4111 ty ractical mechanics - world radio history

A SIMPLE MAGNETIC RECORDER.4111 TY

1111011.10P

RACTICALMECHANICS

EDITOR_:-f_.J.CAMM

JUNE 1951

PRINCIPAL CONTENTS

PRINCIPLES OF ULTRASONICS RADIO CONTROL OF MECHANISMS WORLD OF MODELSPLASTER PRODUCTION A TRIP BY FLYING BOAT QUERIES AND ENQUIRIESA ONE -INCH MICROMETER BUILDING ALUMINIUM OATS CYCLIST SECTION

When / want a Cl/P I turn to

TERRY'S(the Spiting people)

I go to TERRY'S for all kinds of CLIPS-steel,bronze, stainless, etc. When I want a clip made tospecification, Terry's Research Department is a bighelp in the matter of design (Terry's with 96 years'experience should know a thing or two !)

Nos. 8o and 81 comefrom r to 2" from stock.No. 300, an excep-tionally good drawingboard clip, costs g/- adoz. (inc. p.t.) fromstock.

Want to know all about springs?

Here is the most comprehensivetext - book on springs in existence.

No. 80

Sole Makers: HERBERT TERRY & SONS, LTD., REDDITCH London Birmingham Manchester

HT4F

253June, 1951 NEWNES PRACTICAL MECHANICS

Tool Bargains ! !Now is the time to buy your tools ; those offered beloware of the best quality, fully guaranteed, free of purchase

tax, and available for immediate delivery.

Best quality double pinion hand drills, lin. capacity, 171- ; sets of

cramp heads, 816 set ; 6in. jaw woodwork vices, steel screw, 13/6 ;6in. combination wood and metalwork vice, 1216 ; Record " Imp "engineers' table vice, 21in. jaws, 211- ; Record sash cramps, 24in.1816 ; 30in. 191- ; 36in. 1916 ; 48in. 2016. Record adjustable smoothplanes, No. 04, 3016; 041, 3516 ; iron jack planes 05, 3716 ; 051,

421-. Sets of 6 carpenter chisels, in. to lin., 1616 set ; carpenters'expanding bits, a complete set of bits in one, -1in. to 11in., 1216 ;gin. to 3in., 1719 ; Fin. ',Black and Decker utility electric drills,151101- ; engineers' vices, 3in. 2516 ; 3 in. 351- ; 4in., 451- ; 41in.

531- ; carpenters' bow saws, 8in. 1116 ; 10in. 1213 ; l2in. 1316 ;

8in. capacity two -speed breast drills, 291- ; saw sharpening vices1816 ; 8in. best quality black handled cutting out shears, 1116 pair;7in. quick grip woodworkers' vices, 441- ; push screwdrivers, 1216;plow planes with 3 irons, 221- ; adjustable plow planes with 8 bestquality irons, fin. to in., 3613 ; best quality handsaws, 22in. 1313;24in. 1319 ; 26in. 1413 ; steel back tenon saws, 10in. 1016 ; I 2in. 1219;

adjustable rebate and fillister-planes, 2613 ; 10in. super qualityratchet braces, 1616 ; 1, pint paraffin blowlamps, 2216 ; I pint glue -

pots, 816 ; I lb. adze eye claw hammer, 819 ; handy tools (axe, ham-mer, nailpuller), 1016 ; electricians' toolbags, I4in. 1519 ; I6in. 1619.

Carriage paid on orders to the value of 501-. For under that amountsend 21- for postage ; any excess will be refunded.

Illustrated list of tools, electric tools, wood and metalwork machinesfree on request.

PARRY & SON (TOOLS), LTD.,329-333, OLD ST., LONDON,

Telephone : Clerkenwell 3918-3859

" Branchesare ready to deal with your

tiegl on the spot

Every Halden branch is

fully equipped and readyto produce photo copiesof plans, deeds, documents,etc., by any of the usualprocesses. To the largeruser, Haldens offer a rangeof the most modernequipment for the pro-duction of their ownphoto copies. In con-nection with the pro-duction of maps,Haldens are licensed bythe Controller of H.M.Stationery Office toreproduce Ordnance

SurvePlapsin onecolour.

-40 OF MANCHESTER

J. HALDEN & Co., 8, Albert Square, MANCHESTER, 2Branches at : London, Newcastle -en-Tyne, Birmingham, Glasgow, Leeds and Bristol.

TRACK F

GARDENRAILWAYS

71" to 101" Gauge

Model railway enthusiastswill be glad to know that

13assett-Lovikecan now supply

full rangeof tract(

availablefor immediate

delivery.

RAIL in 14ft. lengths Pfinshnehe

bolts -2'.. lbs. tfacerr foot high.

;in.

at each end

lin. tread, 1 17132in.

'Gin. wide on foot. 22116

141t. length,.

P(Metinimum quantity41eng

.

materialsfor garden railways,

kin. to 101in. gauge

d IFISVIPLATESfor above, Com-

d steel plates

P ached with4

DOG

-HOLDING 1)13'8:4, rail to

SPIKES. for fPu(as illustrated).wood slectsers-10!.. pet IN*

rising 2 holes NNit.

Pu fishplatebolts at

4cocuplete,31,a,

Enquiries for largerquantities are welcomeand special quotationswill be given free.Please quote ref. TM/12.when writing.

BASSETT - LOWKE LTDHead Office and Works :NORTHAMPTON

London : 112, High Holborn, W.C.1. Manchester : 28 Corporation Stmt.

CONCENTRATED LIQUIDFINE GRAIN DEVELOPER

Always ready for instant use. Nofiltering or dissolving needed.Gives maximum speed consistentwith fine grain. Produces perfectlygraded negatives of excellent en-larging quality. A standard tech-nique makes it certain that youalways get the results you expect.Dilute one ounce with just theright amount of water to fill yourtank, develop the film and pourthe solution away. No trouble, nowaste and no need to run riskswith partly used solutions. Byfollowing the UNITOL routine youhave fresh, active and correctlydiluted solutions for every filmyou develop. A simple Calculatoris also sold giving developingtimes for all dilutions from 6 to 25.

225 cc. (8 -oz.) ... 316

570 cc. (20 -oz.) ... 616

Unitol Calculator, 4d.

JOHNSONS OF HENDONLONDON, N.W.4. ESTAS. 174).

erne 0-tmee -

one wag

cede itonee,

JOHNSONJ-20 TANK

For developing size 20roll films in daylight.Takes l0l,oz. of solution,Easy -to -load, sturdy one-piece spiral. Pouring lipfor splash -free emptying.Triple light -trapped lid.Complete with new Two -Way Agitation movementand a Calculator Disc.

PRICE 25/-

254 NEWNES PRACTICAL MECHANICS June, 1951

STUDYAT

HOME

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IS YOUR CAREER HERE ?IF NOT, WRITE FOR FREE ADVICEAccountancy Examination;AgricultureA M.I. Fire E. ExaminatioApplied MechanicsAuctioneers and Estate AgentsAviation (Engineering and Wireless)Blue PrintsBoilersBook-keeping, Accountancy and

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and ExaminationsGeneral Certificate of Education

ExaminationsGeneral EducationG.P.O. Eng. Dept.Heating and VentilatingInstitute of HousingInstitute of Municipal EngineersJournalismLanguagesMathematicsMet: I lergy

Mining, dII SubjectsMining, Electrical EngineeringMotor EngineeringNaval ArchitectureNovel Writin:PlasticsPlay WritingPlumbingPolice, Special CoursePreceptors, College ofPress Tool WorkPumps and Pumping MachineryQuantity Surveying-Institute of

Quantity Surveyors Exams.Radio Service EngineeringRadio (Short Wave)Road Making and MaintenanceSalesmanshipSanitationSchool Attendance OfficerSecretarial ExaminationsSheet Metal WorkShipbuildingShorthand (Pitman's)Short Story WritingSocial WelfareStructural EngineeringSurveying (R.I.C.S. Exams.)Teachers of HandicraftsTelecommunications

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COUPON. CUT THIS OUTIF YOU ATTEND TO THIS NOW IT MAY MAKE AWONDERFUL DIFFERENCE TO YOUR FUTURE

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Please send me (free of charge) particulars of

Your private advice about(Cross out line which does not apply)

PLEASE WRITE IN BLOCK LETTERSNAME

ADDRESS

State age if under 21 years

PAM INEIMMIN=IIIIMIMISIL-5 1=1"-- 9IM AO I M2 =I CID Sin MO %OP r..E.J MGM= iL

'1)&'

"F "Because of their HighSensitivity the S. G.BROWN Type " F "(Featherweight) Head-phones are a popularchoice by all requiringefficient, long and de-pendable service.D.C. Resistance 4,000 ohms.Impedance 14,000 ohms at1,000 c.p.s. Weight 9 oz.

The S. G. BROWN Type" K " Moving Coil Head-phones supply that HighQuality Reproduction soessential for DX work,monitoring, laboratorypurposes, etc.

D.C. Resistance 47 ohms.Impedance 52 ohms at1,000 c.p.s.

SEND FOR BROCHURE " P.M." IT GIVES DETAILSOF ALL TYPES OF S. G. BROWN HEADPHONES.

I towit,fitt,SHAKESPEARE STREET, WATFORD, HERTS.

Telephone : Watford 7241

(I)

Most sizes available from stock!

MICRO-DRILLS

STRAIGHT FLUTE DRILLS. A well -designed drill par-ticularly recommended for drilling brass. Rangeof sizes: .35 mm. (.0138") to 3.0 mm. (.1181")

PIVOT DRILLS

Widely used by watchand clock makingtrades for drillingvery small holes.Range of sizes :

.05 mm. (.002")to .5 mm.(.0197")

STANDARD SPIRAL

FLUTE DRILLS

A general purpose drillof improved flutedesign for easy ejec-tion of swarf.Range of sizes: .1mm. (.0039") to3.0 mm. (.1181")

FLAT DRILLS

Similar to pivot drillsbut made in largersizes. Range ofsizes: .25 mm.(.0098") to 3.0mm. (.1181")

SINGLE SPIRAL

FLUTE DRILLS

For drilling smallholes to extremelyfine limits. Range

of sizes: .1 mm.

(.0039") to 3.0

mm. (.1181")

WRITE FOR STOCK LISTS. N. BRIDGES & CO. LTD.

Bridges Place, Parsons Green Lane, London, S.W.6.

June, 1951 NEWNES PRACTICAL MECHANICS 255

RATCHET SPANNERS

UGE demand enables us toHer " Leytool " Ratchet Spanners atrices little above those paid forrdinary good quality spanners. Theyave time and money because they

work faster, operate more easily, andget into those inaccessible places whereordinary spanners will not go.

They are a sound British Engineeringjob, made of carbon chrome steel,hardened all over and negradised.Available in 8 standard sizes to fit150 nut sizes in B.A., Whitworth,B.S.F., S.A.E., Metric and square.Special sizes made to order.

Also available, Mechanic's Set of 5" Leytool " Ratchet Spanners in CanvasWallet, 49/6.

ZOOA to 4y1100/c FOR THE MOST UP-TO-DATE

AND EFFICIENT

DESIGN

PrecisionHand Drill

RatchetSpanners

(Mechanic'sSet)

UniversallyJointedSocket

Spanners

4 -bladed All Leytools are entirelyPocket original and patented de -

Screwdriver signs. Write for FREEIllustrated Booklet.

LEYTONSTO NE JIG & TOOL CO., LTD., High Road, Leyton, London, E.10Telephone. : LEYtonstone 5022-3-4.

POSTAL BARGAINS

TYPE 3

(c>

TYPE 1TYPE 2

TYPE 4

INDUSTRIALTHERMOMETERSType t for ordinary temperatures, extrarobust, heavy brass case Price 12/6with hook eachType 2 reading up to goo° F., can be usedwithout back plate, gradua- Price 716ations engraved on glass each f

* Plus 2/6 for returnable transit case.Type 3 for door or wall of baking or pro-cessing oven. Heavy brass case andprotective cover. This Price

OTYPE 5

reads up to 600' F. 32/6

Type 4 for low temperatures, minus3oo° F. up to I to° F. As illust.for mounting throughpipe line or tank, etc. Price 3216Type 5 is as type 4 except that there 3916is a much longer reach. Price

2 volt ACCUMULATORSuitable for radio or modeldriving, house lighting, etc. Heavymass type plates-precharged-only need filling. New unused-size Tin. x zin. x zin.as,'- value 5p2 Post andfor only u ins. ii3d.

4 VALVE RADIOMeans you can now have that extraradio. Ready to work, not a kit. AC/DCall mains. Four modern valves, gangtuning-high precision coils, condensers.resistor and other parts. Metal chassis,tunes Long and Medium Wave bands-large clear dial with station names-getsHome, Light, Luxembourg, etc. Amplevolume. Com-plete and with

2 YEARSFREE SERVICEChassis 57'6.Moving coil

espeaker15ing 6

else needed.Nothi Ajax.

METAL TRIPODTremendously strong, but notat all heavy. 3ft. high and withbrass male and female thread top.Black Japanned pressed steel,unused, but may need repainting.3/6 each, plus 2/6 post andpacking.

E.P.E. LTD/1.1 \

It

(I) Electron House,WINDMILL HILL, RUISLIP MANOR, MIDDLESEX.

ONLY 4DIN STAMPSBRINGS BOOK

MAKES MANY

PERMANENT

MODELSand utility objects,from simple instruc.tions in illustratedBooklet-pleaseread below.

. . . showing how such models as those above, and many others,can be made, without skill or special tools, from Sankey's PYRUMAPlastic Cement. Ready for immediate use in its plastic state,Pyruma sets or bakes to stone -hardness, and can be painted orenamelled in all colours according to instructions. Thereforerealistic natural -colour models can be made from Pyruma, including

HOUSES, BUILDINGS FOR MODEL RAILWAYS, DOCKS ANDAIRPORTS, SHIPS, MODEL FURNITURE, ANIMALS, FIGURES,RELIEF MAPS, Etc. as well as utility objects such as ASH TRAYS,BOOKENDS, MENU HOLDERS, PAPER WEIGHTS, ORNAMENTSand DECORATIVE OBJECTS.

Pyruma is inexpensive, and easily obtainable in tins from Iron-mongers, Art Material Dealers and Hobbies Shops. Send 4d. instamps to the address below for illustrated Instruction Book.

SANKEY'S

PYRUMAPLASTIC CEMENT

J.H. SANKEY& SON,I21"ILFORD EST. 1857 ESSEX

256

for

NEWNES PRACTICAL MECHANICS

;OESAW

319.0"

I bought this wonderfulWolf Cub electric drill

only f5. 10. 0- the sturdiest, mostpowerful and compact machine I have everused. Even more astounding was my dis-covery that by adding a few parts which costme B. 19. 0, I became the proud possessorAFXof a complete saw kit as well.

111HAITA

lATHE i259"I intend to add a few more parts to give me apowerful Lathe kit. Then with the Drilling,Grinding and Polishing Set I shall own acomplete Wolf Cub Home ConstructorOutfit. Just what I've wanted for years-andat such low cost as I never dreamed possible.

-and thats not all theWonderful Wolf Cab story,/

Write today for this fully descriptive illustrated folder. Readall about the greatest value for money ever offered inHorne Workshop and Handyman tools. Copy free on request.

WOLF ELECTRIC TOOLS LIMITED PIONEER WORKSHANGER LANE LONDON W.5 Telephone: PERIVALE 5631.4

* CHOSEN ON MERIT FOR THE FESTIVAL OF CRITAIN

Post free

June, 1951

Press -button soldering !The " BURGOYNE "

7 -SECOND

SOLDER GUNHere's the tool every home handyman has alwayswanted. Toll rtirigutzciAgla,nse

play.tool Nsoavee,riTeelneOuricei. bid

unlesslls. Makes

making a joint ; cold when not In use no element to burn out ; heatsup in 7 seconds : no risk from touching the " wrong end." No constantre -tinning. Ideal for handyman or radio enthusiast.

A.C; only 200-250 r.

DECCA TWIN -SPEED (78Ty3p3eA 3r7t1".)

RECORD PLAYERSManufactured by the pioneers of long-playing technique on a commercial scale in this coii-try. the Decca 37A Twin Speed Player gives the user facilities for playing both Long-Playi g

and Standard records on the same machine.The turntable is mounted on a heavy. pressed -steel base and the change -over from 78 to33-1 '3rd r.p.m. is accomplished by a simple but positive lever movement.Instead of the usual interchangeable heads, the crygtal element of the pick-up Is rotatedto Change from a 78 r.p.m. stylus to a 33-1i3rd r.p.m. stylus.A compact and reliable unit, the 37A player gives not only first-class reproduction, but first-class value for money.

Fully guaranteed L12-1-6 carriage paid

A "MUST" IN EVERY MODERN HOME

"ZEPHYR" HAIR DRYER

ONLY

84/-Phis 1-- postage

Hair must be dried quicklyand thoroughly after wash-ing to retain the sheen andbrilliance of its naturalappearance. The"ZEPHYR" will also dry"smalls," etc. Just plugin any mains and press.

Heat at once ! Supplied inglue, Cream. Lavender orTurquoise, complete withflex. When ordering, pleasegive choice of two colours.The "ZEPHYR" can beused on voltages 200-250.A.C. and D.C.

WINCHES or HOISTSWorm driven, reduction 187.5 to '1. drive by fin. sq. shaft, can be handoperated or motorised. fitted clutch and clutch release, quick no-loadwind, triple stranded steel cable extends to 61ft., end of cable fitted.mas-aye shackle suspension by steel bar lin. dia.at top of winch, size ovt,rarl 8In. x Ein. x.51n., weight carriage13Ibs., suitable for loads up to 12 cwt. New. petit

KOS MAIL ORDER SUPPLY CO., THE RADIO CENTRE,33, Tottenham Court Road, London, W.1

CHEMICALAPPARATUSAND CHEMICALS

CATALOGUESSend T,d. Post Free

VICSONS LTD. Contractors to EducationAuthorities and many of thelarge industria' laboratories

148, PINNER ROAD, HARROW, MIDDLESEXFOR ALL LABORATORY APPARATUS

" KARLENITE"PLASTIC MARBLE

The entirely new Artificial Stone for casting Bookends ; Ashtrays ; Wall -vases';Statuettes, etc. " Karlenite " sets granite -hard with a scintillating crystallinestructure which very closely resembles marble or alabaster. It is enormouslystrong ; highly resistant to heat and impervious to water. Literally any type ofnatural " veining " can be simulated in any colour and a range of pigments isavailable for this purpose.

MAKE YOUR OWNFLEXIBLE MOULDS

in "PLASTIMOULD " SYNTHETIC RUBBERPrepared in liquid form for making permanent elastic moulds. Ideal for repetition -casting Plaques, Bookends, etc., in plaster, cement or'' Karlenite." It will faithfullyreproduce even the most minute details of ornamentation and surface texture." Plastimould " is incredibly simple to use and moulds can be taken from anytype of pattern, including wood, metal, plaster, stone, glass, ivory, etc.

Send Is. far full details of this et.sy, fascinating and profitable hobby. Moneyrefunded to bona fide enquirers.

KARLENA ART STONE CO. LTD.(Dept. PM4), 55, Deansgate Arcade, Deansgate, MANCHESTER, 3


011141414Natcht4

INSTRUMENTSE SLIDE RULES

For over 70 years Thornton's Drawing Instrumentshave been used by the Engineers and the Surveyorsresponsible for the world's most famous constructions.The more important your work the greater the neces-sity for Reliable and Accurate Drawing Instruments.Insist on using only Thornton's for complete satisfaction.Illustrated catalogue sent post free on request.

A. G THOR.N TO N LTDSpectizibitd

W Y T.4-1.NI4-fA MAN Cf.-ff./TEFLTel : WYThenshawe 2277 (4 lines)

For Metalworkingand Woodworking

Lathesremain

THE CRAFTSMAN'S CHOICE

PLASTIC HAMMERThe plastic faces screwinto each end of the solidsteel head. They fit flushand are replaceable in tenseconds. This is an ex-tremely tough and durableplastic-yet it will never

idamage the part struck.Mallets of Rawhide, Lignum, Lead and Rubber arealso supplied. Used extensively in aircraft, auto-mobile and general engineering works, foundriesand by sheet metal workers.

WillaWWWWW1151P-11111WWW1111111111WW""

-.10WINNWWWW"11111WWWWIIWW -..110111111011WWWWW1 _.dilMIWNWINW=1111W11NNW W ' -.,- '4,'' 1111W '11W ill ailMIMOW IIIIIIIIIIWN \ VANT"WWWW Of IIWWW IIMMW E AWIL Al.MINNI16-4111.1W

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milly- -WI=W' MMIIoff _ 11WWI

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II

MORE skill atyour fingertips!

No. 86TOOL CHEST Almost a workshop

in itself. A complete assortmentoJ' tools in handsome, fitted 84/..

wooden chest.

No. 5 KNIFE No. 2 KNIFEfor heavy duty. With , ,, for normal cutting. Withone No. 19 blade 6, 6 one No. 22 blade 3:6

No. I KNIFEfor delicate work. Withone No. 11 blade 3: -

Try the perfect balance of X-acto knives, test the scalpel -keensharpness of X-acto interchangeable blades and you'll soon beconvinced that X-acto makes creative hands even more skilful.Call at your dealers and see the complete range of knives,blades, tools and attractive kits or write for illustrated folder.

* X-acto blades are available separately in packets. 5 short blades,straight 2;6, five short blades, curved 379 and 2 long blades 21-

THOR HAMMER Co., SALOP STREETBIRMINGHAM, ENGLAND. 'Phone : VICtoria 0987-3.

TRIX LTD., I I, OLD BURLINGTON STREET, LONDON, W.I.

G G


to every ambitious engineerthis valuable 176 -page handbook!

ElBetter days lie ahead if you add " ENGINEERINGOPPORTUNITIES " to your bookshelf. If vouwant to put yourself in line for quick promotion,higher pay and all that goes with it, as well as the sortof job you've always wanted, this enlightening guideto success -176 pages of vital, right up-to-dateinformation-is your blue -print for a brighter future.

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In this book you will find outhow to take advantage of to -day'sopportunities ; how you can riseto a position that ensures success,prosperity and security-the sortof job which, in Peace or War,Prosperity or Slump, makes youa " key " man on whom thecraftsman or fighting -man isequally dependent.

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11Thousands of B.I.E.T. Students-ordinary people with no specialadvantages except a real desire tosucceed - have, under ourguidance passed A.M.I.Mech.E.,.A.M.I.C.E., CITY & GUILDSand other major examinations.Because of our outstanding sue-cesses, you, too, can be confidentof your success, under theguidance of B.I.E.T.

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WhichoftheseisyourPetSubject

Mechanical EngineeringA.M.I.Mech.E.-CITY & GUILDS-GeneralMechanical Eng.-Maintenance Eng.-DieselEng.-Sheet Metal Work-Welding-Metal-lurgy-Machine Drawing & Design-Re-frigeration, etc.Electrical EngineeringCITY & GUILDS-General Electrical Eng.-Installations-Illuminating Eng.-ElectricalScience - Electricity Supply-Meters &Measuring Instruments-Mains Eng., etc.Radio & TelevisionA.M.Brit.I.R.E.-SERVICING CERTIFICATE-C. & G. Telecommunications-General RadioEng.-Radio Servicing-Television Servicing-Sound Film Projection-Electronic Eng., etc.Production EngineeringA.M.I.P.E.-Works Management-Foreman-ship-Staff Supervision-Planning Eng.-Cost-ing, etc.

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BRITISH INSTITUTE OF

ENGINEERING TECHNOLOGY

THE B.I.E.T. IS THE LEADING INSTITUTE OF ITS KIND IN THE WORLD


JUNE, 1951VOL. XVIII. No. 210

25;EDITOR

CAMM

Owing to the paper shortage "The Cyclist," "Practical Motorist, ' and " Home Movies " are temporarily incorporated.

FAIR COMMENT

THE FESTIVAL OF BRITAINTHE Festival of Britain is not only

an exhibition of British Industryand ways of life but it is in cele-

bration of the Great Exhibition of 1851which attracted world-wide attention.Great Britain in those years was thecommercial centre of the world. Itsgoods and its currency were the standardsby which those of all other countrieswere judged.

Victoria was on the throne in 1851and we were in the throes of an industrialrevolution. The national ways of lifewere changing, and so the year 1951enables us to compare the progress,or otherwise, which has taken placeduring the past very eventful century.

Until 188o the changes were mostlyin connection with improved standardsof living brought about by our colonisa-tion, the expansion of our MerchantService, and our development as a greatpower. And then, for no accountablereason, the scientific world proceededto shower upon us a number of greatinventions and vital discoveries whichhave entirely changed our ways oflife, and our methods of earning ourliving.

Free education has made us a moreintelligent race. The pneumatic tyrewas invented in 1888. The telephoneand telegraph, the early motor cycleand motor car, the development of roadtravel, the successful demonstration offlying by those early experimenterswho contributed so much to the firstsuccessful flight of the Wright Brothers,the advance of machine tools and mass -production methods, photography, thegramophone, the cinema, radio andtelevision-these are but a few of thescientific developments which havechanged, and will continue to change,the outlook of the world. The past5o years have been the most fruitfulin the world of science, invention anddiscovery in the whole history of theworld. Within recent years nuclearenergy has come to the forefront asone of the newest of sciences. Thesplitting of the atom, one of the dreamsof scientists for centuries past, is nowan accomplished fact.

Fission opens up an entirely newera in science, and it may within thenext five decades radically change ourscientific concepts of existing principles.

Einstein has already gone a long wayin that direction.

So it is fitting that in 1951 we shouldcelebrate the planting of that seedin 1851 by the Prince Consort andHenry Cole which has laid the founda-tion of scientific development through-out the world. This is a fact whichneeds to be stressed in a manner whichonly a Festival such as the presentmakes possible. Throughout the worldto -day there are insidious attemptsto belittle Great Britain by countrieswhich by now would not have existedas separate entities but for the develop-ments, as well as the protection, whichGreat Britain made possible and avail-able to the rest of the world.

It may be that we have perhapsbeen a little too generous, and thatwe have placed " rods in pickle "for our service. There may be thosewho, comparing 1851 with 1951, willconclude that in many ways thingswere better then than they are now.Such judgment, however, is based uponfalse reasoning.

