DYNAMO AND MOTORPROBLEMS pRACTICAL9D 'MECHANICS EDITOR : F. J. CA MM DECEMBER 1947

102) THE NEW 30,000 -TON LINER"OFtCAD.ES" ON THE STOCKS (See page

PRINCIPAL CONTENTS World of Models The Reign of Radium Adjustable Focusing Stand Letters from Readers Electric Light and Power Installation Mobile X -Ray Unit Cyclist Section Eyes and Ears of the Air Making a Shocking Coil 4/- per doz,,n sub, plus Purchase Tax

N° 300

M ADE BY

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 orour Research Department can design a clip for that particular job of yours. Over 92 years of clip -making is at your disposal.

HERBERT TERRY & SONS LTD.,REDDITCH London, Birmingham, Manchester, December, 1947 NEWNES PRACTICAL MECHANICS 73

JOHNSONPLASTIC News of the models Although the productionof our famous PRINTING FRAME modelsis increasing,alargequota is FOR AMATEUR PHOTOGRAPHERS reserved for export, and supplies for the home market are therefore limited. THIS new frameismoulded inone piece in Our Gauge ' 0' Model Railway Catalogue (GI12), price II-, will give you hard plasticwithsquared -upsidesand prices of models available and delivery dates of forthcoming models. Send for it to -day. ends.The hinged back fitsaccurately and " PECO-WAY," the most realistic Gauge ' 00' Permanent Way. Send cannot slip or slide.Sturdy steel springs exert for Booklet, price 6d. " Model Railway Handbook," Standard Edition.Price 6s. 6d. anevenpressureover the whole surfaceof " How to Build a Working Model Road Tractor,in. scale " ...Price II- the negative and paper.The smooth, dead -level " How to Build a '.in. scale ' Flying Scotsman ' " ...Price 11- precision of this well -fitting plastic back will be a " Laying Permanent Way " " Model Supplies " (L:112) .. Price 6d. delightto those who,inthepast,have had trouble with wooden frames which have warped. BASSETT - LOWKE LTD, Sold by alldealersin one size only, with NORTHAMPTON glass,forfilms upto x 3} inches. London Showrooms :112, High Holborn, W.C.I. 'Phone : HOL 6285. Manchester :28, Corporation Street. Johnsons of Hendon Customers in ornear London are invited tovisit our London Showrooms, where our PHOTOGRAPHIC CHEMICALS AND APPARATUS technical staff is at your service.

S. TYZACK & SON, Ltd. TOOL & MACHINERY SPECIALISTS The.Characteristics Tell SETS OF STOCKS & DIES S. C. BROWN, Type I K' with Tap Wrench, Diestock, Taper and Plug Tap to each size.Corn- Moving Coil Headphones, with plete in Polished Cases. the following outstanding ,u-Ny SetNo. I-Whitworth 1, , Is,1, characteristics,s u pp I ythat 34/6 Set. HighFidelityReproduction Set No. 2-B.A. 2.4. 6.8.10., 37/9 Set. demanded forDX work, + I Set No. 3-B.A. 0. I. 2. 3. 4. 5. 6. 7. 8. 9. 10, 010311T1) 68/6 Set. monitoring and laboratory Set No. 4-Model Engineer Thread, 1, purposes, etc. ,Sr,5, 1, all 40T.P.I., 41'6 Set. Set No. 5-Whitworth,1, 166, I,is,I. 71/6 set. NOTE THESE CHARACTERISTICS. Set No. 6-B.S.F., 1, L71/6 Set. D.C. RESISTANCE, 47 Ohms. WE HAVE GOOD STOCKS OF TAPS AND DIES. IMPEDANCE, 52 Ohms at 1,000 c.o.s. Please Send Us Your Enquiries SENSITIVITY,1.2 x10-52 Watts at THE " ZYTO " I kc.=.0002 DynelcmS. DescriptiveLiteratureon MOTORISED request. SPINDLE PRICE£5.0.0PER PAIR. TYPE'K' Supplies now available. MOULDER Order from your Local Dealer. Specially suitable for Carpentet:s, Fordetailsof other S.G. Cabinet-makers, Pattern -makers, BrownHeadphones (prices from25/- to 60j-) ask for etc., French Head lin. diameter. illustrated Brochure"P.M." Riseandfall spindle.Full details and price, free on applica- HEADPHONES WHICH UPHOLD BRITISH PRESTIGE tion.Please state voltage. S. TYZACK& SON, Ltd. Phone : ACOrn 5021 `roLtd 341-345 OLD STREET, LONDON, E.C.1 VICTORIA ROAD, NORTH ACTON, LONDON,W.3 Telephone: CLE 4034-5-6. Telegrams: TYZGAR, FINSQUARE 74 NEWNES PRACTICAL MECHANICS December, 1947 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 Ambitious men everywhere have succeeded through I.C.S. Home -Study Courses.So also can you. Iii BUT The man with an I.C.S. Training in any one of the subjects fifirrnaie.*-- listedbelow knowsitthoroughly, completely,practically. IT'S THE MOVEMENT THAT COUNTS Andhe knows how to applyitinhiseveryday work. No gift could be better chosen to make the new home complete than a Smiths "Sectric" Clock, and what Accountancy Diesel Engines Motor Engineering makes it all the more acceptable is the Advertising Draughtsmanship Motor Mechanic knowledge that every Smiths Clock SMITASISPIC Aeronautical (State which branch) Motor Vehicle Elec. is as technically sound as itis artisti- callyperfect. Look for the name Engineering Drawing Office Practice Municipal Eng. SMITHS before you buy. Air and Vacuum Electrical Engineering Plastics THE CLOCKS THAT NEED NO WINDING Brakes Electric Power, Light- Plumbing Air -Conditioning ing, Transmission, Quantity Surveying Cbtainable from Jewellers, Stores, Electricians and Supply Authorities. Architecture Traction Radio Engineering Architectural Drawing Eng. Shop Practice Radio Service Eng. cien. SCMI 121 Auditing Fire Engineering Refrigeration Boiler Engineering Free -Lance Journalism Sales Management Book-keeping. Fuel Technology Salesmanship Building Construction Heating and Ventilation Sanitary and Domestic Building Specifications Hydraulic Engineering Engineering Business Training Hydro -Electric Sheet -Metal Work Business Management Illumination Eng. Short -Story Writing Carpentry Industrial Management Steam Engineering Chemical Engineiring Internal Comb. Eng. Structural Steelwork CHEMISTRY Chemistry, Inorganic Joinery Surveying

and Organic Lettering (State which branch) ! Civil Engineering Machine Designing Telegraph Engineering Clerk of Works Machine -Tool Work Textile Designing Colliery Examiner's Marine Engineers Welding; Gas and Elec. Colliery Overman's Mechanical Drawing Woodworking Commercial Art MechanicalEngineering Woollen and Worsted Concrete Engineering Mine Surveying Manufacturing Cotton Manufacturing Mining Engineering Works Engineering And most of the Technical, Professional, Commercial and Educational 1 1 11 Examinations. (I.C.S. students preparing for Examinations are coached till successful) Al11111111 If youneedtechnicaltraining,ouradvice on anymatterconcerning EQUIP YOUR HOME LABORATORY your work and yourcareerisyoursforthe asking-free and without obligation.Let us send you full information regarding the subject in which you SEND STAMP FOR COMPLETE PRICE LIST are specially interested.DON'T DELAY.Make ACTION your watchword. The successful man DOES to -day what the failure SPECIAL OFFER INTENDS doing to -morrow.Write to us TO -DAY SELECTION OF USEFUL APPARATUS Tripod Stand Bunsen Burner Use this Coupon Wire Gauze Rubber Tubing INTERNATIONAL CORRESPONDENCE SCHOOLS LTD Fireclay Crucible Beaker Pipeclay Triangle Flask Dept. 95, International Buildings, Kingsway, London, W.C.2 Test Tubes Holder Please send me particulars of your Courses in 12/6 (Carriage Paid) Name Age (USE BLOCK LETTERS) BOOKLETS Address " EXPERIMENTS IN CHEMISTRY " 7d. " CHEMICAL FORMULAE AND TABLES " 10d. Addresses for Overseas Readers " EASY HOME CHEMISTRY " 213 Aust .alia: 140, Elizabeth Street, Sydney. (Including Postage) Egypt :40, Sharia Malika Farida. Cairo. India : LakshmiBldgs.,Sir Pherozsha Mehta Rd.,Fort, spce, t fiAc 60,High Street, StokeNewington, Bombay. New Zealand : 182, Wakefield Street, Wellington. ICS B ECK LONDON, N.I6. South Africa :45, Shortmarket Street, Cape Town. 'December, 1947 NEWNES PRACTICAL MECHANICS 75

THE FLUXITE QUINS " AT WORK " Snakes -house ; the birds ; what a day ! You just My hair will be fast turning grey ; Ican mendthingsa!l right With the help of FLUXITE, make it and But this lot's the limit ! " bawled EH.. For all SOLDERING work-you need FLUXITE-the paste flux bake it- -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 " tb^ bearing.It is suitable for ALL METALS-excepting ALUMINIUM-and can be used with safety on ELECTRICAL and other sensitive apparatus. With Fluxite joints can bewiped " successfullythat are impossible by any other method Used for over 40 years in Government works and by leading engineers and manufacturers.Of all Ironmongers-in tins, 10d., 1/6 and 3/-. ilkTO CYCLISTS ! For stronger wheels that will remain round and true, here's a time - tested tip.Tie the spokes where they cross with fine wire AND SOLDER. !Cs simple- with FLUXITE-but IMPORTANT.

THE "FLUXITE" ALL MECHANICS WILLHAVE\ GUN puts-FLUX- ITE "where you want it by asimple pressure. Price 1/6 or filled FLUXITE 2/6. IT SIMPLIFIES ALL SOLDERING axiA dim Write for Book on the ART OF SOFT'. SOLDERING and forLeafletson CASE -HARDENING STEEL and TEMPERING TOOLS withFLUXITE. Also on' WIPED JOINTS."Price Id. Each. FLUXITE LTD., Dept. P.M., Bermondsey Street,S.E.I NE" Tools YOU Should have MODELLING MATERIAL MODELrailway buildings and platforms, The "AEROMATIC" model ships aridhouses, animals and Soldering & Brazing Torch many usefulandpermanent objects A general purpose low pressure gas torch with high can be made with Pyruma Plastic Cement. pressure performance. Only needs connecting to any You just "make it and bake it" to stone - ordinary gas tap.No maintenance, no adjustments, no hardness, and afterwards, according to our lighting back. instructions, paint innatural colours,i.e. SIMPLE - FOOLPROOF - EFFICIENT with enamels, poster -paints, etc.Pyruma Sent complete, asillustrated, is comparatively inexpensive, and is obtain- on receipt of 3716d. with order. able in tins from Ironmongers, Art Material DealersandHobbiesShops. Send Id. The " CRYSTAL" stamp for illustrated instruction sheet on Spray Gun Pyruma modelling to the address below. The ideal tool for allpainting jobs from a model to a car. Also for house painting, distempering, etc. Connected to any standard vacuum cleaner it will produce professional SAN KEYS results without mess, waste or effort. The " Crystal " Spray Gun will be forwarded PYRUMA by return, post free,on receipt of 751 - with order. N. B. Please state make and PLASTIC CEMENT type of cleaner when ordering.A special TRADE connector, desirable with all and essential ENQUIRIES Write : Dept. 4 with some cleaners, is available at 316 extra. INVITED

Dept. P.M. J.H. SANKEY& SON,L1T DOMESTIC SUPPLY COMPANY 341, REGENT'S PARK ROAD, LONDON, N.3 ILFORD EST. 1857 ESSEX (Near Finchley Central Station) Tel:FINchley 5190 76 NEWNES PRACTICAL MECHANICS December, 1947 Ley tools are

QUALITY Tools

PRECISION HAND DRILLS As illustrated.I -inch dia- meter capacity.

RATCHET SPANNERS 42Stocksizes. Indis- pensable for avembly and servicing work. SPECIAL: MOTORISTS' SETS of Ratchet Spanners complete in wallet.

UNIVERSALLY JOINTED SOCKET SPANNERS 18 Stock sizes.

POCKET SCREWDRIVERS 4 -bladed. " Leytools " are obtainable PRECISION fromallgood Toolshops, Ironmongers and Stores.If anydifficultyinobtaining '1HAND locally,sendyourorder Price direct, or write for descriptive SPECIAL leaflets giving full details of HANDY CARTON DRILL sizes and prices of any of 211- Prov. Patent No. 20987/44 the above tools.

Every" Leytool "is FURTHER "LEYTOOLS" ARE q genuinepost-war NOW BEING DEVELOPED design, asaccepted ENOUGH FOR by the Councilof LEYTONSTONE JIG & TOOL CO., LTD., 2C0 AVERAGE Industrial Design for JOINTS displayatthe LEYTOOL WORKS, HIGH ROAD, LEYTON, LONDON, E.10 "Britain Can Make Telephone: Leytonstone 5022-3 MLICTICORE SOLDERS LTD., MELLIER HOUSEALBEMARLE STREET,LONDON,W. I It " Exhibition.

The chances are,you'll get it quicker fromMIDLAND INSTRUMENT CO. EX -GOVT. AMPLIFIERS, nOntar two valves. triode and Q.P.P.A o HENRY J. NICHOLLS four transformers, key switch, on,g.ff switch, resistors and condensers. eAc. Contained in metal cases Tin. x x The Recognised Model Specialists 41in. Operates from 2-v. and 120-v. Idealfor loudspeaking intercomor Detailed Test Certificate issued with pickup amplifier. etc.Brand new in every engine, including accurateI wood transit cases, with instructions, GUARANTEED ENGINES R.P.M. Tachometer check. 30/- post free.Ditto, less valves, 151-, post 1/-. MILLS 1.3 O'I'LIERTESTEDDIESELS AIOVLNG COIL METERS. attractive 2/in. sq. flush, 0-300-v., ditto 0-20-,v., Britain's finest " little " KEMP 4 C.c. ... 8 0 diesel -the little brand new, boxed. 10/- each. Thermo- engine KEMP Ic.c. £5 0 0 static switches.2/8.Voltage regulators, with thebigheart.A £44 0 2/8,ditto with H.T. rectifier, etc., 3/8. popular all-round model MAJESCO 2.2 £512 6 GENERATORS, output 12-v. at MO for power and depend- ETA 'S' £816 8 or 750 watts. output 24-v. at 350 or ability. watts, brand new, 30/- each, carriZ Complete with TESTED PETROL ENGLNES 5/- extra. prop. SPARK COILS, 6 to 12-v. input, fit d FROG I7S £3 19 6 trembler and condensers, giving appr Higher and £5 5 6 MAJESCO 4.5 c.c. ...£6 100 tin. spark, superior job, brand n KEIL K.6 (with c. & c. & 1218,post 9d. MILLS SERVICE Wecarry MOTORS, 12/24-v.fitted centrifuge' prop.) £8 17 6 pump, for liquids. delivery at 24-V.. full stocks of Mills spares, and are STENTOR 6 c.c. (ditto) £8 IS 6 10 -galls. per min., brand new, 35/- post Higher authorised Mills repair specialists. free. ORDER NOW FOR XMAS EX -GOVT. BATTERY ELIMINA- stands the reputation of As foremost specialistsin Model Air- TORS, A.C. input200/250-v. output HOW TO ORDER Order personally D.C.120-v.at 30 m.A.. far superior to Harbutt's " Plasticine." For " craft, Diesel and Petrol Engines, we are or by mail, you get the same service either civilian types, fitted neon stabilizer, ready to advise and help with your particular way.All postal orders guaranteed. CASH etc., brand new, 40/- post free. more than fifty yearsithas problem. We carry large and varied stocks, or C.O.D.Orders £1 or over, post free. AIRCRAFTEQUIPMENT, oil pres- and our service to Modellers costs no extra. Under £1, send 11- for postage and packing. sure gauges complete with termination, been the only reliable material 0-1501.b.s., 3/6.Revolution counters (electrical) 0-2,500,718. Rate of clinlb for model makers of all ages. indicators,5/-. Air -speed indicator's, CAR KITS YACHTS,SHIPS GALLEONS 5/-. Altimeters, 15/-. Artificial horizow Whether for home amusement CAR KITS GALLEONS 10/-.Turn and bank indicators. 7, - designing - experiMenting Grand Prix Bugatti 1219 Watercraft La Bona Esperanza 44,- Direction indicators,12/6. Alta 1219 IRON -CLAD5AMP. A.C. ALAI S -or the handyman, " Plasti- Santa Maria 481- SWITCHES, for two -light, etc. contr Mercedes Benz ... 1219 Golden Hind 581- Modelcraft Mercedes Benz four position switch, No. 1 light cine "isindispensable. Be- 816 Half Moon 6716 only, No.2 lighton only, both Modelcraft Bentley 816 Bounty 1919 both off, size din. x Sin. x I lin., attrac- causeitisever -plasticand YACHTS, SHIPS Century Golden tive job, with circuit, 5/-, post U. hygienic, " Plasticine "has Adamcraft I8in. Dinghy ... 70/- Hind ... 551 - TELEPHONE SETS, consists of two Southern Swan 29in. Yacht 3716 Bateman Santa combined microphone and earpieces, hundreds of other uses, and it lona Yacht 25ft. connecting wire, giving perfect 3816 Maria ... 51 - communication, complete set, no never deteriorates. Drome Hydroplane 311- Golden Hind 516 batteries required. 12/8. post 6d. Frog Plastic Tugboat 9/11 Southe'rn Junior Hundreds of other Interesting Radio. Binnacle M.T.B. Miniature 319 Electronic, and Mechanical items, send Golden Hind 251 - for our current lists, 2d. with s.a.e. 319 Plank -built Orders over 30/- post free.No C.O.D. 'Plasticine' Cabin Cruiser Galleon ... 1116 under 20'-. ACCESSORIES --HART model ship fittings; FLY -WHEELS HARBUTT'S PLASTICINE LTD., to specification; Petrol and Diesel SPARES; Balsa Wood. Rider BATHAMPTON, SOMERSET. Wheels, Coils, Plugs, Condensers, Props, Blended Fuels, etc. Moorpool Circle, LONDON.: 68,Victoria Street, S.W.t. Birmingham, 17. lomammommommom HENRY J. NICHOLLS, LTD., 308, Holloway Rd., N.7. Ltpl,t1:1°70,1g; Tel.: HARborne 1308 or 2664. December, 1947 NEWNES PRACTICAL MECHANICS 77 iNS MAKE AND o 00000000000 MEND IN REPAIRS METAL

rtgameati,,,,,,,,,,,,,,,,,,,,,,,,,sA rr4 nr There's almost nc I ARTICLES limitto thesplendid HOUSEHOLD things you can make with /11.: Juneero. You can shear orbend Juneero metal stripsandrods, Ti punch holesand cut threads.Special Juneero materialisprovided for use with the Juneero tool, and Manufacturers of in almost no time at all, you willlearnhow to make 'ascinatingmodels, or any DRAWING and number of useful articles. If you are unable to SURVEYING contactyourlocaldealer drop alineto JUNEERO, INSTRUMENTS Ltd. (Dept. P.M.), STIRLING CORNER, BO R EH A M WOOD, HERTS, asking us to post you an interesting SLIDE RULES leafletgiving fulldetails of Juneero.(Please enclose a penny stamp.) DRAWING MATERIALS EACH KIT INCLUDES THE PATENT MULTI- PURPOSE TOOL. DRAWING OFFICE Pat. Nn. 441157/34 STATIONERY

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41 GAR.TIIDE IT. MANCS-IffTfR. 3. CONSTRUCTIONAL KITS Complete at 25/- and 42/- with spares

, WORKS WISDOMFROM Wullth MEMBERS blows I C ..,11 Book wind which ,` RSPE)- ea___Iverybody good

Tokens say.) ciltsoItiEtiE are /74-0 BREEZY BLOWER SY Well, you can hardly exchangeable call it a wind- tor- We are OFFICIAL STOCKISTS of nado more like it. In " PERSPEX "and" CRINO-

for any book fact, the breeze - THENE, carrying large stocks for comes out of the immediate delivery at CON- at almost any nozzle of this little TROLLED PRICES. ,0 machine at220 m.p.h. bookshop Just a puff of that in "PERSPEX in Clear and Coloured, the works and- inflatsheet fromI/16in.to(in. w-o-o-s-.h -dust, thickness. swarf and shavings 3/65/- 7/610/62i/ - disappear. Of course, SmallConsumers,Hobbyists and plus threepence service fee electric motors, prototype Plastic Engineers, come to switch gear and other us with your enquiries. machinery last years longer when they're cleaned out regularly with this Wolf Portable Electric Blower.It's a handy Send for Price List. little jab, too-weighs only 11 lb., so it's no trouble. What's more, it's only a tick or so's work to change the blow to a suck and there you have the last word PLASTICS WolFin industrial vacuum cleaners. It's easy (MCR.) LIMITED. ELECTRIC to see how a machine like this can help TOOLS in' he big production drive for economic II, WHITWORTHST., freedom. *World Union of Wolf Users. MANCHESTER. I. The range of Wolf Portable Electric Tools includes-Drills, Bench, Pedestal, Handand BOOKSARE Flexible Shaft Grinders, HammerandHammer Kits, Screwdrivers, Chisel Mortisers, Phones: Central 0272 Sanders, Blowers, Engine Reconditioning Equipment including Valve Seat Servicing Kit, ALWAYS IN SEASON Engine Kit, etc. and 1725 S. WOLF & CO. LTD., PIONEER WORKS, HANGER LANE, LONDON. W.5 8189 78 NEWNES PRACTICAL MECHANICS December, 1947 .

PREPARE FOR COMPETITION NOW ! As the Engineering Industry swings into its peace -time 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 you 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.1.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 Installations *Draughtsmanship & Tracing Welding Traction Telegraphy Works Management Sheet Metal Work 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 General Automobile Eng. Inst. Mun. Engineer Road Eng. City & Guilds Garage Management A.M.I.Struct.E. Hydraulics Automobile Repairman Electrical 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 AND BUILDING 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 & Level ling 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 f ICIa week you cannot affordto 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 PiSTITUTE OF ENGINEERING TECIROLOGY 410A, SHAKESPEARE HOUSE, 17, STRATFORD PLACE, LONDON, W.1 THE B.I.E.T. IS THE LEADING INSTITUTE OF ITS KIND IN THE WORLD December, 1947 NEWNES PRACTICAL MECHANICS 79

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. Registeredat transmissionby MECHANICS the G.P.O. for Canadian Magazine Post. Owing to the paper shortage "The Cyclist," "Practical Motorist," 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 orimitationsof any of thesearetherefore expressly forbidden. VOL. XV DECEMBER, 1947 No. 170

FAIR COMMENT BY THE EDITOR About Inventors THERE are certain pieces of mechanismlite together, using excessive pressure on thebe the screw thread and, as has been proved andcertainideaswhichfascinatenuttogeta more rapid and convincingabove, the greater will be the tendency for those with an inventive turnresult. nut slackness and the more vital the need of mind. As each new generation Within a week or so it will be found thatforpositivelocking. Coarsepitchscrew comes along it produces the usual crop ofthe nut is quite loose, although the pointerthreads can be manufactured, of course, to people with bright ideas for harnessing the willstillcoincide with the scratchmark,closer limits than small ones, rendering the water power of the country, converting coalshowing that it is the material which yields,design of a satisfactory lock -nut possible. into power at the pithead, of inventions fornot the nut. For such a lock -nut to be acceptable to perpetual motion, such as the motor which The inventor of the spring washer realisedengineers it must have a number of advan- drives the dynamo and the dynamo whichthisfact,for the spring washer tosome tages not hitherto possessed.It must, in drives the motor, and a goodly proportion ofextent takes up theslack caused by thethe first place, lock positively.It must not those who " want a list of things to invent."material yielding under compression. distort the screw threads.It must be pos- Now, one of the devices which has attracted Thereare many other ways of lockingsible to use the nut over and over again. inventors for many years is the lock -nut.Inuts, such as by means of grub screws-aItmust be possibleto removeiteasily. do not know why people Want to add to thereally humorous solution because you needIt must be reasonably cheap.It must not many thousands ofinventions relatingto a further device to lock the grub screw. Thereoccupy much more space than ordinary nuts. lock -nuts, few of which have been commer-is the mechanic's method of centre popping ciallysuccessfulandfewerstillachievethe end of the bolt, and many other methodsStarting a Small Business ? success in practice, but the fact is that lock -which tackle the effect instead of the cause. MANY readers leaving theServices ate huts are invented each year by the dozen. However, it would be idle to deny that anxious to start business on their own We cannot see that there is need for a newnuts subjected to heavy duty and vibration doaccount. They writeaskingforadvice one.For this reason and in order to pre-work loose beyond theslackening caused byas to the best methods of setting about it. vent readers from wasting further time on We cannot too strongly advise readersat this hoary old subject, concerning which Ithe yieldof the material-forit must be remembered that a boltisintension andthe present time not to waste their savings get quite a large number of queries, I wantitself will stretch as a result giving rise toby starting small businesses.Quite apart to deal this month fully with this problem. loosening of the nut. from thedifficultiesimposed by Govern- One ofthe major problems which has ment controlandthelicensingnecessary, confronted engineers since the invention of Itis absurd that with the progress madethere isa great shortage of raw materials. the screw thread has been to devise a satis-in screw -cutting we should still be using old-Firms old established are unable to obtain factory means of preventing the nut workingfashioned methods to lock nuts.The castel-sufficientofthesetofulfiltheirexport loose.Many devices have been invented tolated nut is not always successful.The nutcommitments.Itisnot generally realised this end, but few of them have been foundhas to be tightened and then the bolt drilledthat in most cases a licence to manufacture satisfactory and thatis why designersstillto take a split -pin.If this nut is removedparticulargoodsisonly granted by the specify the split -pin and the castellatednut. (itis a troublesome business withdrawing aBoard of Trade on the understanding that Lock -nuts hitherto have been unsatisfactorysplit -pin), orifthe material yields, or foratleast6opercent.oftheoutputis not because the principle of the lock -nut isany other reason the nut works loose, theexported. No smallfirmcouldpossibly wrong but because the screw threads were notsplit -pin hole when the nut is tightened orenter the export market at the present time. made to the close limits now commerciallyreplaced seldom coincides with theslotinIt would not pay them to do so. These possible. The time has arrived for the oldthe nut. small firms may have an expected turnover prejudices to be swept away in view of our As therearesix such slotsthe angularof about £2,000 a year, but the formalities improved methods of nut and bolt manu-movement of the nut to bring another onewith which a small firm has to comply are facture and our advanced knowledge of theinto line with the hole is 6o degrees, andjust as onerous and formidable asif their subject. this may be impossible of attainment, whichturnover wereamillionpoundsayear. Why do nuts work loose ?Many of themeans that the nut in practice is slackenedFinding export markets is an expensive job, earlier designs of lock -nuts have been basedback to bring the holes coincident.Thusand unless the turnover is at least L50,000 upon the false premise that it is the nut itselfthe whole object is defeated. a year it simply does not pay. which works loose.This is not always the Small nuts with comparatively fine pitch Capital is another problem. A small firm case. The materialboltedtogether mayscrew threads do not often work loose, andcannot possibly buy at favourable terms.It yield under the pressure exerted by the nut,in any case they are only used on smallcannot afford to pay cash, and even ifit which places theboltintension andtheorunimportantparts where nutslacken-could raw materialsuppliersareunlikely parts bolted together in compression. ingis not accompanied by serious results,to open out fresh accounts when they are The softer the material the more rapidlyand in any case can be rapidly tightened.unable to fulfil existing commitments. will it yield, so that frequent tightening ofThe finera screw thread the lessisthe An increasing demand for the diminish- the nut will be necessary. A simple experi-tendency forthe nutto work loose,foring supply of raw material naturally forces ment will demonstrate that itis not alwaysan angular movement of,say, 6o degreesprices up.We do not think that there is the nut which works loose.Solder a simplemeans that the nut has slackened back one -any room at the present time for new firms. pointer to the outside of a nut and make asixth of a pitch.One -sixth of a coarse pitchThe momentissimplynotpropitious ; scratch mark on some adjacent part to coin-screwthread,however,is areasonablytrading under present conditions is extremely cide with its sharp end point.Use this nutlarge angular movement. difficult, and the form -filling alone would bz on a bolt which clamps two pieces of bake- The heavier the duty the coarser musta burden to the inexperienced. 80 NEWNES PRACTICAL MECHANICS December, 1947 Dynamo and Motor Rotation Rotation

