ASTRO - PHOTOGRAPHIC TELESCOPES

EDITOR : F.J.CAMA4

SEPTEMBER - OCTOBER 1950

THE NATIONAL AERONAUTICAL COLLECTION AT SOUTH KENSINGTON (SEE PAGE 27)

Small Water -power Plants

Hot -melt Flexible Moulds

High Vacua

PRINCIPAL CONTENTS

Britain's Progress in Aircraft Model Engineering Practice

Animal Glues Queries and Enquiries

World of Models Cyclist Section

THAT CLIP YOU NEED

IS MADE BY

Two very popular types, 80 and 81. In arange of sizes from 4" to 2" from stock.No. 300 is a very popular drawing boardclip with a host of additional uses.5/- a doz. (incl. P.T.) from stock.

N

WANT TO KNOW ALL ABOUT

SPRINGS? HERE IS THEMANUAL - 10/6 POST FREE.

Clips in everform

y shape, size and. . . steel clips, bronzeclips, stainless clips, little clips,big clips, clips made exactly asYou Want them. If you desire

cli

it we can designany kind ofp to Your own exact &peel&cation. (We've

been designingclipsfor 95 years !)

Sole MakersHERBERT

TERRYR

&tiSONS

London LTD.,EopircBirmingham

Manchester

H.'1 -.1.C,

IL

September -October, 1950 NEWNES PRACTICAL MECHANICS

S. TYZACKLONDON'S LEADING

& SON, LTD.LATHE AND TOOL SPECIALISTS

111--- *INN111/Drophead Tool Holder,complete with high-speed

3 -Jaw Self -Centring Drill steel tool bit. Size of Lathe farrier'.. Malie-Chuck. Key Type. Capacity shank i" x 9'16" x 4J". able iron body, steel screw0-l". Complete with No. 2 Size of bit 316" square. with hardened point.M.T. shank arbor. Price complete 12'6. Extra Capacity J' I' I' litool bits 1141. each. Price 1,8 2:- 211 3/-

011111111111111/Machine Knurling Tool,single knurl sta drd

06x 4cut.Size of shank ".I"nxai"

Price complete 911 Doubleknurl tool with swivelhead and right- and left-hand diagonal knurls, 17 6complete.

4' Self -Centring 3-lawGeared Scroll 1.0111,4Chuck. One piece body of Angle Plate 3.1" x 2' x 2',semisteel. nickel -Chromesteel scroll. Price 111'7.

1 1 1 1

accurately ground on facesand edges, fully slotted.Price 7/3.

:::.,-

nigh-Speed Lathe Tool'.accurately ground tocorrect angles. Set of six

....--,,,,,,,, -.sm.,-

27 Sliding. TailstoekDie -Holder.Reversible for,_....._

le.0

13.16" or 1' o.d.Circular diesaccurately turned

and finished.

tsNiPrice 186.

Vertiele Slide, swivellingtype, fully indexed forangular movements in bothdirections. Slide tableprecision ground. Table

.

4 in. Independent 4 -JawChuck

and slide supported by with reversible jaws, steel Prong Centre for wood,heavy iox type angle bodies, special steel jaw No. 1 M.T. Price 43.bracket. Table size 3" x V. case-hardened and ground. Screw Flange Chuck forPrice £4. Price 46'9. wood, No. 1 M.T. Price 6'9.BARGAIN TOOL LIST FREE AND POST FREE ON REQUEST341-343, OLD STREET, LONDON, E.C.1

1

TELEPHONES : CLERKEN WELL 8301 (10 LINES)

1950 JOHNSON PHOTOGRAPHICCOMPETITION FOR AMATEURS.

JOHNSONS hold a print competition twice a year. The currentone closes on 31st October, 1950. All amateur photographersmay enter. Any camera may be used. Contact prints or enlarge-ments may be sent. No entrance fee has to be paid and no entryforms have to be filled in. All you have to do is to stick a labelor title panel from a JOHNSON photographic chemical bottle orpackage on the back of each print you send in. No limit to thenumber of entries which may be submitted by any one competitor.Every type of .subect is eligible. Children, animal, home andholiday snapshots. Landscape, seascape, river or street scenes.Garden, flower or tree studios. Architectural, interior or table -top

subjects. Prints need not be mounted.Enlargements need not exceed whole -

£125IN PRIZES

Ask your dealer for a

leaflet giving fullerdetails. Look out someof your best prints andsend them in NOW. Youmay win one of the bigcash prizes.

3 prizes of £10 each

and twenty consolationprizes of 101- worth of

Johnsons chemicals.

ALSO A NOVICES CLASSWITH 13 SPECIAL AWARDS

FOR BEGINNERS.

2 prizes of ES each

8

plate size. Name of camera, size offilm or plate, developer used andexposure given should be recordedwhere possible. Write your name andaddress clearly in block capital letterson the back of each print. Do not sendthe negative, although we may wish tobuy or borrow it if you are a prizewinner.

CLOSING DATEOCTOBER 31

'rite waning prints, not the negatives, willbecome the property of JOHNSONS. All otherswall be returned if sufficient postage stamps areenclosed with the entry. All envelopes or parcelsmust be marked COMPETITION DEPARTMENTand be addressed to

JOHNSONS OF HENDON335 HENDON WAY, LONDON, N.'N.4

GAUGE 0" SCALE MODEL RAILWAYS

WRITE NOW for this NEWENLARGED CATALOGUEIts 40 pages include Model Locomotive,

in British Railways colours, entirely NewModels and additional accessories, etc.

The most comprehensiveGAUGE r 0 ' Catalogue yet published.

Price still only 11- (Quote ref. G0112) from

BASSETT-LOWKE LTD.NORTHAMPTON

London:

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Manchester:

28, Corporation Street

RATCHET SPANNERS

HUGE demand enables us tooffer " Leytool " Ratchet Spanners atprices little above those paid forordinary good quality spanners. Theysave time and money because theywork 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 fit15o 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, 45/,

ZOOA to atcytett70/11OR THE MOST UP-TO-DATE

AND EFFICIENT

DESIGN

PrecisionHand Drill

RatchetSpanners

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

Screwdriver signs. Write for FREEIllustrated Booklet.

40

LEYTONSTONE JIG & TOOL CO., LTD., High Road, Leyton, London, E.18Telephone : LEYtenstone 5022-3-4.

2 NEWNES PRACTICAL MECHANICS - September -October, 1950

I.C.S. TRAINED MENare in Greater Demandthan Ever-Maximum productiondepends on high technical skill, suchas that acquired by I.C.S. Students

TENS OF THOUSANDS MORETRAINED MEN ARE URGENTLYNEEDED NOW-BUT THERE ISNO WORTH -WHILE PLACE FOR

THE UNTRAINED

Ambitious men everywhere have succeeded throughI.C.S. Home -Study Courses. So also can you.The man with an I.C.S. Training inlisted below knows it thoroughly,And he knows how to apply it

AccountancyAdvert. Copy Wr't'gAdvertising M'g'mentAir and Vacuum

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any one of the subjectscompletely, practically.

in his everyday work.

Diesel EnginesDraughtsmanshipDrawing Office PracticeElectrical EngineeringElectric Power, Light-

ing, TransmissionTraction

Eng. Shop PracticeFire EngineeringForemanshipFree -Lance JournalismFuel TechnologyHeating and VentilationHorticultureHydraulic EngineeringIllumination Eng.Industrial ManagementJoineryLetteringMachine DesigningMachine -Tool WorkMarine EngineersMechanical DrawingMechanical EngineeringMine Surveying

Milling EngineeringMotor EngineeringMotor MechanicMotor Vehicle Elec.Municipal Eng.PlasticPlumbingQuantity SurveyingRadio EngineeringRadio Service Eng.RefrigerationSales ManagementSalesmanshipSanitary and Domestic

EngineeringSheet -Metal WorkShort -Story WritingSteam EngineeringStructural SteelworkSurveyingTelegraph EngineeringTelevision TechnologyWelding, Gas and Elec.Woodworking DrawingWorks Engineering

And most of the Technical, Professional, Commercial and Civil Serviceand Educational Examinations

(I.C.S. students preparing for Examinations are coached till successful)

If you need technical training, our advice on any matter concerningyour work and your career is yours for the asking-free and withoutobligation. Let us send you our special free booklet on the subject in which youare specially interested. DON'T DELAY. Make ACTION your watchword

The successful man DOES to -day what the failureINTENDS doing to -morrow. Write to us TO -DAY

Use this Coupon

INTERNATIONAL CORRESPONDENCE SCHOOLS LTDDept. 95, International Buildings, Kingsway, London, W.C.2.

Please send me the free booklet describing your Courses in

Name Age(USE BLOCK LETTERS)

Address

Addresses for Overseas ReadersAustralia : 140, Elizabeth Street, Sydney.Egypt : 40, Sharia Abdel Khalek Sarwat Pasha, Cairo.Eire : 13, Anglesea Street, Dublin C.4,India : Lakshmi Bldgs., Sir Pherozsha Mesta Rd., Fort,

Bombay.New Zealand : 182, Wakefield Street, 'Wellington.N. Ireland : 26, Howard Street, Belfast.South Africa : 45, Shortmarket Street, Cape Town.