The railways in 1851 were practicallyundeveloped. Road travel was uncom-fortable and risky and by stage coach.One must not judge road travel bythe alluring pictures of coaches arrivingat old inns which decorate Christmascards. No one to -day would like togo back to those days.

The Penny Post, introduced by SirRowland Hill in 1839, was a greatadvance, but in 1851 it was still acomparatively slow process. There wereno telegrams. Letters took days todeliver which now take hours. Therewas always the risk of highwaymen.Medical science had not progressed

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Registered at the G.P.O. for transmission byCanadian Magazine Fost.

Copyright in all drawings, photographs andarticles published in " Practical Mechanics " isspecially reserved throughout the countriessignatory to the Berne Convention and the

Repriductions or imitations of any ofthese are therefore expressly forbidden.

By The Editor

very far from the process of bleeding.The bicycle was still in the hobby-

horse stage. Very few people couldread. Free education was unknown,

-and our staple industries were coaland cotton, with pottery and engineeringrunning close. So it is not so much acentury of achievement which the Festivalepitomises, but a half century of achieve-ment, development and progress whichowes little, if anything, to the preceding5o years.

Most people in their fifties to -dayhave witnessed the remarkable develop-ments mentioned earlier. They haveseen them develop from the miraculousto the commonplace. In 1912 peoplewould hurry from their homes to witnessan aeroplane flying over. In 1922 radiowas considered a modem miracle. Tele-vision to -day is, almost a commonplace,and even school children are acquaintedwith the elementary principles of atomicenergy.

Children of the present generationmay have their outlook warped by thefact that most of them were born duringa period of war and, therefore, canhave no experience of life before 1939.

During the past too years sciencehas, paradoxically enough, given uscheaper goods, and then made themdearer. It has made them more plenti-ful and then scarcer. Indeed, as scienceadvances it produces the inevitableparadoxes because there are those whowill divert the real purpose of science,which is to make the world a place worthliving in, to purposes of destruction.Great Britain cannot be criticised onthat score.

The Festival is a wonderful displayof all that is British. It was opened onMay 4th by the King and Queen,preceded the previous day by a Serviceof Dedication at St. Paul's Cathedral.It was exactly too years ago that QueenVictoria and her Prince Consort droveto Hyde Park to open the GreatExhibition, and it certainly was amemorable day not only for Londonbut for the whole world.

There was no radio and televisionin those days, but the world flockedto the Exhibition, and buyers did notneed to be persuaded to come and inspectand buy our goods. It was the firstof the innumerable great exhibition;which have been held since. F. J. C.


11:111111114_-

ENGINEERBy

The Operation of the Modern Automatic Telephone Exchange Simply ExplainedAN acquaintance of mine told me the

other day that the average man in thestreet has not the slightest idea how

the automatic telephone works, and to provehis remarkable statement my friend askedthe first ten people of average appearanceand interests that we met. The majorityappeared interested, but had no idea whathappened at the telephone exchange ; theremainder had no idea, but couldn't care less,so my friend was, therefore, quite right. Iam endeavouring in this article to give apicture, in non -technical language, of themysteries of the automatic telephoneexchange.

Making a Manual CallWe all know what happens in a manual

exchange, so I will briefly run through eachimportant step in the establishment of amanual call and compare it with its auto-matic equivalent. A subscriber wishing tomake a call lifts .the receiver (Fig. t), or in

Initial stage on lifting receiver

(a) Manual

To operator'stelephone circuit,

--:Number please

F'

(b) Automatic

.o..

000

DialTone -Fig. 1.-Two stages in calling a subscriber-

by manual and automatic operation.

'the case of a magneto telephone, winds thehandle first. Whatever the instructions are,'the net result is that an operator or opera-tors at the manual exchange are made awarethat a subscriber is calling. I should men-tion that the subscriber's line terminates atthe manual exchange in a socket or " jack "as it is called, into which a plug can beinserted for extending the call to wherever itis intended to go. Associated with this" jack " there is a lamp or signal whichindicates when the subscriber wants to makea call. In addition, a common visual oraudible signal may be given to indicate thatsomeone somewhere is wishing to make acall. In response to this common signal anoperator will look around to see whose lampis glowing and plug into the associated

" jack." The operator will then throw akey or switch, which causes her telephone tobe connected to the calling line, and say" Number, please."

Automatic OperationNow let us look at the equivalent auto-

matic operation so far. The subscriber wish-ing to make a call lifts the receiver as before.The result is that the automatic exchange ismade aware that someone somewhere wishesto make a call. There are various automaticsystems, and I will start with one most com-parable with the manual system and whichone might expect to find in a very smallexchange, but not in the larger exchanges.In this system, when the automatic exchangeis made aware that a subscriber is calling,a piece of apparatus known as a Line Findersearches for the line wishing to make a call(Fig. 2). The line finder is an electro-magnetic mechanism having radial armswhich rotate around a central spindle andwipe over contacts on the periphery. Thenumber of such contacts depends on the sizeof the switch-we will consider a twenty-fivepoint switch for the moment. A subscriber'sline is terminated on each of the twenty-five peripheral contacts so that the arms canwipe over twenty-five subscribers' lines.Such a line finder is caused to step overeach of these twenty-five lines in turn untilit reaches the calling line. The calling lineis different from the others in that one ofthe rotating arms of the line finder en-counters an electric potential which causes

the line finder to stop rotating, and torest on the contacts of that line. Connectedto this line finder there is a piece of auto -

Call established

(a) Manual

,41.114 u..

(b) Automatic

ao

00.

Fig. 2.-Diagrams showing how the call isestablished.

matic apparatus which is capable of recognis-ing the first figure which the subscriber isabout to dial. This piece of mechanism isknown as a selector, and when the linefinder comes to rest on the contacts of the

Selector panels in a modern automatic telephone exchange.


calling line, the said calling line is now con-nected direct to a selector which is readyto receive the first dialled digit. To indi-cate this, a tone known as " dial tone " issent along the line to the calling party whichindicates that the subscriber may now com-mence dialling. This tone is comparable withthe operator's "Number, please."

In other automatic systems the line finderis turned round the other way so that in-stead of the selector finding the callingsubscriber, the calling subscriber finds a freeselector. There are also other methods bywhich the calling subscriber is connected tothe selector. They all may sound compli-cated, but everything happens very quicklyand, as you know, you hear dial tone in lessthan half a second.

You may, perhaps, ask why the selector isnot permanently connected to the subscriber'sline to save the complications of the linefinder or equivalent. The answer is thatthe selector is an expensive piece of apparatusand it is, therefore, more economical to pro-vide only as many of them as will be actuallywanted simultaneously in the busiest period,and to attach them as and when required bymeans of the much cheaper line finders.How many calls do you make over yourtelephone in a day ? Perhaps four, of which,say, two are made between 9 and to inthe morning, each lasting about two minutes,so between 9 and to o'clock you are usinga selector for four minutes. If there arefifteen of you in a group, each using a

selector for four minutesbetween 9 and to o'clock,the said selector would be inuse for exactly the wholesixty minutes, provided, ofcourse, all the calls made wereconveniently head - to - tail,but of course the calls occurat any time in the hour, andthe mathematicians have de-vised a formula which willtell you how many calls arelikely to occur simultaneouslyin these circumstances. Theywould probably say that fourselectors would be requiredby the fifteen subscribersinstead of fifteen if theselector were tied directly tothe subscribers.

The " Speaking " KeyLet us now go back to

the manual exchange. Theoperator has just plugged in,thrown the " speaking key "and asked the subscriberwhat number he wants. Wewill consider first a smallexchange of about sixty lines-the " jacks " of whichcould be arranged in sixrows of ten-and that thesubscriber asks for No. 52.The operator takes the

A bank of final selectors.

A typical rotary line switch.

other plug of the connecting circuitand inserts it into jack No. 2 of the fifthrow, that is, of course, if subscriber No. 52is not already engaged. The operator cantell if the subscriber is engaged or not, eitherbecause there is already a plug in that jack,or in the case of a larger exchange wherethere are several appearances of the jack, theoperator would hear a distinctive click inher telephone if she endeavoured to put theplug into the jack of a line which is alreadyengaged. This click is caused by the appli-cation of a characteristic potential. The call-ing subscriber's line is now extended, via thecalling jack, plug, cord circuit, plug, jack ofthe wanted party to the wanted subscriber,and all that remains to do now is to ringthe wanted party's bell. In a small exchangethis would be done by the operator connect-ing ringing current via a ringing key to thecord circuit and thus to the wanted party'sline. Also associated with the cord circuitare two lamps, or signals, which indicate theswitch -hook condition of the two sub-scribers, that is, whether or not they havehung up. This lamp, or signal, will also indi-cate to the operator when the wanted partyresponds to the ringing current. At the endof the call the operators can tell when thesubscribers have hung up by these lamps,and when both subscribers have hung upthe operator will pull the plugs out andeverything will then be normal again.

Impulsing RelayIn the automatic equivalent we left the

calling subscriber listening to dial tone. Itis necessary here to explain that there is adirect current loop from battery through anelectromagnetic relay in the selector, the armand contact on the line finder to the sub-scriber's premises and back again to theexchange, through a contact and arm of linefinder through another winding of theelectromagnetic relay in the selector to theother side of the battery. 'The direct currentthus flowing causes the electromagnet in theselector, called the impulsing relay, to beenergised. The dial tone is superimposed onthis circuit. Also in series with this loopthere are the interrupter springs of the dial.

(To be continued)


A Simple MagneticConstructional Details of an Experimental

Loop InstrumentBy G. R. JUDGE

MAGNETIC recording is now as firmlyfixed in our lives as are radio andtelevision, and any reader who cares

to devote a few hours to the subject will getplenty of amusement apart from an insightinto a very interesting scientific subject.

The simple mechanism shown in Fig. rwill record short phrases, such as " Sorry, nocigarettes," " Keep moving, please," " Queuealong here," and so on ; these phrases, oncerecorded, could be reproduced every fewseconds for days, weeks or years, until thewire or tape itself had worn away. On theother hand, any recording made can beimmediately removed from the wire or tapeby feeding into the head an alternatingcurrent, or by setting a small magnet along-side the loop so that, as the recordingmedium passes by the head, or magnet, themagnetic flux erases any previous recording,thus preparing the loop for recording again.Such a device would be a boon to a personlearning public speaking or plays ; one couldspeak a line and hear it played back immedi-ately, thus learning the quality or otherwiseof the diction. A few inches along the tapeor wire from the recording head G would beplaced the playback head H. The erasinghead or magnet would then be placed any-where along the line between HBCDG.

Look again at Fig. r. You will see a

CouplingTransformer

Fig. 2.-Push-pull, self -amplifying microphone,with D.C. biasing to the recording head.

board, square in this case but any othershape will do as well, in the top left-handcorner of which is fitted a small electricmotor. The motor used is a gramophonemotor, but this is optional. In place of thegramophone turntable is fitted a " capstan,"the diameter of which must be taken intoconsideration when determining the speed ofthe tape or wire ; if a gramophone motor isused which normally rotates at 78 r.p.m., bysimple calculation it is possible to work outthe correct diameter of the capstan. Take a3in. capstan, for example ; 3in. multiplied by3 r/7th (the accepted multiplicant for work-ing out the circumference of a circle) willgive you the circumference of the capstan.Since the capstan will revolve 78 times perminute we multiply by 78 to get the totallength travelled per minute. If we dividethe result by 6o we shall then know thetotal length travelled per second. Followingthese calculations, we find that a 3in. capstanrotating at 78 r.p.m. will have a perimeterspeed of roughly rein. per second. Recordermanufacturers are satisfied with a speed of71in. per second for tape, and 2ft. persecond for wire, so rein. should give us a

little better quality fortape, as quality im-proves with speed.

Recording Tapeor Wire

Around the capstanand the three cornerrollers is placed aband of " Diamond"recording tape or of" Crown " recordingwire, whichever youprefer to use. Thecapstan will drive thisrecording mediumaround, and to over-come possible slips a" pinch " wheel isarranged to press the medium on to thecapstan. This pinch wheel A is heldon to the capstan by a tension spring,which doesn't show in the diagram asit is behind the board. To keep the bandof tape taut, one of the three corner rollersis not mounted directly on to the board ;instead, the spindle of the roller passesthrough a slot in the board and is mountedinto a strip of 'metal the end of which ispinned to the board. In this manner the

Output FromRadio Set

Nr., Wire Wound VariableResistance To Apply DCBias To Recording Head

Fig. 3.-Utilising extension speaker sockets tofeed the recording head.

spindle can move to left or right within theslot on the arm of metal. At the back ofthe board the strip of metal is held with atension spring so that the roller is alwaystrying to pull outwards, thus keeping the looptaut.

To join the two ends of the magnetic tapetogether a piece of self-adhesive selotape isused ; the ends should be firmly joined withthe adhesive on the glossy side, and anysurplus adhesive should be neatly trimmedaway to leave a smooth edge. The wireshould be joined by knotting carefully andtrimming back the ends.

Fig. r (F) shows the recording head,and H in the same figure the playbackhead; the latter can be placed in anyposition, either close to or away from therecording head. If you wish to record longerphrases it is suggested that you fit morepulleys, so that the wire or tape can .zig-zagup and down the board, instead of justmoving around the edge. Once you havethe principle mastered, you can even fit upa recorder with spools of tape or wire.

To energise the head you can either usea self -amplifying microphone to record

RecordingHead

ecorder

Fig. 1.-General view of the completed recorder.

speech (Fig. 2), or if you wish to record aradio programme or re-record a record fortesting purposes you can connect the record-ing head to the extension speaker socketsof your radio, at the same time connectinga pick-up to the pick-up sockets (Fig. 3) ;when a record is played through the pick-upit will then be recorded on your wire or tapethrough your recording head. It must beemphasised, however, that re -recordings madein this way are for your private use only ;performances in public, for whatever pur-poses, are an infringement of copyright andlikely to be frowned upon by the owners ofsame.

For playback purposes one really needs asensitive amplifier, as the amount of energystored in the recording medium is quitesmall. Although the stage gain of thedomestic radio between pick-up sockets andoutput is not very great, one can overcomethe difficulty by connecting headphones intothe extension speaker sockets and connectingthe playback head to pick-up sockets (Fig.4). To get the playback louder at least athree -stage amplifier would be needed.

Playback HeadRecording and playback heads are quite

easy to make. Referring to Fig. 5, you willnotice a brass cup having a flange, whichhelps to fasten it down to the base -board.A is a piece of old felt hat forming apad, B is a piece of spring (an oldgramophone governor spring is suitable).The felt pad lightly presses the tape Ton to the gap C in the head. The wind-ing on a strip of mumetal is shown at E,

Pick -Up SocketsOn Radio Set

PlaybackHead

Low ResistanceHeadphones To CheckQuality Connect 7o

Extension LS. Sockets

4.-Method of usinging quality when using

headphones for check -the playback head.


the two ends of the winding meet at Cand pass through the wall of the brass cupso that the tape T can be made to slideacross the ends of this mumetal strip. Athin flake of mica D separates the twoends of the strip ; this mica also passesthrough the wall of the cup, but its purposeis to keep the two ends of the mumetal stripno more than a thousandth of an inch apartand thus form the magnetic " gap." Whatlooks like sacking in Fig. 5 is the magnifiedgrain of the bakelite board seen in Fig. t,

Fig. 5.-Enlarged detail of the playback headshowing the windings on the mumetal strip

and the head shown in Fig. 5 is a magnifiedreproduction of that in Fig. 1. If you havenothing in your junk box similar to the brasscup shown, cut off a piece of brass tubingabout fin. diameter and fin. long. Slit thisdown one side and, with a well -cleanedand tinned hot soldering iron, thinly tin theinside and outside of the tube near the cutand also the two edges of the cut ; thistinning should be as thin and smooth asthe surface of a tinplate can, so while thetube is still hot and the solder " wet " wipeit off with a piece of rag to avoid any ridgesor blisters of solder. Next, take a piece ofmumetal in. wide and roughly tin. long-this metal is very expensive, costing about3s. per square inch, so to avoid spoilingit practise first with a piece of tinplate.Mumetal, by the way, is the very oppositeto a magnet ; it will not retain magnetism.

Winding the Mumetal StripHaving cut your piece of metal to the right

size, clean the edges with a fine file toremove all burrs, then thinly tin the endsfor about fin. on both sides, once againmaking sure to wipe off all surplus solderwhile it is " wet." With a pair of square -jawed pliers give a slight set to the endsso that if the strip is held upright andregarded on edge with the sets t3 theleft, the top set will point at t t o'clock andthe bottom set at 7 o'clock. Now wrapthe strip with two layers of selotape andwind on about 520 turns of 32 -gauge wire;try to leave a space in the middle of thestrip to allow for bending round intocircle, winding the wire evenly on bothsides of the space-in Fig. 5 E indicatesthe two half -windings. Having wound thestrip, bend it to lemon shape (Fig. 6) andplace it within the brass tube so that thetwo ends which have been set at a slightangle poke through the slit in the tube, asin Fig. 6. The slit in the tube shouldpush the two ends of mumetal togetherso that there is no gap discernible betweenthem. You can then push between thetwo ends a very thin flake of mica, makinga gap of about one -thousandth of an inchbetween the two ends. When you are satis-fied that all is ship-shape, apply a hot, tinned

soldering iron (but without any extra solder)to the gap, so that the ends of the stripand the tinned tube fuse together. If thewound strip is left loose within the brasstube you will find it difficult to make anyrecordings, as the gap in the head willmove and vary in size. When the solder-ing is firm, file away any surplus metal,which will be the ends of the mumetal strippoking through the slit in the brass tube.

Polishing the TubeWhen you have filed these ends level with

the tubing, well polish the tube at thisspot with a fine metal polish until the sur-face is very smooth, as any roughness wouldsoon scrape off the oxide coating on therecording tape. If you have decided to usewire for recording, file a narrow channelin the tube and across the gap for the wire -to run in.

Matching TransformerThis type of head will be a low impedance

head and will need a step-up matchingtransformer to couple it to the impedanceinput of a valve, which is high. Fortu-nately, there are plenty of small microphonetransformers available quite cheaply. Fora temporary test where no microphone trans-former is available a speaker transformercan be used.

Not much power is needed for recording,so don't shout into the microphone. As anexample, if you were trying to magnetise aneedle, a 6in. nail, and a jemmy, the needlewould need only a few ampere turns of wirein comparison with the jemmy. Rememberthat in recording you are only trying tomagnetise a few molecules of material a

thousandth of an inch long (the width of thegap).

The fitments shown in Fig. t to the left ofthe head and below the tape, and betweenhead G and roller D, are bakelite sockets tovriich are connected the adjacent heads. Tomake connection one has only to plug inthe relative plug, and arrangements are madefor either recording or playing back. Both

Strip or Mumetal

Wind Strip In Two Halves So That Strip Will BendWithout Dama9inq Turns of Wire

The Strip Bent So ThatEnds Meet To PassThrough Wall of Tube

File Away SurplusMeta/ 8 Polish ToA Glass Finish

Fig. 6.-Method of winding and bending themumetal strip, showing how the ends of the stripprotrude through the slot in the brass tube.

the heads shown in Fig. I are made inexactly the same way, except that H wasmade in a brass cup and G in a piece ofbrass tube fitted between two pieces of brassplate.

Sixty -ton Oil Circuit Breaker

This huge B.T.H. oil circuit breaker can be seen at the South Bank Festival of BritainExhibition. The total weight is over 6o tons-the largest made in this country-and it has acapacity of up to 275,000 volts. In the background looms the Mining Section of the Exhibition.

ittpur,...t.-

264 NEWNES PRACTICAL MECHANKS June, 1951

BuildinA Aluminium Boats -4With Notes on Design

IF a gunwale angle is being used thisshould now be riveted on. The skegs,bottom stringers and centre -board trunk

should now be assembler:f alreadydescribed, for the other comPonints. Thedeck sheeting should be laid on the boatand marked off to shape. Cut the deckplating to shape and rivet up as alreadydescribed for the bottom plating. Beforeriveting the decking on make sure that anyfittings that are inaccessible once the deckingis on have already been assembled. Nowassemble all the minor fittings, such as maststeps, rowlock brackets, seat bearers, etc.

Painting the HullThe hull is now ready for final painting.

First remove all filings, drilling swarf, etc.,then remove any oil or grease and touch upany parts where the priming coat has beenremoved. Two coats of finishing paintover the primer are usually sufficient.

Boat DesignDesigning your own boat is as much fun

as building it, and is not very difficult pro-vided you keep to certain simple rules andhave an elementary knowledge of solidgeometry. As for the method of construc-tion previously described, the following

\' 25° Maximum

By G. F. WALLACE, A.F.R.Ae.S.

(Continued from page 233, May issue)

hyperpola and, therefore, near enough astraight line for practical purposes. Thismay all sound a little theoretical, but is thereason for the following limitations. Aspreviously stated, the tangent of the bowcurve at the stem should not exceed 35° tothe centre line of the boat, and the angle offlare should not exceed 25°, as illustrated inFig. 32. When commencing the design ofa new boat the first thing to decide is thelength, as this is the leading dimension.Small racing boats, for instance, are classifiedby length-r2ft. National, r4ft. International,etc. Other dimensions of the boat-beam,freeboard, sail area, rudder size, centre -boardsize-are best determined by a study ofexisting boats of similar design and lengthwhich are known to be successful. The major-ity of small boats in this country are of roundbilge design, and the following points mustbe borne in mind when comparing roundbilge with hard chine designs. For the samelength, the hard chine boat should have lestbeam than the round bilge boat and, in thecase of sailing boats, lessfreeboard. The hardchine boat will draw lesswater, and, in the case of Tsailing boats, will require

35° Maximum

Fig. 32.- Diagrams showing tangent of boat curve and angle of flare.

method of design is simplified for amateur useand, in consequence, has a number of limita-tions. It does not include calculations ofmetacentric height, curves of areas or meta -centric balance. Such things are a waste oftime on a small boat in which the crew formthe major item of weight. All curves inplan are arcs of circles, and both angle offlare and angle of Vee in a Vee-bottomedboat are constant from stem to stern. It isonly in speed boats that a varying angle offlare or Vee is really necessary. It is alsoassumed that the chine angle is constant andthat the cross -sections are straight lines.Actually, neither of these assumptions ismathematically correct. In a curved how,the angle of chine would only be constant ifthere was no angle of flare, i.e., the bottommaking an angle of 90° with the sides. Pro-vided the bow is reasonably sharp, the changeof angle in the chine angle is very small, twoor three degrees at the most, and can easilybe taken up when riveting the chine angle.In general, it can be taken that the tangentof the bow curve at the stem should notexceed an angle of 35° to the centre line ofthe boat. This means, in effect, that youcannot use the apple bow of the Dutch bargetype of boat. As regards the sections, theside would only be straight if there was noangle of flare, or if there was no curve inplan, as in a punt.

Angle of FlareWhen flare and curves in plan are com-

bined, the sides become conic surfaces, andthe sections are conic sections, i.e., hyper-polas or parabolas. If the angle of flare isnot great and the bow curve not excessive,the section of the sides is the tail end of a

sail area of boat A is m, then the correctarea for boat B is xm z x w2

x x y2

Flat or Vee-bottomedHaving got some idea of the length and

beam of the boat, the next thing is to decidewhether it is to be flat or Vee-bottomed. Aspreviously mentioned, there is a lot of un-warranted prejudice against flat-bottomedboats in this country. They are far morepopular in America, and in the Far Eastnearly all boats, great and small, are flat-bottomed. The chief disadvantage of theflat-bottomed boat is that, owing to its small

Fig. 33.-The base plan.

Fig. 34.-A typical baseline of one half of a boat-the other half is symmetrical.

a bigger centre -board ; in the case of rowingand motor boats a bigger skeg is necessary.Flat-bottomed boats also usually benefit byhaving a small skeg forward, as this improvesthe control of the boat in high winds. Whencomparing boats, care must be taken to com-pare like with like ; for instance, the sailarea of a family picnic boat should not becompared with that of a r4ft. Internationaldinghy, even if the overall lengths are thesame. As a rough guide it can be assumedthat the beam of a boat varies as the squareroot of the length, and also sail area variesdirectly as the length and as the square ofthe beam. This is expressed mathematicallyas follows : -

If boat A is x feet long and y feet beam,and boat B is z feet long, then the beam of

y X l/zboat B is ,--

V x

If the beam x of boat B is w and the

e

p

Icc

d

a

b

Ro

displacement, it is apt to be uncontrollable inchoppy seas and high winds, and sailingboats of this type are not good performers towindward. It is considered, however, thata lot can be done to improve flat-bottomedboats in this respect by proper design ofskegs, centre -boards and rudders. The seconddisadvantage is that they pound heavily inrough water; this is not so serious structur-ally in an aluminium boat as it is in awooden boat, but it is always uncomfortablefor the crew. The Vee-bottomed boat is adevelopment of the flat-bottomed boat, andis an attempt to partially overcome the dis-advantages of the latter. In general, Vee-bottomed boats have a greater displacement,are better performers to windward, and donot pound so badly as flat-bottomed boats.As against this, there is much more work inbuilding them. The frames are more com-plicated, needing an extra gusset, and thereis an extra watertight joint at the bottom ofthe Vee. The Vee-bottomed boat, there -

.3 4 5 6 7

Fig. 35.-Base line ele-vation and plan, andcross-section at frame 3.


fore, requires at least 25 per cent. more man-hours to build, and it is considered that thistype is only justified for fast racing boats orpower boats that are going to be used habitu-ally in rough water.

The Scow BowThe shape of the bow must now be

decided, and in this connection it is sug-gested that the reader should consider themerits of the scow bow. Like flat bottoms,it is not very popular in this country, its usebeing confined to praam dinghys. It ismore widely used in America, where thebilgeboard scows of the Great Lakes aresome of the fastest sailing craft in existence.The scow bow is usually considered suitablefor smooth water only, but it is the mostcommon form of bow for Chinese junks,

p

Rt

width of transom are decided by comparisonwith similar boats to the one being designed.