Problems 2 (b) (a) Fig. 7.-If a conductor or coil were stationary, "Cutting" Lines of Force : Distribution of E.M.F. in and the field started and stopped, maximum e.m.f. would be induced when in position (b). Armature : Field DistortionReversible Motors This is the position of zero e.m.f. if the coil is revolving in the stationary field. By H.REES,A.M.I.E.E. (Continued from page 377, September issue) to induce equal and opposite e.m.f.s in (a), NE or two questions call for furtherbetween (a) and (b) the rate of cutting andbut additive e.m.f.s' in (b). discussion from the first article. the resultant induced e.m.f. will be less than Is this last viewpoint correct?Itis one The firstconcerned an odd factthe maximum, falling to zero at (b). of those finer points of theory which some aboutthe" kicktest "forfinding brush Suppose, now, the conductor was not mov-readers may like to argue. neutral position.Why, when making anding: it is stationary, say, in position (b) when breaking the shunt field from a small -currentwe start and stopthe magnetic field-byDistribution of E.M.F.s in Armature battery source, do we get zero deflection in adoing as in the kick test.Will the induced The discussion should make clear why we millivoltmeter connected across the brushes,e.m.f. still be zero, or maximum, in positionget reversal of the order of things in the whilst the" neutralposition "isthe one(b) ?There isrelative motion-between akick test. which gives maximum output voltage whenfield coming into, and going out of existence, Fig. 8 will offer further elucidation.On the machine is running normally at full exci-and a stationary wire.Is the relative motionan armature there are a number of coils con- tation? such that the wire isstill, virtually, movingnected in series.The total voltage output is I suggested the anomaly was worth a littlealong or cutting (being cut by) lines of force?the sum of the e.m.f.s generated in one series thought. Often instudying the practical Itisa littledifficult to answer from thegroup, i.e., in one of the two or more parallel bearing oftheory,itisthe contradictionspointofviewofcuttingmagneticlines. circuits which make up the winding. -the exceptions to the rule-that are inter-Before giving any answer it may be an inter- Let us getthis point quite clear.In a esting. Indeed, thereare people who willesting experiment to carry out-if you have2 -pole dynamo, there are " two ways " round tell you that theory is invariably " wrong "a galvanometer sensitive enough to indicatethe armature from + to - brushes.The (disproved inpractice), but that statementvoltage inducedinasinglewire (witha,coils are connected up (in series) to form a strong enough field, somewinding which closes upon itself-all modern - A deflection would be got inarmatures are of the closed-circuit type. The a low -reading millia-result is that there must be at least two paths meter). (circuits), each containing the same number Otherwise,if we sub-of coils in series. stituteacoil or a loop, This is shown in Fig. 9a.An equivalent asindicatedin(a)andwould be a number of cells in series -parallel, (b),the answer becomesasin 9b.If thetotale.m.f.issoy.,as evident. indicated, this is the voltage of one group of cells-the e.m.f. of any number of similar In(b)all theflintrows of cells in parallel is that of one row. " threadsthrough "orSimilarly, in 9a ;the output voltage is that " links "with theloop,generated in one-half of the armature.But, (a) (b) i.e.,whenthefieldis of course, in the case of the armature coils Fig. 8 (a). -2 -pole dynamo, showing brushes in geometrical neutralstarted or stopped.Thea given coil is carrying only half the total position, i.e., no allowance is made for the shape of coils.(b).-Ifinduced e.m.f.will be aoutput current-" amperes " divide between the field is started and stopped (armature 'stationary), maximummaximum, though, if thethe two parallel paths. e.m.f. will occur in position A' B' ;the potential -difference acrossloop was rotatingina Reverting to Fig. 8a :the armature is sup- brushes will be zero. steadyfield,(b)wouldposed to be revolving in the direction of the represent the positionarrow. E.M.F.s willbeinducedinthe generally means there are too many indeter- ofzeroinducede.m.f.-inthiscase wetwo halves of the windings, which " meet " minate factors to a problem to permit of ashould say thatwhilethefluxthreadingin the neutral plane where the + brush is simple solution. the loopisstilla maximum, itsrateoffixed,and" diverge "fromthenegative Intryingtounderstanddynamosaridchange is zero. brush. Maximum e.m.f. will be generated in motors, at any rate, we cannot get on with- Conversely for position (a).It is the posi-the coils whose sides are opposite the pole out theory, and this query is a case in point.tion of maximum rate of change of flux andcentres, but the " maximum e.m.f." from the It provides a demonstration of the first lawsmaximum e.m.f. if the loop is revolved.But,whole armature-in the sense of being the of electromagnetic induction-the same sortif stationary, starting and stopping the field,total due to all the coils forming one series of fact which puzzled Faraday fdr a time,the flux linkage is zero-no lines thread thegroup-will be got where the + and-- in those classical experiments to find out the" turn "(or " turns,"ifacoil). Still,itbrushes are set,i.e.,in the neutral position mysteriousconnectionbetweenmagnetism.seems, lines of force must in some sense cutAB, where actually no e.m.f. is generated in and electricity. the sides of the loop, but in such a way asthe individual coils. Inthekicktestthe On " Cutting" Lines of Force I armatureisstationary ; In fact,Faraday himself invented asa the fieldisstarted and workinghypothesistheconcept ofwires stopped. From what was " cutting " imaginary " lines of force." said above, greatest e.m.f. The more you think aboutitthe more will be induced in coils strange it will seem why these ideas should locatedintheneutral be true.What does the conductor really /0 V. '0 tplaneAB-which were " cut " ?Is there any reason for supposing totallyinactive during that" linesofforce "have an objective normalrotation. Once existence, or has the space around a magnet againthetotalinduced some queer properties of its own?Intrigu- e.m.f. in the armature will ing problems of modern physics these, but be due toallthecoils we must take Faraday's laws as the last word forming one group. on the subject. (a) (b) But we have a com- A conductor revolving in a magnetic field plete reversal of the con- cuts across the lines in position (a), Fig. 7, Fig. 9.-An obsolete type of armature winding is shown in (a) toditions shown in 8a. The but is" moving along " the lines in (b)- illustratethe " closed-circuit" principle, and division of currentinducede.m.f.swillbe not " cutting " any, and therefore having no between two (or more) parallel paths-the e.m.f. (10 v.) will be thatofthe same polarityat e.m.f. induced.Position (a) is that of maxi- due to one parallel circuit.The equivalent battery circuit is givenAB, but will converge to mum e.m.f., and in intermediate positions in (b). give+ and-points December, 1947 NEWNES PRACTICAL MECHANICS 81: opposite the pole centres-at A', B', Fig. 8b. If the brushes were left fixed, two thingsthere is a regulating resistance in she field If the brush'rocker were shifted to this posi-would occur:first,severe sparking atall circuit. Here we have adecided weak tion we would get greatest deflection in ourthe brushes ;and, secondly, some slight fallspot because resistances can give 'risetoa millivoltmeter during a kick test-not zeroin output voltage,since the sum totalofdeal of trouble : bad contacts on the -studs, deflection. the e.m.f.'s generated in coil groups will nowbroken or burnt resistance elements, loose That, of course, is not what is reqUired.be got with the brush -position shown inscrews, etc. The object of the test is to locate the exactFig. to. So, before making any very detailed exam- neutral position under normal running con- In modern machines,interpoles preventination or testing, have a look at the field ditions, when the brushes are at AB.Whenfield distortion, together with any necessityrheostat.Very often itis not necessary to starting and stopping the field, we get equalfor readjusting brushgear at different loads.look any farther.All the resistance may and opposite e.m.f.s here (or A and B areBut the theory considered has an importanthave beenleft" in "thefield --the arm equipotentialpointsinthewindings,saybearing on such things as third -brush con-turned right over to the " Voltage Lower " +), hence zero " kickin our test instru-trol in car dynamos.One end of the shuntposition-with the result that excitation can- ment when the brushes aresettoexactis connected to a third brush (Fig. rob) andnot take place. neutral. this brush is located at a point on the com- Thus cause (3) in our list may take first Actually, we would get the same kind ofmutator where the voltage undergoes fairlyplace, though itis possible you will have to result in a dynamo normally running if werapid change, due to field distortion-if thego on to cause (a).The rheostat may be set held the leads of a voltmeter across points oncurrent, supplied tends to increase due to anO.K., but there may be an internal break or the commutator 90deg.(electrical)awayincrease in engine speed.Thus the flux canbad contact.That is quickly settled.Turn from the brush position.The reading willbe made to vary inversely as the speed, main- therheostatfull -on,oreliminateitcom- be zero, because there is no potential -differ-taining the generated e.m.f. and the chargingpletely by shortingthe two leads witha ence between such points in the windings.current sensibly constant. piece of wire. An Exercise in Ifthe dynamo now builds uptofull " Deduction " voltage,the troubleisclearly inthe field Thesecondproblemrheostat.If it does not, well, itis time to outstanding from thestart looking farther afield.Remember, we firstarticleconcerned aare concerned only with the shunt circuit. dynamo which failedtoThere must be a " break " somewhere in the generate, but showed a circuit, butit may beas wellto look at very small voltage whencommutator and brushes for possible " high a voltmeter was putresistance " contacts due togrit, etc.-not across the terminals. forgetting that protruding micas can cause Whatarethemosttrouble. likely causes?From the Finally, it may become necessary to make listof possible troublescontinuity tests:(a) first, of the entire shunt given, what would youcircuit from the switchboard rheostat, right (a) not waste time lookingback through the field winding to the oppo- Fig. to (a).-How the potential distribution in the armature changes for? siteterminal or brush;(b)thefieldlead with forward distortion of the field.(b).-" Third -brush Control" I gave " loss ofresi-between dynamo and switchboard ;(c)the on car dynamos makes use of this shift to control the field current dual magnetism " first incircuit through the field coils of the dynamo. as the speed varies. the list, because so manyIt may happen that the end of the shunt willfallforthisex-joined to + or - in the terminal box of the The matter should be perfectly clear by con-tremely rare type of fault. Obviously, itmachine has become disconected. sidering what a voltmeter would read if con-cannot be a likely cause in this case.Itis In allcontinuity tests,if(a)revealsa nected across points A' B' inthe batterygenerally the most improbable.The factbreak somewhere (b) and (c) will reveal in circuit of 9b-or, better still, compare withthat a small voltage is generated proves: (a)what part of the circuit it is located.Some- the " null " deflection obtained in a balancedthereis some magnetism in the poles;(b) times more complicated faults can arise due Wheatstone bridge. there are no broken connections to brushes to" earths " (or 'a combination of two or Inthe kicktesttheseequipotentialorand commutator; (c) that the brushes are atmore earths)inthe machine and external null points move round 90 deg. electrical. least touching the commutator, though there may be faulty contact. circuit. ShiftinNeutralPoints withField The voltmeter indication eliminates quite aThe " Critical Resistance " of the Shunt Distortion few Things.What else may be deduced? Well, if your voltmeter happens to be on a We must now go on to consider further I have discussed the theory of this simpleswitchboard(ordashboard), or you maketechnical principles. test in considerable detail because, as seen, itanother test at that end,itwill save alot One has already been referred to in refer- brings out quite a number of points import-of time searching for broken connections inence to failure to excite, namely, that there ant to understand in studying generators. the + and - main leads from the dynamo. isa certain critical resistance of the shunt Before going on to the next question left But do not forget the shunt field circuit.circuit,above whichself -excitation cannot over from the first article, it is opportune toAll indications point to loss of excitation, i.e.,occur.Itis important to realise that the mention another bit of theory of great prac-failure to build-up the weak residual magne-value of this resistance is " critical," i.e.,if tical importance.I made a passing referencetism. Thatiswhatisusually meant byexceeded, the field cannot possibly build-up. toitinthe previousarticle:how, once," failure to excite"-not the loss of residual In Fig. sib is shown a typical form of a attendants had to keep a steady eye on themagnetism itself.The shunt is not gettingmagnetisation curve.A dynamo is run at a load and give brushes a " forward lead " (inany current, or possibly not enough to startconstant speed, and the field amperes Iy are dynamos) as the load current increased. the building -up process. increased in steps, from zero, by varying the Armature reaction remains to be discussed noting.All theresistance F.R., observing at the same time the This last point is worth in detail.All I will say now isthis: connections may be reader should be able to understand what weO.K., yet there may be V mean by saying that any distortion of thesome high resistancein field, for example, in the direction of rota-serieswiththeshunt tion, willalter the normal potential -distri- whichwilltotallypre- bution in the armature: the normal distribu- vent self -excitation. I tion shown in Fig. 8a. will touchupon this If-forreasons whichneednotbe explained now-the armature -current causescriticalresistance again the field to be " twisted " forward, we shallpresently. get a new potential distribution,such as in Where are we to find Fig.to.The points AB and A' B' havesuch a high resistance ? moved forward, because coils previously inWell,Ihave knowna the neutral plane will now be cutting somefilm of oil or oxide or flux.In other words, the neutral position ofgrit, etc., on the commu- the brushes will have moved forward by an tatortostopmachines Field Amperes rs angle O. building -up - many a time. Remember,too, (a) (b) In Figs. 8 and to, and the discussion in the text, thatyou cangetsuch the brushes are shown in the " geometrical neutral," things as badly corrodedFig. It (a).-Connections for plotting Magnetisation Characteristic. i.e.,to avoid complicating mattersno accountis (b).-Straight linesillustratethe " CriticalResistance" ofthe taken of the coil -shapes in modern drum armature,,, terminals,orsometimes where the brushes would he se: opposite the pole -onesthathave workedshunt.Thus the dynamo cannot build up its field along a line such centres as explained in Fie. c. prc.vious article. loose. But,first ofall, as " OP," which is " off" the characteristic. 82 NEWNES PRACTICAL MECHANICS December, 1947

how the terminal volts V increase. The curve isexactly the same, but thereare reasons How would you " swap -over thefield shows the relation between V and I, at con-" for " and " against "-depending on otherconnections in this box ?Think carefully ! stant speed, and on open-circuit-no load on things. Let me mkt you one thing you may do, with- the machine. Weheadedthissection "Reversibleout thinking. At first V rises steeply with increase inMotors," implying thatareversing switch Strap "F " to " A," taking off the lead that magnetisation of the poles, but bends overor controller isto be put in circuit for fre-goes to the starter. Connect the latter to the and becomes flatas magnetic saturationis quent reversals. In that case, there is decidedshunt terminal that was previously strapped reached.If we consider any pair of valuesadvantage in putting the switch in the shuntto" L "-removingthisstrap. Next, of V and I drawing astraight line OPfield circuit (if a shunt machine), because theyou put in the main switth and proceed to through thispoint on the curve, then thecurrentisonly afraction of an ampere,start the motor.If runninglight, it races ; slope of this line is expressed by, Ordinate/whereasaheavy -current, more costly typeif loaded pretty heavily, you will probably Abscissa = V/I, = R, - the resistance ofof switch would' be necessary in the armatureblow the fuses.There areall the symp- the shunt fieldcircuit (including thefielu circuit. toms of-what ?-and why ?Draw a com- rheOkat) for these particular values Of V and Against this: it is very undesirable or evenplete schematic of the circuit to see what positively dangerous to break highly induc-you have done. Other lines such as OP' give the corre-tive field circuits, without suitable discharge Leave the strap and outgoing lead to the spondingresistancesatothervaluesof resistances. Eventhen,itmay notbestarter severely alone.Re -connect them to voltage and exciting current.The steeperentirely satisfactory for quick reversal fromthe same terminals, after you have changed - the line the larger the resistance-shown alsofull speed in one direction to the oppositeover the two ingoing shunt leads going from by the smaller exciting current Is. Thedirection. But if only occasional reversalsthe box into the motor. resistance of the shunt field winding itself isare necessary, made when the motor isat If you want to fit a reversing switch for constant. All we are doingisvarying .1 standstillwiththe power switched -off,a occasional use, you could disconnect these rheostat to give various values of Is. small switch in the shunt circuit should betwo ingoing leads, take them to the D.P.D.T. Observe that OP' nearly coincides withperfectly satisfactory. Switch, Fig. 12b, returning two more leads the steep straight portion of the magnetisa- It must be assumed, too, that we are con-from the switch to " L " and " F " in the tion characteristic.A slight further increase sidering at present motors notfitted withterminal box. in resistance would make it coincide exactly, Shunt Reversing 0 p and this is the critical resistance value above Winding Switch mentioned.Any further increase in resist- DRAT . About "Discharge Resistances"

ance would bring the line right off the curve, I would like to reiterate my warning here e such as OP". Since itis off the magne- about sticking switches indiscriminately in tisation curve along which excitation takes the shunt field circuits of machines. place, that simply means the machine can- If a highly inductive circuit is broken sud- not begin to excite along a line as steep as denly, the collapse of a powerful flux will OP". induce an e.m.f. in thecoils far in excess of the normal working voltage for which A Riddle they were designed.It is quite possible to I have just given you what amounts to a L self -induce a few thousand volts in the shunt purely mathematical explanation-or a coils of a machine whose ordinary working graphical representation of tritical resistance. pressure is perhaps 25ov. Apart from other dangers, the risk of in- Many technical explanations are ofthis at. Leads To Starter Leads To Starter type.Reference is made to characteristics, sulation break -down is considerable.There curves, tangents, etc., and,, in many cases, (a) (b) will be a long drawn out arc at the switch it is exceedingly difficult anything else.Fig. 12 (a).-Typical Terminal Box arrange-contacts, hence some tend to get the- idea Indeed, by logical principles itis difficult that a "quick -break " switch is essential. A ment in a shunt motor (or dynamo).Sr and S2quick -break to see what the account of critical resistanceare the ends of the shunt Winding brought into the, switchwillcertainlytend to illustrated in Fig.t tcan mean. According box .(b) A Reversing Switch in the Field Circuit.break the arc rapidly, but, in doing so, it is to Ohm's Law, a current should flow in aIngoing leads S, and S2 are taken off theirthe worst possible switch to use in an induc- circuit of any ordinary resistance value, how-terminals, to a pair of contacts on the switch.-tive circuit.The current is interrupted still ever small the voltage applied. Another pair of leads is taken off terminalsmore rapidly, with still larger induced pres- Thus if we suppose the machine to begin" L " and " F." R is a " discharge resistance,"sures. generating a small e.m.f. of e volts, underas a safeguard against breaking the field when So, go slowly about opening field circuits, residualmagnetism, how canR,beso and especially inserting switches therein for " critical " (no matter how large) as to make fully energised. any purpose other than making a change -over it untrue to write, a current I,---e/R,? inter poles, and, of course, no series windingswhen the main switch is off. Some current must start in the shunt.Ifin addition tothe shunt.Interpoles will Fortunately, there is one very easy safe- it does, it must strengthen the weak residualcome up for later discussion.If there areguard against excessive induced voltages.It magnetism, causing more volts to be gener-interpoles,itwill be well to note atthisis simply to connect permanently a suitable ated in the armature, hence alarger " juncture that most severe sparking ("flaring"value of discharge resistance directly across and so forth. However small, a current mustperhaps isa better word) will occur at allthe inductive winding, on the field side of cause some increase in magnetisation whenthe brushes if these auxiliary poles are lefta reversing switch as shown iiiFig.tzb. itpasses through fieldcoils consistingofof the wrong polarity relative to the main The effect is to cause the induced potential some hundreds of turns. poles. to give rise to a current in the closed circuit I think I will leave the question open for What was said above about a light -currentformed by the field system and the resistance, discussion.What we have to ask ourselvesswitchforoccasionalreversalsofshuntwhen the flux dies away slowly. The correct is,notso much whetheracurrent canmotorscannotapplytoseriesmachinesvalue of resistance can be calculated fiom a " start" in the field, as whether it can causewhere the field winding 'consists of a fewknowledge of the inductance of the shunt, such an increase in generated e.m.f. as willthick -wire turns carrying the same current asand thus depends on the size of motor, etc. ensure acontinuance of the process.Forthe armature.Here, it is largely immaterialFor instance,a value can be found which instance, unless the increase is more than awhether armature or field connections aregives a peak voltage rise (at the instant of certain amount, isit not possible that thereversed, and, in fact, most reversible motorsopening the switch) equal to the normal sup- extra volts will all be dropped in resistances?for driving cranes, vehicles, etc.,are seriesply voltage of the motor or generator. machines. (To be continued). Reversible Motors But letusget down, to actualcircuits, I want to turn now, to consider one orstarting with the simplest. two questions connected with motor circuits. First,abcutreversingthedirectionofPitfalls WORKSHOP CALCULATIONS rotation of d.c. motors.The general rule It might be thought hardly possible to go is simple: reverse the two armature, or thewrong in doing such an easy job as reversing TABLES AND FORMULA two field, connections, but not both.Fora shunt motor.All I can say is :don't treat Eighth Edition example, the two main supply leads to aeven shunt motor circuitstoo lightly-as by F. J. CAMM motor are changed -over, armature and fieldsome who pride themselves upon being A handbook dealing with methods of currents become reversed and rotation will" advanced technicians " tend to do. calculation, solution to workshop problems, be unchanged. Consider the very simplest piece of wiring and the rules and formula necessary in While thisgeneral ruleiswell known,-as motor circuits go.Fig. 12a shows the various workshop processes.It contains there are frequent pitfalls, and one is occa-terminal box connections of a typical shunt all the information a mechanic requires. sionally asked: which is better, reversing themotor.One end of the shunt is strapped to From all booksellers, 6/- net, armature or the field ?Is it possible there" Line " (L) in the box ;the opposite end by post 6,'6 from the publisher, may be an objection in some cases to doing(F) is taken right back to the starter for GEORGE NEWNES, LTD. (Book Dept.), one or the other ?Theoretically, the resultreasons explained before. Tower House, Southampton Street, W.C.2. December, 1947 NEWNES PRACTICAL MECHANICS 83 The Elements of Mechanics and Mechanisms -2

Lawsof Motion-Friction-Mass and Momentum.By F.J.CAMM Absolute and Relative Motion (Continued from page 53, November issue) made of steel revolve in brass or gunmetal THE true motion of a body throughpaper, when the paper is slowly drawn along bearings. In watchesthepivots runin jewels. spaceindependently of anyotherthe weight will be drawn with it because When thehollowsarefilledup motion is known as absolute motion,gravity is pulling the weight downwards andbodies will slide over one another with greater and when the motion of one body is com-causing it to press on the paper. As neitherease, that is why oil is used between surfaces pared with the motion of another it is calledthe paper nor the weight is perfectly smoothsubject to friction. relative motion. We all know that the earthfriction is created. A considerable part of the power used in is not standing still, but that it possesses at A part of the force exerted by the handdriving machinery is lost because of friction, least two different motions.Firstly, it moveswill therefore be transmitted by the paper totherefore, we say that no machine is too per in a circle around the sun once in a year,the weight ;if, however, the paper is pulledcent. efficient.The most efficient machine is and secondly, it turns on its axis once in 24with a jerk the weight will be left beh:ndthat which gives out the highest percentage of the power put intoit. hours. Approximately, therefore, it can bebecause the friction was insufficient to pass Of course, fric- said that in consequence of motion aroundon to the weight sufficient force to cause ittion has its advantages.Without itit would the sun the earth moves rather more thanto move with the paper.As the weightnot be possible to build a house, for example. ti million miles a day, and in consequenceof could not move itself it is left behind. ThisThe slightest disturbance would causeit to it turning round on its axis a place on the isan example of inertia and many otherfall to pieces.We could not walk without equator also describes in one day acircle examples will occur to the reader. the friction between our feet and the earth. about 25,000 The inertia of water is taken advantage of'Itis more difficult to walk on ice than on havingacircumferenceof land, because there is miles. in the well-known arrangement for supplying less friction between All things and all people on the earth there-railway engines with water while the trainthetwo. We rely upon frictiontohold fore have these two motions, and when weis running. A scoop dips into the waterthings in our hands.When the short fibres say that an object on the earth is at rest weand is connected with a pipe leading to theof cotton or wool are woven into long threads mean that it is at rest as far as theearthis tender. As the engine travels along the itis the friction between them which holds concerned and not that it is absolutely at rest,mouth of the scoop dips into the water and them together. because that is impossible. before it has had time to acquire the velocity Now friction is of two kinds-sliding fric- Similarly, when bodies fall the motion weof the train it slides uo the pipe leading totion and rolling friction.Rolling friction is observe is not their whole motion but onlythe tender and rushes into the tank as ifit produced, for example, by a wheel rolling their motion relative to the earth. More-were impelled by a force pump. The waterover the ground, anditis very much less over, if, say, a suitcase is placed onthe seatis transferred to the tank, itwill be seen,than sliding friction, and that is why, when- of a railway carriage it is relatively at rest asby inertia. ever we can we trytosubstituterolling far as the other things or persons in the car- Now let us consider the second part of thefriction for sliding friction. riage are concerned ;it does not change itsfirst law of motion, namely, that when a body A labourer having to move a heavy load position in relation to them. But it is in isnot acted -on by any forceifitbe inwill put rollers under it.Chairs and tables motion in relation to the trees and hedgesmotion it will continue to move in a straightare often fitted with casters so that they may adjacent to the railway, and it has in addi-line with uniform velocity.This seenTs quitemore easily be moved about.Sometimes it is tion the motion of the earth. contrary to our everyday experience, becausean advantage to change rolling friction into We do not, of course, notice the motion all bodies as we know sooner ar later cease tosliding friction.For example, when a heavy of the earth, but we can establish it by com- move.This is because itit acted upon bywagon is moving down a hill a drag or sprag mon observation. some force.In the case ofaclock,foris placed under one wheel' so that the extra If two railway trains are side by side inexample, it stops because the mainspring, orsliding friction will retard its descent.This a station and one of them commences to moverather the force stored in it runs out.Thereis an elementary example of a brake suchas the passengers are often at a loss to knowis friction, and a moving body is bound tothe brake fitted to the rims of bicycle wheels which of the trains is moving. They seetouch something, causing friction.That isor into the brake drums of the motor -car relative motion, but until they look at somewhy, when designing machines, we trytowheels.They areall examples of sliding object known to be at rest, such as a tree, theyreduce friction to a minimum so that we canfriction. are uncertain as to whether their own trainget a higher percentage of the work put into Frictioncausesheat. Ifthespragto the machine out of it. which we have referred isfelt when it has or the other is moving. When we use a hammer we take advantagereached the bottom of a hill it will be found The Laws of Motion of the force of inertia.When the hammer isto be hot.During its descent it will become Sir Isaac Newton discovered the laws ofmade to move quickly through the air onso hot indeed that sparks may fly from it. motion, and he gave us most of our know-reaching the head of the nail it tends to con-Mass and Momentum ledge concerning Moving bodies. His firsttinue in its state of motion and in so doing Matter is that which affects the senses of law of motion states: " When a body is notdrives the nail into the wood. The pile drivertouch, sight, and smell.The force of gravity acted on by any force, if it be at rest it will isa further example of the use whichisattracts all things towards the centre of the remain at rest ;and ifit be in motionitmade of inertia. earth, and the force with which any sub- will continue to move in a straight line with The flywheelis perhaps the best knownstance presses downwards is called its weight. a uniform velocity." This law, unfortun-example.This isattached to engines andNow matter exerts force ;thus the earth ately, is not capable of absolute proof, sinceother machines in order to make them runexerts the force of gravity. A magnet exerts it is impossible to place a body on the earthsmoothly ;its inertia is so great as to compelthe force of magnetism, and a piece of amber so that it will not be acted on by any force.all the moving parts of the machine to main-rubbed with silk exerts the force of electricity. For example, gravity will always affect it. tain a nearly uniform speed. Matter doesnot onlyexertforcebut Consider the first part of the above law.Friction force always acts on matter. Indeed, it is not Place a ball on a table ;it is at rest relative Friction means the rubbing together of twopossible to recognise force until itis acting to the other things in the room. It willsurfaces.The smoother these surfaces are,onmatter. We shouldnotknow,for remain at rest forever if it is not acted uponthe less, under certain circumstances, will theexample,that a magnetwaspossessed by some forCe. The ball cannot move offriction be.Itis impossible to produce aof magnetism until we saw itattracting a its own volition ;if it does move some forceperfectly smooth surface, for every body haspiece of iron.The forceitselfis entirely has acted upon it. upon it projections and hollows which per-beyond observation, and we can only form This property of inactivityis known ashaps are invisible to the eyes.Even a piececertain conclusions about it by studying its the inertia of matter. The first law of motionof polished steel, such as a needle, if exam-action on matter. is often known as the Law of Inertia.Matterined under the miscroscope will be found to A portion of matter large enough to be offers no active resistance to any force act-have these projections and hollows.So thathandled is called a body.All bodies take up ing on it.Inertia merely means that therewhen two surfaces are rubbed together thea certain amount of space ;in other words is no power residing in matter by which aprojections of one will fit into the hollows ofthey have a certain size.The amount of body can either move itself or bring itselfthe other.Friction between pieces of thespace 'taken up is called its volume which is to rest if it be set in motion.. same material is greater than between piecesmeasured in cubic feet or inches. If a. small weight be placed on a sheet ofof different material, and that is why shafts (To be continued.) 84 NEWNES PRACTICAL MECHANICS December, 1947 Eyes and Ears of the. Air. Instruments Which Enable You to Fly Safely Through Clouds MAGINE you are sitting inthe com- fortable cabin of a B.O.A.C. aircraft, I bound, say, from England for the Far East.Idly you're looking out of the window at the fields and woods of Northern France spread out like a relief map below.Now the captain pulls back the controls and the aircraft climbs into cloud to gain height in order to avoidhills on the route.Mean- while, mist blots out your view and you are totally-butsafelyandcomfortably-en- closed in a world of opaque whiteness.It sat this time that the pilot and his crew rely on the aids which modern science pro- vides to make safe your flight through all this cloud some thousands of feet above the earth. The pilot flies by his instruments, oper- ated by gyroscopes which are no more than a scientific adaptation of the toys we played with as children.You may remember that once you set your toy wheel spinning, the gyroscope would maintainitspositionat ' whatever curious angle it was placed.In the aircraft, gyroscopes areset spinning ina vertical and horizontalplane,maintaining indicators in vertical and horizontal direc- tions which do not move asthe aircraft An air traffic control room, shown by the Ministry of Civil Aviation, in operation recently at turns about them. Radiolympia. Artificial Horizon voiceas you call-until you rejoin themchanging note of the engines will tell you The horizontal indicator gives the pilot ansafely.Theyhave " homed " you orthat you're climbing through the clouds, as " artificial horizon " to replace the one he" brought you in." you eat your lunch incomfort, and yOu cannot see through the cloud, and he knows emerge intoa world of brilliant sunshine whether he is flying straight and level, losing" Homing " an Aircraft carpeted with a seemingly endless flooring height or climbing by the related movements The same idea is employed in " homing "of cotton -wool. of a minute model aeroplane with the " arti-an aircraft,althoughitisa much more Later you fly between two layers of cloud ficial horizon " on the indicator. From otherscientificprocess. You may have noticedand, unable to take bearings on the sun or gyroscopic instruments in front of him thethat the strength of reception of some radiocheck the aircraft's position through the cloud pilot can also read degrees of turn and bank,sets with interior frame aerials can be in-below, the navigator asks the radio officer to and these also form the basis of " George,"creased by turning the set towards and theget him a" fix."Three widely separated the automatic pilot of which we heard muchaerialatright anglestothe broadcastingground stations take bearings on theair- during the war, and of the special compassstation.Itisa development ofthisideacraft's transmission, which are then plotted free of magnetic errors. which enables the ground " homer " stationby a ground controller on a map. Where As the pilot watches his instruments, theto determine the direction of an aircraft fromthese bearings cross or " intersect," broadly radio operator is in touch with the ground-the voice of the pilot or radio operator talk-speaking, is the position of the aircraft.To acting as the ears and, to some extent, theing on the R/T. understand this you have only to remember eyes of the pilot and navigator.Just as you This knowledge is reassuring to us in ourhow searchlights were used during the war. use the telephone in home or office, so thecloud world, and, although we are not yetThe sound detector, located near the search- radio operator and pilot can use their R/Tdue to land, similar ground stations help uslight sites, would pick up the sound of an (Radio Telephone) totalktothe controlon our way along the route, using morse-codeaircraft.Then searchlight beams for miles officers at airports and receive from them,when we are out of R/T (or voice) range.around would be lit and, with accurate read- for example, information about heightsatJust now,ifyouwereallowed ontheings from the detectors, they would intersect which to fly to avoid other aircraft, weather" flightdeck," you would see the wirelesseach other and form a cone of light around reports, directions for landing or take -off andoperator busily tapping his key.Over thethe aircraft.They had, in effect, got a " fix," taxying.In fact, instructions such as these" inter-comm," or aircraft house telephone,on it. were being passed by the control officer tothe navigator has asked for a QTE on Le The steward comes through with a message the pilot as your aircraft moved round theBourget airport, Paris.Now what, you mayfrom the captain.You canstillsee only airfield before taking -off while the stewardwonder, does QTE mean ?Well, with allcloud below but you read :" Over Lyons. .vas making you comfortable. the different countries, each with their ownBound for Marignane' Marseilles.' ETA language,operatingairlines,some inter- Remember, too, while you arein your (estimated time of arrival) 15.5o hours local national " basic esperanto of the air " had totime."Other unseen aids have been used world of whiteness,that, by means of anbe agreed upon, and thisis known as the R/T " homer " on an airfield, control officers to bring you to this position.By using his " Q " code.It consists of a whole series ofradio compass, the pilot may have " homed " on the ground can take bearings on the voicequestionsin combinations ofthreeletters of the pilot talking from theaircraft and on transmissions sent out from radio beacons each beginning with "Q," and -each meaningon the ground in a similar way to the " horn- from these the controller knows the directionthe same, say, to French or Dutch aircrewing " already described.Or he may have ofthe aircraft and can give thepilot,in asit does to the British radio officer of a return, directions to reach the airfield and " ridden the range," that is, picked up in his B.O.A.C. airliner. " QTE ? "therefore,earphones the morse signals " A " or " N " come down safely through cloud away frommeans" What is my truebearing from hills which cannot be seen from the air. from ground radio range beacons indicating you ? " ;and, having taken bearings fromthat he was left or right of his correct track At some time or other, you've no doubtthe aircraft's transmission, Le Bourget is ableand held his course if he heard the contin- been walking on moorlands when a suddento give the information and the navigatoruous high-pitched or " on course " note. white mist has blotted out everything aroundchecks thattheaircraftison the correct you.Your friends are within hailing distancecourse. Standard Beam Apkoach but you can't see them ;so you shout and The pilot calls for a weather report as he At some airfields, equipment on similar they judge the direction of your voice andheads southward over France.The wirelessprinciples may be used to direct the aircraft's shout back instructions-based on the in-operator taps out the message :" QAM ? "correct approach to the runway in conditions creasingor diminishing strengthof your(What isthe weather ?), and perhaps theof low cloud or poor visibility.The device December, 1947 NEWNES PRACTICAL MECHANICS .85 used may be the Standard Beam ApproachtalkingneitherGreek-norofcharming The pilot and navigator then know their (SBA for short)or its newer development,ladies!These are radar devices, developed exactposition and can " home " on the the Picao SCS.5s, or,to giveititsfullduringthewar, and beingfittedtoall Eureka beacon if they wish. title," The InstrumentLandingSystemB.O.A.C. aircraft as a further aid to approach When nearing the airfield, if there is much approved by theProvisional Internationaland landing in low cloud and bad visibility.low cloud about and visibility is poor, Babs Civil Aviation Organisation." Rebecca is the equipment in the aircraft andmay be called in to help.Babs, short name In SBA, a combination of morse signalsEureka and Babs the ground counterparts.for Beam Approach Beacon System, is sited in the pilot's earphones and visual indicatorsFor flying -boats the equipment is differenton theairfield opposite the approach end on his instrument panel,tell him whetherby name, but itis similar in design and useof the runway, and also sends out impulses he isleft or right of the correct line ofto Rebecca and Eureka. which appear on the Rebecca screen as dots approach. " Marker "beaconsatknown if the aircraft is to the left of its correct line distances fromthe runway alsotransmit of approach and dashes if it is to the right. high-pitched notes as well as flashing light" Blips " Ifitis" on course " a steady " blip "is signals. The pilot reads the height of the If you are interested you learn that Rebecca seen, and distance from the runway may be aircraft from a sensitive altimeter and startsin the aircraft has a green translucent screenread off the distancescale. In this way, corning down through the cloud towardssomewhat similar to a television screen, withthroughradar's " magic eye," theaircraft the runway in use.He is told by the air-a distance scale down the centre.On thiscan come down safely through cloud and field control officer, over the R/T, when itscreensharplightindicationsfromtheapproach the runway. is his turn for landing approach and is givenground equipment, Eureka, appear.These These, then, are some of the aids avail- other information, such as the height of theindications are known as " blips." Theable on your B.O.A.C. flight-the eyes and cloud base. ground equipment is quiescent untilears of the air.There are others,all,to These radio aids to navigation are installedactivatedor" triggered "bytheaircraftsomeextent,developmentsofprinciples throughout the Empire airroutes, and, inequipment, when it sends cut impulses in aalready described, and as you continue on addition; radar equipment is being shippedpredetermined and known direction.Theseyour journey to the Far East you imagine overseas and placed along these routes and,arethe" blips,"alreadydescribed,and the pilot and radio officer talking to the con- indeed, is already working at many points.according to whetherthey appear left ortrol tower or listening to signals indicating Such words as Rebecca, Eureka and Babsright of the distance scale, the heading ofthey are flying " on course " and you are may be used by the radio operator if youthe aircraft can be altered until the " blips "reassured to know that, rlthough on stages have a chance of talking to him at one ofare centralised and the aircraft's distance fromof your journey you may be out of sight your stopping places, but you'll find he isthe beacon can be read off from the scale.of the ground, you are not out of touch.