ICS

A new solderFOR WORKSHOPAND HANDYMAN

CONTAINS 2 CORES OF FLUX NO EXTRA FLUX REQUIRED REPLACES STICK SOLDER,

FLUID AND PASTE FLUXES

IF DESIRED FLUX RESIDUEREADILY WASHES OFF WITHWATER

SO FAST THAT IT WILL EVENSOLDER BLUED SPRING STEELWITHOUT PRE -CLEANING

No. 10 KIT 21. each

sentIn case of

post free on

MULTECORE SOLDERS

SIZE 8CARTON

51. each

Available in 5/- retail car-tons (4 specifications)

or 2;- Multicore SolderKit contains 2 specifi-cations Arax Multicore

Solder and 2 specifica-tions Ersin Multicore

Solder for electrical wire totag joints. Now obtainable from many stores.

difficulty 5/- cartons or 2/- Multicore Solder Kitsreceipt of postal order or stamps.LTD., MELLIER HOUSE, ALBEMARLE STREET, LONDON, W.1

S.C. BROWNP's-eccIse On.

(5.)e,,t2Aei-e. /re eiC e/6For high Fidelity of Reproductionwith minimum orwear on the record

FIVE TYPES TO CHOOSE FROMThe above are designed and manufactured

to suit all types of pick-ups.

No. 1. " Miniature " jewel tipped needle for light -weight pick-up.No. 2. " Straight " jewel tipped needle for crystal pick-up.No. 3. " Trailer " jewel tipped needle for medium -weight pick-up.No. 4. " Knee Bend Trailer " jewel tipped needle for the older

heavy -weight pick-uD.No. 5. " Miniature Solid Sapphire " needle for light -weight pick-up.

PRICES :-Nos. 1-4, 10/1 each. No. 5, 13/4 each.

A "TIP" WORTH TAKINGAn interesting and instructive Brochure giving technicaldetails, valuable information and advice on the choiceof a S.G. Brown precision Sapphire Needle to suit yourpick-up, will be sent on request. Write Department " N "

TatoCA-,--wintrtclSHAKESPEARE STREET, WATFORD, HERTS.

Telephone : Watford 7241

September -October, 1950 NEWNES PRACTICAL MECHANICS

PHOTO COPYINGajw/BLUE PRINTS

As actual manufac-turers of all typesof sensitised photomaterials, Haldens arein a unique positionas print room sup-pliers. Materials forBlue Prints, DyelinePrints, Gas DevelopedPrints, Sepia Prints,"Ferazo" Blue Prints,Ferro Gallic Prints,etc.The brand names" Dyalyn," " Neut-ralyn," " Vaporax,""..Cyano," " Ferazo "are your guarantee ofcomplete satisfaction. Illustrated is the

" Ferazo " Develop-ing Machine. Writefor fully descriptive

leaflet.

OF MANCHESTER,44J. 'MALDEN & CO., LTD., 8, ALBERT SQUARE, MANCHESTER 2.

.> Bra,etes at London, Neweast e-oa.Tyne,Khata, Glasgow, Leeds and Bristol,

FRANWS 1 GLASGOW*...1111111111

SELECTED MISCELLANEOUS ITEMSPRISMATIC ELBOW TELESCOPES

This is a beautifully -constructed instrument by Cooke,Troughton and Simms, used for aircraft observation.Magnification 7 x. Weight 6 lbs. ... ... each 27 6

TELESCOPIC RIFLE SIGHTS (No. 64 Mk. I)Suitable for .22. No mounts available. ... ... each 35 0

ASSORTED LENSESParcel of ten assorted Lenses. Includes one dia.convex Lens, focal length 3in. One convex meniscusLens, 2Iin. dia., focal length 4Dn. 8 assorted smallconvex Lenses ... The lot 10 0

EX-W.D. PRISMATIC BINOCULARS, by Ross,Kershaw, etc. 6 x 30. Eyepiece focusing. These instru-ments have a wide field of view and brilliant definition.Every glass has been examined in our own workshops,and is guaranteed to be in sound optical and mechanicalcondition. Complete with web case and straps ...a 5 0(Leather cases available if desired 716 extra)

EX -GOVT. TERRY ANGLEPOISE LAMPS32in. fully extended. Fitted with small bayonet cap lamp -holder and Pygmy reflector. Ideal for fitting to benchor wall. Supplied complete with flex. New and unused 35 0

POCKET FOCUSING MICROSCOPESA precision instrument constructed in our own work-shops. The optical system consists of 8 lenses (4achromatic doublets). Definition is crisp and free fromcolour and distortion. Magnification 20 X ... ... 27 6

MASTER CONTACTORS TYPE 11-24 voltA precision mechanical device driven by a twelve-hourclock which makes and breaks contact 120 times perminute. Spark suppressors are built in. Contained inrubber -lined oak box. Brand new. ... ... 9 6

e4,,atia4, 7-4.667-73 SALTMARKET, GLASGOW,

PHONE : BELL 2106INSTRUMENT MAKERS AND DEALERS SINCE 1907

SATISFACTION ON ALL PURCHASES OR REFUND OF PAYMENT

0011/40100WOW00. 000

Agik.%

1

You will be amazed at the many jobs''you will do with new power, speed, con-

fidence and real enjoyment. The Wolf Cub is* more than an electric drill-it is the power unit,of all the kits you see illustrated. Once you ownthe 'Cub' a small additional outlay enables youto widen the scope of your activities to the ex-tent you desire.Think of the economy and thenew profitable pleasure that will be yours !There's never been anything like this before!

WOLF CUB 1"

HOME CONSTRUCTOR

ELECTRIC DRILL

HOME(tillC0000%t4S"

Lk"' KIT

Ask your tool suppliertoday for full detailsor write direct to:

WOLF ELECTRIC TOOLS LIMITED, PIONEER WORKSHANGER LANE, LONDON, W.5. Telephone: PERIVALE 5651-4

POWER UNITTO ALL THIS EQUIPMENT

WOLFCUB

HOMECOtISTRU

SAW KIT

WOLFCUB

NOMECOIISTINICVOR

DRILLING,GRINDING

ANO

POLISHINGKIT

* LOW PRICE CONVERSION SETSConverts Wolf Cub or any Kit to formcomplete Wolf Home Constructor Equip-ment at attractive low prices.

4 NEWNES PRACTICAL MECHANICS

OBJECT GLASS Ex -Army Telescope Objective, brand new in originalcarton. 2in. external diameter, screw -threaded, fecal

length about 5,1,in. Suitable for making small astronomical telescopes, 35/.range sights, etc. (Regd. post II-)

SENSITIVE TACHOMETERAs fitted to all British Aircraft,reading 0-5,000 r.p.m. andincorporates 4 : I gear box.Can also be used as I : I.The outfit consists of flexibledrive for connecting to crankshaft, motor, etc., 3 -phaseA.C. generator which shouldbe connected by 3 -core wireto the sensitive indicator.

Suitable for large or small horsepower installation and supplied complete withinstructions. Each set of instruments is tested by us before despatch, and all aremade by leading British manufacturers, Smiths, Record, etc. AG

Carriage Paid

ELECTRICAL EXPERIMENTER'S KIT A large miscellaneousassortment of heat-

ers, relays, chokes, condensers, indicators, resistors, plugs, etc. All new equipmentand made to Air Force specification. A 7 lb. parcel of useful spares for theelectrical or radio engineer or experimenter. No duplicate parts. 11/6(post free)

MECHANICAL EXPERIMENTER'S KITA large assortment of small aircraft parts such as flyinginstruments, mechanical and electrical parts, indicators,etc. Cost price from the makers over E40 per set -each parcel guaranteed to include at least three fineaircraft instruments such as air speed indicator, rev.counter, rate -of -climb and turn -bank indicators, etc.,etc. We have sold over 1,000 of these parcels to date.Weight approx. 14 lbs. (maximum forparcel post). (U.K. only, post free) 14/6

230v. MINIATURE MOTORSThese motors will run from 2001250 V. 50 cycles A.C.mains. Made by Sangamo for electric meters, and nowsurplus to meter manufacturer's requirements. Dimen-sions of motor Iin. diameter x Itiin. depth. Weightonly a few ounces, but rigidly constructed. Self-starting,no shunt or resistance necessary in circuit. Motorsupplied with ;in. geared shaft and three small feet

for fixing, or mounted on base -plate 21in. sq. with long chainof reduction gearwheels. Brand new. Motor only 12/6

or in frame with reduction gearing,post free 15/..

AFRO SPARES CO.(Dept. 83), 70-T711, W

September -October, 1950

"KINWESDRAW' GoMAT E RIA

We are the largest manufacturers of high-grade Drawing Instrumentsand Slide Rules in the British Empire, and our Kinwest DrawingMaterials have gained a reputation throughout the world for superbquality and accuracy. Insist on using only Thornton's for completesatisfaction.

Our illustrated Catalogue, which includes particulars of DrawingBoards, Tee and Set Squares, Scales, Drawing Instruments, Curves,Protractors, etc., is sent Post Free on request.