The Base PlanThe first thing to determine when laying

out the boat is the base plan. This is illus-trated in Fig. 33, and is, in effect, the projec-tion of the sides and transom of the boat on toa plane parallel to the centre line at a depthequal to the maximum depth of the boat.The maximum beam of the base plan is thebeans at the chine of the centre section ofthe boat, i.e., the maximum beam minus theamount of flare. It should be noted that itis assumed that the maximum depth andmaximum beam both occur at the mid -section.The length of the base plan is the maximumlength minus the amount of overhang of bowand stem. This is not easily determined in

advance, but on thetype of boat being con-sidered is usually gin.to t8in. less than theoverall length. Fig. 34shows a typical baseline, the dimensions a,b and c have alreadybeen fixed, and it isnecessary to determinethe radii R1 and R2.These are given by the

a'

many of which are noted for their seaworthi-ness in the rough waters of the China Sea.In a flat-bottomed boat of light displacementand with the correct amount of rocker on theiottom the bow is normally clear of the water,and a sharp bow does not do any trade any-way, except in rough waters. The advantageof the scow bow is that it makes the boateasier to construct and gives more room inthe boat for a given length.

Some mention must be made of the double -ended boat, which is the standard type forcanoes but is rearly used for dinghys. It issupposed to be a more seaworthy type, butit is doubtful if this applies to boats undert8f t. long. Pointed bows usually give along, narrow boat, but if used in conjunctionwith a scow bow give a boat of more normalproportions. An advantage of the double -ended boat is that, if it is symmetrical aboutthe mid -section, a considerable amount oftime is saved in drawing, marking out, etc.As previously mentioned, the freeboard and

Fig. 36.-Holf-sections of frames.

Fig. 37.-Dia-grams showing themethod of deter-mining the angle

of rake

following formula':a' + 4132

8b4 (b- c)2

- 8 ;b-c)It should be noted

that it is only necessaryto draw on half of theboat as it is symmetricalabout the horizontalcentre line. Havingdrawn in the base line,the next thing is to

n a draw in the frame posi-tions and number themoff. These are thelines numbered t to 9

in Fig. 35. Now draw the base line inelevation, indicated by m -n in Fig. 35 andthe chine line w -x. The height of w and xabove the base line m -n should be such thatthey are just clear of the water when theboat is fully loaded. This means that thevolume of water displaced by the boat belowthe line joining w and x parallel to the baseline must be equal in weight to the totalweight of the boat. The shape of the linewx must be such that the first third fromeach end is nearly straight fairing into aneasy curve into the middle third. Fromthis it will be apparent that the correctheight for w and x must be obtained bytrial and error. The sheer line y -z is now

Fig. 38.-Sheer curve development.

b

a

drawn in, the only rule governing the sheeris that it is normally greater at the bow thanat the stern.

Cross -sections of the HullThe cross -sections of the hull can now be

drawn. As an example, consider frameNo. 3, Fig. 35. Draw a horizontal linerepresenting the base line and a vertical linerepresenting the centre line of the boat.Mark off the beam a -b on the horizontal lineand from b draw a line at an angle a equalto the angle of flare. From a mark off a -c,the height of the chine line above the base.From c draw a line c -e parallel to the baseline. From c mark off the distance c -dequal to the depth of the boat at this frameand draw d -f parallel to the base line; c -d -f -erepresent the true shape of frame No. 3,also c -e is the width of the bottom at frameNo. 3, d -f is the width of the gunwale, ande -f is the true length of the side. This isrepeated for every frame in the boat, andthe resultant cross-section drawing is shownin Fig. 36. It should be noticed that thegunwale and chine points in the sectionsshould lie on a regular curve ; if they donot, check the drawing carefully to see thatthere are no mistakes. In Fig. 35 w -v repre-sents the transom, and the rake of the tran-som, if any, is quite arbitrary. The widthat y is found by extending the base curve

Fig. 39.-Section at frame 3 for a Vee-bottomedboat.

(Fig. 34) to cut the projection of y andlaying it out as for the frames. In obtainingthe line x -z it is assumed that the width ofthe stem is constant and that the angle offlare at the bow is constant. This fixes theangle of rake of the bow and if it is requiredto alter the angle of rake, then either theangle of flare or the width of stern must bevaried. The angle of rake is obtained asfollows: from point a in Fig. 37 draw a linewith the angle of flare a and mark off x sothat a -x is the height of x above the baseline; draw a line through x parallel to thebase to cut the line from a at b, then x -bis half the width of the stem. Through bdraw a vertical line to cut the gunwale line atz. This gives the vertical height of the stemz -a1; mark off the distance z -a1 above the baseline in elevation and draw a horizontal line.Where this line cuts the sheer line is the pointz, which can now be joined to x to give therake of the stem.

In practice, this would be done on Fig. 35,in which the gunwale curve is already drawnand has only been done separately for pur-poses of illustration. It may be found thatthe width x -b is greater than is required; inthis case mark off x -m the required halfwidth of the stem. Through m draw a lineparallel to a -b to cut the base line at n. Inthe plan of the base line (Fig. 37) draw aline p -q parallel to the centre line and adistance a -n from it. Extend the radius to cut this line at v and project to theelevation and mark the point xs represent-ing the new base of the stem. Obtain z'as previously described for z. It will benoticed that this slightly increases the length

266

of the boat and alters the curve of the chine.In consequence, the width of the stem shouldbe fixed before the other frames are laid out.Certain other information can now beobtained from the drawing in Fig. 35.

Referring to frame No. 3 again, measurethe length of the curve b-1 and the angle ofthe tangent of this curve to the horizontal.The length b-1 is the true developed lengthof the side of the boat between framesz and 3 and a is the laying angle at frame 3.Now measure the length of the curve p -cand the tangent of p -c to the horizontal 0.The length p -c is the true developed lengthof the bottom between frames z and 3 and0 is the faying angle of the bottom atframe 3. Repeat this for all the otherframes.

The development drawing of the bottomcan now be made ; this is done by plottingout the width of the bottom represented byc -c, the distances between frames being thetrue lengths p -c. In making the develop-ment drawing of the sides, the true lengthof side between frames is 1-b and the truedepth of the side is e -f. . The height of eabove the datum, however, is neither a -c norb -e. In development the line e -f swingsback so that it lies in the same plane as o -h,the side at frame 5 and the widest point ofthe boat. From e draw a line at right anglesto f -b to cut o -h at g. Then g -h is theheight of e above the datum line in thedevelopment of the sides.

Sheer Curve DevelopmentIt is possible to so arrange the sheer curve

that its development is a straight line. Thismeans that the edge of the sheet can be usedas the gunwale and datum, thus saving timein marking out and sawing up the sheet.This is done as follows: mark out the linesa -c and a -b in Fig. 38, a -c being the widthof the section at the point of maximum beamand 'a -b being the height. From c draw aline at the correct angle of flare a. From bproject to d, which is the sheer line at thissection. From d draw a line d -x at rightangles to c -d. For any frame section layoff the base line width a -e and the chineheight a -f, and obtain the point g, as previ-ously described. Extend c -g to cut d -x at h.Then h is the sheer line point at the framein question and h -j the deck line. This is

NEWNE.S PRACTICAL MECHANICS

repeated at each section and the correspond-ing sheer line points plotted in the elevationto give the sheer line. This method is notsuitable for all designs, as it tends to givea very exaggerated sheer if the bows are fullor the flare angle excessive.

So far it has been assumed that the boatis flat bottomed. If it has a Vee bottom allthat is necessary is to impose the Vee on tothe sections drawn as for a flat-bottomedboat. In Fig. 39 the section of frame 3from Fig. 35 is reproduced. If the boathas a Vee bottom, a line is drawn from e atthe correct angle of Vee a to cut the ver-tical centre -line at h. Then h represents thekeel line of the boat at this frame. This is

Cardboard

Wood

Fig. 40.-Cardboard model for checkingpurposes...

repeated for all frame positions and theresultant c -h dimensions plotted in the eleva-tion to give a keel line under the chine line.With a Vee-bottomed boat the volume of theVee must be included in the calculations ofdisplacement referred to previously. It ispossible to give more rocker to the chine in theVee-bottomed boat, but the middle two-thirdsof the chine should be under -water. Ex-cessive angles of Vee should be avoided, andlittle is gained by making it more than55 deg. to the horizontal at the mid -section.

The layout drawing as in Fig. 35 shouldbe drawn out k or full size. At this

A5'

Elevation /8' 8

Seat 2=4' x /2*.x /-

I I

Deal! ofTransom

Plan

Detail of Chine

June, 1951

scale it should be possible with care tomeasure off the various dimensions to withinI/16 of an inch, which is accurate enoughfor practical purposes. This means thatlofting is unnecessary, and the drawingdimensions can be laid out full size directlyon to the sheet metal of the bottom and sides.At 6 full size a boat 58ft. long can be laidout on a standard drawing board 3ft. 6in.long.

General Arrangement DrawingIn addition to the layout, a general

arrangement drawing of the complete boatis required in order to fix the position ofvarious items such as seats, centre -board

trunks, mast steps, etc.In the accompanying examples

of general arrangement draw-ings it will be noticed that nodevelopment drawing or anydimensions are given for thedeck. The reason is thatvarious small errors thataccumulate during buildingusually result in the gunwalebeing anything up to tin. out,and it is best to mark off theshape of the deck plates fromthe boat.

Using a Half -modelAs a check on the correctness of the

frame dimensions and development drawingsobtained from the layout, it is a good planto make up a full model of the boat incardboard, as shown in Fig. 4o, to a scaleof y or full size. The frames are cutfrom thick cardboard or plywood andmounted on a piece of wood at their correctspacings and height. The developments ofside and bottom are then cut out in thin card-board and they should lay on the frames togive a fair curve and good fit at the chine.

Careful Checking NecessaryIf there appears to be any discrepancy, thedimensions of the layout should be carefullychecked. If any mistake has been made thismodel will show it up and save a lot oftrouble later.

(To be continued.)

End Elevation

Mid Section

i%*

-u

Detail ofGusset

I

4 z

I

Side elevation, plan, and details of a lift. aluminium punt.


Principles of UltrasonicsPractical Applications : Generators : Bibliography

SOUND and noise are almost synonymousterms to most people, so that it wouldseem appropriate to preface a study of

ultrasonics with the strict scientific definitions.Sound is the perception of external stimuliaccepted through the ear and sense of hearing :also the wave motion or vibration which givesrise to such stimulus when applied to theear. In this respect sound may be consideredto include that branch of mechanics whichdeals with vibratory motion. The practicalengineer will not require proof in order tounderstand that all sounding bodies are in astate of vibration. Noise, however, is sub-jective and its study cannot be divorced fromthe realms of psychology ; probably thebest definition of noise is the one given bythe B.S.I., viz., " Sound undesired by therecipient."

Ultrasonics, sometimes called supersonics,although this latter term is falling into disuse,is the science of mechanical vibrations andradiations in solids, gases and fluids, whichhave frequencies in excess of those which,in a sound wave, would be in the aural range.Such frequencies may be considered to liebetween 20,000 cycles,'second and 5 >: to'cycles/second. The wavelengths will varywith the velocity of propagation in differentmedia (see Table r), but very often the wave-length will approach that of visible light,5,000 to 7,000 A° (rA°=10-8 cm.).

Wave MotionThe propagation of all sound is in, the

nature of a wave motion through elasticmedia, but the movement of any particle ofthe media is purely local, each particle oscil-lating about a mean position. The oscillatorymotion is in the same line as the direction ofadvance of the wave. This is termed longi-tudinal motion and may be contrasted withtransverse motion as in water waves.

It will be understood that ultrasonics isoutside the aural spectrum, in much the sameway as the vast majority of electro-magneticwaves are outside the visual spectrum.

The Practical Applications of UltrasonicsA large number of investigators have

contributed to our knowledge of the phen-omena surrounding high frequency soundwaves. Submarine detection and communi-

AnodeFocal spot

Flair

X Ray

Fig. t.-Radiographic exposure for non-destruc-tive testing.

By F. W. COUSINS, A.M.I.E.E.

TABLE IVELOCITY OF SOUND AT is° C.Substance. VelocitySolids cm/sec.Ash .. 470,000Beech 335,000Brass 350,000Copper 360,000Lead 125,000Oak .. 400,000Steel 500,000

LiquidsWater 145,000Alcohol 120,000

GasesAir ..Helium ..Oxygen ..Water vapour

33,20095,40031,700

Hydrogen .. 28,000

cation between submerged submarines in-spired a large amount of original work.It other fields the studies -were only laboratorycuriosities and it is only now, with improved

&Light source

Ultrasonicgenerator

Material undertest

DiffractionspectraA.C.Sopply

2; Lens

Ligu,'d vessel

'6"L en sappears here Screen-v.

Fig. ia.-111ethod of ultrasonic non-destructivetesting.

Screen, SonogramAppears here

Oil film 4 to 7 infn of oil orbanzolin glass dish

ercury film

Ultrasonic generator

Fig. lb.-Another method of ultrasonic non-destructive testing.

ultrasonic generators, that many of thesecuriosities begin to have the appearance ofan industrial application ; a special paragraphis hereinafter devoted to an explanation ofthe principles of these modern generators.

Prior to a consideration of possible olm-mercial values, it is of great interest to recordthat the common bat, vespertilio of the orderChiroptera, in the animal kingdom, avoidsobstacles in its substantially blind ying bygenerating ultrasonic waves with its mouth ofa frequency upward of 50,000 cycles/second,and receiving the echoes of the said wavesreflected from objects in and around its lineof flight.

Phenomena Associated with Ultrasonicsr. Biological-destruction of bacteria and

small forms of life.2. Degassing of liquids.3. Production of colloidal forms.

Testpiece

4. Coagulation of aerosols.5. Detergency.6. Communications' and depth finding.7. Non-destructive testing of materials and

component parts.

20

01.1x/0

-20

(Cast) Cobalt

Iron

Nickel-400 200 400 600 800 1000

MAGNETIC FORCE H /N CG.S.UNITS

Fig. 2.-go/de effect in iron, cast cobalt andnickel.

d LX io`

/0

6% Ni

76% Ni

/000 2000 3000GAUSS -4 NI. ALLOYS

Fig. 3.-goule effect in iron -nickel alloys.

r. The leading study of biological effectsof ultrasonics has probably been undertakenby Dognon and Biancani.' It has been foundthat the high frequency waves are capable ofkilling bacteria, small fish and other smallanimals. The destruction is usually due tocavitation and the waves are able to disruptcompletely cell membranes and micro-organisms.

2. Degassing of liquids-liquids subjectedto the high frequency waves are degassedby the fact that the waves tend to cause themicroscopic gas bubbles in the liquid tocoalesce. Boyle, Taylor and Froman' in-vestigated this and drew the conclusion thatthe gas bubbles are already there in a micro-scopic form and that coalescence is broughtabout by the radiation pressure of the waves.

3. The colloidal state is a state of sub-division of matter in which the particle sizevaries from that of true " molecular " solu-tions to that of coarse suspensions, thediameter of the particles lying betweento-' and to -5 cm. Ultrasonics may beemployed to transform immiscible liquidssuch as water and oil into an emulsion whichexhibits true colloidal characteristics. A tubecontaining the liquids is often placed at thefocus of a parabolic reflector under waterand the high frequency waves are so generatedunder the water as to reflect from the saidreflector and agitate the liquids in the tube.The emulsion so formed may then be ex-amined for colloidal state by seeing if itexhibits the Tyndall effect*. Rschevkin andOstrowsky have produced fine emulsions ofmercury, sulphur, tin, bismuth, lead, copperand silver in water. It is generally agreed thatthe dispersion is caused by cavitation.

4. Aerosols are colloidal systems, suchas a mist or fog, in which the dispersionmedium is a gas. No cavitation occurs whenthe aerosol is subjected to the high frequency

* Cone of light directed into suspension-conebecomes visible.

268

waves, but the particles tend to coagulate.This phenomena has been used to clear theair of tobacco smoke, etc.

5. Detergency-the dust and dirt inclothes and on surfaces may be removed, tosome extent, by ultrasonics, but the powerof the waves has to be of an appreciableorder. An ultrasonic washing machine forlinen has been suggested, and certain laundrieshave considered the advantages of such a

Cooling water

riard nickel "tube

Feed back coil

Rubbersupport

OrivingA/)

Ultrasonicwaves generated

here

l/OV.D.C.

Polarisingcurrent

+ -2000 V DGplate V


Milhlhauser7 protected such a scheme in1931 and the technique has been advancedby Sokotoff 5. Two methods of ultrasonicnon-destructive testing, due to Sokotoff, areshown diagrammatically in Figs. ra and lb.

The Generation of UltrasonicsThe generation of ultrasonic waves may

be accomplished with a specially -designedwhistle, or siren, but these pieces of apparatushave little practical application. From manyattempts in the past to perfect an ultrasonicgenerator, two types have now been left in aposition of unrivalled supremacy ; they are :

r. The magnetostriction generator and2. The piezoelectric crystal generator.

Both of these generators are electro-mechanicalin operation and, for the reader to under-stand the niceties of their operation, thephysical basis of the phenomena of magneto-striction and piezoelectricity will have tobe explored. This exploration, however, hasfilled many excellent books, and any short-comings in an article of this nature may berepaired by the bibliography attached.

The Phenomenon of Magnetostrictionand the Magnetostriction GeneratorMagnetostriction phenomena appear in

//I/ two distinct forms, and they may be classifiedas follows :

Fig. 4.-A tubular type. of magnetostrictiongenerator.

method. No practical equipment for suchwork is known to the writer, but from arecent articles it would appear that theMullard Laboratories have made experi-ments in this direction.

6. Ultrasonic waves may be concentratedinto a beam of small cross-sectional area,and this facilitates their use in surface com-munications.

In the homogeneous medium of salt watergreat use of submerged ultrasonic generatorshas resulted in the location of icebergs4;signalling through the water from ship toship, and the calculation of the depth of theocean bed from the surface. In many ofthese applications the echo principle isemployed and the time lapse between trans-mission and reception is carefully measured.

7. Non-destructive testing is of interestto all engineers in its unique approach to avery difficult problem. Two methods ofnon-destructive testing are fairly well estab-lished. I refer to magnetic crack detectionswith such apparatus as the " Magnaflux "semi -portable crack detector, and the use ofX-rays in the extensive science of Radio-graphy6. In the latter case the process isanalogous to the use of ultrasonics.Flaw Detection by X-rays

Fig. r shows in diagrammatic form the basicprinciple of crack or flaw detection by X-rays,which are a form of radiant energy similar tovisible light. Their distinguishing featureis their very short wavelength, t2oA°to o.o6A°, and the feature is responsiblefor the ability of X-rays to penetrate materialswhich absorb or reflect ordinary light. It isa characteristic of ultrasonic waves that theyhave very short wavelengths and manymaterials, especially those possessing acoustichardness offer excellent media for the trans-mission of the ultrasonic waves. Metals areexcellent transmission agents. If the mediais not homogeneous, that is to say, it hasinvisible hollows, cracks, flaws or greatporosity, then the transmission of the wavesis seriously disturbed from the transmissioncharacteristic to be obtained in a flawlessportion of that media.

b

o>(b-a)= c

Fig. 5a

Fig. 5c

d

o

O

Fig. 56

Figs. 5a, b and c.-Showing the componentparts of and built up and wound vibromotor.

Form t. Alterations in the physicaldimensions of a magnetic material incidentupon the magnetisation of the said magneticmaterial.

Form 2. Alterations in the magneticcharacteristics of a magnetic material incidentupon the subjection of the said magneticmaterial to mechanical stress.

Both Form r and 2 are further subdividedscientifically into effects ; the effects underForm r are classified according to the deforma-tion produced, while the effects under Form 2are classified according to the (reciprocal)magnetic changes. It has been shown inmany works on this subject, 15, 12 that theprimary source of magnetic moment inferromagnetic material is the spin of theelectrons in certain unfilled shells of theatoms of these materials, and that the spinsmay be aligned into domains, called Weissdomains. A sample in the demagnetisedstate is thought to be everywhere self -saturated, the directions of the magnetisationvectors being directed at random. Uponmagnetisation, however, the alignment of themagnetisation vectors occurs. In this way achange in dimensions may be associated withalteration of the magnetisation vectors of theindividual domains. If the material elongatesin the direction of the applied magnetic

June, 1951

field it is termed positive magnetostriction,and negative magnetostriction if a reductionin size is recorded.

The magnetostriction effects under Form rand Form 2 are given in tabular form below,so that the reciprocity may be appreciated.

Form t. Form 2.

Longitudinal Joule effect.

Transverse Joule effect.Barrett effect.Guillemin effect.

Wiedemann effect.

Longitudinal Villarieffect.

Transverse Villari effect.Nagaoka -Honda effect.Reciprocal Guillemin

effect.Reciprocal Wiedemann

effect.

The Joule effects, of the order of ro-6 in./in.,are changes in the linear dimensions of aferromagnetict when a magnetic field isapplied along a specified direction, while theBarrett effect, observed with difficulty,considers the volumetric magnetostriction,its order being ro-7 cubic in. per cubic in.The Guillemin effect treats the bendingwhich a ferromagnetic exhibits when exposedto a magnetic field and finally the Wiedemanneffect, treats of the twisting of a ferromagneticunder the combined action of circular andlongitudinal fields.

The Villari effects refer to changes inmagnetic induction due to longitudinal andtransverse mechanical stress, and the Nagaoka -Honda effect the change in magnetisationresulting from a change in volume.

The reciprocal Guilleman and Wiedemanneffects will need no explanation.

The Joule EffectFrom the viewpoint of the magneto-

striction oscillator or generator of ultrasonicwaves, the most important effect, from thisprofusion of effects, is the Joule effect, and agraphical representation of this is shown foriron, cast cobalt and nickel in Fig. 2 and foriron -nickel alloys in Fig. 3. Naturally,impurities in these materials and varyinggrades cause the characteristics to vary con-siderably. It will be noted that nickel showsthe largest effect and it is very popular in manymodern' generators. Magnetostriction oscilla-tors or generators were first studied by Piercemand they comprised thin rods within a solenoidexcited by a small alternating current super-imposed over a steady magnetiSing current,the rod being set into longitudinal resonantvibration. To overcome undesirable stressesat the centre of such rods, the modern

The Joule effect has also been noted in non-ferro-magnetics by Kapitza, Roy. Soc. Proc. A.135, 556, 1932.

Radiating unit

Supports

Coil

Section on line 0

Coil

magnetostrictionelement

Side clamps

Magnetostrictionelement

Fig. 6.-A magnetostriction generator.


oscillator is usually circular with toroidalwindings.

Fig. 4 shows a tubular type of generatorusing the Joule effect as perfected by Schumb,Peters and Milligan" to study the cavitationerosion of ship's propellers. The nickeltube was mounted vertically and longi-tudinal vibrations of 9,000 cycles/second wereproduced. The tube was hard drawn nickelof t2in length, Fin. O.D. and o.o28in. wallthickness. A not dissimilar type of vibrator

Fig. 7. -Slice of quartz cut from a crysta'.

El

El

r

£2

Figs. 8a and 8b. -Two simple ultrasonicgenerators using quartz crystals.

has been disclosed in British Patent No.283,116.

Two modern magnetostriction generatorsare typified by the generators disclosed inBritish Patents Nos. 610,221 and 621,125.The former, due to Societe de Condensation etd'Applications Mecaniques, is shown atFig. 5a, b, c. Fig. 5a, is an elementarymagnetostrictive plate ; the body of length" c," vibrating lengthwise, is the key part ofthe vibromotor. The trapezoidal headspermit the required frequency to be achievedwith a short plate. Fig. 5b shows an ele-mentary magnetic plate, the dimension "d "being greater than (b -a) ; also dimension" e ' =" c." Fig. 5c shows how the vibro-motor may be built up and wound. Thelatter, due to the well-known SubmarineSignal Co., will be readily understood fromthe drawing and its appended references atFig. 6.The Piezoelectric Effect and the Piezo-electric Crystal Generator

Properly ground plates or bars of quartzand certain other crystalline materials, suchas Rochelle salts, show a mechanical strainwhen subjected to an electric charge. Con-versely, mechanical stress may be set up inthe crystal when a potential difference isapplied across appropriate faces of the crystal.This last mentioned effect is the one with whichwe are primarily concerned in the ultrasonicgenerator art. The pioneer investigators ofthe piezoelectric effect were the brothersPierre and Jacques Curie (1880). LordKelvin enunciated the thermo-dynamicprinciples of the phenomena and intensivestudies were undertaken by Woldemar Voightin 1894.

In 1910 Voight published his famous" Lehrbuch der Kristallphysik," whichenumerated the 32 crystal classes in whichpiezoelectric effects may exist. The FirstWorld War accelerated practical applicationsof the phenomena and Langevin in Francesucceeded in utilising vibrating quartz platesas sound emitters for sub -oceanic work.

The theory of piezoelectricity is mostclearly and thoroughly presented in Cady's

classic work" on the subject and the moreserious reader is referred thereto for authorita-tive information. It can be generally shown,however, that if a slice of quartz is cut from acrystal as indicated in Fig. 7 and pressureapplied to the opposite faces of the slice,electrical charges will be produced. Lippmannshowed that this had a reciprocal effect inthat electrical charges could be so applied asto cause the crystal to develop elastic deforma-tions. If the electric charges are producedby an alternating current, the quartz may besubjected to vibrations at a frequency inharmony with the frequency of the appliedelectric field. In this way the vibratingquartz may be used to generate vibrations inother associated media.

It has been shown by Wood" that thedensity of quartz is 2.654 gm./c.c. and Young'smodulus is 8 x to" dyne:sq. cm. The velocityof compression waves in the quartz is

A/8 x to"2.054.

5.5 x 105 cms. `Sec.

Thus ).=5'S x to5where

A is the wavelength in ems. andf is the frequency in cycles; sec.If both faces are free to move, the funda-

mental mode of vibration will have a nodalplane in the slice centre, and the slice thickness

will be --2.

The frequency f: for a slice thickness oft " vibrating in its fundamental mode will be

f= 5.5 to' 275 x 103cycles sec.

