.It is Alternatively, if R represents the known deal of arguing in the correspoddence columnsa case of action and reaction being equalresistance of a voltmeter, any other unknown of various journals about this question of theand opposite.Something like a " twistofresistance of comparable value can be found. " signs "ofpotentialsinvalvecircuits, The formula then becomes : . -..----- 0.5 v-.1 equivalent circuits, etc. I I I V We shall not enter into that controversy I -m.5 V--.-I 1 1 I X = R -1) = R(n- I).(Why ?) i -7- /-F0r V -.1-- /.5V here, btu much of it has to do with this 1 I fundamental fact that e.m.f. and p.d. are things / Ohm 1 0-'\AA.A. 1----0 Simple Voltage -balance of opposite §jgns. r 4 - The second measurement (b) asked for in our question is of interest because it makes How are " Volts" Lost ? use of voltage-balance-a " null " indication. Suppose 5 volts are dropped in a wire or (a) (b) What is the simplest way of measuring cable.If the e.m.f.at the supply end is the internal resistance of an accumulator ? zoo volts, that at the far end of the line willFig.5 (b).-Showing how internal " drop"Again, one obvious way is to load with a be 200 -5 =195 volts. in a cell is of opposite sign to the e.m.f., andvariable resistance R, Fig. 7a, with ammeter Elementary arithmetic.But why do we thus subtracts from the volts available. A and voltmeter V in the circuit, and observe treat " drop " as negative?Is it just because how much the terminal volts fall from no-load the minus sign stands for arithmetical sub-language is required to describe it : if in anyto full loadIf v denotes this fall, Internal traction ?Five volts are " lost," thereforecircuit element, volts arelost, there mustResistance = v/I. they are a " minus quantity."Or is therebeapotential -differenceof that amount The method now to be considered measures some other meaning ? acting against the applied e.m.f. (Considerv direct, by employing two cells(or two How are " volts 'lost ?Do they vanishthe + and - signs across r (Fig. 5b). Theybatteries of equal e.m.f.'s), inserting a milli - into thin air, or are they changed into heatare opposite to the e.m.f.). voltmeterbetween them(Fig.7b),and in the wire ? So,itseems,thenegativesignhasconnecting the load and ammeter, as before, Electrical energy reappears as heat, the ratea meaning quite apart from its use in denoting of expenditure in joules per second, being,an arithmeticalsubtraction. Watts = Volts x Amperes =Power. But that If a wheelbarrow or a train " reacts " with hardly explains matters.Force, or pressure,a force equal to the applied force, how do is generally lost because it encounters somethey move, etc. ? If the voltage -drop in a "equal and opposite force. resistancegives -risetoanelectricforce Is there such a counter -force in a resistance ?exactly equal and opposite to the voltage Electrically,are we entitledtopostulateapplied, how do electrons move ? anything in the nature of a back e.m.f. in a I will leave you to think about it for the (a) (b) resistance ? present. r- V Measuring Resistances with Voltmeter One obvious way of finding the resistance of a voltmeter is to apply a constant voltage, (C.) whose value will be indicated, and measure the currentiwith a milliammeter mA. in series, Fig. 6a.R = VI, or = Voltmeter Reading/Milliamp. Reading xz,000. To Primary be exact, we should subtract the resistance of A.C. Mean the milliammeter. 1. v But if you have convenient values of known (a) (b) (c) resistances,thereisaneater method not T requiring two instruments. The known valuesFig. 7.-How " voltage -balance" is made use Fig. 6.-Ways of measuring the resistance of ashould be a few hundreds or few thousandof for measuring the internal resistance of an Voltmeter. ohms each, depending on the resistance ofaccumulator(b).Comparewiththemore Action and Reaction the voltmeter. complicated -looking connections (c) for " back- First, connect the voltmeter across a batteryto-back " regulation test on A.C. transformers. Let us take a concrete problem. (Fig.6b), without any resistance in series. The one we started . with would do, butLet the reading be V volts.Repeat theto the cell whose resistance is to be measured. perhaps a simple cell generating an e.m.f.measurement with the known R in seriesThe current taken need not be anything so of 1.5 volts, and having an internal resistance(Fig. 6c) the reading will fall to some lowerlarge (as in Fig. 7a)-if the milli -voltmeter is oft ohm (Fig. 5a) will be more to the point. sensitive enough, quitea small amperage thevalue such as v volts owing to the drop in R The e.m.f.actsoutwards, towards Then : will do. + terminal, or away from the-terminal. Resistance of voltmeter, At first,thee.m.f.'swill be equal (on That is, by definition, the " positive direction" no-load), or will equalise themselves in a If we connected across the of an e.m.f. X =Rx_v while, giving initial zero reading in the mV. terminals a voltmeter which took no current, v -v- _ Upon taking current, the comparatively high it would register exactly1.5 volts - the \ resistance of mV will prevent the second cell total e.m.f. generated. supplying any appreciable proportion of the But if we connected a resistance R taking See if you can derive this formula fromtotal amperes.This cell is simply used to ampere (Fig. 5b), the terminal p.d. wouldfirst principles. Referring to Fig. 6c, askgive voltage -balance to start with. at once fall to 0.5 volts. yourself these.questions : What is the voltage - When on load the internal drop of volts We might ask : Where is the other 1.o volt ?dropped across R ?What is the " drop "will make the terminal voltages unequal, the It is across the internal resistance r of course.across the voltmeter ?What is the current,difference v being indicated direct by the But that is not quite the point.cX7e have ai, in the circuit ?Hence form an expressionmilli -voltmeter - v,ofcourse,being the physicalfacttoexplain, namely, how thefor X. drop. April, 1948 NEWNES PRACTICAL MECHANICS 229 Asbefore,theinternalresistance =v I,coil.Show the directions of the inducedinsulation.Here, too, we have the explana- vbeinginvolts. InA.C.transformere.m.f.in the second coil.What effect,iftion of the 7,000 to 8,000 volts induced in the testingsimilarprinciplesareused. Theany, would result from short-circuiting thesecondary windings of car ignition coils (and secondaries are connected up in oppositionsecond coil ? magnetos) when acontact -breaker rapidly inthesame way(Fig.7c). Herethe The armature of a small motor runs veryinterrupts a primary current derived from a voltages are usually large, and a voltmeter Vfreely and takes some little time to come to 2 -volt battery. (low -reading type) registers the impedance -rest when the power is switched -off.Show drop in the loaded transformer T1, froman easy electrical method of bringing it toThe Inductive " Time Constant " which the percentage drop from no load torest rapidly, explaining what takes place. I would like to discuss the curve given in full load may be calculated.A number of Iwill comment on the questions in myFig. 9b in some detail, because itexhibits a readings are usually taken at different loadsnext article. special " law " (Helmholtz's law). and acurve plotted showing overallper- If the -reader cares to plot this curveon centage regulation. Self-induction squared paper, the set of values given in the The self-induced e.m.f. in a coil when theaccompanying table have been worked from Pogendorff's Method of Measuring e.m.f.currentisstarted or stoppedisa subjectexponentialtables.These values assume a Mention of voltage -balance reminds onehaving wide practical implications. time constant of I.0 seconds, meaning that i of all sorts of interesting applications.There In another article on Dynamo and Motorwill grow to approximately 0.61 in I second, is one more experiment which is worth notingProblems,Ihave mentioned, for instance,as indicated at point P. here. the risks of insulation breakdowns in opening Supposing the final steady value (I) to be highly inductive fieldcircuits.Again, the ampere, the figures in the right-hand column current in every inductive circuit takes timeof the table will then stand for the current to grow to its full value-a fact which accountsvalues reached at instants of 0.s, 0.2, 0.4 for an alternating current in a pure inductanceseconds, etc.Alternatively, if t = so amperes, lagging a quarter -cycle behind the voltage.the values in the right-hand column can he Also this is a factor which must be taken intoread as I, 1.8, 3.3 ampereS, etc.It is interest- account in designing precision devices suching to note that a current ofI will be reached as high-speed relays. in about 0.7 seconds-not in 0.5 seconds. It may be regarded as another instance of More precisely, point P in Fig. 9b corresponds Lenz's law.A self-induced e.m.f.(whichto a time -interval during which i will grow does not itself cause a " current ") tends toto a value of 0.6321 (63.2 per cent. of the. stop dr delay the motion producing it-thefinal value).It is shown ass. sec. in this motion of electrons, cm& the supply current.instance ;in Sc,itis so secs., but would Fig. 8.-Another measurement making use of Thus, in Fig. 9 a, on closing the switch S,become soo secs. if R was reduced to I ohm. voltage -balance.Calibrating an ordinary Metrethe current grows rather slowly to its normal Oddly enough, the inductive time -constant scale (not shown)to read " Volts." value, somewhat as indicated by the curve inis given by the ratio, Inductance i Resistance Fig. 9b. Magneticlines coming into(L IR) =Henries/Ohms.Thus, L /R =a time It is a method of accurately measuring theexistence, " cut " the turns of the coil, induc-in seconds-the time the current will take to e.m.f. of a cell without a voltmeter. ing a back e.m.f. E whose positive directiongrow to 63.2 per cent. of its final value.To In Fig.8,aslide -wire potentiometerisis opposite to the + and - of the supplytake another example :a coil of 48H. having connected to a steady voltage source, such as(indicated by dotted arrow s). aresistanceof6oohniswillhavea a 2 -volt accumulator. An additional resistance The effect can be seen in the inductivetime -constant of L12-48 60=0.8 sec. R being put in circuit to limit the currentfield circuits of large generators, transformers, There we will leave this subject, but laws and thus prevent overheating the slide -wire s.etc.With a D.C. supply, the pointer of anofelectro-magneticinductionwhich we The totalfall of potential along swill beammeter creeps up,fairlyrapidlyatfirststarted considering inthe previous article 2 volts, less the volts dropped in R, the end(steep portion of the curve, Fig. 9b), then atmust be developed so as to give more precise B being +to A.A metre scale is fixed along s.successivelyslowerrates.Several secondsdefinitions of quantities like " inductance." First, a standard cell SC (or one whosemay elapse before a steady value is reached. e.m.f. is accurately known) is switched through For example, in the inductive circuit shown" Loop " or Coil in Magnetic Field galvanometer G to the slider which makesin Fig. 9e,i will take so seconds to grow to a Some space has already been devoted to contactwiths.Anys'ensitivemeasuringvalue such as is shown by point P in Fig. 9b-the "BLv " formula for the electro-motive instrumentcouldbeusedas " galvo, force induced in a single conductor moving or preferably centre-zero-but no measurementabout 6o per cent. (0.6) of the steady value I. of voltage or current is required, only zero Final Steady Current R=/0 Ohms balance. I Suppose the known e.m.f. of SC is LosFig. 9.-On closing switch volts.The slider is moved along the wire and carefully adjusted until G reads zero.S, current in the inductive Suppose this occurs at 8o ems. on the metrecircuit grows in the manner shown in (b),where I= Approve. 04/ scale.Then the fall of potential along 8oViR= thefinal steady ems.isexactly equal to the e.m.f. of SC,value given by Ohm's Law. Los volts,but of opposite sign-current 0 In (c),the current wouldBack E.M.F. On %2 cannot flow either way through G. Therefore, Time (t)Seconds the metre scale can be calibrated in volts :take so secs. to reach theClosing And 8o cms. = I.os volts, hence s cm. - Los /Flo -- value i =0.61. Opening S. 0.013 volts. (a) (b) (c) The cell of unknown e.m.f. X isnext switched into circuit and the slider againIf the resistance could be made as low asrevolving in a magnetic field, and we saw adjusted for null deflection.Suppose balanceI.0 ohm, the time would bet,minutes.that it comes down to the fundamental law : is obtained at 90 cms.The e.m.f. X =0.0 s3 xWe shall say a little more about these time - Induced e.m.f.(electromagneticunits)=.- 90 = 1.17 volts. intervals presently. Total number of lines cutin I second. The and - signs placed against the On opening theswitch S(Fig. 9a),the Sinces -voltisthe e.m.f. induced inA cells and slide -wire will show why the galvano-fieldwillsuddenlycollapse,an immenseconductorcutting100,000,000(sob)lines meter gives no reading. For example atnumber of " magnetic lines " cutting hundredsevery second, the first balance point, there is a potentialor thousands of turns in a small fraction of a Total Lines cut per sec. drop of Los volts in s-this drop being duesecond-in snore technical. terms, we get an E (in volts) - to the steady current flowing from the accumu-extreniely high rate of change of " flux -linkages." so' lator, and of sign - from right to left, asIn consequence, an e.m.f. will be induced It was pointed out, also, that the BLv shown.Against it, the Los volts from SCacting in the direction of the second dottedequation gives the maximum value of the acts as a back e.m.f., hence no current canarrow 2, i.e., in the same direction as the supplyinduced voltage.That is to say, the formula flow either way through G. voltage,sotendingtokeepthecurrentasitstands refers to a conductor moving " going," or to maintain itat 'steady valueatright -anglestothefield.If we take More on Lenz's Law when itisrapidly decreasing.Probably aaccount of the fact that, when revolving, the As exercises on the direction of inducedlong drawn-out arc will occur at the switchmotion is at right -angles to the lines at only current being such as to " tend to stop "contacts.Theself-inductionthuspartlytwo points, we have to introduce " Sin 0 the motion producing it, readers are inviteddelays the rate of decay-the spark at the(or " Cos 0," depending on what is considered to answer the following questions : switch tends to prolong the current flow. the initial position). ' Two identical coils wound in the same Still, the rate of interruption may be large The formula then gives the instantaneous direction and having similar terminal connec-enough at " break " to self -induce an e.m.f.value of an alternating e.m.f., Em., i.e., the tions are placed on an iron core. A make -and -many times the normal supply voltage, thusvalue at any instant in a cycleis, e=Em break device starts and stops a current in onecausing breakdown of weak partsof thesin0. 230 NEWNES PRACTICAL MECHANICS April, 1948

Consider, next,a" loop " or asingleis because N/t is an average rate of change.the e.m.f.) in terms of rate of change of turn of wire revolvinginthefield -for A numerical example will show how bothlinkages, and the maximum or r.m.s. value example,single -turn armaturecoils.Themethods may be applied to simple designis asked for, ,the answer must be multiplied maximum voltage generated may be calculatedproblems. by Lir or 1.57. by BLv x to8, treating eachactive side of Alternatively,the BLv formula can be the loop as a conductor of length L cms.Two Ways of Calculating Induced E.M.F.appliedtofindthemaximume.m.f., As there are two " sides," the formula must Let us work the following problem for amultiplying by 0.707 to find what a voltmeter be x2.The velocity v=2 rn ems. per sec.,coil revolving in a two -pole field (Figto),would read, and by 1/1.57=0.637if the where r is the radius of rotation. average value is asked for. But we want to approach this question ofthe data being : More care should be exercised to take induction in loops and coils from a slightly Turns = too account of such conversions when transposing different angle.While, as before mentioned, Active Length L = to cms. it is often convenient to regard each active Radius r =2.5 CMS. Total Flux (N) Area A =5o sq. cms. Fig. IL -An iron -cored side as a conductor cutting lines of force, Flux Density B = to,000 lines per sq. cm.chokeortransformer the principle of " cutting " becomes difficult well illustrates linkage to apply to other cases such as circular coifs. Speed --3,000 r.p.m. =5o r.p.s. The total flux N =B x A-= x so=5 ;/. 105of N lines with T turns. Turns Our object is not so much to " derive The flux is varying at (T) fern:1111m "asto grasp or soo,000 lines a wider principle Circumferential Velocity v-=2or x 2.5 x 50= thealternatingfre- applicable to self-induction, a.c. transformers, quency of the supply. etc., where coils are themselves stationary 25071 CMS. per sec. whilstthemagneticfieldisvaryingor Therefore, using BLv : alternating. Max. e.m.f. (two sides ofI turn) =Em=to find the turns, flux, or speed, given the This wider principle may be stated as to'to x 2507r / 2-1.57 volts. other quantities. follows :the induced e.m.f. in a coil of T 108 Transformers Thisisthe maximum For transformer windings (Fig.t 1), the (peak) value of an alternat-N,'t method is extremely easy to apply. ing e.m.f. of frequency 5o Here, we have a stationary coil of T turns, cycles per sec. Since thereand'a flux N in the core which8is varying at aretoo turns, thetotalthe supply frequency, so cyclespersec. peak voltage if a pair ofThe self-induction effect will be exactly the sliprings were fitted wouldsame as if the coil was revolved 5o r.p.s. be 1.57 x too =157 V. in a two -pole field, as above. Hence ana.c.voltmeter Thus, N varies between zero and maximum would indicate the R.M.S.every-cycle = I /4f.secs.(or 200th sec. Value =0.707x 157 =forf =50 cycles)Working the same as to v. above : Next, let us reason the Average induced e.m.f. =4.fNT x 108. 1L CMS .10 R.M.S. induced e.m.f.=4.4.4..fNT x 108= Zero Linkage. Max Linkage same problem in terms of 222.fNT x 108; for f =5o cis. Max Rate Of Zero Rate Of flux linkages. Now, seeif you can do the following Change And Max Change And Zero During each1 -revolu-type of problem :How many turns are E.M.F. E M.F Area A tion the flux threading therequired on the primary of a transformer to coil willchange from owork off a supply at 25o volts., so cycles, if to 5 x to' lines (or the otherthe core has a oross-section of 20 sq. ems., (a) (b) (c) and the flux density is not to exceed 8,000 way about) -The time tlines per sq. cm. ? Fig.io.-Explaining a generatorinterms of " flux -linkage."of a+-rev. = t /moth sec., Though the flux " linking," or "threading " the loop is maximumso that, TABLE I in (c), the induced e.m.f. is zero because the rate of change of flux Values for plotting a curve of growth of is zero in this position. Average rate of change currentinaninductivecircuitwhose of flux =Nit = time -constant L/R =I second. turns is numerically the same as the rate of 5 x :o5 Jos lines per sec. change of flux -linkages. 1/200 - Time (t)in secs.Current at instants t, x Turns Average Induced e.m.f. -Flux Or, average rate of change of flux -turns --- from instant of expressed as a time to8 x too. closing the switch. decimal fraction of NT 8x r08o5 = r - (e.m.u.'s). Average induced e.m.f. -10 the final steady 1 volts.oo current I. NT The maximum as found above is 157 volts, or E (in volts)=- x 108, the R.M.S. value Ito volts, and this the o 0 t being a time interval in secs., during whichratio)R.M. S . /Average = oo = r. r,the 0.1 sec. 0.1 the flux varies between o and the value N.more exact figure (the form factor) for a sine - 0.2 0.18 (The symbol N stands for total flux -BA,wave being 1.I 1. 0.4 0.33 where B =lines per sq. cm. (flux density), Also for a sine -wave alternating e.m.f. or o.6 0.45 and A the area traversed by the flux. current :max.value/averagevalue -1.57 o.8 0.55 1.0 Observe, we must be careful tostate,which is seen to be the case above, i.e., 53 0.632 flux -linkages -flux times turns.One line of1.57 volts/too volts =1.57. 2.0,, 0.865 force linking with too turns will develop a Examination students should particularly 3.0 3, 0.95 hundred times the e.m.f. induced in a singlenote these facts.If given a problem to work 4.0 3/ 0.98 turn.Hencer -voltwillbethee.m.f.the induced e.m.f. (or turns, or flux, given (To be continued.) induced in a coil whose total" linkage " is changing at a rate equivalent to to' flux turns per sec. A rate of change of 108 linkages per sec. FOR ENGINEERS may be :too million lines linked with one ---!----, turn (changing between zero and maximum Screw Thread Tables, 5/-, by post S13. Wire and Wire Gauges(VestPocket in one second) ;to million lines linked with Book), 316, by post 319. to turns ;tmillion lines linked with too Refresher CourseinMathematics,816, turns ;and so forth.Also, the time need by post 91-. Screw Thread Manual, 61-, by post 616. not be Isec.A " rate of change " of re Gears and Gear Cutting,61-, by post 616. lines per sec., for instance, may result from Newnes' Engineer's Reference Book, 421-, million lines varying in r/iooth sec., since Workshop Calculations, Tables and by post 431-. N/t ---to8/rol= to8 lines per sec. Formula, 61-, by post 616. Practical Mechanics' Handbook, 1216, by In other words :a flux -change oft million Engineer's Manual, 1016, by post Ill-. post 131-. lines in rizooth sec. wilt have precisely the same induction effect in a coil of T turns as PlantEngineer's Pocket Book,6/-,by too million lines changing in i sec. post 616. Published by Another point to noteisthat formula; Newnes' Metric and Decimal Tables, 316, GEORGE NEW NEB,LTD., TOW ER HOUSE, which make use of N/t (Flux/time) give the by post 319. SOUTHAMPTON STREET, STRAND, W.C.2 average,not the maximum induced e.m.f.- the BLv formula gave the maximum.This April, 1948 NEWNES PRACTICAL MECHANICS 231 The Schoolboys' OwnExhibition Afterthoughts On This Interesting.Show By THE MARQUIS OF DONEGAL!.