letter -box flap to come into easy contact with it when the flap is pushed inwards. The An Effective Alarm idea is for this contact of the brass strip and the clock -spring to complete the circuit that Constructional Details of a Novel Electric Alarm rings the bell in the bedroom.Before the screw used for securing the piece of clock - Operated from a Front -door Letter -box spring in position is finally driven home, take By C. BRADSHAW the other length of bell -wire and wrap one end firmly around it. We now have one IN these days of acute shortages there areare fixed firmly to the flap, then replace thelength of bell -wire attached to the flap of few who have nbt experienced the diffi-metal facing of the letter -box to the frontthe letter -box and another attached to the culty of securing a reliable alarm -clock.of the door.The flap should swing freely,piece of clock -spring fastened to the back of Even if we are fortunate enough to comebut if the brass strip has been allowed to ' the door. Using a few staples, run these across one of these very essential nuisances, two wires diagonally across the door from the it usually turns out to be very poorly con- Circuit places where they are fixed to the top right- structed from the flimsiest material, and most Bell Panel Breaker hand corner of the door, then across to the unreliable in performance. Switch jamb. Ifindthatrunningthewire In my own case, if I can be aroused some- diagonally thus eliminates any tendency for where around 6.3o in the morning on work- itto wear and break, through the opening Bedroom Wall Battery Held and closing of the door.After crossing on ing -days (other days don't matter so much) by Clips I have no difficulty at all, outside the usual to the jamb the wires can be run vertically scramble forbuses,inarrivingat work up the wall,passing through the ceiling punctually. It was only recentlythatI into the bedroom, after a hole has been made noticed that my daily newspaper is slipped in the ceiling for the purpose. through the letter -box at approximately that Ceiling time each morning. Now, I thought, ifI Connections can make that letter -box ring a bell in my When the bell -unit, switch and battery bedroom as the newsagent delivers his paper have been fixed to the base -board, the alarm through it each morning then I will have a Staples is wired in the following manner :Take one very effective alarm.I have evolved a very lead from the letter -box and connect it to the simple system that can quite easily be put positive terminal of the battery.The other into practice by any handyman. The follow- lead is attached to the left-hand bell -terminal. ing components will be required: A short -length of wire is now connected to right-hand terminal on the bell and the other a electric bell. end is connected to one point of the switch. 6 or 7 yards of bell -wire. Another short length is run from the remain- a circuit -breaker switch. ing switch -point to the negative terminal of . a piece of clock -spring about 3ins.long and -gin. wide. the battery.When the alarm is ready for istrip of brass about skins. long and kin. action the switch is left in the on position. wide. Since the alarm will only continue ringing a base -board for holding the bell, switch whilst the flap of the letter -box is open, it holding the is essential that some method of preventing and battery, and 2clips for Portionof Brass Contact the newspaper from passing right through battery in position on the board. Clock Spring Soldered to Flap Having obtained these components, pro- the letter -box and falling behind the door General arrangement of an electric alarm isintroduced. This can be done very ceed in the following manner: operated by the front -door letter -box flap. simply. Take a piece of cotton material Contact Strips about Tins. wide and a8ins. long.Tack one First cut the bell -wire in two and bareprotrude too far over the edge it will impedenarrow end of this material about sin, above about sin, of each end. Next remove thethe movement of the flap.If you find thatthe letter -box and tack the other end of the wholeletter -box cover complete withits thishas happened, remove theletter -box strip about sin. below the letter -box.This hinged flap, through which the letters, etc.,facing and file the brass until the necessarywillpreventthenewspaper frombeing are delivered, and to the bottom left-handclearance is obtained, then replace. thrust too far through the letter -box and corner of the flap (at the back of it) solder Now take the Sin. piece of clock spring,the brass contact will thus be kept on the the skin, strip of brass horizontal with thewhich should have a small hole bored aboutpiece of clock -spring causing the alarm bell bottom edge, but protruding about kin, overkin. from one end so that it can be screwedto continue ringing until you get out of bed the side of the flap.Fix one end of the bell -into position.The spring should be curvedand switch off at the base -board. wire at this junction also, so thatitis into about a quarter of a circle.It should be One thing to remember: see that you put goodcontactwiththestripofbrass. screwed to the back of the recess in such athe switch to the on position before getting Make sure that the brass strip and the wiremanner as to allow the brass strip on theinto bed each night. 86 NEWNES PRACTICAL MECHANICS December, 1947 Electric Light and Power Installation -2 Further Notes on Layouts andWiring Methods. By S.T. CORNER ITis the general practice to " run " steel (Continued from page 13, October issue.) or screwed securely in the fitting to which conduit for electricity installations before it runs; but it must not project too far into the builder lays the flooring or plasters the joint, or the sharp edges will cut the the walls and ceilings.In the trade this is wires when they are being drawn through. called " carcass " wiring.The work must, The most satisfactory resultsare obtained of course, be done in co-operation with the bysecuringthefittingstemporarilyin contractor, or the whole building operation position and then measuring the distance may be disorganised. between them; by adopting this method, the For all good class work the conduit instal- tubing can be marked off and cut exactly to lation is completed before the wiring is run.' the required length.Before final fixing, the Itisadvisable togive the house time to dry out, and to wiretothefittingsjust fi1 before painting and internal decorations are opii started.Wires should not be drawn in until tt% qi11(filik allnailingisfinishedandthehouseis reasonably dry. Tubing should not be starteduntilthe ft/I/WWI( roofis on the house and the dwarf walls and joists of the lower floors are in position. O Usually the tubing on the upper floor is run first, and the work continued downwards, but Butted Together the wiring of the upper floor is done lastly. By that time the middle floors will have been laid and can be used for ladders and other (1)k.114tkOk\kkktkm.0.111\1W11\t1,,%\t necessary appliances. Coup/er Locked Fig. 9.-Three positions of a running coupler. ends of the tubing should be carefully filed Main and rounded in the bore. Switch Saddle Clamps

All tubing should be secured and sup- Cram pet ported at intervals of not more than three feet, by saddle clamps tojoists and other woodwork and by crampets to brick walls, as shown in Fig. 7a.Spacing saddles are used Fig. 6.-Showing position for " rising main."to secured tubing, where it runs into a fitting, to bring it into alignment with the threaded tape through it to make sure that it will goinlet,as shown atFig. 7b. There are, of round the bends and there are no obstruc-course, numerous kinds of fittings for various tions in the conduit.To remedy any faultspurposes, some of which were shown in the after the plastering has been done would beprevious article; other fittings are shown in a costly business.All inspection covers mustFig. 8.Fittings with inspection plates sim- be carefully replacedto excludedirtand plify wiring drawing and they should be damp while the plastering is being done. used at all angle turns in preference to plain Inferior electrical installation work can beelbows.When a bent tube is used to turn as dangerousasleaking gas pipes. Unfortunately, muchwiringworkis SpacingSaddle cheap and shoddy, and thiscausesconsiderable Fig. 7.-Methods of fixingtubing. troubleinafew years after installation.Cheap Locating Lighting Points slip -intubingisoften Before starting any work, it is most essen-usedundertheroof, tialto study the plans, so that the exactwhich, next to a cellar, is locations of the lighting points and switchesthe dampest place in the Inspection can be fixed by accurate measurement.Onehouse. In many instancesInspection Tee E/ bow of the most important items is the choice ofitislaid loosely across the position for the " rising main," Fig.6. the joists with no clamps. This conduit carries the main feeding wiresIfthe space under the from the meter board to each floor level.roof is used for storing Owing to the fact that the meter board isboxes, the least movement usually fixed under the stairs, the run to the ofthe conduitpullsit first flooris often the most awkward.Allfrom the fittings.The Such tubing must be given ample bends andsharp edges of the tubes a junction box provided on the landing in acut the insulation of the convenient position to draw in the wires.wires and cause short cir- Alternatively, intermediate inspection boxescuits. Most fires originated must be fitted at awkward angles and bends.byfusingaredueto Wiring is drawn into the tubing with apoorelectricalworkof wireman's " snake," which consists of a coilthis kind. of spring steel wire or tape, with a brass All tubing should be CircularType CircularType ball at one end and a loop at the other.Itcut to exact lengths is advisable to test all tubing by passing theso that it can be gripped Fig. 8.-Inspection elbows and T -pieces. December, 1947 NEWNES PRACTICAL MECHANICS - 87

a corner it should be as generous as possible, Conduit is usually sunk in the brickwork tonotchedneartheircentres,Which would and of never less than four inches radius.a depth of about halfits diameter, whichweaken them where the greatest strain has to All runs must be planned so that 'the drawshould bring the face of the box level withbe taken. wire can be passed from point to point. the finished plaster surface. The boxis secured in position and the conduit run into Running Couplers Wooden Switch Blocks Long lengths of tubing for straight runs, The useofwooden blocksforfixing or tubing in such a position that it cannot be switches and ceiling roses is fairly common, turned, may be joined with a running coupler but itis neither good practice nor a really as shown in Fig.9. One conduit endis safe method. A more satisfactory way is to use screwedtoalengthsufficienttotakea iron -clad fittings, as shown in Fig. iIa. These coupler and locknut.The two conduit ends are screwed or otherwise secured to the end are then butted together and the coupler is of the tubing and ultimately set in the plaster. run back on to the other length of tubing; By this method the switch does not need a the locknut is screwed tightly against the end wooden surface mounting block, and the fit- of the coupler to prevent it turning. ting is therefore much neater because it does II Where tubing is run into junction boxes or ti not protrude above the wall face. When other fittingsthatare not threaded either adopting the former method a wooden block, of two methods can be used to secure it in about 4ins. square and tin. thick,isnailed position. By thefirst method, asleeve A it to the brickwork, and the tubing terminated couplerisscrewed on tothe end of the with a vulcanite or rubber bush to protect the tubing, and a screwed bush, passes through wires, as shown in Fig. isb. the holein the junction box and screwed into the coupler, as shown in Fig. soa.The rounded end of the bush prevents the wires Light Point, from chafing.A second and simpler method Several different methods can be adopted isto run the tubing through the hole in for light points.A ceiling point canter - the box and secure it with two locknuts, one on the outside and the other on the inside, Fig.so.-Section see Fig. sob. of a junction box -Floor BOardt It is sometimes necessary to join two runs showing connec- of tubing of different sizes, or to join up to a tions for tubing. junction box that has a larger opening than the tubesize. In both casesareducing

Correct Wooden Conduit Fixing Term,nal Block

Fixing Box

Incorrect Conduit 11

End to Sortgh r.

Fg. H.-Methods of mounting switches. Fig. t2.-Various methods of anchoring light points to a ceiling. nipple is used, which is threaded externally it. It is advisable to cement round a largeminate in an iron flush box, which has two to fit the larger screw thread, and internallybox to keep it square with the wall.Wheretapped holes for fixing the ceiling rose or to take the smaller, as shown in Fig. loc. junction boxes are fitted to joists, before thependant. The box must be securely anchored floor boards ate laid, arrangements should beon each side with battens to keep it in place, Carcass Wiring made with the carpenter to make traps thatas shown in Fig.12a. If the point ends can be easily lifted to facilitate wiring.Allwith a bushed tubeit must be terminated Simplicity should be the keynote ofallruns should be planned so that the cablesat the under surface of the ceiling, -Fig. x2b. carcass wiring, and the runs planned with Where the point is dropped from the back of as few junction boxesaspossible. Thismay be passed from the junction box to out- method is not only economical in the cost oflet points without the aid of a draw wire.Ita junction box, blocks must be provided to fittings, but italso reduces the number ofshould be necessary to use a draw wire onlycarry the ceiling rose or pendant.If the traps to be made.Bends are easy to formwhen there are several bends in a run.Allpoint is run from a bend the tubing can end (but they must be generous) and are prefer-conduit runs under the floor boards must benear a joist, and this may be used as a fixing able to a multiplicity of connections.Theykept near to walls so that the joists are notpoint, Fig.I 2C. should be so -placed that the wires can be drawn into and out of the tubing with a minimum of structural disturbances. Bow Bells., By A. M. L. Junction boxes should be arranged so that they arc in the least conspicuous positions; WE say, in London, that anyone bornfingers and, without letting the string touch where likely to be unsightly, the face of the within sound of BowBellsisa anything, bend forward and swing the poker box should not protrude above the plasterCockney. I am not fond of bells myselfuntil it taps the table. surface of the wall.In such cases the con-nor of spherical decorations, forall these Nearly everything hasits own rate of duit must be sunk into the brickwork farsuggest problems to me.And bells are sonatural oscillation in this way. A wine glass enough to make this possible.The positionsavage that Ifeel ashamed of them. Tom-tomsrings a certain note, and if that note is played of the groove isfirst marked on the brick-on a big scale. it might break the glass.If there were no work with a carpenter's pencil, and also the Please do nottell me about the Bushfriction, a child could upset a battleship by position of the recess for the junction, switchtelegraph, the Indian rope trick and thepressing regularly upon its side. box, or wooden fixing block.The chase, orMango tree ;I, too, know dozens of people Flames are very sensitive to vibrations, channel,isneatly cut with aspecialtool who know someone who saw them.I willand if you arrange a small gas jet from a tiny known as an electrician's chaser, or with agive you instead an amusing little experimenthole, fitted via football bladder in order to bricklayer's bolster.Both tools resemble veryby which you can hear bells as beautiful assmooth outanyirregularityofpressure wide cold chisels, and they must be reallythose of Notre Dame or St. Paul's. between the jet and the main, the flame will sharp.A small chaser is just the width of Obtain a fairly heavy poker and at one endbecome sensitive and will duck if you clap a brick,i.e.,3ins., and is used to line outtie a piece of string, leaving ends about s8in.your hands or hiss.Even a bunch of keys the positions marked; the pieces of brick -long. At each end of these ends tie a smallwell rattled will make the flame bob.With must be carefully removed.Extreme pre-loop about }in. diameter or less into whichlow pressures and the flame enclosed in a caution must be taken not to dislodge thethe forefinger of each hand fits comfortably.chimney youcan makeitsinglikean bricks. Now press your ears tightly shut with yourorgan. NEWNES PRACTICAL MECHANICS December, 1947 A Mobile X-ray Unit problem of the satisfactory X-ray THEexamination, in situ, of welded high pressure pipe lines has been solved by Philips Electrical, Limited, by the pro- duction of a fully mobile X-ray unit. Completely equipped for immediate service, this unit is housed in a 4-5 ton van, the body of which is divided into compart- ments which accommodate all the necessary X-ray equipment and provide a complete darkroom service. The necessity for this apparatus has arisen in connection with the urgent need for the provision of power generating stations. The testing of materials for these projects takes time, which, under present conditions, can ill be spared. Any means that can be devised therefore for Speeding up the neces- sary test inspection withoutloss of efficiency is greatly to be desired.

Complete Macro 30o inspection unit assembled at the foot of the ramp at the rear of the van. (Philips Electrical, Ltd.) X-ray Inspection reflectors having a flat opal glass front. Equipment Ventilation The rearpart of the vanhousestheX-ray Ventilation of the darkroom is effected by equipmentandissep-means of two refrigerator -type .ventilators arated from the forepartfitted in the roof of the van and also by a by a light -tight partition.Vent-Axia exhaust fan fitted in the forward The equipmentitselfis bulkhead of the darkroom.' heldinpositionduring Special cable and hose drums are housed transit by means of in compartments below the chassis of the spring -loaded attachments. van, which, when coupled to external supply For ease in unloading,sources feed the various water and electrical the tailboard of the van circuits. is designed as a double - A 34 -gallon storage tank is housed above hinged ramp which, whenthe driver's cabin to boost the water pressure

Film loading bench with built-in cassette racks and film storage cupboards.(PhilipsElectrical, Ltd.) Messrs. Stewarts and Lloyds, Ltd., one of lowered, gives a gradient the largest metal tube makers in the coun-of r in 6.The h.t. gen- try, have recently taken delivery of the first eratorsfortheX-ray of these Philips' mobile X-ray vans. They equipment are moved by will use it for the routine examination, in small two -wheeled trollies. situ, of their welded, high pressure pipe lines The type of equipment to ensure thatthe welds arefree from supplied for the van is a defects. Philips Macro 30o inspec- tion unit, capable of ex- Internal Layout of the Van aminingsteeluptoa The dark room arrangement consists of the thickness of 4iin. following: A special film -loading bench for the stor- age of X-ray films, chemicals, 'cassettes, etc.Lighting The processing unit and a wash basin ; Thelightinginthe special a Philora 'viewing lantern and facili- dark -room is concealed in ties for the quick drying of X-ray film. the angles of the roof and .Stainless steel tanks for processing, each consists of six toin. tubu- Stainless steel processing tanks and film viewing desk fitted with with a clip -on, spill proof lid. lar strip lights fitted into " Philora" viewing lantern.(Philips Electrical, Ltd.) December, 1947 NEWNES PRACTICAL MECHANICS 89 Studies in Electricity and Magnetism A Discussion on Some Fundamental Electrical and MagneticQuantities

THERE areplenty of excellent books By H.REES, A.M.I.E.E. terminals of the dynamo will similarlybe covering " Electricity and Magnetism," R -25o soo =2.5 ohms-of which the two and a thorough study of the subjectthese " p.d.s "in a typicalcircuit, usinglines account for 2' 0.05 =0.5 ohm. willalwaysbe worth while. This, ofsymbols such as VI, V2, etc. Finally,theinternalresistanceof the course, applief to those readers interested in Of course, " voltage " generally signifiesgenerator-armature winding, brushes, etc., electrical matters. only one thing-the voltage or potential -isshown asa" lumped "resistance Ra. But there will always remain a real needdifference across a pair of lines, or a pair ofStrictly, of course, this is an internal resistance, to supplement bookwork by lectures, notes,terminals.But in setting out to use Ohm'sand cannot be put extraneous to the armature or articles, particularly if these are designedLaw, itis hard torealise that " V " canas indicated. By doing so, the armature itself to give a practical approach. to theoreticaldenote other things.Also, the concept ofmay be supposed to have no resistance, and topics-or to relate " theory " to " things,"volts " dropped "-giving rise to a potential -cause no voltage -drop, when the reading of such ascircuits, machines, lamps, heaters,difference across some part of a circuit-255 volts from point B to earth will represent instruments, etc. is often peculiarly difficult to beginners. the induced voltage in the armature windings. In writing, I have tried to show the need In using I ==V,,R, it is commonly supposed Evidently we have a further drop of 5 volts for " thought " even on relatively elementarythat V ,mat represent the supply voltage.in Ra-making the terminal p.d., 255 v. -5 v. questions. It will be best-if space is availableBut if R is the resistance of a cable, possibly= 25o v., when, Ra = 5 isoo == o.o5 ohms. -to discuss a few topics adequately, ratherforming only a small part of an entire circuitIn an actual dynamo there willbe other than attempt the impossible, e.g., to condensenetwork, " V "isthe drop, the potential -causes than " resistance " for a falling voltage the contents of a fair-sized text -book withindifference across that part-usually only a fewcharacteristic ;for example, the reduction in the space of a few articles ! volts. shunt -field current if the . p.d.falls by, say, To start with " Electricity," I feel I cannot .0 volt due to resistance-the overall resultant do better than to take for my theme certainNumerical Illustration fall will be more than t volt. In non-interpole aspects ofOhm'sLaw-things which Let us give values to the symbols of Fig. 2a,machines armature reaction may weaken the instructional experience indicates constantlyas in 2b. effective flux which the conductors cut, and need elucidating. 'Suppose a voltmeter V is connected betweenso reduce the e.m.f. generated. The big difficulty to beginners, and manyvarious points and " earth "-we have indi- more advanced students, is not with expres-cated 'an" earth "in order to make theElectromotive Force sions such as" I -V, R. The worry isproblem fairly typical of the sort of thing Otherwise, the 255 volts is the total e.m.f.- not so much Ohm's Law as in its conceptsapt to be troublesome to a beginner, and toor the total volts available for overcoming -the ideas or intangible, unpicturable quan-illustrate important ideas regarding " earthedall resistancesin thecircuit,internal and titiesthesymbolsstandfor : pressure,mains." The voltmeterreadingsareas external. electromotive -force, potential -difference, voltage -indicated. If we neglect the effect upon the field - drop, voltage -to -earth,etc. What does the reading of " 5 volts " fromexcitation,andofarmaturereactionin negative line to " earth'indicate, when theweakening the field,the load current will

Fig. t.-(Left) Is there a " drop 'or a " loss " 'of 240 volts in a 240 - volt lamp Fig. 2.-(Right) Study 240 of voltmeter indications v. (21') at various points in a two -wire earthed circuit. vs Fall Of Potential (a) 4PF (b) supply is at 240 volts ? What current is carriedhave no effect upon the generated e.m.f.--. Different Meanings of Voltage . by the lines? provided, too, the speed remains constant. Itisusefulsometimesforexplanatory Because theearth forms an additional Hence, unlike terminal potential -difference, purposestoaskapparentlynonsensicalconductor, the voltmeter from point E tothe electromotive -force may be regardedas questions, if they help to clarify our ideas-earth is virtually connected right across theconstant, and independent of loadcurrent. and not all questions which appear so areends of the negative line, from E to A. ThereMathematically : nonsense. is a potential -difference of 5 volts between E.M.F., E- One, which I recall asking at one time wasthe ends. The end E is 5 volts positive withTotalrate of change offlux-linkages/roe.. this :if 240 volts are " lost " (dropped)inrespect to end A-or, what is the same, end BLvj los volts. the filament of a 240 -volt lamp, Fig. 1, whatA is 5' volts negative with respect to the far drives the current back along the negativeend E, though A is at zero potential relativefor a single conductor. wire ?For that matter, what drives it alongto earth. We shall devote some space to this basic the positive ?For, remember, " voltage ' Now, if there exists a difference in potential offormula presently. As long as the flux - isa sort of electric pressure ; a" driving5 volts between the two ends of a single isolateddensity (B) and the velocity (v), are constant, force,"maintainingelectronsinmotionwire, how is this brought about ?Clearly,the induced e.m.f. will be independent of throughout a circuit. there must be a loss, a drop of 5 volts in thisany drop in resistances. The question is useful because the answersingle conductor-in overcoming its resistance. In the case of a battery, the generated will bring out clearly the different meaningsThe current is given by I =V R, where V -e.m.f. will depend only upon the chemical for composition of the electrodes and electrolyte.. to be attached to the word " voltage " ; the drop, and R =the resistance of the lineAgain, there may be a large voltage -drop due example, the fact that potential -differences=0.05 ohm. Hence, I =5,0.05 = too amperes.to internal resistance, affecting the terminal exist across other parts of the circuit. Alternatively, if as is usual V denotes thevolts, but not the e.m.f.In many types of Unless it is clearly specified what particularline voltage, which is 240 at the load end,cells, however, " polarisation " will give rise " voltage "is meant, the word can signifyand R denotes the total resistance of a loadto a counter-e.m.f. opposing the main e.m.f. many things:(a) the total e.m.f. generated-say, a large number of lamps in parallel-generated, so the result will be equivalent to atthe source by a battery or a dynamo ;itisalsotrue towrite :soo A -240,'R,a reduction in the total e.m.f. developed. (b) the terminal p.d. at the generator ;(c) thewhence R -24.0 'Pao (RV, I) =2.4 ohms. terminal p.d. at some point in the line, such as At the generator end the " terminal p.d."Potentials " To Earth " the distant end ;(b) the potential -drop in ais shown as being 25o volts.The extra so volts Observe that with the. end A tied to earth wire or cable ;(e) the internal potential -droprepresents the drop in the two lines.The-as shown in Fig. 2b-the potential of the at the source ;(f) the potential -to -earth atcurrent of too A. will be the same everywhere,negative line " to earth " will be of positive various points in a system.Fig. 2 indicatesso the total resistance across the externalsign everywhere along its length up to point A. 90 NEWNES PRACTICAL MECHANICS December, 1947 Thus at point E, the potential is 5 volts This is an easy expression to use, and, as Peripheral velocity, v = 2orrn, cms. per sec. positive with respecttoearth ;half -wayalways, a concrete example will make things a = 2nr x Rpm/6o, cms. sec. along the line, it will be 2.5 volts positive ;bit clearer. This shows that for a given length of active if a voltmeter had one lead connected to Suppose, then, we had a magnetic fieldconductor and a given speed of rotation, the earth whilsttheotherconnectionwaswhose strength was known to be ro,000 (ore.m.f. will increase with the diameter of the gradually slid along the negative line towards ro4)" magneticlines "ineverysquarearmature-or, what is signified in design, a A, the reading would successively fall fromcentimetreofspace-probablythemostlower speed tan be employed for the same 5 volts, until, at A, there is no difference ofdifficult job will be to arrive at anything like avoltage(obviouslythespeed hastobe potential relative to " ground." reasonably accurate estimate of the " fluxreduced the larger the armature, to restrict Here we have the curious fact that andensity," but we cannot go into that now. centrifugal forces). earthed cable or line which is carrying current Let us take a piece of copper wire of The circumferential velocity is uniform, but may have a small potential -difference relative" activelength " L= tocentimetres,i.e.,our conductor will not be equally effective to ground of opposite sign to the potential ofwhatever the actual length,ro cm. will bein generating an e.m.f. at all positions during the line itself relative to another line.Simplyactivelycutting magneticlines. Letusa revolution-or a half -revolution. a matter of " volts -dropped," of course, butproceed to " cut linesby moving this wire The velocity v is fully utilised when the thispointregarding" signs "isworthacross the field at a uniform velocity of r,000 thinking over. conductor is opposite the pole -centres, and cms. per sec.-another difficult quantity toso moving exactly at right -anglestothe If end E were tied to earth instead of A,estimate, but easy enough when dealing withmagnetic field, as in Fig. 3a.This is the a moving -coil voltmeter (the type of instru-the circumferential velocities of armatures. positionof maximume.m.f.,and,unless ment which will indicate + and - polarities) As an experiment, you may well think ourotherwise modified, the BLv formula always would show end A 5 volts negative to earth-procedure somewhat academic or far-fetched !gives the maximum value. as might be expected from the fact that endWhat is interesting, however, is that a volt- E was positive when the earth was located In a position such as Fig. 3b, where the meter joined across the two ends of thatconductor makes an angle 0(radiansor a:.A. conductorwillregisteradefiniteinduceddegrees) with the position of maximum e.m.f., The opposite reasoning would apply if thee.m.f.-when aconductor " cuts " acrossthe velocity is still v cm. per sec. tangential + line were earthed, at C or D. magnetic lines of force, its state of electricalto the armature, but this velocity is in a potential is altered. direction oblique to the horizontal direction What is more interest-of the field.It has, however; a " perpendicu- ing at the moment is tolar component," v x cosine 0 (or v cos0), get some ideaof thewhich will be less than v itself.Hence the " amount " of inducede.m.f. equation becomes voltage.Our quantities B are: B - o4, L - ro cm., e r x cos 0. and v= roa cm/sec., so ro,Lv that: If, as is usual, the angle 0:is specified from the position of zero e.m.f., the multiplier E -rat x x roa 108 changes to : 508 B Lv ro= rvolt. e = x sin 0 (a) (b) ro8 Fig. 3.-Rotation of a conductor in a stationary magnetic field. Quitearespectable Thus at 0 = o° (conductor in the neutral e.m.f.inone singleposition), sin 0 = o, and therefore -E = o ; Much more could besaid on simpleconductor.If we added many more, with9o° later, sin 0 = sin 9o° = I, and E will earthing problems.As a theoretical pointr.o volt induced in each, and connected thembe the maximum value given by the BLv which did give rise to much learned argumentallin series to form the " turns " of anformula. among certain radio academicians, the readerarmature coil, then add still more coils in At 18o' the sine again becomes o.From might consider from our illustrations whetherseries, it is not too difficult to get some idea18o° to 36o° itwill be negative, signifying a potential -difference across part ,of a circuitofthequantitativeaspectsofarmaturethe e.m.f. has reversed. has the same or an opposite sign to the applieddesign. Since 0 makes 36o°, or 2nr radians, every e.m.f. ? Or, if we had the means in a laboratory ofrevolution, the sine will pass through two As a matter of some practical importance inmeasuring accurately the velocity v (possiblyzero values, and two maxima of + ir and -1. using a voltmeter to locate " earths," supposeits average value), then, knowing E and theIt follows that an alternating e.m.f. is being Fig. zb represented an insulated system, andactivelength of conductor L, we couldgenerated, varying sinusoidally between the that an earth occurred somewhere along thecalculate the " field strength " B, i.e., two maxima of +E and -E. In mathematical + or - lines, not at the ends. The foregoing E xIoa language, the voltage will be a " sine function discussion should show how a low -reading Flux Density, B = Lv of time." instrument might be used to find the approxi- mate location of an earth at any time, but in The e.m.f. E may be measured by a precision If we writeBLvi'1o8 = Emax = the the case now mentioned the meter wouldvoltmeter or calibrated galvanometer, whilst Lmaximum e.m.f., we getthewell-known show a negative reading (or reversed reading)needs nothing more than at certain parts. Can you see why ? a centimetre rule.I am Reverse To return to our nonsensical " query :not suggesting that flux - Motion Motion it should not be difficult to understand wheredensitiesaremeasured quite in this crude. fashion, a voltage is derived from to drive the current N N " along the + or - lines " !Any resistance,but ithelps to answer a S S anywhere in the circuit, simply " drops " thequestion sometimesput M M amount of pressure required to drive theby zealous students : How current along that particular part. are magneticlines (a) (b) But I can see many beginners still asking :" counted " ? Besides," MagnetismFig. 4.-A simple illustration of " Lenz's Law "-e.m.f. and current How can it be -true to say that 240 volts are induced in a short-circuited coil by the motion of a magnet. " lost " across a lamp-or whatever the loadand Electricity " become may be ?It requires an effort of the imagina-more instructive when it is tion to see how " volts " can possibly befully realised that r.o volt can be generated in aalternating expression : absorbed, and, of course, it is really a questionpiece of wire approximately 4in. long, if moved e = Emax sin 0, of energy being converted into heat. across a strong magnetic field at a " speed "whichmathematicallyconveysasmuch I must leave the subject here, to go on toof about 28ft. per second. information as a graphical sketch of a sine - one or two magnetic problems. wave, when it is remembered that " sin 0" Alternating E.M.F. changes sign and so shows reversal every The " BLv " Formula Our objectisnotso muchtogivehalf -cycle. As an introduction to many elementary" formula: " and to see how well they " work " design questions, it may be of interest towhen applied to concrete examples. TheThe" Velocity of Light" consider the" BLv "formula mentioned"- BLv "expressionstates awider truth, Our basic expression offers more food for earlier. applicable generally to many things besidesthought. If a straight conductor of length L centi-a wire moving across a magnetic field. Itis notsostrangeperhapswhy metres moves across a magnetic field of density But a little more about the " equation" for" imaginary " lines of force, or their numerical B lines per square centimetre, at a velocity ofa moment.If the , conductoris one of aspecification, should give results which agree' v cm. per second, the induced e.m.f. will be : large number fixed at a radius r cm. on thewith the readings of voltmeters.It does E (volts) -BxLxvor BLv x ro-8. periphery of an armature making n revolutionssuggest that mathematicians and physicists per sec., Fig. 3a, we get : have managed things very well, even though December, 1947 NEWNES PRACTICAL MECHANICS 91 voltmetersandammetersarecalibratedtextbooks-and Ihave known students toan extra " pull " has to be exerted by the against standards based upon the electro-groan audibly when listening to dissertationsengine to overcome the increased magnetic magnetic units of measurement. on electromagneticinduction. drag on the armature. Were this not so, the The formula we have been discusging can This state of hopelessness was at the samesamedriving -power(horse -power)would be translated into the more familiar quaritita-timeheightened, andrelieved, when thesuffice on full -load as for no-load. tive ideas of Faraday's Laws. name of " Lenz," was mentioned.But, if Again, the electric motors used for traction If a conductor of length. L cm. movesanything, Lenz's Law is a wider generalisationcan be utilised as a most effective " electric " v cm."in one second, it sweeps out anthan Faraday's.In one sense it is a particularbrake," by quickly shutting -off the main area A of L x v sq. cm. = Lv sq.cm.,case of the Law of Conservation of Energy.power supply and manipulating a control and since there are " B lines of force " toThere are several ways of enunciating thewhich changes the circuit connections so as each square centimetre, the total number ofprinciple. The most usefulforpresentto " short " the machine upon itself-uSually lines cut across in r sec. is obviously B Apurposes is the following :The direction ofthrough a controllable amount of resistance. = BLv lines.Thus the formula reducesan induced e.m.f. (or the resulting current) isThe " momentum " or kinetic energy of the to : such as to tend to stop the motion producing it.vehicle is dissipated as heat in the resistance Total lines cut per sec. The space that remains will not permit us=much the same, of course, asit would E (in volts) = to do more than glance at a few examples ofotherwise be dissipated in the form of fric- ro8 the law. tionalheat ina mechanical brake. The i.e.,t volt is the e.m.f. generated if a single Perhaps the best known is eddy currentmotor(s)actasgenerators(" regenerative conductor cuts too million (re) magnetic" damping ", or " braking ", in meters. Abraking "), supplying a heavy current which lines every second. light aluminium disc, or an aluminium coil -retards the motion producing it. The C.G.S. or electromagnetic unit (e.m.u.)former closed upon itself, moves in a strong To conclude this articlewe will take a of e.m.f. is much smaller.Theoretically, it ispermanent -magnet field-under theactionsimple magnetic illustration of the Law.In thee.m.f.generatedifaconductorcutsof some other driving force such as the coilFig. 4a is shown a short-circuited coil c wound " one line of force " every second.It mayin a moving -coil meter.It cuts magneticon a soft -iron core.A bar magnet (or other not be so easy to conceive physically howlines. A small e.m.f. is induced, which giveselectromagnet) M is brought up towards c, that could be possible-a single magneticrise to a circulating current in the metal-the direction of motion being as indicated by line " cut " in one second or in any finiteeach " conductor " may be regarded as a thinthe main arrow. What must be the direction interval of time ?There are very weak fieldsstripof metalshort-circuited upon itselfof the induced e.m.f. in c ? where the e.m.f. developed would be equiva-through the rest of the metal. The aluminium lent to such a performance, but somehow theformer of a moving -coil instrument forms a Apply Lenz's Law.A current will flow concept of isolated " lines of force " (withsingleshort-circuited" turn." in the shorted coil in such a direction as to spaces between where there are no lines) The direction of the induced e.m.f. andexert a magnetic force on M " trying " to does not seem entirely satisfactory. current must be such as to tend to stop thestop its motion.The induced e.m.f. will Another unit of e.m.f.-theelectrostaticmotion :in other words, the magnetic fieldhave the same positive direction as the current. unit (e.s.u.)-is equivalent to 30o volts in theset up by the induced current will be such asWhat direction is this ?Clearly an induced current as indicated by the arrows on the coil practical units, or to 30o x Io& = 3 ;< 10uto exercise a " magnetic drag " opposite to the e.m.u.'s,i.e.,theratio,electrostaticunit,driving torque, so giving a braking effect. turns, giving the ns polarity shown in the electromagnetic unit = 3 X 1010. Additionaldamping canbegiventhesoft-iron-the n -pole next to the N -pole of Readers who know alittle physics willmovement of a moving -coil instrument whenthe magnet causing magnetic repulsion. recognise this curious figure.It is the velocityit is to be packed for transit by short-circuiting In 4b the bar magnetisbeing moved of light in centimetres per second.Whateverthe two main terminals with a piece of wire.away from c-direction of motion reversed. electrical quantities are considered, an electro-On top of the ordinary effect of the coilThe polarity due to the induced current must static unit divided by an electromagnetic unitformer, the coil turns will then provide anreverse, becoming sn, and such that s attracts will always give the same answer-the speedextra heavy damping to prevent the pointerthe N of the magnet-again " opposing or of light in free space ? swinging about. tending to stop the motion." This can only Take another example of Lenz's principle.come about by reversal of the induced e.m.f. Electromagnetic Waves When a heavy load comes on a generatorand current. We cannot go into the significance of this fact now, but itis interesting to note that electromagnetic waves-light, heat, wireless waves, etc.-all travel through free space with the same velocity :186,000 miles per sec. Sheffield Steel - 3;- ro" cm./sec. Our BLv formula could be employed, for instance,tocalculatethe9.m.f.induced in a vertical aerial fixed upon a chimney or in the back garden. The aerial wire is stationary, but is " cut " by the horizontal magnetic field of a " wireless wave" from somedistanttransmitter-it would also be possible to look at matters from the viewpoint of a vertical electric field, such a wave being said to be vertically polarised. In terms of horizontal magnetic lines, the " conductor "may be regarded as being cut by a field of maximum intensity " B " or " H," sweeping past at a velocity of 186,000 miles per sec. The induced e.m.f. calculated by a formula ofthe form BLv,' to' would thus be the maximum or peak value-the e.m.f.itself will be alternating, since from the present standpointthewave may beconsidered stationary in space, whilst " B " undergoes sinusoidal alternating changes.Often, radio field strengths are given " R.M.S. Values," when the estimated induced e.m.f. would be that indicated by an a.c. voltmeter capable of giving correct readings at radio -frequencies. Of course, the magnetic and electric fields at some miles away from a wireless trans- mitter are exceedingly weak, but the "velpcity" (or " rate of change ")islarge, giving an e.m.f. in a receiving aerial of the order of microvolts (pV)-millionths of a volt. Lenz's Law It is hoped that Faraday's Law will look Sheffield is now forging ahead to provide the steel badly needed for world markets.Our illus, somewhat more attractive the next time the tration shows an important operation in the heavy forging section at Firth Brown's Steel Works, " dry bones " of the subject are tackled in Sheffield. Two ship's propeller shafts being forged out of an 83 -ton ingot in the 6,000 -ton press. 92 NEWNES PRACTICAL MECHANICS December, 1947 An Adjustable Focusing Stand ConstructionalDetails of a Useful Unit for the Amateur Photographer