2Cady" shows two simple ultrasonic genera -

Liquid under influence ofsupersonic waves

Upperelectrode

- -1

E(asticfluid tight

packing

Lower electrodefull of air or gas toprevent transmission

of sound downwards

Uppervessel

Piezo electricplate

Insulating liquid.

lower fluid tightcase

insulating liquid

Fig. 9. -Special piezoelectric ultrasonic gener-ator. General constructional details only.

tors using simple quartz crystals and theyare reproduced in Figs. 8a and 8b.

Fig. 8a comprises a crystal bar " c " forlengthwise vibration, the electrodes EE2 beingof tin -foil. The crystal is in abutment with thetube T and the piston P, which is slideablein the tube, reflects the radiations.

Fig. 8b comprises a very similar arrangementfor higher frequencies, the crystal being madeto vibrate across its thickness.

Typical modern crystal ultrasonic genera-tors are disclosed in British Patent No.619,679, due to the Submarine Signal Co.,and also in British Patent No. 619,872, dueto Societe de Condensation et d'ApplicationsMecaniques ; the last mentioned generator isshown schematically in Fig. 9. It is specificallydesigned to cut down losses, one electrodebeing in contact with the liquid to be treated,or if this should be a conductor of electricitythe liquid per se may act as one electrode,the other electrode being contained in areceptacle filled with insulating fluid.

A comparison of the driving force in dynesfor magnetostriction and quartz crystalsubaqueous loudspeakers has been given by'

# For refinements of this calculation see Proc.Inst. and Radio Eng., Vol. 14, p. 447.

Olson", the schematic arrangement of theloudspeakers or vibrators is shown at Figs.toa and lob.

The driving force in dynes generated in the

Coil

Crystal

RodCase

- Magnet

Electricleads

Crystal mount

Figs. toa and iob.-A magnetostrictive and apiezoelectric subaqueous vibrator.

rod of the magnetostriction device (Fig. ma)is given by the relationship

:7(sin

Nlk

In the piezoelectric quartz device (Fig.lob) the relationship is

YA E KF=1

where F= driving force in dynes.N= number turns in coil.I = abamperes.k= constant -Joule magnetostriction

effect.r = reluctance.

=2:rf.f= frequency in cycles/sec.t = time in seconds.Y =Young's modulus in dynes/sq.cm.A =area of crystal (cross section).e = applied voltage in statvolts.1= effective length of crystal in ems.K =crystal constant 6.4 x to -8 quartz.

ConclusionIn conclusion, as an index of the increasing

interest of ultrasonics to industrial applica-tions, attention is directed to some of themore recent patent specifications filed.

Patent No. 527,562. Reimar Pohlman.Massage apparatus for effecting massage byvibration at supersonic frequency.

Patent No. 602,095. E. G. Budd Manufac-turing Co. A method of welding, includingindicating the condition of the weld by mech-anical oscillatory energy.

Patent Nos. 615,578 and 615,579. Testingof solids for fissures and other defects bysupersonic waves.

Also Patent No. 615,684. Electro-acoustictransducers, Sperry Products, Inc.

r. Dognon and Biancani, Ultrasons et Biologie.Paris. 1937.

2. Boyle, etc. Cavitation in the track of an ultrasonicbeam. Trans. Roy. Soc. Canada (iii) 23, 187, 1929.

3. Ultrasonics. R. R. Whymark. Electrical Review.,5th April, 1949.

4. British Patent No. 145,691.5. Magnetic Crack Detection. C. B. Young. 1942.6. Radiography in Modern Industry. Eastman

Kodak Co., Rochester 4, N.Y.7. Muhlhauser. German Patent 569,598 (t93t).8. See Ultrasonics, by L. Bergmann. 1938.9. G. E. Review. D. Williams. March, 1942, page.

161.ro. Modern Magnetism. L. F. Bates. 1939.Ir. Magnetic Materials. F. Brailsford. 1948.12. Magnetostriction Generators. J. A. Osborne.

Electrical Engineering June, 1948, v. 67, D. 571.13. G. W. Pierce, Proc. Amer. Acad. Arts & Sci.

63.1,1928.14. Metals and Alloys, 8, 126, 1937-'5. Piezoelectricity. W. G. Cady. 1946.,6. Acoustics. A Wood. 1940. See pages 220-223.17. Olson, H. F. Dynamical Analogies. 1943.

Elements of Acoustical Engineering. 1947.


The Mosquito ALM TarA Practical Engine for Cyclists

IN our August, 195o, issue we gave acomprehensive article dealing with thelatest motor -assisted bicycks. Since the

article was published, other auxiliary engineshave appeared on the market, among thesebeing the Mosquito, which we have had undertest. This 38 c.c. engine is made by Mosquito

desired to pedal with motor disengaged, therider does not feel the least extra resistance.

An important thing to consider with friction -drive motors is tyre wear, but with theMosquito it is practically equal to that ofmotorised bicycles with chain or geardrive.

Fig. 1.-The Mosquito auxiliary engine for cycles-showing the largediameter ribbed driving roller. Drive pressure is ensured automatically

by two springs.

Motors, Ltd., Moorfields, Liverpool, 2, andcan be fitted to any type of bicycle, normal,light or heavy without any modification. Itcan be attached in a few minutes by only twobolts which fix it to the stiffest part of theframe.

It is a two-stroke engine having counter-current scavenging and a piston with a flathead. The mixture consists of 2 to 3oz. ofoil for each quart of petrol. The position ofthe engine increases the stability of the bicycleand the numerous cooling fins allow theMosquito to work perfectly also in climbingand under highest temperature conditions.The ignition is thoroughly sheltered and theengine will work in the heaviest rain.

The DriveThe drive is by a large -diameter ribbed

roller driven through reduction gears. Thedrive pressure is ensured automatically bytwo springs so that the engine follows exactlythe contour of the tyre. The compact arrange-ment of the engine and the drive is shownclearly in Fig. 1.

The elastic swinging suspension, which canbe seen above the drive, neutralises thevibrations and ensures that the roller adherenceis kept constant. The width of the Mosquitohas been reduced to a minimum, and nomodification of the crank assembly of thebicycle is necessary.

It is so small that the chainguard covers itcompletely and only the silencer protrudes(see Fig. 2). By moving the lever, which isshown above the suspension in Fig. r theengine is disengaged from the tyre so that' thebicycle is at all times thoroughly free. If it is

The crankshaft, con-necting -rods and driv-ing roller are respect-ively mounted on roller,needle and ball bear-ings, and the automaticcarburettor is prov-ided with single -levercontrol with air filter,fuel pump and chokingdevice.

InsuranceRegarding the driv-

ing licence, paymentof a fee of 5s. enablesone to obtain a provis-ional driving licence.Before a Road FundLicence will be granted,a certificate of insur-ance must be obtained.This can be obtainedfrom the Iron TradesMutual Insurance Co.,Ltd., Iron TradesHouse, 21-24, Gros-venor Place, London,S.W.r. The rates ofpremium, which willcover all riders and notbe restrictive to anyclass of use, are :

Comprehensive cover(subject to theinsured bearing thefirst £ r of each and

EnAine

Fig. 2.-Some idea of the smallness of, theMosquito unit can be gained by comparing it

with the size of the chainguard.

every claim) £1 12s. 6d.Third party, fire and theft .. 17s..6d.Third party only .. is. §d.

Characteristics of the Mosquito EnginePiston displacement . . . . 38 cc.R.p.m. 4,200Corresponding speed . . . . 20 m.p.h.Minimum speed . . . . 4 m.p.h.'Gradient climbed without pedal assistance

5-6 peilcent.Fuel consumption . . . . 25o m.p.g.Fuel tank enough for . . 125 miles

(approx.)Net weight of the engine .. 151b. '

(approx.)

In a Cardiff Ordnance Factory

Boring the barrel of a 20 -pounder tank gun at the Cardiff Royal Ordnance Factory. Thetime taken in the boring is now only one-third of the time required at the end of the war.


A Trip by Flying -boatA Description of a Flight to Madeira

By MAURICE F. ALLWARD

SINCE last November, when B.O.A.C.replaced the last of their flying -boatswith Hermes landplanes, it has been

left to privately -owned Aquila Airways to runthe sole remaining flying -boat service opera-ting from this country. Once a week aflying -boat takes off from SouthamptonWater and commences the 1,300 -mile flightto Madeira, lovely Portuguese island about40o miles off the north-west coast of Africa.The return journey is made four days later,and while at the island a quick shuttleservice is run to Lisbon.

Bearing in mind the controversy arousedover the elimination of flying -boats by ournational air corporations, I was verypleased when business recently took me ona flying visa to Madeira, and enabled me togain first-hand experience of travelling bythis type of aircraft which seems so popularwith passengers and unpopular amongairlines.

Arriving at the Marine Airport, South-ampton, at 8 a.m. we had cleared theemigration and customs formalities and werecruising down Southampton Water within anhour. For some time we taxied past thefamous docks to which vessels of everynationality come from all over the world,particular interest being shown in the QueenElizabeth which had berthed the previousday. The flight was to be the first one byflying -boat for most of the other passengers,who included British and American holiday-makers,- businessmen and an elderly coupletravelling under doctor's orders, and we wereall looking forward to the trip.

The "Take -off."For those who love the sea, the, actual

take -off in a flying -boat is a thrillingexperience. We had been cruising along athalf power, but as we turned into thestraight the engines were opened full outand with a terrific surge of power we startedon the take -off run. Aircraft accidents arerare these days, but when they do occur itis usually during landing or take -off. Thedisastrous consequences on a big landplaneof engine failure at take -off are well known,but as we sped over the writer it was com-forting to know that only in the mostrestricted area is this an anxiety to the flying -

boat pilot. Soon our speed was that of anexpress train, with spray flashing high pastthe windows until, quite suddenly, all becamerelatively quiet and we were airborne. Thetime was 9.10 a.m.

Our Hythe flying -boat, the Royal MailAircraft Hampshire, had looked deceptivelysmall from the quayside, for she was actuallya double -deck airliner, divided up into anumber of spacious cabins, each seating upto six passengers, and complete with apromenade deck and bar, and a well-equippedgalley. When going aboard I had asked for" a seat with a good view " and had beenplaced in the main cabin amidships. Theadjacent window sloped outwards slightly,making it possible to look almost straightdown and so obtain a wonderful " plan-orama " of the green fields of the Isle ofWight as we climbed steadily on our way.Unfastening our seat belts, and adjusting ourarm -chairs to a lazy angle, we all settledback comfortably. A feature commented onby several of the passengers was the way ourcabin was conveniently sheltered from theglare of the sun by the high -placed wing-an amenity denied to the passengers of mostmodern land -based airliners as these havelow -placed wings.

By to.to a.m. we were crossing the Brestpeninsula and heading out over the Bay ofBiscay while coffee and biscuits were served.A note from the captain informed us thatour ground speed was 170 m.p.h and thatwe were due to arrive at Funchal, the capitalof Madeira, at 5.t5 p.m. local time. Threehours then passed during which we cruised

db,MADEIRA

CANARYISLANDS

Map showing the Madeira route operated byAquila Airways, Southampton.

serenely above an almost unbroken oceanof white clouds, before Cape Finisterre, onthe tip of Spain, was sighted. The time was12.50 p.m. or rather 11.5o a.m. Madeiratime, as we lost an hour on the way out.We had covered 585 miles of our journey.For an hour fortunate gaps in the clouds

(Above) Aquila's Hythe " Hampshire" mooredin Funchal harbour, Madeira.

(Left) There is no sheltered bay, and the flying -boats use the open sea at Funchal.

afforded us views of the olive hills of Spainmoving slowly beneath us like pictures ona vast cinema screen. A surprising featurewas the absence of any transport on theroad or life in the fields. A pleasant hourwas then spent eating an excellent lunch, thevariety, number and size of the courses ofwhich almost proved too much for me. Soft

272 NEWNES PRACTICAL MECHANICS

drinks were also " on the house," and thosewho preferred something stronger orderedtheir choice from the bar.

Over the AtlanticAs the Hampshire left the Spanish coast-

line and headed out over the vast expanseof the Atlantic, the knowledge that below usan " emergency " landing -ground stretchedall the way to our destination induced afeeling of security. After all, it seems logicalto use flying -boats on long over -water routes,for their ability to land in any but thestormiest seas is obviously a safety featurein the event of an emergency and theirgreatest advantage over landplanes. Theyhave done so not once but many times. Mostrecent example of such adventures, which withlandplanes would have been disasters, wasthe forced landing through fuel shortage ofthe Bermuda Sky Queen in the Atlantic in1948, in waves six to eight feet high, withoutany harm to the flying -boat, passengers andcrew.

At 5 p.m. another mesage from thecaptain informed us that the Porto Santoislands were sliding by the port windows,and soon afterwards Madeira itself came intoview, a mountainous mass towering above theHampshire, but a welcome sight after hoursof limitless sea.

No wonder that flying -boats are the onlyaircraft capable of operating to the island asit was obviously impossible for an aerodrometo be built at reasonable cost. This also

explains how Aquila are able to operate theirMadeira -Lisbon shuttle service before return-ing to the United Kingdom, for as far asPortugal is concerned it is cabotage traffic-a foreign company running a domestic airline. Happily, the Portuguese authoritiestook the lenient view that as they could notoperate landplanes to the island, and sincethey had no flying -boats themselves, theywere quite prepared to let an outside com-pany provide the air service, with consequentbenefit to all concerned. The 500 -mile triptakes four hours as against about 36 hoursby steamer.

Touching Down at FunchalFor some minutes we flew parallel to the

coastline, watching the villages passing by,little patterns of white and peach -colouredhouses with bright red roofs, until Funchalcame into view.

There is no sheltered bay for landing atFunchal, and Aquila's service to Madeiraprovides an interesting study of open seaoperations with flying -boats, proving thatregular flights to unsheltered alighting areasare possible in certain cases, although, asmight be expected, bad weather has some-times interrupted the service. But most ofthe hold-ups have been caused by badweather at the Southampton end.

Preparing for the run-in, we flew close tothe face of the cliff in order to get in thetriangle of calm air formed as the wind blewupwards over the top. Then there was a

June, 1951

view of the water coming up to meet us,slowly at first and then seemingly to racepast the wing tip floats at fantastic speeduntil with a gentle swish our keel touchedand we were down. The time was 5.15 p.m.as predicted by the navigator over nine hoursearlier.

The Hampshire was then taxied towardsthe protection of the small harbour break-water. Flying -boats, of course, do not needbrakes like landplanes, as the drag of thewater is more than sufficient to slow themup quickly as the engines are throttled back.Drag drogues are carried, however, and aswe neared the mooring buoy one was releasedover the starboard side to provide a gentleturning action, swinging the bow round andenabling the buoy to be picked up.

This simple buoy constituted Aquila's" terminal base " at Madeira. One couldnot help contrasting it with some of theelaborately equipped B.O.A.C. bases alongtheir old South African route, the overheadsof which were largely responsible for theCorporations' decison to withdraw its flying -boats. Aquila's arrangements at Funchalwould not, of course, be suitable for a high -frequency service, but for the tourists whoform most of their passengers it is ideal. Allthe " glamour " of a foreign port is evidentfrom the moment the aircraft taxies into thesmall harbour. All too efficiently the gailypainted local harbour launch Angiolina camealongside to take us ashore and a memorableflight was over.

Radio Control of MechanismsSimple Position -control Systems Briefly Explained

THE easy way to acquire an understand-ing of an unfamiliar technical art isto specify first what its aims are, and

then examine the possible ways of achievingthem, side by side with methods and tech-niques already familiar and well understood.This, briefly, is what the writer has done inthe following notes on the radio control ofmechanisms.

The aims can be defined as the remoteccntrol, by means of an intermediate radiolink, of the position of selected componentsof a distant piece of mechanism; or, if weinclude telemetering, the remote indication,by similar methods, of such information astemperatures, velocities, pressures, etc.

To be practical, let us add at once thatradio position -control includes such applica-tions as the flying under radio control of afull-size Service aircraft, as was successfullycarried out many years ago with the R.A.F.Queen Bee. The " selected components " ofthe Queen Bee, for instance, were all theessential flying controls. There are manysimpler examples, and at random one couldquote the remote operation of a camerashutter for nature photography and thesteering of a model yacht-both of whichhave been done.

Amongst practical examples of radio tele-metering there is the daily release ofmeteorological balloons, which, as they ascendthrough the atmosphere, send back through asmall transmitter suspended underneath read-ings of barometric pressure, temperature andhumidity. The signals front the balloon arerecorded at special ground stations and,after the necessary interpretation, are used inthe preparation of weather forecasts.

Position -control SystemsFor the time being, however, we will con-

sider position -control systems only, and-compare them with the most familiar radio -

By DENIS HART

communication systems of all-sound andtelevision broadcasting. When the announcerreads ou the nws, sound waves from hisvoice cause the ribbon or diaphragm of themicrophone to vibrate, and this mechanicalmovement produces corresponding EMFs,which are amplified and applied as modula-tion to the carrier wave of the transmitter.At the receiving end a minute fraction ofthe power radiated by the transmitter ispicked up, amplified, demodulated, amplifiedagain, and then applied to the speech coilof the loudspeaker. The diaphragm or cone

Receiver

Controlconponenledts

Actuator

Fig. 1.-Elements of the radio position -controlsystem.

of the loudspeaker is thus caused to vibratein such a way that it produces sound waveswhich are a passable imitation of thoseoriginating in the studio, and it is obviousthat the movements of the loudspeaker coneare a more or less exact copy of those of themicrophone diaphragm.

In a television system the movements ofthe spot on the screen of the picture tubeare an even more faithful imitation of thecomplex antics of the scanning spot in thestudio camera tube. In both these systemswe have already virtually attained ourobject.

Obviously, there are many desirable

modifications, and we have exaggerated alittle in inferring that the spot on a tele-vision CRT can be considered as amechanical " component " ; but all theessential elements of a position -control systemare there. In their simplest form they areas set out in Fig 1.

Starting from the left, it will be seen thatthe microphone has been replaced by thecontroller, which, we will assume, can reacton the carrier of the transmitter without theaid of a separate modulator-in the mostelementary case it will merely switch it onor off.

Function of the ActuatorAt the receiving end the loudspeaker has

been replaced by an actuator, about whichwe will have more to say later on in thisarticle. Its function, in our elementarysystem, is to react to the signal deliveredby the receiver and change the position ofthe controlled element. Perhaps this needsa little more explanation ; again taking thesimplest possible case the actuator mightconsist of an electromagnet solenoid, thearmature of which is pulled into the coilwhen current passes in the output stage ofthe receiver, and, for example, switches thepropulsive system of a model boat. For thesake of completeness-and our elementarysystem is now quite complete-it ought to beadded that the power output available frommost practical receivers is so limited that asensitive relay is incorporated between theoutput stage of the receiver and the actuatoritself in order to step up the power levelsufficiently for the latter.

Let us now revert for a moment tomodulation methods. It was mentionedabove that we would assume for the sakeof simplicity that the controller merelyswitched the carrier on or off. In many

June, 1951

practical cases, particularly with models, thisactually happens, so that the controller andmodulator are one and the same .

But suppose we want two or three, or evenmore, actuators simultaneously under control.In such cases we must turn to moreadvanced methods of modulation, and atypical system is outlined in Fig. 2.

Here we have in effect two modulators,each of which can impose on the carrier itsown tone whenever required to do so byits controller. At the receiving end thedetector output is fed to two tuned filters,one resonating to the frequency of the firstmodulator and the other to that of thesecond modulator. The receiver is thus ableto discriminate between signals originating inthe two modulators, and delivers separateoperating currents to the correspondingactuators.

"Multiplexing "This is an example of what telecom-

munications engineers call " multiplexing,"meaning the provision of a number of com-munications channels via one basic link.Although we have described a simple methodusing separate tones, there are, of course,others, such as pulse -time multiplex. Also,the reader will have justifiably assumed thatamplitude modulation was intended to betacitly understood, but other methods are per-fectly feasible, and in the writer's experiencephase, amplitude and pulse -width methodshave all been used.

We now know how to control the position ofone or more simple actuators simultaneously,but on closer inspection it must be admittedthat the scope of control of which our systemis capable is extremely limited. Like the

Controller2

Modulators

NEWNES PRACTICAL MECHANICS 273

direction. In this case a signal throughchannel t will turn the control to one side, 2and a signal through channel 2 will turn itto the other. In the absence of signals inboth channels the control remains stationary,so that any intermediate position may beheld by switching off both controllers whenthe required degree of movement has beenobtained.

For Model Power BoatsThis system finds favour in model power

boat practice, in which it is used to controlthe rudder, and where a relatively slowmovement of the control is less importantthan accurate position setting. It appearsmost convincing to the onlooker but doesnot " handle " as realistically to the opera-tor as systems using a true position -controlservo -mechanism. It has also been usedprofessionally in model aircraft designed forresearch work.

If we can be satisfied, however, with amere two- or three -fold increase in thenumber of positions our elementary systemprovides it is possible to obtain results quiteacceptable, for model work at least, by acertain amount of re -design to our simple" bang -bang " actuator.

In Fig. 3 our actuator solenoid S attractsa small armature A attached to the rockerR, which is pivoted as shown and carries atits extremities two pawls Pt and P2. Inthe absence of signals this rocker is keptfirmly against its backstop by means of asuitable spring. W is a star -wheel pivotedat its centre and subjected to a constanttorque applied in the direction of the arrow.In the absence of signal, and therefore ofenergising current, the pawl Pr prevents its

R.F. Amplifier.Actuator

Controlledcomponents

ActuatFilters Output

Fig. 21-Outline of the two -channel control system.,

Transmitteri

clutch on a cheap car, it is a two -positiondevice and is either " in " or " out." Thisis perfectly adequate for some applicationsand where extreme simplicity is called for,as in model aircraft work, in which it issometimes used, and it will enable such amodel to be steered straight ahead or, say,sharp right at will. In model aeroplanejargon it is often known as a " bang -bang "system, for reasons obvious to anyone who hasever watched it work.

"Proportional Control"The next step, then, is to obtain a finer

degree of control over the movements ofthe actuator, and if in fact we carry ourrequirements to their logical conclusion wewould like to make it take up and hold anyextreme or intermediate position corre-sponding exactly to settings made to thecontroller. With more complex equipmentthis can be, and is, carried out, and sucharrangements are known as " proportionalcontrol " or, occasionally, " infinitely vari-able " systems. In their most advancedform they comprise true position -controlservo -mechanisms, usually working upon theprinciple of the " self -balancing bridge."

A satisfactory compromise between theexacting performance requirements and theusual calls for simplicity, reliability andlightness can be achieved by replacing thetwo actuators of Fig. 2 by relays arrangedto switch a steering motor to the required

Receiver

rotation, but as soon as the solenoid is ener-gised pawl Pr is moved downwards awayfrom the bottom limb of W and W is drivenround 45° by the applied torque. Its furthertravel is prevented by P2, which has mean-while engaged the next limb, but as soon asthe solenoid is de -energised a further 45°rotation takes place. Thus, for every com-plete pulse of current W rotates through90'.

Let us now imagine that E is a pinmounted eccentrically on W and engagingin a slot in the tiller bar T. In the positionshown in Fig. 3 the rudder is hard to theleft, and after the passage of the next pulseof current will clearly return to neutral asthe pin E moves from position 2 to 3. Infact, we may deduce that over the completecycle of events, when E moves under theinfluence of four consecutive pulses of currentaround positions I to 4 inclusive, the rudder

Backstop

Pivot

©riveto

rudde,

Fig. 3.-Sequence-type three -position actuator.

will move from neutral to left, then back toneutral, to right, and finally to neutral again.We can thus make the rudder take up anyone of three positions, and obviously thesystem may be developed to include anydesired number of positions.

Notice, however, that only one channel ofcommunication is required, since we are con-trolling one actuator and using one controlleronly. We have succeeded in making oneactuator perform three different operationsin a known sequence, but, of course, it is upto the operator at the controlling end toremember which response was obtained tohis last command and to deduce from thisand his memory of the sequences whichresponse will be forthcoming next-appar-ently he is unable to make, for instance, tworight turns in succession. With practice,however, it becomes quite easy to flickthrough the two or three unwanted positionsof the sequence with an actuator of the typedescribed so that the required movementappears to be direct.

Operating TorqueA furthei important design point is also

brought out in Fig. 3. We have stated inour description that a constant torque isapplied to the star -wheel, the function ofthe rocker and pawls being to control itsmotion, not to produce it. The operatingpower of the system thus depends only onthe applied torque, and we need only justsufficient power from the receiver and relayto operate the rocker arm. This is a highlydesirable state of affairs in the case of lightmodels, where the system is most often usedand where the receiver output power is ofthe order of a few milliwatts. It enables theenergy needed to operate the system to bestored in a lighter and more effective formthan is possible with electricity ; batteriesof all sorts are notoriously heavy for theamount of energy stored, and no electricmotor is yet known which can deliver asteady torque without continuously consum-ing current. In practice the torque is usuallyprovided by a specially -designed clockworkmechanism, or, more simply, by a twistedskein of the familiar model aircraft drivingrubber. An obvious disadvantage of thismethod is that it can provide only a limitednumber of movements for one winding ofthe driving mechanism, but the system iswidely used in model practice and hasattained a great degree of popularity. It isthe system which is most likely to be foundin commercially -made model control equip-ment, which perhaps speaks for itself.

FOR ENGINEERSBy F

Screw Thread Tables, 51-, by post 513.

Refresher Course in Mathematics, 816,post, 91-.

Gears and Gear Cutting, 61., by post 616.

Workshop Calculations, Tables and Formulae,by post 616.

t From GEORGE NEWNES, LTD., TOWER

by

6!-,

J. CAMMDictionary of Metals and Alloys, 1016, by post III-.

Wire and Wire Gauges (Vest Pocket Book), 316, bypost 319.

Metric and Decimal Tables, 316, by post 319.

Screw Thread Manual, 61-, by post 616.

HOUSE SOUTHAMPTON STREET STRAND, W.C.2.


HE mineral gypsum is one of the world'scommon commodities. Almost everycountry has its own natural resources

of this nowadays indispensable material.Available figures over the last quartercentury show that the world's annual outputof gypsum products has centred around tenmillion tons, the average British productionfor home consumption averaging about onemillion tons per year.

Clearly, therefore, gypsum is an impor-tant substance. It is a very interestingmaterial, also, viewed from a scientific aspect,and its technical and everyday 'applicationsare almost without number.