THIS Exhibition was held at the Newpresent King-; the Horticultural Hall, Westminster.IDuke of Glouces- pursued my usual technique of exhi-terandthelate bition reviewing by making aquick ten-Duke of Kent. The minute tour of the whole show and thenpresent King was going meticulously through the A to Z gamutin R.A.F. uniform of individual stands. and the Duke of After my ten-minute run-around it wasKent inthe uni- obvious what a great improvement had beenform of my Home made over the1947Exhibition. Why?Guard and Army Because there seemed to be so many moreCadet Force regi- stands calculated to be of special interest toment,the Royal schoolboys. West Kent. As you came in .the doorsyou walked Another fascina- straight intoalarge stand displaying andting display in the selling cigarette cards.In spite of the pres-War Office section sure of younger enthusiasts,I learned that was a complete the first set of cigarette cards was of actresses model of the between 1892 and 1893.These are worthGrandFinaleat

A fine model railway layout, arranged by the British Railways, and shown at the Schoolboys' Own Exhibition.

gadget at length in another article,Iwill leave it at that.British Railways and Lon- don Transport showed an extensive No. "o" gauge railway system. We next come to the " Daily Mail's " exhibit, which filledthe whole of the so- called dais.It was got up as a sports' arena, wheredisplaysby well-known champions were given in football, cricket, fencing, box- ing,tennis,table -tennisandswimming. Where a display was impossible, as obviously in the case of golf, the various experts were interviewed by sports' reporters and gave talks. Competition Arena One of the most interesting sections,I thought, was the Competition Arena. There Watching a machine which packs120 razor blades a minute on the stand at were a numberofcompetitions,which the Exhibition. includedmodel -making ;dressed -dollfor schoolgirlsunder 18 ; artcompetitions 5os. each to -day.Another valuable set is athe Aldershot Tattoo; and finally, with thedivided between under 14 and 14 to 18 years military series by Wills which would costbackground of Edinburgh Castle, a parade ofof age ; a stamp competition and a construc- you around £35 a set.Apparently the urgethe Scots Greys and the Black Watch. Captaintional set competition organised by Castos, for collecting cigarette cards isstill alive inLightbody spent a month painting each piper.Ltd. the 1948 adolescent breast, even though there Then we passed to the West London Road On the day that I went a competition in are no modern ones to be collected.In fact,Safety Committee's exhibit which showed thecardboard -modelling was in progress, and one it might interest a friend of mine who hasE.R.A. racing car driven by Reg. Parnell.boy was well on his way to completing an 25,000 to know that his potential market isLater we are to see John Cobb's record -astoundingly realistic model of a London bus as firm as ever.He happens to be one ofbreakingRailton-Mobil-Special. Thiscarwhen his time -limit tragically ran out. Britain's most eminent surgeons. broketheworld'sland -speedrecordon Towards the end of our round we find Bonneville Salt Flats a few days before thethe Army Cadet Force display.This was an War Office Display outbreak of the war ataspeed of 369.7extraordinarily good show. The exhibits, Next we passed to the War Office displaym.p.h.It it possible that this car may reachwhich were made inone ofthe Army of model soldiers. There was aBailey 400 m.p.h. at the Utah Centennial Celebra-Apprentice Schools, ranged from Elizabethan Bridge and a complete model of the Troop-tions this summer over the rz-mile course. days to 1948.The controlling of working ing of the Colour.Apart from the mass of The Royal Society for the Prevention ofmodels by cathode-ray and photographic -cell troopers and officers in their pre-war splen-Accidents were there with their driving testdrew a fascinated audience.They had an dour, there were special models of Kingconsisting of an immobile car that " drives "extensivecollectionofGermanmedals, George V ; the Prince of Wales, as.the Dukealong a road that unrolls beforeitona together with Hitler's will and his private of Windsor then was; the Duke of York, our screen. As I have already described this telephone exchange. 232 NEWNES PRACTICAL MECHANICS April, 1948 R.A.F. Exhibit The same applied to the schoolboys whorequired a pull of just under one ounce.I The R.A.F. showed, among many otherqueued up to make recordings for sending ascan only hope 'that my martyrdom was of things, a model of an R.A.F. Station com-greetings to their friends. I know of nosome benefit to the march of science! plete with hangars and aircraft.Next to it,otherorganisation,excepttheYorkshire I was glad to notice that our childhood a complete model of an Operations' RoomGramophone Library, who ran this exhibit,friend, the Ingersoll, is back with us.To be during the war. that has a postal gramophone record librarysure, he has gone from his traditional five After this we came to a fluent gentleman service. Another feature was a series ofbob for the cheapest model to 43s.; and he who was demonstrating an adhesive pasterecords ofthedialec,ts now usedinthe issoon to have his younger brother, the which, under his expert demonstration, wouldBritish Isles. Ingersoll wrist -watch, asa companion. A apparently stick anything more solidly than watch is quite enough to interest a school- before it was broken. Before a gogglingRazor -blade Wrapping Machine boy, but this stand also provided the well- audience of youngsters from eight to 8o he Next we came to Gillette.They showedknown conjurer, Mr.- ErnestSewell, who smashedmirrors,teacups,furniture,and a machine that wraps the razor blades.Thisvisitsschoolsallover thecountry.The stuck them instantaneously together againmachine, although slowed down for purposespresent Ingersoll is, of course, British work- with a paste resembling gruel that he hadof demonstration at the Exhibition, normallymanship. brewed over a low flame. Having mendedwraps up 15o blades a minute. There were several things thatIdidn't these sundry articles, he proceeded immedi- In t944 I wrote an article on Gillette andknow. before going to the Schoolboys' Own ately to smash them again, and succeeded indiscovered that not only was the Great WestExhibition: demonstratingthatwherever elsethese Road factory turning out a million and a half (1) That the Gas Light and Coke Com- articles that he flung about like a poltergeistbladesaday,butthat a distinguishedpany is the largest gas undertaking in the broke at the second effort, his joint remainedmember of the firm, Mr. J. F. Kayser,was anworld. intact.Immeasurably impressed, I investedunsung hero in the cause of hirsute human- (2) That Arthur Rank's cinema clubs for a shilling or so, but it seems that I have not ity. In fact, he lent out portions of hischildren between the ages of seven and four- acquired the proper magic passes or abra-face-and for allI know may still do so-teen have a membership of nearly halfa cadabra, as I have so far not succeeded inas an experimental guinea-pig towards themillion. sticking anything with it. improvement of shaving methods. For this (3) That you can get t3 stamps with. Hit- Recording Studio purpose Mr. Kayser had a small tattoo markler's head on for a shilling. One of the most popular exhibits was theabout an inch from the right-hand corner of (4) That there was a car in the world that recording studio of a Leeds company. Sincehis mouth.This was to make sure that thecould do 15o m.p.h. on its lowest gear. I have had a recording machine in my housemicro -photographs of his growth of beard So, in conclusion, I repeat that there was I have been astounded at the number of myunder varying conditions would always showplenty this year to interest the schoolboy, in friends-some of them well-known publicexactly the same spot. particular, and grown-ups, in general.The speakers-who have never taken the trouble During my visit to the Gillette factory theyorganisers are to becongrAtulated, andI to hear what their own voice sounds like.put my head through a hole in an operat-hope that they will pursue their efforts and But, given the opportunity,Ihave nevering table.The result of this highly scientificdelight the youth of 1949 even more than found one that did not practically insist onexperiment was thatit was found that tothey succeededin doingin1948'smost making a record immediately. detach one of my hairs from the epidermispraiseworthy and well -thought-out display.

mural reproduction of a Saxon Scratch Dial from Kirkdale Church in Yorkshire. Controlling Electric Light fromaBedEarly Workshops The workshops of the early clockmakers were also shown by means of enlarged prints, TT is always desirable to be able to control just screwed on the end of the tumblerand examples of mechanical clocks by the the ceiling light from the bedside, more withoutdieinghasproved an admirableworld renowned British craftsmen formed a especially when a bedside lamp isnot insolution in these cases. The cords can'background to the old craftsman working at use,but in some casesitisnot always terminateatthe bed ina loop, or ina his bench. convenient to do thiselectrically.A very handle,asshown. In severalof these simple and efficient manner in which thisattachmentsIhave made,Ihavepassed Early foliot or cross bar escapements were can be done otherwise is as shown in the thecordsthroughplasticsheathing andreplaced by recoil escapements and pendu- sketch. a lums.One of the earliest known types of terminated in loop. With thewhole doniestic clock was shown by a fine example The clip G andbracket F whichis fitting painted in -a suitable colour ...it formsof a weight driven Gothic alarm and striking riveted to the clip were made of light gauge averyusefuladditiontothebedroom. aluminium, and tightened to switch body byWhen entering or leaving the room ordin-clock made about AM. 1500. means of a 4 B.A. screw and nut. The sketcharily the switchisoperated in the usual The discovery ofthe mainspringasa shows the arrangement of the cords,i.e.,manner.-W. R. Knapp. motive force for timekeeping is generally attri- one under and buted to Peter Henlein and some of his first the other over efforts were made about 151o. Other ex- the tumbler. amples of this section included: The Pageant of the Hours Two beautiful modelsofspring driven The cords are tableclocksofabout1565. Inthese knottedat A "THE Pageant of the Hours " presentedexamples both dumb -bell and wheel types and B outside by Smiths English Clocks Limited, of balance were used and in one instance theclip,pass atthe " Daily Mail Ideal Home "regulation was effected by short lengths of round the Exhibition, held at Olympia, March 2nd topig bristle. tumbler,25th, was an exhibit illustrating the evolu- Another interesting model was a wonder- through thetion of man's efforts at time measurement ful astronomical clock with twelve dials hav- shoe eyeletsat through the centuries.We believe that thising complete calendar mechanism showing C and D, andis the first time that such a presentation has signs of the Zodiac, Rising and Setting of converge to an-been made public in this country. From the Sun, Phases of the Moon, and several other eyeletin purely the intellectual interest in clocks and other interesting features. the bracketat time measuring devices.from 1500 B.c. to the E,whichen- modern " Sectric " models ofto -daythis ables the switchexhibit proved extremely interesting. MAKING A DESIGNOGRAPH tobe' worked On entry one saw prints of period rooms (Continued from page 227) from anacute illustrating how the clock has been estab-Jockey Pulley angle, if neces-lished in the home and formed an integral A brass jockey pulley isfitted, as shown, sary. Some types part in the regulated day of each individual.to take up the slack in the driving belt which of switches have From the period rooms the visitor was may consist of blind cord or similar material. a square section taken in the form of a diorama from theAn adjustable coiled spring is provided to tumble r,earliest known method of time measurement maintain the necessary pressure for keeping inwhich case as illustrated by the figure of primeval man the belt taut.- the cord wouldstudying the shadow cast from his spear by Foursmallrubberfeet,screwedto normally slipthe sun.Included in the section was a cast the underside of the baseboard, complete overtheend, from an Egyptian clepsydra or water clockthe appliance which will produce an un- A simple device for control- but alin.dated from t400 B.C. and early sundials in-limited number of varying designs by simply ling a ceilinglight from a domed nut fromcluding a copy of the hemi-cycle of Berosus altering one or more of the four adjustments ted, and detail of handle.thejunkbox the Chaldean made about 300 B.C., and a provided April, 1948 NEWNES PRACTICAL MECHANICS '233 The Elements of Mechanics and Mechanisms -6 ByF.J. CAMM (All Rights Reserved) Horse-power-Measurement of Force-Unit of Pressure IN estimating the amount of work performed 75 kilogrammetres per second, or 4,500Measurement of Force by Strain or by machines, the foot pound is an incon- kilogrammetres per minute -32,55o ft. lb. Pressure veniently small unit because the number Now there are plenty of examples of a force per minute; or about I- less than a of them would be uncomfortably large in the, 70 acting on a body and failingto produce case of machines of high horse -power. A Britishh.p.,hence" chevaux de75 motion, because of the action of some opposing larger unit has therefore been established, in kilogs," or metric horse -power. force.In this case a strain or pressure results. exactly the same way as long distances are French h.p. x 0.9863 =British h.p. Thus, if a 5 lb. weight is placed on a bench, measured in miles, or furlongs, instead of in British h.p. x 1.014-French h.p. gravity endeavours topullthe weight down- yards or feet.This unit of work is called French i.h.p.=cheval indique. wards, butisprevented by the opposite r horse -power. Now this is an arbitrary unit, action of the bench. A push downwards on the since there is no such thing as a standard We have already seen that forceisthattable and upwards on the weight is the result, horse.It was James Watt, the man who didwhich produces or tries to produce motion.and the pressure is caused by the force of not invent the steam-engine, who introducedForce causes strain or pressure in the bodygravity. this unit of power, or work, and he estimatedon which it acts, and we may therefore say Magnetism provides many examples where that an average horse could raise I lb. 33,000ft.that force causes either motion or pressure. pressure is produced.Since gravity is such or 33,000 lb. ift. in one minute.It is now In the case of forces acting on the samea constant forceitprovides us with the accepted as a standard. massitisapparent that the greater theunit of pressure, and the pressure which When we say that an engine develops 8force acting on the body of a given massgravity produces in a mass of I lb. is the unit horse -power we mean thatit can performthe greater will be the velocity given to theof pressure, or the unit of force as measured 8 x 33,000=264,000 foot lb. of work in onebody.Assume, for example, that a certainby pressure.Any force, therefore, whether minute. The unit is abbreviated to h.p. force imparts a velocity of 'ft. per secondit be gravity, magnetism, cohesion, electricity, It will be noticed that time is introducedin a mass of r lb., twice the force will causeor any other force which acting on, a mass of into this unit, although it does not occur ina velocity of 2ft. per second ;six times the -1b. kept at rest produces the same pressure connection with foot pounds. force, a velocity of 6ft. per second, and soon a r lb. weight is said to have a magnitude James Watt assumed that a horse can travelon. of 1 lb., and this is called the gravitation unit 2a miles per hour fir eight hours a day, Also the longer the time a force acts on theof force. performing the equivalent of dialling a loadbody the greater will be the velocity produced, Suppose we wish to measure the force of 15o lb. out of a shaft by means of a rope.and .if a certain force acting for one secondexerted by a man pulling a barrow. We Thus 2 a miles an hour is z2oft. per minute,produces in a mass of Ilb. a velocity of ift.have only to connect the hook of a spring and at that speed the load of Iso lb. is raisedper second, the same force acting for twobalance with the barrow, and let the man verticallythesamedistance. Thereforeseconds will produce a velocity of 2ft. percommence to pull ituntil the barrow just 300 lb. would be raised i Ion., or 3,000 lb.second. If itcontinued to actfor threebegins to move. The pull in pounds will be raised 1 ift., or 33,000 lb. raised rft. high persecondsit would impart a velocity of 3ft.given by the index fingerof thespring minute.The latteristhe unit of horse-per second. balance.Precisely this method may be used power, i.e., 33,000 lb.raised'ft. high per It is because of this fundamental fact thatto measure the pull of a train.In fact, minute, or 33,000 foot pound per minute.we are enabled to measure force by thedynamometer cars are used on the railway' Electrical equivalent is 746 watts. velocity which it produces. Now let the forcesin this way to measure the drawbar pull of a Horse -power of an electric motor- which we wish to measure act on the samelocomotive. Volts x Amperes masses for the same time, and observe theRelation of Absolute Unit to Gravitation I.H.P.= velocity whichisgiven to each of these Unit 746 masses, taking r lb. as our unit of mass, and We know that the force of gravity acting Horse -power (indicated) of a single cylinderour unitof time one second.In theseon a mass of Ilb. for one second produces steam-engine (single -acting)- circumstances the force which, acting on a PLAN in that mass a velocity of 32ft: per second. I.H.P.-PLAN mass of i lb. per second, produces a velocityBut the absolute unit of force acting on the 33,000 of ift. per second is the unit of force. same mass only produces a velocity of 1ft. where P -mean effective steam pressure in Following this reasoning it is obvious thatper second.That is to say, only 1/32 of the lb. per sq. in. another force acting on a mass of r lb. andgravitationunit. Therefore,a weight or L =Length of stroke in feet producing a velocity of Soft. per second willpressure of ilb. is equal to 32 absolute units A -area of piston in sq. in. be 30 times as great, and will have 3o unitsof force.One absolute unit of force is equal N =number of revolutions per minute.of force. The unit of force produces a velocityto the weight of a oz.In other words, if

Fora double-acting engine the formula is : of 'ft. per second in a mass of Ilb., but ifthe weight of a oz. acts on a mass of I lb. for this force acts on a different mass, say of 2 lb.,one second it will produce a velocity of 'ft. I.H.P. =2PLAN it will impart a different velocity, in this caseper second. 33,000 aft. per second, and a force acting on a mass EnergyBy Horse -power of petrol engines- of ilb. producing inita velocity of loft. is meant the poWer of doing work, per second will produce if it acts on a mass formula :h.p. and work has already been defined as the R.A.C.D'N16.13 of 2 lb. a velocity of loft. per second, on a massproductionof motionagainstresistance. of 4 lb. a velocity of 41t. per second, and so Dendy Marshal formula :h.p. -D2SNR Whenever a body "is moved against some 200,000on.Expressed in another way, the same forceresistance, work is done, and the power which where S -stroke in centimetres acting on different masses produces varyingovercomes the resistance is called energy. D =diameter of cylinder in centimetresvelocities. We have already explained that to measure R -revolutions per minute On multiplying each mass, however, bythe magnitude of any force we have to con- N -number of cylinders its corresponding velocity the product is thesider how many units of work itis capable A.C.U. formula: roo cc. = rh.p. same in each case, and this product measuresof performing.Thus a force that can raise the momentum, so the same force acting for'so lb. to a height of ioft. would Be said to be Metric Horse -power the same time on different masses producesdoing roro= too foot pounds of work. >French h.p.(force de cheval or cheval-,the same momentum. When we know the velocity of a moving vapeur) Summarising, the unitofforceisthatbody and its weight we can quickly find kilogrammetre -I kilogramme (2.205 lb.)which, acting on any mass for unit time (onehow many foot pounds of work the body is raised i metre (3.28 ift.)--7.2346 ft. lb. second), produces in that mass the unit ofperforming, and thisis the measure of its Ikilogrammetre per second =434 ft.lb. momentum. Thisisthe absoluteunitofenergy.

per minute. force. (To be continued) 234 NEWNES PRACTICAL MECHANICS April, 1948

Rack For Too/s In Use MakinAa Watch-repairin Glass Surface Bench Constructional Details of a Useful Appliance for the Amateur Craftsman By M. M. E. PEARSON

-_-,------_' properking gin. deep.General Assembly of the Top _,--_=-_-i-----:_=----- This is to ensure it slid- The actual bench is seen to comprise a base ing easily in use. Suit- (Fig.3) around which there are four side _ -_-',---- =3-----.----1.1 ------' 2 Supports 2 Runners Baseboard To Form Fig. 1.-The completed ex 12's x /7 Square And Screwed To Battens bench,showingthelampshade and supporting column. THE advantages of a portable bench forable divisions for such watch repairing or model engineeringa drawer are a matter work are numerous.Particularly soof individual taste, but during the winter months when such a benchthose shown have may be safely used on apolished table-provedsatisfactoryin hence increased comfort from which betteruse. The divisions in work is likely to result. the front are for The bench to be described is made entirelyfairlylargetools,the from \ tood with the exception of five metalsecond row for tins con- clips, and is easy to construct, involving onlytaining small tools, and one half -lapped joint.The cost to make isthe back row forbits only a few shillings, for it will, in many cases,andpiecesforwhich Lamp Note: The four legs only mean purchasing a square of glass, lamp -there is only 'occasional Column are screwed to the holder and flex, etc. use. mainbattens,as Fig.r shows the bench in its basic form, indicated. on to which other attachments, such as a part cover for the glass to which a small vice or Tool Rack 4 Cl/ps Securing Rack To Bench l8 "Square Fig. 4.-General assembly of underside of bench.

pieces, each of which isr8in. by rlin. by fin.These side members form a frame for retaining the glass, which is prevented from falling out by four lengths of-tin.corner moulding. The moulding can be fastened to the framework by panel pins. The drawer slides in the slots formed by the baseboard, battens and runners.A square of glass is required, and should be slightly under r7in. Sheet Of Glass Base Board square. Underside of Bench The baseboardcanbe made from a number of pieces of woodin.thick held Runner Section Through Drawer Showing The Runner

CMoulding Batten Fig. 3.-Assembly of top side of bench and detail of moulding and under batten.

(6) bench drill may be fittedor perhaps a flap cover fixed to the top surface of the drawer Side view (a) toprovide an auxiliary bench top when assembling a complicated mechanism can be incorporated as the need arises. The Drawer Fig.2shows the details of the drawer, the Assembly Of width of which is r4 in. to the insides of the Handle runners.There is no real need for any other than butt joints, glued and screwed, or even panel pins in the place of screws. The handle of the drawer can be made in two pieces as depicted, finally glued and screwed as are the rest of the pieces which go to make the finished job.It will be noticed that the ,Suggested Divisions Fig.2.-Details of - front df the drawer is rain. deep, the drawer /n Drawer drawerconstruction. April, 1948 NEWNES PRACTICAL MECHANICS 235 framework of the bench by the four clips, whichforpreferenceshouldbei/i6in. thick. The actualtoolholderisin one piece andhas a number of slotsin itto -1 a receive the various tools in use.The holder, being in one piece,stiffensthe body and results in a rigid fitment. Painting the Bench TotSuit To put the finishing touches to the bench, a coat of paint isa necessity.In order to finish this well, all screws and nail holes, etc., must be filled up. A good stopping mixture /7" can be made by mixing powdered chalk (french chalk isexcellent) and some of the Bracket paint to be used on the bench.Mix these two untilastiff smooth pasteis obtained Fig. 5.-Details of hunp sup- and smear over the parts requiring the treat- portingcolumn andbracket ment, leaving a slight surplus as when apply- for the lampholder. ing plastic wood.After this paste has hard- Column ened, smooth with glass-paper, and apply a flat or glossy coat of paint.Rub this down smooth after itis thoroughly dry and apply necessary tohalf lap two pieces ofthe top coat. wood each tin.sq.at approximately Fix an opaque lampshade after wiring the the position shown, taking care that lampholder,neatlyfasteningtheflexto The bench 9" the grain in the wood is near enoughthe side or back of the column. asindicatedinthediagram. Theis then ready for use. together by two battens i8in. x fin. x $in. As lamp bracket fits the the drawer is only tzin. long, the runners yin. part of the need only extend for the'gin., these being column, andisheld glued and screwed to the battens. inpositionbyfour Four legs, which are rain. long, Ilin. wide smallscrews. The at the top, and tin. wide at their base by`tin.diameter holeis ,,gyp lin. thick, can now be fixed to the battens tosuitanordinary and the under edge of the frame, one inch bayonet fitting lamp - from the corners (Fig. 4). holder.Any piece of The lamp column is held securely by two steelorbrassabout support blocksasshown, andisfurther r/16in. thick is quite 4" boa steadied by the two pieces constituting the suitable for t h i tool rack body. bracket. The Tool Rack 4 ClipsTo Secure Lamp Column and Bracket Rack To Bench The illustration, Fig. 5, shows the profile of Therack bod y the lamp column laid out on inch squares. illustrated in Fig. 6 is To prevent alarge section of the column made in twosections Fig. 6.-The tool rack having short grain owing to the curve,itis andsecuredtothe fixing clips.

Fercuson Tractors

ACONSIDERABLE contribution towards the'solution of the world food shortage is being brought about by a revolutionary agri- cultural machine, the Ferguson Tractor, which is being produced in large numbers at the former wartime shadow factory of Standard Motors at Banner Lane, Coventry.The tractor is of lightweight speciallytreatedalloysteels, designed to pull great loads with ease, and has finger-tip depth control, etc.Half the present outputis now being exported tothe eastern hemisphere, and this will increase as Jarge-scale production commences. The tractor company, Harry Ferguson, Ltd., of Coventry, are to send to theUnitedStates tractors worth £5,000,000.The first shipment left recently, and subsequent deliveries will be at the rate of £125,000 worth a week until the orderiscompleted. Itisbelieved that the Americans are prepared to take up to£1 5,000,000 worth of the tractors.Associated with Mr. Ferguson is Sir John Black, managing director of the Standard Motor Co.

Completed Ferguson tractors filling the bays at the Banner Lane factory of Standard Motors. 236 NEWNES PRACTICAL MECHANICS April, 1948 Makinga6in. Astronomical Telescope Reflector

The Methods, Tests and Techniques Employed in the Production of an Astronomical Telescope Mirror. By T.J. MULLIGAN The Foucault Test (Concluded from page 19o, March issue.) the measurement for later reference when con- Atthisstage,thepolishedmirroris structing the telescope. approximately spheroid in form. In thisdistance equal to the radiusof curvature, Once the principle is grasped, the shadow condition it is optically unsuitable for use inwhich in this case is ten feet. phenomena exhibited by the Foucault test a telescope ; parallel light, such as would Joe The pinhole light source should be sightedare easily interpreted.In the Foucault set-ups received from astar, when received br aon the mirror, which is adjusted so that anillustrated in Fig. 8, two types of surface are spherical mirror could not be reflected to aimage of the pin hole is formed upon theshown under test :(a). is a true spheroid, truepoint image ;the more centralraysknife edge ;thisis best carried out in- awith shadow figures for three positions of the would be brought toa focus further awaydarkened room, using a piece of white cardknife edge-inside focus, showing the shadow than those from the periphery of the reflector.to find the image. A support should be mademoving in the same direction as the knife This defect must be corrected before thefor the mirror, so that it can be replaced inedge ;at focus, where the mirror darkens mirror can be incorporated in the telescope.exactly the same position when required. gradually as the knife advances ;this is rather To do this the spheroidal surface must be The image on the knife edge should bedifficult to illustrate, as the mirror fades from made paraboloidal, as shown in Fig. 8.Atthe same size as the pinhole light source andfullillumination to darkness without any first sight, this might appear to be a con-in sharp focus. movement of shadow either from right or left siderable undertaking with the limited re- The eye is placed directly behind the knifeas the knife advances ;and outside focus, sources at our disposal ; yet the methods usededge, whichis moved totheright, thuswith the shadow moving towards the knife arequite simple, and consist of polishing edge. away minute amounts of glass from the cen- Fig. 8 (b) shows a tral zones of the mirror, using asuitably paraboloidal surface ; modified pitch tool.This re-forming of the with the pinhole radiant mirror surface, or " figuring "is controlled at the centre of curva- by frequent testing. ture, no position can The apparatus usedfortesting,whilst be found for the knife making possible results of the unhost accur- edge where the mirror acy, can be simply constrtfcted from odds and darkens evenly over its ends. The type ofapparatus requiredis entire surface ;this is shown in Fig. 7 ;details can be modified to because the radius of suit such equipment as may be available so curvature in creases long as the principle of the test remains un- gradually from the altered.The essentials are these: an approx- imate point source of light ;this must be a centreoutwards. In radiant source, that is to say the light emit- The, Foucault test apparatus. Fig. 8, for the purposes ted from the point must radiate evenly in all of illustration two zones directions, and must not be parallel or con-permitting the light reflected from the mirrorare shown, -inner and outer, and the knife vergent: the other essential is the knife edge,to fall upon the eye ;the mirror will thenedge is placed at the focus of the inner zone, which is a straight sharp edge capable ofappear as a bright disc of light.This isat the mean focus, and at the focus of the smooth lateral movement in or about thebecause the image of the pinhole is formedouter zone. plane of the light source.The knife edgeso close to the eye that the eye lens is incapable At the focus of the inner zone the centre and light source should be as close as pos-of forming an image upon the retina ;theportion of the mirror. is darkened by the sible. aperture of the mirror being so small, however,advancing knife edge, whilst a fainter shadow Inthe diagrams showingtheFoucahltall the reflected light enters the eye throughadvances from right to left around the outer :est the knife edge is assumed to be on thethe iris ;the result is that whilst the shapeedge. right of, and approaching, uthe light source.of the mirror and its surroundirigs are in focus At the average focus, the inner zone shadow The positions of light source and knife edgeon the retina, the pinhole light source is not,moves from left to right, whilst the -outer zone can be reversed if more convenient, but thisand the mirror appears brightly and evenlyshadow moves from right to left., must be kept in mind when interpreting theilluminated. At the focus of the outer zone, only the shadow figures, which would be reversed. The knife edge is now advanced slowlyright-hand portion of the inner zone is free The apparatus must be fixed securely uponfrom right to left until the edge begins tofrom' shadow. a common base, which in turn must be se-encroach upon the light from the mirror ;if Other types of shadow figures are depicted cured in a permanent position.This,forthe mirror surface is exactly spherical, andin Fig. 9 :(a) is a mirror with a turned -down comfort should be about eye level, and athe knife edge at the focus, the light -fillededge, and (b) has a depressed centre. similar position provided for the mirror at amirror will appear to darken/ gradually andFiguring evenly as the knife edge This operation is the " bogy " of amateur advances. telescope makers ;with a little extra care, Pinhole Light Source Should the knife edgehowever, together with common-sense inter- be within the focus, apretation of the Foucault test, the beginner Oshadow will advancemaytackle figuringwithoutundue Knife -Edge Thin Sheet across the surface of the Lead Pierced trepidation, and with every expectation of At Ceptre With mirror,the movementproducing a thoroughly efficient reflector. Needle being in -the same Figuring consists of altering the spheroidal Slides Short Focus direction as that of thesurface of the mirror to that of a paraboloid, Lens Forming image knife edge ;outside theas mentioned earlier ;the difference in form Of Filament On Pinhole focus, the movement willbetween the two types of surface shown in Scale, Piece Cut be in the OppositeFig. 8 is greatly exaggerated for the sake of