By L.C. MASON THIS stand was evolved for use when copying or photographing small objectswhichrequiretheuseof double extension bellows or extension tubes. It is actually used with a double extension plate camera, but is applicable in all respects to any other camera set-up for close range work.It was found that when trying to focus with the bellows almost fully extended, the point of sharpest focus was difficult to determine, as a considerable movement of the lenst appeared to make little difference to the sharpness of the image on the focus- ing screen. If the focusing movement is applied to the object to be photographed, however, itwill be found that very small movements are sufficient to alter the focus enough to provide a large margin either side of " critical," due to the very small depth of field. The completed focusing stand inits fully extended position. " Lazy -Tongs " Movement the rod between the side arms and the out-protrudes the end of a ;in. Whit. coach - Accordingly,thestandillustratedwasside of the guide bars makes for smootherhead bolt inserted from underneath. A wing built to take advantage of this.The subject working.If necessary,the bearing platesnut on the bolt, when screwed down firmly, to be photographed is laid .on a light plat -or the guide bar brackets should be packedgrips the strip tightly to the base, retaining up with pieces of thinit in any position. cardboarduntilthe table is perfectly par-Operation allel with its base. To It will be seen from the illustrations that the lower sliding rodthe higher the position ofthetable, the is attached the end offurther the operating strip projects.This a slidingstripbyindicates the method of operation; slack off whichthetableis the wing nut sufficiently to allow the strip raised and lowered. Toto slide freely, and then pull it out to raise allow the rod to turnthe table.Lowering is effected by allowing while being drawnthe strip to slide gently back, which it will along,thefixturetodo automatically by the weight of the table. theslidingstripis A small knob attached to the outer end of merelyashortstripthe sliding strip will make operation easier. liketheside armsIt is desirable to adjust the fits to give com- bentroundtherodpletely free movement, as operation can then and screwed o rbe carried out with one hand if necessary. The focusing table in its loweredposition. riveted to the end of Dimensions are a matter of personal choice the sliding strip. Ifand material available, but in the one illus- formortable,whichismounted ona the loop is made from a fairly wide piecetrated the table and base are both 6in. x heavier base by means of a " lazy tongs " itwill prevent sideways movement of thekin., which has beenfoundamplybig assembly. This enables thetable to be sliding strip. enough.If a thin print larger than this is raised and lowered to adjust focus, while being copied, for instance,itisa simple remaining inallpositionshorizontal andLocking Device matter to lay a piece of stiff card on the parallel to both base and the film. The tableis locked in any position bytable first to hold the print flat.The side The movable table is a piece of 3/16in.a clamping arrangement on the sliding strip. members are 5in. long, and this length affords three-ply for lightness, while the base isa This strip bas a slot cut in it through whichan up and down movement of some 4in. piece of fin. wood the same size.The metal cross pieces of the lazy tongs movement are Side Arm din. wide strips of/t6in. duralumin, as are the guide bars along the edge of the base Guide Bars Lock Nut Guide Bar (Fig.t). This material was to hand, so was K." used, but no doubt strip brass would do N Cross equally well.The ends of the cross strips Brackets 28 are joined to their opposite numbers on the Rod other side by four 3/16in. steel rods screwed 2 B.A. at the ends, and screwed into the Washer strips with lock nuts outside.The pivot at the cross -over can be either a small nut and bolt or a river, with a washer between the Bracket arms.The upper and lower rods at one end are free to turn in bearings, each consisting Soldered of a short length of tube soldered to a small plate.The two pairs of Plates are screwed to one end of the table and to the base, while the rods at the other end are free to slide between guide bars.The bars are iin. wide Lock 0 strips of the same material as the crossed Nut se Plate arms, riveted by/thin. rivets to small angle 141Aital4144.111 brackets and spaced apart just sufficiently to 0 allow the Pods to slide freely between them with the minimum of play.A washer on r.-Details of guide bars and bearings for cross rod. 93 December, 1947 NEWNES PRACTICAL MECHANICS For Floor or Table asmallhookcanbe The device was designed for use on the screwed in one end of the floor or table with the tripod standing over base so that the table can it and the camera aimed straight down. The be hung on the wall and procedure in this case is to place everything thecameraandlights in position, raise the table about 2in. and placed on a small table in then focus as near as possible to the size front of it. In this case of image required by rough adjustments of the object to be photo- the tripod.The final focusing is then done graphed will have to be by raising or lowering the table slightly as Cross Rod pinned to the table.If required.If a small object such as a coin is 4i"Coach head bolt this is done frequently, it being photographed by extreme angle light- wouldbeworthwhile Cross gluingalayerofthin ing to show uo the relief of the design, take Sliding Strip care that any adjustment of the focus by Rod cork (such as is used for movement of the table does not disturb the table mats) on the top of lighting. the table to make it easy toinsertand withdraw Photographing Objects in Vertical Plane pins. Knob Ifitisdesired to photograph an object Fig. 2.-Plan and side view in a vertical plane, dispensing with a tripod, of the sliding strip.

other kinds of light each different from its neighbour.There is the cathode ray which makes some ofthe platinum compounds Observations fluoresce, a property very useful to makers of television screens.X-rays are also light, ByProf,A. M. LOWbut have quite different properties, and are Interesting Fads About Everyday Topics. capableofpenetrating opaque substances owing to their very short wavelength with Instability evaporations and condensations inacon-which the particles of normally solid matter ARADIO valve is full up with an electrictinuous cycle. are liable to interfere.If you had eyes which charge which " falls over " like water Some liquid,suchassulphurdioxide,were sensitive to X-rays you would be able from a bucket and enables current to be re-under pressure, is caused to evaporate, andto see through walls, if you had eyes like a versed or amplified. A street regulating stop orin doing so cold is produced. The gas is thenmicroscope you would see the air full of living " go lamp " works on the principle that eachcondensed again by pressure, when it becomescreatures, and ifit did not happen that the vehicle charges a condenser as it passes overliquid ready once more to go through its cool-sun's rays were composed mainly of these thestripuntil the chargeissufficient toing evaporation and the further cooling re-spectrum colours, you would never have taken operate a relay, thus working the lights. generationof thecontentsof the wholewhite to be plain and not coloured. If the machine. sun's rays had been green your relative eye Itislucky thatstabilityis almost non- If carbon dioxide is used in liquid formsensibility would have been different, for you existent.Nothing is permanent ;even our are a creature of evolution in nature's plan. finest buildings will be mud and dust in dueand allowed to evaporate quickly into gas, the coolingisso quick that solid particles ofYou would have looked at a pair of bright course.Everything changes ;it is the prin- red pants and remarked, " what a pity they ciple of life which you see in the forms whichcarbon dioxide " snow " are formed. You will realise that whether the evaporation is causedare not coloured."While white would no renew your own body. A drop of water in aby a sudden lowering of the pressure or bydoubt have seemed most glaring and out of rainstorm cannot exceed a certain size without place. Heat is merely a slightly different breaking up, and this is lucky for you. Tinythe application of heat to the liquid does not make much difference. form of light with a longer wavelength. It drops have pressures of 2o1b. per square inch can be focused, as in the normal electric fire, and more inside their controlled surface, but The working fluid,for thatisallitis,and its rays can be bent like those of light ata certain diameter they fall to pieces becausemerely servesas a method of transferringby using the proper material.In the early the localised grip has been exceeded by theheat ; whether youusecarbondioxide,days of infra -red photography when it was total strain.It would be very unpleasantsulphur dioxide or ammonia solutionisa first discovered that photographs could be to be hit on the head by a drop of water thematter for design and economics. taken through cloudthefirstexperiments size of a large bucket, even if it was round ! In the same way, as I think I once ex-were made with lenses constructed of rock The water assumes a globular form becauseplained, water is used in a boiler to be turnedsalt because this substance did not cut out itbalan'ces out the internal force and thisinto steam and the steam merely acts as athe heat ray. There is no real difficulty in is a condition which we see relatively repro-vehicle for heat in order that, in its anxietytaking a photograph inside a dark room by duced in the atom bomb where certain isotopesto expand,it may produce power.Otherthe light of a kettle of hot water. suchasthatof uranium become mildlyliquids are equally effective.Airis rather At the other end of the stick we have unstable.Their solar system has its Milkydifficult to heat, but mercury makes a splendidultra -violet light which is invisible, and which Way clear, and bombardment is allowed tocarrier and is only inclined to failure by its cost, does not pass through lenses containing lead. reach the inner nucleus. and some danger to those who may use itThat is why special glass has to be employed From this you will guess that above a certainwithout precautions. if the fullbenefit of the sun's raysisto size a bomb might be too easy to set off, When you see vacuum pumps at work in acome into your house. In this world we and below the size of a kilogram or so thesteam engine you will know that the engineersknow very little about light, but we do know bomb becomes so stable that nothing muchwant to condense the steam as soon asitthat it is a somewhat material thing, and I leaves the engine, not only so that the water k that when atomic power has been can be done with it. can be used again for warming the boiler,further investigated, and we have found how but so that the waste steam can get away fromto change matter into energy quite easily, Hot One Minute-Cold the Next the engine quickly without having to be pushedweshallbe abletowrite knowledgeably IAM told that ancient mariners lick theirout. In the old days they used to squirt waterabout the weight of light. Far light has finger, hold it up in the air and say,into the engine cylinder, but they soon foundweight and actually hits us all the time.It "Nor', nor' by east, abaft the binnacle," orthat ifthecylinderwascooledinthishas been calculated that if a cent was raised words to that effect.In short, they feel whichway, the entering steam from the boilerto the temperature of the inside of the sun side of the finger grows cold and know thatwasted its energy by merely warming thethe actual weight of light proceeding from itis facing the point from which the windmetal of the engine. itwould knock down everyone withina comes. radius of over 5 miles. Thisistheprincipleof nearlyeveryYou Can See By It refrigerator.Even savages used to put their WHEN writing about light I think I did water, or " twala twala," as the boys' books not make it clear that what you and NEWNES ENGINEER'S Used to call native beer, in a porous vessel.I call light is only one form of an ethereal As the water, better still the beer, evaporated,oscillation. It mildly resembles wireless waves POCKET BOOK the liquid gave up its heat, and the resultingexcept that its frequencyisvastly higher. By F. J. CA NM cold provided the necessary refreshinent. Orey light from the sky is a combination of To this day it always pleased me to seeall the spectrum colours, and if you paint a 10/6 or by post 11/ - someone light a gas -jet under a refrigeratorwhite disc about 3in. diameter with segments Obtainable frombooksellers,orbypostfrom burner and to know that heat is producingof each of these rainbow colours and then George Newnes, Ltd., (Book Dept.), Tower House. cold.Cold is merely the abSence of heat,spin like a top you will soon find that the Southadipton Street, Strand, London, W.C.2. and these machines work by aseries ofcolours blend into white. There are many NEWNES PRACTICAL MECHANICS December, 1947. Memoirs of the Metals -4 The ReOrz of Radium Its Peculiar Properties and Characteristics RADIUM, now and again, has been By J.F. STIRLING, M.Sc. discovery of radium gave a sharp shock to dubbed by various writers a veritable thescientificworldwhichatthattime " prince " of metals. The simile, how- thought it knew everything about atoms and ever, is to say the least, a strained one. True their adventures, but realised afterwards that it is that radium constitutes one of the most it had really very little exact knowledge con- amazing substances which men ofscience cerning them. have ever hit upon.It has given us the long -sought key. with which, for weal or for Becquerel Began It woe, the secrets of the atom and the stupen- It all came about in 1896, when a French dous forces which exist within it are, one by chemical worker, Antoine Henry Becquerel, one, being laid bare. was studying the brilliant fluorescence which Such is the significance of radium at the is shown by solutions of uranium salts, such present day.In this direction the element asuranium sulphateor uraniumnitrate. certainly domineers over the commoner ele- Becquerel,quiteby chance, happenedto ments and enjoysascientificreign over place a tube of uranium salt on a box of them. photographic plates in a dark cupboard, and But, as a mere metal, radium is one of the on using the plates to photograph some other weakest and the least important of the world's object he found, on developing, them, that metals.Were it as common as cast-iron the they were all spoiled, having apparently been engineering industries would have very little fogged by exposure to some source of light. use forit,justas they find but sparing That is how radium made its preliminary employment for metallic barium, calcium and bow to the world of science just fifty-one strontium, its closest partners in the family years ago. of metals.You might, perhaps, be able to At that time the scientific world had been devise one or two useful amalgams with set rocking by Rontgen's epoch-making dis- radium and mercury, or, alternatively, one covery of what, for want of a better name, he might possibly be able to include metallic called his " X " rays.Scientists wereall radium as a constituent of certain soft bear- going mad on these " X " rays, and Bec- ing metalsin much the same manner in querel'sseemingly insignificantobservation which a soft alloy of calcium, sodium and Madame .Curie, radium's discoverer, and theabout uranium salts being able to affect a lead used to constitute the Bahn-metall of the first person to isolate radium metal. photographic platein the dark was given German railways. scant attention. As a structural metal, however, radium,gradually disappearing. It is slowly but quite But there was one individual who became even ifit were shorn of allits dangeroussurely fading away like the proverbial oldparticularlyinterestedinBecquerel'sdis- properties, would be useless.It would besoldier.And nothing can be done about it,covery.This was a girl, Marie Sklodowska too soft, too reactive, too plastic for any suchunless, perchance, some future atomic scien-by name, the clever daughter ofa Polish ordinary use. You might as well try to buildtist is able to hit on a method of building upscience master in Warsaw.She had gone a bridge out of sodium or potassium as toa sort of synthetic radium from fragments ofto study science in Paris, where she came into constructitout of radium metal. Forother elements. That, however, is a problemcontact with Henri Becquerel, and also with sodium and potassium are almost as soft aswith which we cannot deal here. another science lecturer named Pierre Curie,. cheese, and can be cut readily with a blunt Radium is an element knife. What ismore, they absorb atmo-which has now had nearly spheric oxygen greedily, and rapidly becomehalf a century of scienti- converted into crumbly, white oxide. Radium,fic publicity. More has too, has similar properties, but, as one mightbeen written and talked expect with such a curious metal, it differs aboutradiumandits from the rest of these soft metals in that itproperties from a spectac- prefers nitrogento oxygen, sothat whenular standpoint than has exposed to the atmosphere at ordinary tem-been uttered about most peratures it combines not with the oxygen ofothermetals.This is the air, but with the nitrogen, rapidly turn- becausethe accidental ing intoitsnitride, a white powder not dissimilar in appear- anceandphysical properties to the sodiumandpotas- sium oxides. Radium in Rocks Pieces of pitchblende-radium's chief ore. But, of course, radiumwillnever who himself was beginning to be attracted to become common, Becquerel's work. even in spite of the factthat very deli- TheyearbeforeBecquerel'sdiscovery cate physical Marie Sklodowska had married Pierre Curie. methods have proved The two were very poor.Sometimes, they it to exist in minute were almost on the verge of starvation, so tracesinthe most little in demand were science lecturers at that abundantotrocks time.But Pierre swept the floor of their and minerals. It is little apartment and helped with the washing- tco unstable a sub- up, and Marie did the shopping and cooked stance for that. It the meals, and they appear to have been is a metallic element very happy, because they both found some which is here to -day time for original investigations inscience, and gone to -morrow, particularly Marie, who, on being told by if we can use those Becquerel about his discovery, began in her phrases to signify a spare time to test out all sorts of mineral matter of a few thou- The commercial handling of radium salts.Here, the hands of the substances for " rays." sand years each.So operator are heavily swathed in protetive gloves, whilst his arms are In this way, she soon found out that this that the world's thrust through apertures in a thick lead screen.The operator ray -producing property (" radioactivity," we stockof radiumis remains behind the screen and looks through a thick sheet of plate glass. now term it) of uranium was independent of DeCember, 1947 NEWNES PRACTICAL MECHANICS 95 the exact kind of uranium salt, but was pro-delved deeper and deeper into radium andfreak and curiosity of chemical science.Of portional to the concentration of the elementinto its many mysteries. enormous cost,it would, even ifit could existing in the -salt.Hence, inferred Madame Four years after the tragedy this renownedbe protected at the back from atmospheric Curie, this mysterious radiation is concernedwoman first isolated radium metal.She elec-action by a thick layer of varnish, be of with the atoms .of the element themselves,trolysed radium chloridesolution, using alittle use, for the radium rays would quickly and is not a result of certain chemical com-mercury cathode.The radium which wasdiscolour the glass and, in time, render it binations of those atoms. liberated by electrolysis at the cathode dis-almost opaque. In 5898, Madame Curie discovered thatsolved in the mercury, forming a radium Radium compounds all discolour glass and thorium salts were ray -producing in muchamalgam. This was carefully dried andsilica, turning such materials a deep purple - the same way as uranium salts.She found,cautiously heated in an iron boat (for mer-violet, not unlike the colour of iodine vapour. also, that these ray -producing compounds hadcury does not attack iron) contained in aThe " radium stain " on glass can be to theproperty of being abletoionise theglass tube through which a current of verysome extentdecolourised by heating the surrounding air and to render it electrically glass, but some of it, at least, is indelible. conducting. Held in a non -luminous flame, a fragment The next step, and perhaps the most im- of radium metal (or of its salts) colours the portant one of all, was taken by Madame flame astriking carmine -red,injust the Curie when she noticed that certain grades same way as sodium colours the flame yellow of pitchblende (the mineral ore of uranium) and barium renders it green. seemed to have more radiation activity than could be accounted for by their estimated Decomposes Water uranium content.This, inferred Madame Metallicradiumvigorously decomposes Curie, could only be due tothere being water, just as do the 'metals potassium and present in these pitchblendes traces of an sodium.Hydrogen gas is evolved from the unknown element which was much more liquid, the radium metal disappears and the active than uranium itself. radium hydroxide, a milky alkaline substance, which is formed enters into solution. Radium Revealed To what extent metallic radium will alloy Through the good offices of their friends with other metals is more or less unknown. and the generosity of the Austrian Govern- The cost of such experiments has been too ment, the Curies obtained a free gift of a greatto allow ofsuch knowledge being ton of pitchblende from the famous " Dollar gained.Who knows, however, what future Mine "at Joachimstal,a mining town in some asyet unknown radium alloy may Bohemia.Together the Curies dissolved up eventually possess ? the whole of the crushed ore, chemically con- The metal which bears the closest resem- centrated it, precipitated it, and in this way blance to radium is barium, a member of they obtained two chemical substances which the " alkaline earth " metals.Indeed, radium were each strongly radioactive.One of theseA lead bottle for the storage of radium and itsbelongs properly to this family group of substances was prpcipitated with bismuth, and salts. metals, and its chemical properties fitit in to the element which it contained Madame accurately with this group.What properties Curie gave the name of ." Polonium," inpure hydrogen was passed under a reducedbarium has, the same also will be shown honour of her native Poland.For the other more or less in the case of radium. pressure.. substance which had been precipitated with The radium amalgam, which at ordinary barium compound, and which showed thetemperatures had beenplasticandsemi- greater amount ofray -producingactivity,liquid, became solid as soon as a temperature Madame Curie happily conceived the nameof 400 deg. C. had been reached, most of the of " Radium," a title which she little thoughtmercury volatilising away.At 700 deg. C. was eventually to become world-famous. no more traces of mercury remained, and the bright globule of metal which lay in the diminutive iron boat itself suddenly liquefied. Madame Curie, for the first time in the world's history, had prepared radium metal and had melted it. Metallic radium has been made by other workers at later dates, but, naturally enough, owing tothe extreme scarcity of radium compounds, only very small amounts of the metal have been produced. A White Metal Radium is a brilliant white metal, almost, indeed,as white assilver, whichisthe whitest of all metals.It melts sharply just above 700 deg. C., and at this temperature itvolatilisesappreciably. In contact with air, radium metal rapidly tarnishes and, in fact, corrodes.But, as we have already seen, the product of thisactionisnot radium oxide, but the nitride of the metal. A few A carrying -tub -2for smallquantitiesof other metals, such as titanium, calcium, mag- radium compounds.Itis made out of a nesium and lithium, will form nitrides, or thick-walledleadwater pipe. Containers combinations with nitrogen, when 'heated in of tungsten -copper -nickel alloy have anatmosphereofthatgas,but radium recently beenintroducedforthesame appears to be the only metal which, when purpose. They have similar ray -screening given a free choice, will at ordinary tempera- - powers, and are muchlighterthan lead tures combine with nitrogen in preference . containers. to the more active oxygen. An interesting feature of radium is that For a long time, radium was only knownitisoneofthe' mirror -formingmetals. Two electroscopes standing side by side.Both in the form of its salts.Pierre Curie him-Silver, gold, copper and a few other metalshave been givenidenticalelectricalcharges. self never saw metallic radium for, one even- can all be deposited as brilliant mirrors onThe electroscope on the right retains its charge, ing in 1906, he went out to visit some friendsglass orsilica by various chemical means.the gold leaves remaining apart.The electro- and to have dinner with them.It was ,anBy heating radium azoimide,. whichisascope on the left, however, contains a bottle evening's relaxation from which he neverspecial organic nitrogen compound of thehaving a fragment of radium barium bromide returned home.He met sudden death onelement, in a high vacuum at a temperaturein it.The ray -m from this ionise the air within the streets of Paris by being run over. of between 185 and 200 deg. C., the radiumthe electroscope, rendering it electrically con= After the initial effects of the tragedy hadmetal is liberated and is deposited on theductable. The gold leaves thus fail to hold worn off, Madame Curie found a degree ofglass of the vessel as a brilliant mirror. theircharge,andtheythereforecollapse forgetfulness in her beloved science. She A radium mirrorisnecessarilya mere together. 96 NEWNES PRACTICAL MECHANICS December, 1947

Metallic radium (and all its chemical salts) the explosion and disintegration of isself -luminous.It glows brilliantly in the 37,000,000,000 of its atoms every second, a dark, manifesting an intense bluish lumines- given mass of radium only loses about 0.04 cence. Likewise,owingtotheinternal per cent. of its content per annum. activityofitsatomsitisalwaysafew degrees higher in temperature than its sur- Rots the Flesh roundingobjects. Were radiumandits Radium, of course,isone of the most compounds common, and were they without dangerous metals known toscience. Its any semblance of danger, they would func- intenseradiationwillrot away theflesh tionadmirablyas perpetualsources of of any livingbeing. Itwill break down personal warmth for stitching into clothing complexmolecules of organicmatter, on cold days. destroying the life -function with which such Of the vital radio -activities of radium metal molecules may be concerned.That is why it is hardly within the province of this article radium will, when uncontrolled, far oftener totreat. Radium,aswe know,isan cause cancers and other malignant tumours unstable metal.Some of its atoms persist than it will cure them. in exploding spontaneously and, in so doing, Radium's chief minerals are pitchblende they give out energy in the form of " rays." and carnotite, which occur in various parts Becauseofitsself-destructiveproperties, of the world.The largest British Empire radium is slowly decaying.One-half of any deposits of pitchblende are in the Great Bear given mass of radium will decay in 1,58o Lake region of North-western Canada. This years, this period being known as the " half ore, which is mainly an oxide of uranium, life " of the element.After 4,740 years the carries quantities of silver and copper.It original amount ofthe element will have is concentrated locally and sent by aeroplane reduced itself to one -eighth. to a refinery at Port Hope, Ontario, where The chief emanation or " ray " given off radium bromide and sulphate are extracted by radium is the alpha -particle.So intenseA tube containing radium bromide.It is self-from it, along with uranium and silver. is the internal energy of a mass of radium luminous. In 1938-the last year for which figures that itis able to shoot off its alpha -particles areavailable-Port Hope produced about with an average velocity of 9,38o miles perplaced at a given distance from an accurately70,000 milligrams of radium material, whilst second. weighted fragment of radium. in the previous year its production was only In one second one gramme of pure radium From this consideration alone we are able23,770 mg. wouldemitapproximately37,000,000,000togainsomedimappreciationofthe With .the enormous demands now being alpha particles.This stupendous number isenormous number of individual atoms whichmade on uranium ore foruseinatomic no mere fancy,forithasbeenactuallymust be containedinasinglegramofpower stations, the production of radium will determined by counting the flash -impacts ofradium or of any other metal, and thisis be stepped up so that, relatively speaking, alpha -particles on the zinc sulphide screenespecially so when we learnthat,despiteradium will become commoner.

which is gradually raised to about 1,000 deg. When they are up to temperature, they are EthylSilicateinEngineering removed and immediately clamped to a tilt- ting electric furnace containing the molten A New Organic Compound of Silicon By A. E. WILLIAMS, F.C.S.metal, which isforced in by air pressure. The mould and casting are allowed to cool WHILE theinorganic compounds of fabricateby conventional methods. Itis slowly and the refractory materialisthen silicon-so well known in the formimportant that the moulds prepared for thisbroken away from the casting, which has of innumerable minerals-have beenprocess should resist high temperatures andonly to be trimmed or shot blasted where with us from time immemorial, itis onlyshouldnot become crackedordistorted.necessary. The accuracy depends on the very that recently organic compounds ofHydrolysed ethylsilicateactsasa bondtypeofcasting,butitisusually about silicon have been evolved and developed forwhich does not slag or burn out at higho.003in. use in industry.The fact that organic com-temperatures. pounds have been produced is something of an achievement in the chemical sphere, forPrecision Casting Hydrolysed Ethyl Silicate silicon, better known as its oxide, silica or A master pattern, accurately made from Ethyl silicateitself,as manufactured by sand,isaveryinert,refractorymaterialwood or metal, is used to make soft metalAlbright and Wilson, Ltd., isa mixture of which does not readily combine with any-moulds from which wax patterns can be castethyl silicates of different degrees of conden- thing, much less the mild organic materials.by injection of molten wax under pressure.sation, and it has an actual silica content of So that the production of an organic com-The soft metal moulds are sometimes lubri-about 4o per cent.it is a colourless mobile pound ofsiliconisregarded asadefinitecated with the unhydrolysed ethylsilicate,liquid ofspecific gravity Lon at 20 deg. innovation In the chemical field. which use represents one small outlet forC., and has an initial boiling point of about the unhydrolysed material. 170 deg. C. at ordinary pressures.Its flash " Lost Wax " Moulding Process When solid, the wax pattern is removedpoint is approximately 53 deg. C., and itis The chief of these new organic compoundsfrom the mould, trimmed, sprayed with ainsoluble in water, but is soluble in alcohol of siliconisethyl silicate, and as such itslurry consisting generally of sodium silicateand other organic solvents.The most im- finds little commercial application up to theand powdered silica, and then allowed to dry.portant chemical property of ethyl silicate is present time, but itshydrolysed solution isIn this way the wax pattern is coated withits ability, to undergo hydrolysis to give silica being used in a variety of ways.Its mostwhat amounts to a facing sand. The sprayedor highly condensed ethyl silicates. This important application at present being in thepattern is next fixed in position in a mouldinghydrolysis is usually carried out by the addi- " lost wax " investment moulding process forbox and the " investment mixture " pouredtion of a very small amount of acid, dilute the production of precision castings.Preci-around it.This mixture consists of a slurryhydrochloric acid being the most suitable, to sion casting was originally developed for theof powdered ceramics, such as silica floura mixture of ethyl silicate, industrial alcohol fabrication of dentures and jewellery, butand powdered grog, containing a little mag-and water.Hydrolysed solutions of ethyl it has now been extended to all fields wherenesium oxide, in a hydrolysed solution ofsilicate, suitable for use in precision casting, intricate castings from special high -meltingethyl silicate.The magnesium oxide (magne-may be prepared by a variety of methods, point and corrosion -resistant alloys are re-sia) is the alkali which accelerates the settingbut the following suggested example gives a quired.As, for example, in the manufacture ofthe mixture, anditsamount must bemixture which is initially homogeneous and ofturbo -superchargerbucketsforaerocarefully regulated. The moulding boxes areconsequently does not require shaking or engines, parts for jet and gas turbine engines,vibrated so that the refractory materialis stirring: chemical and textile equipment, diesel enginecompactedroundthewaxpatternand Soo cubic centimetres ethyl silicate and pulverising machinery components,allowed to set.The setting time can be con- 5,500 cubic centimetres industrial alcohol pump impellers, rock drills and cutting tools.trolled by variation of the amount of magne- 5o cubic centimetres water The " lost wax " processisused to makesium oxide in the mix.After the preliminary to cubic centimetres hydrochloric acid extremely accurate castings of parts too intri-set has taken place, the moulds are put into (5 per cent. strength). cateto machine or forge economically, oran oven to melt out the wax and harden The above materials are mixed thoroughly those made from high -melting alloys, such asthe refractory mixture. The moulds are thenand then allowed to stand approximately 12 special nickel alloys which are too tough toput through a furnace, the temperature ofhours before use. December, 1947 NEWNES PRACTICAL MECHANICS 97 Electrics for BeAinners 2.-A Small Shocking Coil THE beginner will find the construction in the edges for the connecting wires to pass of this small shocking coila fairly By " HANDYMAN" through and glue the wooden cheeks in place. simple job, and when completed it will (Continued from page; at, October issue.) One end of the iron core should project provide instruction and entertainment.The past the face of one cheek asshown in coil described can be made quite cheaply,unwinding, and, after applying a coating ofFigs. r and 2.Fix the coil in position on the and will work efficiently when connected upshellac varnish, cover the coil with a piecebaseboard by two screws driven into each to a 4 -volt accumulator ortwo large dryof thin brown paper. When quite dry windcheek from underneath. cells. on the secondary coil,leaving about6in. At this stage four small wooden knobs, to Principle of Working free at each end for connecting -up purposes.serve as feet, can be fixed to the baseboard BeforedealingwiththeconstructionalBind the last two or three turns with thread,near the corners. The stems of the knobs can details it may be as well to briefly explain the principle on which a shocking coil works. A shocking coil is an induction coil of simple form, and depends foritsaction on the peculiar property of electricity by virtue of which, when one coil of insulated wire through which an intermittent current of electricity is caused to flow is placed within another coil, a current of electricity is induced in the other coil.The inner coil in this case is known as the primary coil, and the outer one thesecondarycoil.To ensurethatthe electromotiveforce,orpressure,ofthe induced current shall be sufficiently high to cause a shock, the primary coil is wound round a laminated iron core, while the secondary coil of finer wire consists of a much larger number of turns than the primary winding. By means of a rapid make -and -break device the necessary intermittent current is caused to flow in the primary coil. It is on the rapidity Fig I. -Plan of the completed coil, with hand grips. ofthemake -and -breakactionthatthegive another coating of shellac varnish andbegluedintoholes made in thebase- strength of the shock depends. put on one side to dry. board. Constructional Details For the baseboard, A (Figs. r and 2), cut aMounting Coils Contact Breaker piece of Bin. planed wood 6in. long and 31in. To enclose the coils a thin cardboard tube diameter,isused, Thisconsistsofanarmaturespring, wide. Ordinary deal will answer the purpose, 3,1in.long andiiin. supporting pillar, contact screw and bracket. andthiscanafterwardsbestained andcovered by a piece of velvet or other material.The armature spring can be made from a polished. Place the coils in the tube, make small nickspiece of thin, springy brass, about No. 35 gauge, cut to the dimensions given at D.