It must have been in very ancient timeswhen someone made the chance discoveryof the fact that this white mineral earth,after it had been powdered and heated, couldcombine with water and set to a solid mass.Yet such a discovery forms the basis ofall our present-day common plasters, andjust because the large natural deposits of

. this mineral at Montmartre, near Paris,were employed locally for the extensivemanufacture of a hydraulic or water -settingplaster the prepared material somehow orother obtained for itself the name of plasterof Paris, although, apart from this chanceassociation, the material has nothing what-ever to do with the French capital.

Gypsum is nothing more nor less thancalcium sulphate, CaSO4. Its name is aGreek one, meaning chalk, although in actualfact it has nothing in common with chalk,which is calcium carbonate, apart from itssuperficial white appearance.

Raw GypsumNative gypsum occurs in a loose com-

bination with water. Its chemical formulais CaSO42H2O. Even in this " raw " stategypsum has a number of important uses.Under the guise of terra alba (white earth)or " mineral white," it functions as an im-portant filler for paper and cotton fabrics,as an " extender " for distempers and paints,as a dusting powder for scattering in minesin order to keep down explosion risks, asan inert medium or diluent for the modernhighly -potent insecticidal powders of the" Gammexane " type, as an ingredient ofPortland cement in order to retard its set-ting -time, and even as a means of improv-ing (or " Burtonising," as it is called) thewater used for the brewing of ales.

When the gypsum is found in clean, nicelycoloured, fine-grained masses it is calledalabaster (the name is said to be derivedfrom Alabastron, a town of ancient Egyptwhere there were quarries of this material),a mineral which is used mainly for orna-mental purposes. There is, also, a crystal-line variety of gypsum which is almosttransparent and which is called selenite,from the Greek selene (the moon), in

Modern Plasreference to its soft,pearly lustre.

It is, however,after the commonnative gypsum hasbeen converted intoplaster, or " plasterof Paris," to give theprepared material itsmore conventionalname, that it attainsits most importantuses.

Plaster of Paris isvery simply manufac-tured. The nativegypsum is screenedfrom all other earthymatters. It is roughlycrushed, dried to re-move obvious mois-ture, and then groundto a fine, impalpablepowder either betweenstones (the old-fashioned method) orin a revolving cylinderknown as a " tube mill," in whichsteel balls pound the white material to anextremely small particle size.

Next comes the " boiling " of the pow-dered gypsum. This is a curious term touse for the treatment of a powder, but thepowdered gypsum is charged into iron con-tainers called " kettles," in which it iscarefully heated and in which the escapeof the chemically combined water gives thegypsum powder the appearance of a boilingliquid.

This boiling must be very carefully done,to which end the material is agitated during

The Manufacture of Plaster of Pari!

A slow -speed revolving steel cylinder or " tube mill " used for the finegrinding of industrial materials such as limestone and gypsum.

hard the whole of the process. The temperaturemust be kept around 13o deg. C. If itis allowed to rise considerably above thismark the whole of the water contained inthe gypsum is driven off and the materialis said to be burnt. As such it consistsof anhydrous calcium sulphate, CaSO4, andit becomes useless for ordinary plaster pur-poses since it will only recombine withwater very slowly and with the greatestreluctance, requiring days or even weeks forits setting.

It is important, also, to see that only veryhigh-grade raw gypsum is used for plaster

manufacture, for ifthe crude material iscontaminated withother substances, suchas chalk or china clay,which do not take partin the controlled de-hydration, these inertmaterials will remainin the finished plasterand will thus dilute it,taking away from itserviceability a n dstrength.

How Plaster SetsThe precise chemi-

cal and physicalmechanism underlyingthe setting of plasterof Paris is not difficultto understand. Letus consider it in this

(Above) Stout wirenetting gives addi-tional strength to aconcrete road. (Left)Painting a plasterstatue with a solutionof wax in benzene toimpart a surface -lustre to the cast.

manner :We have already seen that the composi-

tion of native gypsum (calcium sulphate) isrepresented by the formula CaS0,21120.In this formula the " H20" represents thewater content of the material, and theexpression "2/120 " signifies that in nativegypsum each molecule of calcium sulphate,CaSO4, is combined naturally with twomolecules of water. Hence we obtain theformula, CaS0,21120. Chemically speak-ing, this is the dihvdrate of calcium sulphatesince it contains two molecules or units of

- combined water.

June, 19 51 NEWNES PRACTICAL MECHANICS 275

its Uses

Gesso,

ProductionBy J. F. STIRLING

a simply -made plaster material which is produced by slakingplaster or whiting with glue water.

Now, when this dihydrate (which isnatural gypsum) is heated to a temperaturearound 13o deg. C., a portion of its combinedwater is driven off, and thus it is convertedinto what is known as the " hemihydrate,"having the formula CaS0J-120. Thishemihydrate is the white powder which weknow as plaster of Paris.

The actual " transition temperature " atwhich the dihydrate changes into the hemi-hydrate of to8 deg. C., that is just over theboiling -point of water,but, in practice, tomake sure of theaction being complete,the plaster of Paris ismanufactured at about13o deg. C.

You see now whythis matter of tem-perature is so import-ant in plaster manu-facture, because if13o deg. C. is sub-stantially exceeded theremaining water int h e hemihydrate(plaster of Paris)begins to be drivenoff, so that ultimately(and very definitely attemperatures abovezoo deg. C.) there isproduced the com-pletely dehydrated cal-cium sulphate, con-sisting of CaS0.1and nothing more.

AnhydriteThe completely dehydrated material is

known as " anhydrite." Although it isuseless for plaster purposes, it is becominga substance of increasing industrial impor-tance, for which purpose it is sometimesmanufactured synthetically. It can also beobtained from natural sources. Its industrialimportance results from the facts thatsulphur for the manufacture of sulphuric .acid can be obtained from it, and that bytreatment with nitrogen it can be turned into" nitro -chalk," a valuable fertiliser, and also

into ammonium sul-phate, another fertil-iser, by reaction withsynthetic ammoniamade from the nitro-gen of the atmo-sphere.

We must, how-ever, resist the temp-tation to exploret h e s e interestingchemical by -waysand return to ourmain theme of plas-ter of Paris and itssetting mechanism.

When the calciumsulphate hemihy-drate, CaSO4H20is treated with anappropriate amountof water, it not onlyabsorbs the waterbut it chemicallyretains it. That isto say, the addedwater is not merely

mechanically mixed with the white powderbut it actually enters into chemical combina-tion with it. The result of this process isa reconversion of the hemihydrate, CaSO,H20,into the dihydrate, CaS042}120. Such is theprinciple of the setting of plaster of Paris.

Good plaster of Paris is not a pure sub-stance in that it does not consist solely ofthe hemihydrate. The latter makes up itsgreatest bulk, but it also contains someunchanged dihydrate and a little of the corn -

(Above) Sectionalview of a plasterblock reinforced withhorsehair.(Right) Liquid pla-ster, which is merelya thin gesso, brushedover a wood panelto provide a smooth

- white surface.

pletely anhydrous or water -free calciumsulphate.

Now, the anhydrous calcium sulphate,although only sparingly soluble in water, ismore soluble than the dihydrate, so that whenwater is added to plaster of Paris theanhydrous calcium sulphate partially dissolvesin the water and becomes converted to thedihydrate. This crystallises about the undis-solved particles of dihydrate in interlockingneedle -like crystals. The dihydrate whichresults from the absorption of water by thehemihydrate also crystallises in needlecrystals which interlock firmly and so giverise to the solid mass of " set " plaster. Itis probable that the unchanged particles ofdihydrate in the plaster form nuclei aboutwhich the re-formed dihydrate crystallisesand interlocks.

The setting of plaster of Paris is accom-panied first by a contraction of the mass ofmaterial, but this is followed by an expan-sion which is due to a change from thecrystal system of the hemihydrate into thebulkier crystal form of the dihydrate. Sothat, as a final result, the plaster expandsvery slightly on setting, a fact which makesit so admirably adapted for the taking ofsharp castings and for similar accurate work.

Retarding the SettingIf the water used for the slaking of the

plaster contains any substance which canpossibly interfere with the formation ofdihydrate crystals, such a substance willretard the setting and even actually preventit. All colloid materials have this retardingproperty because it is not easy for anythingto crystallise when it is interspersed withjelly -like matters. Hence, if we dissolve glue,gelatine, starch, gums 'or any similar sub-stance in the slaking water of plaster of Paristhe setting of the plaster will be retarded inproportion to the amount of colloid which ispresent. If an excess of such colloid materialis present the plaster will not set at all.

The Romans must have had some know-ledge of this property for it is reported thatthey used animal and, maybe, human bloodto slow down the setting of their plasters.

Conversely, if we dissolve in the plasterslaking water anything which will tend tocrystallise, the internal crystallisation of theplaster, and therefore its setting, will bespeeded up. Thus, materials such ascommon salt (sodium chloride) will acceleratethe setting of plaster. Indeed, anythingwhich materially increases the solubility ofthe gypsum will do this. Weak hydrochloricacid, acetic acid, tartaric, phosphoric andcitric acids all reduce the setting time ofplaster, but borax and alum retard the setting.

We have seen that when native gypsum isheated to about 200 deg. C. it becomes con-


Horsehair gives additional strength

verted into anhydrous calcium sulphate,CaSO4, and in this condition is said to be" burnt." Such material, which, as we havefurther seen, may take long periods to set, issupposed to contain calcium oxide, CaO(quicklime), in addition to anhydrous calciumsulphate, the lime being dissolved in thesulphate And thereby forming a " solid solu-tion." This material has been used underthe title of " flooring plaster."

If the gypsum is heated to about 600 deg.C. not only is it completely dehydrated toanhydrous calcium sulphate, CaSO4, but theproduct refuses to reabsorb any water. Thematerial, consequently, will not set, evenafter a prolonged period, when mixed withwater. It is said to be " dead burnt," inwhich condition it is without practicalinterest.

" Hard Finish " PlastersWhen native gypsum is calcined at red

heat and the resulting anhydrous calcium sul-phate is immersed in a bath of alum solutionand again calcined and powdered, the pro-duct, when slaked with water, sets compara-tively slowly. In this condition, the plasteris known as Keene's Cement. It is one ofthe "hard finish" plasters, used for " skim-ming " or surfacing walls. A peculiarityabout it is that the partially -set cement maybe reworked with water and that, in thesecircumstances, it will set as well as if itsfirst setting time had not been interrupted.

What is known as Martin's Cement resultswhen sodium or potassium carbonate, as wellas alum, is used in the above process andthe subsequent reheating is done at a higher

A microscope view of asbestos powder, showingthe fibrous character of the material which aidsthe interlocking and " keying " of plaster

particles.

o concrete.

temperature than thatused for Keene'scement.

Parian Cement ismerely another ofthese " hard finish "plasters based on gyp-sum. It is made bytreating the gypsumwith borax solution ina similar manner tothe above.

Plaster of Paris,a f ter setting, ischaracteristically por-ous. It can, how-ever, very readily beimpregnated withagents such as size orglue solution, or withsolutions of variouscommon waxes whichnot only give it in-

creased strength hut which allow its surfaceto be painted on without subsequent absorp-tion of the paint medium.

Plaster casts are notoriously brittle. Anyof these impregnation processes at oncedecreases the brittleness of the plaster, as will,also, the incorporation with the plaster ofa fibrous material such as asbestos powder.

(Above) A network of leaf -like crystalsor " spheralites," similar to those whichform in a setting mass of plaster of Paris,and by whose continual spread and inter-locking the plaster mass is given solidityand coherence. (Right) Replacing missingpieces in a plaster picture -frame mouldingby means of a plastic stick of gesso.

For a really effective reinforcement of amass of plaster, and for making it practi-cally impossible to fracture the plaster masscompletely there is nothing like horsehair,the hair being padded or otherwise forcedinto the plaster mass in its wet stage.

Steel wool can be used for the abovepurpose, but there is a risk here of thesurface being- discoloured, particularly underconditions of dampness. It can, however,give an enormously tough plaster mass.

When slaking plaster of Paris it is betterto add the plaster to the water than thewater to the plaster. Estimate the necessaryquantity of water required. Then shake theplaster into the water by degrees, stirringcontinuously. Good plaster should have theconsistency of thick cream. It will usuallyset solid within ten minutes, although thenature of the water has an influence on theprecise setting time. It is not safe to removea plaster from a mould under half an hourfrom its apparent setting.

To prevent the plaster from adhering to

the side of the mould, the latter may be oiledor greased, but, in the case of statue work,where the grease would stain the surface ofthe casts, it is a better plan to brush themould surfaces with white of egg, and, afterdrying, to apply to the same surfaces a verythin cream of china clay mixed up instrong soapy water.

Good GessoWe have noted that when plaster of Paris

is slaked with glue or gelatine water its set-ting can be delayed or completely prevented.If, however, sufficient glue is used, the glueitself will harden, binding the plaster massinto a hard, unyielding mass.

There is, however, no need to use plasterof Paris for this purpose. Common whitingwill do equally well and the product is knownas " gesso " (pronounced " jesso "), which isan Italian word for plaster.

Although gesso may not contain anyplaster of Paris, it is excellent stuff foramateur moulding work, but it has nothinglike the quick setting time of true plaster ofParis and may, indeed, in large masses, re-quire up to a week to harden out.

To make good gesso, dissolve r part ofhigh-grade glue in 52 parts of water. Addto this a.few drops of carbolic acid to prevent

the glue from going mouldy and thus des-troying itself. This is the stock " gessosolution."

As the gesso medium or " aggregate " youcan use whiting alone, or whiting admixedwith plaster of Paris, either or both withor without additional admixture of a colour-ing matter such as lampblack, red oxide orochre.

For the best work, the most satisfactorygesso aggregate is whiting mixed with abouta quarter of its bulk of zinc oxide.

To make the gesso, all one has to do isto warm the gesso solution and to stir intoit sufficient gesso aggregate to make a stiffpaste which, when moulded between thefingers, will remain " put " and will notflow.

If the gesso is made to a thin cream con-sistency it may actually be brushed on tosurfaces such as wooden panels, walls, fabrics,etc., thereby providing a coating which canbe painted or drawn on.

June, 1951

MakinNEWNES PRACTICAL MECHANICS 277

a One -inch MicrometerConstructional Details of a Serviceable

Instrument for the Home WorkshopBy A. D. STUBBS

OF course, when you have finished themicrometer, you will find that thefirst job needing a " mic " is just

under 2 inches, and if you proceedaccordingly to make them in r -inch stepsyou will eventually end up with a boxfulof micrometers.

I did contemplate a larger one, to incor-porate r- and 2 -inch distance pieces,but as even a 3 -inch " mic " would notnecessarily be the limit, I decided on thesmallest size, and here it is.

Starting from zero, my design, Fig. t,can be improved upon, as the stirrup is justa little ungainly. If you can cast the com-bined body, stirrup and anvil in iron a lotof artistic possibilities will arise, but havingdecided upon a stirrup from kin. steel plate,I had to give myself riveting room, or elseresort to welding with the probability thatdistortion would occur.

The stirrup shown in Fig. 2 is machinedall over, the thickness being taken down to7/32in. Incidentally, the whole of theinstrument is polish -finished except the boresof the body and cap. I do not show anyrivet holes in the stirrup, because these are

And, by the way, allthreads should betapped in the lathe toensure alignment.

Centring on thishole, I turned themiddle portion downto kin. diameter, andthen got to work onthe two flat sides witha milling cutter. The7/32in. slots were re-moved in a series ofcuts with the slittingsaw, using the stirrup as a " go " gauge, andit is a nice hard push fit. To ensure that thejoint bedded right home, I slightly radiusedthe corners of the stirrup with a file., Theanvil was then parted from the body, leavingme enough metal to face the remote end ofthe body. To face the outside end of theanvil I used an end mill.

Pallet ScrewMy first pallet screw, Fig. 5, was a

cheeseheaded setscrew, with the end turneddown to remove the slot, the remainder of

the head having a coupleof flats milled off for aspecial spanner, but laterI made another from kin.silver steel, with the outerface of the head fulldiameter, milling flats onthe inner part of thehead.

Fig. 6 shows the silversteel screw. The onlypoints to watch here arethat the thread must beas perfect as possible andthat the business end ofthe micrometer screw

must not be otherwise than dead flat, and at90° to the axis.

The cap and nut, Fig. 7, both came outof gin. diameter mild steel, the nut alonebeing knurled, for appearance sake, and thencame the marking of the divisions.

I selected the kin. Whitworth screwingfor the sake of its twenty threads per inch,so the body marking divisions correspond.Setting up for screwing 20 t.p.i. I centredthe body, but without holding it for rotation,and put on my faceplate, to " drive " by.

Tooling the MarkingsA sharp -pointed vee tool was then set up

on its side, and the longitudinal markingline cut .002in. deep by winding in my top -slide feed. The same tool was then changedover to normal position, and the topslide setwith the tool tip against the left-hand endof the jin. diameter of the body.

Fig. 1.-Side elevat'on, plan and end view.

better drilled from the anvil and body. Thestirrup was turned up on the faceplate, as acomplete circle, and afterwards cut with aslitting saw. I still keep coming across thediscarded segment, which might come inuseful one day !

Anvil and BodyThe anvil and body, Figs. 3 and 4, are

made from a Sin. piece of tin. black mildsteel, turned down to 29/32in. diameter, thenext operation being to mark off and drillthe offset main hole, with the object ofmachining the slots for the stirrup beforethe two component pieces were parted.

In their Siamese twin state, the anvil layon the threaded end of the body, enablingme to drill 17/64in. from the other end fort-iin. depth. The kin. Whiporth tappingdrill followed for another 9/16in. then a No.43 drill went through to give me a tappingsize for the eventual Bin. Whitworth thread.

NIIIMIII /1/11/11/111M////,

7 NIMIIIIIMIM/NNI

o64._ 32

4 32

4-1 whit

6

Fig. 4.-Section and Fig. 5.-Detailend view of Cody. of pallet.

6 r 81

Fig. 2.-Stirrup

16

32 32

3.-Section andend view of anvil.

The finished micrometer.

To ensure taking up all gear teeth, bear-ings and any other sources of slack, I gavethe faceplate two complete turns by hand,backwards, marked the faceplate so that Icould repeat 360° precisely, and then fed inthe tool to touch my longitudinal line, thepoint being about .002in. below the surfaceof the body. A hand twist on the lug endof the body gave a perfect zero marking,full length, as shown in Fig. r.

The remainder is easy. Withdraw thetool, turn the faceplate once precisely, windin the tool, another hand twist (a short one

-t,2.1-;1

111111601M1

331--64±_

16

111101011111

Fig. 6.-Screw.

41-.116

Fig. 7.-Sections of

16

1,-; Whit -.1

cap and lock -nut.

this time), and there's another fiftythousandths marked up. Be careful not toturn the faceplate more than 360'. If youdo, it will be necessary to go back half aturn, to ensure taking up all the slack.

To mark out the fifty divisions on thebevelled end of the cap, I used the sameprocedure, with the change wheel ratioreversed. As a point of interest, I have adial on the tailstock end of my leadscrewwith a peripheral scale divided into 125millimetres. The mm. just don't mean athing except that as my leadscrew is8 t.p.i. they are to me each .00t in. This isprincipally to give me a fine reading whenfeeding with the leadscrew, but geared up tothe mandrel it gives me practically any divi-sion I need.

For the cap, I set the cross -slide for taperturning 20°, at which angle the cap hadbeen bevelled, and used the same sharp -pointed vee tool, again on its side, cutting a.002in.-deep mark at each fiftieth of a revo-lution, each tenth division being longer. Toavoid the amateurish mess I inevitably makeif I try to etch figures, I used the same tool,cross -slide reset to normal, to cut one, two,three and four cuts respectively at each tenthdivision on the full diameter of the cap. Theun.narked tenth division is my zero, as in theplan, Fig. 1.

(Continued on page 282)

278 NEWNES PRACTICAL MECHANICS

WORLD ofMODELS

By "MOTILUS"

The Production of Scale Models : A Fine Model Cargo Vessel : Architectural Models

June, 1951

IT is often interesting to see behind thescenes and watch the production ofscale models, whether being made by

the skilled hands of craftsmen or in the pro-cess of machine production, whereby scalemodels can be put on the market at lowerprices than the hand -made craftwork.

Mass-produced ModelsEven mass -production in the model world

requires a large amount of skilled labour.The designer, the tool-maker the precisionworker on small parts and the experts onassembly and final testing all have to playtheir part, and this is particularly so in themanufacture of model railways, now souniversally popular. Gauge 0 or ascale of 7mm. to aft., is still the size mostin demand for the model railway hobby, asit is suitable for either clockwork, electric orsteam propulsion. A review of the processesinvolved in the production of the ready-made gauge 0 models that can be boughtto -day may interest readers.

First, the locomotive, which has to bedesigned in suitable model form, based on anactual prototype. In doing this the designerhas to bear in mind that the finished locomo-tive may be fitted with either a permanentmagnet unit, with electric power collectedfrom a centre rail on the track, or with aclockwork mechanism, when only hand -winding is necessary ; or the most realisticmethod of steam propulsion may be used,generally by means of a cylindrical boilerheated by a methylated spirit lamp.

When drawings are complete the mainlocomotive body parts are stamped out ofmetal, usually tinplated steel. If the quan-

tity to be produced is large, the tinplatesheets are colour -printed first, then punchedout and assembled. This avoids the paint-ing process, except for wheels and othersmall parts, which are hand painted. Whenonly small quantities are required, however,printed tin is not used, and the locomotivehas to be entirely painted and lined by hand.

The Press RoomFirst operations, then, take place in the

press room, where the various sections arepunched out from tinplate sheets or printedtinplate according to the type of locomotive ;the mechanisms for electric or clockworkpropulsion are made in another department.Eventually all parts come together in theassembly room, after being painted where

necessary. Then the finished model is readyfor testing.

The illustrations, Figs. r, 2 and 3, showsome of these operations in a Northamptonfactory, where models are made.

Rail and paints for ready-made track can,be pressed out of tinplated steel, which isless expensive than using brass or steel railof standard bullhead section and buildingone's own track with cast metal keys. Thelengths of track are joined by means of slip-on fishplates.

Except when more expensive rolling -stockis concerned, coaches and wagons are de-signed and printed on tinplate, ready forstamping out and assembly in a similar wayto the locomotives. This method, however,cannot be used when much detail work is re -

Fig. 2. Microscopic examination of parts of the mechanism of a gauge o model locomotive.

Fig. r. Manufacturing model locomotivesafter painting, but before final assembly, thenumber and British Railways cr'est are applied,by means of transfers, to the model locomotive

and tender respectively.

quired, which necessitates hand work, in -eluding painting.

All parts of model railway equipment arethoroughly tested before leaving the factory.The locomotives receive tests on the track,whether they are clockwork, electric or forsteam propulsion.

Many railway accessories, such as signals,buffer stops, water towers, bridges and rail-way stations can be made on a similar prin-ciple to that described above, when mass-produced.

Of course, the whole procedure is quitedifferent from that used for hand -mademodels, which are made by very skilled .

craftsmen, who have suitable tools for thework and use sheet metal, castings and othermaterial for making small fittings. Thegeneral improvement in the making of model


design and appear-ance. Their steeldecks are painted red,superstructure is allwhite, and the hullsare aluminium andred.

The illustration Fig.4 is a model of thePathfinder to a scaleof 32ft. to sin. Itshows clearly theunique design, witht h e superstructureastern, and the long,level deck amidshipsalmost entirely free of

Fig. 3.-Assembly work on gauge o modellocomotives, after they have been painted and

lined.

locomotives, railway rolling -stock and otherequipment has resulted in the hobby becom-ing more universally popular.

Model Cargo Vessel " Pathfinder"Two new vessels were ordered last year

from Messrs. R. and W. Hawthorn, Leslieand Co., Ltd.,by the Pan Ore SteamshipCompany of .S.A. The first one to com-plete her trials was Pathfinder, and both sheand her sister ship, Prospector, have beenspecially constructed for carrying bauxite.There is no cargo -handling gear on board

Fig. 4.-A model of the Pan Ore Steamshipconstructed for carrying bauxite. This model is

collection belonging to Messrs. Wm.

with the exception of winches for generalcargo, as the ore is unloaded by grabs work-ing from the shore.

The Pathfinder has an 'overall length of447ft., moulded breadth 6oft., and she hasa mean draft of 2oft. Tonnage- is 7,730and displacement 11,173 tons. Her main,diesel engine is of the standard Doxfordopposed -piston type, constructed by the ship-builders at their St. Peter's works.

It is interesting to note that the air-con-ditioning and ventilating arrangements areperhaps the first of their kind carried out ona large scale. They were designed by theNorris -Warning Co., Newcastle -on -Tyne.Bauxite creates a large amount of dust'during loading and unloading and the air-conditioning and ventilation of machineryspaces can continue during these operations,as well as when the ship is under way. Allaccommodation is air-conditioned from acentral plant, which also filters the air andeliminates bauxite dust.

Thus the Pathfinder and 'Prospector aretwo most interesting modern vessels in.

Company's " Pathfinder," a vessel speciallyto a scale of 32ft. to tin. and is part of theHarvie & Co., of Birmingham.

deck gear. This model is one of severalhundred ship models made for Messrs. Wm.Harvie & Co., Birmingham, by a well -known -model -making firm. I understand a selec-tion of these models will be on view in theshipping section of the Festival of Britain,on the South Bank site,. in London.

Packaging ExhibitionEarly this year the Second National

Packaging Exhibition was held in the EmpireHall, Olympia. In conjunction with this;and taking up the whole of the ground floor,was the Metal Containers, Ltd. -Van LeerExhibition. Main feature of this extra-ordinary display was a mobile, metal drumfactory, in which there is a separate vehiclefor every machine, including a car fittedwith a generator, giving . out zoo KVA.Other cars provide living accommodation forstaff and management and a comprehensive ,canteen, so that the different components,when together, combine to make a completemanufacturing unit. The Van Leer organisa-tion is justly proud of the fact that this

mobile factory was driven into the EmpireHall at Olympia and within twenty-nineminutes was producing finished oil drumsfrom raw materials. Visitors to the Hallsaw oil drums wherever they turned! Drumsof all types and in various colours, applicableto different uses: even full-size glass drumsfor illuminated display purposes.