From Wooden direction. clear illustration. Pule The radius of curva- In practice, the more central zones of the To Battery Cut -Away To ture can be determinedmirror are polished away to form the required' Al/ow Eye To Be exactlybymeasuringparaboloidal form. The amount of glass Placed Close ro the distance between theremovedbythisoperationisextremely Knife -Edge knife 4dge or the pinholeminute, and is measured in millionths of an Since Brass Curtain Pail and the mirror. inch.This small surface difference,impos- Fittings. half this distance is equalsible to .detect by mechanical methods, is to the focus of the mirror,easily and accurately controlled and measured Fig. 7.-Details of the Foucault test apparatus and pinhole light source. a note should be made ofby the Foucault test. April, 1948 NEWNES PRACTICAL MECHANICS 237

After the initial polishing, the mirror is 22 32 d, - evenly until the level of the depression has tested by means of the Foucault knife-edge 120 0.033in., and d2=120- =o.o75in.been reached.The edges of the pitch tool test ;if the test shows an imperfect surface, The scale (see Fig.7)is used for theseare kept clear of the depressed zone at the such as a turned -down edge, time will bemeasurements ; the procedure is as follows :end of each stroke, and to this end, shortened, saved by returning the mirror to the glassthe knife edge is adjusted so that the centrestaggered strokes are employed ;the mirror tool and repeatingthefinegrinding. A should not be permitted to stop at the turned -down edge, or a depressed centre, Spheroid Paraboloid - end of a stroke, but should be kept in which amounts to the same thing, is very motion, using an oval stroke, and work- difficult to correct on the pitch tool.It is ing the centre of the mirror in a small because of the possibility of having to return circle around the centre of the pitch the mirror to the glass tool for re -grinding tool. that the writer prefers to use a hard -wood Sometimes itis possible to fig J:.-2 a base for the pitch tool. mirror to a satisfactory parab aloid, but If the preliminary test shows the surface which exhibits faint tqol edge zones. to be spherical, then parabolising can be These faint zones can be removed by pr6ceeded with.The pitch tool must be so (b)" smoothing " on a full-size soft pitch modified that the polishing action is greatest tool.Soft tools need to be handled with towards the centre of the mirror;thisis circumspection owing to the tendency of accomplished by trimming,asshown in the outer facets to become depressed, Fig. to. The facets are thus made to decrease thuscausinga seriously -depressed in size as they approach the edge of the tool. central zone. The mirror is then polished for a short Silvering (Chemical*Method) period ;it is wise to err on the side of caution The silvering process con- in the first stages of figuring, so this first sists of depositing a thin film spell should be a short one, say so minutes. 1 r- i of pure silver upon the surface There are so many variable factors involved Spherical Parabolic of the glass ; that it is impossible to give an estimate of the this film will Inside Focus 01 takethecharacterof the time required ;such things as hand pressure, Focus Inner Zone surfaceupon whichitis stroke, and pitch temper all influence the deposited ;thatis cutting speed. tosay, silver deposited upon a The mirror is cleansed of rouge and the surface which has not been surface polished with a clean cloth ;it is then Mean fully polished will exhibit a placed in position on its stand on the shelf for Focus Correspondinglackofre- the Foucault test and allowed to stand there ;flectivity in the silvered for at least half an hour.This is to alloy., surface. A fullypolished the heat generated in polishing to dissipate ; surface, on the other hand, if the mirror is tested immediately, this heat, willtakeasilverfilmof small as it is, will so distort the surface as to maximum efficiency. give an unreliable, knife edge reading. It-isevident,therefore, At the end of the half-hour period the Pinhole Pinhole that since two reflecting sur- mirroristested ;the surfaceiscarefully Radiant Radiant faces will be required (object- inspected by means of the knife edge for traces ive mirror and prism)the Outside Focus Ot of tool edge zones ;these are characteristic Focus Outer Zone mirror surface should be fully of hard pitch and regular polishing strokes, polished before any attempt and are caused by the tool edges reaching is Made to deposit silver upon the same radial distance from the centre ofFig.8.-Diagrams illustrating the method of testing mirrors byit, so as to keep light losses the mirror at each stroke.The remedy is to the Foucault apparatus. to a minimum. stagger the lengths of the strokes. A cleansing operation of the Two or three short spells may be requireddisc darkens evenly-this is the focus of themost thorough nature is necessary before silver- before the mirror exhibits the characteristiccentre, and a note is maclej)f the scale reading,ing. The mirror, after the polishing and figuring paraboloid shadows shown in Fig. 8b. which will be termed fl.The knife edge ishave been completed, is first of all well rinsed A perfectparaboloid would exhibit anthen withdrawn a little, and f2, the focus of theunder the tap ; the disc is then laid face down- ' infinite number of different radii of curvature,inner zone, determined.Similarly, f thewards on a soft dish -cloth in the sink and the increasing in focus from the centre outwards.focus of the outer zone, is found. back and sides well scrubbed with soap and Itisobviously impossible to measure the Then, d,=f, -f1, and should be o.o33in. water. When all traces of rouge and pitch have focus of each tiny zone separately, so for and d, = and should be o.o75in. been removed (a little paraffin is useful for re- practical purposes the mirror is imagined to Actually,itisnot likely that a perfectmoving any traces of adherent pitch), the disc have two or three separate zones, each withparaboloidal form will be obtainedquiteis turned over and the surface well soaped, its own centre of curvature, the inner zonesoeasilyas might be inferred fromtheusing a pad of cotton -wool. Particular atten- having the shorter focus. preceding paragraphs.Knife edge tests aretion should be paid to the edges ;pitch and In Fig. 8 the knife edge is shown in threelikelyto show upvariousimperfections,rouge and other contaminations lodge very positions-at the focus of the inner zone, atsuch as turned. -down edges or various formsreadily in the innumerable tiny chips and the average centre of curvature, and at theof ring zones. splinters which are usually to be found around focus of the outer zone (focus in this case As mentioned earlier, the quickest and surestthe edge of the worked surface.When the refers to the focus when the radiant is at themethod of dealing with a turned -dawn edgesoap washing is finished the disc is thoroughly average centre of curvature). or a depressed centre is to return the mirrorrinsed. The difference between the foci of theto the glass tool.Repeating the fine grinding The surface is now treated with precipitated inner and outer zones when measured fromuntil the turned edge or depressed centrechalk ; a swab of cotton -wool is wetted, dipped the centre of curvature is a definite quantityhas been removed, followed by polishing, isin the chalk, and rubbed over the surface of the for any paraboloidal reflector, and is obtainedpreferable to long sessions on the polishingdisc ;the chalk must be very thoroughly tool, with irritating delays for testing. rubbed in to every portion of the surface. from the formula-where, r is the radius Ring zones, on the other hand, are causedThe swab must be used until nearly dry and R by the edges of a hard pitch tool, and zonesthen discarded, the disc is then rinsed and the of the mirror disc, and R is the mean radius*caused by the polishing tool must be removedtreatment repeated with a fresh swab.It will of curvature. It is difficult to give In this case, where r =3in., and R = szoin.,by the polishing tool. the difference should be 9/ szoin. or o.o75in.,precise instrpctions for correcting and represents the difference in focus betweenthese defects, which might have the centre zone of the mirror and the outerwidely varying characteristics in edge zone. individualmirrors ;inother A cardboard mask (Fig. s s) placed over thewords, the remedy must depend mirror will permit the measurement of threeupon thesymptoms, anditis this stage which requires common Turned -Down zones-centre, inner and outer ; the formula, Edge De° 2ee%'erc; sense andcorrectinterpretation R2 is applied for each of the two radii tin.of the shadow test. Fig. 9.---.-Shadina .formations on the surfaces of mirrors. and 3in. Ring zones are invariably de- The two differences to be measured willpressed zones-raised ring zonesFig. to (,right) -Pitch tool be between centre and inner,'and centre andare not likely to occur; the treat- modified for parabolising. outer zones, and are found as, follows :- ment is to polish the entire surface 238 NEWNES PRACTICAL MECHANICS April, 1948 - be found that an appreciable amount of rouge,not less than 65 to 7o deg. F.The solutionsrun over the surface and removed with dry etc.,willbe removed by thistreatment.and mirror should both be at this temperatureblotting paper ;the mirror should then be Repeated applications of the wet chalk willforsatisfactory results. completely dry in a few minutes. have the effect of removing the surface greasi- If the operation is being carried out on a The silvered surfaceisthen burnished, ness ;it should be possible, after the preci-warm summer daysilveringcan proceedusing small clean pieces of chamois leather. pitated chalk treatment, to wet the surfacewithout further delay ;but in cold weatherThe pressure applied should be very light without the water draWing back and leavingsteps must be taken to take the chill off theat first, and very gradually increased.Each the edges dry.When this condition hasmirror and the solutions. piece of chamois leather should be used for a been achieved the disc is rinsed to clear it of all The mirror disc can be allowed to stand in,short period only, and then discarded. traces of chalk.From this stage onwards thewarm water for a short time until the glass A little dry rouge may be used after the mirror surface should not be touched by thefeels warm to the touch, taking care, of course,first two or three pieces of chamois, but this is fingersor allowed to become dryuntil theto handle only the back and sides of the disc.usually not necessary. silvering has been completed. A strip of clean stiff paper is obtained, 2 to The next operation is to swab the surface3M, wide, and long enough to wind once orThe Teles'cope with concentrated nitric acid. twice around the edge of the mirror ;a length of the red paper backing used on camera The actual construction of the telescope is The acid is poured on and mopped over outside the scope of this article ;in any case the surface with a swab made from cotton -films is ideal for- this purpose. The paper is wound tightly around the edgesince design is likely to be dictated by available wool tied to the end of a smooth ended glass materials itis unlikely that any two home - rod. constructed telescopes will be alike. The acid is rinsed off under the tap and all As mentioned in the opening chapters, the surplus water drained away. optical system is very simple, and consists of Aconcentratedsolutionofstannous a 6in. reflector, small 90 deg. prism or silvered chloride is now prepared and poured on so flatmirror(surfacesilvered-an ordinary that it covers the entire surface ; this is allowed back -silvered mirror would be useless, pro- to stand for a few moments and then rinsed ducing a doubled image) and eyepiece.It off under the tap. No traces of chloride can is important that the prism or silvered flat be permitted to remain and this rinsing must should possess high quality worked surfaces ; be very thorough. it is of little avail to spend long hours working After the tap rinsing the disc is rinsed in the 6in. reflector to a high state of perfection water.The cleaning operations are now completed and the surface is ready to if the resulting image is to be marred by receive its deposit of silver. prism distortion. Hit is not convenient to silver immediately,Fig. 11.-Mask used when measuring the focus The design of the telescope tube is shown in the mirror should, be kept immersed in dis- ofdifferentzones. Fig. 12 ;the reflector is seen mounted in a tilled water. On no account should' theof the disc and secured by binding withcell, which should be removable so that the surface be allowed to become dry until the mirror can be covered up when the telescope string. is not in use.The author's tube was made silvering is completed. The two solutionsalready prepared arecheaply and efficiently of tip plate by the then filtered through cotton wool into cleanlocal tinsmith, with a simple bayonet type Silvering-Brashear's Process glasses;to each solution is added an equalrelease for the cell.There is no necessity The following solutions will be required forvolume of distilled water. for the tubeto be cylindrical-it can be the silvering process : The glass containing the reducer solutionsquare section and built of wood, if more Solution A is also allowed to stand in warm water untilconvenient.Indeed, a tube is not entirely 75 c.c. water. it has absorbed sufficient heat.The silvernecessary, and many of the world'slargest 5 grammes silver nitrate. solution is not heated. reflectors are of open-work girder construction. Solution B Assuming that the disc has been warmed The prism fitting should be constructed of 25 c.c. water. and bound with its paper " collar " the silver- ing operation can now be carried out. fiat strip metal, edge on to the reflector to 3.5 grammes potassium hydroxide. minimise the effect of silhouetting. Solution C The solutions are mixed by pouring the 15 c.c. water. reducer into the ammoniated silver nitrate The completed telescope tube will be quite gramme silver nitrate. solution in the proportion r to 2; that is toheavy, and will require to be mounted on a Concentrated Ammonia. say, if there is roo cc,. of silver solution, thenstout base, with provision for horizontal and Reducer Solution 5o c.c. of reducer would be poured into it. vertical movement. 3o c.c. water. The mixture is stirred, when it will become The image is inverted, as in a refracting 2 grammes dextrose. straw-coloured and then dark brown.Atastronomical telescope, so it is not convenient All water used must be distilled. this stage it is poured immediately over thefor use as a terrestrial telescope, although an mirror the whole of the solution is pourederect image can be obtained by turning one's The method of preparation is as follows :on, and the mirror gently rocked.If properlyback to the view, and looking down into the Solution A is poured into a clear tumbler eyepiece. and ammonia added to it drop by drop, usingbound on, the paper will prevent any serious a medicine dropper ;a brown precipitateloss of solution over the edge. In these days of shortages, the construction will be formed, and the solution should be stirred with a glass rod as the ammonia is Eyepiece added.As the cloudiness begins gradually 90.Prisin Mounted in Tube todisperse,theliquid should bestirred Fig.I2. -A telescope vigorously between each drop until the solutiontube-part broken away just clears.Great care must be taken not toto show the mounting add too much ammonia, and a 4ew drops ofof the prism and eye- nitrate solution-solution the second silver piece. /r/e4irr

C-are added until the liquid assumes a faint Flat Strip Metal Mounted Cell straw colour. Edge On To Reflector The solution is now ready for the addition of solution B. This should be added cautiously, using a clean medicine dropper and stirring By this time the liquid will be quite black,of the telescope mounting will provide many constantly.Thereisapossibilityunderwith broken films of silver floating on thedifficulties ;but the constructor who has the favourable conditions of the solution formingsurface.As the disc is rocked, a heavy blackpatience to grind, polish and figure a 6in. crystals of the explosivesilver fulminate ;precipitate will be seen in the solution thisreflector, and who constructs a makeshift for this reason the solution should be stirredmust not be allowed to settle on the surfacemounting, is not likely to abate his efforts constantly,andthepreparationoftheseof the mirror, but must be kept in motion ;until he is the proud possessor of a first-class solutions should be carried our in a cold roomif necessary, the surface can be lightly swabbedhorne-madetelescopewithanefficient if possible. with cotton -wool. equatorial mounting. When all of solution B has been added, In ashort time -5 torp minutes-the more ammonia should be added, drop byliquid will clear;the discis immediately drop, until the mixture just clears ;as before,rinsed clear of solution and the paper removed. GEARS AND GEAR CUTTING drops of solution C are added until a brown The mirror, which should now> have a precipitate begins to appear. perfectsilversurfacefree fromstains,is Edited by F. J. Camm. The solution is filtered through cotton wool,immersed in clean water and allowed to stand Price 6s. from allBooksellers or 6s.6d.by post from George Newnes, Ltd., (Book Dept.). and is then ready for use. for an hour.At the expiration of this period, Tower House, Southampton Street, London, The temperature at which the silvering isit is removed and excess water removed with W.C.2. carried out is most important-it should beclean blotting paper.A little alcohol is then April, 1948 NEWNES PRACTICAL MECHANICS 239 A Useful Radiator An Easily Constructed and Efficient Heater

By E. S. BROWN THE portable radiatorherein describedof the reflector to 'take the heating cone, and consists of a simple and easily -madetwo more holes of the same dimensions are heating unit and parabolic reflector attachedmade within fin. distance from the two sides by suitable means to an ordinary paraffinfor the flame -guard supports. A further four pressure stove. 3/ t6in. holes are suitably drilled along the During the early spring evenings such abottom edge tobolt do theclips which radiator is invaluable, as it provides a verysecure the reflector assembly to the stove. convenient and inexpensive means of heat-(See Fig.2.)When the holes are drilled, ing, and is, of course, ideal for the bathroom,remove any dross that may be present around where the presence of steam and generalsame, and well burnish one sideofthe dampness prohibits the use of any portablealuminium sheet with a good quality metal form of electrical heating. polish. The reflective powers of the radiator The dimensions given for the various com-depend absolutely upon the quality of the ponents are a generalisation, and although finish imparted, so every care should be taken to ensure a perfect mirror finish. The aluminium sheet must now be care- fully bent into the concave shape as indi- cated, and the heating cone fixed in position 0 'with a Ain. by 4in. bolt interposed with a 0 distance -piece ofin. by 31in.. tubing, as in 0 Fig. 3.The flame -guard is made by bolt- 0 The radiator fixed on the pressure stove, ready 0 ing a piece ofin. by t2in. tubing, flattened 0 and suitably drilledat both ends, to two far use.

Osg Flame Guard Perforated Heating Cone to the stove supports.The clips allow a cer- Bolt Hole tain amount of vertical movement to he made, 3 and thisis necessary in order to correctly Overlap position the heating cone over the burner. Fig.1.-Shape and dimensionsof heating - Experiment will decide the most satisfactory cone blank. distance.In the writer's case the best posi- tion for the cone was found to be tin. above the burner. suitable for the average pressure stove, they The object should be to contain all the may have to be slightly varied to suit indi- flame within the heating -cone, and to' also vidual circumstances. heat the cone to a bright red to obtain the maximum radiation. When this has been Heating Cone and Reflector attained, bolt the clips tightlyto ensure a The heating cone is made from a piece of permanence of position.

stout tinplate, 71in. by 31in., and shaped as ...... 1111111111111111111,1111!I II 111'1 shown in Fig.t.A series of ;in. diameter Pre -heating the Burner holes is drilled in the tinplate, which is then When lighting the stove, make very sure carefullyshapedtoformacone. The Bolt Distance Flame Guard that the burner is sufficiently pre -heated with measurements of the cone, allowing alin. NUt Piece Support methylated spirits before applying air -pres- overlap for joining purposes, should be Sin. Fig. 4.-Plan of radiator slowing the assemblysure, otherwise a smoky flame will result and diameter by 31in. long. The overlap is drawn spoil the reflector.Also see that the stove is together and secured by two or three small layout. not in a draught, as otherwise the flame may nuts and bolts. bt deviated from heating the cone, and the The reflector is made from a piece of 16tubular side -members fin. diameter by 7ip.radiator's heating power will be correspond- or r8 gauge aluminium nin. square. A long.(Fig. 4.)Two lin. by 71in. bolts willingly impaired. diameter hole is drilled in the exact centrehe required, and the assembly is securely bolted to the reflector, thus ensuring a par- Reflector, 12' ticularly robust and rigid form of construc- tion. Distance Piece Bolt Fixing Fixing Clips _IA.- Heating 2 2 Cone To The clips securing the radiator assembly Reflector tothestovearepreferablymade from aluminium. Strips of suitable size are cut, and are bent around the stove supports with a pair of pliers.Holes are next drilled in 12" the strips to correspond with those made in the reflector, and the assembly is then bolted

A NEW VEST POCKET BOOK JUST FsUBLISHED NEWNES METRIC & Heating Cone DECIMAL TABLES

I \ 0 I151 0 ono By F. J. CAMM F,,ang --- Nut And Bolt 3" DiaHoles DiaHoles 316 or 3/9 by post from Fig. 2.-The reflector plate drilledforthe Geo. Newnes, Ltd., Tower House, fitting of heating cone and flame guard, and Southampton St.,Strand, .W.C.2 Fig. 3.-Side view of reflector, showing method also showing fixing clips. of attaching heating cone and fixing clips. 4 240 NEWNES PRACTICAL MECHANICS April, 1948 THEWORLD OF MODELS The National Maritime Museum, Greenwich By " MOTILUS"

surely restored to the galleries at Greenwich, whichhavebeen redecoratedtoreceive them. The finebuildingshousingthe Museum (Fig. 1)lie adjacent to the Royal Naval College and were converted for use as a Museum through the generosity of Sir James Caird, Bart., having been previously the Royal Hospital School for educating sons of seamen and marines. The School, founded 1.-The National Maritime Museum, Greenwich, showing the Queen's House and the in 1752, was originally housed in the Green- West Wing, viewed from the north-east corner of the grounds. wich Royal Hospital but later moved across the road to the Queen's House, a villa designed THE Thames below Tower Bridge-world ? If he had visitedthe Nationalby Inigo Jones for Henrietta Maria, wife Dep:ford, Greenwich, Wapping : whatMaritime Museum at Greenwich, asI didof CharlesII. In 1807 colonnades were diverse associations these names callrecently, he would without doubt have theerected to the east and west of the Queen's to the minds of Englishmen, whether theymost vivid recollection of some of the won-House and two flanking wings were subse- have visited these historical places or. not.derful models that are to be seen among thequentlybuilt,sothatthe Museum now Even among London's eight million the ideasvastcollectionsinthis home of nauticalconsists of three principal buildings. such names suggest must be many and varied.history. Before referring to a few of the many The historian recalls entries in Pepys' diary The present National Maritime Museumintriguing and varied ship models, I would -" By water to Greenwich "-written bydeveloped from the Royal Naval Museum inliketo mentiontheappointment,nearly this Thames -lover in the days when the gilt -Greenwich Royal Hospital (now the Royal12 months ago,of Mr.F.G. G. Carr, decorated Royal Barge was frequently to beNavalCollege) and was envisaged in theM.A., LL.B., F.R.G.S., as Director of the seen on its tranquil journey from Westminsterearly 5930's.It opened in 1937, but wasNational Maritime Museum.Mr. Carr has Palace to Greenwich. The sailing ship loverclosed at the outbreak of war in 1939, when thea lifelong experience of sailing and shipping conjures a picture of the last sailing bargesValuable exhibits were sent away for safety.round our coasts, as well as a wide knowledge now remaining on London River-the spritsailNow, however, they are being slowly butof books and manuscripts, obtained through barges, so characteristic of the Thames. The modern shipping student links these names in his thoughts with the Port of London and the Isle of Dogs.For the merchant they mean the warehouses in the Port, where so many of Britain's imports find a temporary resting - place.:timber from the Bailie, grain from Canada, sugar, bananas and rum from the West Indies. What associations, then, might a model enthusiast have with this part of the

Fig. 3.-Model of thehull of the" Royal William," a ship of icio guns, built at Ports- mouth in 5759. Her guns were reduced' to 84 in 1757 and she was finally broken up in 1853. Scale of the model is5'48 actual size=4ft. to Tin.