THOUITON LTDutauting .972A6Vtaineezt Sp ew:144,66

W Y.T44-ENJ-44AW.E. MANCS-if/TERTel WYThenshawe 2277 (4 lin%)

DUKE & CO.NEW PHILCO RADIO CABINETSBrown, 151-, plus 216 post.

EXTENSION Speaker Cabinets,walnut, metal grill, position forVlControl, with baffle for 10in. speaker.OUR price, 251- ; original price, 5 gns.

DUNLOPILLO CUSHION 5,32in. x I8in. x 2in. or 34in. x I5in. x 3in.,tapering to I fin., including postage 1216.DUNLOPILLO SEATS or backs,33in. x I5in. x 3in., wedge shape, or31 in. x I9in. x2/, in., moquette covered,plywood backed, 141- plus post.PLYWOOD, 3116in. Pre-war, 3ft. x2ft.. 316 ; or 3ft. x I7in., 216 plus post.VALVES. Special Offer, 6J7GTIG or6H6, 251- doz., 216 each, brand new inmaker's boxes. SP4I, 251- doz., 216

each. SP6I, 351- doz., 316 each. Alltested.SPEAKERS. 21in., 101-. (Specialsuper midget transformer, 616.) 5in.speaker, 101- ; Sin. with trans., 1216 ;

6in. speaker, 1216 ; 6in. with trans.,ISIS ; 8in., 1516; with trans., 181-,

10in., 1916 ; I2in., 3516.

SPEAKER, NEW, in extension'cabinet, 1416.SHORT WAVE SUPERHET 18

set. receiver, complete and tested.FREE pair of headphones includedfor 1716. NOTE -Set with a littlealteration makes first-class portable orcar radio. 1. F.'s 465 change -over to P.Coils for medium wave.H.T. BATTERIES, 180 v. tapped90 v., 21 v. bias, 1 L.T. All thosetested:so far are full volts. These aredespatched in sealed case, but are notguaranteed. 516, plus II- post.DOMESTIC RADIO KIT, in bakelitecabinet, 4 valve T.R.F. Universal orA.C. only for only E4 I5s. 6d., or inIvory cabinet 61- extra. Assembled,301- extra.CASH with Order please, and allow

sufficient for postage.STAMPS ONLY for lists.

219, Ilford Lane, Ilford, Essex.

SUCCESSFUL WOODWORKINGis the experience of all Myford Lathe users. The ML8 WoodworkingLathe, supplied complete with motorising unit for bench or cabinetmounting, motor -pulley, vee-belt, centres, hand -rest, 6in. dia. faceplateand all guards, costs LI6,I2S. 64. Once your Myford Lathe is installedyou can at any time add our specially -designed attachments which, allquickly mounted and dismounted and powered by the lathe motor, makethe ML8 capable of practically every other wood -working operation. Thusequipped, this lathe :

SAWS SANDS. PLANES REBATES

MYa e s

GRINDSGROOVESPOLISHESSPINS METAL

See your Tool Merchant for further information concerning this versatilemachine, or write to us for free coloured leaflets.MYFORD ENGINEERING CO. LTD., Beeston, Nottingham. Phone : 54222,3/4.

Y 0 Ucan become a first-classRADIO ENGINEERWe are spasia!ists in Home -Study Courses in Radio Engineering.Servicing, Transmission, Television, Mathematics and Radio Calculations.

Post coupon nowfor free bookletand learn howyou can qualifyfor well - paidemployment orprofitable spare -

time work.

(Post coupon inunsealed envelope

-1d. Postage.)

T. & C. RADIO COLLEGE

To R. Heath Bradley, T.C.R.C.,50, Harland Road,

Southbourne, Bournemouth.

Name

AddressM.63

WILCO ELECTRONICS204. Lower Addisconthe ltd., CroydonA.C. INDUCTION MOTORS. SinglePhase 1,425 r.p.m., all voltages, ideal for

workshop and:ndustrialuses. Heavyduty, silentrunning. Noradio inter-ference.

h.P. £6 56h.p. £13 17 3h.p. £8 8 7

Carr.andpack-10/-.

GEARED CAPACITOR MOTOR, 220.'240v. A.C. ao watt, size 7in. x 4in., 1.500 r.p.m.,with 300 r.p.m. on final shaft, standard footmounting, brand new, reversible, withcapacitor. 84.-, post 1-6.UN ISELECTOR SWITCHES, 25 way8 bank, 8 wipers, 37.5 ohms, 27/6. postBATTERY CHARGERS "IV ESTA I, [TEL"'Input 100 539 v. A.C. Outptit L2 v. 16 amps.,variable metered output, fused, worth £34.Our price while they last £10 10 0, carr. 10/,24 VOUT D.C. MOTORS with double endedshaft 2in. x 3in.. 10,6. Postage 1 -.THERMOSTAT SWITCH.- typein sealed glass tube. 2fln. lin. 30, deg.Cent. Ideal for AqUariums, 5- each. ,

VOLTMETERS. -0-300 A.C, Moving Iwo21in. Flush, 17,6 ; 34in. Flush or Surfaea,22/6 : 0-250 A.C. Moving Coil RectifierType, 311n. Flush.CLOCKWORK MECHANISW-Precls'omade movement adaptable for photographftiming, etc., with contacts making andbreaking twice per second. Brand new tosoundproof cabinet with thermostat tem-perature control. Price only 15/6.MASTS. TELESCOPIC. extending to Rift.in 7 sections. 15/0, Post 1.i-.THERMOS TAT. Satchwell 12in. stem,0:250 volts A.C./D.C., 10 to 90 deg.Cent. 35/-24 VOLT MOTOR with reduction gear andcam -operated switches, 1516. Post lb,WIRELESS FILM RECORDERS 'Int35 uvm. film with cutting head, etc.; Incor-porating a 230 volt Mains motor,CUTTERS STYLI!, 6!- per doz. "

i.

BOMB RELEASE UNITS, suitable .forPhotographic exposure timers, 1 secondintervals up to 8 seconds, 10/- each ; up to16 seconds, 15/- each. Post and pkg., 116.SPEAKERS. -P.M. 8in. Goodman, in wallcase, with transformer, Post & pkg. 2/6

Sperry Computer, Type BB. Ref. 10992 " M."This unit represents a

wealth of mechanical andelectrical components.Consists of : Over 100various precision gearwheels, helicals, rollers,spirals, levels, ratchets,worm drives, skew gearsand variable pitch 'wormgear. Precision pitchstabilizing gyro unit.Servo syphon unit withfour concertina type reser-voiAnti -Vibration Mtg. Reversible Friction Clutch. tub

rs, small bore servoes, servo switch.

Two 24 -volt D.C. 1.5 A. motors with pulleys shaft each end and reversing clutch mechanism.Selsyn 24 volt repeater motor (912282). Slow motion dials, counters, aneroid, capsules,shafts, springs, metal and flexible tubing, plus over 800 springs, washers, nuts and bolts,etc., etc., etc.The complete unit is enclosed in a metal box with removable side covers : 19 x 141 x 3/ins.finished in black crackle and suspended in a tubular metal cradle frame by four heavy dutyanti -vibration mountings. Weight 96 lbs.This unit was designed for use with the American TI Bombsight.

CLYDESDALE'S....n9/6 each CARRIAGE

PRICE ONLY PAID

230/250v. 50 Cycles A.C. Shaded Pole MotorH.313 (Right) Shaded Pole end thrust motor 1,500 r.p.m.at 11100 h.p. fitted with 51I6in. spindle bin. long. Threadedfixing lugs. Diam. 4 x 31 ins: Weight 51 lbs.'

CLYDESDALE'S !,arti. each POSTPRICE ONLY `14"0/ PAID

HI.314. This motor as above- but fitted with *in. screwshaft. 4 x 31 ins. Weight 4 lbs.

CLYDESDALE'S 02/6 each POSTPRICE ONLY ,a. PAID

S.R.2. Carefully balanced, rugged, and very efficient motor. Silen room tested. Can berun at gross overloads without damage.

CLYDESDALE'S 1125/ each POSTPRICE ONLY .ff PAID

S As for S.R.2, 2,000 r.p.m. Shaft diam. .1875 in. Steel. Silent room testedCLYDESDALE'S ,_240, / each POST

..PRICE ONLY 1...'6../ , PAID

September -October, 1950 NEWNES PRACTICAL MECHANICS 5

-CLYDESDALE *******************************************

Bargains in .Ex -Services .Electronic- Equipment

Repeater IMotor.

"ServoTubing.

bettricMotor.

Rheostat.

Anti -VibrationMtg.

ServoSyphon Unit.Fine wormgear withLeaden.

Pitch Gyro.

TubularSteel Frame.

rder direct from : 'Phone: SOUTH 2706;9

CLYDESDALE %P.;a. 2,Ala

.et,

Branches in Scotland, England and Northern Ireland

All these motors are ideal for gramophone, wire and tape recorders, fans or motion

it

46

* NEW *American Star

Identification InstrumentsA -N Type 1

An accurate instrument with which it is possibleto obtain positions of all the stars and planetswhich are included in British and AmericanAlmanacs or, alternatively, it can be used foridentifying or spotting stars.