When this Van Leer Exhibition was beingplanned, the whole layout was modelled bytechnicians of Metal Containers, Ltd., beforeit was finally approved, and this model wasdisplayed in the Hall. There were also othermodels of various types on view, many ofwhich had been made by the firm of Bassett-Lowke, Ltd. Among these were someattractive block models of machines, finished

Fig. 5.-This'architectural model, to a scale of.nift. to sin., shows in entirety the EllesmerePort factory of Messrs. Metal Contaiao s,Ltd., where metal oil drums, canisters, etc., are

manufactured.

in white and strikingly displayed againstblack backgrounds at different points in theHall: also a working model of an Americandrum -making plant, to a scale of Bin. to'ft., a complete model of the company'sEllesmere Port factory and another of theSprings factory at Johannesburg.

The Ellesmere Port model (Fig. 5), to ascale of t21ft. t3 tin. (t/r5oth actual size),shows' the whole of the works there. Itincludes two American line, drum factories,one recently erected, and other buildingswhere small canisters, buckets, etc., aremanufactured. A railway serves the shedsfor transport and this is included in themodel, as, well as the road approaches forvans and lorries. The interiors of all build-ings in this model can be lit up, giving animpression of the factory as it would appearafter dark.

A NEW VEST POCKET BOOK

NEWNES METRIC &DECIMAL TABLES

By F. J. CAMM

3/6 or 3/9 by post fromGeo. Newnes Ltd., Tower House,Southampton St., Strand, W.C.2.

280

Oxygenating AquariumWater

SIR,-The alga whichbothers Mr. E. J.

Harmsworth is probably theinnocuous green variety, asopposed to the harmfulblue and pestilential brown types, and isusually seen in abundance after continuoususe of strong overhead lighting.

The simplest way to rid one's tanks of itis to leave all lights switched off for fourdays, subsequently reducing the wattage ofthe tank -lighting systems. A 6o -watt bulbover a tank 24in. x rain. x r2in. should beadequate.

If the tank in question is a cold -wateraquarium, perhaps it is situated by a window ?Should this be the case, steps should betaken to ensure that sunlight does notfall directly on to the tank, since this willpromote rapid growth of diatoms, etc.,causing " green water," and in any casethe eyes of fish are not intended by natureto receive light sideways !

The copper -sulphate treatment shouldclear a tank of alga in about 12 hours.

Snails, alas ! will not help in cleaning upalga, are incomplete scavengers, and canbecome a nuisance in one's tanks. If yourcorrespondent is a tropical -fish keeper heshould know that the " live -bearer " family(Paciliida) are gourmets for green alga,especially the Molliensias, and will keep itunder control.

Assisted oxygenation is not necessaryif the number of fish is kept to reasonablelimits, since oxygen is dissolved continu-ously, via the water surface, sufficient tobalance the tank, provided there is no over-crowding. (Bear in mind that cold -waterfish need far more oxygen than their tropicalcousins, bulk for bulk.)

Finally, I cannot understand the impliedobjection to the inclusion of plants as oxygena-tors, since the asthetic value alone justifiesthe presence in the aquarium of suchoxygenators as myriophyllum, sagittaria,elodea, etc.

Incidentally, green alga is a splendidoxygenator !-WM. E. HADFIELD (EastMolesey).

Home-made Wood -turning LatheSIR,-Many of your readers no doubt

find that the diametrical capacity ofthe usual wood -turning lathe is very limitedunless one can afford the more expensivetype, which is beyond the pocket of somepeople.

I have overcome this drawback by makingmy own machine, as shown in the accompany-ing photographs. It is made entirely ofwood-mostly packing cases-with the excep-tion of such essentials as bearings, bed -plate,etc. I now have a machine with which Ican turn up 2ft. diameter in the gap, 'ft.over the bed -plate and 2ft. Sin. betweencentres. The total cost, including the h.p.motor (temporary), was £12.

The bed -plate is of 4ft. x tin. channelback to back. Headstock is of 6in. x 2in.timber, and has a hollow spindle set in tripleball races with a gin. faceplate. The traverse,again of wood, is electrically operated andcontrolled by two very simple limit switchesat the rear. This is driven by a motor which


I obtained from an old vacuum cleaner andgeared down through a giainophone motor.The lead screw is lin. Whitworth, whichI had threaded on a pipe -screwing machine.

The controls, as seen on the front viewof the lathe, are, left to right : t. Isolator ;2. Traverse direction lever ; 3. Traversespeed control.

I have thoroughly tested this machineand find that it is very satisfactory. Itsweight is roughly 21 cwts.

June, 1951

they can do most of the things they thoughtotherwise impossible.

Incidentally, I have only one arm !-W. FLETCHER (Aberavon).

Law of GravitationSIR,-Concerning A. D. Joseph's curious

assertion (May issue) that " to resistand attract at the same time is impossible,"I would like to point out that action andreaction are equal and opposite ; that attrac-tion and resistance are equal and opposite ;that, in short, resistance to Mr. Joseph'sfrustrated apple is merely the obvious resultof attraction.

Perhaps he, unlike Newton, confuses theverbs " to resist " and " to repulse."-S. F. W. H.zurr, B.Sc. (London, E.).

SIR,-I would presume that A. D. Joseph(Epsom) is the kind of person who thinks

he can lift himself in the air by standing in abucket and pulling at the handle.

The centre of gravity of any object, surely,is the centre of its mass, and therefore it isthe core of the earth attracting the apple hementions. In theory the apple would continue

Two views of Mr. W. Fletcher's wood -turning lathe.

The reason for my sending you this letteris this : I have often wondered how manyof your readers have given up their hobbybecause of loss of limbs in the late war ?I have met many, and I am pleased to saythat, after spending some time with them,

to the centre of the earth. With regard tohis version of the Law of Gravity, it shouldbe pointed out that if attraction were notpresent between two bodies there could beno resistance between them.-L. J. BRYANT(Rochester).

Aylesbury and District Society of ModelEngineersTHE March meeting of the society, held at

Hampden Buildings on the 21st, wasdevoted to a chat by Mr. J. L. Maskelyne.Mr. Maskelyne's talk could not be called alecture, for to do so would create a wrongimpression of Mr. Maskelyne. His chat wasliberally illustrated with photographs, and hehad some very expressive things to say aboutthe tinny commercial models and the freelance adaptations of prototypes with which weheartily agree. We would like to thank Mr.Maskelyne for an enjoyable evening.-Hon.secretary, E. H. SMITH, Mulberry Tree Cot-tage, Devonshire Avenue, Amersham, Bucks.

Ilford and West Essex Model RailwayClub

THE annual general meeting was heldrecently when the following officers

were elected for the ensuing year: Presi-dent, Mr. R. L. Riddle (who was dulyinvested with the badge of office by the retir-

ing president, Mr. J. A. Carter) ; President-elect, Mr. G. J. A. Baker ; Hon. treasurer,Mr. S. H. Gilding ; Hon. secretary, Mr.E. W. Cornell ; Hon. librarian, Mr. G. J. A.Baker ; Vice-presidents, Messrs J. N. Maske-lyne, W. J. Kohring, N. F. K. Fletcher,T. S. Lascelles, F. H. White, G. R. Dowand Mrs. M. R. Hardy.

The reports of the various officers and ofthe 0 gauge, 00 gauge, EM gauge andjunior sections were adopted, and the meetingrecorded its thanks to the local Press and themodel railway journals for reporting fromtime to time upon the club's activities.

The summer programme includes thefollowing events: June loth, 5o/5o sale ;July 18th, Mr. H. M. Sell (London Manager,Bassett-Lowke, Ltd.) ; September 5th, FilmNight ; September 22 -29th, Exhibition atIlford in connection with Festival of Britain.

Other meetings will be devoted to complet-ing the alterations to the exhibition layout,and it is hoped, with the kind permission ofthe owners, to arrange visits to the layoutsof Mr. W. S. Norris, Mr. Fleetwood Shawand ERG (Bournemouth), Ltd. A cordialwelcome is extended to new members.-E. W.CHAIN:ELL, Hon. secretary, 42, Lincoln Road,Forest Gate, E.7.


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232 NEWNES PRACTICAL MECHANICS June, 19 51

"Abingdon" Door SpragMARKETED by The Abingdon Rubber

Co. Ltd., 505, Kingsland Road,London, E.8, this fitment is specially suitable

for garage doors.Attached to t h elower part of a door,as shown in theaccompanying illus-tration, the sprag isoperated by a flick ofthe foot, and willhold doors in theopen position againstthe strongest wind.

o, The sprag is alsoparticularly usefulfor industrial andoffice buildings andin the home. Fittedinside a door it willgive added security,as the door cannotbe forced open fromthe outside. Thefitment is of heavyconstruction, t h edoor fixing being ofstout iron channel:the hardwood spragis spring -loaded sothat is snaps easilyinto the up or down

door position. A brightyellow finish makesthe device easy to

locate at night. The retail prices are cos.per pair, or 5s. 6d. each, post paid.Eyre Smelting Company's New

CalendarTHIS being Festival of Britain year,

many friends of the company will bevisiting London to see one or other of theexhibitions being held there. Many of themwill want to see other features of interest,and as there are a number of these within asmall radius of the firm's works, the companyhave made a new departure in the design of

The "Abingdon"

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their calendar, which they have just issued.The new calendar takes the form of a mapwith a coloured decorative border consistingof sketches illustrating some of the manyinteresting places within easy reach of theworks. For those who wish to visit theTandem Works, or the Aluminium Works atMitcham, the positions of these two factoriesarc shown, and details are given on thereverse side of the calendar of rail and roadservices from London.

Copies of the calendar are available tomembers of the engineering, foundry andallied trades while supplies last. Applicationshould be made on a business heading to theEngineering Sales Department, The EyreSmelting Co. I.td., Tandem Works, MertonAbbey, London, S.W.'s,.

Microid Flask ShakerTHE Microid silent shaking machine

accommodates up to four 50o ml.flasks, each half full of liquid. It can beplaced on the laboratory bench and does notneed permanent fixing. The power consump-tion is only 6o watts. It can be pluggedinto A.C. or D.C. lighting circuits, and iscontinuously variable inspeed from zero up to500 oscillations p e rminute. Its agitationcan be varied instantlyfrom a gentle slopping,useful for viscid solutionssuch as collodion, to aviolent cascade. In around bottom flask suit-ably adjusted, the liquidcan be made to swirlaround the flask on ahollow horizontal aids. Ina conical flask the liquidcan be made to rise spir-ally up the walls ; inreturning in droplets tothe bottom it is broughtinto intimate contact withthe gaseous phase and is

A Review of the LatestAppliances. Tools and

Accessories

effectively " aerated " for such purposes ashydrogenation. In the incidental dailylaboratory operations of dissolving and dis-persing solids, extracting residues, emulsify-ing oils, it abolishes the tedium of prolongedshaking by hand, saves time and acceleratesthe processes. If suitably supported it couldbe used for shaking flasks in a thermostaticbath. Since it reproduces so many differenttypes of agitation hitherto attainable onlyby hand, it may be termed a " wrist -action "shaker.

The casing of the shaker is a heavy, box -shaped iron casting mounted on four vibra-tion -absorbing rubber feet. Running onbearings through the casting there paeses afin. diam. spindle fitted at each end withsplit -sleeve non-ferrous casurgs to which arebolted four Griffin four -six clamps. Withinthe casing is mounted a rho -h.p. universal,ball -bearing fan-c000led motor which, bymeans of an eccentrin coupled with a sturdylink motion, causes the spindle to oscillatethrough a small amplitude. Further particularsand prices can be obtained from Griffin andTatlock, Ltd., Kemble Street, Kingsway,London, W.C.2.

The Microid fas:z shaker.

Books ReceivedGem Testing. By B. W. Anderson.

Published by Heywood & Co. Ltd.246 pages. Price 2IS. net.THIS book, which is a fifth edition, aims

at showing the ordinary jeweller anddealer, in the simplest possible manner, theeasy, scientific tests available to him fordiscriminating with certainty between onestone and another, and between real stonesand their substitutes. Since the earlier editionsof this work appeared there have been startlingdevelopments in the production of syntheticgem -stones. For instance, Verneuil's " flamefusion " method, now 50 years old, has beeningeniously modified to yield a new gem -stone-synthetic rutile-and synthetic etar rubiesand sapphires. Full descriptions of the newmaterials, and of other developments insynthetic, imitation, and " faked stones aregiven in this volume, together with sug-gestions as to how they may be recognised.Among the other extensive additions to thebook is the description of a new method ofusing the refractometer, which was firstsuggested by Mr. Lester Benson, of theGemological Institute of America. By usingthe " distant vision " technique, the gem-mologist can obtain refractometer readingson curved surfaces, or on tiny faceted gemswhich .give no visible shadow -edge by normal

methods of observation. The chapter on thespectroscope has been re -written, and thewavelength tables extended. Several additionalminerals have been included in the summaryof gem species, and in the tables at the endof the book. There are also a good glossaryand index, and many excellent half -toneillustrations. Although the book is intendedprimarily for the use of those who trade inprecious stones, students and members ofthe general public who are interested in thesubject will find a wealth of information inthis authoritative work.

Motor Cycling Year Book, 1951. Compiledby Peter Chamberlain and the Staffof " Motor Cycling." Published byTemple Press Ltd. 186 pages. Price7s. 6d. net.FOR several, years there has been a need

for an annual review of all motor-cycling activities-technical developments,sporting events and the touring aspect. Thepurpose of this book is to fill this gap inmotor -cycling literature and to present acomplete record of the year's progress andevents, including chapters on technicaldevelopments, world specification tables, roadtests, motor attachmentst and touting abroad.The sports side is covered by a general reviewof racing at home and abroad, and there areindividual chapters on the world champion-

ships, records and record -breaking, reliabilitytrials, race results, Moto Cross, and speedwayracing. The book is lavishly illustrated.

A ONE -INCH MICROMETER(Continued from page 277)

To read the micrometer, the exposed divi-sions on the body are totalled, each being,of course, 5o thousandths, and to the quot-ient is added the cap reading above zero,4 tenths plus 2 being .o42in. As the .00 tin.divisions on the cap measure about 1/32in.apart the instrument is quite easy to read,even down to .000sin.Assembling

Assemble the body with its screw, capand nut, run the pallet screw into the anvil,then mount the stirrup.

Drill through the four 3/32in. rivet holesin the one setting, then use the same diameterbrass wire for rivets.

To set the micrometer, let the pallet screwbe half a turn short of home," then screwin the cap until the screw face just contactsthe pallet. Hold the plain portion of thescrew, and adjust ..the cap until the com-bined body -cap micrometer reading is zero,and at that point tighten the lock nut. Theinevitable slight inaccuracy created in takingup the cap thread slack is now corrected byadjusting the pallet screw. '

June, 1951

Announcing

"LINESIDE" KITS"00" Gauge

for Railway ModellersThese kits are ideal for the man whowould like to find out just where thefascinationlies in scenic railway modellingfor they enable him to make a start on asimple but satisfying 'ob at small expense.They contain printed card and woodparts, printed celluloid windows, de-tailed authentic plans, brick and tilebuilding papers. The first off arc

LARGE SIGNAL CABINWATER TOWERS (2 types in r kit) 219COUNTRY STATION 5/6PLATFORMS 2/9

Postage: Single kit 6d., two or more rod.

*The full MODELCRAFTLIST for 1951 gives details of morethan 603 plans, planbooks, kits and acces-sories covering every aspect of the model -maker's art, ships, aircraft, road vehicles,houses, etc. It costs II- post free andincludes a II- refund voucher for use inbuying Modelcraft goods.

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EACH ONLY 80/- Inclusive.

NEON LAMP BULBS. Suitable test in-struments etc. Low voltage A,C. workingwith S.C.C. fitting (Single/Pole Car Type),Size 45 mm. x la mm. diam. : 181- doz.

Incl.ROTARY TRANSFORMERS T31. Input18 v. D.C. 12 amps.: Output 220 v. 0.11 amps. ;and 7.2 v. 13 amps. Or converts to goodMains Motor for A.C. or D.C. 25!- incl.ELECTRIC BELLS. Made by WesternElectric. double gong with moulded case,loud tone direct from 2001250 volts A.C.,50 cycles. 15/- each, post 11-.CAUSTIC SODA. B.P. 98 per cent. (pure)flake. by leading makers, in 51h, tins at only7/6 per tin incl.FCRIEENED LEADS. lift. long. fin. diam.spade terminals each end. TechnicallyLerfeet. 3,6 each, nest 9,1.

LAMP BULBSMillion lamps. 150 types, for Projectors,Searchlights, Floodlights. Signal, Mines,Car, Aircraft,Yacht. Ship, Workshop, House,Miscellaneous, etc. All unused in originalwrappers at low cost. ld. S.A.E. for LISTS-3d. S.A.E. for RADIO ELE.2 LISTS.

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THERMOMETERSCAPILLARY THERMOMETERS Reading 0-100 deg. C., 21in. dialwith square flange, capillary lengths 10ft and very flexible. Guaranteedaccurate to I per cent. Designed for R.A.F. as an oil thermometer 27/6brand new. Post free,

AIR THERMOMETER Reading -30 to =-50 deg. C., 21in. dial withsquare flange, highly flexible 10ft. capillary and long bulb. Hasmany uses such as for refrigeration plants, ground temperatures, etc., 27/6brand new. Post free,

BRASS CASED THERMOMETER A precision instrument,mercury filled and reading +55 to -I 240 deg. F. With loop for suspension andoverhaul length of 121in. Brand new, nitrogen atmosphere above themercury gives great accuracy and all made by leading British instrument 0/6makers. Post free.

BLACK CASED THERMOMETER Spirit filled and brasscase heavily japanned to reduce radiation. Reads - 30 to 200 deg. F.and all made by British instrument makers of repute, I5in. long and 8/''with suspension loop, brand new, in wooden case. Post free,

LOW RANGE THERMOMETER Reads -50 to + 40 deg. C. andis a highly efficient instrument, brand new and made by Short and Mason, Ltd.,includes cover for bulb, which is at right angles to the stem. The bulbend can be inserted into a refrigerator or through a wall so that readings 15/_are taken outside. Post free,

PULLIN MOTOR Pullin electricmotor, designed for Admiralty use on 20volts D.C., but will run on 12 volts -24volts D.C. and also on A.C. current with -out rectifier, but with transformer giving28-30 volts, brand new and packed in strongwooden box. Mounted on brass base plate4in. x Sin, with 4 corner fixing holds.Motor dimensions 2in. x 2in. x Sin. andshaft is fitted with brass gear -wheel. Twospeeds obtainable by shorting across theshunt. Carbon brushes readily adjustableand the whole gives " great power " in asmall space (about 1116 h.p.), this offercannot be repeated and we fully guaran-tee every motor. Each motorwith maker's name -plate 22/6thereon. Pest free,

BROMIDE PAPERBRITISH BROMIDE PAPER by

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SMALL BLOWER 12 volt D.C.with 3)in. volute. Easily fixedand with many applications. 22/6British made. Post free,

AERO - SPARES CO., (DEPT. 121), 71/71, HIGH HOLBORNLONDON, W.C.I. Telephone : AMBassador 287112 (all depts.).

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" First-class " MindsTo -day trained minds are more

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283

GALPI N'SELECTRICAL STORES,

408 HIGH STREET, LEWISHAM,LONDON, S.E.13.

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Terms :

CASH WITH ORDER. NO C.O.D.EARLY CLOSING DAY THURSDAYALL GOODS SENT ON 7 DAYS'

APPROVAL AGAINST CASHELECTRIC -LIGHT CHECK METERS,cuarterly type, for sub -letting garages,apartments, etc., all fully guaranteedelectrically for 2001250 volts A.C. mains,50 cys., I ph., 5 amp. load, 1716 each ;10 amp. load, 201- each ; 20 amp. load, 251 -each ; 50 amp. load, 3716 each ; carriage21- extra on each ; special discount of10 per cent. on quantities of one dozenOr more.EX - RADAR MAINS TRANS-FORMERS. 230 volts 50 cycles Input4 kV or 5 kV. OUTPUT with 3 L.T.s6.3 v. 2 a., 2 v. 2 a., 4 v. I a. These trans-formers are in oil, new, boxed. [313/ -each, carriage 716.MAINS VARIABLE RESISTANCES.14 ohms to carry I to 4 amps, 1216 each.0.4 ohms to carry 25 amps, 101-, 1,500ohms to carry 0.45 amps, 22/6.DUCOIN VARIABLE TARIFFELECTRIC LIGHT Id.11s. SLOTMETERS, all fully guaranteed 2001250volt A.G. mains 5 amp. load, 4216 each,carriage 216 ; 20 amp. load, 5716 each,carriage 216.ROTARY CONVERTERS, 24 voltsD.C. input, 50 volts 50 cycles, I ph, at 450watts output, complete with step-upTransformer from 50 to 230 volts, 01101 -each, carriage 101-, condition as new.ROTARY CONVERTER, EX -NAVAL, well-known makers, 100 voltsD.C. input, 230 volts 50 cys. I phase at 250watts output, capable of 100 per cent.overload, weight 1001b., condition as new,E1011010 each, carr. paid.POWER TRANSFORMER AUTOWOUND, voltage changer tapped 0,110, 150, 180 and 230 volts at 1,600 watts,65151- each, carriagewatts, E6151- each, carriage 3!6 ; anothertapped 0, 110, 200, 230 volts at 350 watts,at 4816 each, carriage 21-.EX-R.A.F. MICROPHONE TESTERS.These contain a 2in. scale 0 to 450 micro -amp. meter shunted to I mlamp., calibrated0 to 10 volts, moving coil, complete with1 mA rectifier, " mike transformer," etc.,all contained in polished wood box, asnew, 1716 each.MAINS TRANSFORMERS (New). All2001250 volts input in steps of 10 volts,Outputs 0, 6, 12 and 24 volts at 10112amps., 471- each ; 0, 18, 30, 36 volts at516 amps., 4216 each ; 0, 6, 12 and 24 voltsat 25130 amps., 6816 each ; 0, 6, 12 and24 volts at 516 amps., 351- each.MILLIAMP-METERS CENTRE ZEROMOVING COIL. 1510115 Milliamps21in. scale, 716 each, post 9d. Another 0 to10 Milliamp, 101- each, post 9d. Anotherreading 350101350 Millivolts, 1216 each,post 9d, All new, boxed by well-knownmakers.VOLTAGE CHANGER TRANS-FORMERS (New) 500 watts tapped0, 110, 200, 230 volts can be used eitherway, 651- each, carriage 316.MAINS BOOSTER TRANSFORMERS.1,500 watts tapped 0, 6, 10, 19, 175, 200,225, 240 and 250 volts, good condition,electrically guaranteed, f41151- each.Carriage 51-.DOUBLE WOUND 3,000 -WATTVOLTAGE CHANGER TRANS-FORMERS. 130 to 250 volts or vice versa,weight 1001b., E10 each. Carriage 101 --

MAINS TRANSFORMERS (New). All2001250 volt primaries in steps of 10 volts.Output 350101350 volts, 300 mA, 6.3 v. 8 a.,6.3 v. 8 a., 4 v. 4 a., 5 v. 4 a., 62(6 each ;,500101450 volts 300 mA., 6.3 v. 8 a., 6.3 v. 8 a.,4 v, 4 a., 5 v. 4 a., 6216 each ; 500101500 volts300 mA, 6.3 v. 8 a., 6.3 v. 8 a., 6.3 v. 4 a.,5 v, 4 a., 3 v. 4 a., 6716 each ; 350101350volts, 250 mA, 6,3 v. 8 a., 4 v. 8 a., 4 v. 4 a.,6.3 tapped 2 v. 2 amps. (Electronic), 5716each, Carriage 316.MAINS TRANSFORMERS (New), allwith 2001250 volt primaries in steps of10 volts ; output 350101350 volts, 180 mA,6.3 v. 8 a., 5 v. 3 a., 3716 each ; 35010050volts, 180 mA, 6.3 v. 4 a., 5 v. 3 a., 4 v. 4 a.,3716 each ; 500101500 volts, 150 mA,6.3 v. 5 a., 4 v. 4 a. .5 v. 3 a., 4216 each ;

425101425 volts, 160 mA, 6.3 v. 3 a., 6.3 v,3 a., 5.3 a., 3916 each. Carriage extra 116.METERS EX-W.D. SURPLUS (New),2in. scale, moving coil 0 to 20 volts, 61 -each, post 9d. ; another 0 to 40 volts,717 each, post 9d. ; another 0 to 10 amp.,1216 each post 9d.

284

Centrifugal PumpSuper pumps ready for use in anyliquid pumping need. Outstanding -value ; for all types of intermittentservice in pumping large volumes ofliquid in home, farm and industrialservice. Ideal for home water systemsdraining basements. side protection,etc. ; on the farms for watering stock.draining ponds, sprinkling, etc. ; inshops and factories for all types ofpumping services. When operated at1,750 r.p.m. will pump 42 gallons perminute on a 23 foot head : at 3,000r.p.m. on a 52 foot head will pump(8 gallons per minute. May be runwith electric engine or power take -offon tractor. Pump has cast alumin-ium housing ; accurately machinedbronze impeller vanes. Shaft rotateson sealed ball bearings with grease gunfitting ; has Him intake flange, twolin. inlet for Packard Motor Car Co.for use in Rolls-Royce Merlin aircraftengines. Brand new ; boxed at afraction of their original cost. Canto used with the heavy duty I h.p.motor. Price 47,6 each, carriage paid.