hisprevious appointment as Assistant Librarian to the House of Lords. So, with his untiring enthusiasm, heiswell equipped for the large task of organisation that confronts the director of a museum dealing with the records of those achievements which have made the maritime history of Great Britain so vital.When I visited Greenwich I had The pleasure of meeting Mr. Carr, and he was good enough to devote a considerable amount of his valuable time to pointing out to me many interestingexhibitsandalsonew features, arrangements and amenities of the Museum.The latter, incidentally, include a modern restaurant. Ifeelthat under Mr. Carr's able direction the Museum will becomeaveryliveattractionforboth Londoners themselves, andall who visit London from otherpartsofBritain and from overseas. We enter the Museum through the East Fig. 2.-Model of the " St. Michael," a ship of 90 guns, built at Portsmouth in 1669Scale Wing, whence a colonnade leads to the Queen's of the model is5148 actual size-oft. to sin. House,containingvariousexhibitsfrom April, '1948 NEWNES PRACTICAL' MECHANICS 241' ,early times up to 1702. A paved way passesrepresented.In this case the model shows Ascending the northern staircase of the right through the centre of the Queen's Housegilding on the upper -work of the ship, aWest Wing you pass a glass -case model of a to a further colonnade connecting with theform of decoration that gradually disappearedgalley of the Knights of Malta. These West Wing. This is the path of the oldafter1703,butitalsobearstheinitialsMediterranean galleys varied very little from Deptford -Woolwich Road. The Queen's" A.R." (Anne Regina) in the carving, sothe sixteenth to the eighteenth century, and it House was built on either side of the roadcould not l3ave been earlier than 1702. Ais often difficult to fix the date of any particular and the two portions were connected by oneremarkable feature in this model is a windlassmodel. This one, to an approximate scale of room built across the roadway and whichtransmitting the steering to the rudder by a1/30 actual size, has been placed at about 1780, thus became known as the " Bridge Room."chain, which is believed to have been a fore-as it has a mizen mast and these were only used Later, other rooms were built over the road,runner of the steering wheel. The model wasin the latter part of the eighteenth century. but the original room still retained its name.presented to the Greenwich Hospital in 1830,This large model, presented to the Royal by William IV.A further development inNaval Museum, in 1828, by the Duke of Dockyard Models the history of the steering wheel can beNorthumberland, shows the typical lateen sails In this room and others in the Queen'sseen in another model of a 50 -gun ship ofof these galleys and the long oars that were House are some of the earliest contemporaryabout 1703, in the same gallery.Built to amanned by galley -slaves when the wind was scale models of ships in -existence. These arescale of 1(48 actual size, it shows the steeringunfavourable. known as dockyard models, as in nearly allwheel used in connection with the earlier Some of the contemporary ship models of cases they are built to reveal the interior ofwhipstaff and is probably the first evidencethe late eighteenth century have the distin- the ship, the hull being left unplanked toof such a fitting as the wheel being used inguishing feature of the sliding keel, or centre- show form of construction.Many of thesean English ship. board, as designed by Captain John Schank. models show in perfect detail the elaborate In Gallery I3V, which covers the periodThere are two model sloops in the Museum, carving and gilding on the upper work offrom 1739 to 1748, I was shown a modelone of 36 guns, dated about 1790 and another their prototypes. I particularly noted a model(scale1/48 actual size) made f6r Admiralof 14 guns of about 1795, both built to a (scale 1/48 actual size) of the " St. Michael "Anson in 1747 of his ship " Centurion."scale of 1/48 actual size.These have keels (Fig. 2), a ship of 90 guns built at PortsmouthBuilt at Portsmouth in 1732, the " Centurion "on the Schank system, but ncither has been in 1669.This model stands in the Bridgecarried the Admiral on his voyage round theidentified with any particular ship.Another Room andisbeautifullydecoratedandworld.A portrait of this Admiral hangs insliding keel model is that of the six-gun brig, gilded. Another fine model, showing dis-Gallery V, and another, painted when he" Lady Nelson "(scale1/32actualsize), tinctive grace of line in her hull, is that ofwas a Commodore, in Gallery IV. builtin1799. She served in Australian the first English Royal Yacht, given to Charles Most of us know the famous ." Royalwaters as a store -ship and surveying vessel from II by the Dutch, in 1660, after which many similar vessels were builtillthis country. The model of the yacht was made about 1675, to a scale of 1/32 actual size. There are many of these revealing dockyard models amid numerous other treasuresin the Queen's House. The Caird Galleries in the West Wing containextensivecollectionsofportraits, maritime pictures and prints, medals, seals, navigation instruments and authentic relics

Fig. 5.-John Harrison's fourth chronometer, with which he won the £20,000 prize offered by the Board of Longitude.On the right is the replica made by Larcum Kendall and used by Captain James Cooh on his voyage between 1772-9.

George," the too -gun1800 to1825, but was then captured by shiplauncheda tnatives in the Timor Sea.The sliding keel Woolwich in 1756, ofenabled a vessel of very shallow draft (keel which there is a dock-up) to sail to windward (keel down).It was yard model here. Shealso possible to use the keel, of which there was the first Englishwere three sections, forward, amidships and three -decker ship withaft, respectively, to alter the sailing trim of channels fixed abovethe vessel and thus help with the steering. the upper -deck guns, an innovation whichNavigation Instruments did not become gen- One of the most fascinating rooms in the eral for another 3owhole Museum is the one devoted to the years.This dockyardhistory of navigation.Here is to be seen model, to a scale of 1 /48that very ingenious but rather impracticable actual size, shows ex-piece of work, Drake's pocket astrolabe, as cellent workmanship,well as other early astrolabes ' cross -staffs, especially in the re-back -staffs and quadrants. Here also are markable detail in theJohn Harrison's four chronometers. Harrison, 4.-John Harrison's first chronometer, construtted in 1735. This stern carving.Hang-aYorkshirecarpenterandmechanician, was used on a voyage to Lisbon in H.M.S. "Centurion" in1736. ing near the modelmade his first chronometer in 1737.(Fig. 4.) is a fine painting, byIt was so constructed that it needed no oil at of such\famous figures as Drake, Cook a adJohnCleveley,theElder,showingtheall to maintain its smooth running, although Nelson, as well as comprehensive records in" Royal George " lying at Deptford in 1757.it became necessary in the later developments. the magnificent library of over 50,000 books. The ship was lost at Spithead in 1782, whenIn 1713 the British Government offered a Admiral Kempenfelt was drowned. Cowperreward of k20,000 for discovery of a method Contemporary Ship Models gives a romantic account of thisinhisof determining longitude at sea to within a Among the contemporary ship models inpoem," OntheLossofthe' Royalmaximum error of 3o miles. Although Harri- Gallery III, Mr. Carr drew my attention toGeorge '," but he was apparently blissfullyson claimed the reward for his fourth chrono- a model ship of 96 guns (scale 1/6o actualignorant of the telling fact that the loss wasmeter (Fig. 5), the Commissioners of Longi- size), dated about 1703.Various clues in thedue to a large part of the ship's bottom fallingtude did not pay him in full until 1773, construction of a model often have to beout !A sad token of the bad condition of theand then only after intervention on the part relied on in deciding the date of the shipship and Admiralty neglect in those days. of the King. Unfortunately, Harrison was too 242 NEWNES PRACTICAL MECHANICS April, 1948 old to enjoy the fortune by that time. A copy ofHarrison'smaritimewatch, made by Kendall between 1767 and 1769, was used by Captain James Cook on his voyages between 1772 and 1779.It is remarkable to note, from an entry in Cook's Journal on his return to England, after having been round the world, that he records the watch as being out by only seven minutes 45seconds(inarc), which is roughly an equivalent of two minutes in normal time.I wonder how many modern watches, even Swiss made, could be proved so reliable ! Examples of more up-to-date models can be found among thevariedexhibitsin Neptune's Hall.(Fig. 6.)One case in this large hall contains a representation of the Battle of Trafalgar, made to a scale of approxi- mately if16in. to 'ft., the ships being shown as waterline models, set in an imitation sea. There is also a model of " Cleopatra's Needle " and the craftin which this now familiar Thames Embankment landmark was towed to England.Modern craftsmanship is well to the fore in some excellent British -made ship models ; H.M.S. "Arrow," superbly modelled by her builders, Messrs. Vickers Armstrongs, Ltd., and the Royal Mail Line hospital ship, " Atlantis," showing thefirst-classmodel work of Messrs. Bassett-Lowke, Ltd. There arealsoseveral German -made models ofFig. 6.-Neptune's Hall, formerly the gymnasium of the Royal Hospital School, which German seacraft : a submarine, a pocket battle- now contains a huge collection of many types of ship models of all periods and in various scales. ship and Hitler's private yacht, the " Grille." Tiny Model Cannon worlds of art, history and shipping.Facilitiesby river steamer from Westminster Bridge, Before leaving Neptune's Hall, Mr. Carrfor reaching the Museum from London arewhich takes about three-quarters of an hour- asked me to look through a magnifying glass atnot at present as good as they should be,time that passes all too quickly when you are the smallest exhibit in the Museum-a modelespecially when theboatservices on thewatching the busy life of London River and cannon, weighing less than a grain and noThames arenot running, butthereareidentifying the places that you pass en route. more than a speck when seen with the nakedseveral ways of getting there by road and railHere is an idea for a day's vacation in a part eye.This tiny novelty was originally madeand a visit is well worth while.The mostof London teeming with historical interest, for theGreatExhibition,heldin Hydefrequent train service is from London Bridgeand if you are a ship model enthusiast, you Park, 1851. to New Cross and then by tram to the Museum.have at the same time a fine chance of increas- It is impossible, within the space allottedAlternatively, you can take the train to Mazeing your knowledge of the development of to this feature, to give you more than just aHill, which is within walking distance of theship modelling in this country. microscopic impression of thefascinatingMuseum, buttrainsthatstopthereare [Note :All the illustrations in this article are things that await the visitor to this Museum,infrequent.During the spylng and summer,by thecourtesyoftheNational Maritime either " in the world of models " or in thethe ideal way of approaching Greenwich isMuseum, Greenwich.]

lubrication, bothdieselandcoilignition engines, is Thelson motor oil H.C5o, manu- Letters from Readers factured by KennethThelwall, Ltd., Churchill Road, Doncaster. "Institution of Mechanics" the instrument.They are not original, but Thisisacastor -basedoilcontaining SIR,-A small 'group of skilled mechanicscouldatone time be seen exhibited on averyefficientinhibitor which prevents those types displayed in the South Kensing-piston ring sticking, and thisis one of the havebandedtogethertoformanton " InstitutionofMechanics,"toraisethe Science Museum.In one form thedrawbacks associated with this type of oil. status of the skilled mechanic, assist in thetracerpiececarriedamilled -edgeddisc, There are r t present only limited supplies interchange of ideas, experience and mutualwhich could turn freely about the tracingof this oil available, but I am sure that the help. We wish to raise the quality of crafts-point so as to serve as a convenient handle.firm would do their best to supply orders from model aero clubs.-P. W. HALDRICH manship and provide employers with a pool RY Tocentre of from which they can choose a really skilled 'atchet. (Hungerford). man for any job.By encouraging members to study foremanship or industrial psycho- String Washers , logytocertificatestandard, we hopeto SIR, - In the issue of PRACTICAL ensure that members get a chance of promo- Milted edge MECHANICS for December, 1947, you tion when promotion is going. disc published a very interesting leading article We havethebackingandhelpofa about inventions.What interested me most Member of Parliament, the good wishes and was your remarks about the various kinds future help of the Minister of Labour, and Tracing of spring washers that had been invented individual interest of mechanics asfaroff point. and that they had not been very successful. as the occupation forces in Germany. I may statethatIhave had 4o years' Would any readers interested in the aims experience in driving and. repairing traction set out above, or in any way interested in A planimeter improvement. engines, road rollers and steam wagons in the cause of the skilled mechanic and the many partsofthecountry betweenthe furthering of craftsmanship, even those -not Also,thistracing point was made separ-Moray FirthandtheEnglishChannel. engaged professionallybut are skilledately and screwed to the loin. bar, as shownWhen Ifirststartedin1892 there were amateurs, drop me a postcard.Iwill tryin the accompanying sketch. no fine tar macadam roads, but only rough, to put readersintotouch with others" in In another form the horizontal loin. baruneven roads, and traction engines were very their locality so that they may form localwas graduated so that areas could be readhard to stand on owing to the vibration, branches.-A. L. JACKSON, Acting Secretary,off directly, i.e., distances were marked cor-which made the driver'steethchatterat responding to the marks made on the paper, times.There was plenty of strain on bolts, 118, Westwood Park, London, S.E.23. and numbers set against them equal to the computed areas.-G. ails (Sheerness). and very often nuts and lock -nuts had to "Hatchet" Planimeter be tightened up.Lock -nuts were not im- provedbyanyofthetypesofspring SIR,-In reference- to the article on theModel Aeroplane Lubrication washers.After trying many ways of keep- " Hatchet " planimeter in the October, SIR,-The following note might be inter-ing nuts from getting loose I found out a 1947, issue, here are one or two additional esting to model aero enthusiasts.The vay by chance which proved so successful detailswhichreaders may easilyaddtomostsuccessfuloilformodelaeroplanethat I used it as long as I carried on driving. April, 1948 NEWNES PRACTICAL MECHANICS 243 I simply used a piece of ordinary thick string I have not driven any steam road engineIwouldhumblysuggestthefollowing as a washer. for several years, but Istill keep my faithmethod: I screwed up the nut till there was justin the string washer. Mix a small bottle of red ink with three room to get the string between the nut and I look forwardfor my PRACTICAL tablespoonfuls of household ammonia, two the plate or bearing cover, then twisted theMECHANICS every month asitisthe besttablespoonfuls of common salt, two squares string round the bolt or studtillitfilledpaper I get.-W. JOHNSTON (Aberdeen). of washing blue and three tablespoonfuls of the space to the outer edge of the nut, and cold water.Place four or five lumps of tightened the nut as hard asIcould. ICrystallisation Experiment coalaboutthesizeoftangerine oranges did the same with the lock -nut, and when in a glass bowl and pour the mixture over the string was cut off close to the edge of SIR,-I read with interest, in your Januarythem. Standina warm place. Every the nuts there was nothing to be seen. issue, the answer to Mr. A. Gasser'ssecond day pour over the coal a tablespoon- question regarding the production of crystalful of water in which has been dissolved a A piece of thick string was quite suitablegrowths on coal.No doubt the methodteaspoonful of salt.In a short time there for bolts from tin: upwards, and for smallersuggested would produce the desired effectwill be a bowlful of crystal growths which size bolts I untwisted two or three strandsup to a point, but I cannot help thinkingwill be both interesting and decorative.- to suit the size of bolt. that the whole process is rather ponderous.H. H. MIDDLETON (Twickenham).

betweenthescreensnecessitatedmov- ingthecamerabacksofarthatthe traceswerereducedeventuallytoan Trade Notes impracticable scale.To provide a record on a practical scale where a number of traces D.P. Kathanode Batteries New Recorder of Oscillograph Traces arerequiredtobeshownsidebyside THE first main -linedieselelectrictrac- Avimo now have in production a series of tion locomotive for passenger service inIT is well known that high-speed mechani-recording cameras with built-in cathode-ray this country has been undergoing final trials calL or electrical variations can be trans-tubes-the latter so arranged .that their traces and a duplicate locomotive-No. to,00t-lated by a standard commercial oscillographare photographed through a mirror.In this will later be brought into service. - into visible traces on a fluorescent screen.way as many as15 traces, plus a timing The giant 16 -cylinder, 1,600 h.p. " EnglishThe impermanence of the traces, however,interval, may be recorded on a scale adequate Electric "dieselenginesareelectricallymakesdifficult any accurate study of thefor practical purposes. started by means of x2o-volt, 236 ampere -inter - relationship of hour D.P. Kathanode diesel traction several phenomena batteries, manufactured by the D.P. Batteryand makes impossible Co., Ltd., Bakewell, Derbyshire.This typeany subsequent of battery has been,exhaustively tested out inchecking ; and at- actual service on diesel-electric locomotivestempts have been used mainly for shunting operation by themade withvarying London, Midland and Scottish, London andsuccess to photo- North Eastern and Southern Railways. Thegraph these traces by battery is designed to operate with a gener-means of standard ous safety margin under conditions much cameras. more severe than are likely to be actually During the late war encountered, as, for example, with a tem-Messrs. Avimo, Ltd., perature at freezing point and in a half -dis-designed special charged state. cameraswhichgave The cells are assembled in specially treatedmuchmore, satisfac- wood trays, these being fitted with porce-toryresultsandre- lain insulators on the sides. and ends.As corded, side by side, headroom is somewhat restrictedthe cell -on continuous film or containing trays are mounted on steel -facedpaper, traces from any ebonite runners sliding in channels to facili-standard type of oscil- tate easy withdrawal for periodical inspection.lograph. The number Handles are fitted on the ends of the traysof traces which could beso recordedwas, for this purpose, and each cell is providedhowever, 'limited with a float to enable the acid level to be TheAvimo FifteenChannel Camera which records55oscillograph readily observed. inpracticebythe factthatthespace traces side by side.

lapped at 25 m.p.h. on ax2ft.line.' Mr. Jackson's " Kitten " and Mr. Ward's free- Club Notes lance model, although only partly finished, showedtheirpaces. The meeting was Wallasey Society of Model and Ex-rounded off with an R.T.P. flying competi- perimental Engineers tion which was won by Mr. Harrison's N exhibition will be held from April 8th" Thistledown."His encore flight lasted 66 tolothat Church StreetSchools, seconds and was warmly applauded.-Hon. Church Street, Wallasey, and will open asSec.,F.H. PLASTER, " Virginia House," follows:Thursday and Friday, 5-9 p.m.;Cartwright Lane, Beverley, E. Yorks. Saturday, 12 noon to 8 p.m.There will be steam locomotives on a passenger -carryingSociety of Model and Experimental track, a working " oo " railway layout and Engineers other models working on compressedair. THE above club will hold its fifth exhibi- -Hon. Sec., W. K. NICHOLAS,12, Rose tion during Easter week. Mount Drive, Wallasey. The exhibition will be held from Wednes- day, March 31st,toSaturady, April 3rd The Beverley Model Club (inclusive) at the Central Technical School, D.P. Kathanode traction battery. THIS club now meetsat" Cross KeysLeopold and West Streets, Sheffield.Entries Hotel," Lairgate, Beverley.The timesof all kinds will be welcomed from " lone Batteries of the type referred to above areare as before, viz., 7.3o on second and fourthhands " and from other societies;all such being manufactured for 12 main -line diesel-Mondays. At the first annual general meetingentries will be eligible for awards, and judg- electric locomotives for the Egyptian Stateheld on January 26th it was agreed that theing will be independent and anonymous. All Railways. club was firmly on its feet in spite of onlyexhibits will be insured. D.P.Kathanodedieseltractionbat-five months' existence.Plans of the model As in former years, it is hoped to have the teries of somewhat smaller capacity are in usecar section are going ahead, and on Febru-valued co-operation oftheSheffield Ship on many diesel-electric shunting locomotivesary 5th the first public demonstration wasModel Society, the Sheffield Society of Aero- atthe presenttime, amongst these beinggiventothepeopleofBeverley. Mr.modellersand theSheffield Model Yacht 37 operated by the ex-L.M.S., L. & N.E. andTurner's " Kitten " showed the possibilitiesClub.-W. J. HUGHES, 87, Hopedale Road, 41 Southern Railways. of this branch of modelling, and on one runFrecheville. Sheffield. 244 NEWNES PRACTICAL MECHANICS April, 1948