The Northern or Southern sky may be viewedon the Star Base, so that, with the seven graphswhich are provided, the instrument can be usedin all parts of the world.

Originally manufactured for the U.S. Hydro -graphic Office at considerable cost, they are nowto be sold at a greatly reduced price.

As supplied to leading shipping companies andairline operators, at home and abroad.

An outstanding offer at Ss. each, complete inleather case with instructions.

Order early to avoid disappointment.

* LAWRENCES61, BYROM STREET, LIVERPOOL, 3

Tel.: C'ENiral 4430

41

43

48

42,41.

e.

UNUSED Ex-W.D. BARGAINFRACTIONAL 11.1'.

Ith II.P. BRANDSEW ELECTRIC

MOTORSMade by Hoovers.

EACH

Pet 37/6Carr.4.t to be confused with smaller, cheaper.ypes. Size llin. x 5lin. x 511n. Weight8 lbs. Volts 200-250 ; state A.C. or D.C.4000 r.p.m. Ideal for polishing, grinders,tc. Existing spindle Iln, diem.. fin, long.hil-purpose extn. spindles to screw- on.b6 pair extra.LX-ARNES HEADPHONE%

BRAND NEW AND BOXED.deal for Crystal or Valveets, hospitals, etc."OST fa TWO i'ER PAIRFREEc sq v PAIRS,

nv/

Insts., Dal. Arm. Units. Reed drive:orrug. alum. Diaphragms, dble. H/bands.Ift. cords and plug. Worth about 42,- pair.Uso makes telephone set by connecting.arpleces to any length twin flex.:iiENERATOR TOOL KITS. Complete inock-up chest fitted race extractor. Assem-sly block, 3 drifts. 2 box and I ring spannersor 500 and 1,030 watt generators. etc. 22'8nolu.

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[SEPTEMBER -OCTOBER, 1950

VOL. XVIII. No. 203

Owing to the paper shortage " The

FAIR COMMENT

HAVE received a large number ofletters on the subject of flying saucers.What are they ? Do they really

exist ? Are they frOm other planets ? Arethey weapons of 'war ? New forms ofradiosonde ? The fact is that flyingsaucers do exist, and the United Statesauthorities admit that they are responsiblefor them. Photographs are available showingthem in flight. From the tangled reportswhich have appeared in the Press no onewould be able to form an accurate opinionof what a flying saucer really looks like.These reports indicate that they vary insize from 250 feet to a few inches. Theyfly at all heights. Some are self-propelling,others are radio -controlled. They do notexude exhaust gases. They are silent, theycan poise and hover and travel at immensespeed.

It is known that in Maryland in theUnited States an American project has beenprogressing during the past three years. Asvarious experimental flying saucers are pro-duced they are released into the air and thiswould account for the varying reports as totheir size. These experiments are conductedby the United States Air Force who havenot released any statements concerning thebasis of their experiments. Facts aboutthese saucers were recently given in a broad-cast by Henry J. Taylor working in co-operation with the U.S. Military Authority.He told his listeners that the following wordsare stencilled on the saucers: " Militarysecret of the United States of America AirForces. Anyone damaging or revealing adescription or whereabouts of this missile issubject to prosecution by the United StatesGovernment. Call collect at once (followedby a telephone number and the address of a

U.S. air base). Non -explosive."Flying Saucers have been sighted in 39

of the 48 United States. One responsiblewatcher said that they appeared to be revolv-ing at about Zoo revolutions per minute at6,000ft. and travelling at from 500 to 700miles per hour.

Another man in Houston, Texas, pickedup a circular flat disc marked " U.S.A. classi-fied secret device. Notify Col. F. Hackett,Washington." Col. Hackett denied anyknowledge of the device. I have no informa-tion beyond that and readers may form con-clusions as valid as mine from the foregoing.

There have been many attempts in thepast to produce aeroplanes with truly circularwings, the design being based on the mis-taken belief that automatic lateral and longi-tudinal stability would be secured. Some ofthem were partially successful but they wereno more stable that the more normal types.

I have often thought that guided pilotlessaircraft such as the VI were wrongly con-ceived in that to achieve their object theydestroyed themselves. A considerable amountof expensive equipment is -.fitted to them.Surely it should be possible to design one onthe boomerang principle which at a pre-determined moment dropped its bomb andreturned to its base for further use. It will

NEWNES PRACTICAL MECHANICS 7

EDITORFJ. CAMM

Cyclist," "Practical Motorist," and Home Movies " are temporarily incorporated.

By The Editor

Flying Saucersbe seen at once that such a design could beproduced, and there is no scientific or prac-tical reason why it should not ; a consider-able saving of time, money and materialwould be effected. The principles ofthe boomerang are well understood and itmight pay to experiment with poweredboomerangs.

The most satisfactory power unit, ofcourse, would be a jet motor.

TELEVISION LINK WITH CONTINENTTHE first Continental outside broadcast

televised during the month of Augustmarks a considerable advance in televisiontechnique. It is the first time the Channelhas been spanned by microwave televisionlinks which carry the programmes in a seriesof hops from Dover to the roof of theLondon University building from whence itwas transmitted by land -line to AlexandraPalace, and retransmitted to London andMidland Regional televiewers. The Calais -London broadcast brought a programmetransmitted 90 miles away. There were threeintermediate stations on the route to London,in addition to the terminal stations at Calaisand Dover. A microwave link was used forthe first lap across the Straits of Dover, withthe transmitter zooft. above ground in thetower of the Town Hall at Calais, and thereceiver on a mast at Dover. Another micro-wave link carried the signals from Doverover the 26 miles to Warren Street, nearLenham. The next stage from WarrenStreet to Harvel, about 18 miles, wasaccomplished with a V.H.F. link. FromHarvel, which is near Wrotham, the signalscarried the last lap to London, where thereceiving equipment had been installed onthe London University Senate House inBloomsbury. From there the signals wentby cable to Alexandra Palace, having

;ravelled a distance of 95 miles in fourstages.

The portable microwave television link,such as that produced for the purpose byStandard Telephones and Cables, Ltd., is afrequency modulated S.H.F. system employ-ing carriers of the order of 4,000 mega-cycles, and operating between points withit

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visual range of each other and not normallymore than 3o miles apart. For transmissionsover longer distances one or more repeatersmay be used. These comprise, without modi-fication, a standard receiver for demodulatingincoming signals and a transmitter for re -modulating the resulting video signals andpassing them on in the desired direction ata frequency shifted from that of the previouslink of 4o megacycles to prevent mutualinterference.

The complete mains -operated transmittersand receivers are transportable, being brokendown into a. number of portable units.Except in the case of semi -permanent receiv-ing terminals, equipment is designed for usein a motor van. The 4ft. paraboloid trans-mitter and/or receiver assembly may bemounted on a spigot on the roof so that noequipment need be removed from the vanfor short and unobstructed radio linkages.Where transmission paths are not clear ofbuildings and leafy trees, it is necessary tofind a more elevated or suitable vantage point.

The rapid developments of the past year -in television radio links have produced light-weight equipment which can be taken to thescene of action and set up immediately.Several of these units can be used in tandem,the picture being transmitted from one toanother, thus permitting much greater dis-tances to be covered. Experimental workonly started last year, and two sets of equip-ment were used successfully for televising theBoat Race this year.

THE " PRACTICAL TELEVISIONRECEIVER "

WE have produced in the PracticalTelevision laboratory a highly effi-

cient 18 -valve television receiver which canbe built by any amateur from the instruc-tions given in that journal. Back issues ofit, so successful is our new companionjournal, are unobtainable ; for the conveni-ence of readers unable to obtain the issuescontaining the instructions we have produceda booklet at 3/6, or 3/9 by post, giving fullinstructions, theoretical circuits, wiring dia-grams, list of components and photographsof the instrument both finished and incourse of construction. Copies may beobtained from or through most newsagents,or from the Publisher, Book Department,address as on this page.

NEW VOLUME COMMENCESVOLUME 18 commences with this issue.

As in the past, indexes have beenproduced for Volume 17, comprising issuesdated October, 1949, to August, 595o,inclusive for rod., by post. It will beobserved that owing to the no overtimeworking in the printing trade we were com-pelled, in order to make up for lost time, tocombine the September and October issues,and so Volume 17 contains only elevenissues. This present September/Octoberissue therefore commences Volume 18. It ishoped that readers will take advantage ofthis service to our readers.-F. T. C.

8 NEWNES PRACTICAL MECHANICS September -October, 1950

Small Water-power PlantsConstructional and Operational Details of Water Wheels and Turbines

Suitable for Small Streams and RiversTHERE are many places in the British

Isles, especially in remote districts,where small streams and rivers lend

themselves to power development on asmall scale, and those who wish to achievethe best results without waste of money maybe interested to learn a few facts helpful tothem in planning a water -power scheme.