Relays101 'B/520. Siemens' High Speed ;1,700 ohm coil : S.P. changeover.fitted with Vernier armature adjust-ment ; dim. 31n. by liin. by lin.Price 518.110F/715. Packard Bell. 600 ohmcoil ; 2 sets changeover contacts ;miniature relay : dim. llin. by lin.by lin. Price 4/13.A20545. Clare : 45 ohm coil ; 1 setcontacts S.P.S.T. fitted with leadsready for use ; miniature type ;

dim. 111n. by llin. by lin. Price 3/6.1054 ARV. Leach : 180 ohm coil ;3 S.P. contacts, normally open ; 3sets heavy contacts : adjustablearmature ; dim. 3lin. by llin. by11in. Price 56.1029 VA. Leach : 160 ohm coil ;

5 S.P. contacts normally open : 5sets heavy contacts ; adjustablearmature ; dim. 21in. by 211n. byHin. Price EV-.NC4. American : 200 ohm coil,normally open and single -pole action:easily modified to double pole 2sets heavy contacts dim. Bin. by

in. by Gin. Price 4,6.Send S.A.E. for OUT Super Detailed List

WILFLO PRODUCTS216-222, GORBALS STREET

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ENLARGERS up to 21in.EPISCOPESTELESCOPESBINOCULARSRIFLE SIGHTSEPIDIASCOPESFILM STRIP

PROJECTORSPROJECTION LENSCONDENSERS up to 2,1in.MICROSCOPESSTEREOSCOPESMAGIC LANTERNS

If you are interested in makingany of the above then you arebadly in need of our new booklet

" How to use ex -Govt. Lensand Prisms " price 216 each.We hold a large and varied stock '

of ex -Govt. lens and prisms andgeneral optical gear. New andenlarged lists free on receipt ofyour S.A.E.

H. ENGLISHRayleigh Road, Hutton,Brentwood, Essex

'Phone : Brentwood 1685


ENGINEERS

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Technical training is vital to your success.Our Home Study Courses have now beenvery widely extended in range.Write or 'phone for FREE BROCHURESdetailing our courses of TECHNICALTRAINING IN ALL BRANCHES OFENGINEERING covering the syllabuses ofthe various professional examinations,City and Guilds, etc.Moderate terms. Facilities for easypayment.

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Slip a "MASONMASTER " into a wheel -brace and turn. No matterif it is brick, tile, concreteor marble the carbide tippenetrates easily a n dquickly and gives a cleanround hole.Sizes from 5/32in. to ;lin.The " G LAZE M A STE R "bores holes in glass of anythickness without fear ofsplintering or breakage.You just let the drill dothe work. Type B asillustrated for craftsmen.Type A for the handyman.Send for illustrated Book-

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OBTAINABLE FROM ALL GOOD TOOL STOCKISTS

Experimenters ! Build the

MATCHBOX RADIO SETWith the aid of our full instructions you can build a complete

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Tuning arrangements include a medium wave inductor withstation selector switch, and a long -wave coil for the B.B.C.Light Programme on 1,500 metres.

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MAIL ORDER ONLY.

June, 1951

Solorth i Rif/ for you!CRYSTAL SETS. The Festival BoudoirModel, black bakelite case with variabletuning condenser, coil, diode Detectorneeding no adjustment and headphonesspecially suitable for crystal reception301- post free.INDICATOR UNITS TYPE 6, as newand in Transit case with V.C.R. 97 CathodeRay Tube EF50 and 8634 Valves, Hood,Dipole, etc. An interesting parcel ofcomponents for the amateur, 751-, carr. 71-.MICROPHONES. Table type in adjust.able stand with on -off Switch. Sound powertype, need no battery, 716. PostG.P.O. carbon mike in moulded bakelitecase ; hand type, 316 ; transformer, 216,post II-. G.P.O. Mike Button, lin. dia., 316.VIBRATORS. 6 volt 4 -pin non -sync.,as new, 716.RELAYS. G.P.O. bank of 20 relays inmetal case, 100 ohms resistance, 101- each.post 21..TRANSFORMERS. Double wound, new,110 volts input, 230 volts 4.75 KVA output,Eli 10e. B.T.H. 230 volts 50 cy. input,30 volts 6 amps. and 2 volts 20 amps. output,451-. Foster 230 volts input, 50 volts 2 amps.output, 151-, post 21-.CONDENSERS. 4 mfd. 1,50) voltsworking. Also other voltages at specialprices.THERMOSTATS. Small, fit test tube,operate 0 degrees cent. Easily alteredand suitable for Fish Ponds, etc., 616 newand in maker's box.MORSE PRACTICE OUTFIT com-prising precision made A.M. Morse Keywith insulated bar, and knob, twin coilbuzzer with contacts, battery holder onbase with diagram and instructions, 616,post 116.

H OUSE AND OFFICE TELEPH ONES,ex G.P.O. wall type telephone constructors'parts, comprising magneto bell in polishedwood box, 8in. x 6in. x 3in., fitted trans-former, condenser, microphone, connectionstrip, switch -hook and contacts, separatehand magneto generators and G.P.O.single receivers, 351- pair, carr. 51-.Please include postage for moil orders.

ELECTRADIX RADIOS214, Queenstown Road, London, S.W.3

Telephone : MACaulay 2159

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Meters. 10v., 2/in. Rectifier (a.c.), inwooden carrying case, 14/6 15v.. 2/inm/c., 9/6 ; 150v., 2in., m/c.. 10/- ; 3,500v.311n., m/c. 20/- ; 6.000v.. m/c.. 57 615/600v.. double reading, 8,-100 m/a., 21n., m/c.. 7/6 ; 3.5 amp. 21n., T.C.5/. ; 4 amp., 2lin.. T.C., in case with switch7/6. Units containing 2-500 microamp,5/-, post 8d. All meters post extra.Bell Transformers. These guaranteedtransformers work from any A.C. Mains,giving 3, 5 or 8 volts output at 1 amp.,operate bulb, buzzer or bell. Will supplylight in bedroom or larder, etc. PRICE8/-. post 8d. BELLS for use with either theabove or batteries, 6/-. post 6d. BUZZERS3/-, or Heavy Duty 4/6, post 5d.Ex-R.A.F. 2 -valve (2 -volt) MicrophoneAmplifiers as used in 'plane inter-com.,in self-contained metal case ; can be usedto make up a deaf aid outfit, intercom-munication system, or with crystal set,complete with valves, 20f-, post 116. Usefulwooden box with partitions to hold ampli-fier, 2/- extra. Ditto, less valves, 10/-.One valve amplifier, complete with valve.9/6, post 1/-.Hand Microphones, with switch in handle,and lead, 4/-. Similar instrument, movingcoil, 7/6, post 6d.Mike Buttons (carbon), 2/-. Moving Coil,4/6; Transformers, 5/-. All post 4d. each.Sparking Plug Neon Testers. with vest -Pocket clip, 3,3, or with gauge. 3/6, post 3d.S.B.C. Neon Indicator Lamps, for use onmains to show " live " side of switches,i etc.,3/6, post 4d. Soldering Irons. -Our newstreamlined Iron is supplied with twointerchangeable bits, one each straightand curved ; 203250v. 50 watts. 10/-.Standard Iron with adjustable bit,200/250v., 60 watts, 11/-. Heavy Duty Iron,150 watts, 14/6. all post 6d. CrystalSets. Our latest Model is a real radioreceiver, fitted with a permanent crystaldetector. Have a set In your own room.1116. post 6d. De Luxe Receiver in polishedoak cabinet, 18;6, post 1/-. Spare Per-manent Detectors, 25. each. When orderedseparately, 2/6. with clips and screws.2i10, post 3d. Headphones, brand new,S. G. Brown, G.E.C., etc., 15/-. 23/-,and super -sensitive, 30/- a pair, post 8d.New Headphones, 10/- a pair. Balancedarmature type (very sensitive), 12,6 a pair.Both post 8d. New Single Earpieces,3/6. Bal. armature type. 4/6 : ex R.A.F.earpiece, 2/, post 4d. Ileadphones, ingood order, 5/6 (better quality, 7/6), allpost 6d. (All Headphones listed aresuitable for use with our Crystal Sets.)5Ioney refunded if not completely satisfied

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PRISMATIC ELBOW TELESCOPESPower 7 x. Weight 6 lb. Image erect. Definition is crispand free from distortion. Post free ... 27 6

HAND SIGNALLING LAMPSDiameter of reflector 5in. Bulb pre -focus 12 volt, 36watt. This lamp gives a brilliant beam and is suitablefor use as spotlight, inspection lamp, etc. Cover glassavailable in green, amber or clear. Post 11- extra ... IS 0

116th H.P. ELECTRIC MOTORSHoover repulsionlinduction with automatic overload cut-out. 240 v.-250 v., 1,425 r.p.m. Single-phase A.C.Mounted on rubber cushion, sprung cradle ensuringsilent running. New and unused, although outer cas-ing is slightly soiled. Inc. carriage ... 4 9 6

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WILCO ELECTRONICS204, Lower Addiscombe ltd., CroydonAIRCRAFT CLOCKS with splendid 8 -dayjewelled movement, flange type, made tostringent Govt. specification. Brand new.guaranteed. Ideal for car, study, bedroom.etc., will withstand vibration and shocks.Special offer, 65:- each, post free.BATTERY CHARGER, Input, 230 voltsA.C. ; Output, 4 amp. 6 or 12 volts, in neatcase with meter fuses, control switch.£6:8.0. Pkg. & carr., 4/-.BATTERY CHARGERS `IVESTALITE."Input 100,250 v. A.C. Output 12 v. 16 amps.,variable metered output, fused, worth £34.Our price while they last, £15. Carr. & Pkg.,

POWER UNITS. Comprising standardmains transformer, 350-0-350 volts 80 M/a..6.3 volt 1 a., 6.3 volt .5 a., 5 volt 2 a., L.F.choke, 8+8 Mfd. condensers, 5Z4G valve,etc., contained in steel case Sin. x 811n. xSin. Sufficient room to build in smallamplifier. Brand new 82:10/0, carr. and pkg.,2/6.SHOWCASES. -Hardwood with plate glassopening' front; 3ft. 31h. x 2ft. 3in. xIdeal for shops, factories, etc., 451-, carriage

" ELF " CIRCUIT BREAKER. 220 volts1-2 amps. size 3 inches round, 10,6. Postage1/-.KLAXON GEARED MOTORS No.IK5S133-W7. Torque lbs. ins. 15. R.p.m.175. Motor r.p.m. 1,900 at 230 v. A.C. Splitphase induction type, £10 each.KLAXON CAPACITOR INDUCTIONMOTORS with lin. fan, 1,40 h.p. 220/240 v.A.C.. 2,700 r.p.m. No. EM5CB2 with con-denser, 55; -.each.24 VOLT D.C. MOTORS with double endedshaft 2in. x 3in., 10/6, postageTHERMOSTAT SWITCH. -Bimetal typein sealed glass tube, 211n. x lin. 30 deg.Cent. Ideal for Aquariums, Wax and OilBaths. Gluepots. etc. Will control 1 amp.at 240 v. 5/- each.VOLTMETERS. -0-300 A.C. Moving Iron211n. Flush, 17,6 ; 31in. Flush or Surface,22,'6.MASTS, TELESCOPIC, extending to lMt.in 7 sections, 151$, Post 1/-.THERMOSTAT. Satchwell 121n. stem0,250 volts A.C. D.C., 10 to 90 deg. Cent., 35:-.SPEAKERS. -P.M. Bin. Goodman, in wallcase, with transformer, 21/ -.Post & pkg. 2/6.

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Hand -Driven GeneratorH. 409. Hand -driven Generator 10K/13043 comprising of a 40 I gearing unit driving agenerator producing 6.3 v..5 a. and 300 v. SO ma complete with ratchet handle. Diam.7in. long. Used, but in good condition.

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DUKE & CO.50 YARD SPOOLS OF NI -CHROME.014 wire for only 2'-, and 25 yards.032, same price. These bargains are afraction of to -day's price. (If you canbuy it.) Postage extra.TYPE 22/49 TR ANSNII1TER. 2 6.Mostly new. Relays. crystals, and coilwire removed. Otherwise perfect. Setincludes : 11 res. : 11 coeds.: Jonessocket. International Wholders. tagpanels, press button switch, panel ofsockets for crystals, stwave choke, 3bank Yaxley switch. slow motion drives.valve caps, metal chassis and cover. Novalves. Ideal for amplifier. Contentsnot guaranteed. Post 1/6.GERMAN INVASION BOATS. 50!-.20 to 30ft. x 6 to 8ft. wide. Tough. vul-canised rubber. Inflatable. Roomurgently required. Plus carriage.EX :MILITARY BOAT. 13ft. NEW.In two packing cases, including allaccessories. Bargain, 6 alas. Inflatable.PANNIER BAGS, 716. Limited quan-tities. made of tough. vulcanised.rubberised' canvas. 14 x 101 x 5Uns. ;

lined with /in. sponge rubber. Requireonly fixing clips. Strong webbingstraps. Water and dust proof. Nothingelse as good at the price. No. P. Tax.Post re.HEAD LAMPS. Ex-L.P.T.B. Standardsingle bolt fitting, '7/6 ; plus 1/8 post.TV LENSES. NEW. 12in. 75'-, othersize.. 8. 9 or 65/... Post 113.PHILCO CABINETS. (Table) Plasticwalnut, approx. 18 x 161 x IBMs., a fewonly, 15!-, plus 3 - carr. (C/Patersondistricts only).CHOKES. MIDGET. 4 for 5/-. 10henry, 50 mill., 300 ohms. Post andpacking, 1/-.BEDSIDE RADIO KIT. In bakelitecabinet, 4 valve T.R.F. Universal orA.C. for only 24.15.6. or in Ivory. 6, -extra, assembled 30)- extra. New andimproved circuits.An amateur can buildthis set, with practically no knowledge.The ONLY set now available at thisprice. 'Post and packing. 2/6.SPEAKERS. 2'ins., complete withtrans., 1616. Also new but slightlydamaged, 12/6. Same speaker, lesstrans., 13/6 post 1'-.H.T. BATTERIES:90 volts guaranteedand 3 volts L.T. This is of the smallPortable 'type, with standard British,all -dry connections, 5/8. post 1/6.CRYSTAL SETS. Complete, receptionguaranteed, 8'6, plus 11- post.

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THE "FLUXITE QUINS"AT WORK

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f

June, 1951

VOL. XIX

Editor : F. J. CAMMJUNE, 1951

THE CYCLIST

No. 349

57

All letters should be addressed tothe Editor, "THE CYCLIST,"George Newnes, Ltd., Tower House,Southampton Street,Strand, London,

W.C.2.Phone : Temple Bar 4363

Telegrams : Newnes, Rand, London

Comments of the MonthAWRITER in a contemporary under the

heading - No Quarter or Compromise "deals with the " Heal the Split " moves

being made to make peace between the variouscycling bodies and to find a formula whichwill accommodate the various points at issue.

His comments are unlikely to do anythingto cause the split to be healed. As we havebefore remarked, the split should be hailed,not healed. The contemporary in which thewriter expresses his point of view is onewhich has been severely critical not only ofthe B.L.R.C. but also of the N.C.U., andthey are the main antagonists. This contri-butor says " the only people who can healthe split are those who caused it." This isa nice trite phrase, but it is thoroughlyillogical. It is well to suggest that a, manwho has cut his throat is the best person toheal it.

I agree with this critic when he says thatmassed -start racing in its latest form hascaused much disquiet among the moreresponsible sport -promoting clubs. But thereason for this disquiet is not what the criticthinks it is. Sports promoters are naturallyjealous of the publicity which massed -startracing attracts, to the detriment possibly oftheir own events. Instead of promotingevents having greater attraction and compet-ing by fair means they are adopting theusual underground, hole-and-corner un-sportsmanlike methods which in certaindirections has been undermining the sport formany years.

The R.R.A. was formed as the result ofa breakaway movement, and so was theR.T.T.C. It would be equally true to saythat they were dissident bodies. It is per-fectly proper if a large body of cyclists wantto indulge in a particular form of cycleracing to break away from a body which isopposed to it. On the question of the so-called danger of massed -start racing, whereis the evidence of it ? The critics in theearly days of massed start (not -in -line if youplease!) stated that there would be manyaccidents, that such form of racing wouldbe dangerous to other road users when motorcars came back on the roads in sufficientnumbers.

The critics, after ten years, have beenproved wrong. Every possible move hasbeen made behind the scenes to get massed -start racing banned, and the underhandmethods adopted to this end have merelyforced hundreds into the ranks of the massedstarters. Naturally this is aggravating to theproprietors of cycling sport, and most of allto that obsolescent body the N.C.U. whichwhich has long ceased to reflect cyclingopinion or to exercise control.

We agree that there is no half -way houseat which the differences between the, twoschools can be composed. Each wishes tosubmerge the identity of the other, that isone reason why the oft -suggested con-dominium between the N.C.U. and theC.T.C. has failed. There really is no needfor the two bodies. We therefore arrive atthe point where massed -start racing must berecognised as a new form of cycle sport

Healing the SplitBy F. J. C.

which is here to stay. It may be scornedon by the elder brethren, but then so wasthe pneumatic tyre. We do not think thatany Government in view of its record willban massed -start racing.

Festival of CyclingTHERE can be no doubt that the Festival

of Cycling will be one of the greatestcycling week -ends. Visitors to the DunlopSports Field where the Festival will be heldon June 23rd -24th will not only see a sortof cavalcade of cycling, past and present, butexhibitions of riding skill, a grand fireworkdisplay finale, demonstrations of folk danc-ing, and be able to listen to famous bands,and one of the best displays of old cyclesyet seen in this country.

Sunday's events will include an open-airChurch Service conducted by the Arch-deacon of Birmingham, accompanied by theFestival Singers, a combined choir drawnfrom famous cycle factories ; a competitionbetween bicycle polo teams, a demonstrationof cycle roadmanship by 200 young Birming-ham riders.

Midnight matinees have been arranged byGaumont-Odeon Theatres, the sponsors ofthe Festival, at their cinemas in New Streetand Steelhouse Lane, Birmingham. At thosetwo theatres nearly 5,000 cyclists have beeninvited as guests.

A special Scots feature in Saturday's pro-gramme will be the ceremonial welcome ofthe party of riders from the Cumnock Rally,which is being held during the same week-end. There will be demonstrations by theWomen's League of Health and Beauty, tra-ditional country dancing by the MidlandGroup of the English Folk Dance and SongsSociety.

Britain's ancient crafts to be demonstratedwill include a Warwickshire woodturnermaking bowls, egg -cups and plates; a demon-stration of pottery painting by two Staf-fordshire pottery artists, and an exhibition ofrepousse work, roller racing, etc., etc.

The admission fee to the Festival groundwill be is. 6d. inclusive, and this fee includesa copy of the Festival Programme, entry intocompetitors events, cinema shows, and theuse of ground facilities, such as exhibitions.

Clubs and sections of clubs are invited totake part in the Parade of Clubs immediatelyafter the Festival opening-the first event toemphasise the popularity of club cycling.Four riders from each club or section of theclub will Lake part. Each rider will carry acane or light pole surmounted by a triangularflag with black background and yellow letter-ing stating the name of the club.

Seven Members of Parliament will attendthe opening-Mr. J. Silverman, Mr. F. L.Shurner, Mr. Martin Lindsay, D.S.O., Mr.F. Longden, Mr. V. F. Yates, Mr. C. C.Poole, and Mr. H. C. Usborne. Mr, A. E.Scott -Piggott, head of the Festival of BritainLiaison Branch will open the Festival. The

411111WIMMINNIMIIIIIIN

Lord Mayor of Birmingham and the Mayorof Lymington will be present.

Reg Harris is to appear with four otherinternational stars on the quintuplet which54 years ago helped by J. W. Stocks to setup the record still standing for the longestdistance ridden in one hour on an outdoortrack with human pacing -32 miles, 186yards. Stocks used this " quint " for theloo kilometres World Championship atGlasgow in the same year, and it is still infirst-class running order although it hasnever had such distinguished riders .on itssaddles at one time.

Comments on RoadsTHE British Road Federation has recently

compiled a series of comments byCounty Surveyors and others on our roads.Here are some of the comments.

" The roads are getting into the state whenvery shortly they will become completelyimpassable." (Lord MacDonald, chairmanof the Roads Committee of Inverness CountyCouncil.)

" Some (West Riding) roads must be seento be believed. Many are in danger ofcollapse because they were not made to carrythe present volume of traffic, and deteriora-tion continues through lack of funds. . . .

An even more vital consideration is that inthe event of national emergency, the adventof heavy Service traffic on some of the roadsin the Riding would result in their completecollapse within a matter of a few months."(Mr. S. M. Lovell, county surveyor, WestRiding.)

" I know from long experience of motoringon the roads of this country and from com-mercial experience outside my Parliamentarylife that for various reasons our roads seemto be hopelessly behind current needs." (Mr.Alfred Barnes, Minister of Transport.)

" One day in the coming summer, a roadaccident will occur which will involve themillionth person to be killed or injured onthe roads of Great Britain since the end ofhostilities in 1945. And the rate is stillrising. (Mr. James Drake, county surveyor,Lancashire.)

" We all know that increases in the num-bers, variety and speed of vehicles on theroads have made our present road systemseriously obsolete." (Mr. Herbert Morrison,M.P., Lord President of the Council.)

ExportsMORE than £6,375,069 worth of bicycles

and motor -cycles were sold by GreatBrtiain overseas during the first quarter ofth3 year, £827,551 up on 195o. Bicyclesshowed the biggest increase, £771,928 ;motor -cycles £55,623. Most of the latter(5,436) went to Australia ; followed byU.S.A. (1,925), Canada (1,215), NewZealand (1,174) and Switzerland (984).

Malaya was Britain's best customer forbicycles (£639,789 worth), followed byBrazil (£404,237), India (£33o,004), BritishWest Africa (£326,414), Pakistan (£277,69o),U.S.A. (£227,605) and British EastAfrica (E212,986).

58

,,111111111111111!III11111111111,

When repainting or re -enamelling the framesuspend it from the roof of the shed so that all

parts of it can be seen.

AT this time of the year one instantlyconjures up thoughts of the delightfulweek -ends to be spent with a cycle

during the ensuing months and holidays.Before we begin to make our plans, how-ever, we must first turn our attention to themachine that is to convey us on thoseprospective tours. Perhaps it will require afresh coat of enamel, new mudguards,brakes ; in fact, there may be many thingsthat will need adjustment.

Enamelling the BicycleThere are many first-class enamels on the

market which have been advertised in thisjournal from time to time. Best results areobtained by stripping the machine, as thisenables the frame to be hung up whilstenamelling and also provides for easier work-ing. Small unenamelled parts prepare theway for flaking and chipping at a later date,so that it is essential that no small cornersare overlooked.

A passable finish may be obtained byenamelling over the old surface, first smooth-ing it with pumice stone and emery cloth.The real stoved-on finish, however, can onlybe imitated by first removing the old enameland applying fresh coats of paint to the baresteel. The old enamel can be removed byone of the popular removers or by dissolvinga pennyworth of potash in a cupful of waterand then rubbing the resulting liquid overthe frame, so that the old coats will be suffi-ciently softened for them to be scraped offwith a knife.

Turpentine should be used to clean thebare steel, which is then well wiped andsmoothed with emery cloth.

The tendency to -day is to use brightenamels and thus enhance the appearance ofthe mount. Enamelling should be done witha soft brush, as a stiff -haired one will givea " brush -marked" finish. After the firstcoat has been applied it should be allowed

BottomBracket

Cut) Unscrewed

7 Ar# AMR,4 IIIIIIIIIIIIIIIIIIIIIIIIIIItllllllllll,l1111,,

0,141

11111111111111111111111111111111111111114011

j<jt4.11111114111;1:,1ii,N,§sripysto ri. A4

MachineUpside Down

111111111111111111

Balls Fallinto FrameTube as Cupis Unscrewed

to harden (twenty-four hours is usuallynecessary), and the second application of theenamel should be preceded by a rubbing-dOwn with a very fine emery paper. Relin-ing the frame with transfers will add to itsappearance. A paint spray gives the bestfinish.

Care of the MudguardsThe mudguards should next receive atten-

tion. These may either be of steel 'or cellu-loid. Dents in steel guards may be removedby placing a sandbag under the guard andhammering with a padded hammer. Theycan then be given a fresh coat of enamel or,if they are badly dented, new ones shouldbe fitted.

Celluloid mudguards have a tendency tocrack if they neglected or dented, and

Steering Head RaceOut of Alignment

Showing cause of shake in the steering head.

Offside Crank ReplacedSpindle Falling Out.

to Prevent

Above : The bracket is inverted when replacingthe nearside adjustable cup, the spindle beingheld in position by temporarily replacing the

chain wheel and crank.Left : A machine should not be inverted whendismantling the bottom bracket bearing for thereason shown here. As the cup is unscrewedthere is a risk of the balls falling into the frame

Tubes andbeing lost.Right : The procedure in reassembling thebottom bracket bearing. Lower the spindle intothe bracket after previously screwing in theoffside cup from underneath, with the balls held

in greas:.

THE CYCLIST June, 1951

Overhaulin theTo Ensure Maximum Efficiency of Your Cycle it Should be

Preparation for the Touring

an efficient repair can be carried out bycleaning the cracked edges and uniting themtoisther ,with a little celluloid (or " pear-drelp ") cement. A patch of celluloid may

The balls may be picked up by means of ascrewdriver having some .Vaseline on the end.They should be laid on a piece of cloth andwiped clean so that they may be inspected for

rust or pitting.

be inserted and cemented into position bymoms of the same adhesive if the crackedarea of the mudguard is extensive.

White " safety " rear -flaps can also be re-paired in the same way, and usually becometemporarily plastic under the influence ofmoderate heat. Masses of dried dirt, whichgenerally accumulate on the underside of themudguard, should be removed, using a long,flexible brush for the purpose. This willminimise rusting of the underside of steelmudguards and their life will be greatly pro-longed in consequence.

The BrakesBrakes are a most important item and

should receive a very thorough overhaul.When refitting any type of rim brake itis very important to see that the shoes arefitted the right way. The holders will befound either to taper or to have flanges at-one end, and this end must be the lower oneif the blocks are fitted vertically, or the frontend if they are horizontal, otherwise the rotat-

June, 1951

BicycleOverhauled and Adjusted in

Season

ing of the wheel will tend to force the blocksfrom the holders when the brake is applied.

With a cable brake it is essential to attendto the cable itself before refitting. Greaseshould be forced liberally between the wireand the covering, to prevent breakages andto make the brake easier to apply. Thestranded cable of Bowden -operated brakes

Reassembling a pedal after it has been takenapart. The steel balls in the inner cup areplaced in position with grease and the spindle

is lowered into position.

should be well protected when it leaves theouter casing at the brake end and at the hand -lever end.