The rheostat itself must be mounted and securedmanufactured from bitumen, but being verymuch well out of the reach of the liquid in the tank, otherwise harder than the latter. it would become oil splashed and thereby refuse to Very many industrial chemical tanks are asphalt -lined, function. the asphalt used for the purpose being of a special A system operating on these lines will, we think,variety known as" acid -resistingasphaltmastic." QUER1ESGA1.4 give you a much more accurate indication than wouldFor tank -lining purposes this type of asphalt must be ahydrostaticlevel withitslong liauid-containing used.Two (in.thick layers of this asphalt would pipeline, which would be subject to all sorts of tempera- resist hydrochloric acid up to a 50 : 5o dilution with ture and barometric changes. water at a temperature of 6o deg.. F., provided that there was not much mechanical agitation of the liquid ENQUIRIES in the tank.But this concentration and temperature Potash Manufacture of acid is very near the borderline, and hence you would CAN you suggest any method by which dry have to be prepared for a slow deterioration of the surface waste wood and fresh forest timber waste of the asphalt tank -lining, so much so that a resurfacing can be utilised in the manufacture of potash might be necessary after two or three years of usage. Astampedaddressed envelope,threepenny-, on a small commercial scale ?If the project is As an alternative to an asphalt -lined tank, have you stamps, and the query coupon from the current feasible,Ishould appreciate details of plant, ever considered a strong wooden tank, glass lined, and issue, which appears on page 56 (THE CYCLIST), process, etc. -H. J. Lucas (Southampton). with the jointsof- the glass made up with a good must be enclosed with every letter containing a POTASH (potassiumcarbonate) was formerly acid -resisting cement ? Ifitsjointsaregood, query. Every query and drawing which is sent obtained very largely from the ashes of plantssuch a tank will last almost indefinitely, and at any must bear the name and address of the reader.. and wood which were burnt in iron pots ;hence thereasonable temperature, always provided that its glass Send your queries to the Editor, PRACTICAL name " pot -ash." linings do not became mechanically damaged. MECHANICS, Geo. Newnes, Ltd.. Tower Houso, In some parts of Canada and the United States An electrical heating immersion unit can be used in Southampton Street, Strand, London, W.C.2. the process is still, we believe, carried out in a veryeither case, but withabitumen -linedtanksteam small way.Briefly, this process is as follows : heating should not be used unless the steam coil is The wood chippings, etc., are burnt completely in kept at a good distance from the asphalt lining, for, Making Leathercloth smooth -walled pits.The ashes are collected, mixedwith steam heating, it is very easy for a development forwith a small quantity of lime, and then extractedof excess local heat so to soften an adjacent area of WILL you please supply me with a formula with boiling water in open tanks or boilers.The liquidasphalt that it slides down to the bottom of the tank the paint used in making rexine or leather -is drawn off, roughly filtered, and then evaporated toand flans leaves a " weakness " in the asphalt lining cloth and the method of applying it.Can it be dryness.The dry matter is then heated to red heatwhich is steadily (and usually rapidly) progressive, and sprayed ?How are the antique and hide effectsin order tocalcine and burn away any remainingthus results in the entire disintegration of the tank obtained organic matter.The material which remains is of alining. I should also like to know if the paint can becreamy colour and was at one time known as " American bought. -L. G. Roberts (Bexley Heath). potash."Itcontainsvaryingquantities of caustic LEATHERCLOTH of various trade names is essen-potash, from which substance various potassium com-Renovating Canvas of Oil Painting tially a closely woven fine canvas material,the pounds can be prepared by the appropriate chemicalT HAVE recently framed a valuable oil painting fibres of which have been impregnated with a cellulose processes. and after varnishingitwith gum mastic compound and the surface of which has afterwards Such is an outline of the basic process, which isI find that the canvas has become slack and has been treated with a pigmented cellulose paint, withsimple enough.But whether you can, without prior wrinkled slightly.Can you advise me of a suitable or without a subsequent pressure and/or heat treatment experience, work the process for yourself and make itsolution which I could apply on the back of the for the purpose of obtaining special types of embossing an economic success against the prevailing restrictions painting, thereby shrinking the canvas to make effects.It is in this mariner that the various " hide "is more than we should like to say.The chemicalittaut in the frame ?-W. Henderson (South and " antique " effects are obtained, the treated cloth plant required is very simple and your needs in this Shields). being passed through heavy calender rollers. respect are well catered for by the many firms of chemi- You cannot hope to make a close imitation of leather -cal plant makers in this country.They, however,TO be perfectly candid, it is quite impossible for us cloth by merely using home methods, but you will be ableare working under restrictions and, as you know, steel to diagnose just where you have gone, wrong in to make some such type of material.The basic celluloseand allied products all come heavily within the restric-varnishing your picture.The whole art and technique solution is made by dissolving scrap celluloid either tive influence. of varnishing an oil painting on canvas is a very tricky in "cellusolve " or in a mixture of approximately Your best plan, we think, is to try the process out one.Its success depends on so many different factors, equal parts (by volume) of acetone and amyl acetatein a small way first of all, using a few clean iron or steel as, for example, the age of the picture, the type of paint Unfortunately, these 'solvents are extremely hard todrums.From these beginnings you. willobtain aused, the nature of the " ground " on which the picture get at the present time, but you may possibly obtain aknowledge of the various difficulties inherent in the has been painted, the precise composition of the applied small quantity by going the rounds of the Londonprocess, and this will enable you to decide whether tovarnish and the state of humidity of the surroundings chemical supply houses.The solution of the celluloidproceed in the matter or not.Always, of course, bearand materials.All thesefactors -and others -sum is effected by shaking, not by heat, since the solutionin mind the fact that your final product is not a pureup and determine whether or notthevarnishing is very inflammable. one.To produce pure potassium salts would necessi- The cloth is stretched on a frame, and the solutiontate the equipment of a small chemical work's in itself, Gum masticiscertainlythebestmaterialfor iswell rubbed into the upper side of the material,the employment of at least one skilled chemist andvarnishing an oil painting, but it must be the pure this operation being done twice.For this purpose,various ancilliary workers.Moreover, you have also andunadulterated gum dissolvedinthepurest the solution should have a thin varnish consistency. to remember that in thus entering into potash produc-turpentine to make a medium -strength solution.We After drying (12 hours in the cold) a cellulose paint ortion you would be up against powerful interests which presume that you have attended to these requirements. varnish is applied to the treated surface.One coating would not be inclined to treat your competition lightly.If, however, the solution is too dilute (i.e.contains - is usually sufficient to give a smooth, pleasing effect, We think, therefore, that even before commencingtoo much turpentine) the latter will soak through to and one coating of the paint is less liable to crack thansmall-scale experiments, you should consult authenticthe back of the canvas (particularly if the picture is old two coats.The paint may be either sprayed or brushed. chemical literature on the subject in a good and up-to-and contains numerous cracks) thereby causing the The precise paint and cellusolve solution used by thedate reference library.Only then will you be equippedindr(idual fibres of the canvas to relax and slacken. leathercloth manufacturers is maintained a close secret with the means of sizing up the various problems, The same effect obtains if the correct strength mastic and of course you will not be able to obtain theirtechnical and economic, involved. varnish is applied too liberally.Again, a similar thing results.Nevertheless, with careful and patient working, happens if the varnishing is done under damp conditions, you should be able to produce some reasonable imita- Tanks for Hydrochloric Acid for a canvas may absorb and hold a good deal of water tions ,of the commercial article.The only trouble isCAN you please advise me as tothe beat and vapour. thepresent-day excessive and continual shortage of most economical method ofmaintaining The picture should be bone dry to begin with. materials, so far as the average individual is concerned.a solution of Soo gallons of " cold " hydrochloricThe surface should be given the thinnest possible acid, in bitumen -lined tanks, at a temperaturelayer of varnish, applying it with a small, flat brush Electrical Indicator for Storage Tanks of approximately 6o deg. F.? (preferably of hogshair).This coating should be IHAVE recently installed two storagetanks The tanks are used for pickling wire rods priorallowed to dry before a second (and thicker)coat of for fuel oil of ta' 000 and 6,000 gallons capacityto wiredrawing. Any immersion system shouldvarnish is applied. above4- ground level and T.would much like toprovide for protection of equipment against the Pos-sibly,therefore,inthelightof theabove instal inside an office some 6oft. from the aboveacid. -K. 0. Leach (Sheffield). information, you will be able to find out just where you have gone wrong in the varnishing process. tanks an accurate indicator so as to check dailyYOU do not tell us at what strength the hydrochloric We assume thatthe canvasisperfectly sound the amount of fuel in storage.Would a hydro- acid is to be used, nor whether the acid is of the although very frequently many of these old pictures static gauge be suitable with, say, a gin. bore" pure " or " commercial " variety.In any case, aare on canvases which are anything but sound, and pipeline from each tank suitably connected with abitumen -lined tank will not withstand any liquid, letwhich require renewing -a very difficult and expert tee at the U-tube end so that each tank readingalone an acid liquor, at 6o degrees, for the simple reason task. could be taken in turn ? that the bitumen will soften at this temperature and If such is the cases your best plan is to remove the I would be pleased to have your observationswill slowly " creep " down to the bottom of the tank. canvas from its frame and very carefully to renail it in on this or any other method it would be possible We think, therefore, that, instead of bitumen, youposition.This is a job for two people, one doing to employ. -T. Cuerden (Blackburn). must really meanasphalt,which is essentially a productthe necessary stretching and the other the nailing TNprinciple,ahydrostaticpetrol -levelindicator would answer your purpose, but in actual practice it would possibly give rise to many difficulties, thereby giving inaccurate and unsatisfactoryresults, mainly THE P.M. LIST OF BLUEPRINTS owing to the long connecting line (6oft.) which would be interposed between -the tanks themselves and your " PRACTICAL MECHANICS "12 FT. ALL -WOOD CANOE...New Series.No. 1. 3s.6d. own office. " PRACTICAL MECHANICS " 10 -WATT MOTOR.New Series.*No. 2.3s. 6d. A mach better method, we think, would be an " PRACTICAL MECHANICS" COMPRESSED -AIR MODEL AERO ENGINE.*New Series. electrical one, a modification of which has been put No. 3.Ss. into practice for car use by Messrs. Smiths, and by " PRACTICAL MECHANICS" " SPORTS" PEDAL CAR.*New Series.No. 4. 5s. other people. F. J. CAMM'S FLASH STEAM PLANT.New Series.No. S. Ss. Essentially, with the electrical method a suitable " PRACTICAL MECHANICS" SYNCHRONOUS ELECTRIC CLOCK.New Series.No. 6.5s. float is provided, which float operates an arm working "PRACTICAL MECHANICS" 420 CAR SUPER -DURATION BIPLANE* up and down an electrical resistance of the rheostat (Designedby F.J. CAPIN), Full-size, blueprint, 2s. type.A galvanometer instrument (at any reasonable distance) is wired up in circuit with the rheostat and a Rh. 6d. per set of four sheets. The I-c.c. TWO-STROKE PETROL ENGINE* source of current (battery, accumulator or D.C. trans- "PRACTICAL MECHANICS" MASTER Complete set,7s. 6d. former), so that as the float arm moves up and down BATTERY CLOCK* STREAMLINED WAKEFIELD the rheostat in accordance with the variance of liquid Blueprints(2 sheets), 3s.6d. MONOPLANE -3s. 6d. level in the tank the resistance of the circuit continually " PRACTICAL MECHANICS" OUTBOARD LIGHTWEIGHT MODEL MONOPLANE varies.This variation is manifested by the movement SPEEDBOAT Full-size blueprint,3s.6d. of the needle on the galvanometerdial, thelatter 10s. 6d. per set of three sheets. P.M. TRAILER CARAVAN* being, of course, carefully calibrated in terms of the A MODEL AUTOGIRO* Complete set,10s. 6d. = capacity of the tank in question. Full-sizeblueprint, 2s. P.M. BATTERY SLAVE CLOCK* 2s. - It will be realised that the current need not con- E. The above blueprints are obtainable, post free, from Messrs.GeorgeNewnes,Ltd., Tower House. .g tinuallyflow through the Orcui:.Itneed merely be switched on at the moment at which it is desired Southampton Street, Strand, W.C.2. = er to take a reading, a switch being provided near the dialE An * denotes constructional details areavailable, free, with the blueprint. = for this purpose. April, 1948 NEWNES PRACTICAL MECHANICS 245

It is easier to do this in the case of a small canvas than Your best places of inquiry are :Messrs. Albright both solutions to about 6o deg. C. Then mix them, stir of a large one.Again, you might insert theusualand Wilson,Ltd.,Water Treatment Department, well and allow to solidify. wooden wedges at the corners of the canvas frame and 49, Park Lane, London, W.z ;Sofnol, Ltd., Greenwich, If you cannot obtain stearic acid, the following is an drive them into position.This procedure isoftenLondon, S.E. ;and Burgess Zeolite Co., Ltd., 68-72, alternative formula, but it is not as good as the previous sufficient to take up any stretch in the canvas. Horseferry Road, London, S.W.r. one : On no account apply any chemical substance, oil, In smaller quantities, you might possibly be able to Spirit, r,000 ccs. ;soap chips, 3o grams. ;shellac glue, etc., to the back of the canvas.If you do, theobtain water -softening zeolite material from one or 2 grams. picture will gradually deteriorate.There is nothing ether of the London wholesale chemical supply houses, Heat the alcohol to 6o deg. C. (14o deg. F.).Add like oil for slowly rotting the films of a canvas. as, for instance, Messrs. A. Gallenkamp & Co., Ltd.,the soap and shellac.Stir well until dissolved. Then If the picture isparticularly valuable, we should 17-29, Sun Street, Finsbury Square, London, E.C.2,allow to cool. advise you strongly not to tamper with it further butor Messrs. Hopkin and Williams, Ltd.,16-17,St. to place it in the hands of a good local picture restorer. Cross Street, Hatton Garden, London, E.C.r. White Spirit Varnish His charge should not be excessive for the work entailed. vrLL you please supply me with a recipe for Cut-out for Charging Circuit making a white hard varnish " spirit " as Paper -making you tell me how to make a small dryused for tennis rackets ?-E. Gent (Surbiton). T AM veryinterestedin making paper and 1-,accumulator which will pack into a smallASPIRIT varnish of the type you require can readily A putting in the watermark, and wish to knowcylinder zin. diameter and 6in. long ?I want it be made by dissolving bleached shellac powder in if you can give me a recipe for the making ofto be charged by a 6 -volt dynamo and to operateabout an equal quantity of warm methylated spirit. paper (writingpaper) andtellme how totwo 6 -volt lamps of .3 amps and .04 amps. The spirit should be placed, together with the shellac, incorporate the watermark ? Also, could you tell me how to make a cut-outin an uncorked bottle, the bottle being allowed to I am told that old papers' as well as rags, havedevice so that the accumulator will be chargedstand in a vessel of warm water.Shake up the mass to be " cooked " and stirred up in a vat. at the correct rate and length of time, and how tovery frequently until ithas all dissolved.The con- You might be able to recommend a good bookmake the connections to dynamo, accumulatorsistency of the varnish should be that of thin syrup. on the subject.-K. Morgan (Melbourne,and lamps ?-L. Starkey (Manchester). If it is too thick, add more spirit ;if too thin, add Australia). more shellac.Finally, before use, filter the varnish WE cannot hold out much hopes of successful homethrough fine cloth (muslin), and apply with a soft, flat PAPER -MAKING asanamateurpursuit is a construction of the type ofaccumulator you brush. very difficult job, and there are very few who mention, and consider that you, would be well advised A solution of gum dammar in turpentine also makes everattemptit.Simpleenoughintheory,the to purchase one of the manufactured articles, such as a very good clear varnish.Unless, however, applied procedure is difficult in practice, and itcalls for the the Varley. very thinly, it will take a couple of weeks to dry and a utmost degree of skill and experience.Given this, We know of no type of automatic cut-out which willfurther week to harden. however, and using good materials, there is, for mostensure the accumulator isautomatically, charged at purposes, no better paper in the world, than that of the " handmade " variety, a commodity of the very Finishing French Polish : Bleaching Ivory highest quality which even this present machine age Contacts) 'THERE is a method of finishing french polish- has been unable to displace. ing with dilute vitriol and some kind of The paper is, of course, made by dipping a fine wire chalk instead of the alternative method of spiriting mesh, wooden framed,: into a vat of the liquid paper out. Could you give me any information on the pulp, which latter is obtained by the breaking down of Accumulator subject ? clean rags and other fibrous materials in water.This Also,is there any method of bleaching dis- has to be done mechanically by means of A " beating coloured ivory backtoitsoriginal whiteness engine," which literally tears the rags asunder.To without the tedious processof scraping and some extent you can get a similar effect by the prolonged F,ne wire glass papering ?-W. Picton (Barrow-in-Furness). boiling of scrap paper in water.The usable paper pulp shunt coll. should have the appearance of milk. SOME polishers have a practice ofgoing over the When takenupinthewire -bottomedshallow polished surface with adilute solution of sul- tray the water drains through the wire mesh, leavingArrangement of cu -out in a charging circ phuric acid(vitriol) and then neutralising the acid - behind a wad of fibre.This wad is tapped off the treated surface with precipitated chalk, finally wiping mesh on to a wet pad of hair felt, on which it is allowed (L.Starkey.) away and giving the surface a final rub over with a soft to dry.The resultant mass of formed paper is, of polishing wad.The sulphuric acid strength is about course, highly absorbent, likeblotting -paper.Itis the correct rate and for the correct length of time. AI in 6, i.e.,I part of sulphuric acid in 6 pans of water. then " tub -sized," in which process it is passed through certain amount of supervision is always advisable. We see no advantage in the process, however, which a3 per cent. solution of gelatine (3 parts gelatine A cut-out, which would break circuit when theis said to toughen the polish film, nor do we recommend dissolved in 97 pans of water) containing also a little,dynamo voltage is too low for charging, and would i t. soap and a little common alum to increase the smoothnessclose the circuit when the dynamo voltage is correct Ivory is best bleached by continually wetting with and toughness of the paper.It is again dried and isfor charging, could consist of spring -loaded contactswater and placing in strong sunshine for a prolonged then ready for use. carried on an armature of soft iron, the contacts beingtime, butitis obvious that this method cannot be The watermark (if any) is obtained simply by weavingconnected in series with the accumulator.Opposite'undertaken in very many instances. We observe, too, the required design of the watermark into the wire meshthe armature should be fitted a soft iron pole piecethat you do not state what kind of ivory objects you of the paper -making frame.In this manner, the design,wound with a coil of fine wire connected across the desire to bleach.If, however, you refer to pianoforte n woven wire, is raised above the level of the wire dynamo ; when the dynamo voltage reaches the required keys, the best method (apart from the sunlight bleach) mesh to a very slight extent, and it is this which producesvalue the current and magnetism created by this coilis to make up a paste of chloride of lime and water. the required watermark, the watermarked area of the are sufficient to attract the armature and connect the Acidify this with a few drops of sulphuric or hydro- paper being slightly thinner than the rernainder of thedynamo to the accumulator. On the top of the fine wire chloric acid (dilute) and spread the paste on the ivory paper. coil are wound a few turns of thicker wire which aresurface, treating each key (removed from the piano) There are no books on papermaking from an amateurconnected in series with the contacts; this coil carriesseparately.Two or three repetitions of this treatment viewpoint.Below, we give adist of technical works onthe charging current so that when current flows towill whiten the ivory, but the surface may be a little industrial papermaking.After each title we appendcharge the accumulator the series coil assists the fine roughened.In such instances, the surface should then the pre-war publishers' price.Such books may bewire shunt coil in keeping the contacts closed.If thebe polished by rubbing over with a little fine putty obtained from any good bookseller, such as Messrs. Ed.dynamo voltage falls so the accumulator tends to return powder or whitening mixed with oil. Bryce, Ltd., 54, Lothian Street, Edinburgh, or Messrs.current to the dynamo this current in the series coil A strong, hot solution of oxalic acid will sometimes W. & G. Foyle, Ltd., Charing Cross Road, London,will create magnetism of opposite polarity. to that of the diminish the yellowing with forms of ivory objects, but W.C.z, from both of which firmsalso secondhandshunt coil, the total magnetism will he reduced andits use is not reliable.Also, a prolonged immersion of copies may possibly be obtained : 'the spring will' open the contacts. the ivory object in a solution of sodium carbonate (x R.H.Clapperton :" PracticalPaper Making " part in 4 parts of water) has also been stated to remove (7s. 6d.). yellowing, but, here again, the results are not reliable. R. H. Clapperton and W. Henderson:" ModernSolid Methylated Fuel Paper Making " (21s.). CAN you please supply me with the recipe for A. Watt :" Paper Making" (8s. 6d.). making solidmethylatedfuel ? SmallRadio Metal Locator : A Correction H. A. Maddox :" Paper " (3s.). quantities onlywillbe needed.-W.J.Grove R. W. Sindall" Paper Technology " (ars.). (Portsmouth). In the article on " A Radio Metal Locator," Cross and Bevan " Textbook of Paper Making," which was published in the February, 1948, 5th ed., revised (3os.). TO make " solidified spirit" proceed according to J. Beveridge :" Paper Maker's Pocket Book " (ars.) the fcllowing formula : issue of PRACTICAL MECHANICS, our contri- Spirit, t,000 ccs. ;stearic acid, 60 grams. ;caustic butor made one or two errors in the circuit soda, 13.5 grams. Water Softener Details Dissolve the stearic acid in 50o ccs. of the spirit.diagram.The corrected diagram isgiven T WAS very interestedin the constructionalDissolve the caustic soda in 500 ccs. of spirit. Warmbelow. A details for making a water softener. Will you please let me know if the following would be suitable for making the body ? I have two brass shell cases zoin. by 4in., relics of the 1914 war. Would brass have any harmful RFC, o effects on the water or the basic material and O salt ? - I cannot get the softening medium in Guildford, so will you also let me have an address where it /sr Osc 2^10 Osc. can be purchased ?-G. F. Hall (Guildford). Det. COPPER and brassaredefinitelyunsuitablefor any type of water -softening apparatus, since both of these metals are liable to be attacked by water - softening chemicals and particularly by salt or brine solutions. For ordinary purposes, iron is the best metal to use, and if the softened water is required for O human consumption the iron should not be galvanised, CY that is to say, zinc -coated. O A vessel of dimensions approximately 2ft. by 9in. would, we think, be suitable for your purpose.After cleaning out, this should be filled at the bottom with clean broken glass, then clean coarse rock orflint fragments, then a 'in. layer of coarse sand mixed with broken charcoal fragments.On top of this place a rain. or r8in. layer of the softening material, with a layer of well washed coarse sand above. The vessel must, of course, be provided with a suitable tap near the bottom. Water -softening materials of this class are as yet Corrected circuit diagram forthe radio metallocator published in not easy to obtain. the February issue of " Practical Mechanics." 246 NEWNES PRACTICAL MECHANICS April, 1948

.Mtr,ei$t

GALPINS JEEP ELECTRICAL STORES, 6. 408, HIGHSTREET, LEWISHAM, TAKE UP LONDON, S,E.I3 Telephone: LEE _GREEN 0309. (Near LewishamHospital). TERMS : CASH WITH ORDER. NO C.O.D. PELMANISM MAINS TRANSFORMERS (AUTO and Develop Power WOUND). Voltage Changers tapped 10, LANTERN 20, 25, 90, 130, 150, 190, 210 and 230 volts, LAMPSHADE trainingin 0 ELMANISMisa allat1,000watts, acombination of 34 isameansby voltages can be obtained from this Trans- power. It former, new ex -Govt. stock, 851101- each, whichknowledgeismoreeasily carriage 51,Mains Booster Transformer, acquired,retainedandused; a tapped 0, 6,10,19, 175, 200, 220, 225, 240, - means through which natural apti- and 250 volts at 1,500 watts (new ex -Govt.), expression and 85151-each,carriage5)-. Another 200 tudesfindgreater voltsinput240voltsoutputat2,500 by which individualfacultiesare watts,£71101-,carriage 716. Another, developed.The main ideaisall 2 to I ratio,110 voltsinput 220 volts outputorviceversaat4,000watts, the time on use, for with practice EI21101-, carriage 101-.Another, 230 volts JIB CRANE and use more knowledge comes, and 78'79 input tapped output 40,41,42,44,46, skill, wisdom and power grow. 47,49, and 52 voltsat100 amps., £15 each,carriage 101-; thelattertwo are " First-class " Minds double wound. Another auto wound, SOAP BASKET To -day trained minds are more tapped 0, 110,150, 190, 210 and 230 volts 100 at 1,500 watts,261101- each, carriageSI-. necessarythanever. Alsothey Ditto, 2,000 watts, £7151-, carriage51-. are more in demand.Efficiency is EX -GOVT. (G.E.C.) ELECTRIC FANS. MODEL theneedofthemoment-and 12 volts AC1DC laminated field, complete RAILWAY EQUIPMENT mental efficiencyabove everything with Sin. impellor. New boxed, 251- each, RI'M5 11- post. Transformer to suit 230 volts in- else. To do your job superlatively put 10116 volts at 4 amps. output, 3216 each. well must be the desire and duty of EX -GOVT. (NEW) MAINS TRANS- 4iG every man and woman to -day, and FORMERS, 2001250 volts 50 cys. I ph. input 525101525 volts150 Mlamps. 6.3v. thebest way of making yourself 5 a., 5 v. 3 a. output standard rating, 351-, " first-class " from the point of view post 21,Mains Smoothing Chokes, 10 Hy. 150 Mlamps.180 ohms D.C. Resistance, of personal efficiency is to train your 816 each. Ditto,100 Mlamps., 516 each, mind by means of Pelmanism. post 9d. EX-R.A.F. MICROPHONE TESTERS Pelmanism eliminates the feelings (new). Theseconsistofa FERRANTI of Frustration and Inferiority (and O to450 Microamp21 in.scalemeter many other weaknesses as well) and shunted to I MIA incorporated Westing- houseRectifier,thewholeencased in develops and strengthens your Will - No. 2 SET Power, your Determination and your polishedteak casecalibratedatpresent COMPLETE 0 to 10 volts, 3216 each. I SET with powers of Initiative and Concentra- EX-R.A.E. CRYSTAL CALIBRATORS TOOL tion. UNITS. Type 18 R.A.F.serialNo. and I0a115237. These units contain 100 kcls So why suffer from these failings xstal 2-EF 50 valves and numerous other I EQUIPMENTobtainable from 1/-. any longer ? Whatever your age, items all new and unused, 351- each. Spare Equipment DEALERS ONLY whatever your occupation, SPECIAL OFFER METERS, ALL NEW FROM APPOINTEDwrite to soleManufacturers BOXED. Moving Coil First -Grade to obtain locally Corner, Boreham willfreeyourmind fromthese NEERObleIf una LTD., to Dept. PM. Sterling Instruments, 0 to 20 volts,101- each, or JU Wood, Herts. unhappy conditions and change for 3 for 25/- ;0 to 40 volts, 1216 each ; 0 to the better 'your whole outlook on 10 amps., 151- each ;all tin. scale.0 to 20 volts A.C. calibrated 50 cys., 251- each ; Every time you have life. 0 to 4 amps. Thermo Coupled, 251- each ; 0 to 3,500 volts Electastatic, 351- each, all Half -feesforserving and ex -Service scale. to STOP EX -NAVAL CATHODE RAY RECTI- membersof HisMajesty'sForces. FIER UNITS. These units are new and (Apply for Service Enrolment Form) weigh 90Ibs. Consisting of high voltage condensers,15 volume controls,chokes. approx. 100 resistancesand condensers A True Philosophy allcoloured, coded of marked, valve and Pelmanism is a true philosophy of tube holders (no valves), transformers are included but are for 500 cys., price to clear, living for ordinary sensible people 4216 each, carriage paid. who wishtomakethebestof MAINS TRANSFORMERS, EX - themselvesatall times and under all GOVT. All 50 cys. input 230 volts input circumstances. The Pelman Institute 500101500 volt. at 250 Mlamps. L.T. 5 v. 3 a.,37)6, carriage 316.Another 50 volts has won and held its unique position at 30 amps. output, 751- each, carriage 61-. BRAKE BLOCKS through all wars and worries, trials Another two L.T. windings, voltsat and LINERS andtribulationsduringthelast 10 amps., 2716 each. Another 230 volts input 700 volts at 150 Mlamps., 4 v. 2 a., will pull you up half century. To -day Pelmanism 4v. I a.output, 2716 each, carriage316. smoothly and promptly isappreciatedas much asever. Another 700101700 volts 80 Mlamps., 12 v. The test of timekiasproved the I a., 4 v. 2 a. output, 301- each. Known to thousands of cyclists power of Pelmanism. EX-R.A.F. IFF UNITS.As new, these over the past 4o years for their reliability and long wearing qualities.Supplied units contain 10valvesS.P.41s,Ef 50s. Ask your dealer. The general effect of the training EA 50s, etc., also approx. 100 resistances in various patterns to fit all makes of machine. is to induce an attitude of mind and and condensers, also complete with motor FIBRAX LTD.,2 TUDOR STREET, LONDON, E.C.4. generator, 12 or 24 volts input 450 volts apersonal efficiency favourable to ,,at50 Mlamps. output. To clear, 24 -volt the happy management of life- type, 35)- ;12 -volt type, 4216, carriage 316. Remember-Everything you do is EX-R.A.F. RF UNITS (new)packed, preceded by your attitude of mind. containing 6 valves, all 6.3 heaters, included groundedgridtriode,also a miniature YOUCAN MAKE THESE The Pelman Course isfully de- 24 -voltmotor(universal) and approx. scribedinabook entitled" The 80 resistances and condensers, all mounted on silver-plated chassis, to clear, 451- each, Scienceof Success."The Course carriage paid. AND MAKE is simple and interesting, and takes L .T. RECTIFIERS (NEW), 12 -voltsat up very little time ;you can, enrol amps. output,1016 each ; 12volts at 618 amps. output, 451- each.Transformers on the most convenient terms.The can also be supplied for ch8rging 6 or 12 MONEY book will be sent you, gratis and volts (delivery 10 days from date of order). Knights in Armour post free, on application to prices respectively 251- and 451- each. Make these and other models with the aid ol MAINS TRANSFORMERS(NEW). Indians our Toy Casting Moulds and fast drying enamels. Farmyard Animals PELMAN INSTITUTE, Input 2001250 volts 50 cys. I ph. output Fullparticulars of this fascinating hobby and 350101350 volts at180 Mlamps. 4 v.4 a. Lions (Established over50years) profitablepastimewitheveryfirstorder. C.T. 6.3v.4 a. C.T. 5 v.3a., 3716 each, Elephants 130, Norfolk Mansions, ; Send S.A.E. for full details. ! post 116 ditto, 500101500 v.150 Mlamps. Cannons, etc. Write to -day 4 v. 4 a. C.T. 6.3 v. 4 a. C.T. 5 v. 3 a., 4716 Wigmore Street, London, W.T.