The first and most important task is to

1.-Simple measuring weir with triangularnotch.

carry out a careful survey of the proposedsite, because without an accurate knowledgeof local distances and differences of levelit will be impossible to plan anything.There is no need to use expensive instru-ments or complicated methods ; the wholearea can be surveyed with a prismatic com-pass and a good tape, using the standardmethods as laid down in any good book onelementary surveying. Important levelpoints should be established with the aid oflevel and staff, and such instruments canprobably be borrowed from a contractor, orfrom the local county surveyor. In anycase, it would be wise to have a talk withthe local surveyor at the outset, just to makesure that no water rights are being infringed,and that the work proposed will not interferewith local amenities. All this kind of pre-liminary discussion will go with a swing ifthe designer and builder has clear andaccurate drawings, and can explain everydetail of what he intends to do.Gauging Stream Flow

The poet tells us " that even the weariestriver flows somewhere out to sea," so thatevery stream and river has a gradient andthis should be measured accurately, as muchwill depend upon this in gauging the flowof the stream. Our next task will be togauge stream flow, and several methods areavailable for doing this, but it should beemphasised that every method has its ownparticular application and that the mainobject of flow measurement is to obtain asound and accurate idea_of what the flowwill be over a considerable period. Thereare cases where even large water -powerschemes have given disappointing resultsin practice because the flow measurementswere not taken over a sufficiently long periodof time.

For very small streams, a direct measure-ment of flow can be made by means of acalibrated collecting tank or receiver, butthis is not a satisfactory method, and canonly be used for very small flows. In thecase of a wide stream or small river, measure-ment of flow is by means of a current meter ;this is a standard type of surveying instru-ment, and comprises a small horizontallymounted wheel with conical buckets whichis suspended from a cable and measureswater speed by a simple electrical contacting

By ROLT HAMMOND, A.C.G.I., A.M.I.C.E.

device. The cross section of the strewill have to be measured accurately andplotted to scale, and water -velocity readingswill then be taken at, say, ten feet intervalsacross the width of the stream ; any goodtext book on hydraulics will descril:e themethod used for measuring flow in thismanner.

Failing the ability to borrow a currentmeter, stream flow can be measured by meansof floats, their time of travel being measuredover a given distance by stop watch, andtheir position picked up by suitablie observa-tion.

A Measuring WeirFlow of a stream can be accurately and

conveniently measured by constructing a weiracross the stream and measuring the flowthrough a notch. The water upstream ofthe weir should be deep enough to avoid anyperceptible velocity of approach to the weir,because this will lead to inaccurate readings.The triangular or vee-notch is the most suit-able type of measuring weir, because relation-ship between wetted perimeter and arearemains constant for all heads, but careshould be taken to ensure that the sides of

meadRace

TailRace

4 e

Part of Casing RemovedTo Show Vanes

Fig. 3.-Diagram snowing general arrange-ment of an undershot water wheel and sluice.

the notch are equally inclined to the vertical.The vee-notch shown in Fig. I may be madeof hardwood but if it is to be in positionfor a long time, then it would be better toline the sides of the notch with stainlesssteel, as wood is liable to be damaged byfloating branches and other debris. If thenotch can be sited in a place where it is notlikely to suffer from disturbance, then somuch the better.

The discharge Q incubic feet per second overa triangular notch isgiven by the formula:Q =4/15 k.w.h. -

where w, h and g are infeet units, the latter beingthe acceleration of grav-ity. k is a constant,which varies from 0.59 to0.62, according to theangle a, being 0.59 whenthis angle is a right angle,and in this case w = zhand the above formulathen becomesQ=o.3 1120i cubic feet

per minute, where h is in inches and k is0.59.

The notch should be carefully levelledwhen it is installed, and the edge of thenotch must be sharp, otherwise the readingswill be quite inaccurate. Measurement ofhead can be made on a gauge in the bed

of the stream somedistance upstreamfrom the weir. It iseven better practiceto provide a stillingchamber in the formof a glazed earthen-ware pipe set on endin a bed of loosestones. Fig. 2 showsa hook gauge, whichis a very convenientand accurate instru-ment. This can bemade up from a

Fig. 2.-A hook micrometer head orsimilar device, theexact level being re-

vealed when the hook just touches the surfaceof the water from below. It may be worthwhile investing in complete autcmaticrecorder gear, such as that made by the LeaRecorder Company, Ltd., of Manchester.

Another very useful method of measuringstream velocity is by no means a pitot tube,the lower end of which is immersed in thestream and left open, the water rising in thetube above the surface of the water. Thevelocity is given by the approximate formula

gauge.

V= LTV h. An instrument known asPerrodil's hydrodynamometer has also beenused with success ; this measures the velocityof a stream by the torsion which is producedin a wire by the pressure of the wateragainst a disc mounted on an arm at rightangles to the wire. The velocity is given bythe formula V=c V a, where a is the angleof torsion and c is coefficient, which is foundby experiment, or may be calculated fromthe coefficient of torsion of the wire. It isclaimed that this instrument is very sensitiveand can be used with success for measuringvery low velocities.

These are but a few of the methods usedfor measuring stream and river flow., butin case the reader should require moredetailed information, he is recommended toconsult " Stream and Channel Flow," byE. E. Morgan, published in 1937.Designing the Plant

Having obtained an accurate idea of flow,we are now faced with the problem of design-ing the plant, and the first essential is todecide on the best type of water wheel or

.4/

Fig. 4.-Section and plan diagrams of a reaction turbine.

September -October, 1950

turbine to adopt. For heads up- to about6ft., the undershot water wheel is a goodproposition, and Fig. 3 shows the generalidea. This wheel is a kind of turbine, andthe designer should aim at setting the vanesat such an angle that the water will enterand leave the turbine or wheel smoothly andwithout shock. The best speed for the outerends of the vanes is about 55 per cent. of thatat which the water enters the wheel, althoughit can vary from 5o to 6o per cent. withoutdisadvantage. The diameter of the wheelshould be about three or four times the head,so that we shOuld have a 24ft. diameterwheel for a head of 6ft. It is interestingto note that a wheel of this type erected inAngouleme, France, in about 1847, attainedan efficiency of about 68 to 75 per cent., sothat the undershot wheel is certainly worthconsidering for a small power development.Suitable gearing would probably have to beinstalled if the wheel were to be used fordriving a dynamo.

The selection of the most suitable turbinefor the scheme is a very important matterto decide, but before this can be done it isnecessary to understand what is meant bythat very useful factor known as " specificspeed." This is used as the basis of com-parison for water turbines, and has beendefined as the speed at which the turbinewould run, at its designed efficiency, undera head of 1 foot when reduced in size so thatit would produce one horsepower under thathead. An impulse wheel of the Felton type,used for high -head plants, and not likely tobe of interest to us in this present article,has a specific speed varying from 55 to 3o,the corresponding specific speed for a verylow speed Francis turbine varying from 5oto 70.

Specific speed is given by the formula n;=nA1 N/H5/4 wherein n is the speed of thewheel in revolutions per minute, N is theoutput of the wheel and H is the head onthe wheel. These facts being known, thespecific speed is then calculated, and if themakers are given a note of this they will beable to recommend the best type of turbineto conform to these figures, and thus toensure the best operating efficiency. Thesemakers have curves which show the highestspecific speed that can safely be employedat a given head and with given suctionconditions.

The most usual type of turbine for lowand medium heads is the reaction turbine,which consists of four main component parts,namely: the casing, the guide apparatus, therunner and the draft tube ; in Fig. 4, Aindicates the runner, B the guide vanes(which are turned by the governor mechan-ism as the speed varies) and C is the drafttube. The latter enables the turbine to be

Fig. 6.-Alternative arrangement for a low -head installation. "

NEWNES PRACTICAL MECHANICS 9

Head

Shaft

Race

Turbinea

Tail Race

4 <7 0 .

Fig. 5.-Section of a low -head installation.set above the level of the tail wa er withoutloss of head due to its elevation. By havinga suitable taper on the draft tube, much ofthe kinetic energy of the water leaving therunner can be recovered. This is not ofvery great importance in turbines of lowspecific speed, but for units of high- specificspeed, up to a quarter of the energy in thewater may be recovered in the draft tube, inwhich case its design assumes greatimportance.

Type of SettingHaving obtained our

turbine, we next haveto consider the mostsuitable setting, andthis will be determinedby the manner inwhich the waterreaches the turbine.In a low head installa-tion, water will reachthe turbine throughan open flume, asshown in the twoalternative arrange-ments in Fig. 5 andFig. 6. In the former,the turbine itself hasno casing, and ismerely set at the bot-tom of an open chamber ; the latter tur-bine also has no casing and is set at the sideof the flume.

In Fig. 7 we have a larger type of thesame turbine, that is of the reaction type,with the runner entirely encased and thewhole installation set in a mass concretefoundation which forms part of the powerstation. This refers more to the larger typesof plant, but a modification of this would bevery suitable for a small turbine installationwhere the head might be as much as zoo feet,as in the case of a Scottish burn with asteep gradient. In such a case, the waterwould be collected in a forebay at the topof the stream and led down the mountainside in a pipe, with concrete anchor blocksholding it in position at intervals.