111 (Fig. 4). The armature, E, is a soft iron disc Bin. dithneter and *in. thick, ahole being drilled through the centre so that it can either be screwed or riveted to the end of the spring. 0 The contact piece, F, is of silver, and for this part of a link from an old watch chain can be used.Straighten out the link, cut off a 6" or. piece about *in. long, and insert it in the hole, G, and burr it over on both sides of the Fig 2.-Side and end views of the coil. spring by tapping it with a light hammer till a flatdisc of silveris formed about tin. diameter as shown in Fig. 4. Two pieces of planed wood, I Bin. square and For the supporting pillar a piece of brass 5/16in. thick, will also be required for the rod gin. diameter andin. long will be end cheeks, B (Fig. 3), which support the core required, and this has a hole drilled and and windings. With a 5/16in. centre -bit bore a tapped in one end to take a countersunk hole in the middle of each cheek for the screw, as shown at H. At the top end a flat ends of the core to pass through.Chisel is filed to take the end of the armature spring, off the top corners as indicated, and smooth which can be neatly soldered to the pillar as the sides and edges of the cheeks and base- 02,--P1 shown in Figs. r and 2. board with fine glasspaper. The core consists The bracket, J, for the contact screw is of a bundle of soft iron wires, 4 Pn. long, and bent to shape from a piece of sheet brass lin-in. this is covered with a layer of thin brown thick, after drilling the two holes near one end paper, the edges overlapping +in. and stuck Layer°afte.r. C for the fixing screw and terminal stem and down with a smear of gum.The paper Brown, drilling and tapping the hole at the other covering should be 3' -gin. long, so as to allow end for the contact screw.For the latter, in. of the core to be bare at each end, as C obtain a brass screw, preferably with a milled indicated at C, C (Fig. 3). 10)11))))1010100»001100 head, and in the end drill a small hole and Coil Winding Slartinv solder in a short piece of silver wire from the For the primary winding 5yds. of No. 22 -(-_Enct watch -chain link, leaving about lig in. project- cotton -covered copper wire will be required, ing as shown in Fig. 4. Fix the bracket to the and for the secondary winding 26yds. of No. 28 baseboard, in the position shown in Fig.t, with a small round -headed brass screw and a cotton -covered will be necessary. Carefully !riilLIII(11111111111111111111111111111111 wind the primary wire on the paper -covered terminal. Make sure that the end of the silver core, leaving a free end of about 6in. to start wire on the contact screw touches the centre with, the same amount being leftat the Emig/iv of the silver disc on the armature spring when finishing end. 'End the latter is in its normal position.Another Bind the last two or three turns tightly withFig.3.-Details of coil cheeks, ironcore andterminal can be screwed into the baseboarc; strongthreadtopreventthecoilfrom primary winding. near one corner as in Fig. 1. 93 NEWNES PRACTICAL MECHANICS December, 1947

winding, are clamped underwhen a slightshockwillimmediately 2" two terminals which alsobe felt. 0-G 1;4' take the ends of the flexible For the hand -grips, obtain two pieces of +-- q11 X- leads attached tothethin brass tubing about din. diameter and din. 1/4-)1 hand -grips. long.A piece of twin -flex wire, 2ft. long, The coils can now beserves for the connecting leads.The wire wow@ tested by connecting up tois opened out at each end, two of the ends 511 a single dry cell, the leadsbeing soldered to the grips inside one end. from thelatter beingThe strands of wire at each of the other ends, H connected tothe twoafter being twisted together, can be dipped in 00 terminalsatthe ends ofsome flux and soldered, so forming solid ends theprimarywindingas for clamping under the terminal screws. F shown in the circuit Primary Winding Fig. 4.-Armature spring, supporting pillar, contact screw and bracket.diagram, Fig.5. On adjustingthe Connections contactscrew so that Before making the connections it will bethesilverpointpresses as well to form the free ends of the windingslightlyagainstthecon- intospiralsasindicated. Thisiseasilytact disc on the armatureTo done by winding the wire round a smoothspringthelattershould_Battery wooden or metal rod about kin. diameter.vibrateat arapidrate, Secondary Iron, A more " business -like " appearance is thusand continue to do so as Winding Core given to the coil. longasthecurrentis With the aid of a penknife, bare each endflowing. This indicates of the covered wire and fix one end of thethat the primary winding Artncdure thicker wire under theterminal near theis all right. Now place the corner of the baseboard.Clamp the othertip of a finger of each hand String Terminals end of thethicker wire under the brasslightly on the two term- for HandGriffis pillar which supports the armature spring.inals,attached to the The ends of the finer wire,or secondarysecondary winding, Fig. 5.-Circuit diagram.

FinishingMetalSurfaces --CelluloseandSynthetic Methods of Applying Cellulose and Syhihetic Enamels

THERE are two methods of finishing ByJ.H. OUSBEY turps. and leavefor an hour or two,if metalsurfaceswithouttheuseof successful re -spray to cover the marks left elaborate plant.These methods areprimer to avoid the surface acquiring moreby the turps., if not it will be necessary to (t)cellulosingand(2)enamellingwithgrease frombeing handledorrust fromstrip the affected part and start again. synthetic enamels. exposure. Blooming is a common fault with cellulose Celluloseis normally applied by spray,Spray Equipment and usually occurs through spraying in a whilst synthetics can be brushed or sprayed. The spray plant will vary, according todamp place with no heat. The remedy is to amount of work being tackled, from a veryget some heat on and re -spray, first with Preparation small t cylinder model with a fractional h.p.thinners alone, then carrying on with the 1. Metals are prepared in the same mannermotor to a large garage sized compressor withcolour. for both kinds of finish, and the aim isa 6o to So gallon tank and a large powerfulPolishing scrupulouscleanlinessand freedomfrommotor with self-starting and stopping device. If a matt cellulose lacquer has been used grease. Whatever_ the model or make, however,and it is desired -to polish it, use the abrasive 2. Where metal surfaces have been welded,efficient spraying cannot be hoped for unlesscompound supplied by the makers of cellulose soldered or brazed, there isa danger thatthe plant can reach and maintain at leastlacquers and apply with soft cloths so as not to some of the various fluxes used will lurk in5o lbs. per square inch ; working pressuresscratch the finish in any way. cracks and defects, and later, either hindervary from 5o to 70 lbs.per square inch A wax polish will give added lustre and the paint from drying or cause it to blister ifaccording to the type and consistency of theprotection to the finished surface. it does dry. cellulose or paint being sprayed. _. 3. To help combat these fluxes, it will be Guns.-The best guns are the suction orSynthetic Enamels advisable to wash the metal well with paraffinpressure feed type.There are too many The virtue of synthetics is that whilst they orpetrol,scratchingthesurfacewithdisadvantages with the gravity fed type witharc not quite as hard as cellulose in as short either a wire brush or coarse emery cloth tothe cup on top, the chief disadvantage is thata time, they have better drying qualities than clean any rough places.If paraffin is usedthe gun must be held upright. ordinary enamels, and areless trouble to finish off with turpentine substitute and wipe When spraying, keep the vent hole on top apply. dry and clean. of the container free from cellulose or paint. Prepareasdescribedforcellulose, and 4. All very smoothly finished metals such The gun is held at a distance of 6 to gin.prime with the primer supplied by the makers ; as aluminium need the surface made roughfrom the work and a little experience willor a red lead primer with no gloss is per- with emery cloth so as to provide a " key "show the correct distance for each part ofmissible. One of the most successful ways of for the paint, otherwise flaking and chippinga job. applying synthetic enamels is that of spraying will occur later on. the undercoats and brushing the finishing 5. Galvanised iron does not readily takeSpraying coats. cellulose or paint and has a marked tendency The first coat is the primer, which is made The undercoating goes right on top of the to cause any coating to flake off, due mainlyto adhere to bare metal and may have a redpriming, and alittlesandpapering will be to saponification of the paint film. lead base.Allow 1 of an hour to dry beforenecessary after this coat is dry Before putting 6. A " mordant " is required to etch theapplying the next coat, which isafiller. on the final coat of finishing enamel. surface sufficiently to take the finishitis The condition of the metal decides how If more than one coat of finishing enamel is proposed toapply. Formula for such amany coats of filler, from one for pressedproposed, the first should be well brushed out mordant is as follows : steel to three or four for castings is the rule,so as to dry hard for the final coat. To make approximately t gallon of Mordant.65 per cent. filler, 35 per cent. thinners being Synthetic varnishes are obtainable but are Industrial spirit 5 pints the usual consistency. not advised on such colours as creams, greys, Lightly rub down with waterproof abrasive Toluol 2,, and spray on the colour until solid, allowingetc., as even the palest varnish turns these Spirits of salts .1 ,., not less than 20 minutes between coats. colours yellow in time. Carbon tetrachloride )1 When sprayingsyntheticenamelsthey 7. After applying this solution and allowingSnags to Avoid should be thinned with the thinners provided, to remain on the surface for about to minutes, Runs.-If a run occurs and the article isor with the best sub. turps. available.to per wash off with warm water and dry well.too large to permit of wiping all the cellulosecent. of thinners is the limit, beyond which After the preparation stage, the method hasoff and re -spraying, allow to.dry and rub downthe obliterating power of the paint is reduced to be decided, cellulose or Synthetic, the twowith abrasive paper and then re -spray theconsiderably. cannot be mixed. portion affected. After completion of any article in synthetic 8. As soon as the cleaning is complete the Patches not Dry.-If some partsremainit is advisable to leave untouched for about work should be put into the first coat oftacky the remedy isto dab on some sub.24 hours. December, 1947 NEWNES PRACTICAL MECHANICS 99 THE WORLD OF MODELS Model Work at Exhibitions Architectural Modelling in Sweden By "MOTILUS" AT the end of theyear we alllook collectionofs h i p towards the New Year, but at themodels ever brought same time some of us like to dwell together in this coun- for a short space on what the past twelvetry was to be seen at months have meant to us in our hobbies, and the -RoyalHorticul- to recall our own particular achievements turalHall,London. since we last looked forward to a New Year. The models displayed As thisspaceisdevoted tothe " Model weremostlyprofes- World "-and I feel readers will agree thatsionally made, either it has been a wonderful year for modellers-by specialist firms or Iwould liketo takethis opportunity toin the modelling de-

Fig. 1.-A peep at the Aircraft Section of the Model Engineer Exhibition, 5947. This section seemed to fascinate the younger generation more than the older model fans who still cling faith- fully to their old loves, train and ship models.

partments of the various shipbuilding yards. Not only ship models, but many technical devices used in modern marine engineering %I ere demonstrated here, and a series of lec- tures, covering many phases of shipbuilding and ship operation was given in the Lecture Hall. A place among the " classics " must also be given to the Marine and Engineering Exhibition heldat Olympia this autumn where some remarkably good models were to be seen on the stand of Messrs. Burmeister and Wain, of Copenhagen. The Welsh Exhi- bition was running simultaneously at Olympia,wheretherewasagainsome splendid model work, although I must con- fess that my attention was rather distracted Fig.2.-7'ne French " Crampton" locomotive that was sent to Switzerland for the Swiss from my notebook during my visit there, by Railways Centenary celebrations.This photograph was taken while the locomotive was taking the delightful Welsh puppies and the charm- water at Brugg, near Baden. ing, friendlylittle Welsh corgis.Iforgot the " Model World " for a short time while revive memories of some important events in admiring some of their sagacious tricks. our " miniature " sphere, including some that Another Exhibition which gave publicity have been mentioned in these pages since last January. Various Exhibitions The item having claim to first mention is, without doubt, the Model Engineer Exhibi- tion, the most popular " get-together" of the Model World in this country, which also attracts many of Our friends from overseas. An innovation was made this year -in the general layout of the Exhibition : The trade stands were arranged apart from the Com- petition and Loan Sections, which were in the centre of the hall.Also, in place of the familiar passenger -carrying railway there was - working models arena at the far end of the hall which provided fora display of model aircraft, power boats and racing cars. Workmanship wasofaneven-higher standard than in previous years, exhibits were more numerous and trade , stands showed signs of gradual return to pre-war produc- tion (Fig.5). The Model Railway Club Exhibition, held in the Central Hall, Westminster, in April, drew large crowds, although not so compre- hensiveashow asthe Model Engineer Exhibition. The now familiar Model railway running track isstill- a firm favourite and never lacks enthusiastic passengers. Fig. 3.-A Swedish architectural modeller at work in Stockholm.All the working ?moo. - TheShipwrightsExhibition,heldin makers I saw in Stockholm were dressed similarly in white overalls and white peaked cap. February, was an occasion when -the finest This looks very smart and I presume the peak on the cap is to shade the eyes. ti

100 NEWNES PRACTICAL MECHANICS December, 1947

structionofa ship'sinteriormechanism. brought over from France for the occasion, To emphasise the success of model -making and which is seen in tke illustration (Fig. 2). inits newest phases-those of aircraft and Standing on the engine are the French driver, cars-mention must be made of the EatonMr. Walter Brast, and the French fireman. Bray Aerodrome and Car Track where soMr. Walter Brastisoneof the" Brast much has been accomplished inthe past Brothers,"thekeen model -makers of twelve months. New records, larger crowdsLucerne, about whom Ihave writtenin and much fine work has been seen at this previous issues. Meccaofallaircraftandroadvehicle modellers. Model Making in Sweden Duringthesummer, model -makersin Anothercountrywhichcanboast a Switzerland had a gala season on the occa-fine fellowship of model -makers is Sweden, sion of the Swiss Federal Railways Centen-where I was able to pay a short visit this ary.Readers will recollect glowing accounts year.The Swedes are principally interested of this event in previous issues of PRACTICAL in architectural and ship modelling (Fig. 3). MECHANICS, and it will be remembered thatWhile over thereIvisited two museums, great interest was shown in thetravelling the Marine Museum at Stockholm and the exhibition which toured the country andmore historic one at Gothenburg.I found which contained a large number of railwaythem both well planned and displayed and models. Of these, many were made byfull of good examples of both ancient and members of well-known Swiss clubs, to illus- modern ship models and equipment. When tratetheprogress madeinSwissrail- itcomestoarchitecturalmodelling,the roading in the last hundred years. Among Swedes differ from us in their method of the full-size locomotives used in the celebra-showing contours on landscape.- Instead of tions was a French " Crampton " locomotive, making arealistic appearance as we do in

Fig. 4.-A vertical steam engine and boiler, built by Mr. Hare, secretary of the Percival Aircraft Model Engineering Society.This is Mr. Hare's first attempt at metal work. totheuseofmodelswasthatof the Institute of MarineEngineers. One ofthe most outstanding models was the sectional replica of the R.M.S. " Queen Eliza- beth." This detailed exhibit showed the engine room and machinery ofthe great " Queen of the Seas," including her boilers, turbines, electrical plant, pumps, generating plant, etc. The work of Messrs. Bassett- Lowke, Ltd., it was made to a scale of lin. Fig.5.-Model hydroplane, " Trailblazer," powered by a 2.5c.c. compression ignition to the foot, and could be distinguished as engine. The model was designed and built by Mr. A. M. Welter. one of the finest models showing the con- this country, they reproduce on the model the contours of the ordnance survey map, so that the undeveloped part of the model is covered with what lookslikeaseries.of regular,thinsteps,coveringthe various undulating areas.This tends to give the finished model a rather peculiar appearance, but the Swedish architects maintain that this isa simpler and more satisfactory way of showing contours on the land than a realistic presentation of a hilly countryside. In our own country, model clubs and societies have been increasing in quality and quantity, and whether formed in works, dis- trict or school, great strides are evident. Mr. George Archer, previously mentioned in these pages, who is now group apprentice instruc- tor for Messrs. Percival Aircraft, Ltd., has sent me some interesting photographs of the work of members of the Percival Aircraft Model Engineering Society.These photo- graphs cover a large range of subjects, but illustrated here (Fig. 4) is the first attempt of Mr. " Bunny " Hare to work in metal a verticalsteam engine andboiler. This model has been built on a total cost of 3s. for materials, and as it was constructed for the purpose of gaining experience for more ambitious metal work, it is a very creditable effort.I congratulate Mr. " Bunny " Hare Fig. 7.-A close-up view of the forward portion of a model of the new passenger ship, " Patria." and prophesy that we shall be hearing further This ship was built by MesSrs. John Brown, of Clydebank, for Cia. Colonial de Navegacao from him in the future. of Lisbon. This year Northampton had its first model December, 1947 NEWNES PRACTICAL MECHANICS 101 combining original de-highstandard,and some ofthe designs signandfinework- showed promise of great things. The Angli- manship. A uniquecan Church model made by Mr. H. C. modelhydroplane,Ward was well proportioned, and was so designed and built bysimple in itsdetail that it reminded me of Mr. A. M. Welter, aa modein Swiss church (Fig. 6). I wonder native of Switzerland,whetherMr.Wardhaseverbeento whohasmadehis Switzerland ? home in Northampton News of professional model -making for and who ischief de-the large shipbuilders also reaches me for signerat one of themy notebook. A very beautiful, detailed shoe factories. Themodel of an entirely new ship, " Patria' " has model, named "Trail-just been made by Messrs. Bassett-Lowke, blazer,"isillustratedLtd., for the builders, Messrs. John Brown inFig.5.Builtof&Co., Ltd., of Clydebank (Fig. 7).This is balsa wood, the floats a52,50o -ton passenger ship belonging to are planked and theCia. Colonial de Navegacao, Lisbon.She is bodyisalso plankedfitted with a Brown -Sulzer turbine and will inside andoutside.be used by the owners for service between The seats in the inter-Lisbon and East and West African ports. ior of the 'plane are of In the commercial world generally itis stainless steel andvery refreshing to note that materials are there is a motor in thebecoming gradually more numerous. Manu- a2.5c.c. facturers are slowly getting into their stride, Fig. 6.-An original design for an Anglican Church, by Mr.H.C. Ward,tailend, and most of the well-known model shops in of Leicester School of Building and Architecture.The design and theD y n o compressionLondon and the provinces are producing a 116in. to the foot model were both Mr. Ward's work. ignitionengine.The hydroplane is not in-better variety of goods. In most cases, exhibition, an excellent effort on the part of tended for racing, but for passenger -carryingalthough prices are higher, the standards are the Northampton Society of Model Engi-on lakes or rivers, and is well suited for theequal to those of pre-war days. neers, which met with well -deserved success. conveyance of passengers from seaplanes to From this brief and. not very comprehen- Held in the Guildhall, it presented an impres-terminals. sive review, which only mentions some of sive array of work for aSociety that has This was only one of a variety of excellentthe high spots of the year in the " Model so recently been reorganised after enforcedmodels shown, and as the attendance duringWorld," readers will be convinced, without dormancy during war years, and drew largethe three days the Exhibition was open wasdoubt, that model -making, both by amateurs crowds during its " run " of three days. and professionals, is very much alive, and its so high, the organisers have decided to makeappealis much wider thanit was before The exhibits were divided into sections forthis an annual event. the war.This, I think, is due to the great locomotives, ships, aircraft and open competi-Leice;ter Students Model Work number of people who, during the war tion, and the entries inallthese totalled VisitingLeicestertoassistinjudging period, took up the hobby as a relaxation over 4o in number, all showing a good standardsome models made by the students of thefrom the strain of the times. These new of work.There were also over 6o loanLeicester School of Building and Architec- devotees, as well as the older model -makers, exhibits contributed from Northampton andture I found the studentS there very keenare now finding thatmaterials,drawings, district.A novel feature at the Exhibitionon this work, and they designed as well ascastings and parts are more easily obtained was a cast-iron tank for the demonstrationmade their own models.The school is aand thisisencouraging them to greater of model power boats, and there was also a veryprogressivepart of the Educational working model railway. Department of the city, and every encour-will bring larger supplies of materials of all Messrs.Bassett-Lowke,Ltd.,offereda agement isgiventothe students inthis kinds,fiper models and an even keener silverchallenge bowl for thebest model hobby.Consequently the work is of a veryinterest in the hobby. and the indicators for both pilot and navi- gator give their readings of the bearing. If, for some reason, this automatic opera- New British Radio Compass tion is not required, the loop may be driven THE Royal Air Force is to have a newshaped housing placed above the fuselage,round under manual control and the opera- radiocompass,whicliisthe mosttakes onaverydifferent,compact andtor may determinethe minimumsignal - advanced instrument, of this type yetflattened form, only a few inches in depth. position aurally.Both fortuning and for produced.It was shown for the first timeFor retrospective fitting to aircraft it is nowdriving the loop, the operator has only to at the recent Radlett Display and Exhibition.housed in a shallow " blister " whose airturn a small knob.If he turns it far, opera- The fact that this new radio compass hasresistance is one third that of the old stand-tion is rapid.Ifhe slacks it back, movement already gone into production will undoubt-ard loop and may, indeed, be less still.Foris gradual, and if he turns it the other way, edly be pleasing news for past and presentincorporation in new machines, the loop is allmovementsarereversed.The whole aircrew familiar,until now, only with ansunk into the aircraft body itself, with aoperation is thus completed in a matter of American instrument.SinceiFisunder-cover moulded to the curvature of the fuse-seconds. stood that the radio compass will also belage, so that there is no projection at all. These are merely some outstanding features made available forcivil aviation purposes, more readily appreciated by the layman. For the news will, in fact, be of much wider,Operation the flying man there are other aspects of indeed of world-wide, interest. Inthe operation of this type of equipmentequal interest-the general presentation, for In essence, a radio compass is a specialisedit is necessary to rotate the loop aerial to justinstance, and, particularly, the accuracy of receiver with specialised aerials, designed sothatpositionwhere minimumsignalis the whole instrument, which is o the order that the signals received from a radio beacon,received from the beacon.With the newof one degree or less-an exceptional achieve or other station, give a direct dial readingof radio compass itis only necessary to tunement on the part of the engineers concerned the compass bearing of that station.Suchin the beacon and the rest follows automat-both with the conception and development bearings are used for navigational purposesically-the loop takes up its correct positionof this new British navigational aid. in the ordinary way, or for direct homing to the site of the beacon itself. Theradiocompass,whichhasbeen FOR ENGINEERS-----, developed to meet the specification of the B. F. J. CAMM. R.A.F. by Salford Electrical Instruments of PracticalMechanics Handbook12/6,by Wire and Wire Gauges(VestPocket the G.E.C., working inclose collaboration Book), 316, by post 319. with the Royal Aircraft Establishment, Farn- post 131-. borough, embodies most advanced electronic Screw Thread Tables, 51-, by post 513. Screw Thread Manual, 61-, by post 616. and " servo " practice, and takes the fullest Refresher Course in Mathematics, 816, by Newnes Engineer's Reference Book, 42,1 - advantageoftheknowledgewhichthe post 91-. by post 431-. hasgainedbyexperienceduring R.A.F. Gears and Gear Cutting, 61-, by post 616. Newnes Metric and Decimal Tables 3/6, recent years.Thus all remote controls are by post 3/9. electrical so that no limit is imposed upon Workshop Calculations, Tables and Published by the distance between the various units, while Formula, 6/-, by post 616. GEORGE NEWNES,LTD., TOWER HOUSE, theelimination 61 mechanicalbacklash reduces possible error. Engineer's Manual, 1016, by postIII-. SOUTHAMPTON STREET, STRAND, W.C.2 The loop aerial, so familiar in its torpedo - 102 NEWNES PRACTICAL MECHANICS December, 1947 possible to draw the conic with compass and rulers, an accurate trisection was therefore Letters from Readers impossible.If this isso, will one of your Trisection of an Angle Now by ordinary methods construct FP,mathematically -minded readers kindly explain EQ parallel to BG. how itis that a = 0/3 satisfiesthesecond SIR,-There appears to he a considerable equation above.-G. H. CHILD (Hove). amount of misapprehension on this sub- .. BP -PQ =QD. ject. Most people when putting forward a i.e., BD is trisected. solution to this problem say that it is usually Fluorescent Paints . regarded as being impossible of solution- geo- SIR,-On page 392 of the September issue metrically.The Greek Geometers (of whom of PRACTICAL MECHANICS itiSstated Euclid was one) regarded geometry as an in reply to H. Irvine (Edinburgh) that' you intellectualpastime and laid down certain do not know of any firm which is producing rules for the playing of the game, and they fluorescent paints. said that within theserulesthere was no May I point out that Messrs. Thomas general method of trisection of an angle, and Tyrer andCo.,Ltd.,StirlingChemical within these rules there is no general solution Works, Canning Road, Stratford, London, known to -day. E.r5, manufacture fluorescentpaints in a The chief rules are that, apart from the Now join,AP, AQ and any of the threenumber of different shades.Whilst I have writing instrument (usually a pencil), the onlyangles so formed [LBAP, LPAQ, Z_QAD]no actual experience of these,Icertainly tools permitted are a straight -edge (as distinctis one-third of LBAC.-R. E. BRETT (Finch -have had excellent results from their fluores- ley). cent varnishes, which are available in eight from a measuring " ruler."), and a pair of colours, all of which I have used recently. compasses ;itis not permitted to measure -J. POTTER (Whitley Bay). any dimensions, nor is it permissible to trans- SIR,-With referencetoMr.Rhodes's fer any dimensions. Most solutions break method of trisection in your OctoberSailing Pools for Model Boats down on this last rule, as does the solutionissue, this is interesting and fairly accurate ; given by R. Rhodes in the October issue, as SIR,-In your issue for October I noticed a abouttper cent. out at 6o degrees, tested photograph in " The World of Models" he transfers the dimension OE to EF andby its equation of Mr. Welter launching his model cabin FG. Tan 2a(2+ cos 10)= sin 0. cruiser from a rather high bank. A simple device is sold at stationers' shops In regard to Mr. Coppelman's letter of In the laying out of playing fields, I think by means of which any angle may be dividedthe same page, I agree that 0/3 satisfies thethat it would be a good idea if the model boat into any number of equal or unequal parts.equation in this case, i.e., designer and sailer were catered for, by pro- Its name? A protractor.-D ERB1.4IsT (Bark- sin 0=sin a (1+2 cos0+a), buttheviding a basin with the surface of the water ing). construction is obviously inaccurate for largeslightly above ground level. values of 0 ;as0 approaches 18o° u should This would be of great convenience, and SIR,-May I correct G. H. Child on hisapproach 6o degrees, but .it approaches o.it would provide a good view of the models two statementsinarecentissue ofI think Professor Burnside said about 4o yearsand interest many who are not active partici- PRACTICAL MECHANICS. Firstly, the methodago thatthetrisection was equivalenttopants in what is undoubtedly a most interest- of trisection of an angle given by K. R.solving a cubic equation graphicallyby notinging and instructive hobby that appeals to all Saillard is perfectly true for all acute angleswhere a line cuts a conic, and as it was im- and can be proved geometrically as shown in ages.-DONALD-A. STEPHEN (London, W.). the diagram, Fig. 1. Given the figure in the May -June issue, join " The Atom Minor, Mark III." By OC. Books Received Edgar T. Westbury. Price 3s. od. net. " Practical' Two -Rail' Electrification." " The A.B.C. of Electronics."By E. B. By Ernest F. Carter. Price 3s. 6d. net. Watton, A.M.I.E.E. Publishedby"Planning and Layout." By Henry Percival Marshall and Co., Ltd. 134 Greenly.Price 3s. od. net. pages. Price 7s. 6d. net. " How to Make a Telescope." By Ernest THIS book is intended to meet the demand F. Carter. Price 3s. od. net. for a concise explanation of the scope and possibilities of electronics as related to everyday life. The treatment of the subject is, of necessity, brief, but the information Club Notes given should prove particularlyusefultoEccles and District Model Engineering the student and the general reader interested Society in the subject. Now, for the conditions of the trisection RECENTLY, atwell -attendedmeetings of the angle, OC-CB-radius of the circle " Modelling the held in the club room of the above . LOCB is isosceles and ` Archibald Russell '."society,interestinglectures were givenas LCOB=LCBO=a By E. Bowness. Published by Percivalfollows: Now since L ACO is exterior to A COB Marshall and Co., Ltd. 84 pages. October 26th: The Steam Engine. By LACO --sum of interior opposite, Ls Price 5s. od. net. W. J. Thompson. -20. Q HIP modelling enthusiasts will find in November9th : Fabrication. ByW. In AAOC, OC =OA (radii of circle), 0this book all the information necessaryTaylor. .. AAOC is isosceles to enable them to construct a model of what November 23rd: The Steam Engine (con- . . OAC= LACO -2a. is recognised as one of the finest ships evertinued).By W. J. Thompson. But since LAOD is exterior to A BAO, tosail the seven seas.The book iswell On December 7th various members will LAOD = Z_OAB LABO illustrated with half tones and line drawings.take part in current work on hand, and on -20+0 December 21st there will be a jumble sale.- -3(1. " Gear Wheels and Gear Cutting."ByW. J. Thompson, hon. sec.,16, Prestwood which is the required proof. Alfred W. Marshall, M.I.Mech.E. Pub-Road, Salford 6, Lancs. Secondly, G.H. Childisincorrectin lished by Percival Marshall and Co., stating that an angle cannot be trisected by Ltd. 92 pages. Price 3s. 6d. net. geometrical construction. THE purpose of this useful handbook is Our Cover Subject Itiswell known thatif we divide the to describe the various types of gear base of an isosceles triangleinto a givenwheels in general use for the transmission of THE liner Orcades, of 30,000 tons gross, ratio, say m :n, and join the dividing pointmotion and power, and to explain the princi- built by Vickers-Armstrongs attheir to the vertex, the vertical angle will also beples which govern the formation and numberBarrow-in-FurnessworksfortheOrient divided in the ratio m :n. of the teeth for a given mechanism.TheSteam Navigation Company, was launched earliereditionsof this handbook enjoyedrecently by Lady Morshead.The Orcades A good method is as shown in the diagram,considerable popularity by reasonof thewill be the largest ship to be launched in the Fig. 2. simplicity of its treatment of the subject and,world since the end of the war. The previ- Given the Z_BAC it is required to trisectno doubt, the present revised and enlargedous Orcades, of 23,50o tons, launched from this angle. edition will be equally popular. the same yard late in 1936, was torpedoed Construct an isosceles triangle ABD by and sunk in the South Atlantic in 1942 after cutting of equal parts on AB, AC. Other books recently received from Percivala struggle lasting three hours. Produce AD to X, and from D mark offMarshall and Co. are : The illustration on the front cover shows three equal segments, DE, EF, FG.Join" How to Make an Electric Clock." Bythe liner on the stocks, dwarfing the two -

BG. R. Barnard Way. Price 3s. od. net. storey building in the foreground. December, 1947 NEWNES PRACTICAL MECHANICS 103

oil to it (a few drops to a gill) and see if this makes any whether the materials are obtainable, and from difference. whom ?-R. R. Steavenson (Circencester). If not, it may be that you are not sufficiently degreasing have considerable knowledge and your metal surface before the application of the paint.UNLESSexperience, you you will not be able to glaze pottery QUERIES Scrub the surface down with a hot medium -strengthyourself. solution of caustic soda or soda ash.Rinse well with In principle, the finely powdered glaze is mixed with water.Then allow todry.Paint applied to thiswater to a thin cream.The pottery is dipped into surface should hold well.If it doesn't, try mattingthis cream, allowed to drain.Then it is " fired " in thesurfacewithsandpaper,ifthisoperationis electric ovens at a temperature of 80o deg. C.to convenient.If otherwise, you will have to apply agoo deg. C. for several hours.During this process, ENQUIRIES very thin coating of an oil -bound priming paint and,the materials of the glaze unite together and form a after it has dried, to cellulose over It. speeiesof soft glass which runs in a uniform film over the pottery article.The furnace is then slowly cooled down and the glazed articles withdrawn. A stampedaddressedenvelope,threepenny Electric Heater Control The colour and various other glaze materials may stamps, and the query coupon from the current WHL you kindly advise me on the followingbe obtained from Messrs. Wengers, Ltd.,Etruria, issue, which appears on back of cover, must be -problems ? : Stoke-on-Trent,and fromvariousotherceramic enclosed with every ,letter containing a query. firms in the Potteries district. Every query and drawing whichissent must Two 750 -watt heater elements areto be 'bearthename andaddressofthereader. connected to a control switch which has the A typical glaze composition is the following : Send your queries to the Editor, PRACTICAL following settings :high, medium, low and off. White lead .. 03 parts (by weight). MECHANICS, Geo. Newnes, Ltd., Tower House, There are four terminals In the switch which Feldspar .. zo have these markings4RL-3C-iL.I would Zinc oxide .. .. 3 Southampton Street, Strand, London, W.C.2. be grateful if you could give me the circuit for Plaster of paris

operating on soo v. and zso v. Flint glass ..