each, post 116 ; another tapped6,12 and Callers welcomed. 24 voltsat10112 amps., 451- each,post PEI MAN (OVERSEAS) INSTITUTES ." PARIS: 116. Auto wound Voltage Charger Trans- PROGRESSTOY CO. LTD. 176Boulevard Haussmann. AMSTERDAM: formers, tapped 0,110, 200, 220 and 240 Damrak.68.NEW YORK :271,North Avenue, volts 250 watts, 451-; 350 watts,551- ; Dept. 7 KIRBYROAD, BLACKPOOL, S.S. New Rochelle.MELBOURNE :396.Flinders Lane. JOHANNESBURG :P.O. Box4928 500 watts, 70/- each, carriage 116.(Please Telephone BLACKPOOL 750 DURBAN: Natal Bank Chambers (P.O. Box note, these Transformers can be delivered 1489).DELHI: 10, Alivore Road. CALCUTTA: 10 days from receipt of order.) 102.Clive Street. April, 1948 NEWNES PRACTICAL MECHANICS 247 A Fine Set Here is a splendid selection of The verdict of many satisfied con- structors using the famous DORSET MODEL RAILWAY CLUB ELECTRADIX BARGAINS Circuits. NONCE orEXPERT.These circuits DYNAMOS. D. 12 volt 10 amp. shunt,, are TOPS. Each manuscript contains 1,400 r.p.m., 24/10q. 70 ;12 volt 500 watt, very detailed instructions, easy to read EXHIBITION black and white drawings, .point to 2,000 r.p.m., 114/1510 ; 24 volt1,000 watt, Point wiring, every step and stage EASTER WEEK, TUES. MARCH 30 to SAT. APRIL, 3. 2,000 r.p.m., 27/1010 24 vols 40amp., described. NO RADIOEXPERI- 1,000r.p.m.,210 ;30volt5 amp., 1,500 ENCE necessary. r.p.m., SS. The work of members of the Model Railway Club, approximately DORSET 2/6CIRCUITS VARIABLE RESISTANCES. Vit. each 3,000 models of locomotives, coaches, wagons, signals and working enamelled tube, with laminated brush gear, A.C. or A.C./D.C. 5 -valve three -wave 14 ohms, 5 amp., new,251- ;61 ohms, superhet. with pick-up. tracks.Free rides behind real steam engines. 6i amp. 51H, 1716 ;50 ohms, 30 amp., ALL DRY BATTERY PORTABLE. enclosed, 401-. 4 -valve, med. and long. BATTERY FOUR.Three -wave super- TRANSFORMERS. Adto 2301110v. tett 1.4or2voltvalves.(A real 85 watt, 251- ;150 watt, 351-; 200 watt, humdinger onshort.) CENTRAL HALL, WESTMINSTER 401- ; 350watt,651- ; 1 kw., £711013. A.C./D.C.. 6 -valve AMPLIFIER for mike and pick-up, inc. pre -amp. Tuesday, 2 p.m. to 9 p.m.Thereafter, IIa.m. to 9 p.m. B.T.H. TRANSFORMERS. 20012301250 volts, 50 cy. input, 2 volts 20 amps, 75 volts DORSET COMPONENTS ADMISSION - Adults 2/3, Children under 14, V-. 6 amps., with 15 taps output, 701-. Carriage speciallydesignedfor above. paid England and Wales. C. Panton, Chassis.Coilpacks, Group Boards. Special terms for organised parties on application to R. METAL RECTIFIERS.12 volts,I amp., 1.F. Transformers.Chokes,Mains Transformers,Speakers,etc. I62a, Strand, London, W.C.2. 1216 ; 12 volts,ISamy.,401-; 36 volts, - " Hot Spot " battery soldering outfits. 10 amp., 551-.; 6o volts, I amp., Mt- ;75 Send Id. for list.Theoretical circuits. volts, 6 amp., £4. 21d. each. SOLENOIDS.12 voltRotax, willpull WELDONA lion.lin.,616 ;heavySolenoids, 24 volts, RADIO ACCESSORIES LTD. to lift14Ibs.,Isl.. NTIFORI5 MOTORS. 110 voltD.C.1/12 h.p. Shunt 38, Gloucester Road, BRIGHTON. TYPE ML7. wound,251- ; a fewsimilarmachines, 31" HEAVY DUTY LATHE needing repair,110v. D.C.,1216, postage ELECTROTORS3v. to 6v. 116 extra. The finestLathein itsclass. CIRCUIT BREAKERS. N.C.S., 71 amp. Type 240withoutbase 816 A.C., enclosed type, 211, Type 242 asIllustrated 1016 Extensive Post 4d. BATTERY CHARGERS. 230 volts A.G. range of for 6 or12 volt accumulators ;send for accessories. special leaflet and keepyour car accumulator in good condition while not in use. LAMPS.I watt Neon lamps, 230 volts, miniature type, with small bayonet cap, 316, postage 9d.extra ;5 -watt Standard Neons, bayonet cap, 311, postage 9d.; letter plate Neons with E.S. cap, 216, postage 9d. SPARK COILS. Ex-G.P.O.6112 volts D.C. input to give 3, in. to lin. spark, 251-; large 4in.coil on polished base in new MYFORD ENGINEERING COMPANY LIMITED condition, 12 volt, £1211010. HAND MIKESinmoulded bakelite case, BEEsToN NOTTINGHAM 'Phone: 54222 (3 lines) 416 ; transformer, 416 ; Tannoy Hand Mike, multi cell Carbon types, withneat switch 07.1490 in handle, 1216.Special transformer, 816. PREPAYMENT House ServiceMeters, LABORATORY Chamberlain andHookham, 230volts, APPARATUS & CHEMICALS 10 amp., for II- coin, £4. MODEL ENGINEERS HAND COMBINATION Telephones, STUDENTS' PRICE LISTS FOR THE TURNER : ex-G.P.O., moulded bakelite, sound power 2d. type, with cord and plug, 211, Lathes, 3t and 41S.S. Bench Millers.Drilling Machines. VICSONS & CO. RELAYS. G.P.O., enclosed type,1,003 148, Pinner Road, Hand Bench Shaping Machines. ohms, 216 ;30 ohms, 2 make and 2 break Harrow, Middlesex. FOR' THE WOODWORKER : contacts, 216. 'Phone : Underhill 0906. FANS. 110 volt D.C. tablefans,10in. Wood Turning Lathes, 2 and sr centres.4in. Planers.Saw bladeandguard,RI- ; 220voltD.C. Benches.Sanders.Spindle Moulders. table fan,10in. blade and guard, 551-. CHEMISTRY APPARATUS METERS. IroncladA.C.voltmeters, Pedestal Jig and Fret Saws. G.E.C. 4in, switchboard, 0.60 volts,451-. Send Stamp for Ammeters tomatch. 0-40 amps.,451-. COMPLETE PRICE LIST Perspex -All sizes and coloursinstock. Frequency meter 40160 cy. Crompton F.G. Ironclad switchboard, 50 volts6iin. x 6iin. Special x 4in.with lamp on top to illuminate dial, £51510 ;transformer for 230 voltsA.G., Offer NUTTALL'S (LATHES) LIMITED, 35/- extra. Ammeter to match, 0-50 amps., Bunsen MANSFIELD, NOTTS. A.C.,751, Voltmeter tomatch,0-75 Burner volts A.C., 651,D.C.moving coil, Elliott Tripod and voltmeter,31in.,panelwithback con- ELECTR IC ENGRAVERS. -Powerful nection,1301260 volts, 301-. Useful Remote Contactor. New, with many instrumentsin,cylindricalcase, on Glassware useful items including luminous dial stand with spring attachment and TELEPHONES. Wall type constructors' and pointer, 3 amp. toggle switch, two switch.Suitable for dog collars, tool parts, ex-G.P.O., comprising cabinet 8in. x 12/6 relay bobbins wound 3 ozs. clean enam- marking, etc.,4-6 volt model, price 6in. x 3in., bracketmike, transformer and Post Paid. elled copper x 36g. wire, two Platinum 50/- ;A.C. Mains model, 200-240 volts, condenser,mag.bell,switch -hook and contacts, cable leads,etc. 3/6 each. 60/- A.C. Engraver only50/-. contacts,hand mag., ringerP.O.type 3 different Multi -point Switches, silver TELEPHONE SETS,comprising 2 BECK(Scientific Dept. A) contacts.3 for 2/-, 7i0 doz. G.P.O. hand phones, 2 bells, 2 pushes receiver terminals and connection diagram, 10 -way Terminal block and connector, and 80ft. twin wire.Price 65/-, post 351- perpair. 60 HIGH STREET, 30 screws, 1/- each,6 for 5/-. free. SingleInstrument,25/6. Hamofil heat -resisting rubber covered 6 inch Brass Brackets lin. thread,1/9. BATTERY SUPERSEDER. 6 volts D.C., Stoke Newington, London, N.16 copper connecting wire.12 'yds.2/-. S.B.C. Fancy glass shades 1/9. Circular input 230 volts 40 m.a. D.C. output, for Peribraid sleeving, finest quality, high resistances on china base 10 ohm..2/-. Radio receivers, 51in. x 311n, x ball voltage, various colours, 1 m.m., 1.5 Screwplates for threading0 2 4 B.A. 4/6. bearings, model finish, 551, m.m. 4d. yard. MOTOR. -4-6v.dry batterydriven, Bakelite bobbin wound IIozs. clean well made, powerful, 11/6.Illustrated TERMINALS. Mk. III solid brass double MAKE MONEY IN usable 36 s.w.g. enamelled copper wire. list,6d. Carbon Diaphragm terminals with nuts and washers, 716 dozen. 1/- each,10/6 dozen. 1/- each and carbongranules 6d.packet. YOUR WORKSHOP Used ex-R.A.F, low resistance earphone BATTERYCHARGERS FOR A.C. BellingLee platedor brass,5/-dozen. with switch. 2/6. MAINS. FOR CHARGING 2 -volt accu- Heavy insulated Belling, 101- dozen. SETS of CLEAR CONSTRUCTIONAL NewS.G. Brownex -Army high mulators at I amp. Parts with diagram, DIAGRAMS and instructions for resistance headphones, complete with 12/6. Complete 21/8: Postage 10d. MAGNETS. D.C. Electric magnets, weight BUILDING YOUR OWN headband and leads.12/8 perpair. FOR TRICKLE CHARGING CAR 10 oz., lift on 2 volts lilb., 4 volts31b., 6 (1) TOY, MODELor WOOD- New U.S.A.singlesmall earphone, CELLS, parts with diagram.Output volts 41b., new, surplus, 716 each. Permanent WORKER'S LATHE, 3/8. 1,000 ohm:; resistance.5/6. 11 amps. for 6v. cells,30/- act.For powerful flat bar magnets, 2iin. xlin. x (2) Power or foot CHINEtreadled3/8.rive FRET New U.S.A. high resistance headphones, 12v.cells, 35/-set. 118in., drilled 2 holes each end, and any pole JIGSAW MA , Complete with headband and lead. 12/6' Largersizes quoted for. per pair. MINIATURE HEAD- pieces, 21- pair.The wonder Midget mag- (3) Ball bearing Table Model CIRCU- ,As above. but special lightweight with PHONE. Reproduces nets.Alni perm.steel disc. ;518in. diam., LAR SAW, 3/8. detachable rubber ear guards. Com- equal to best 'phones. 318in.thick, with 311 6in. centrehole, 316 (or 9/- for the three.) plete.15/-per pair. Fits into ear, does not each. Large stock of Horseshoe magnets. ALL these well tested, simple machines All above postag, extra. require headband. Two Sendforspecial MagnetLeaflet, "P.M." can be built EASILY from READILY nipples large and small OBTAINABLE PARTS AND Send S.A.E. for list of insulated copper 10 ohm or 1,000 ohm. Please include postage for mail orders. MATERIALS ONLY and will turn out wires, screws, nuts, tags, Ebonite and Blackorfleshen- 1.01 Saleable articles for the shops and laminated Bakelite panels, coil formers, amelled. 4ft. cord. market.Prompt, posting. etc., etc. Price 30', ELECTRADIX RADIOS ECONOMIC ELECTRIC CO., P. M. BARHAM, Bridge Avenue, POST RADIO SUPPLIES 214, Queenstown Road, London, S.W.8 St.. Sampson, Guernsey, C.I. 33 Bourne Gardens,London, E.4 64, LondonRoad,Twickenham, Middlesex. Tel.:POPesgrove 1318 ® Telephone :MACaulay 2159-giagallm 248 NEWNES PRACTICAL MECHANICS April, 1948

Part of the charm of rural England is the rich music of its place names.Who could fail to be delighted by slid% a name as Barton -in -the -Beans, a tiny parish in Leicestershire,justnorthof Market Bosworth.There are plenty of others, equally charming. You may never have heard of them ...

t3UT EVERYONE'S HEARD OF DUNLOP

zi.ozooteatatefitorelf%g-ei Zge"sea,

71-1/321

TOY -CASTING MOULDS Modelcraft's FINE NEW MIDLAND INSTRUMENT Co. PLANS FOR A 36" M. Y. A. RACING Offer the following brand new Ex -Gov. -DEEP CUT surplus gear. YACHT. -Comprise3 sheets of drawings CAMERA CONTROLS TYPE 35, and 2 of instructions covering Soldiers,sailors,airmen,ships, includes 12-v. motor operating 1to 'planes, tanks, cars, farm animals, 50 -sec.exposure timing 'device, also twoalternative methods of 8/6 exposure counter 0-125,etc. etc.,in hull construction. POST Casting mould; deep wild animals and keepers. Sample wood transit cases, 25/-, post 1/4. 4d. cpt. Battledress ENGINE DRIVEN GENERATORS Soldiers, Aeroplane, mould 3,6.Plastercraft Metal (D.C. dynamos), fitted shaft, output Farm -end WOO Moulds, -Wall plaques, galleons, 12-v.at 750 -watt,30/, carriage 5/-, Animals. Cars.etc. Ditto, output 24-v. at 1,000 -watt, 40', Modelcraft's PLANS FOR AN Stamped envelope brooches,dogornaments,etc. carriage 10/ -- forlist.Illustrated AMPLIFIERS, contains two valves, AMERICAN TYPE(' DAYTONA ') Catalogue 60 Samplemouldofbrooch3/6. triode and Q.P.P., four transformers, 33" MOTOR CRUISER. -Foursheets of key switch,on/off switch,resistors Germanflatmoulds from 3/6. and conds..etc.Operates from 2-v. drawings (23in. x 36in.) and S.A.E. for List.6d. for Illustrated and 120-v.Ideal for microphone, pickup instruction sheet giving de- 10/6 or 2 -way loudspeaking intercom.Size tails of the bread-and-butter Catalogue. 7in. x 5in. x 41in., supplied in Wood POST transit cases with instructions.30,' - hull construction. 4d. NUTHALL, 69, ST. MARK'S RD.. post free. FLASHER MOTORS TYPE " E," HANWELL, LONDON, W.7 contains 12/24-v. motor fitted gearbox, final,driveoperatescamswitch. suppressor, etc., 20/-, post 1/4. Modelcraft's PLANS FOR A WORM DRIVE MOTORS, 12-v. A.C./D.C., takes 4 -amps. HOME WATERS TYPE (' WALTON ') fittedgearbox, powerfulfinaldrive JUBILEEHOSE CLIPS 1,000-r.p.m.,25/-, post 1/4. MAINS MOTOR CRUISER. -Oneof our most MOTORS, 200/250-v. A.C./D.C. at The long -life approx. 1 -amp, fitted shaft, ball -bearing, popular plans, the model is 30/-, post1/4. PUMP MOTORS, designed to be powered by 7/6 clip with the 12/24-v.A.C./D.C.fittedcentrifugal pump for liquids only, delivery at 24-v. either clockwork or electric POST ever -tight approx. 7-10 g.p.m., 35/-, post 1/4. motor. 2d. grip STARTERS TYPE " A," contains two heavycurrentsilvercontact TheBest Known relays, 12/24-v. in bakelite case. 2/6, For post 1/-. TheHallam ELIMINATORS, A.C. input 200/250-v., Modelcraft's COASTAL Radiator Joints, D.C. output 120-v. 30-m/A.Fitted neon CRUISER CONSTRUCTIONAL Air, Oil and 'SuperNine- Engine stabilizer, etc.Far superior to civilian Water Host type eliminators, 40/- carriage paid. KIT. -Based on aeromodelling principles, Joints SELECTOR SWITCHES, 12/24-v. we have put togetherthis EASILY MADE FROM OUR CASTINGS, impulses and homes, operates 4 -way We guarantee a Yaxleyswitch, 3/6.Ditto,fitted lightweight kit which yet gives I 7/6 Tight Joint flexible shaft from rotating wheel. 5/-. a thoroughly staunch hull. POST J. HALLAM & SON Either 9d. postage. L. ROBINSON & Co. MOVING COIL. METERS, 211n.sq. 4d.1 UPTON, POOLE, DORSET. flush. 5 types, 0-20-v., 0-300-v.. 0-5-m/A., 25, London MINIATURE PETROL ENGINESfor 0-150-m/A., 20 -0 -20 -amp., all7/6 each, YACHT & POWER BOAT FITTINGS Chambers, Aeroplanes, Boats and Race Cars. post 6d. GILLINGHAM, KENT ALTIMETERS(aneroidbarometer ARE NOW AVAILABLE AGAIN. Send 6d. for New List. movements) 10/-, post 9d. Oxygen flow indicators, 1/6, post 4d.All -dry batteries, 90-v. plus 14-v., 3/6, Post 9d. NICKEL PLATING ADANA PRINTING MACHINES Bell cells 11-v..2/6. post 9d. Print in the odd hours with an Also hundreds of other interesting 1/. post free.MAGAZINE & LISTNo. 5 Complete Equipment, Including Nickel Adana -still the most absorbing Radio,ElectronicandMechanical Anode, Plating Salt, etc. Full instruc- of crafts. No.1 ICS items, send for our new March/April Gives details ofcver 450plans,pianbooks, etc. tionsforPlatingOrnaments,Car Machine24.10.0. lists, 2d. with s.a.e. Fittings, and all Metal Parts.Flash - No. 2 II/S Machine Orders over 30/- post paid. Our C.O.D. lamp battery only required. 29.15 . 0.Will pay service is cancelled for the moment. Price 151-, post tree. for itself In a month or Modeleraft Ltd.. two. Sendforillus- HOLROROW to CO., tratedfolderto Dept. MOORPOOL CIRCLE. (L), Grosvenor Road, 71, VVeymouth Bay Avenue. P.M. 10, BIRMINGHAM. 17. Weymouth. Adams (Printing Machines), Ltd., Tel : HARborne 1308 or 2664. London, S.W.1. 15/18, Church St., Twickenham, Middx April, 1948 THE CYCLIST

THE All letters should be addressed to theEditor," THE CYCLIST," ld George Newnes, Ltd., Tower House, Southampton Street,Strcind,London, W .C.2. Editor : F.J. CAMM Phone :Temple Bar 4363 Telegrams : Newnes, Rand, London VOL. XVI APRIL, 1948 No. 313

Comments of the Month By F. J. C. DiamondJubilee of the Pneumatic Tyre NO invention has made such a profoundthe cover to the rim by means of endless wiresevent, but in this he failed, but he succeeded impression upon civilisation nor beenimproved the design and fortified the positionin winning all the remaining cycle events. responsible for such change in the habitof the Dunlop patent ; nor Woods the inventor Notwithstanding the claims of a so-called of the people of the world than the pneumaticof the tyre valve, that simple device whichhistorian who, for years, exhibited a machine tyre.It paved the way for the perfection ofenables the tyre to be quickly inflated, and isin his so-called museum with the specious the bicycle, the motor cycle, the motor car,practically the same to -day as it was when firstand quite fictitious claim that it was the bicycle the aeroplane, and all vehicles which run onoriginated. on which Hume won the first race, we have wheels. Dunlop was born at Dreghorn in AyrshireHume's authority for saying that the machine Its invention was as momentous as that of(appropriate name !) in 1840, and was educatedwas destroyed.As thisspurious machine the wheel itself.This year the pneumatic tyreat the Irwin Academy under Dr. White,has been bequeathed to the City of Coventry, celebrated its Diamond Jubilee, for it wasfrom whom he acquired his knowledge ofwe made it our business to inform the appro- on February 28th, 1888, that pneumatic tyresmathematics.He enteredtheVeterinarypriate authorities there of the facts.Itis were first used.Although there had been aprofession as quite a young man, qualifyingunlikely that the machine will be exhibited previouspatentforpneumatictyresbywhen he was 19.On obtaining his degreeas Hume's bicycle.Hume took shares in the Thompson,' it was John Boyd Dunlop whohe went to Ireland, where he settled in Belfast,Dunlop Company's original issue. diligentlyappliedhimself tothe taskofin which city he invented the tyre. An amusing aspect of the history of the fitting pneumatic tyrestothe wheels of When he invented and made thefirstpneumatic tyre is,as can be expected, the bicycles and tticycles.The jubilee has beenpneumatic tyre he had never ridden a bicyclestupidattitudeof theNationalCyclists' fittingly celebrated at the premises in May'and there was not a rubber factory in Ireland,Union at the time.Dunlop was declared Street, Belfast, where the tyres were inventedyet he made the first practical air tyre for hisby that body to be a professional cyclist, and and made, and at Fort Dunlop. son Johnny's tricycle.He made it out ofso were the remainder of the directors of The Lord Mayor of Belfast laid a wreathordinary sheet rubber and canvas, his onlythe Dunlop Company.Dunlop could not too' being a pair of scissors. ride a bicycle at that time ! on the May Street Memorial to John Boyd The first advertisement for Dunlop's great Dunlop, and in a speech paid tribute to his invention appeared in an Irish journal dated work and the pride with which Belfast claimed December 19th, 1888.It said : Dunlop as a citizen. " Look out for the new pneumatic safety. Tyre manufacture to -day gives employ- Vibrationimpossible.SoleMakers,W. ment to millions of people and comfortable Edlin & Co., Belfast." and enjoyable travel to many more millions. Robert Carlisle, now 84 years old, who First Appearance in the South helped Dunlop to make the first pneumatic THE first appearance of pneumatic tyres tyre, placed a wreath on the Fort Dunlop in thesouth of England was at the Memorial.Mr. Carlisle is the oldest Dunlop Spring Sports of the Surrey Bicycle Club at employee. Kennington Oval in April, 1890, when two In our issue dated July loth, 1938, we machinesso fittedwereused. Frank devoted the whole of that issue to the history Shoreland, heavily handicapped and riding a and development of the pneumatic tyre, for geared Facile, won from a short mark with it was, of course, in that year that it celebrated such ease that the merits of the pneumatic its jubilee.In that issue we said, and we now tyre were quickly recognised. repeat, that Dunlop has indelibly inscribed Tyres in those days were costly, and the his name on the walls of Valhalla, among competitor to the pneumatic was the cushion those immortals who have benefited civilisa- tyre.Itwasfound,however,thatthis tion, for the pneumatic tyre supplied the punctured more easily than the pneumatic. missing link in what was in itself a great in- There were also stuffed cushion tyres. vention-thebicycle. The bicycle intro- A pair of pneumatic tyres in 1888 cost £3. ducedanew form of transportreadily The reduction in vibration enabled much Robert Carlisle, now 84 years old, who helpedlighter machines to be built, and the weight available to and within the means of h11.John Boyd Dunlop to make the first pneumatic It has done more than anything else to improve of a bicycle gradually fell from about 7o1b. tyre, places a wreath on the memorial to him atto 261b.The first repair outfit was marketed the fitness of the human race, and to increase Fort Dunlop. its longevity. in 1891 by A. J. Wilson, who was closely associated with the early days of the pneumatic Dunlop's patent is dated July 23rd, 1888,First Success in Racing tyre.Wired -on tyres were first produced in and, of course,it amused the technicians THE pneumatic tyreachieveditsfirst1893 under the Welch Patents and they of the period, who still believed that nothing success in racing before a sneering crowdrapidly replaced the beaded edge tyres. would oust. the solid tyre.Famous cyclists,at the Queen's College Sports Meeting at such as George Lacy Hillier (aptly termed theBelfast, held at the North of Ireland CricketEarly Pneumatic Tyres apostle of lost causes because of his oppositionClub's grounds on May 18th, 1889, whenIN the early pneumatic tyre it was necessary to the safety bicycle, and other improvementsWilliam Hume won the firstrace ever to to lift the strip of canvas which covered totheOrdinary)vigorously opposed thebe ridden on pneumatic tyres. the edges of the outer cover, unstick one pneumatic tyre in speeches and in print, There were four cycleraces, and afteredgeforabout 'ft., usingnaphthaasa whilst many others endeavoured to getitwinning the first two, Dunlop congratulatedsolvent, cut a slit in the wall of the canvas suppressed in racing circles.In this latterhim and suggested that he had done verybag and so gain access to the inner tube they, for a time, succeeded. Others, of course,well for the day.Hume then went on to winbefore a puncture could be repaired. contributed to the success of the pneumaticthe third and fourth races !The results The early pneumatics as sold up to 1893 tyre. obtained by Hume so impressed Harvey Duconsisted of an air tube completely enclosed We must not forget Harvey Du Cros, theCros that he left the meeting after the firstin a canvas bag which was wrapped round financialgenius behindtheformationoftwo races and got to work on schemes forthe rim, the whole being covered by an endless the Dunlop Rubber Co.;Charles Kingstonexploiting the idea.Shortly afterwards Humestrip of vulcanised rubber, thickened on the Welch, whose patent for the method of fixinewent to Liverpool and entered a scratch mile (Continued on pap 52.) 50 THE CYCLIST April, 1948