Regulation of this kind of turbine isaccomplished by moving the guide vanes B(Fig. 4) which admit more or less water tothe turbine. The most satisfactory type ofgovernor is the automatic oil -operated servo-motor mechanism, and in modern plantssome form of centrifugal pendulum is usedto control the admission of oil under pressureto the actuating cylinder of the guide vaneoperating gear.

Water PipedFrom

Head Pace

I1

General ConsiderationsAll mechanical and electrical gear for this

type of plant should be obtained from special-

ist firms, but the man who is fortunateenough to have a stream on his propertycan do a great deal of what may be termedthe civil engineering work himself. More-over, a man who is a good mechanic orwheelwright can make a very good under-shot water wheel which will serve him wellAnd pay a good dividend.

Strainer RacksHe can also make simple sluice gates and

strainer racks, the latter being very import-ant in order to avoid any possible damage tothe turbine. In designing a pipe line for arelatively high head, a specialist should beconsulted, and it is worth spending a fairsum on this because great danger may arisein a pipe line owing to accidental water -hammer effects. Again, he will have toobtain valves and similar accessories fromspecialist firms, but probably a great deal ofthe equipment can be bought second hand.For a low head plant the sluice valve is suit-able, but for higher heads we must employthe Lamer Johnson or English Electric types.

Expansion and ContractionA very important point to be watched in

designing the pipe line is to make provisionfor expansion and contraction between theanchor blocks due to changing air tempera-ture. An empty pipe in the hot sun reachesa temperature far above that of the ambient

Fig. 7.-A larger in-stallation using a headof water up to 2ooft.

Turbine

air. In solid rock there is no difficulty aboutgetting a good foundation for the anchorblocks, but these foundations should be keyedin with rag bolts or reinforcing bars, setin cement grout, in holes drilled in the rock.

Consult the MakersIn any water power development scheme,

however small, it is wise to consult turbinemakers who have a vast experience on whichthey are able to draw. The constructionalwork is mainly common sense, but that tooshould be done in consultation with the tur-bine maker, who can give very good advicein this respect.

WORKSHOP CALCULATIONSTABLES AND FORMULA

Ninth Editionby F. J. CAMM

A handbook dealing with methods of calcula-tion, solution to workshop problems, and therules and formula necessary in various work-shop processes. It contains all the information

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From all booksellers, 6/- net,by post 6/6 from the publisher,

GEORGE NEWNES, LTD. (Book Dept.),Tower House, Southampton Street, W.C.2.

melting/ - to avoid localoverheating whichmay char and decom-pose the compounds.Frequent stirring isnecessary, and thisshould be done slowlyto avoid forming airbubbles which are noteasy to remove. A lidmust be provided forthe melting -pot, andthis should be kept onat all times, exceptwhen stirring or pour-ing. Aluminium, glass,enamelled iron orstainless steel vesselsare suitable for melt-ing the compounds ;copper vessels shouldnot be used. Electric-ally -heated jacketedmelting - pots a r eobtainable for melt-ing large quantities ; these are ther-mostatically controlled, and require verylittle attention in use. Smaller quantities canbe melted in a glue pot, or porringer, withthe outer vessel left empty, or filled withparaffin wax or powdered graphite. Steam -heated jacketed containers are suitable formelting the compounds if steam pressure ofSolb. per square inch can be exceeded.Water baths are not suitable. Electric orgas -cooker ovens can be used to heatthe compounds at temperatures of 16oto rfio" C. (32o to 356* F.). Very smallquantities of the compounds can be meltedover an electric hot -plate or a gas -ring, if anasbestos mat is used and the hot -melt stirred

A group of moulds and casts ; moulds in background were formed bypouring ; moulds in foreground were formed by dipping. Two of themoulds are peeled back to demonstrate elasticity. Dark castings arecold -set resins ; light castings are plaster. (Photo : Vinyl Products, Ltd.)

frequently. The " Vinamolds " are suppliedin slab form, and whatever kind of melting -pot is used, the compounds should be cut intosmall pieces to facilitate even melting, or theycan be broken down by passing strips of thecompound through a mincing machine.

Pre-treatment of ModelsPre-treatment of non -porous models made

of metal, glazed earthenware, china or glassis not necessary before pouring the hot -meltcompound, but they should be warmed beforepouring to prevent chilling of the compound,and in the case of glass or china, to preventthe model cracking. Porous objects ofplaster, cement, earthenware, etc., require

10 NEWNES PRACTICAL MECHANICS September -October, 1950

Flexible Mould CompoundsThe Use of Vinyl Elastomers for Hot -meltCompounds By F. J. CHRISTOPHER

HOT -MELT compounds are being usedin place of gelatine for forming flexiblemoulds. The compounds, which are

known as " Vinamolds,"* were developedand are manufactured by Vinyl Products,Limited. They are based on a vinyl resin,and can be melted down to a liquid to bepoured around articles of plaster, glass, metal,earthenware, pottery or china to form flexiblemoulds of great strength for the productionof casts of plaster, cement or cold -set resins.

The hot -melt compounds are thermo-plastic, completely water-resistant, and donot shrink or split as does gelatine or glue.They are fully recoverable, and are notaffected by the phenol -formaldehyde -typecold -setting resins, or by plasters with a highlime content which heat while setting.Because of their tensile strength and flexi-bility, casts with deep undercuts can beremoved from one-piece =bids withoutdamage to the cast or mould, and hundreds ofperfect casts can be produced before the lifeof the mould is expended when it can beremelted for further use.

" Vinamolds " are produced in threegrades of flexibility Zsee table), and a fourthgrade is being developed. Selection of thecorrect grade depends on the shape and sizeof the object used for a model. The highlyflexible grade (HMC. 776) is suitable forforming moulds for small compact objects.The fairly rigid grade (HMC. 21) is suitablefor forming moulds for long, slender objectssuch as the column of a table -lamp stand.The intermediate flexible grade (HMC. 774)is suitable for forming moulds for medium -size objects such as book -ends, small figures,statuettes, etc. Cased moulds may be neces-sary where the weight of the filling is likelyto cause distortion,

Melting the CompoundsThe " Vinamolds " are true gels and

liquefy when heated, but their thermal con-ductivity is low, and care must be taken when

Registered Trade Name

Demonstrating the remarkable elasticity and tensile strength of " Vinamold." Mould isone used to cast indian head plaque : parts of mould are less than a quarter of an inch thick.

(Photo : Hotnecrctfts.)

A small mould cut in half to show cast. Itis not necessary to cut small moulds of thistype ; mould has been cut to illustratethis article. (Photo : Hontecrafts.)

treating before pouring the hot compound ;they should be immersed in molten paraffinwax to drive out trapped air and to seal allpores, or given a coat of a good celluloseenamel ; this pre-treatment is necessary toprevent blisters from forming by heat expan-sion. Faithful reproduction of even thefinest details of the model is a feature of the" Vinamolds," and small blemishes on themodel should be carefully repaired beforemould -making takes place. A reproductionof a plaque showed a faint hair -line scratchwhich was hardly distinguishable on theoriginal.

The model should be placed in a containerof glass, metal, card, wood, plaster, etc.,

September -October, 1950

Removing a cast from a one-piece mould.'` Cast is plaster, mould is "Vinamold" HMC.774.

(Photo : Vinyl Products, Ltd.)

before pouring. The top of the containershould be slightly larger than the base tofacilitate easy removal of the formed mouldfrom the container, and the container shouldbe deeper than the model to allow for a slightshrinkage of the compound in setting. Themodel can rest on the bottom of the Con-tainer or it can be suspended upside downinside the container. The liquid hot -meltshould not be poured directly on to themodel ; the flow should be directed againstthe side of the container to rise slowly roundthe model, and pouring should be uninter-rupted. Small moulds can be formed bydipping the prepared model in the liquidcompound, allowing it to cool, and dippingagain until a sufficient wall thickness hasbeen built up. In most cases a wall thicknessof a quarter of an inch is sufficient, but thisdepends on the size and shape of the model.

One-piece MouldsOne-piece moulds can be formed for all

objects unless they have elongated projec-tions such as in the " Javelin Thrower " (thejavelin), or apertures such as in a figure witharms akimbo (the holes between arms andbody). Where the filling hole is smaller thanthe bulk of the model, the mould can becut open at one side to allow easy withdrawal

NEWNES PRACTICAL MECHANICS 11

of the cast ; a rubber band should be used tohold the mould together for refilling. Mouldsfor models with apertures or projections canbe made in two or more parts by attachingthe base of the model to the side of thecontainer, and by pouring the melted com-pound to the level of the parting line, andallowing the hot -melt to cool to roomtemperature before again pouring the com-pound to cover the model. French chalkshould be dusted on the surface of thedivision level if the fairly rigid grade(HMC. 21) is used, but the other two gradeswill not stick and will part easily. Anysmall blemishes in the mould can besmoothed out with a heated knife blade.

Casts of Cement or PlasterTreatment of the moulds is not necessary

before casting as neither plaster, cement, norcold -set resins will stick to the mould. Inmaking casts of cement or plaster, the mixture

shaking the mould so that the slurry coatsthe mould as it sets. It may be necessaryto do this several times to build up a wallthickness of sufficient strength. Mouldsshould be flushed out with water after useto remove any loose particles of plaster orcement.