Ihave a small medical heater apparatus. China clay .. There are two heater elements and two carbons Paris white I¢ Plumbago Crucible which are all connected in series.The elements Glazecompositions varyenormously.Their com- COULD you please tell me where I can obtainturn, but I cannot get the carbons to strike.I positions depend on the character of the potting clay, materials for a plumbago crucible and thehave fitted two new carbons, but with no success.the character of the glaze which is required, its hardness, correct mixture for same ?I am melting alu-Will you kindly give me the circuit, also any othersoftness, opacity, colour, and on many other factors. minium and propose using dry sand for thereason for the fault ?This apparatus is workingIt is, therefore, quite impossible to formulate a sort moulds.Ihaveaquantityof" Pyruma,"on 250 volts. -C. W. Smith (Tottenham). of universal glaze which would be applicable in all Cases. ' water glass and plaster of paris.Is this of anyAPPARENTLY the switch is arranged to connect If you are interested in the practical side of potting, use as a bonding agent ?-J. A. Wood (Harefield). the two units inseries for low heat, one unitthe following books would be of use to you : IN making a plumbago crucible, mix equal parts ofalone in circuit for the medium heat, and the two C. F. Binns :" Manual of Practical Potting." plumbago and fireclay to astiff dough.Keep units in parallel for high heti, as indicated in the S. W. Anthonies :" Pottery and Modelling." this in a cool place for three days, and knead it fre- sketch.Assuming the elements are rated for 250, volt, H. Barnard :" Art of the Potter." quently, when it will become more plastic and less C. F. Binns :" The Potter's Craft." sticky.The clay should be almost too stiff to work R. Lunn :" Handbook of Practical Pottery." at the time of moulding. H. and D. K. Wren :" Handicraft Pottery." Use an iron or steel mould with a central plug or C. J. Cox :" Pottery for Artists, Craftsmen and core to fit it.Fill the mould with the moulding mix- Teachers." ture.Then hammer the plug or core in to form the hollow of the crucible.The mould is kept in a warm - place for a few days, during which time the formed Astronomical Telescope crucible will gradually harden and contract, thereby making its removal from the mould fairly easy. Finally, T WOULD liketo construct an astronomical after removal from the mould, the crucible should be telescope of suitable power for the scanning put aside for two weeks in a warm place to complete of most planets,etc.What magnification must its drying and setting.When used for the first time, Iuse, and what is the cost of objection and it should be very gently and slowly heated. eyepiece ? How willI be able to determine Pyruma mixed with plumbagomightform a service- " body -length " ?-S. Cheetham(Bath). able crucible, but plaster of paris would be useless. WE presume that you wish to make a telescope Plumbago can normally be obtained from the follow- whichwillenable youtoexamineallthe ing firms :Messrs. Wm. Cumming and Co., Ltd., astronomical " exhibits " such as the phases of Venus, Kelvinvale Mills, Maryhill, Glasgow; Messrs. Thomas the satellites Of Jupiter, the rings of Saturn, and so on. Hill -Jones, Ltd., Invicta Works, Bow Common Lane, For this purpose, the instrument should carry an London,E.3 ;The Morgan CrucibleCo.,Ltd., object glass of 3M. or, at least 2 fin. diameter, and the Battersea ' Works, Battersea Church Road, London instrument will want a body length of from 3ift. to S.W.H. The last-named firm supplies ready-made Circuit for a medical heater apparatus. - 4ift., depending on theexact focal -length of the object plumbago crucibles in various sizes. glass. A simple (non -erecting) astronomical eyepiece (C. W. Smith.) will also be required. At the present time it will be very difficult for you Luminous Powder the above connections would be used on a 25o voltto make such an instrument yourself in consequence r`OULD you supply me with a formula for mak-supply.For use on a soo volt supply only oneof the shortage of materials.If, however, you can connection would be possible, i.e., with the two elements procure a suitable objective and eyepiece, together ing'1/4 agoodluminous(phosphorescent) with a long brass barrel and at least one sliding tube powder ?I have prepared such powders fromin series.With such a connection the rate of heating the sulphides of the alkaline earth metals con-would be the sante as obtained with the two elements carrying the eyepiece, you will certainly make a success so- taining minute quantities of heavy metal com-in parallel on 25o volts, i.e., " high." of the task.Your best plan is to write to one or two Assuming your carbons are of the correct size andsuitable firms asking for quotations for object glasses pounds such as bismuth and uranium, but the and eyepieces, or,alternatively, for complete luminosity (even after long exposure to sunlight)type for the supply, and that the connections areinstruments secondhand.i was .invariably weak. correct, it is possible that the arc may be short circuited. Suitable firms are :Messrs. Broadhurst, Clarkson At the same time I would be obliged if you wouldIn this case the heaters would be " on " even when the and Co.,Ltd., Farringdon Road, London, E.C.4; inform me how such powders are made up into carbons were not in contact with each other.AnotherMessrs. C. Baker, High Holborn, London, W.C. luminous paints. -D. J.C.Pirie(Peterhead).possibility is that the two heating elements should be connected in parallel with each other and in series with It is impossible to give you any exact idea of present- only giveyOu formula:for luminous powders the arc.In this case the present connection wouldday prices.They are greatly in advance on pre-war WE cansuchasyou obviouslyhaveworked from. not allow the elements to reach their correct temperature. costs, when it was possible to purchase a new telescope Since you report that your trials have not been very However, we think it most likely that the carbons are of the above description for about £7 iris.You might successful (which is often the case), we suggest thatnot of the correct type, and would advise you to obtain be able to pick up a Sin. objective for three or four you purchase a small amount of a good luminous new carbons from the makers, if you have not alreadypounds, and an eyepiece for half that amount.But, compound, such asluminous zinc sulphide.This done so.Note that metal electrodes require D.C. unfortunately, as in the case of all scientific instruments, can be obtained (priced about 5s. per oz.) from most the demand is great and the goods are few. laboratory supply houses, such as Messrs. Griffen and Tatlock, Ltd., Kemble Street, Kingsway, London, Glazing Pottery W.C.2, or Messrs. Vicsons and Company, 114, PinnerT WOULD be most grateful if you could tellSilvering Plastics Road,Harrow,Middlesex.Permanentlyluminous me by what process such articles as cups,T SHALL be pleased if you will give me any compounds containing radium may also be obtained information on the possibilities of silvering at a much higher price -say, about zos. per gram. plates, etc., are treated externally, and what istransparent plastics, and the best way to obtain a To make up luminous paints from any of thesethecompositionofthe" glaze "used -also powders, use clear oil varnish or cellulose varnish. This should be obtainab!e from a local paint store. Alternatively,you may makeasuitablecellulose F.-. varnish by dissolving scrap celluloid in a mixture of THE P.M. LIST OF BLUEPRINTS equal parts of acetone and amyl acetate, but, since ."PRACTICAL MECHANICS" 12 FT. ALL -WOOD CANOE.* New Series.No. I.3s. 6d. these solvents are very difficult to obtain at the present, "PRACTICAL MECHANICS " 10 -WATT MOTOR.New Series.*No. 2.3s. 6d. day, you would be advised to purchase your cleart. "PRACTICAL MECHANICS" COMPRESSED -AIR MODEL AERO ENGINE.*New Series. varnish ready.If you cannot obtain such material No. 3. 5s. locally,try Messrs. James Beard,Ltd.,16,Great New Series.No. 4.Is. Ancoats Street, Manchester. "PRACTICAL MECHANICS" " SPORTS " PEDAL CAR.* F.J. CAMM'S FLASH STEAM PLANT. New Series.No. 5. 5s. The reason why your luminous powder formula --1, have not given you the success you desire is because " PRACTICAL MECHANICS " 120 CAR SUPER -DURATION BIPLANE' commercial luminous powder manufacture is a secret (Designed by F.I. CAMM), Full-size blueprint, 2s. process, and itis quite impossible to imitate it on a 10s. 6d. per setof four sheets. The 1-t.c. TWO-STROKE PETROL ENGINE home scale. If "PRACTICAL MECHANICS " MASTER Complete set,7s.6d. ' BATTERY CLOCK STREAMLINED WAKEFIELD = Blueprints (2 sheets),3s. 6d. MONOPLANE -3s. 6d. Spray Painting Metal Sheet LIGHTWEIGHT MODEL MON 0?LANE "PRACTICAL MECHANICS" OUTBOARD T HAVE spray painted some lead -coated iron SPEEDBOAT Full-size blueprint,3s.6d. A sheet with cellulose paint, but when dry I 10s. 6d. per set of three sheets. P.M. TRAILER CARAVAN find itpeels off.What can I do to make it A MODEL AUTOGIRO' Complete set,10s. 6d. adhere firmly ?-J. H. Johnson (Erdington). = Full-size blueprint, 2s. P.M. BATTERY SLAVE CLOCK2s. postfree, from Messrs. GeorgeNewnes, Ltd., Tower House, The above blueprintsare obtainable, UNLESS yoursheet metalis excessively greasy, Southampton Street, Strand, W.C.2. -the cause of the subsequent peeling seems to lie -i-- An * denotes that constructional details are available, free, with the blueprint. in the quality of the paint used.It may not be flexible enough.Try adding a very small amount of castor 104 NEWNES PRACTICAL MECHANICS December, 1947 frosted effect on them.I require curved mirrors However, the varnish can be removed by gently If the preliminary scraping with a copper coin is too of no great accuracy, so any details of the mostroughening the surface in a local area and then by slow a process, soak the bowls overnight in a strong suitablematerial would be very welcome.-rubbing it with the bare finger-tip.If the varnish is at solution of washing soda.Then rub them over with A. Slack (Macclesfield). all brittle, this will serve to powder it up and bring it fine sandpaper to remove the softened varnish. away.Very fine glasspaper may also be used for the 1\4 IRRORS can be produced on the surface of most same purpose.Great care must be taken not to " dig " 1. plastic materials by methods used for the silveringdown on to the canvas too deeply for fear of removing Preparing Surface of Asbestos Sheet of glass, particulars of which can be obtained from anythe actual paint below the varnish. standard book of recipes and formula. A good picture varnish may be made by dissolving AM panelling a staircase in flat asbestos sheet, A typical silvering formula is the following : gum mastic in about -double its bulk of pure turpentine, as I am unable to obtain wood. SOLUTION A theturpentinebeingusedwarm.Theresultant Can you please inform me how to prepare the Silver nitrate .. 6o grains product should have the consistency of thin syrup. surface of the asbestos for painting so as to get Water .. toz. This varish is spread thinly and evenly over the picturerid of the " ripple " which seems to be a character- Pour this solution quickly into a boiling solution ofwith a very soft brush, and the picture is then put asideistic of this material ?-J. B. Louie (Oldham). 48 grains Rochelle salt in about toz. of water.On for the varnish to dry, which takes about six weeks. WE think that you will have much difficulty in getting cooling, filter the liquid, and make up to izoz. with Gum mastic, unfortunately, is very expensive at the rid of the slight degree of " wave " or " ripple water. present time, but it can be obtained from any wholesale which characterises the surfaces of so many sheets ' SOLUTION B chemical house, or from a good firm of artists' materials of the asbestos -cement type.This isbecause any Silver nitrate 6o grains dealers, such as Messrs. Winsor & Newton, Ltd., 38,thin coating of material which you may apply will Water .. 'oz. Rathbone Place, London, W.I. always tend to follow the " ripple " and therefore to Add ammonia drop by drop until the precipitate which Please note that there isno quick and " easy "reproduce it on the newly -prepared surface. is first formed almost (but not quite) re -dissolves, leavingmethod of picture -cleaning and restoration.It is all The best treatment is as follows :Smooth the sheets a faint milkiness in the liquid. difficult, slow, painstaking and sometimes very risky down as much as possible.Then apply a thin " cream" For silvering, mix equal amounts of the above work.Itrequires experience,skill and, above all,of white Portland cement and water, using a brush for solutions and pour them on the surface to be silvered. Do not try a prentice hand on any picturethe purpose.Allow the coating to dry.Brush the Use distilled water for making up the solutions if of value. surface with a dry brush.Repeat the process to build possible.Theplasticsurfacemustbeperfectly up the surface.After the final dry brushing give the grease -free. entire surface a coating of glue size and over this a Silver does not adhere as well to plastics as it does to Circuit for Photoflood Lamp thin layer of some suitable priming paint or distemper. glass, in view of the difficulty of wetting the plasticT WOULD be obliged if you couldgiveme someWhen this has set and hardened, you can apply your surface.It is an aid to pour a solution of stannous A particulars relating to the enclosed diagramfinal coats of decorative paint to the surface. chloride over the plastic surface just before silvering. of a wiring circuit used for indoor photography. To obtain a frosted effect on a plastic surface, merely Lamp A is a 275 -watt over -run filament photo- apply to ita paste of silica and water.Rub in allflood lamp, which if connected directly to the 220 -Colouring Lino directions beneath thefingers and then wash thevolt mains would burn out in about two hours. paste away. By dropping the vtlitage the lamp life is con-T HAVE recently purchased a length of lino, but A find that it is far too light in colour for the If the plastic material is soft, ordinary glasspaper willsiderablyincreased. use it gets in a kitchen. give the required matt surface. May I ask your advice Lamp A on any method by which Electric Soldering Iron 275 Watt I may darken it,say, to HAVE an electric soldering iron forto volt Over run Filameni a brown colour ?I wish IA mains which I wish to use on 220 volt mains. Shorting Switch to avoid,if possible, the Please inform me if this could be done by includ- Photoflood use of one of the many lino paints now onthe ing one Ito -volt lamp in the flex leads.-W. G. market.-A. S. Bampton Jones (London, E.C.). (East Dulwich). 7HE soldering iron could be operated from the zzo volt mains in series with a suitable resistance; a A.C./Veins TO darken your lino, merely lamp could be used as the resistance if one of the correct make up a solution of rating can be obtained.This should be a Ito -volt a brownaniline dyein lamp of wattage equal or very slightly lower than that methylatedspiritor,alter- of the nidering iron.The size of lamp can be taken natively, in an oil -like as correct when the measured voltage across the iron or turpentineorlinseedoil. lamp isIto volts or the lamp lights with normal Brush thissparingly on to brilliancy. 0 100 Watt theclean linosurface and If the mains are A.C., a zzo-volt iron could be allowittodry.The lino operated from Ito volts through a transformer.Alter- Ordinary Electric Globe will be stained at once. could be rewound with wire Resistance Lamp The exactstrength of having half the cross-sectional area of the present wire thedyesolutiondepends and four times the present resistance, i.e., if the same Circuit diagram for a photoflood lamp showing the position of the entirelyonthedegreeto type of wire is used the new element wire should be half 1°o -watt lamp used as a resistance.-(Wm. Grogan.) which you desire to tint the the present cross-sectional area and twice the present lino.Bismarck brownand length. other spiritandoil -soluble The voltage is dropped by lamp B, which is dyes canbeobtained about as. 6d. per oz. from any Ito volt too watts. London chemicalsupplyhouse,as,forexample, Paints for Perspex Is it possible to put a wirewound resistance inMessrs. Griffen and Tatlock, Ltd., Kemble Street, place of lamp B ? Kingsway, W.C.2 ;or Messrs. W. and J. George and T WISH to obtain small quantitiesofpaints The resistance is approximately too ohms andBecker, Ltd., /7-29, Hatton Wall, E.C.i. A (coloured and metallic finishes) which willa amp.Could a resistance of too ohms to carry adhere to clear Perspex. a amp be suitable ?-Wm. Grogan (Liverpool). Can you furnish me with names of suppliers CAN you advise me as to a method of preserving of these and also favour me with the necessary IT is not possible to say exactly what value of resistance the cleanliness of such things as Indian ink formulae for making them myself ?-M. F. Jones would be required, as the resistance of the lampdrawings, mounted on white cardboard, cuttings filamentswillvary with the current and filamentand photographs from periodicals,etc. ? (Bewdley). temperature.It would have been useful to know thedesire to " fix " them, and to prevent their becom-I 'THE paints which you desire are not commerciallycurrent and the voltage at theto -volt bulb or theing hand soiled. obtainable.You can make them for yourself by 275 -watt bulb.However, atoo -ohm resistance to dissolvingclearscrapPerspexintrichlorethylene carrya amp should be approximately correct.Since I have in mind some kind of transparent liquid (obtainable from Messrs. A. Boake, Roberts & Co.,power is wasted in heat at such a resistance it is bound (not dangerous to handle) which can be applied Ltd., Stratford, London, E.15, or from Messrs. W. & J. to get warm or hot.If a resistance of small gauge wirewith a brush and which would set hard. George & Becker, Ltd.,157, Great Charles Street,is used a short wire will be required and this will reach Is there such a proprietary product, or a method Birmingham,3). Whenasolutionofsyrup-likea high temperature; whilst a larger size of wire wouldof making up such aliquid ?-C. E. Pilcher consistency has been obtained, dry paint colour or run at a lower temperature but a longer wire would be (Croydon). metallic powders are ground into the material, theneeded._ The heat generated would be the same in whole then being squeezed through muslin.Painteach case. DISSOLVE fiveparts of the best leaf gelatine in prepared on these lines will adhere well to Perspex. Twenty-five feet of 3o s.w.g. Brightray resistance 95 parts of water and add to the solution a few Metallic powders for paint -making are obtainablewire, as supplied by Messrs Henry Wiggin and Co., drops of carbolic acid in order to prevent it from going from Messrs. John & Bloy, Ltd., Metana House, HindLtd.,of Grosvenor House, Park Lane, London, W.a, mouldy.Use the solution warm (it will set to a jelly Court, Fleet Street, London, E.C.4. These powders arewould make a suitable resistance with probably a little when cold) and) with a camel's hair brush, paint a thin somewhat expensive. to spare. layer of it gently over the surface of the drawing or other illustration which you wish to preserve.The solution will, in this manner, fill the pores of the paper and form Cleaning Oil Paintings Staining and Polishing Bowls a semi -matt surface over the illustrations. T HAVE some oil paintings which are becomingCAN you describe a method of removing the An alternative method is to paint collodion (highly A faded and dusty -looking.Can you suggest 1-,old polish from a bowls " wood " without inflammable)overtheillustrations. Thisliquid any method for cleaning these in order to freshenscratching or damaging the surface of the "wood" ?may be obtained from a local druggist, or it may be up their appearance ?If some special solution isAlso, what is the polish used and how is it appliedmade by dissolving nitro -cotton in a mixture of equal required, could you please inform me where itto repolish thewood " with a black finish ? - volumes of alcohol and ether. can be bought, or howitcan be made ?-S. Fidler (Mountain Ash). Celluloid solution may also be used for the same A. England (Kirkham). purpose.This is made by dissolving scrap celluloid lltOWLS are usually stained with a logwood prepara-in a mixture of equal volumes of amyl acetate and OIL paintings are very difficult to restore,and if tion and subsequently given a wax polish which acetone. yours are valuable, your best planisto washitself may carry a black stain.Sometimes, also,a them well with soap and warm water;dry them andthin film of shellac polish is also applied. In the case of any illustrations, drawings, etc., of hang them in a good light, thereafter leaving them In your case, you will be able to remove the oldcommercial value we should think twice about apply- well alone. polish by carefully scraping the bowls with the upturneding any surface treatment whatsoever to them, since, There is no chemical method which you can apply edge of a copper coin.This requires patience, but thein our opinion, any such treatment might reduce their to freshen up the paintings. method will remove all applied surface without injuring value. After all, a good degree of protection can always When an oil painting becomes dirty and faded andthe underlying wood. be achieved by binding a sheet of clear Cellophane dusty -looking, the cause is generally due to the accumu- You can then stain the bowls with a wax stain madeover the surface to 'be preserved, and this method has lation of dirt on the surface or else a yellowing of theby dissolving paraffin wax in turpentine containing an the advantage that the protective film is readily remov- varnish.The dirt is readily removed by washing with oil -soluble black dye, or you can make a logwood stain able when required. soap and water and, perhaps, with a little soda dissolvedby boiling for two hours in an iron vessel alb. logwood We do not think that any commercial preparations in the water.If the varnishisyellowed, ifit has chips, A lb. green copperas, roz. nut galls, zoz. lampblack on the above -indicatedlinesareavailable, but an cracked and become darkish and brittle, the best thingand I gallon of water.This liquor is then strained andinquiry addressedtoany well-known firmofart to do isto remove itcompletely and to re -varnish applied hot to the bowls.. Two or three coats may be materialdealerswould soon bring you up-to-date the picture. necessary.Finally, the bowls should be rinsedin information on this point. Two such firms are : Messrs. It is here that the tricky business comes in, and cold water, allowed to dry slowly and then wax polished.Windsor and Newton,Ltd.,38,Rathbone Place, unless you feel that you can afford to experiment on the A final thin coating of shellac varnish may be necessary London, W.I.Messrs. Reeves and Sons, Ltd.,18, picture, we should not advise you to proceed further. if a very high gloss is desired. Ashwin Street, London, E.8. December, 1947 NEWNES PRACTICAL MECHANICS 105 Arealengineeringjob for the MODEL ENTHUSIAST

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SELF - LOCATING NO MARKING OUT NO MEASURING NO GUESSWORK

The Prestacon Press pierces, bends and work to be done to within precision routs metal strip and sheet with absolute limits without measurement.It is an Prestacon Precision Press accuracy for making up a wide variety of exceptionallyversatiletoolthatsoon is available as models, parts for radio and other hobbies, becomes indispensabletothe model No. IPress and Tools and many utility purposes in the home. engineer and handyman,and,being Price55/- Ingenious " location " bars make marking simple to operate, makes a wonderful gift out unnecessary and enable repetition for any boy who is keen on engineering. No. 10 Complete Outfit comprising Press, Tools, together with supplies of Write to -day for illustrated pamphlet and name of metalplate,andstrip nearest Prestacon Dealer to Sole Concessionaires :-L. REES&CO., LTD. axles, wheels, nuts and bolts, drawings etc., to DEPT. N, I. 31-35, WILSON ST., LONDON, E.C.2.'Phone :Monarch 2651 (5 lines)'Grams :Elreesonia,Finsquare,Londan make a variety of models. Price 84/- 106 NEWNES PRACTICAL MECHANICS December, 1947 Some Fine Investments ! GALPINS MOTORS. Electradix ELECTRICAL STORES Micro Motors for Instru- ment work and models 403, HIGH STREET, LEWISHAM, 2in. x 1 lin., weight

LONDON, S.E.13 LEARN only 10 ozs. 12124 volts ; Telephone Lee Green 0309. Near Lewisham work from dry cells or A.C. Mains through Hospital transformer, laminated fields, ball bearings, totally enclosed, small vee pulley, centrifugal TERMS: CASH WITH ORDER. relay speed governor on shaft removable NO C.O.D. TO for second shaft drive. Precision made EX-R.A.F. CALIBRATOR UNITS ex W.D. stock.Worth 451, Price 211 - TYPE IS.These units consist of 1-100 klc each.Limited stocks. Xstal 2-EF 50 valves and numerous other MOTORS. D.C. 230 -volt D.C.1112 h.p., components (new boxed), 351- each, P!F. 1,50012,000 r.p.m. shunt wound by Croydon, EX-U.S.A. ARMY HAND DRIVEN 251-. 1140 h.p. 110 v. or 220 v., 1716. 1130 GENERATORS (as new). Output 162 EARN h.p.12 -volt with 4 -hole base plate,75:-. volts at 60 mla, 3.1 volts at .3 a., complete MOTOR BLOWERS, as new, by Keith with all smoothing and circuit diagram, 351 - Blackman,24voltD.C.serieswound, 5in. inlet and outlet, a robust machine, £5. each.Ditto, 425 volts at 115 mla, 105 volts, 32 mla, 6.3volts at2.5 amps., 6.3v.at MOTORS. D.C.220 volt 1'12 h.p., need- .43 amps. at SS/. each. Leave the overcrowded ranksof the poorly paid-let ing minor repairs, 12 6 each, postage I 6. TRANSFORMERS. B.T.H. 20012301250v. A SPECIAL LINE OF VOLTMETERS. The Bennett College help you to the top where there is 50 cy. input, 2 volts 20 amps. and 75 volts First -grade Moving Cod 0 to 20 volts, 2in. 6 amps, with 15 taps output. 651-. 2 kw. lots always plenty of room for the well -trained. Just choose square face, new boxed, 101- each, in 400 voltinput 220volts 50cy.output of 3, 251, your career or let us advise you.The Bennett College tapped every 25 volts, £811010. EX-R.A.F. MICROPHONE TESTERS. its CIRCUIT BREAKERS. N.C.S.7! amp. These consist of a Ferranti 22,in. mlcoil 0 to with proud tradition offriendlypersonaltuition A.C. enclosed type, 251-. I mla meter with Westinghouse Rectifier and its long record of triumphs, is the most progressive, METERS D.C. MovingcoilWeston incorporated, calibratedatpresent 0 to Meters2in.dia.flushfitting,fullscale 10volts, microphone transformer,jacks, most successful Correspondence Collegein the World. 500 micro amps.Scaled forIS volts and etc.,allcontainedinpolished teak case, We teach nearly all the Trades and Professions by post 600 volts will measure 15 volts, but need size 61in. x 51in.Condition as new.Price external rises for high voltages.201-. 3216 each. allovertheGlobe. DISTANCE MAKES NO DIMMER RHEOSTAT SWITCHES. LARGE RECTIFIERS FOR CHARG- DIFFERENCE. I ohm 3 amps., for regulation of 6 volts ; ING. 6 or 12 volts at 618 amps. Complete one hole fixing, hollow knob has base for with mains transformer for 2001250 volts miniature bulb to glow when " on," 216 each, plus 6d. postage. 50 cy. I ph., £51216, carriage paid. * CHOOSE EX -GOVT. NEW MAINS DIMMER YOUR CAREER AND SWITCHES. RESISTANCE, worm wheel control, 700 Dewar key panel toBlackout. WE WILL SEE YOU TIIIIOUCH type, 7 -pole C.O. wattsvariationfromfull flush fitting, SI-. Price £31101- each. Accountancy Examinations Mining, Electrical Engineering Yaxley 3 -pole EX -GOVT. VARIABLE RESISTANCES Advertising and Sales Management Motor Engineering 3 -way,316 ; 8 - (new), 450 ohms, carry 7 amp., 301- each, Agriculture Municipal and County Engineers pole1 -way, 316. D.P.C.O. toggle switch - 4,000 ohms, carry 1 amp., 3716 each. A.M.I. Fire E. Examination Naval Architecture 250v. I amp.,flushpanel,313 ; 8 -way MAINS TRANSFORMERS. Ex -Govt. Applied Mechanics Novel Writing Lucas switchbox, 316 ;6 -way, 31-. (New). Tapped input 2001250 volts 50 cys. Auctioneers and Estate Age:,ts Plastics TELEPHONES. Wall type constructors'

I ph.Output 350101350 v. 180 mla. 6.3 v. Aviation (Engineering and Wireless) Play Writing parts, ex-G.P.O., comprising cabinet 4 a., 5 v. 3 a.. 4 v. 4 a., 3716 each.116 post. Banking Plumbing Bin. x 6in. x 3in., bracket mike, trans- Another 500101500 v.ISO mla., 6.3 v. 4 a., Blue Prints Police, Special Course former and condenser, mag. bell, switch - 5 v. 3 a., 4 v. 4 a., 4716, post 116.Another Boilers Preceptors, College of hookand contacts, handmag., ringer 6, 12 and 24 volts,10112 amps., 451- each, Book-keeping,Accountancy and Press Tool Work P.O. type receiver terminals and connection post 21-. Another14/and 171 volts at Modern Business Methods Production Engineering diagram, 351- per pair.G.P.O. Candlestick 30 amps (auto wound), -£41151-, post 216. B.Sc. (Eng.) Pumps and Pumping Machinery Telephone with receiver and cord, 151-, Another 700101700 v. 80 rela.,12v. I a., Builders' Quantities Quantity Surveying-Ins, of Quan- postage 116.Spare mike inserts, 216 each. 4 v. 2 a., 301, Another 350101350 v. 200 mla., Building, Architecture and Clerks tity Surveyors Exams. TERMINALS. Brass orplatedBelling 6.3 v. 20 a., 5 v. 3 a., 451-, post 216. Another of Works Radio Service Engineering type Terminals,withnuts andwashers, 4, 6.3 v. and12.6 voltsat12 amps., 451-, Cambridge SeniorSchool C rti- Radio (Short Wave) 6d. each, 51- doz. Large insulated terminals, post 216.Another 171, and 20 volts at 30 ficate Road Making and Maintenance Belling type,II- each,101- doz. Wander amps., 95!-, post 316. Carpentry and Joinery Salesmanship I.S.M.A. Plugs, Red and Black, 31- doz.Croc. Clips, Chemistry Sanitation TRANS- small,31- doz. ; large,816 doz. Mk.III VOLTAGE CHARGER Civil Engineerin: School Attendance Officer FORMERS (Auto Wound), tapped 0,110, Civil Service double brass terminals, with nuts, 716 doz. 200, 220 and 240 volts, 350 watts, 551-, post Secretarial Examinations All Commercial Subjects Sheet Metal Work CRYSTAL SET. The 116. 500 watts, 701-, post 21-.1,000 watts, Commercial Art £5151-, post 216. 1,500 watts, £71151 -,post Shipbuilding Lesdix Bijou Crystal set Common Prelim. E.J.E.B. inbakelitecase,semi - 316. 2,000 watts, £81151-, post 51, ouble Shorthand (Pitman's) Concrete and Structural Engineer- Short Story Writing perm. detector, con- Wound, 2 to I ratio (1201240 or vice -versa), ing 4,000 watts, £121101-. CIF. Social Wel 'are densertuning. 151-. Draughtsmanship, all Branches Speaking in Public Headphones, 2216pair, AUTO WOUND TRANSFORMERS Engineering, all Branches, Subjects Structural Engineering with cords. (Mains Boosters), tapped 0, 6,10,19,175, and Examinations Surveying 200, 220, 225, 240 and 250 volts at1,500 General Education Teachers of Handicrafts BUTTON MICRO- watts (new ex -Govt.), '?5/10/-, post 51, G.P.O. Eng. Dept. Telecommunications PHONES provide Heating and Ventilating (City and Guilds) interestingexperi- LARGE MAINS TRANSFORMERS, ex ments for making out- Govt. (New), Input 2001250 volts, 50 cys., Institute of Housng Television Journalism Transport Inst. Examinations sidelisteners,sound I ph., in steps of 5 volts.Output 30135 volts transmission,etc. at 100 amps.Price £12, CIF. Languages Viewers, Gaugers, Inspectors Mathematics Weights and Measures Inspectors These ex-G.P.O. Voice AUTO WOUND TRANSFORMERS Matriculation Welding Units are underlie. (Voltage Changer), tapped 0,10,20, 25, Metallurgy Wireless Telegraphy and Telephony diam., filled carbon 90,.130, 150, 190, 210 and 230 volts at 1,000 Mining, All Sub;ects Works Managers granules and fitted watts. (Itwill be ,seen that almost any mica diaphragm, 316 each. Special Trans- voltage can be obtained from this Trans- If you do not see your own requirements above, write to us on former and Condenser,SI-. Instruction former). Price £51101-, post 51-. Leaflet with eachButton. G.P.O. Mike any subject.Full MAINS TRANSFORMERS, EX -GOVT. particulars free. inserts, 216. HAND MIKES in moulded bakelite Input 230 volts 50 cys. I ph. Output 121 volts C.T. at 25 amps., 451- each, carriage 51-. case, 416. Tannoy hand mike, multi -cell COUPON. CUT THIS OUT carbon type, metal case with neat switch METERS ALL BY WELL-KNOWN inhandle, 1216, special transformer, 816. MAKERS. Ex -Govt. new boxed 1st Grade illEMIEMMINIZIN SEND -RECEIVE Hand -corns. All -metal Moving Coil. 0 to I mla., 211- ;0 to 40 volts, fieldtype ;the famous No. 16, Govern- ; To Dept. 76, THE BENNETT COLLEGE ; IF 151- 0 to 10 amps., 151- 0 to 5 mla., 1716 YOU AT- ment pattern, as used in field telephones : 0 to 20 mla., 1716; 0 to 50 mla., 201-; all TEND TO THIS LTD., SHEFFIELD 2in. fsd. 0 to 3 mla., 2216 ;0 to 50 mla., 2216 ; mike and ear piece with damaged switch 0 to 200 mla., 2216 ;0 to 4 amp. Thermo NOW IT MAY inhandle, 51-each. Mouldedbakelite MAKE A Please send me ex-G.P.O. Hand -corns. with switch in Coupled, 301- ; 0 to 20 volts A.C., calibrated (freeof charge) handle, cord and plug, 151-.Double Head- 50 cys., 251-; 0 to 3,500 volts Electrostatic, WONDERFUL (Cross out line phonecords,216. 35/-.All 21in. fsd. Particulars of 4 -way5 -footcords, DIFFERENCE whichdoes ex-G.P.O., 216. L.T. RECTIFIERS (new). 6 volts, 1/ amp., TO YOUR Your private advice not apply) MAGNETS. D.C. Electric magnets, 7/6 each, 12 v. 11 amp., 1016 each, 9d. post. FUTURE. about weight 10oz.,lift on 2 volts,1.11b., 4 volts Instrument Rectifiers, S.H.,10 or 20 mla. 31b.,6 volts 41b., new, surplus, 716 each. PLEASE WRITE IN types, 416 each. BLOCK LETTERS Permanentpowerfulflatbar magnets, MAINS CHOKES, 9 hy., 100 mla., 616; 22in. xlin.xlin.,drilled 2 holes each 20 hy., 120 mla., 1016 each ; 30 hy., 150 mla., Name end, for any pole pieces,21-pair. The 2216 each.Mains Transformers, 230 volts, wonder Midget magnets.Alni perm. steel 50 cys. I ph. input, Output 500101500 volts Address I disc. ; 2in. diam., '2in.thick, with 31I6in. at 250 mla., 5 v. 3 a., 4716 each. Another with I centrehole, 316each, Large stockof two windings of 61 volts 5 amps., 301- each ; Horseshoemagnets. Sendforspecial another with 350101350 v.,180 mla., twice L11311MMINIIIMINIE o a WWI IBM SIM MINI MOS a 11111110111111INIMINI Mal Magnet Leaflet " P.M." three 6.3volt windings and two 5volt Please include postage for mail orders. windings, 4216 each ; another 50 volts at approx. 50 amps., alsoa 5 volt winding, £31151-, each CIF. Allthe above Trans- ELECTRADIX RADIOS formers areverylargetype,soplease Ze Co//eyewitha aswellasbrains 214, Queenstown Road, London, S.W.8 allow 316 for carriage. Telephone : MACaulay 2159 December, 1947 NEWNES PRACTICAL MECHANICS 107 PELMANISM TYPE ML7 and 31" HEAVY DUTY LATHE The Frustration Complex The finestLatheinitsclass.. THOUSANDSof people to -day Extensive arelivingfrustratedlives. rangeof Day after day they are haunted accessories. by a sense of frustration.They Building feel they are being baulked in their desires to do the things they really want to do. They feel they a Galleon are not living the lives they really want to live. The book with the plans They feeldiscontented,dis- gruntled, dissatisfied.They are Written and illustrated by men who uneasy and unhappy.And, as a know all the secrets of ship -modelling MYFORD ENGINEERING COMPANY LIMITED result of suffering from frustration, forexhibition,thisbookisso bEESTON NOTTINGHAM 'Phone: 54222 (3 lines) they often become the victims of attractively presentedit makes an 07.148B other mental evils as well.They . ideal Christmas gift. The plans are becomeIrritableandMorose. for Drake's " Golden Hind," but the ELECTRIC ENGRAVERS. -Powerful They have fits of bad temper ; LABORATORY instruments Incylindricalcase, on book is an asset in making any of the stand with spring attachment and their thoughts become Morbid. other twenty-six " old-time " ships APPARATUS AND CHEMICALS switch.Suitable for dog collars, tool They feel Depressed and Pessi- marking, etc.,4-6 volt model, price in our list. for Student and Experimenter' 50/- A.C. Mains model: 200-240 volts, mistic. Send 2d. Stamps for New Apparatus 60/- A.C. Engraver only 50/-. Thisleadstoinefficiency in PRICE :12/6(Postage 6d.) Price List TELEPHONE SETS,comprising 2 G.P.O. hand phones. 2 bells. 2 pushes business and to friction and un- A Selection from our Students List. and 80ft. twin wire.Price 65/-. post (Complete with. set of 8 plans) MICROSCOPE (Student) in case mag. free. Singleinstrument. 25/8. happiness in the home.It makes x 100, £4 9s. 6d.Evaporating Basins 6 inch Brass Brackets bin. thread, 1/9. men and women amiseryto 75 mm:. 1/8 ea. 100 mm., 3/3 ea. Crucibles S.B.C. Fancy glass shades 1/9. Circular 32 mm., lid.38 mm., 1/-41 mm., 1/1 resistances on china base 10 ohm., 2/-. themselves and all around them ; Modelcraft's NUMBER 4 ea. Beakers 100 ml., LS ea.Flasks 150 ipl., 1/10 ea. Beaker Covers (Clock Screwplates for threading 0 2 4 B.A. 4/6. their condition is purely mental. Glasses) 3in.. 4d. 4in. 8d. each. Bottles MOTOR. --4-6v.dry batterydriven, MAGAZINE tfc' LIST Bakelite Screw Cap 16oz., 10d. each. well made, powerful, 11/6.Illustrated It has its root in certain known 24oz., 1/2 ea.Calcium Chloride Tubes list.6d. Carbon Diaphragm anddefinite Brighter than ever, this Christmas number 1/- each and carbon granules 6d. packet. causes which can has articles by K. N. Harris, I. T. Hal, Straight 4in.. 8d. ea." U " 41n., 10d. BATTERY CHARGERS FOR A.C. easilyberemovedbycorrect K. M. Blake, " S,"R. V. Worth and ea. Gas Jars 6in. x llfn., 1/8.Cover MAINS. FOR CHARGING 2 -volt accu- others, and an even longer list (over 400 21d. ea. Pipettes 10 ml. Bulb Form. 1/11 mulators at /amp.Parts with diagram, treatment and training. ea. Rods Glass Stirring 8in., 3d. Bun- 12/6. Complete 21/6: Postage 10d..., items) ofkits,plans, - - sen Burners (Students), 2/-.(School), FOR TRICKLE CHARGING CAR planbdoks and accessories.I/- rost free 2/6 ea.Rubber Tubing for same 5d. CELLS, parts with diagram.Output Half fees for serving and ex -service members per foot. Thermometers 0 deg. -360 deg. For C., 6/10 ea.Test Tubes 2in. x 3/81n.. 11 amps, for 8v. cells,80/- set. of His Majesty's Forces. 3M. x 3/8in. and 3M. x sin., 10d. per 12v.cells, 35/-set. (Apply for Services Enrolment Form.) Modeleraft Ltd. doz. 41n. x fin., 11d. per doz. 5in. x lin., Larger sizes quoted for. 1/1 per doz.6in. x lin., 1/2 Per doz. MINIATURE HEAD- 77(1), Grosvenor Road, 6in. x 5/8in.. 1/3 per doz. Specimen PHONE. Reproduces Tubes Corked 3in. x fin., 2/2 per doz. equal to best 'phones. Mental Scienceisconquering Fits into ear, doesnot..; CHEMICALS ARE QUOTED ON require headband. Two this modern curse, and this feeling APPLICATION nipples large and small Electrotors type 240.3-6 volts, 5,000 10 ohm or1.000 ohm. - of frustration is easily and swiftly 'r.p.m.. 8/6 ea. Post 4d. Blackorflesh en- removed by a course of Pelmanism POST RADIO SUPPLIES Electrotors type 441.6-24 volts, 4,500 amelled. 4ft. cord. r.p.m., 17/6Post 6d. Price 30'-. as directed through the post by OFFER FROM STOCK: - VICSONS &Co. (Dept. Lab. P.M.) ECONOMIC ELECTRIC CO., the experienced instructors of the COPPER INSTRUMENT WIRE. 148, Pinner Road, 64,LondonRoad, Twickenham, Pelinan Institute. ENAMELLED17 S.W.G. -42 S.W.G. HARROW, MIDDLESEX Middlesex. Tel.: POPesgrove 1318 TINNED & FUSE, 17 S.W.G. -42 S.W.G. Pelmanism eliminates the feel- COTTON COVERED,16 S.W.G. - ings of Frustration and Inferiority 45 S.W.G. (and many other weaknesses as SILK COVERED, 16 S.W.G. SCREWS, NUTS, WASHERS, soldering MODEL ENGINEERS well) and develops and strengthens tags, eyelets, rivets, etc. your. Will -Power, your Determina- EBONITE & LAMINATED BAKELITE FOR THE TURNER: ation and your powers of Initiative PANELS. Lathes, 31 and 4+ S.S. Bench Millers.Drilling Machines. PAXOLIN TYPE COIL FORMERS & and Concentration. TUBES. ALL DIAMETERS. FOR THE WOODWORKER: So why suffer from these failings COVERED WIRES, FLEXES, etc. any longer ?Whatever your age, CRYSTALS, PERMANENT DETEC- WOod Turning Lathes, 2+" and5rcentres.4in. Planers.Saw whatever your occupation,Pel- TORS, EARPHONES, etc. Benches. Sanders. Spindle Moulders. List S.A.E.Trade supplied. manism will free your mind from POST RADIO SUPPLIES theseunhappyconditionsand 33, B Gardens, London, E.4. Pedestal Jig and Fret Saws. change for the better your whole Perspex -All sizes and colours in stock. outlook on life. A ReallyUniversal Motor The general effect of the train- ingisto induce an attitude of "A.C.-D.C." Car. Faid NUTTALL'S (LATHES) LIMITED, mind and a personalefficiency 12, 27, 200-250v., by ample adjustment of MANSFIELD, NOTTS. favourable to the happy manage- FieldConnections. Ap- ment of life. prox.kh.p., 6,000 revs. Remember -Everything you do is -f Threaded Shaft. 35,- preceded by your attitude of mind. Morton & Dismore, isfully 52c, Old Church Rd., NEW The Pelman Course Chingford, E.4. EX. R.A.F. described in a book entitled " The MAKE THESE YOURSELF Science of Success." The Course issimpleandinterestingand ti DO YOU WANT A AND MAKE takes up very little time ;you can enrolonthe most convenient LATHE? terms. The book will be sent you, MONEY! gratis and post free, on application Why not make your own from readily obtainable materials. With ourtoy -castingmoulds and to :- Toy Soldiers, PELMAN INSTITUTE Clear diagrams andinstructions, fast -drying enamels, making these and Cowboys&Indians, other models becomes a really profitable (Established over50 years) - Wild & Farmyard pastime, or fascinating hobby.Full in- ppost free. Animals, 530, Norfolk Mansions, 3/ to Aeroplanes, structions with every first order.Send Wigmore Street, London, Wa Ships, Cars, etc. s.a.e. for full details. Write to -day ! Postedpromptly,as represented or Write or call for this free book to -day. immediate refund. Callers welcomed. PROGRESSTOY CO.LTD. PEI MAN (OVERSEAS) INSTITUTES : PARIS, 178BoulevardHaussmann.AMSTERDAM. P.M. BARHAM, Bridge Damrak,68.NEW YORK.271North Avenue, Dept. P.M., KIRBY ROAD, BLACKPOOL, S.S. New Rochelle MELBOURNE. 396 Flinders Lane, Avenue, St. Sampsons, Telephone :BLACKPOOL 750 DURBAN, Natal Bank Chambers (P.O. Box 1489). JOHANNESBURG. P.O. Box4928. Guernsey, C.I. CALCUTTA.182Clive Street. DELHI.10 Allpore Road. 108 NEWNES PRACTICAL MECHANICS December, 1947