engine and a one gallon tank and the drive is by beltNew Members for Doncaster Club and pulleys to a chain onALF MARTIN, thewell-knownYorkshire Road to a sprocket on the front Club rider, with his wife, Mary Martin, a national wheel.The doctor claimstitle holder, have both become members of Doncaster PARAGRAMS that his cycle can now doWheelers' Club, and will take part in racing events for 12o miles to the gallon and the club next season.At the end of t947 the club has a range of speeds from membership had increased tot IIand a successful six to 42 m.p.h.Although season is anticipated. havingtheengineover the front wheel would appearRide Him, Copper ! to make the machine rather APETERBOROUGH policeman,cyclingsedately unmanageable, the inventor along, and keeping a sharp look outfor any claims that it can be ridden law -breakers, suddenly sprang into action and gave perfectly at all speeds. a five-minuterodeoexhibition when a milkman's horse ran away with its car.Pedalling furiously, he Any Older Club? chased and overtook the runaway and then, riding with PETERBOROUGH Cycl- one hand on the handlebars he managed to grasp the ing Club, which has just dangling reins.He was dragged for a considerable celebrated the seventy-thirddistance,but he kepthisbalance andeventually anniversary of its founda-managed to force the excited animal to a standstill. tion,is claimed by members to be practicallyHis Work Appreciated the oldest cycling club in A T the annual general meeting of St. Neots and the world. Towards the end" District Cycling Club, held at St. Neots, Hunts, of last century club members the club handicapper, Mr. C. H. Paget, was made an used to ride more or lesshonorary life president of the club in recognition of sedately along the bumpyhis services.Arrangements are also being made to 11-110itv,\;: roads wearing right -fitting present him with -an illuminated address and reference uniforms and pill -box capswas made at the meeting to his good work for the club like a kind of Boys' Brigade. over a long period. The Peterborough Club, in i881, was presented with d bugle as winners in a com-Fifty Years In Business petition for the most smartlyAFTER carrying on business as a cycle dealer for gy the WatertfalasK. turned out club and some 5o years in Coney Court and Bridge Street, membersalsotookpart Brigg,Lings, Mr. Frank E. Lee, of Scawby Road, in Queen Victoria's Jubilee Brigg, has died at the age of 78. He was born in Bir- Kersey procession. During 1947,mingham and moved to Brigg to commence business club membership increased on his own account in the early days of cycling. by 50 to 142 and 23 club records were broken during Above the Law? the season. AS quite a number of cyclists have discovered, Halt The King and Queen as Patrons Fold It Up signs are put in the streets to be observed, but King and Queen have granted theirAFOLDING patronage bicycle,which,itisclaimed,can a St. Ives (Hunts) Rural District Councillor evidently 'THEto the Cycle and Motor Cycle Show to be held even be sent -by rail without finishing its journefhas other ideas.He was motoring in Peterborough at Earl's Court from November 18 to 24, as a complete wreck, is being produced in quantity bywhen, according to a policeman, he passed a Halt sign a firm of cycle manufacturers at Westfield, Mass. at 15 miles an hour.He duly appeared before the It is called the Columbia Compax and is designed on Peterborough Bench, and told them :" I worked with Large Scale Operations the lines of those folding bicycles used by paratroopersthe police through the war years. This would not have A BEDFORD man who was sentenced at the Boroughduring the war.The handlebars fold downwards andhappened in my own county. They all know me and I Police Court tosix months' imprisonment onthe frame folds back upon itself so that both front andam sure my word would have been taken." The chair- each of two charges of cycle -stealing, asked for 2i rear wheelslietogether.The folding -up operationman told him he had better be careful what he said other cases to be taken into consideration and it appeared takes only a few minutes and no tools are required. and must not regard himself as having in Peterborough cycles at the rate of approxi- the immunity which he claimed to have in Hunting- mately one every fortnight.The man told the police that he stole the cycles to get money, generally whileNot So Good donshire. he was " in drink." Up to the date of the hearing onlyMONMOUTHSHIRE Policerecentlycarried out six of the stolen machines had been recovered. a check of 18i cycles used by scholars at theStarted Well Monmouth Grammar School, but out of the totalD ON MEADWELL, of Melton Mowbray, member number inspected they were only able to pass 27 as AN. of the East Midlands Clarion Club who is with Celebrations, in1948 the British Olympic Games team in South Africa, began ANOTHER Yorkshire club, Brodsworth Racing Club,being fit for the children to ride in safety. in fine style by winning the half -mile handicap from will celebrate itstwenty-first birthday in1948. scratch and setting up a new South African record of and plans are being made to mark the event and to make Learn from -4IteYoung 56.7 secs.The event took place on an asphalt track the coming season a special one in the club's history. at Bulawayo, Rhodesia. This year the club is introducing youth championshipsI TRMSTCT (Lanes) Road SafetyCommitteeis suggestingthatgrown-upcyclistsoughtto of 88oyds. and to miles and a " best -all-rounder' watch the way in which the local children manage competition for junior members. Other events plannedtheir cycles if they want to learn good road sense.Fairies About? include track championships of 88oyds. and five miles,Altogether, Urmston child cyclists have received 15 A CAMBRIDGESHIRE cyclistevidentlybelieves 'time trials of to and 25 miles and a rough-riders'out of the 35proficiency certificates awarded in a"that fairies are on the road now and again, apart trial, competition organised by the National Safety First from those who accompany male club members on their Association.Special instructors examine the children's runs and at the same time, add a little brightness to the New Yorkshire Club bicycles and give short lectures on maintenance and countryside. He said he left his cycle outside a public ANUMBER of cyclists in the Rossington districtof road sense. house without a lamp on it but when he came out Yorkshire, some of whom have previously been again there was a nice new lamp which had materialised members of Doncaster, Clarion C.C., have formed from somewhere. He made no enquiries but rode away their own cycling club.Ithas been named TheWell-earned Retirement and a week or so afterwards he was charged with Rossington Road and Path Club and plans are beingMR. A. FOSTER, senior partner in the firm ofstealing the lamp and was fined La, together with made for its first year of life. Mesys. A. Foster and Son, cycle dealers, 26, 123.Costs. Wood Street,Earl Shilton,Leics,has retired after Miracle Operation on Cyclist 5o years in the business.His two sons, Mr. C. A.Doncaster's Biggest Foster and Mr. H. Foster, will carry on the familyAT a meeting between.officials of the South Yorkshire m R. HAROLD BLAKE, of Kettering, chief reporter business. on the staff of the Kettering Evening Telegraph N.C.U. and Mr. Rupert Todd, manager of the and formerly a prominent member of Peterborough Gaumont Cinema, Doncaster, arrangements have been Cycling Club,. is reported to be making good progress made for holdingDoncaster's biggestroller -racing Can He Prove It? competition.Itis planned to hold the event on the following a miracle operation in a hospital at St. Louis,ThURING the war a glib explanation of the increasestage of the Gaumont during the period from April 19 Missouri.Mr. Blake,asufferer from Parkinson's1-in cycle -stealing was that Servicemen took themto April 23, and good support is expected. disease, had become so affected that he could neithertemporarily so that they could get back to camp. Now walk nor use his right arm, and he was told by thethat the war is over and many men out of uniform, it is specialists that he could not be cured.. However, hebeing suggested by the Chief Constable of the Holland In Business37Years read in a magazine of the new .operation evolved by andivision of Lincolnshire that the habit continues.He THE death has occurred at his home, 95, London American surgeon, on a part of the brain to break uptold Holland County Council, in his annual report on Road, Boston, at the age of 6z, of Mr. Frederick the paralysis, and he decided to make the trip to America.the year's crime :" During the war, when there wereVictor Walker, for 37 years a cycle dealer in business He is now gradually learning to walk again and to use a lot of troops in the area, it was expected that cyclein High Street, Boston. After serving an apprenticeship his right arm and if all goes well he may even be cycling thefts would increase. This, infact, did happen. with a Lincoln cycle dealer he went to Boston in 1903 once more. He is the first Englishman to undergo this Then there was a lull and now it looks as if those menand later established the present business in High operation. coming from the Forces arc looking for cycles onceStreet. Mr. Walker took a great interest in local activities more."He added that the abolition of basic petroluntil his health began tofail about twelve months Paid for Pleasure may also have had some effect. before his death. educationauthorityhas MIDDLESEXdecided that county an allowance of fifteen shillings a term shall be paid to all schoolchildren in the countyHigh Hopes Quarter of a Century with J. A. Phillips over II years old who cycle to school and live moreMR. JOHN DRAPER,secretaryofKettering TWENTY-EIGHT employees of J. A. Phillips and than two and a half miles from school.Normally Friendly Cycling Club, forecastat the club's Co., Ltd., of Smethwick, Birmingham, received such children are entitled to free travel, and itis feltannual dinner and prize -giving :" Itis not an idlegold wristlet watches in recognition of 25 years service 'that if such children prefer to cycle instead they shouldboast, but within the next two years we hope to havewith the firmata dinner held in their honour on somebody worthy of representing Britain."Although Monday, February16. receive some allowance for the upkeep of their machines.the club only came into being in t9.45, much progress Altogether, over 6o watcheshave been awarded has already been made.Practically all the members since the firm's inception to employees with a quarter Powered Cycle are under z5 years of age and they are showing theof a century's service.Thirty-eight of the previous AN American doctor, whois an amateur mechanic greatestkeenness,especiallythe17 -year -oldrider watch -holdersstillworkatPhillips',representing in his spare time, has converted hisbicycle towho, by mistake, covered to miles more than he need 1,zoo years service between them. The male employee power propulsion.It looks rather like a tradesman's have done in the race to decide the club championship.with the longest service is Mr. W. J. Underwood who Kr. cycle, having a box about r8in. square fixed aboveThis rider did not win the championship, but he didhas done over 49 years, while Miss G. A. Williams the front wheel.The box contains a a h.p. petrolcollect five other awards during the season. with 33 years is the longest serving female employee. April, 1948 THE CYCLIST 51 AroundtheWheelworld By ICARUS Association,an inscribed testimonial and aThe Duke of Windsor on Cycling Bidlake Memorial Plaque cheque. The Plaque was inscribed with the MY congratulationstoR.H.HarrisS:R.R.A.'s thanks for deVoted services. The THE Duke of Windsor, in his memoirs, on being awarded, by theBidlakePresidentof theAssociation,J.Dudley recentlypublishedinAmericaand. MemorialTrust,theBidlakeMemorialDaymond, Was in the chair. serialised in the Sunday Express, has the Plaque for 1947 for his victory in the Ainateni The toast of the AssOciation was proposedfollowing to say on the subject of cycling : Sprint Cycling Championship of the Worldby W. H. Townsend, who paid fitting tribute " I learned about war chiefly on a bicycle. at Paris on July 27th, 1947.Hitherto I haieto its work. The number of affiliated clubs,I was constantly back and forth between various quarrelled with the decision of the Trust insaid. Percy Hugget, the secretary, was nowheadquarters, and although entitled to a staff awarding the Plaque for events or for reasons42, nearly double the 1947 total.Present atcar, I seldom used one within our area. whichIdo not consider meritorious. Ithe dinner were members of the Norwood " The motor -cars of the brass -hats honked maintain that if nothing worthy of perpetuat-Paragon, the AddiscOmbe, Kentish Wheelers,infantrymen off the road into ditches, splashed ipg Bidlake's memory has occurred during theVegetarian, Belle Vue, Polytechnic, Dulwichmud, and, even under the best of circum- year the Plaque should not be awarded forHamlet,Catford,Balham,KentRoad,stances, were an irritating reminder of the that year.To fish round and find someRedhill and Southern Road Cycling Clubs.relative Comforts of staff life. flimsy pretext for awarding it, such as for theI noted also Arthur Slade, Charles Lawton, " My green Army bicycle was a heavy, invention of a split pin, is to besmirch theStan Butler, Alan Gordon, Monty Southall,cumbersome machine, which was tough to honour of those who have justifiably meritedCharlie Davy,W.G. Paul, J. Brereton Summers,trundle through the mud. the award.Harris has certainly done that,Tommy Hall, E. Coles -Webb, H. H. England, " But on itIpedalled hundreds, even and I shall be present to congratulate him inR. B. Coley, Harry Miles, Frank Southall,thousands, of miles collecting material for person long before the next issue appears. S. Amey, W. Gibson, and J. H. Wallis. Anreports,insfrectingcamps,andmeeting excellent evening. thousands of people. Chiltern Road Club " My brother officers laughed at me for T.W. GRIFFIN, 9, Lime Avenue, High preferring this hard way of getting around, Wycombe, is the secretary of the Chiltern but they missed the point.Just as had my j firstbicycleatSandringham, my Army Road Club, newly formed and affiliated to bicycle opened up for me an unexpected new theBritishLeagueof RacingCyclists. world. Interested cyclists are asked to get into touch " Even now, after three decades, I still meet with him at that address. men who will suddenly say :' The last time I saw you, you were on your bicycle on the Welsh Cycling Union road to Poperinghe,' or Montauban, or any J.P. THOMAS, secretary of the one of a hundred French villages. MR.Rhos -on -Lea C.C., 15, Tan -Lan Road, " I am amazed when I hear the young Old Colwyn, N. Wales, would like to see a veterans of this last war talk so casually about Welsh Cycling Union formed, which would global war, with its whirlwind sweeps and enable Welsh riders to compete in the large rushes across oceans and continents." programme of international events organised by the B.L.R.C.-S.C.U.-F.S.S.T. combina- Thiefproof Cycles tion.At present the Rhos -on -Lea C.C. is the only body in Wales recognised by these J.G. SIMPSON, of Durham, apropos Progressivebodies. He appealstoall MR.my paragraph on thiefproof devices interested Welshmen to write, to him with a writes : view to furthering this project. " Your remarks regarding thiefproof cycles prompts me to pen the following (but no claim is made that the problem is solved).The New Hudson Silver ArrOw suggestions, suitably modified, may assist in AN attractive sports model has now been reducing the number stolen. added to the New Hudsonrange. " (,)' Bulky' cycles are not easily ,` taken The 21in. or 23in. frame has double -taper away.'Locking the front wheel at full lock seat and chainstays brazed -up, with cutaway can make forbulkiness.'With the wheel lugs and forward drop -out fork -ends.The locked in the ahead position only a little front fork is D to round with chromium - wrist -work isnecessary to get through a plated crown ;wheels are 26in. byI lin. crowd. A broadside wheelalsoattracts Endrick, with lightweight hubs. The handle-Reg. Harris, of the Manchester Wheelers, whoattention !Thieves don't Eke that. bar is Continental pattern, chromium platedhas just' been awarded the Bidlake Memorial " The aboiie presents a parking problem, on adjustable stem, and brakes are side -pull Plaque for 1947. so as an alternative, how about a form of caliper.Celluloid mudguards are fitted and street stand, lockable in the ' stand ' position, the brake cables are silvered.The finish is and for the sake of safety in the ' up ' position. attractive in carmine red with silver bandW. S.Gilbert-Cyclist (It might fall during riding.) on seat tube, and silver head.Price withTT is not generally known that W. S. Gilbert, " It would serve the same purpose because fixed and free wheel (model Gi8), £13 14s. 5d.1 who wrote the famous series of comicof its protruding at the side. (including £2 us. 11d. tax).Model GISDoperas, came from acycling family, and, " (2) More trouble, this ! This ' being an is fitted with B:S.A. 3 -speed hub, and costshimself was a keen cyclist.So also was hisunattended indicator (again lockable and for £15 us. 6d. (including £2 18s. 9d. tax), andwife. They even kept spare cycles in theincreased safety of cycle inter -connected with model G t8T,withCyclo gear,costshouse for the use of their friends, and all ofthe steering -head or other lock).Maybe a £15 17s. 7d. (including £3 os. id. tax).Athe servants rode bicycles. He had a specialhandlebar fixture, erectable and capable of ladies' model, 21in. or 22in., is available withstable for bicycles built in the grounds of hisbeing illuminated at night-something tubular, free wheel (model L16), or B.S.A. 3 -speedcountry house, Grim's Dyke, in the Harrowperhaps.Red being best avoided.It might hub (model L16D), at the same prices as theWeald. The Birmingham Post drew attentionbe mistaken for a rear light. men's models. to this in a recent issue. " (3) One to be frowned upon, but here it is.More rules and regs. ! Presentationto Arthur Whinnett Southern Counties Cycling Union " On sale of a cycle the frame number, an The high spot of the annual dinner of the THE list of road events has been alteredadditional number given by the manufacturer SouthernRoad Records Association slightly to the following and the name and address of the buyer would which was heldatthe WindsorCastle, Coursebe recorded by the agent (suitably approved. Victoria, on February 19th, was a presentationApril 4th -25 miles, 1st class .. G 2by the manufacturer) and also lodged with - to Arthur Whinnett for his valued servicesApril 11th -25 miles, Women .. G 2the police, latter also approving agents. to the Association for 20 years.The chiefApril 18th -25 miles, 2nd class .. G 3 " Now in case of a stolen cycle the police guest of the evening was W. H. Townsend,May 2nd -5o miles .. .. G 7would have something to work upon.Three secretary of the R.R.A.The presentationJune 13th-too miles ... .. G 9thingsmusttally. Thatiscomplicated took the form of a small record Plaque of theJuly 18th-co miles.. - . G 7enough. 52 THE CYCLIST April,1948 " The ' gift' number and usual name, etc.,with a small hole central Or eccentric, but notv;ith the history and development of the would be carried by the cyclist when usinginflated. pneumatic tyre, of the early problems, the machine and not fixed to the cycle. Stuffed cushion tyres which had largerlitigation, the competition, and the struggle " Changed frame numbers wouldn't tallyholes than the cushion tyresstuffed withto change popular beliefs in the solid tyrea.. with the police records. some light substance such as felt or cork. It was 6o years ago when Johnny Dunlop " Used machines could be dealt with in Solid rubber tyres, including tyres as usedrode off in the moonlight on the first pneumatic the same way through suitably approvedfor carriages and having A small central holetyres.Dunlop died on the 23rd October, agents (or dealers, if you prefer that name). for wiring on. 1921, and thus did not live to see the Jubilee " (4) This final suggestion is perhaps the Spring tyres. or the Diamond Jubilee of his invention. simplestandmosteffective. Giveall His daughter, hoiraer, Mrs.Jean ' regular 'cyclethievesonesentence- From small beginnings the Dunlop RubberMcClintock, isstillalive, and acts as an imprisonment.Some of the profits couldn'tcompany has developedto an enormoushistorical link between those days and the be set aside for that ! " world-wide organisation, and it has achievedpresent.She is,indeed, an authority on a remarkable transformationin tyre pro-Dunlop and his work, and we have been duction and methodsof manufacture.privileged to publish many articles in this G.H.S. and Brick Walls Famous namesflashacrosstheDunlopjournal from her pen. GH. S. is still at it.In a contemporary hestage-Zimmerman, G. P. Mills, J. W. Stocks, Our regretisthat paper shortage has saysthatthereisnopurposeinDick Palmer, Harry Green, F. C. Armstrong,prevented us from' signalising in the manner continually butting our heads against a brickA. J. Wilson, Arthur Du Cros. . .. we should have liked the Diamond Jubilee wall.It is almost unnecessary to tell yOu Dunlop himself wrote the " History of theof one of the world's greatest inventions, and that he is riding his hobby -horse and decrlingPneumatic Tyre," and it was published afteron lines comparable to that with which we massed -start racing.No oneis knOckinghisdeath.Sir Arthur Du Cros has alsospread ourselves in our issue dated July zoth, their heads against brick walls except G. H. S.writtena fascinatingbookentitledthe1938,which remainsasouvenirof the His attitude is, as I have pointed out before," Wheels of Fortune," which deals very'fullypneumatic tyre and a history of it. that he does not like massed -start racing, and therefore how dare you like it !In spiteof what he writes the Government attitude towards massed -start racing, or at PARAGRAMS leastitsspoken opposition toit(subtle (Continued from page 5o). distinction), has been entirely inspired by theUnder New Management Making Good Progress N.C.U. and the R.T.T.C., and by other GALLACHER, 36 -years -old racing ATthe dinner and prize -giving of the East Midlands critics. cyclist with a fine record in Scotland and the Clarion Club, held at the Victory Hotel, Leicester, The statement by Scotland Yard as long ago FdlARLESands over the past 18 years, has taken over the poston February 5, it was stated that the past season was of team manager to the racing riders of Kettering the most successful in the Club's history.Four Club as June 22nd, 1922, to which he refers, has no Friendly Cycling Club. In 1939 he left the Lanarkshiremembers, R. Meadwell, R.Cassy, W. Pratt and relation whatever to massed -start racing.ItRoad Club and went south to Northamptonshire, butR. Herbert are in the short list for the Olympic Games. referred to time trials and motoring events. during the war he had little time for the sport, being'The Club is anxious to have a cement track at Leicester, too busy with other things. He will work on a voluntary and one speaker commented that many riders do not basis and is planning a course of intensive training forknow what it is like to race on a track until they are track work and time trials witti'a view to club membersactually on the point of taking part in an important New Tyre for Cars competing in open events.His greatest achievementevent. The Club now has a new award, the Whitworth TO improve radio reception on motor -carsduring his career was, he says, when he was 17 yearsMemorial Rose Bowl, which was won by Mr. and Mrs. old and came second in the National Scottish Cycling Sid Mottram.Sid Mottram had been Club secretary Fort Dunlop is at present experimentingChampionship,completing the 25 -mile course ina for 14 years until his recent resignation. with a new tyre, developed from one used snowstorm in z hr. q mins. by the R.A.F. during the war, which removes Pushed Bike ! Tudor Cycle Shop the static electricity generated by the move-WILLIAM LUSH, of Cicero, in Illinois, has built ment between tyre tread and road surface. himself a box of tricks on wheels which heMR. H. BERWICK, cycle dealer, of Sheaf Street, attaches to the rear of his cycle to push himself along. Daventry, has discovered during repair work at On a light framework on two small balloon-tyred wheelsthe premises in. Sheaf Street, which he recently acquired Tyres Have Four Lives he has mounted a 1 i h.p. petrol engine which drives thefor an extension of his business, certain building work wheels through a system of Vee-pulleys and belts,dating from. Tudor times.A beautiful carved oak CARBON black increases by 40o per cent. covered with an aluminium top for neatness.Thisstaircase has been found hidden beneath many coats of the resistance of tyre treads to wear,engine -trailer is clamped to the frame of the cycle onpaint, a number of oak beams came to light when either side of the rear wheel and can propel the cycle matchboarding was stripped from the ceilingsand Dr. D. Parkinson, of Fort Dunlop's researchat a speed of 25 m.p.h.Clutch and throttle cables arefour Tudor fireplaces were found to have been bricked department,toldBirminghamUniversitytaken to controls on the cycle handlebars.Mr. Lushup. The premises are some of the oldest in the town, Chemical Engineering Society in a lecture onhas also used the unit for towing a lawn mower when although during the Victorian period an addition was " Carbon Black in the Rubber Industry "he has not felt too energetic. made at the rear. recently This, he said, was primarily aBig Business consequience of the exceedingly small size of WHEN three boys appeared at Peterborough JnvenileNo More Punctures ! thecarbonparticleswhichtheelectron Court charged with cycle stealing, it was dis-nNE of the exhibits at a recent Trade Fair in Paris closed that they had gone into business in a big way. `-was a substitute for bicycle tyres, consisting of a microscope had shown to be of the order ofThe ringleader, who was 16 years old, had arrangedseries of coiled steel springs attached to the rim. The one millionth of an inch in diameter.Nextwith his two 15 -years -old " partners " to steal cycles springs formed a " tyre " about the size of the normal to rubber itself, carbon black was the mostwhich were left unattended, alter the cycles by changingcycle tyre and it is claimed that they give easy riding round the accessories and repainting them, and enterand are long wearing. The shortage of cycle and other largely used material in the world's rubberthem in local auctions under an assumed name. Whentyres has existed for a considerable time, it being quite industry, more than half a million tons beingthey were caught the boys had already stolen six cyclesusual to see a cycle offered for sale in a. shop minus consumed annually. valued at £48 xos. and were evidently working upthe tyres,and probably the new idea will become what was, to them, a profitable business. popular until tyres are more easily obtainable. All-time Cycle Record THE number and value of British bicycles exported during 1947 set up an all-time record-I,449,662, bringing £10,040,338 to Britain, asagainst the previous record of 1,073,391 machines, bringing in £6,442,826 the year before, Diamond Jubilee of the Pneumatic Tyre (Continued from page 49) tread.From the tin. and zlin. solids of 1871 to 1873, tyres gradually decreased in size as wheels increased in diameter, until a lin.tyre was considered the correct thing for racing, despite the fact that it ploughed into the grass on turf tracks and dug into cinder paths. In 1888 the tyres in use may be summarised as follows : The inflated or single tube in which there was one case to contain the air.This class included the tubeless tyres such as the Fleuss. Cushion tyres either round or oval inform April, 1948 THE CYCLIST 53 APEX The World Famous 'SUPERLITE'BAILEY'S CELLULOID PUMP `SUPER' 15 x BLACK PUMP IS x sBLACK Thick Celluloid "No other tyre Beautifully Polished Steel Lined Celluloid Covered