Cold -set resins are made by mixingsynthetic resin with a hardener ; the mix-ture can be poured directly into the mouldwhich does not require pre-treatment: Care

TABLE OF GRADESVinamold VinamoldHMC.zr HMC.774

Softening Point(Ring and Ball) 131° C. ' 139° C. 136° C.

Liquid at .. 13o to 145 to 145 to155° C. 150" C. 150° C.

Viscosity of melt medium low lowElasticity .. fairly

rigid

VinamoldHMC.776

flexible highlyflexible

THE COMPOUNDS SHOULD NOT BE HEATEDTO TEMPERATURES OVER zoo' C. (392° F.)

Combination of a broken plastic ashtray and glass paperweight. Container for mouldwas stiff card ; sides have bulged in pouring, but cast is unaffected.

(Photo : Homecrafts.)

is poured into the mould and entrapped airin deep undercuts is removed by stirring themixture and by tapping the sides of themould ; if there are any very deep undercutsit may be necessary to make air vents in themould. Hollow casts can be produced byinserting a core of " Vinamold " whichshould be withdrawn when the cast has set,or by mixing a slurry of the casting materialand partly filling the mould with this-

should be taken to remove entrapped air.The cold -set resins gel quickly, but they canbe cured if so desired by placing the filledmould in an oven heated to a temperatureof 75' C. (167" F.). There is a slight shrink-age of the cold -set resin of .04 during setting.After removal from the oven, the mouldshould be allowed to cool before removingthe cast ; premature withdrawal may damagethe mould in its softened state.

Reaction SolderingA Process of Coming ImportanceTHEY call it " reaction " soldering

because it results from a chemicalreaction which is made to take place

between the two metal surfaces which areto be joined together. It would, however,be better to use the term " chemicalsoldering," because such an expression ordesignation is more clearly indicative of thenature of the process.Metallic Chlorides

Reaction or chemical soldering first cameinto practical use just before the beginningof the last war. It made slow progress atfirst, and even now its use is not widespreadfor the reason that it is only really adapt-able to certain types of soldering. Variousmixtures of metallic chlorides and bromideshave been used, but the mixture found tobe most efficient is one of zinc chloride,ammonium bromide and sodium fluoride.These ingredients are intimately mixedtogether and stored in a tightly -corkedbottle. The zinc chloride is very deliquescent,or moisture -absorbing. Consequently, themixture will never be dry. It will alwaysresolve itself into a paste. Hence, it mustbe kept in well -corked bottles. Do not storethe mixture in, glass -stoppered bottles. The

By J. F. STIRLING

zinc chloride can often act as a peculiarlyefficient adhesive for glass stoppers inbottle -necks, and much difficulty is oftenexperienced in extracting stoppers frombottles containing this material or admixturesof it.Method of Using

For reaction soldering, the parts arecleaned in the normal manner. No flux isneeded because the soldering mixture acts asits own flux. The mixture is smeared thinlyon both contacting surfaces, which are thenbrought together in firm but not too tightcontact. The joint is then heated eitherwith a bunsen burner or with a small blow-lamp. The result of the heating is a complexchemical reaction which produces metalliczinc on the contacting surfaces. Theliberated zinc is in a molten condition. It" keys " well to the metal surface and formsa very strong joint. In fact, the joint thuscreated is usually stronger than that madeby ordinary solder, and it will stand up toa higher temperature than will the normalsoldered joint, the melting -point of zincbeing 418 deg. C. (787 deg. F.).

The reaction -soldered joint must, ofcourse, be well washed in warm water to

remove the remaining salt encrustationswhich cling to it. If this washing is notthorough, any remaining traces of zincchloride will set up corrosion of the joint.

The proportions of the three ingredientsof the soldering paste are capable of muchvariation. Usually, the mixture shouldcontain equal parts of each ingredient,although some workers may prefer to keepthe zinc chloride in excess, since this isreally the main active ingredient of the pasteand the ingredient from which the solderingmetal is derived. Potassium bromide maybe substituted for ammonium bromide, butthe latter gives better results and at a lowertemperature.

For Large WorkThere are two disadvantages of the

process. The first is the fact that copiouswhite fumes are evolved during the heatingof the joint. The second is that the methodcannot be applied to really fine work, suchas the joining of thin wires and metal foils,since these would tend to melt or oxidisecompletely during the heating. For anyreally substantial soldering job, however, theprocess is convenient and easy to work. Itis best operated on copper and brass, but itcan also be used on aluminium and itsalloys. It was indeed, in connection withthis type of work that reaction or chemicalsoldering was first devised.

12 NEWNES PRACTICAL MECHANICS September -October, 1950

Animal GluesSome of their Advantages as Compared with Synthetic Resin Glues

IN a recent article in this journal Mr.D. N. Buttrey, M.Sc., wrote about syn-thetic resin glues as ideal for use in the

home workshop. In so doing he made criticalreferences to animal and fish glues. If theauthor had contented himself with simplydescribing the advantages of synthetic resinglues and had not attacked animal and fishglues then his article would have been a fairtechnical contribution.

Immortal CraftsmenUnfortunately, however, some of Mr.

Buttrey's assertions are rather misleading.For this reason the matter cannot be passedover without a truthful statement of the facts-in justice to all manufacturers of animaland fish glues. In the first place, the factthat such immortal craftsmen as Sheraton,Hepplewhite and Chippendale used animalglues in the construction of their superbfurniture is evidence of the time-honouredsupremacy of animal glues. For not only foryears but for centuries the magnificent piecescreated by these craftsmen have remainedfirm in all their joints.

Does this fact suggest that with animalglue: " Invariably the glue line is the weakestlink in the assembly "; or " Embrittle withage "; or " Is often attacked by bacteria ormould growth " ? Further, does it suggestthat " shrinking during drying and ageingcauses gap -filled joints to craze and crackon the glue line with consequent weakeningof the joints " ?

The evidence provided by the Sheraton,Hepplewhite and Chippendale masterpiecesshould be quite sufficient to. repudiate flatlysuch misguided criticisms of the effectivenessand " lastingness " of animal glues.

Some AnomaliesBut there are other points in this matter

which should be dealt with not by the nega-tive method of " defending " animal and fishglues-they need no defence-but in exposinga few of the anomalies of Mr. Buttrey's casefor synthetic resin glues. (I shall not dealwith fish glues in this article because theseadhesives are entirely different and are rarely,if ever, used for wood -jointing.) What, then,are the anomalies to which we refer ?

Mr. Buttrey suggested that there are manyuses to which both phenolic and urea formal-dehyde resins could be"put in the " homeworkshop "-but let it be made perfectlyclear to anyone who wants to use theseadhesives for home use that he will find themextremely difficult to obtain in smallquantities. There are several reasons whymanufacturers do not make these glues avail-able through the normal retail channels:

(a) Risk of dermatitis from contact ofthese compounds with the skin. In fact,industrial users are obliged to provide specialprotective creams to safeguard the hands oftheir workpeople.

(b) The limited shelf-life-Mr. Buttreysays 3 months in a cool place-is a manifestdisadvantage to both stockists and prospectiveusers. One needs little imagination toappreciate the intricate marketing problemsinvolved in selling a product that has topass through the normal wholesale and retailchannels and yet be used within 3 months!It is assumed, of course, that all who handlesuch glues have taken good care to see thatmeantime it is kept in a cool place " !

(c) Most synthetic resin glues have a shortpot life once the hardener has been added.Typically: at so° F., 3 hours; at 6o° F.,

By W. E. FLETCHER, B.Sc., Ph.D.

hour; at 70° F., 45 mins.; at 80° F.,3o mins.

Admittedly, this is not a particularlyserious disadvantage under factory condi-tions where production can be geared tomeet it, but for the handyman or ordinaryhome user the disadvantage is, of course, avery serious one.

(d) Assuming, however, that the amateurdoes use synthetic resin glues, he will get anunpleasant shock when, if for any reason, hewishes to plane any part of the woodworkwhich has been glued with synthetic resins.They set hard and brittle and can have nobeneficial effect on the sharp cutting blade ofthe plane! Moreover, they actually changethe character of each piece of wood intowhich they impregnate, adversely affectingits natural resilience, and some evidence indi-cates that under stress the wood may there-fore break at a lower value than if no resinwere present. Any modern veneerers willgive evidence as to the cracking of the woodveneers when adhered by synthetic resins.

Animal glues, on the other hand, evenwhen thoroughly set, are relatively " flexible "and retain this property indefinitely.

There is some truth in Mr. Buttrey's re-marks to the effect that " animal glue rapidlydisintegrates in water and pieces separate."

But this is not really an important criticism,because where water-resistant joints arerequired-window-sills, doors, gates, etc.-protection is almost invariably provided bypaintwork or varnish, and no other protectionis therefore needed. Indeed, for centuries,different types of exposed structures con-structed with animal glues have successfully" weathered all storms " and passed the testof time.

With regard to Mr. Buttrey's point on thesubject of shrinking during drying, etc.