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BRANCHES AND SALES DEPOTS AT BIRMINGHAM, BLACKBURN, BRISTOL, CARDIFF, EDINBURGH, GLASGOW, LEEDS, LIVERPOOL, MANCHESTER, NEWCASTLE, NOTTINGHAM, SHEFFIELD (Ph.3 I I B) December, 1947 THE CYCLIST 17

All letters should be addressed to theEditor, "THE CYCLIST," GeorgeNewnes, Ltd., Tower House, Southafnpton Street,Strand, London, W.C.2. Phone : Temple Bar 4363 Telegrams : Newnes, Rand, London VOL. XVI DECEMBER, 1947 No. 309

Comments of the Month By C. The Road Safety Campaign

MR. G. R. STRAUSS, M.P., Parlia-Road Safety Campaign, therefore,inourreally responsible for the 25 per cent. reduc- mentary Secretary to the Ministry ofview should go on. tion referred to earlier, then we may expect a Transport, was the chief guest at the The Committee on Road Safety express thecontinuation ofitsbeneficent influence,so Congress of the Royal Society for the Preven-view that vehicle defects may have been athat in a matter of five years the number of tion of Accidents, and the main theme of hiscontributory cause ofalarger number ofaccidents will be negligible.Itisfatuous speech was the Road Safety Campaign andaccidents than is shown in the pre-war roadtoselect the first post-war year, which is the results it had achieved.It is not possibleaccidents statistics.With this point of viewbound to show areduction, anyway, and to relate reductions in road accidents to any we entirely agree. compare it with the year before the war. specific remedial measure, but in support of As part of the American Road SafetyThe time to assess the Road Safety Campaign his statement that the campaign has producedCampaign a check was made by the Unitedisinthree years' time when, ifaccidents worthwhile results, he said that whilst in theStates police last year on nearly 3,000,000continue to show a decline of 25 per cent. second quarter of 1939 1,560 persons were vehicles.Of this number it was found thatper annum there will be some justification for killed on the roads and 58,722 were injured,atleastone-third were defectivein somesaying that the money and effort involved has in the second quarter of 1947 1,174 personsimportant respect.In this country the Roadbeen worth while. were killed and 43,154 injured.In otherTraffic Acts enable technical officers of the At present we are of the opinion that a words, the 1947 figures are about 25 per cent.Ministry of Transport toexamine publiclarge amount of money has been wasted. lessthan thoseforthesimilar periodin service vehicles and goods vehicles. The Road Widow poster, for example, has 1939 - As a part of Safety Weeks arranged bynot, in our view, been responsible for pre- The number of vehicles licensed in thesome local authorities the Ministry's technicalventing one accident, yetit has cost large 1947 period was slightly higher than thatofficers have collaborated with the police insums of money. in 1939, and so was the total fuel consump-the inspection of goods vehicles on the roads. Not until we have practical road users in tion.Neither roads nor vehicles are in as Of 209 vehicles examined 108 were foundthe Ministry of Transport, not mere politi- good aconditionas they were before theto be defective, and in 53 cases the defectscians and statisticians,will road affairs be war, and owing to the shortage of manpowerwere sufficiently serious to justify prohibitionsensiblydirectedandcorrectconclusions the police are not able to devote as muchof use of the vehicle.Steering and brakedrawn.The traffic muddle in London, for attention to road traffic. defects were the main faults. example, is a scandal.If Ministry of Trans- We dd not agree with Mr. Strauss that The Committee on Road Safety, believingport officials had to use the roads of London there has been a " remarkable " drop in thethat those concerned with road accidents andwe have no doubt that the conditions would number of accidents.He attributes the drop,their prevention should have complete in-have changed a long time ago.But then, such as it is, to the need to conserve vehiclesformation about the cause of accidents, hasmost Ministry of Transport officials, when and the difficulties in obtaining spare partsrecommended in itsfinal report the settingthey use a motor -caratall, are chauffeur and tyres, which have led to more carefulup of a comprehensive system of road acci-driven in a State-owned car. driving and to the Road Safety Campaign.dentstatistics. This recommendation has It is our view also that too much authority It is, of course, impossible to segregate or tobeen accepted by the Ministry of Transport. is given to the police in the matter of traffic measure the effect of these two factors.It is control.They have power to close roads, natural that Mr. Strauss, as an official of theControl of Pedestrians causing the most chaotic trafficconditions, Ministry of Transport, should assume thatIN the memorandum submitted by the Road-because of some mediwval ceremony like the the Road Safety Campaign has been the more farers' Club to the Ministry of Trans-opening of Parliament.What isrequired important factor. port,several recommendations were madeis less traffic control. We do not think so.We think that onewhich have been adopted by the Committee. of the causes of the drop is the greater skillThe Roadfarers' Club suggested, for example,ScarcerStill of drivers as a result of wartime training.that there should be control of pedestrians. IN view of the export drive bicycles and We do not think, in view of the limitation of We hear too much talk about motorists accessories are going to be scarcer than mileage imposed by petrol rationing, that sobeing in charge of lethal weapons, and tooever.We think this is a mistaken policy on many miles have been travelled, and thislittle about the crass carelessness, leading tothe part of the Government.The bicycle is would naturally account for a drop in theaccidents which motoristscannotpossiblythe means by which hundreds of thousands of number of accidents.The average mileageavoid, on the part of pedestrians. people get to and from their work.Itis covered by a motorist before the war was Roadsaremainly madeforvehicularcheaper than, any other form of transport, about 10,000 miles.Under the petrol ration-traffic. In the name of road safety largeand relieves the public service vehicles of ing scheme it would be less than 5,000 miles.numbers of experiments have been made andundue pressure during rush hours.Because The total fuel consumption, ifas a facta number of regulations introduced control-many bicycles cannot be put into good ser- itis in excess of 1932, can be accounted forlingtheuseandconstructionofmotorvice,an added financial burdenistobe by the fact that mosf cars on the road arevehicles.Many of these experiments havethrown on to the user and public services old cars, and are not doing so many milesproved failures since dey have not materiallyalready overcrowded will be less comfortable to the gallon,, by the slightly increased num-affected the accident problem.We do notthan ever. ber ofvehicles on the road, and by thethink that road traffic should be reduced to a The bicycle is a door-to-door vehicle. Many greater consumption for industrial purposes. farce if they fail in their object.The manworkers reside in districts which may mean It would be wrong to assume that now themostresponsibleforobstruction,whichas many as three changes if public service basic petrol rationing is withdrawn there iscreates conditions under which accidents canvehicles are used.Apart from the shortage no -longer the same need for the Road Safetyoccur was Mr. Hore-Belisha, who smotheredof new machines there is a greater shortage Campaign.One effect of taking vehicles offthe country with thousands of unnecessaryof spares. It is adding an extra and an unfair the road will be to speed up the remainingtraffic lights which do no more than to coagu- ,burden on workers to expect them to work traffic in busy streets, therefore the risk oflatetraffic instead of keeping itfluid andharder than ever before as they have so often accidents on those streets is not likely to beseparated, and reduce speedtosomethingbeen exhorted to do by politicians quite out much less than it is at present. little better than walking pace. of touch with the public, and then to travel The object of the campaign is to form en- Pedestrians must be educated to the viewhome by public service vehicles which take duringhabitsofsafeandsensibleroadthat the roads are hot specially made fortwiceas long asa journey on abicycle. behaviour based on the 'principle that self-them and that they cannot do what they likeThe Manufacturers' Association have been preservation is the first law of nature.Theon them.If the Road Safety Campaign ispressing to have this position changed. 18 rHE CYCLIST December, 1947

withsidelights-parkingchildren go nearthewateruntil theycould lights they are rightly knownswim, and South Derbyshire Education Committee as in Canada." appears to be taking up a similar attitude with regard to child cyclists.They are urging parents to stop their WheretheEnergy children cycling to school, and recommend that schools should stop providing accommodation for cycles, saying Goes that the children cannot ride without being a danger

EXTENSIVE researchto themselVes and others on the road. work into questions re- lating to fatigue in racing cyclists and other athletes isReally Black Spot being carriedoutinthe size the Leicestershiretownof Lough- Department of PhysicalFORborough its has an unenviable reputation for road Education of California accidents.According to the local police superintendent: University.In one experi-" So many black pins-used to denote accidents-have mentacyclistpedalsa been stuck in the map this year that we have had to get stationary cycle and as hea new map." breathes his exhaled breath passesthrough ameter, while other devices measureExpensive Ornament increases in the beating of the heart and the onset ofATrowbridge, Wilts, there was an ancient lock -up fatigue symptoms.Experi- which was used up to a century or so ago for mentshaveshownthat housing drunkards until they sobered up, but during smoking affects the steadi-the late argument with the Germans a random bomb 11r-vtace ness of the hand and pulsewrecked the place.To rebuild it will cost £zoo, and Cornwall the council have agreed to the rebuilding so that they rate but the research workerscan get the money back from the War Damage Com- The 90aiRt. Post- Office refuse to say whether or not mission.But the lock -up will have to be rebuilt on smokinghasanyactual the exact spot where it stood before and where it blocks harmfulphysical effects the flow of traffic, otherwise the War Damage Com- upon the body. mission will not pay up.The council have plans for Flowers - ButNo widening the road where the lock -up stands, so no doubt in a few years' time more money will be spent in pulling Bouquet it down again. ALTHOUGH concrete, labourand apparently Not the Right Spot everything else these days arein short supply,Scooped the Pool ALETTER has been received by the Urban Council Leicester City Council has decided that now is the time of Sleaford, Lines, from a woman now living atto build concrete -bordered. flower gardens in the centre IN one season, J. O'Connor, of the Grantham Road Pampas, Queensland, askingif her husband's ashesof Charles Street to separate the trafficlines.The IClub, has collected all the club's course records. cart be sent to England and buried at .the foot of hissight of the flowers and the thought of the concreteHis latest feat was the clipping of eight seconds off the grandfather'smonument,theHandleyMemorial, and other materials, not to mention the labour, that has t935 club record for the 3o -miles T.T. championship, which stands at the junction of Southgate and Boston been wasted will no doubt help to cheer up thosewhich was formerly held by L. Page.In spite of Road,Sleaford.Unfortunatelyfortheidea,the unfortunate couples who, with luck, will have housesadverse conditions, O'Connor covered the course in council is proposing to move the memorial because ofbuilt for them some time during the next 2o years. hr. re mins. 36 secs. the trafficcongestion which itcauses, and they areOne critic has suggested that the flower beds should be suggesting that the late Mr. Handley's ashes should decorated with a series of maypoles, around which the find a resting place elsewhere. citizens may dance to celebrate the crisis. No Encouragement PRESUMABLY, with the shortsightedideathatif children do not cycle they are not'. likely to be Menaces ! Looking Ahead involved in road accidents, Nottinghamshire Education DESCRIBING schoolchildrencyclists at Brigg, WITH a view, evidently, to the possibility that cyclesCommittee have approved a suggestion that children Lines,as" menaces tothemselves and other will become scarcer than ever with the newunder to years old in the county should be discouraged road users," a member of Brigg Road Safety Committeeexport drive, Mr. H. T. Garley, managing director offrom cycling to school.Cycle accommodation at the stated that boys make a habit of cycling through thethe Garley Cycle Co., Ltd., Lower Street, Kettering,schools will only be available for those children who live town without holding the handlebars, at the same time has bought himself a cycle at a local sale.He paid onemore than a mile away.Those who live nearer will either doing their homework or reading thrillers.Theguinea for the model-a wonderful old penny-farthing. have to do their cycling after school hours. boys are greatly offended at the suggestion that theyIt may be a bit hard on the rider, are so keen on homework that they do it while cycling,but it isn't a bad idea to have a a thing no decent schoolboy would dream of doing.spare in the stable, just in case. 'The committee has decided to draw the attentionof local schoolmasters to their complaint. Yorkshire Dealer's Death THE death has occurred at the Successful Season age of 6z,of Mr.J.A. Bates,of x to, St.Sepulchre A. CLAYSON, of theLeicester ForestCycling Gate, Doncaster, who was one Club, has won the club's lasttime trial of theof the best-known cycle dealers season by covering the 25 miles int hour 4 minutes inSouth Yorkshire. He had 43 seconds and beating 27 other riders.Clayson has beenillfor some longtime. set up a record this season by winning every club event Mr. Bates, who had carried on a in which he has ridden, with just a single exception. cycle business in Doncaster for manyyears,wasa founder -

Conscientious member of the Doncaster A LDERMAN W. H. HENNESY, ofBristol, has Wheelers' Cycling Club, which designed from the town's Road Safety Council was formed in 1926. because he considers he is not fit to serve on such a council.He says he was once convicted of failing to Not So New observe a halt sign while he was cycling and he con-APETERBOROUGH con- siders that no one who has been convicted of a road stable who stopped a cyclist offence, however trifling, should put himself in a posi- andtoldhimhewouldbe tion to tell other road users how to behave. reportedforfailingto observe ahalt sign, was asked by the surprisedrider : " Isthis a Upset His Budget . new police order ? "The con- WHEN stopped in Peterborough and told he wouldstable wondered where the cyclist be reported for riding without alightacyclist had been hidden away all these told the constable :" You will only summon me for years, but managed to keep his riding without a li. They will only fine me k emotionsincheckadmirably. -and IhaveCr."'The magistrates later causeda The cyclistlater had to paya crisis in his financial affairs by fining him 305. and the 15s. fine. chairman commented :" We shall have to revise our tariff." North Lines Pioneer MR. GEORGE HENRY It's a Free Country ! LAY NE, of Brigg, foundet A DERBY soldier who appeared ata Huntingdon- andformermanaging-directot shire police court charged with cycling withoutof Messrs. G. Fl. Layne & Co. a" light appears to have strange ideas of the rights of Ltd.,motor engineers, etc., Brigg, who has died at the age of the individual.To the policeman who stopped him 81, was one of the first men tc he said : " If one cannot ride without lightsitisa pity."Another rider who was charged with a similarenter the cycle industry in North offence wrote to the magistrates saying :" I took every Lincolnshire.Just 6o years age precaution by riding on the footpath !" he openedasmall repair shot atWinterton, moving toBrig) a few years later, where he starte, Highway Code Criticised a factory employing half a dozer, l'HE recommendation of the Highway Code that men and producing his own cycle,Kenneth Horne and Richard Murdoch wish each other.1 fond Imotorists should not use headlights in built-up theGlanford. Some of these areas was criticised by the Nuneaton coroner at the cycles are still in existence to -day,farewell as they start a nine -week holiday from radio.The stars inquest on a cyclist who was struck by a car and killedone of them being now in Canadaof " Much Binding in the Marsh " visited the Smethwick works while on his way to his ambulance class.The motorist, inthe possessionofaformer who was driving with his side lights on, said he did not Briggschoolmaster,whotookof J. A. Phillips & Co., Ltd., recently to collect two brand new see the cyclist until after the accident and the first he it with him when he emigrased 35bicycles, guaranteed to stand up to anything, after their old machine knew was when he saw a light-later proved to be a years ago. had collapsed under the combined weight of the entire " Much cycle lamp-fly into the air.The coroner commented : Phillips, a subsidiary of Tube Investments, Ltd., " Properly dipped headlights dazzle no one.These How Will They Learn ? Binding " staff. accidents happen with sickening regularity and I shall (INCE there was a fond motherare sending 75 per cent. of their output for export, and to show their always use my headlights.No one can see very far s --f whorefused toletherappreciation Horne and Murdoch gave a show in the works canteen. December, 1947 THE CYCLIST 19 AroundtheWheelworld By ICARUS Arthur Whinnett Testimonial confirmed that he had handed up the drinkNorth Wales.It is thought that this is the only organised league club in Wales. DUDLEY DAYMOND, of4,Grange to a member of the Paris Cycle Team) ; that immediately the protest was lodged the twoRiders to Exchange Holiday Accommodation Court, 31, Christchurch Road, Streat-chief judges, L. Adams and J. Kain, made ham Hill, S.W.2, is anxious to obtain theevery effort to inform the event organiser, EARLY in 1948 the convlete race calendars names and addresses of all Southern RoadW. C. Rains, of the objection, in accordance of each country will be published, and Record Holders, together with past privatewith league rules, but considerable delay wasarrangements will be encouraged whereby the members and clubs -3939 ----in order to give unavoidablyincurredinmakingcontactriders who wish to takeaholiday abroad them the opportunity of subscribing toa owing to the assembled crowd. When con- may so arrange the holiday that it coincides testimonial to show their appreciation of thetact was made, W. C. Rains, L. Adams andwith particular events in which they wish to services rendered by Arthur Whinnett to J.Kain agreedthat the commentator, F.compete. cycling in general and to the S.R.R.A. in par-Guy,be instructedtoannounce that an British competitors going to France will be ticular.It is hoped to be able to make aobjection had been lodged against the Parisaccompanied by a_member of the French really worthwhile gift to Whinnett attheCycle Team and that the prizes were beingFederation, and French riders will be wel- 1948 S.R.R.A. dinner which will be held atpresented subject to protest, and this was comed to the homes of B.L.R.C. riders in the the " Windsor Castle," Victoria, on February done ;that the act of F. Guy in takingsame way when they come to Britain. 19th next. charge of the prize -giving ceremony was to Whinnett was responsible more than anybe deplored, but in view ofthe advanced Ladies'Events other man for the organisation of Frank stage of this ceremony at the time decision BOTH Federations encourage ladies' events Southall's records and Southall himself hashad been reached, no useful purpose would on road and track, and arrangements will statedon many occasionsthatalarge be served by stopping the ceremony in thebe made to include special programmes of measure of his success was due to Whinnett.presenceofGeorgeAllison,directorof international status during 1948.It is prob- I should like to add my own tribute to theArsenalFootballClub,TheMayorof great work which Arthur Whinnett has done. able that such an event will be staged to Weston -super -Mare,thePublicRelationsfollow the Grand Prix delaBastille,in He was, of course, secretary of the S.R.R.A.Officer of Weston -super -Mare, the Press andBattersea Park, on July 14th next, a French for over 20 years, relinquishing the job lastgeneral public and it was feared that such amale team having already been invited. year to Percy Huggett. belatedpublic announcement might even Ealing Resolution detract from the credit that was due to D. N.C.U.-R.T.T.C.Rift AT a special committee meeting of theJaggard, in the event of him being announced THE Annual Report of the NationalCom- as the winner ; that the instructions to com- mittee of the R.T.T.C. provides further Ealing Cyclist Club, the following reso-petitors governing the race, as laid down in lutions were passed unanimously: evidencethatthestrange" partnership " the third paragraph of the noticeissued tobetween these two bodiesisbreaking up. r.-That this meeting views with grave" competitors . and officials,"had been in-The row seems to have started in the early concern the action of the London Sectionfringed,thisnoticestatingquite clearly,part of this year when the N.C.U. virtually B.L.R.C. in nominating A. H. Clarke and R.viz., "Feeding. Riders must make their ownapproved the Paris to London race without Morbey as delegates to the meeting of thefeeding arrangements, and all feeds and drinksreference to the R.T:T.C., who banned its NationalExecutiveCommittee,B.L.R.C.,must be handed up in a 30o yards stretch ofmembers from taking, part init, but finally held at Birmingham on Octobr 11th androad on the outskirts of Weston leading upapproved it by a face-saving agreement. 12th, 1947, in view of the fact that these twoto the main road. This will be marked delegates were directly involved in an appeal The R.T.T.C. seems to be greatly upset withflags(approximategradient1-t6).because equipment used by some ofthe to be heard by that committee. Infringement will lead to disqualification." 2.-That the -Hon. Secretary write to the amateur writers was advertised in the French That in view of thisit was unanimouslyPress. We would remind the R.T.T.C., National Executive Committee registering aagreed that A. H. Clarke, H. Burville and protest against the decision permitting A. H. however, that it has no power to control' the R. Morbey be disqualified and that the' racemethods of another nation, and thatitis Clarke and R. Morbey to form part of thebe awarded to D. Jaggard, Dayton Cycles. committee that dealt with the appeal of these merely a domestic tribunal without inter- two riders against the judges' decision whichRoadster, Sprite and Sports national recognition, except by virtue of its disqualified them for infringing the feeding strange bed -partnershipwiththe N.C.U. PLEASING news announced by Dunlop isThe N.C.U. has now made a request that it regulations governing the Independent Road that the famous Dunlop Roadster, Dun- Race Championship, held recently at Wes- should be recognised as the sole controlling lop Sprite and Dunlop Sports cycle tyresbody in Great Britain for all forms of inter- ton -super -Mare. are now available in 26in. x IQin., 26in. x 3.-Also,thatthecompositionofthe Jain., 26in. x IZin., 26in. x ain., 28in. xnational cycle racing.This raises some vital National Executive Committee was not as',lin., 28in. x IZin., 28in. x On., 22in. xissues.It means, in effect, that the N.C.U. laid down in Rule 6 of the National Consti-'gin., 24in. x ain., and 24in. x IZin. (Road-could run races on an international basis in tutional Rules. ster); 26in. x I4in., and 26in. x 'gin. (Sports);this country, and as such races are not run 4.-That in view of the appeal being heard 26in. x twin., 26in. x tRin., and 27in. x in conformity with R.T.T.C.rules,it can under such irregular conditions, which left(Sprite).The quantities available arestillhardly be expected that the latter body will doubt on the integrity of Dennis laggard,limited, but are fairly distributed. agree. who has resigned from the B.L.R.C. in con- The request does, however, reveal that the sequence, we feel it will be in the interest ofTown -to -Town Mileages N.C.U., sprung intoactivitybythe un- the League as a whole ifthese facts are" TOWN - TO - TOWN MILEAGES,"doubtedsuccessoftheB.L.R.C.,isen- publicised. published at is. net (postage id.) bydeavouring to steal some of its thunder. The A meeting of B.L.R.C. officials also con-Iliffe and Sons, Ltd., size loin. (wide) byR.T.T.C. isnaturally invitingitsaffiliated vened recently to consider a verbal protest rain., folded in paper wallet size Ain. (wide)clubs to resist any such recognition.I do lodged by the manager of, the Dayton Cycleby Qin. not think that the N.C.U. is the proper body Team on the occasion of the Independent There are numerous occasions on whichto control road sport or any branch of it.It Road Race Championship held at Weston -the cyclist, either for business or pleasure,has no experience of such sport, since its super -Mare in September.It was stated: wants to know at a moment's notice the dis-activity has been entirely devoted to racing That the placing of the first four riderstance between particular towns. on closed circuits.It threw over time trial- was announced by F. Guy, the commentator, This at -a -glance mileage chart gives theing and road records fifty years ago.It before the judges had had an opportunity distancesbetween 77ofthemostim- exists to -day to administer the activities of a of confirming their decision on the placings ; portant towns in Great Britain. Distancesfewhundredtrack -racingcyclists. Its that Mr. F. S. Durman, manager of the Day-between nearly 300 other towns can quicklyofficials have been expressly forbiddento ton team, lodged a protest against the Parisbe obtained from a subsidiary table. have anything to do with road racing, and .cycle team immediately after the four leading The distances are those of recommended itsdeplorablyunsportsmanlikeactionin riders had finished, first verbally (and later R.A.C.routes ;and thecharthasbeenendeavouringtoget massedstartracing inwriting,letter 21/9/47, Weston -super -specially prepared by the R.A.C. for " Thestopped has done a great deal of harm to Mare) ;that Mr. Durman produced fiveAutocar." all forms of road sport.The N.C.U. is in witnesses confirming the infringement con- urgent need of reorganisation.Itshould cerned, which charged A. H. Clarke, H. North Wales Road Club get on, as I said at a recent public dinner, or Burville and R. Morbey with having taken above club is now representing theget out.Itis not wanted as a body, and a drink contrary to the regulations governingTHEB.L.R.C. in Wales.All cyclists in thehas long outlived its usefulness. Recognising the race, at a point apnroyamately five milesNorth Wales area should get into touch withthat it is dying as at present constituted, it is from the finish of the race (the motorist,Mr. J. P. Thomas, hon. sec., North Walestrying to horn in on a form of road sport who handed up the drink concerned, laterRoad Club, Tan-han Road, Old Colwyn,which it has steadily opposed. 20 THE CYCLIST DeCember, 1947 with the result that the gathering has gained a reputation and tradition, goodwill assets which count enormously when the year brings this fixture round. Far too many riders and officials seem to think they are the important Wayside Thoughts people at such functions ;nothing of the sort, it is the folk who make the ring round the track, for without them the others are less than nothing.If promoters By F.J. URRY would only realise that truth and act on it,I believe about training methods thanthe success of enclosed cycle racing would be enormously our old crude notions "ofimproved. riding as fast as we could until our knees knocked the It is Answered top rail; otherwise the busi-THE cry is still heard in the land that cycling is hard ness of racing on the road work, and that the delight in it is when you stop. is much as it was.What I There is a half truth in the latter phrase and none in the am specially happy aboutformer, always providing the exponent is fairly fit, has is the fact that the game has the right kind of bicycle and is using it correctly.I remained clean in the trueam getting into the sere and yellow, out of sympathy sporting sense of the term, with unnecessary hard work, nor seeking to add toil for there was a period whento life, yet I ride a bicycle daily because I like it, and the trade felt an inclination whenever opportunity offers roam into the country on to exploit it.But the good two wheels, taking from the change of scene and. the sense of clubmen, led by the exercise the joy that adds a sparkle to life and makes a lateF. T. Bidlake,over- man more glad to be alive. Having done this same thing came that phase, and for afor years, not as a matter of habit but through desire, it time made the purely club surely follows that the hard work slogan is utterly false event not only a racing fix- in the ears of the competent cyclist, and further, there ture but a happy social one. is no reason why any ordinary individual should not That was in the early years become such a rider.The hard work cries of the of the century, when motor- positively idle or utterlycareless folk have always cars were few and far be-annoyed me,firstlybecause they are untrue,and tween, and we could hold our secondly for the reason that the expression of such an Castle Acre eventson Saturday- after-opinion suggests I am a blithering idiot to remain a -Priory , noons and make the evening cyclist. Generally speaking Ifind the people who Norfolk-. of the day a chorus of clubtalk ignorantly on the subject of cycling possess very life. Isuppose every oldlittle knowledge of any game exceptasspectators. Port of the remains rider will regret the passingThey have grown physically idle, often careless of a of the crest Norman.. of those times, for the earlymeasure of decent muscular attention to their bodies, fortress and House morning event and the subsequent scattering of the and when they want to travel prefer to loll at ease and oi the Clunioc Monks clan on its private occasions lacks the joyousness of club thereby grow much older in activity and outlook than contact which made the purely club programme such they should.I have seen so many such degenerations delightful fixtures. There are, as always, compensations, that I would keep on cycling if for nothing else than PreaGhing the Gospel and the greatest of these is probably the fact that many its superlative exercise.But the delight in cycling and IN the early part of the yearhad a number of talkingmore young folk are now interested in this graceful andits grant of glorious horizons is linked with the factor engagements with RotaryClub audiences and comely sport. Anyhow, it is good to see the lads alongof exercise, that feeling of being alive and self-sufficient, expected that my insistence on the value ofcycling the road practising to acquire a speed which far outrunsthat high pleasure of exploration, the splendid enjoy- as a means of pleasantly sustaining the boy that is saidthe very best of our performances. There is no doubtment of food, and the quiet personal satisfaction that tolivein the heart ofeveryman would meet withthe game will go on, butI do wish the little quarrels the ending day has been well spent. Such indeed is the considerable opposition.It didn't ; rather the reverse,would cease and the blessings of peace return to the delight in cycling when you stop, when the'country inn for it seemed to gain the compliment that a man not great,clean sport of road racing. welcomes you, and the last thrill of a sleepy bird seems forced by circumstances to make cycling his main to light the evening star.Such then to me, in epitome, hobby possessed the wisdom to break down the common The Right Way is a day on tour, a day to be remembered and revered, convention that the pastime is something just " notAND talking of sport reminds me of the criticismswhen food is ambrosial and the last smoke the incense done ' when an individual reaches a certain status in recently launched regarding the sloppy runningof heaven. And some people would call this hard work I life.. Now, these Rotary people are hard-headed businessof sports meetings.I do not think there is anythingWell, it takes all sorts to make a world, but I prefer men who for the main part have forgotten the valuesso annoying to the average spectator at a sports gather-health and my simple image of enjoyment rather than a ing than to be kept waiting from race to race, or fail totravelling cage with a cocktailbar at the end of the knew them.One bicycle to them is as another, andunderstand the type of competition because thef pro-journey. orie cyclist just a unit in a crowd that sometimes annoys gramme is faulty in description.There is no excuse themat'knocking -off "times on week -days,and for this kind of shortcoming, and it does untold damage That Absurdity - occasionally at week -ends when returning hastily from to an entertainment that otherwise deserves afar IWANT to help break down that state of mind people their motor trips.So in telling these people -what thegreater measure of public support.I was at a race are prone to accept-say . what you will-that if bicycle has meant to them in that happiness and con- meeting some weeks ago which Went with a swing you are a cyclist it automatically follows your status in venience of their own employees, and stressing thefrom start to finish and quite charmed the crowd ofthe social scale is thereby lowered. That very persistent certain truth that they too would be better and fitter9,000 spectators.It started on time, was never morementality has not been derived from cycling but from people if they rode for the' sheer joy, exercise and than a couple of minutes down on schedule, and whenmotoring, and itispart of the ostentation concerned individual freedom thatiscycling's special virtues, that happened the responsible officialsgingered up with engine travel too frequently observable, which is a and-please forgivethe egotism-presenting myselfeveryone concerned, with the result that the last event pity, for motoring as well as cycling.Naturally I as a decent example of my own test, I seemed to persuade of the day was off to the tick.Now, that meeting has consider 'thewell-equippedcyclististhehappier my audience that there was much more in the gamebeen successfully undertaken for twenty-five years, has individual as well as the more comely, and the question than they had given it the credit for possessing.I do always made a fair, and oftena handsome, profit ; of the size of his bank balance has nothing whatever not expect to gain recruits from among these dapperdespite the fact that on more than half the occasions theto do with the matter.Occasionally I meet the patron- business people-that would bea miracle-butI weather has been distinctlyunfavourable. Why ? age- of the motorist and quietly but firmly reverse the sincerely believe there is a high value in the matter of Because its public know the promoters' first considera- position, as he seesit. Why should the possession instruction that cycling is not " hard work " nor the tionis for them and their interest and convenience, of a car be the sign of superiority ?Nearly all the travel travel resort of the purely impecunious. My object is values are on the side of the cyclist, for the only one and alWtws has been to raise the status of the pastime, the motorist has in exeelsis is speed, and that to my way to make people realise that this geared walking is the of thinking is often, indeed mostly, a deterrent to the best thing that has evolved in the way of games for a abiding virtues of roaming. Ilove the things that hundred years, because it can be played at the tempo cycling has given me and am indeed thankful for them ; to suit every age and condition, in company or alone. but I have no desire to encourage a feeling of superiority And its silence is indeed golden, its freshness revived in me because I think my way is the best. Why should with every dawn, its exercise ranging from the strenuous the motorist ?Probably most of them would disclaim to the gentle, and its healthiness a positive measure of such an attitude of mind if they were to argue the national value. Those are facts which cannot be denied, subject, as indeed most of them have when contacts and underlying them are the glories of observation, of this nature have been made ;but the notion unthink- scent, penetration and the loveliness of a land which, ingly exists and it needs eradicating before the two it seems to me, can only be assessed atits true value methods of travel can hope to be sympathetic.I would by the indiVidual who has used his physical powers to be the last to persuade anyone to ride a bicycle without see it.Yes, I have been surprised to find the little a shadow of conviction showing on their part, for I lessons going home so easily, and if this older generation know the cyclist of necessity is too often a critic of the will but encourage the younger to retain the manliness pastime.I can only say what cycling has given me of cyclingfortheirhealth andpleasure, however and is still giving, I can only imagine my activity and supreme they may become in the affairs of the world, good health result from my 8,000 miles of riding per the pastime will gain something, but never as much annum, and both of them are too precious in possession as the individuals who have the very common sense for me to lightly drop. The car is useful on occasions to remain cyclists all the length of their active lives. when there are urgent things to do, but I don't like it. for I can only glimpse the country, not see or smell or taste it, and a couple of hours of such journeying makes Discipline and Contentment me feel like perished elastic-all the spring gone out of PROWLING round the lesser roads running circularly me.Yes,I'd rather be an ancient cyclist with a decent a dozen or more miles from the city centre the pride in my " grizzled youth " than a solid gentleman other evening, I was met or overtaken by some twenty in a saloon, accepting his years without protesting that young men, in singles and couples, evidently intent on the boyinhisheartisstillalive.I can under- training, and I was reminded of the words of a very old stand that man and his way of life without feeling friend of my father's, who, happening to be at home superior ;he has chosen it and it'shis affair ;but when I had returned from just such a jaunt in 189q, why on earth he should seek to patronise me-as he so remarked what an excellent discipline and self-sacrifice it was for a young man to undertake, far better than frequently does-is one of those mysteries still existing wasting time hanging round street corners.At that in democracy which makes a man despair of ever discov- moment I wondered precisely what the old gentleman ering the shifting meaning of that much abused word. meant, for it did not occur to me there was any degree of self-sacrifice in the fierce joy of a training ride. PLANT ENGINEER'S POCKET -BOOK Now I know ; and as these young folk met and passed me, often flinging an evening greeting,itstruck me 6/-by post6/6 how little the old game has altered down the years. From GEORGE NEWNES, LTD. e- Road surfaces and bicycle building have improved, Jeff Scherens, the Belgian professional sprint (Itook Dent.), there are many more expert riders in the .competitive Tower House, Southampton Street, Strand, W.C.2. ranks, 'and 'the lads and lassies know a good deal more ' cycling champion of the world. December 1947 THE CYCLIST 21 APEX The World Famous 'SUPERLITE'BAILEY'S CELLULOID PUMP `SUPER' IS x" BLACK PUMP IS x BLACK Thick Celluloid "No other tyre Beautifully Polished Steel Lined Celluloid Covered Light of Weight Lining is Solid drawn but of cartridge fashion,the ends will really satisfy robust construction being solid with the barrel 'SUPERLITE' ISin. Cannot warp nor leak. CELLULOID (withr BAILEY'S'SUPER ' (Steel solid drawn brassar lined and Celluloid $PaoE= plunger tube) each covered) ISin. each5/6 war>-=1 me now" 'LASTWEL' CELLULOID BRASS PUMP, Nickel 1'1 (withsteel split Plated or Black enamelled v.,an plunger tube) ISin.4/6 (with steel split each plunger tube) each 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 AP EX INFLATOR Co. Ltd. ALDRIDGE ROAD, PERRY BARR, BIRMINGHAM 22B Fibrax) and get there safely! In any emergency Fibrax Brake Blocks will always pull you up.They are made of material specially processed to give the maximum braking efficiency. Highly resistant to wear.Production limited in these days, but you can depend on your dealer to do his best to supply you. FIBRAX LTD., 2 TUDOR STREET, LONDON, E.C.4. YOU Rubber dipped and insulated cord body and deep tread for long life and safe riding.Tubes are can become a first-class circular-moulded-tailor madetofitwithout RADIO ENGINEER wrinkling-rubber-base valve prevents air leaks. We arespecialistsinHome -Study CoursesinRadioEngineering, Servicing, Transmission, Television, Mathematics and Radio Calculations. Post coupon now for free booklet T. & C. RADIO COLLEGE, andlearn how you can qualify NORTH ROAD, PARKSTONE, DORSET. for well -paid employment or n Please send me freedetailsof your Home -Study profitable spare - Courses in Mathematics, Radio and Television. .time work. 11 Name BEST TODAYre * STILL sto BETTER TOMORROW (Pastcoupon in unsealed envelope Address -1d.stamp.) I M.35 aml .1=1 now vo. =NM imms wow mire 22 THE CYCLIST December, 1947