Rust generally attacks these two points,and eventually leads to the strands cartingand the cable breaking. Do not let aBowden cable leave a brake at an angle, asit will prove extremely troublesome. Itshould lead out straight from the abutmentadjustment. If, when the brake lever isoperated, it catches the edge of the hole, itwill wear, thus causing a strand to break.

Hub Reversed

Sp;ndle Restingon Bench. N

Here the wheel is reversed in order to replacethe other set of balls. With the balls in placethe adjustable cone is screwed down as shown.

THE CYCLIST

LubricationWhen oiling the hubs, a good quality oil

of medium body is recommended. The cycleshould be leaned over to one side when inject-ing the lubricant, as the feed cap is usuallysituated in the centre of the barrel. Whenthe oil appears on the spindle -cones, spin

CardboardSleeve

A cardboard sleeve fitted as shown will preventthe balls from falling between the cup and thespindle. The cardboard can be retnoved after

the balls are in place.

the wheel to assist the lubricant to workthoroughly into the bearings.

Oil hub -brake bearings sparingly, andmake sure that the lubricant does not flow on

Fork Blade

Cone Hub Shell

------------,,,,41 ,

III Innown!!!!!!

FlangedTin Lid

Felt Washer

Hole Cut to F,tCone Flange

Tin Lid

1111

Spindle

FeltWasher

Section of hub assembly showing felt oil -retain-ing washers, which also exclude moisture and grit.

11,Lower Spindle into11e

mpHub Shell ..0.

Balls Heldin Grease

Reassembling wheel bearings. The fixed coneis screwed on to the spindle, which is being

lowered into the hub.

59

Method of removing the balls from the outerbearing of a pedal.

to the brake linings. A time -worn tip, butnevertheless worth mentioning, is to see thatthe oil does not run down the spokes, as itwill enter through the nipple holes in therim, with disastrous results to the inner tube.

The machine should again be laid on itsside during the process of oiling the free-wheel. Thin oil should be used for this.It is as well, before starting on the free-wheel, to squirt a little paraffin through theoil -cap to wash out the dirty oil, which mayotherwise cause the pawls to clog. Thepedals should be oiled next, and shouldreceive special attention, as they are subjectedto more exposure from mud and rain thanother parts.

The steering head bearings are neglectedmore than any others. It is a simple matterto stand the machine upright and drop a littleoil into each bearing.

The ChainLastly, we come to the chain. This should

be removed and washed thoroughly in a bath

Chain Flat on Bench

Check ForSide Playin Rollers

Testing chains for stretch, rivet and roller wear.

of paraffin to remove dirt and grit. Gritwill cause chain wear, as it will slowly grindthe metal away, and a chain roller can easilybe stopped from turning by a particle of grit.After the chain has been thoroughly washedin the paraffin, allow it to dry. It shouldthen be placed in a shallow tin filled withfairly thick oil, which should be warmedslightly to allow it to penetrate with morefreedom into the required places.

Allow the chain to cool before hanging itup to dry, and wipe away all surplus oilfrom the outside. To ensure that the oilingprocess is carried out efficiently, somemachines are equipped for the use of an oilgun. By this method of lubrication, oilpenetrates right into the bearings, at the sametime pushing out the " dirty " oil.

t -S

- 60 THE CYCLIST June, 1951

Around the Wheelworld

Cycles at the FestivalTHE opening day of the Festival of Britain

did not disclose very much to suggestthat the British cycle industry had stagedanything worthy of its magnitude. I wastold by the Industries Press Officer that acomprehensive selection of bicycles andmotor -cycles had been made for the Festivalby the Council of Industrial Design at SouthBank. I was informed there would be 8motor -cycles, 20 bicycles, and 4 children'stricycles in the Power and ProductionPavilion, the Transport and CommunicationsPavilion, the Camping Display and else-where. Why did not someone suggest acomplete exhibit truly representative of thesport and pastime, and not merely repre-sentative of a few firms' wares ?

And what has the Imperial ScienceMuseum at Kensington done ? On the open-ing day I rang the Museum to know whathad happened to the replica of MacMillan'sfirst rear -driven bicycle, only to be told, asI was on March 6th, 1948, that it still wasnot at the Museum from which it wasremoved to the fastnesses of Wales forsafety during the war. In 1948 I was toldthat it was due to transport difficulties thatthe machine and other historic bicycles hadnot been returned. I have 'phoned theexhibition regularly ever since, and havebeen fobbed off with footling excuses.

The Imperial Science Museum shouldrealise that it is a state-owned institution,that the exhibits belong to the British public,to whom it owes the duty of seeing that theexhibits are available. Someone there hasforgotten the Festival!

Why in any case should the exhibits atthe Festival be split up ? Anyone interestedin cycling is hardly likely to traipse roundseveral sideshows to see the various exhibits,paying an entrance fee every time. It is apiece of absurdity, for example, to exhibit atandem cycle in the Gallery of Metals.

R.R.A. Triennial DinnerTHE Triennial Dinner of the Road

Records Association which was held atthe Connaught Rooms on April 13th wasa nostalgic affair for the numerous recordbreakers of the past who forgathered underthe chairmanship of the president.

The room was not altogether ideal in thatnumerous pillars prevented those seated atthe sprig tables from observing those atthe top table. The acoustics were also verypoor, but otherwise this once -every -three-yearevent was well organised.

The toast of the association was proposedby H. Green with a .response by W. H.Townsend, the secretary. The importanttoast of the evening, Record Breakers Pastand Present, was proposed by H. H.England in anecdotal style with responses byE. V. Brown and A. R. J. Hill, whilstCycling, the Sport and Pastime, was dealtwith, if somewhat sketchily, by S. R. Baronwith responses by S. T. Capener and W.Oakley.

It is my view that three years is too longa gap and these reunions should be held atleast once every two years.

Old-world Charm of English RoadsOFFICIAL publications concerning the

Festival of Britain which are circulat-ing in the U.S.A. with the object of attract-ing visitors to the Festival contain thefollowing rhapsodic encomium:

" Those who are accustomed only to thestark efficiency of Continental highways,

By ICARUS

which bore their tree -lined way through thecountryside, intent merely on tracing themost direct route between two given points,will be agreeably surprised by the charm ofBritish roads. In England roads havecharacter. They think nothing of making adetour in order to spare a tree, or to avoidcutting off the end of a cottage garden. . . .

" . . . The excellent condition of the roadswhich serve even the most remote towns andvillages in Britain is often a source of genuinesurprise to the visitor. Their smooth, dust-less surfaces and well -maintained edges, theirreliable signposting and the care with whichdanger points have, as far as possible, beeneliminated, all excite admiration. Here is_evidence indeed of the skill and conscientious-ness of the highway authorities of Britain."

The most commendable sentiment con-tained in this lyrical description appears inthe last sentence. Were it not for the " skilland conscientiousness of the highway authori-ties " many of our principal highways wouldhave collapsed long ago owing to Govern-ment diversion of the funds intended forroadwork.

The Late Harry ParsonsHARRY PARSONS was the first man to

cover 22 miles in 'the hour on abicycle. He died in February, aged 79, buthis real interest was motor -bicycles. Hefounded the Parsons Engineering Co., Ltd.,Southampton, and was formerly chief designerto the Rudge Whitworth Company. In the'nineties he built a Quad and claimed to havedesigned the sociable or side -by -side machine.He evidently found the cycling and motor-cycle industry prosperous, for he died worth£165,437.

The London -HolyheadTHE above race which takes place on

Saturday, June 9th, bids fair to eclipseany similar road event. The course has nowbeen measured and the total distance, includ-ing a detour at Weedon, where there is adiversion owing to bridge construction work,is 267 miles. The race will be started at5 a.m. and a huge reception is to greet theriders at the finish on the promenade, Holy-head, where the leaders are expected to appearat approximately 6 p.m.

1

wzaw, semi° I syctist.

The National Railways Beauty Queen willpresent the awards at an official functionafter the event. The prizes are extensive,and are of especial interest to independentsand professionals, the two classes eligible tocompete. The total value of the prizes isover £15o. Current star of those certainto ride is Dave Bedwell, stocky five -feetRomford man, who has won all three eventsin which he has ridden' this season. Bedwellwill be well supported by clubmates LenWest, current B.L.R.C. road champion, andcaptain of the team, Les Scales, former 5 -mileN.C.U. grass track champion, Les Wade, who" makes " team wins rather than winningraces individually, and Clive Parker, whoseability is only overshadowed by Bedwell.

Cycle Stands StandardisedTHE British Standards Institution has just

issued a British Standard for CycleStands (B.S.1716:195t).

In view of the variety of parking equip-ment for cycles at present in use the prepara-tion of this British Standard was undertakenin order to standardise the most convenienttypes suitable for any particular purpose, andin order to provide guidance to purchasers,architects and others in their selection. TheStandard refers only to stands constructed ofsteel or of concrete, but it is not intended topreclude the use of other materials anddesigns, some of which are the subjectof patents or registration.

Performance requirements are given bothfor steel stands and those constructed fromconcrete, and appendices are included con-taining recommendations on the selection,spacing and maintenance of the stands.

Copies of this Standard may be obtainedfrom the British Standards Institution, SalesDepartment, 24, Victoria Street, London,S.W.t, price as. 6d. post free.

Is Man Carnivorous ?

-I-

HAVE received the following letter fromthe secretary of the Vegetarian Society

(National) of Manchester. I publish it with-out comment.

" May I comment on two statements whichappeared in your May issue ?

" The first is the incorrect assumption thatman is a carnivorous animal. No physio-logist would dare to make such a statementbecause the whole of, man's digestive appar-atus proves the contrary. The late Sir PeterChalmers Mitchell (then secretary of theZoological Society of London) said ' Apesand men were fundamentally vegetarian, justas otters and ferrets were fundamentallyflesh -eaters, notwithstanding their readinessto eat carrots or fruit.'

" The other statement was to the effectthat no vegetarian has ever achieved anythingwhich has not been equalled at least by car-nivores. To take one instance only-in theworld of sport a vegetarian holds the twolongest cycling records on the books of theRoad Records Association-the Land's Endto John o' Groats and the r,000 miles (S. H.Ferris), and the Land's End to John o' Groatswalking record is still held (since 1908) bya vegetarian (George Allen).

" The point which vegetarians wish toemphasise is that a suitable vegetarian diet iscapable of supplying all the needs of man.Bad diets are chosen by both vegetarians andflesh -eaters. On the other hand, is all thesickness among flesh -eaters any credit to theirdiet ? Our hospitals are not, by any means,full of vegetarians, but meat -eaters!

June, 1951

FIRM

CONTROL

THE CYCLIST

even when wetFerodo All Weather Brake Blocks are made of specialfriction material that is practically unaffected by weatherand can be relied on to give you safe. positive controlfor long hills or emergency stops.

For use with alloy rims, ask for the special softquality blocks, now available, which do not score thelight metal.

The price of standard sizes,both normal and soft quality, is

A PAIR

HUB BRAKES. Ferodo Linings are supplied inboxed sets, complete with rivets, for all makes of hubbrake. The size is exact, and the friction characteristicscorrect, for each type. Also available in roll form.

FERODOALL WEATHER BRAKE BLOCKSAND LININGS FOR HUB BRAKES

FERODO LIMITED, CHAPEL -EN -LE -FRITHA Member of the Turner R Newal! Organization

REG'D TRADE MARK

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61

iteepyour eye

ox

allords. . . and be sure of the finestselection of spares, accessoriesand equipment, includinga full range of " Halford "" Raleigh " and " RobinHood " Cycles-there's aHalford's branch in everylarge town.

THE HALF,ORDCYCLE COMPANY LIMITED

HEAD OFFICE

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222 BRANCHES IN ENGLAND, SCOTLAND AND WALES

62 THE CYCLIST

- -/"/V4 '/ "/1, /' /

fifers you a range

CYCLE new

June, 195

50H/348

4

FRONT SEAT for the Festival;

THE FESTIVAL OF BRITAIN IS not Con-fined to London. Cities, towns andvillages everywhere are organising ex-hibitions and displays. See them fromthe saddle of a B.S.A., the Bicyclewhich will make you independent ofexpensive and inconvenient publictransport for years to come.

Lj.

This 13.S.A. LightTourist wills Reynolds531 frame, DunlopSprite Tyres and calliperbrakes will exactly tillyour bill. Price ,93.2.6-b 0.1.3 Tax, °r oil EasyTerms. See you; B.S.A.Dealer.

Send coupon for cora-logue of full range ofB.S.A. Bicycles.

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Its three - To B.S.A. Cycles Ltd., 12. Armoury Road,Birmingham, II.

you had a Please send Catalogue

NAME

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IMPORTANT NOTICE toOwners of MOTORISED BICYCLES

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of

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CANTILEVERS have been given special tests on bicycles fitted with many of thleading Motor Units, and as a result they are being strongly recommended fotheir complete EFFICIENCY and RELIABILITY. Your life depends upon youbrakes, and the addition of a motor unit to your bicycle makes it vital that yoare equipped with the best brakes obtainable. CANTILEVERS will give yocomplete CONFIDENCE in ANY EMERGENCY. Fixed rigidly on the forks ostays, they are always positive in action, smooth and powerful, grip well in thwet, and give long service. Special models available for use on Westwood rim:Fitted with our Locking Lever, they make the ideal SAFEGUARD against pettthieving. Twelve month guarantee with all new brakes.

SAFETY FIRST ! Second Thoughts are Too LateTHE RESILION CO. LTD. 200, LIVERPOOL ROAD, LONDON, N.I

June, 1951 THE CYCLIST 63

Wayside ThoughtsBy F. J. URRY

Hope, South Devon.-The picturesque little fishing village *with its charmingthatched and whitewashed cottages.

Thi s WeatherA COLD sticky morning wrapped up in

fog, and everyone I meet swearing atthe conditions, the power cuts and the dis-comfort. I agree a bit of a fire is very cheer-ful after a seven miles ride slowly and withcircumspection, for it warms my feet andmakes me realise there is still a sting ofwinter left in this weather. But have youconsidered how very fortunate we Britishersare in the matter of the elements, duemainly to our watery friend the Gulf Streamabout which we were informed in our schooldays. It is, of course, part of the Britishtemperament to swear at the weather whenit rains or snows. I came to the conclusionlong ago that it is the best weather in theworld because it is no nicely assorted. Re-cently I was out in a chill temperature beauti-fully tempered by sunshine, the kind of daywhen you loole for the snowdrops in thecottage gardens and think sublimely of themonths to come. And to -day the dirty foghas rimmed my collar and made my eyessmart, and to-morrow-who knows?-the sunwill probably be shining, and we shall haveforgotten yesterday. Such variety goes onall through the year, generally without ex-tremes to bring fear into the hearts of anyof us. From month to month we seldom getlong spells of any single type of weather,never long enough to weary of the sunshine,or bad enough to keep us inactive because ofrain. It is a benison we too seldom appre-cipte, especially we cyclists, and it is justas well to think of our fortune in this respect.Added to our roads, our scenery and ourhistory, there is no land in the world soperfectly equipped for the cyclist. I expectI am as ungrateful as most other people incussing the weather just because it doesn'ta0 as I desire, but the overall picture isindeed a very delightful one.

Home Is Very GoodAS I grow older I sometimes wonder why

the younger folk are so keen onforeign touring. Is it a sort of kindlyostentation, this gentle brag of foreign

travel, or is it, as so many of them tell us,the desire to sample other lands while theirresponsibilities are light, and the necessarymoney is not an undue handicap ? I aminclined to think it is the latter, and it isdiffiCult to criticise such decisions. When Iwas young, foreign travel was much more ofa wheeling adventure than it is to -day, wheneverything is made easy for the Continentalwanderers; and I must confess that when inmiddle life I crossed the Channel I foundnothing in the matter of scenery to give anygreater joy than the vistas of my own land.Perhaps that was because snow-so firmlyallied to Switzerland-never had any appealto me, for I always looked upon it, as MarkTwain said, as " merely adding another pangto winter." It was pleasant to meet otherpeople speaking other tongues, to sample an-other way of life ; but from the scenic angleI got no greater thrill than I can 'find inYorkshire, Wales, and The Lakes, or Scot-land. Many foreign -travelled cyclists seemto know much more of other lands than ofBritain, and when I speak to them on thissubject the reply is that they intend to " do "'the home lands after they have settled down.I wonder ? Many of the younger generationI know who have settled down after theirforeign scampers, have, alas, given up cycling,and will never now see this best of all coun-tries through the eyes of the cyclist. MaybeI am parochial, and love the quiet charm ofmy land with a native intensity unshaken,yet I often deplore the fact that so many folkI talk to know so very little about it, andgive the guerdon to foreign touring withoutthe knowledge of comparisons.

Why Cavil ?CLUB subscriptions are rising, and some

of my young friends are inclined tobe critical of the fact. Why ? Is thereanything we need with which to carry onlife that has not risen ? If so I don't knowof it. Do you think the expense in con-nection with club organisation should be theexception ? As a matter of fact it is theexception because it is one of those services

which seeks not a profit, but the performanceof a sound job which is considered satisfactoryif it makes ends meet. I mention this matterbecause it is important. A man or girl whoundertakes honorary work for the benefit offriends ought not to be subjected to financialworries as, I'm afraid, many club officialsare at the present moment. Let us facethe facts and be honest with ourselves. Mostpeople at work are earning double the wagesthan was the case fifteen years ago, and theyounger element nearer three times thisamount, and yet some of them seem to thinkclubs can be successfully run on the old sub-scription.- We cheerfully pay more for ourtyres, our repairs, our bicycles, our fads. andour touring, while our equipment in thematter of bags and mackintoshes is far morethan double. But we buy them, and it is onlywhen club subscriptions are discussed thatwe begin to plead poverty. It is unfair, andit seems to me a little unsporting to expectan honorary service to be the cheapest thingin the cost of living ; indeed, it is a certainmethod to disgust that ever valuable in-dividual, the honorary worker. I agree thatmany clubs are subsidised by their rich sup-porters, and I am glad of it ; but they cannotexpect such generosity without the membersthemselves showing their willingness to maketheir reasonable contributions. It seems tome this paragraph is needed to implement theappeals to reason, and the loyalty to club life.

Festival RallyFOR the first time in the history of -cycling

-as far as I remember-the trade, thesport and the pastime are at one in runninga Festival of Britain Rally for the propaga-tion of cycling. This is a fine gesture to afine game, and I am glad in feeling thisgigantic show piece is bound to be a success.The dates are Friday evening, June 22nd,Saturday the 23rd, and Sunday the 24th, andthe venue, the Dunlop Sports Ground at FortDunlop, could not, in my opinion, bebettered, for there is space and accommoda-tion second to none. And the spot is par-ticularly appropriate, for without Dunlopcycling could not have spread in such aspate of travel, for to my knowledge the oldsolid tyre would have shaken my bones toopainfully to remain a cyclist at three scoreand ten. That; however, is by the way ; thegreat thing is that cycling is going to get itsbiggest boost of the century, for the folkconcerned with the enormous work oforganisation mean to make this Festival Rallythe occasion for putting over the story, notonly on the spot selected, but through someboo cinemas in picture form throughout thecountry. The aim, I understand, is to makethe Rally a colourful display, attractive andvariegated wiTli items of interest for every-one, from the ,toddler with his trike to theoctagenarian when he has returned to threewheels. Naturally, the separate items are notfully decided, and details of them will, nodoubt, be given in the Press from time totime ; but I understand much effort is tobe expended in linking the pastime withcountry life,' 'so giving the, beholder acontracted vision of what cycling can mean tothe public. Remember, cycling can be every-one's game, and that will be the main notionbehind the Rally, to widen the appeal ofthe bicycle which can give you so much forso little. I hope all cyclists will note thedates. All club folk will make this fixtureprominent in their run lists, for it is therider who encourages the public to ventureinto a field of pleasure endless in its variety.No doubt in later issues there will bemuch more to tell when the arrangementsare finalised ; but in the meantime book thedates, and if you are keenly interested getinto touch with the secretary, E. T. Bannister,C.T.C. Offices, 3, Craven Hill, London, W.2.

TS*

64

CYCLORAMA H. WB.yELEY

THE CYCLIST June, 19 51

4

Kingdom of BirdsONE of the many delights of country life

is that it brings you close to the kingdomof birds. And many are the varieties

which abound in this pleasant Derbyshirecountryside. Just now, I am revelling inthe return of the house -martins . . . thosedainty little birds which so many peopleconfuse with swifts. Back they come eachseason . . . to the very same corner in thebarn or shed, taking up their residence againas if they had never left these shores forsunny climes. Soon, the swallows, divinglike meteors in the sun, and gatheringtogether, later in the year, to hold their" conferences " prior to leaving us.Chaffinches, robins, fly -catchers, yellow-hammers abound . . . and at night thetawny owl takes up his position in the talllime tree and hoots mournfully in thedusk.. .

A Dunlop OccasionSCOTTISH cycling is going to be in the

spotlight of publicity this year, follow-ing the all-star track meeting promoted bythe Dunlop Rubber Co. Ltd. at HelenvalePark, Glasgow. An event of this nature,where leading professional and amateurtrackmen compete, is bound to give a stimu-lus to cycling generally, and one feels boundto congratulate Dunlop on its enterprise.But the great tyre firm has always been asponsor of " big sport " and readers mayrecall the famous meeting at Herne Hill,held in 1938, to mark " Dunlop Jubilee "year.

Faithful to the BikeIRECENTLY visited the home of a

" county magnate "-and his. residencecould quite justly be regarded as one ofMrs. Hemans' " stately homes of England."As I rode up the long tree -lined drive themagnate's big gleaming car was parked infront of the house. In a garage I saw twoother fine cars. And . . . I also saw a bicycle.

I CKLETONCa m braqesiii re .

A valacie of great antiquitylading close to the Essex.border .

I inquired from my guide as to whom itbelonged . . and was told with a smile thatit belonged to " His Lordship." Then myguide " opened out " and told me how " theboss " still loved a bike and, whenever hecould, ignored his cars, and rode into thelanes on his cycle. Somehow, I feel that thiswealthy man is not the only magnate whoremains faithful to the cycle ! Probably inhis far -away youth he had been a keenmember of a cycling club, and had neverlost the magical lure of a bike . . . a road. . . and freedom !

" Safety First " in the Village

IT is quite wrong to imagine that in the" heart of the country " there is no need

for " safety first " teaching. In the part ofthe country where I now live lorry trafficalong the narrow lanes is quite heavy, forthere are milk -collecting depots and quarriesin the vicinity, and riding a cycle calls forperpetual alertness. We have two goodenthusiasts in the safety first cause . . . thevillage schoolmistress and the village con-stable ! They drill the children in thesalient points of the Highway Code, and doall they can to promote safety on the roads.Come to think of it, I fancy that much morecould be done in the schools : so manykiddies now ride to school, and a little intelli-gent teaching in school would strengthen the" lectures " given at home.

Exit the " Tramp "

HOW rarely does one meet, nowadays, areal authentic " tramp "! Years ago,

as one travelled the English highways, it wasimpossible to go far without meeting several" wayfarers "-shod with incredible gapingboots, bundles on shoulders, tin cans (andfrying pans) attached to the person with oddbits of string ; picturesque . . . but quiteinsanitary. Miles and miles they plodded,from town to town, mostly sleeping underhedges or in old barns and sheds-occasion-ally " putting up for repairs " at somecasual ward. I suppose that the rationing

system, identity cards, and the tightercontrol of the individual have together spelt" finis " to tramping and tramps. I do notknow, but it is singular that one may nowride mile upon mile and never see a dirty,bearded, ragged fellow squatting by the road-side, paring a chunk of cheese with a jack-knife or mending some tattered bit of hisunhygienic clothing. Where have they allgone ? The question is intriguing. . . .

Beech), Bucks . . . for Famous MenBUCKINGHAMSHIRE is a county I

love. I love its glorious beeches, itswoods, its glades where in autumn the wood -fires burn with aromatic fragrance, its littleinns. And it is a county of the great:.Milton, the towering giant of English letters,lived at Chalfont St. Giles, and his cottageis still preserved there. At Olney once livedthe gentle poet Cowper-and it was on thevicarage lawn where he is supposed to havetamed those hares he so loved. Turn topolitics, and we find that the great Disraelilived at Hughenden in leafy Buckingham-shire, and if we saunter around that pleasantplace we shall doubtless muse upon greatdays and great achievements-of " Dizzy "securing the Suez Canal for Britain, of histriumphal return from Berlin, of pale prim-roses . . . the great man's favourite flower,still worn by the faithful when the 19th ofApril comes round. Finally, if we journeyto Jordans, we shall be in the country ofWilliam Penn, the founder of Pennsylvania.Great names . . . woven into a lovablecounty, where the noble beech trees are kings,and the quiet woodland glades beckon us intotheir cool shade. . . .

Inn Names

MY old-time love for the Englishits sign burns brightly still, and I am

constantly on the look -out, as I ride throughvillages, for curious and uncommon innnames and picturesque signs. I saw a signthe other day which is new to my modestcollection . . . the " Swan and Salmon." Itis in ancient Derby, and I do not think I haveever seen it before. " Swans "-both blackand white-are common enough. " TheThree Swans " is not unusual, but the com-bination of swan and salmon is new to me.In previous " Cyclorama " notes I havedeplored the scarcity of inn signs which havedefinite links with the cycle and cycling. Mycollection includes " The Bicycle Arms,"near Rotherfield, in Sussex, but there oughtto be far more inns dedicated to men of thewheel.

Kiss of the MorningAT this time of the year wise is the rider

who gets up early and cycles abroadwhile the earth is fresh and the air pure,and when field and hedgerow are sparklingwith dew. In the country folks know thatthe " best of the day " is in the early morn-ing, and I have taken a tip from old country-men, and often ride out just as daylightcomes streaking over the hills and the worldis very quiet. Then it is that one sees thebeauty of coppice, and meadow, and trees.Then it is that the birds sing most sweetlyin the orchard and hedgerow. Then itis that the young rabbits venture from thewarrens, and frisk in the first glint of thesun. An hour's ride, and I am more thanready for coffee and scones at Lilac Cottage,where Widow Cundall likes to fortify me formy ride home. . .

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