Light of Weight Lining is Solid drawn but of cartridgefashion, the ends being solid with the barrel will really satisfy robust construction 'SUPERLITE' ISin. Cannot warp nor leak. CELLULOID (with C /. BAILEY'S 'SUPER ' (Steel solid drawn brass.1/ lined and Celluloid (.11.1 plunger tube) each covered) ISin. each5/6 WaY me now" WW 'LASTWEL' CELLULOID BRASS PUMP,Nickel (withsteel split Plated or Black enamelled tutnt plunger tube) ISin.4/6 (with steel split Ai. each plunger tube) each -t APEX PRODUCTS Are in use in every Country in the world. Theyareknown andappreciated for theirreliability,long service and efficiency in their job of inflating tyres. Labour and materials arestill very much restricted; consequently supplies of pumps are scarce !If you are lucky in owning an Apex Pump, treasure it. MADE BY APEX INFLATOR Co. Ltd. ALDRIDGE ROAD, PERRY BARR, BIRMINGHAM 22B

THE " FLUXITE QUINS " AT WORK " Don't worry ! We'll soon be all right I I'veborrowedthis tinof FLUXITE." Yelled EH, "You're a dud; Our burstis a flood, " And now we're afloat for the night.'' For all SOLDERING work-you need FLUXITE-the paste flux -with which even dirty metals 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 with safety on ELECTRICAL and other sensitive apparatus. WithFluxite joints can bewiped " successfullythat are impossible by tiny other method Rubber Used for over 90 years in Government works and by leading dipped insulated cord body with deep engineers and manufacturers.Of all Ironmongers-in tins, tread for long life and safe riding.Tubes are 10d., 1/6 and 3/-. circular -moulded - tailor made tofitwithout Ai TO CYCLISTS ! For stronger wheels that will remain round and true, here's a time - wrinkling-rubber-base valve prevents air leaks. tested tip.Tie the spokes where they cross with fine wire AND SOLDER.It's simple- withFLUXITE-butIMPORTANT.

THE "FLUX ITE- ALL MECHANICS WILL HAVEN, GUN puts"FLUX- where you want it by asimple pressure. FLUXITE Price 1/6 or filled 2/6. IT SIMPLIFIES ALL SOLDERING -firestoneBEST TODAY * STILL BETTER TOMORROW Write for Book onthe ART OF "SOFT" SOLDERING and for Leaflets on CASE -HARDENING STEEL and TEMPERING TOOLSwithFLUXITE. Also on WIPED JOINTS.' Price Id. Each. FLUXITELTD., Dept.P.M., Bermondsey Street,S.E.I 54 THE CYCLIST April, 1948

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H32GZ April, 1948 THE CYCLIST 55 few days of its home -coming, and since then it has covered just over 2,000 miles without a creak unless you count the rather comforting protest of the saddle when Wayside Thoughts I put my weight on the cantle plate to ride up stiff slopes. But I must mention both the cable wires of the brakes shed their stops at the lever ends, a bit of careless ByF. J. URRY work on the part of brake makers, the kind of thing that never should happen.It is a beautiful bicycle to ride, although its blackness calls forth the derision of my younger friends with theirlustre -finished machines. I tell them, and it is true, that in a year or so my mount will look respectable still when theirs is wearing the shabbiness of a couple of winters.Still, that is all a question of personal preference ;I like 'em black, with a decade of decent appearance to please me along the road. My normal gear is the usual 6oin., very com- fortable for pottering around up to tz miles an hour ; fi/ but I have a 74in. when I feel frisky and the wind is fresh and my way.Also, I can go as low as 4oin., to trundle which is a good deal easier than walking when a y;Iuef/ long slope needs climbing. Yes, it is a beautiful bicycle, "//40/ii7,0/9111fi,'" 0///// easy steering with its 68 deg. angles, easy riding and /%///////%1/O///////l comfortable to the postured fellow in the saddle.It is 4W 470 /67.,/ lth the firstI hope of several to come home when their ""',aiamosavi///'/' l'q.1104 makers can give me the small elegances I desire, for not counting this May -time purchase, all my bicycles are of pre-war vintage except one, and are showing signs of their years of service. At this moment I am rid- ing a 13 years -old model on which I must have travelled 30,000 miles, andI am delighted with its running qualities,and,indeed,itsgeneralup-to-dateness except in the matter of enamel.That machine has only needed a new chain -wheel ,and rear sprocket, and a pair of new pedals, beyond, of course, many tyres and brake blocks.The rims, pre-war Italian Fiume alloy, have stood up remarkably ; I would have expected them to wear through,on the brake paths, as other alloy rims in my possession have done, but they look good enough for thousands of miles yet.For the moment FiRthir\Cyfield I am keeping the new bicycle for special journeys because Essex. the tyres are sound, and this cannot be said for most of my mounts, nor will it be possible to repair that fault A 'picturesque. village of until I can buy good open -sided tyres, not in ones or twos, but in half dozen pairs. My tyres are such rags `.`-`-k Worth. Ettex.,with. its pond and patches that the like of them I have not seen since and agreen,qabled houses 1 was 18, with that delightful age's impecuniosity. and old ckurck.. .

The Quiet Way THE pleasant anticipationof aquiet night ride The Cut! zenith.Such moments-and they are many in a year- makes me forget the dull days of work, and always remind me of Wordsworth's sonnet : thestillworseones whenthe hum andrattle THE ways are quiet again and the wartime loneliness " The world is too much with us, late and soon : of the machinery has ceased during those times when of them is now greater, for the military traffic has Getting and spending we lay waste our powers ; almost disappeared.I am not glorying in this condition, the works are idle for lack of power.But the clack of Little we see in Nature that is ours ; - the typewriter dots dismal thoughts with capital I's but simply taking advantage ofit,and-let me be We have given our hearts away ;a sordid boon "and dominant full -points.Then I go out into the candid-enjoying the changed circumstances of spring darkened night and in half an hour leave the line of cycling.I am indeed sorry for many people who And how true that is in a people that seem to hurry on found a quiet pleasure in travel now robbed of thatand have no time to look.Actually, we are betterfrustrated lamps along the last suburban street and enjoyment, and because of their age and inactivity beings if we save an hour or two a week for the quietude move silently and more contentedly under the stars cannot take to the game you and I enjoy.To thethat makes our blessings a realisation, and rest awhilebetween the black hedge -rows.Only a few lorries active and the healthy, I say it is their own fault if theythe driving spur of ambition.And I know nothing someet or overtake me, a pool of white floodlight, a do not take to cycling, get and keep fit, improve theirefficient in the way of healthy contemplation than agrowing and dwindling roar, and again I am almost local knowledge, and wake up one morning to discovercouple of hours aboard a bicycle, when the familiar ways the sole occupant of the road.Who would have they are capable of eighty miles in a day and can enjoy are etherealised under a sky radiant with the richnessthought so great a change as this could happen to our the performance. A famous newspaper said the petrol of sunset.Yes, there is more quiet joy in cycling on ahard hammered roads in peacetime ?Yet here itis, ban hit the comparatively few and those who couldgood bicycle than can be given you in the racing game and the winter night prowler has time to look and listen, best afford it.Like every general statement, that isor the broader pleasures of club riding.; and literallyto muse and remember as he passes over familiar ways not entirely true, simply because the car had broughtthere are millions still to make this discovery. he has known since his years entered into double amenities to many people who are too old to find figures. They are grand hours, these quiet rides home delight in the exercise which cycling entails.These over the long route, and I am lucky to be so situated changed circumstances on the road will mean a very Variable Joys that I can enjoy them and count the blessings cycling THAT, however,is onlyone phase of. a greatlyhas given me.UsuallyIprefer company on my great increase in the use, and I hope the enjoyment, of Ihave enjoyed and still enjoyexcursions,the chatter and change of words,the cycling, and if only the story of the pastime could be varied pastime. coinage of mind, but on these occasions it is very told in temperate language by the folk who have longthe others, albeit the sternly strenuous exercises bypleasant to feel self-sufficient, to see the orange glow enjoyed it, and the trade could supply us with the bestproxy. 'Right at the end of last season I was out allof a bedroom window where children are preparing class of goods, I am certain the pastime would enter aday helping my younger friends in a is hours' ride, for rest and to hear a couple of old owls hold a one note novel condition of enthusiasm which has been too longand it was a joy to meet so many of the old boys on theconversation with each other across the meadows. restricted to the type known as club cyclists.Alas ! roads, inflamed with the spirit of the ancient days. But, alas ! most of them were using up their last fewThey are a refreshment, and I wish many more people , the story is not told and the industry, by and large, is could taste of their goodness, for the essence from which not in a position, apparently, to give us the goods we gallons of petrol, and for the main part the bicycle was want and encourage those amongst us who love thea memory-albeit a happy one-to them.I wonder ifthey derii,e is the quiet activity of cycling. game to tender advice on the way to play it and thethey will return to the old love and get reasonably fit kind of instrument with which to enjoy it.Itis, ofnow that the spirit that moves the horses is deniedDunlop's Annual Donation course, one of the austerity impositions that make forto them ?From their point of view in the physical inhibition and keep us chained inside the circle of gene it might be a good thing ; for it is true that the DUNLOP are making an annual contribution of frustration.And there is another important hangover man who once rode a bicycle superbly knows how to zoo guineas to the Travel Association. in thought that makes the erstwhile motorist buy train on " and conserve his powers in order to enjoy cheaply when he takes to what, in his opinion, is thethem. The pity is he ever allowed them to lapse, that nextbestthing.His mindrecollectsbicyclesat great error in neglect which has robbed thousands of £3 19s. 9d., and he thinks Ca I should still purchase themen of apleasuresophysically splendidthatI TWO VEST-POCKET BOOKS! best or the near best.He has forgotten the rise infrequentlywonder how suchunwisdombecame costs and the P.T., yet curiously enough he remembersassociated with the old racing than, the worst example both when the prices of new cars are discussed. I havein neglect of cycling continuance in any type of rider. met this tangle of values over and over again when And this question of help on big racing fixtures raises WIRE AND WIRE mention has been made of a first-class mount-whenthe many difficulties of organisation to be faced by obtainable-costing a figure in the region of C30. club officials now that petrol has dried up.In these GAUGES modern days racing men have been more dependent on car aid than they recognise, and the withdrawal of ' By F. J. CAMM The Values Remain that useful carrier of helpers, and particularly of food .THE old prices have gone for ever, but not the old and drink, will create a problem. In the old days when 3/6, or by post 3/9 values.The best you can affordisstillsafe cars were not on the road, we used a pub or a cottage ; advice on bicycle purchase, where the value in the food and drink was plentiful and cheap ; but to -day the article is reflected in the ease of its running and its difficulties of provender are enormously multiplied, and comfort accommodation.That factis always worththe people of the pub or the cottage do not want you. NEWNES' RADIO ENGINEER'S remembering ;yet how comparatively many folk fall forIt is a fact to be faced if the basic ration is missing the seemingly similar article at a lower price.Thisfrom our scheme of life for the couple of years which POCKET BOOK oft -debated question isnot one of salesmanship sosome of my knowledgeable friends predict.Well, I much as of sense, for on analysis who would create for shall go on along the lonelier roads, and I and my like himself an unnecessary task for the purpose of savingwill rejoice that we are stillcyclists, happy in our By F. J. CAMM a few pounds ?Yet this errorisoften committed freedom, and thankful,I hope,for our health and deliberately, and it is nearly certain to bring .disappoint-activity, and tolerant to the disappointed people who 3/6, or by post 3/9 ment.Unfortunately, we do it in so many ways of life, envy, us. seeking for the things that never existed when the Obtainab!e from booksellers, or by worthwhile is so near to us that we fail to recognise it. I often think along these lines when on my eveningLuckof Ownership post from George Newnes, Ltd., jaunts, and am passed by people hurrying fiercely on their IHAD a new bicycle in May, luckily shod with (Book Dept.), Tower House, way, oblivious to the beauty of the closing day and the Sprites, stainless rims, spokes, bar, and seat pillar, _Southampton Street, Strand, W.C.2. loveliness of a land preparing for sleep, bathed in the a large sofa -like saddle of hide, and a four -speed " gear " splendour of light with one bright star high in the of the wide ratio type.I was touring with it within a 56 THE CYCLIST April, 1948 in the "drear " month of December-a reward piled on top of all the other ad.vantages which accrue from active participation in the road -game of road -games, My Point of View whatever the time of the year or the day (or night), and whether for short journeys or long.Further, when By " WAYFARER " Easter approaches, we who practise cycling as well as preach it will find an additional reward-for we shall be ready for the longer jaunts which the first holiday of the year presents to us. The Contrary Way USUALLY at this time of the year I provide myself with two front lamps-a gas lamp for the .senous evening journey and an electric battery lamp for the brief period before tea when darkness is falling.This latter avoids my having to " wet the carbid'e," which it is not worth while to do for an odd half-hour in the dusk. But how contrary these battery lamps can be !It so happened that, on the last Saturday in 1947, my gas lamp refuseil to operate properly, whereupon, a Mile or two from home, I turned off the water, blew out the feeble light, and switched on the electric lamp.At least,I went through the motions of switching it on, but the battery had run downand there was no response. So I had to revert to the gas lamp and put up with the miserable Om it was providing.Next morning I set forth for my usual day s. journey and a passer-by called my attention to the fact that my battery lampwas functioning.The contrary way !I switched off, and at the first opportunity I bought a new battery, being tired of this humbug. That night the gas lamp let me down again (trouble now diagnosed) and I had to revert to the battery lamp. A -broken reed !Owing to a faulty contact there were .no results and it was necessary for me to relight the carbide.The resultant light was so dim that at one point a policeman was constrained to cry aloud (twice), " Hey ! indicating, I fancy, that he desired to con- verse with me.I suddenly became, deaf in both ears, and there was a marked increase in my speed. Later on On the edge of the Plain-Erlestoke, looking towards Lavington. I was able to borrow an electric lamp and thus returned to the status of a law-abiding citizen.With the aid when this change occurred. With white blankets hangingof a meat skewer my erring battery lamp was brought Not To Be Answered in front of our noses, flop went our pace, and we movedto heel, and itis hoped that there will be no more THE writer of an open-air article in oneof the daily cautiously forward and downward in a world of silence.trouble.But these batteries are indeed contrary things , newspapers recently inqhired whether there was It must be admitted that I harbour no kindly feelings . . ..my rear lamp batters/ excepted.That, at the a nobler prospect of sea and mountain, south of Skye,'towards fog, which always makes it difficult for one tomoment, is behaving marvellously. than the view one gets from a boat midway between ride fast enough to keep warm, and which (in my case) Port Meirion and Borth-y-gest, North Wales. There istends to produce a headache. But the qettle had to . no answer to such a question ;nor, I imagine, was any Unrivalled Pictures It is beyond the wit of poor feeble'be grasped ,where fog is concerned there is no " escapeTHERE are those who think that I hold aprejudice answer expected. clause.'On the main road a mile below the ridge, against that type of entertainment which people, man to say which is the best view anywhere, so much ghostly traffic, in small quantities, was moving gingerlywith sublime effrontery, speak of as " the pictures." depending on circumstances over which there is noonward. We joined in the procession, finding, to our control-and also on the mood of the onlooker. Not for worlds would I desire to deprive the public of I have never seen the view which is the subject ofjoy, a gradual thinning of thefog. So our pacetheir right to think just what they fancy with regard to quickened, and our day's journey was completed inmyself and my views, but let it bri said, in a thoroughly this unanswerable inquiry, though I have gazed at thesomething like normal time. forthright manner, that my prejudice (if any) is directed scene in amazement, from many land points, and I A far better day-again in " drear " December-at those who make a fetish of going with habitual therefore turn to " The Cruise of the' Nona,'" byoccurred a fortnight later, .yielding me 76 miles. Theregularity and frequency to " the pictures " (with -their Hilaire Belloc, for something in the nature of con-joys of the afternoon transcended those of the morningoccasional concomitant of a chewing -gum atmosphere firmation of what is implicit in the question.This. is and evening, and our little party of three paused timeand a torrent of gangster English), while completely what Belloc says :" Therefore did we lie thus inandagaintolookoveralovelycountrysideto neglecting the beauty and the majesty which reside Harlech Bay, gazing at the great ;hills of Wales. Therethose distant hills we know so well.What beauty , is no corner of Europe thatI' know, not even the " The soul of winter ! " ejaculatedall around them-the undying loveliness of our country- splendid amphitheatre standing in tiers of high Alpinewhat colouring ! side, with its variegated colour scheme, its moors and the schoolmaster, as we lingered at one point, gratefulwoods and rivers and valleys and lakes and high hills, walls around Udine, which so moves me with the aweto the farmer who, having cut down his hedge, had and with its ever fascinating network of roads and and majesty of great things as does this mass of norttiem provided us -with- an opportunity for such grand views. Welsh mountains seen from this, corner of their silent lanes wandering hither and thither.To my way of The scene was indeed an enchanting one, the layers of thinking, those are the pictures which are worth patronis- sea." grey clouds in the sky being beautified with streaks ofing, day by day and week by week, as opportunity salmon -pink, and the rolling land telling out part of its offers. Those " Drear " Days endless story.It was a picture of greatinspiration, Having thrown that off my chest,I et me now frankly IF it had been suggested to meduring my .earlysomething to take away with us, in the storehouse ofadmit that during i947I went to" the pictures ' cycling career that the time would come when athe mind, for use on future occasions when, owing to twice. The attraction of ." the pictures " was the ride of 7o -odd miles on a " drear " day in Decemberthe exigencies of work, these rural scenes were not quite scenery, and, the scenery alone.A friend who was would be commonplace, I am sure that surprise would so near at hand. holiday -makingintheIsleof Ske while" The have been registered.And yet that unspoken prophecy Thus we went on our way, preferring a roundaboutBrothers " was being created (" shot," I fancy, is the has come to pass IAt the time of which Ispeak itroute to the direct road.Night closed down upon us, term to use) wondered to me " what sort of a mess they was my habit-and the habit of many other cyclists-but not before we had been favoured with a secondwould make of it."I went and saw, but am not in the to have done with cycling at the end of September,joyous glimpse of the distant hills (in another direction) ; least degree competent to express an opinion on thb the pastime to be resumed in the following spring. and rather belatedly-an hour after lighting-up time-wetechnique of the film. Later on the possibility of looking This is hardly the occasion to dwell on the supremecame to the cottage of our choice, there to be welcomedat some Irish scenery sent me post-haste on a visit to folly of such a course (still practised by a small selectionby a grand fire and a first class tea. And so home-in0 Captain Boycott."Each of these films provided me of wheel -folk), with the cutting out of one of the bestthe cool of the evening IA week later-the last Sundaywith snippets-and nothing but snippets-of lovely months of the year from the open-air standpoint ;of the year-I partook of " the mixture as before ' (indeed, adorable) scenery, whetting my appetite for and, whatever may be said in support of the policy ofwith a total of 72 miles. Not bad for three Sundays inmore and more& the real thing. My complaint against refraining from active cycling when the conditions are" drear " December I the cinema is that what it presents to the public lacks really difficult, October is essentially a grand month for continuity and endurance, andI am bound to say " the living out of doors."A good October can beSupporting Evidence that my preference is for still pictures. very good indeed ; indeed, magnificent. That is by theTT may be fitting, at this juncture, to summarise a In this latter connection I recall a little controversy way.For many years now I have looked upon every letter which appeared in The Times immediatelywhich raged a few years ago as to the relative merits month as a cycling month, maintaining that our pastimefollowing compilation of the preceding paragraphs.of static and moving pictures as regards cycling lectures. is just as good in February as in May-just as thrillingActually, the letter was written (by a Glasgow lady) to I voted-perhaps rather vehemently (as is occasionally in November as in July.That is the voice of experience. complain of the alleged inaccuracy of the official weathermy wont)-forthe" out-of-date ' magiclantern. On anearlySundaylastDecember- drear " forecasts,anditgave afine picture of Saturday, My vote still goes in the same direction, and is all the December-I set forth for my usual jaunt, which, inDecemberloth(" drear "December again !)-" afirmer now because the opportunity for seeing " the the event, totted up to 73 miles.It was certainlyday (she said) of such exquisite loveliness that peoplepictures " has been multiplied many times over, and a forbidding morning, with a definite threat of fog. noticeably took a more optimistic view of the worldbecause it is a change and a relief-to put the thing But, after a while, I rode in splendid sunshine, whichin general and Britain infparticular."The dawn, sheon no higher plane-to be able to view still pictures, put paid to the opaque atmosphere and touched theheard, was remarkably beautiful.As to the dusk, ofwithout dithering or clamour.Moreover, after some glowing countryside into life.The low temperaturewhich she was an observer,:" Imagine the semi -circle25 years oft ecturing for cyclists and others, I find that suggested the desirability of steady movement in orderof the sky from east to west ;the cast already in grey - the product of the well -named magic lantern is still that personal warmth might be maintained.So, in,blue darkness with high in the heavens a silver half-received with complete acceptance by my audiences pleasant conditions, lunch and tea went by, and lampsmoon set in a hazy gold aureole.From this point whether of the wheeling or the walking variety. were lighted for the evening run home, this part of thewestwards a dome of turquoise was suffused in an Yet, when all is said and done, we must return to the day's programme being shared with two companions.after -sunset light ranging from coral to deep orange, basic fact that the best pictures of all-the unrivalled Nearly half of the final stage of the ride had beenin which light clouds, sotne rosy, one dark indigo, werepictures-are those which we travellers obtain during accomplished when, without a word of warning, wesuspended.And the air soft and calm."And the our journeyings ;and those pictures are all the more found ourselves enveloped in a thick fog-and not aconnection 'betweenthisgloriouspicture and ourappreciated w.ien they are earned by " the sweat of valley fog, either, for we had just topped a line of hills pastime ?Well, here is one of the rewards for cyclingthe brow." Published about the 30th of each month by GEORGE NEWNES. LIMITED. Tower House, Southampton Street. Strand. London, "Practical Mechanics" Advice Bureau COUPON W.C.2, and Printed in England by W. Speaight & Sons, Ltd., Exmoor Street, London, W.10.Sole Agents for Australia and New Zealand-Gordon & Gotch (A/sia), Ltd. Sole Agents for South Africa-Central News Agency, Ltd. Subscription Rates This coupon is available until April 30th, 1948, (including postage) : Inland. 105. 6d. per annum. Abroad, 108.1)er annum. Canada, 10s. per annum. Registered at the G.P.O. and must be attached to all letters containing for transmission by Canadian Magazine Post. CONDITIONS OF SALE AND SUPPLY :This periodical is sold subject to the following conditions, namely, that it shall queries,together with3penny stamps/ A not, without the written consent of the publishers first given, be lent, re -sold, hired out or otherwise disposed of by way of stamped, addressed envelope must also be enclosed. 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