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$3202 December, 1947 THE CYCLIST 23

CYCLORAMA H \ALEY record of work during the war years in con- nection with such matters as National Sav- ings, Salvage and Production.He is one of the hardest workers I know-forthright in his manner and with a background of experi- ence whichIhave found,personally,of enormous help on committees.I wish him good luck in his latest activity.

Sylvan Staffordshire yES-sylvan ! Foritisa myth to imagine thatallof. Staffordshireis grimy and dirty. I know the county well, and while admitting that there are many sorry industrial scars in the Potteries and in the Black Country, one should not forget that there isa belt between-the lush and green Trent Valley, around Lichfield, which is lovely indeed.What happy hours I have ,u/a spent at little Alrewas, fishing in the Trent. What sweet and unspoiled villages there are //y .7/.1/ fltly(7 "7751/ around Burton -on -Trent. Here isa fine q-oueinn cycling area which I commend to all riders "r CkertSeq who would see some new angle of England's beauty.There is Abbots' Bromley, where, Surrey followed this sane advice.Not only trafficevery September, they still indulge in the A pretty little inn on the relief would result, but health would improve centuries -old " Horned Dance "-in which slope of St Amies Hill %lilt, -and whilst I cannot claim to cycle to work twelvemen, bedeckedwithantlersand its fine old tree dillitfull now, for many years in the provinces I didgreenery, dance to some ancient tunes. The foliage, but needi.kciA tittle so, and well do I remember how freshIorigin of the dance islost in the mists of dret felt on arriving at the office. antiquity, but the ceremony is most inter- esting.And do not forget that Derbyshire is only just over the border, and that one Trees may meander by the silvery River Dove, Winter Preparations CYCLING recently with some young folk NOT a bad plan, now that the dark nights with whom I fell in near Barnet, the socredtoalltimetoIzaak Walton and are here and we are thinking of wintertalk turned on to the subject of trees, andCharles Cotton. riding, to give the bike a good overhaul.ItI was a little grieved at the ignorance shown is a job which many cyclists neglect, to theabout our familiar trees-these young peopleThe Incurable Habit ! detriment of their winter riding-which, ifcould, of course, recognise an oak and an IHEARD of an old Dunlop friend the the machine is in good trim, can be so enjoy-ash-but there their knowledge apparently other day --R. H. Bagnall, with whom I able. In fact, some of my very happiest ended.The alder, the hornbeam and theworked at Aston Cross in1913. He is cycling memories are memories of winterwych elm baffled them. Now it seems aseventy-seven, and cycles thirty miles a day . rides:those good daysinJanuary whenstrange thing that the roads are iron hard, and the big redin this well -treed sun islike a ballin the heavens, and the rime is on the hedges, and the air is crispland, where we have suchlovely varieties, 6'd st. and keen.Then itis good to get out intothere should be such the lanes and see the beauty of the starkignorance in identify- trees, with their bare branches stretched out ing the different like lean arms.And on such days Motherspecies.And how it Nature is not dead-the robin still sings onadds to the joys of a ' the farm -yard gate, and over the fields thecountry ramble if one ;lapwings cry as they forage for food in thecan recogniseeach hard rutted earth. But do get the bike intreeandgivesome good running order now ! studytoitshabits, form and growth. A VeryOldCyclingClub Thereareseveral ,THESouthgate-founded,Ibelieveinsimpleandexcellent the year 1882, has had a .long andlittle books published Iconsistent record of good performances. Thison trees, and perhaps yearits annual dinner is going to be heldthe best for the be-

at Beale's Restaurant, in Holloway, and Iginneris" The Ob- have been honoured by being invitedtoserver's Book of respond to the toast of " The Visitors "-British Trees "-pub- 4 and very gladly did I accept the kindly invi-lished byFrederick tation extended to me.From past experi-Warne & Company. Millers Dale, enceI know how enjoyable cycling club" Treestudy "goes be,byskire. dinners and other functions can be.And, well with cycling, The P.ver Wye v. a loves '$evenn these austerity days. I know that s Ike dale twit and I commend the east of Luxton. this old club will put on a fine " do."Isubjecttoallwho Dole forward to a happy evening. love the shady wood- lands, the forest glade and the thickets andon three days a week!No wonder that my The Happy Cyclist coppices where the hawthorns and hazelsinformant about him reported that he was IEXPECT that many readers saw thatgrow. "Male and hearty "!There is nothing like enthusiastic letter in the national Press cycling for keeping the " old 'uns "fit ! from a cyclist Who explained how he rode to" Works Relations Drive " and from his work each day, some ten miles ISEE that my friend Noel Brealey, the morning and evening, and thus escaped the advertising manager of the B.S.A. Com- GEARS AND GEAR CUTTING . ever-increasing trials and turmoil of Londonpany, is prominent in connection with the 'traffic-thecrushesin theTubes-the" drive " being made by the Birmingham Edited by F. J. Camm. " battles " to board the 'buses.This riderPublicity Club regarding " production propa- Price6s. from allBooksellers or6s.6d.by extolled the virtues of cycling and made a ganda " in factories, and is closely associated post from George Newnes, Ltd., (Book Dept.), Tower House, Southampton Street, London, els great plea for more folk to cycle to and fromwith the approach to the Government by the W.C.2. ' their work.It would be a good thing if we Birmingham Club. Noel has a very fine 24 THE CYCLIST December, 1947 The Food Question MyPoint of View T CERTAINLY lived on the fat of the land, and I anow know where togo whenthefoodcuts, threatenedatthe time of writing,actually occur ! .1/ Roads and One day I managed to put away five eggs.Every day I had, for breakfast, home -cured bacon and egg. I By " WAYFARER" Conditions had substantial meals in the evenings.There seemed e - to be plenty of everything-yes !even sugar.At an / FOUNDtheroads, isolated hotel up in the Shropshire hills I had a magnifi- practieMlye v ery- cent lunch of hot soup (delicious), meat and vegetables, where, in satisfactory condi- fruittart and cream, cheese, " tion,at leastfromthe etc. Bread and butter abounded . .. and it was a bit of a drop to come back q cycling point of view, which home to bread and " marg " IAt a first-class hotel, siris theonlyonewhich in a place which shall be nameless, I obtained such a A concerns me.The worstpoor lunch thatIwas constrained to write to the -443! - piece of road I struck wasproprietors, who run a group, or chain, of such hotels. the four -mile climb from I complained of the soup, which was merely coloured Newtown to Dolfor.This water.I suggested that the main course-bully beef hadrecentlybeentar - (of which I happen to be very fond), with sausage -roll paintedand treatedwith as an alternative-was lacking in imagination, which granite chippings, theremark applied also to the sweets-stewed figs and " resultant surface being of acustard, or what the waiter called " milk " pudding. very coarse texture.It was I conceded that the coffee was excellent. uncomfortabletocycle On the over, and yet, though I amother hand, I thought that the kitchen staff was quite a poor hill -climber,I rodeout of control, judging by the " noises off " which most of that long and rather were clearly heard in the dining -room.The prompt Newo,tc. reply from the proprietors justified my complaint, wearyslope. InMont-and I was offered (but did not accept) the return of Sk,e4 h ganomersh ices I my money.It appeared that the local management pictoreic,e ruInS of - had proved to be unsatisfactory and was under notice :Lecofficialcini(a:which7h rent st.ding to leave.Thus everything-including the complete 1/ attention)of lay the fiver Wei near Riley dumpinglack of imagination-was accounted for. loadsofthesechippings I had two other indifferent lunches atplaces far ontheroadsideswithout less classy than the hotel above -mentioned, and they anyretainingdevice,withtheresultthattheno* go on my black -list.My final lunch of the tour material spills over on the road, setting up dangerouswas in a farmhouse, where, in the absence of meat,I conditions for cyclists and others. A cyclist driven into managed (!) with a couple of eggs, bread and butter, Misconception Piled High the gutter by the press of traffic (hard to imagine in etc., at a cost of 3s., which I thought excessive.My Montgomeryshire !) would sustain a nasty fall if he wereplain tea that day cost me zs., which was also an extor- A BROTHER-ANFIELDER whom Ihave just compelled to negotiate this loose stuff. tion.On the whole, however, I ant more than satisfied met on tour-it was interesting to note that our Another point perhaps worthy of mention is that with my experiences as to food and costs. last meeting was on Crib Goch (Snowdon) some zo in all these miles of travel I observed only two cases of years ago-told me that he was " on his own " because bad motor driving.The one which concerned me was his intended companion funked the holiday at the lastthat of a big car pressing forward on a narrow road at moment.The reasons, threefold, were most interest- Fairbourne and then having to pull up because of anWrong Lightness ing.There was the difficulty of obtaining accommoda-approaching car, thus making things awkward for me. tion.There was the likelihood of starving to death The other case was that of a Service vehicle beingWHEN ridingwith aboycyclist-acomplete because ofthe foodposition.There wasallthe driven downhill on the wrong side of the road, to the stranger-the other day he told me that he was discomfortto be derived 'from overcrowded roads.grave inconvenience of a private car which was met onusing a borrowed machine, his own being in " dry Misconception piled on misconception I a corner.That is not a bad record for over 600 miles ! dock."It appeared that he had had to apply his front I compared notes with my friend, whom I saw twice brakerathersuddenlyinordertoavoidhitting afterwards,andhisexperience agreed withmine. something and the strain caused his front forksto There was no difficulty in obtaining accommodation.No Relaxation recede. I have always advocated light bicycles, but As it happened, mine was booked in advance, and I it seems to me that it is almost criminal on the part of encountered no problems. My friend was chancingLVEN those of us who have 'been cluttering up thea builder so to cut down weight that the forks will not his arm, and he, too, met no difficulties.We both 2-4 roads for many years are not immune from thetake a perfectly natural strain.That, surely, is wrong- did very well as regards roadside meals, which wereoccasional need of a reminder that eternal vigilance isvery wrong-lightness. easily obtained,and,mainly,of high quality andthe price of safety.Let me amplify the point. On a satisfying abundance.(More of this anon.) We did recent Sunday night I was making my way through a not find the " overcrowded roads."On this point complicatedlane -route with which constant useis I would say that, if all the traffic seen during the nine gradually creating a sense of familiarity.Nevertheless, Sixth Sense days I was on holiday had been crammed into one half - a proffered opportunity to go astray was accepted, and, T RECALL that one day, a few years ago, when cycling day, there would still have been no congestion.The quickly failing to recognise my surroundings, I turned A home from business on a blustery afternoon my scarcity of traffic, rather than its frequency, was reallyback and put myself right. A few moments later, riding attention was attracted to a bicycle standing at the noteworthy.Thus my friend's friend missed a jollyup the stem of a T -piece, the existence of which had kerb." That machine," I said, " may be blown over." fine trip, in perfect weather, solely through his imagin- been completely forgotten,I suddenly found myselfI took evasive action " in case," and, as it happened, ings as to the position of affairs along the road.'That is heading straight for a roadside bank and hedge.By my foreboding was fulfilled just as I rode by.Fortu- what one must expect in return for swallowing all one dint of lightning evasive action, consisting of furious nately, my sixth sense had impelled me to leave a safe hears about food and accommodation and for judgingback-pedalling and urgent braking, I safely made themargin. Otherwise the standing bicycle would have trafficconditions from our citystreets during the acute right-hand turn, and went on my way in safety, fallen against me, with the possibility of unpleasant business." rush " hours.One hardly expects a cyclistenriched by a reminder of the need for constant vigilance. results.Similarly, last Sunday morning (asI write), however, t be so misled. It is quite clear that there must never be any relaxation. itstruck me that one of the crew of a stationary milk -cart on the left-handside of the road might descend on the right-hand side and dash across the Touring Plan Joint Concern road. How correct was my intuition !A boy jumped ON this holiday I followed my usual touring plan.MAY I suggest, for the consideration of allreaders, into the road, started to run, changed his mind and Brief study of the map would tell me where to go, that safety on the roads is the joint concern ofreturned to the cart, quite oblivious of the dangers ho andI would set forth on a strippedbicycle for myeverybody who travels along the King's Highway. was creating for himself and others.Fortunately, I was day's ride, satisfied that the mileage, whatever it was,There can be no unilateral plan here ;there can beready for his gyrations, though these, in the circum- was well within my compass.It is to be supposed that no " leaving it to George." On the other hand, there stances, were not too easy for me to circumvent. The the practised eye, looking at the map, can tell at amust exist-there must be set up (and be maintained), sixthsenseiscultivatedas the result of years of glance, more or less, that the distance is right.On where it does not already exist-an unofficial, automatic, experience.It is well worth nurturing. one day, however, I did not quite follow this plan, and and too per cent. partnership between pedestrian and thought for one gaudy moment that I had " kicked a motorist, between cyclist and lorry driver, between bus brick." Mybrother-Anfielder,above -mentioned, driver and the youthful population, in the sacred cause of Distance if Required who was staying in a farm adjacent to mine, called safety,thatpartnership functioninginatwo-way for me at breakfast -time, and we decided that we would (and; indeed, in an every -way) manner. two recent Sunday afternoons I had my tea in spend part of the day together.He was then _hound It takes two to make a quarrel.Similarly, and as a ,--a village about three miles away from thatin for the North Wales coast, and I said that I would gogeneral rule, it takes two to make an accident.Thuswhich I had obtained my lunch.On each occasion a bit of the way with him.The " bit " lasted untilthe avoidance of accidents is the joint concern of all.I travelled zt miles between the two meals, enjoying aftertea, when our routes separated.It was thenExperience shows that most of the accidents which to the full the beautiful weather conditions which thatI sustained a mild shock.I had put up a fair happen arc avoidable, and unnecessary.It is not tooprevailed, and making every useof theseclusion mileage and had a decent distance still to do, when amuch to say that many of them are manufactured. presented by lane routes.There was a little repetition sign -post told me thatit was 21miles to Harlech. Any ordinary observer, watching the roads, can seein the two journeys, but for the most part the second I did not doubt the statement, which meant that I trouble being built up. With co-operation on a wholesalejaunt varied considerably from the first.I was not out was doing at least an 8o -mile jaunt-rather more thanscale, accidents could be reduced to a minimum. after miles :I just wanted to employ the afternoon I desired to achieve in mid -Wales, on a hot day. The hours advantageously and pleasantly-and to prove that time it took me to reach Harlech suggested that I am to have two consecutive meals soclosetogether a perfectly marvellous rider-with the alternative that geographically is not so silly as it looks Thus, when the signpost was woefully inaccurate.The latter, -of Unpleasant Sound we want to have a meal within walking distance of course, is the explanation, and I have since taken steps ONE of the most unpleasant and unwelcome soundshome, or of the spot where the previous meal has been to have the information put right. which can assail the ears of a cyclistis the sharptaken, itis advisable to remember the possibility of When I reached home and reckoned out my mileage " crack " which denotes the bursting of a tyre.Twice, " making a ride of it."The guest-house on your -cyclometer-recorded-IfoundthatIhaddone recently, within a few days, I heard this sinister note, very doorstep, or a couple of fields away, can quite 625 miles, or practically 70 miles a day, and that without though on neither occasion was I personally concerned.readily provide you with a journey of 20 or 3o miles- trying.Had, I been out for miles, I would have made Nevertheless I felt very sympathetic towards the cyclistsif you are so minded.Personally, I am very keen on a much earlier start than my usual was a.m. involved. these wayward jaunts.

Published about the 30th of each month by GEORGE NEWNES, LIMITED. Tower Hciuse, 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. This coupon is available until December 31st, New Zealand-Gordon & Gotch (Aisle). Ltd. Sole Agents for South Africa-Central News Agency, Ltd. Subscription Rates (including postage) :Inland, 10s. cal. per annum. Abroad, 10s. per annum. Canada, 105. per annum. Registered at the G.P.O. 1947, and must be attached to all letters contain. for transmission by Canadian Magazine Post. ing queries, together with 3 penny stamps.A CONDITIONS OP SALE AND SUPPLY :This periodical is sold subject to the following conditions, namely, that it shall . stamped. addressed envelop: must also be enclosed. not, without the written consent of the publishers first given, be lent, re -sold, hired out or otherwise disposed of by way of Trade except at the full retail price of 9d. :and that it shall not be lent, re -sold,' hired out or otherwise disposed of in a Practical Mechanics December, 1947 Mutilated condition or in any unauthorised cover by way of Trade'or affixed to or as part of any publication or advertising, literary or pictorial matter. whatsoever. 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Will MINIATURE PETROL ENGINESfor buzzer Temporary address 49,NorthStreet, TWO -VALVE (Batt.) ... supply light in bedroom or PORTSLADE, BRIGHTON. Aeroplanes, Boats and Race Cars. ...2/6 larder, etc. PRICE V, Posted. THREE -VALVE Ditto. P.P. ...26 Send 3d. for Pg. A.C. 3) WATT. Fine Power ...2,6 BELLS, for use with either the 8 WATT. A.C.P. -P. Neg. F./B. Above or bait ies, 6/-. Posted. 2/6 PRECISION CUT -THREAD 8 WATT Ditto, A.C./D.C...... 3,6 B.A. SCREWS Stamp for Full List and with Order. SOLDERING IRONS - We are now able tosupply from stock COMPONENTS AVAILABLE. AdjustableBit, all parts replaceable and folly a range of Brass and SteelScrews, guaranteed.2001250 v., 60 watts,9/8 ; 130watts, L. ORMOND SPARKS (M), 12/6, post 6d. Small Soldering Irons,for use roundhead, cheesehead,countersunk, on gas,1/4. Post4d. Resin cored solder for easy etc.,also Nuts and Washers, allof 9, Phoebeth Road, Brockle), S.E.4 soldering,6d,packets, or lib, reds, EV-,Postage precision make suitable for instrument ('Phone :Lee Green 0220.) extra. work, engineers and model makers. PERFECT PASTIMES FOR (These products shouid not be confused PLEAS LIREAND PROFIT with cheaper " rolled -thread " screws.) Crinothene-Cel luloseAcetate-Parch- Ex-R.A.F. TELEPHONE SETS,comprising hand generator, bell, relay, morse key, Lis13 oat appliattion. ment-Plastics-Larnpshade Frames and Patterns -Raffia -Plastic Leather -Toys JUBILEE w"m°Rf"HOSE CLIPS signal lamp.'All necessary jacks and Also Rack and Pinion, Gearing, etc. Models -Materials,tools andfittings Patent - switches. Contained in a strong metal case Spirit Levels for Instruments. for Craftsthat aredifferent. with circuit diagram.25/-each, carr.2/6; The long -life 47/6pair,cart.2/6. Telephone hand SendII-for copyof theMagazine clip with the generator,withhandle,9/6,post1/6. SPENCER COMPONENTS CRAFTWORKER. (includes full price lists) ever -tight Bell, 4/6, post6d. 22 CAROLINE STREET grip HO MECRAFTS (Dept. 2),The BIRMINGHAM 3 Broadway, Broadstairs, Kent. TheBest Known Hand Microphones, with snitchin handle For and lead,3,6,post6d. Radiator Joints, ADANA PRINTING MACHINES TheInstituteofPracticalRadio Air, Oil and Print in the odd hours with an Engineers have available Home Study Water Hose reconditioned and in good Courses covering elementary, Joints Headphones, Adana -still the most absorbing theoretical,mathematical,practical order,5/6a pair, post6d.(better quality, of crafts.No. 1 11, and laboratory tuition in radio and We guarantee a 7/6 iv). These 'phones and mikes can Machine 24.10.0. No.2 a S 'Machine 89.15.0. television engineering the textis Tight Joint be used with telephone sets above. Will payforitself suitable coaching matter for I.P.R.E. Service entry and progressive exams. L.ROBINSON & Co in a month or two. tuitionary fees at pre-war rates -are Send stampforillus- moderate.The Syllabus of Instruc- 25, London New Headphones, 10/-a pair, post6d. trated foldertoDept. tional Text may be obtained,post Chambers, Balanced armature type (very sensitive), P.111.9, Adana (Printing Machines),Ltd.,15/18, ChurchSt., free, from the Secretary, 20, Fairfield GILLINGHAM, KENT 15/-a pair, post6d.NewSingle Earpieces, Road, Crouch End, N.8. Twickenham. Middx. 3{6.-Bal. armature type;6/-,post4d. a pair, post3d. (£4 Maskperiynoguse Headphone cords, 1/- PLANS-Vosper motor torpedo, boat. BOOKS: - per 100). Replacement bandsfor head - Two sheets giving every detail to build G.W.R. Nameplates ... Phones. 1/-, post4d. ($4per 100).Wire 36in. model.A splendid job.12/10 our Universalwiti7 SPRING WINDER bands, '6d.per pair(£2per 100).Rotary post paid. Cargo Passenger liner. Two KanniZo&RPLOV :S. t:- Transformers,12v. input in sound -proof sheets giving every detail to build 36in. Complete with 5 " Two Rail Electrification "..: ... 3(6- etc.,will also model of a beautiful merchant ship. " Rail & Platform Plans. No. 1 " 5/- cabinet, for Car Radio, 12/10 post paid. Really new. Plans " British Railway Stations Illus." 314 light 2.25w. lamps in series,22;6each, to build 28in. elastic driven long dura- diff-gauge Wires.£2 13 0 carr. 2"9. tion speed boat. 4/9 post paid. LINESIDE BUILDING KITS : List 2d. 246, High Street, 00 T. FITTON (Model Specialist), 4 Ann Footbridge Terrace, Norwich Road, E. Derchani, Harlesden, Windmill ...... 2/6 - Rola Sin. P.M. Loudspeakerand cabinet Norfolk. Signal Cabin ... 4/- - BULLS N. W.1©. . Loco Shed ... 7/6 - with volume control, £1, post 1/6. Shops and Flats 8/6 - " PIGMY" ELECTRIC MOTORS Country Station ... 10/- - BURALUMIN Low voltage., reversing for models.Use Pea Lamps. 5v. min. screw s.c.6d. each AND ALUMINIUM SHEETS the famous "PIGMY" motor for your Boats, METERS, 600mja.,3in.uic.,15/- Cars, etc., the most powerful motor obtain- Postage extra." 00 " or " 0 " Parts List lie.,in/c.,11/- 2.3 Duralumin 36 in. x 24in., 7/- 3d. per post. D/r 40/120 ni/a., 24S.W.G. 48in. x 36in., 12/- able.Weight 91 ozs., 21in. x 2lin. x liin. ap,.2in.,m Thermo coupled, 4/- ;20 amp., 72in. x 36in., 15/-. 2 to24volts.Price 25/-.Send21d. TYLDESLEY & HOLBROOK (M.E.T.A.) 7/6.;15 volt, 2fin., in/c.,12/6 ; Aluminium. In- sheets up to 6ft. x aft. for leaflet. 109, DEANSGATE, MANCHESTER 3 :30 atop., flin., Ind Switchboard mounting, 20 S.W.G. 1110d. per sq. ft. Ex -Gov. Motors, 24150v.A.C./D.C., 3lin. x 35/-;6,000v. 3fin., mic,£3/10/.. All On all above add 2d. per sq. ft. carriage. 21in. Ball Bearings, 25/-.12,24v. D.C. Ball. Inquiries invited for various sections. Bearings, 21in. x liin. x 12:8. With THE WORLD'S GREATEST BOOKSHOP postage extra. 4011 worm gear, 18'8.Worm gears, 10/1: COMPETITION CARS, LTD., The case, lin. x Din. x lin..8r-. Satisfaction SEND Id.S.A.E. FOR ILLUSTRATED 01(1 :Battings, Nayland. Nr. Colches- guaranteed. -E.M.Co.120, Torrington ter. Essex.Tel. Wayland 334. LISTB.P.OF USEFUL ELECTRICAL Avenue. Coventry. CFORBOOKS 4 ACCESSORIES. Money refunded if not Free Electricity from the Wind for Ydur New and secondhand Books onevery subject completely satisfied.Letters only. Please RATCHET & REVOLUTION Radio, Workshop, or Bungalow. WE BUYBOOKS, TOO includepostage;anyexcesswillbe COMPACT WIND -CHARGER TURN- I1e-125, CHARING CROSS ROAD, refunded. COUNTERS TABLES(tofitany Car Dynamo) LONDON, W.C.2. Completewith all partsrequired. Gerrard 5660 (16 lines). Open 9-6 (inc. Sat.) Askfor EASILY MADE atverylow cost from Leaflet No.18/5 quickly obtainedparts. HIGHSTONEUTILITIES Speed up to DIAGRAMS and INSTRUCTIONS, 216 6,000 r.p.m. per set NEW Machinery. -ElectricMotors, 58, New Wanstead, London BandSaws,Drilling Machine, Pumps, B. & F. CARTER J. Maker,22, Ditton Road, Surbiton, Grinders, Welders,etc. -John P.Steel, E. II 8eCo.Ltd., Bolton 5 Surrey Bingley. One of the following Courses taken at home in your " PRACTICAL ENGINEERING "said- spare time can definitely be the means of securing We recommend all readers interested in improving their position substantial promotion in your present calling, or entryto apply for a copy of this valuable book." Success in

into a more congenial career with better prospects. Engineering"isnot a pamphlet.Itis a 132 -page book, containing valuable and vital information on all branches of ENGINEERING, AERO, ETC._ engineering.. . . There are many engaged in engineering who Plastic-Radio-Aero Engines-AircraftDesign-owe their success to -The National Institute of Engineering. Welding-Aerodynamics-Electrical Engineering-The FREE GUIDE explains : Television-Electric Wiring-Talking Picture Work Openings, prospects,salaries,'etc.,in Draughts- -Generation and Supply-Works Management- manship, Inspection, and opportunities in all other

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