(referred to at length earlier in this article),unless special hardeners are used, if a Ain.thick layer of S.R. and hardener is cast andleft open to the atmosphere for a month ortwo it will first shrink slightly and thencompletely disintegrate into small cube -shaped pieces.

Scientific TestsIn conclusion, a few words should be said

on the methods employed in a modern animalglue factory to ensure that the finished pro-ducts cannot be infected by either mould orbacteria, and that their strength is uniformand consistent with the requirements ofwhatever purposes for which they are to beused.

Bacteria Test.-Samples from each batchof manufactured animal glue are stored fora specified time under laboratory conditionscreated to be most conducive to bacterialattack. In the event of such glue becom-ing infected it would be, of course, imme-diately rejected. Thus all glues which areissued from a modern animal glue factorycan be said to be proof against mould andbacteria infection.

Tensile Strength Test.-Modern animalglues are scientifically tested for strength inaccordance with B.S.I. specifications, and arenot released for sale unless they show a ten-sile strength of some predetermined figureconsiderably higher than the specificationminimum.

Limitation of space prevents me fromdealing at greater length with this subject,but the foregoing facts demonstrate thatmany of the observations made by Mr. But -trey in his article have been proved unten-able.

Finally, animal glues are very simple touse, and there is no better glue for mosttypes of woodwork. These adhesives havemeasured up to, and successfully withstood,the test of time.

Mathematics as a PastimeThe Proper Proportion

DO you play bridge ? When a pair ofplayers win two games, without theiropponents winning one, the pair get

a bonus of 700. Suppose now thatwhat they used to call " military exigency,"or some other annoying reason, causes theplay to stop when one game only has beenwon. How many points should be scoredfor this game ? And let us assume that thewinning pair is as likely as not to win thesecond game.

The chance of winning the second gameis I to I. But then, even if the pair losethe second game, all is not lost: a chanceof winning the third game remains. Whatis the value of this chance ? Of course, ifthe third game has to be played, the chanceof winning it is again I to I. But thenthere is an even chance that the game willnot be played. The value of that chanceis therefore I of I. The pair winning thefirst` game has i + or compared withThe 700 points should accordingly, if mathe-matics is to rule, be distributed 525 and 575,greatly different from the rule in practice.

Well, tackle this ancient problem: twoplayers agree that the first to score three

games takes the stakes of £3. A wins twogames and B one, when they are obliged tobreak off. How should the stakes be divided?

Put down the results possible of the fourthand fifth games. They are: (r) A winsfourth and wins fifth (2) A wins fourthand loses fifth ; (3) A loses fourth and winsfifth ; (4) A loses fourth and loses fifth. Inone only of these four results, the last ofthem, does B take the stakes. The divisionis accordingly 3 to I : A should take £2 5s.,B 15s. It is not £2 to £1.

Again, you see, the chances are I to I forthe fourth game, and to for the fifthgame.

What about this question of the loaves ?The hungry hunter met two shepherds, onehaving five small loaves, the other three,all alike. Equal division ensued, and thehunter paid 8 pennies for his share. Howshould the pennies be divided between theshepherds ? Not in the proportion of 5 to 3,but in the proportion of 7 to 1. For, con-sider : each eats a third of 8, that is 21; oneshepherd, therefore, gives up 21, the otheronly

September -October, 1950 NEWNES PRACTICAL MECHANICS 13

15th Article of a New Series

WHERE solid tools are used it is betterto use a steel of deep section. Rect-angular steel tools are more rigid.

The rectangular steels are obtainable in manysections in both carbon and high-speed.High-speed tools are the most advantageous.The cheapest way to use high-speed steel isin " tool -bit " form in a special holder, orto use " tipped tools."

Cutting and Clearance AnglesFig. 18 shows the cutting and clearance

angles. A tool cannot function correctly ifimproperly set. With a " rocker -bar " typetool -post the effect of rising or dipping thenose of the tool is to alter the front clear-ance and top -rake angles. If the base of thetool is rising towards the front, the frontclearance angle is decreased and the top -rake increased, and vice versa.

The tool shown in Fig. 18 is a right-handtool-it cuts towards the chuck. The frontclearance angle is the amount that the frontof the tool slopes out of perpendicular. Top -rake is the amount of back slope from thenose of the tool ; side -rake is the amountthat the cutting edge slopes away from thework. The tool is ground on both sides togive side clearance. For, soft mild steel thetop- and side -rakes may be at their greatest.Tougher material, like nickel and similaralloy steels, and cast -steel require less rake,because keen -edged tools will not stand upto them. The harder the material the morethe rake is reduced. Tools for hard brassare made flat-topped to. prevent digging ten-dencies ; with cast-iron the rake is reducedto provide a cutting edge that will with-stand the abrading action of the metal.

TopSide , rake

rake

Front clearanceFig. 18.-The various toolangles referred to in the text.

Y.cf.e9./m/ff

LATHE WORK (Continued)

Tool TypesThe group of tools shown in Figs. 19 to 22

may be made from the bar without priorforging. Their uses are as follow:-

From-roughing Tools.-Roughing out,turning or facing particularly suitable fortough material and cast-iron. Figs. 23 to 27show method of application to bar work,arrows show direction of feed for right- andleft-hand tools. For slender work the radius

RH.

Front roughingL H R.N. L.H.

Side roughing

Knife . Side finishing Brass turning

Figs. 23-27.-U s e s of front -roughing, side -roughing, knife, side -finishing, and brass -

turning tools. (See Figs. 19-22.)

at the nose should be made small ; requiresboth top- and side -rake.

Side -roughing Tools.-General turning ofa shouldered character when set at an angle,as shown in Fig. 24, or when set squarewith the work. The " swarf " comes awayover the tool clear of the work. Use witha deep cut and medium feed. The nose ofthe tool should form an angle of a fewdegrees less than 9o, the corner beingradiused. Requires both top- and side -rake.

Knife Tools.-Chiefly used for workingwith mild steel. Made so that when the

.1

RH L.H. R.H. L.H. . R.H L.H. R.H. LH. /PartingFront roughing Knife too/s 7- Brass

Side roughing ;Side finishing

Figs. I9-22.-Front-roughing, knife, brass, parting, side -roughing, and side -finishing tools.

Uk""

Fig. 29.-A special carrier for grippingtapered work.

cutting edge is presented square to the workthe front face has a back slope of 5 deg.(see Figs. 23 to 27). Deep cut, fine feed.Side -rake only.

Side -finishing Tools.-Like a knife tool,but has a small flat stoned on the frontsquare with the front face. This flat is setsquare with the direction of travel; itobliterates feed marks produced by pointedor round -nosed tools. Light cut, fine feed.Slight top- and side -rake. May have a widerface and top -rake only for use with coarsefeed. They then require very careful settingto be successfully used.

Brass Turning.-The small round -nosedtool is suitable for machining hard brass,gun-metal and the like. Used for roughingout and turning as in Figs. 23 to 27, andcan be fed in either direction. Flat-topped,no rake.

Outside and Inside Screw -cutting Tools.-Both made with top- and side -rake. Frontclearance of inside tool as for boring tools.Main cutting should be done on leadingflank of too? by feeding top slide alongslightly as well as increasing depth of cut.Allow both flanks to cut on last one or twocuts (see Fig. 28).

Boring Tools.-Boring tools are shown inFig. 28 below. The round -nosed tool(Fig. 28) is suitable for straight -throughholes, and has both top- and side -rake. Thecounterboring tool can be used for boringinto corners or flat bottoming ; has bothtop- and side -rake. The recessing tool issuitable for cutting oil channels in bushes orbearings, etc. Made with top -rake only.To prevent interference by rubbing, theclearance face should be reduced in depth tothat shown.

Parting Tool.-Make the blade of the toolwider at the cutting edge to prevent binding.Grind the rake by holding the tool verticallyagainst the face of the grinding wheel.

Outside screwcuttingBoring

Inside screwcutting CounterboringInside recessing

Fig. 28.-Screw-cutting and boring tools.

14 NEWNES PRACTICAL MECHANICS September -October, 1950

Fig. 3o.-One method of turning a flangedcylinder between centres. This method isoften adopted when carrying out turningoperations on finished work so as to avoid

chuck marks.

Jaw ChucksThese are purchaseable in sizes to suit the

centre height of the lathe. Additional tothese the turner is often compelled to makespecial fixtures for holding the work. Thework must be tightly locked, otherwise thework may be scrapped or fly out and causedamage.

Face -platesThe face -plates (see Fig. 36) have a number

of slots cut in them, and the work is held tothe face -plate by means of bolts and clamp-ing -plates passed through appropriate slots.Note that these slots are so arranged thatit is possible to clamp a casting of any shapeto it. For example, suppose it is requiredto bore a hole in a square casting, the holeto be out of the centre, the procedure wouldbe first to chalk over the surface of the cast-ing, to carefully mark out the position ofthe hole by means of the dividers, and thenloosely to attach the casting to the face -plateso that its position can be adjusted until thecircle scribed on the casting revolves trulywhen viewed in relation to the point of ascriber held in the tool -post and brought intoclose proximity. After finally locking thecasting down, the truth of the setting shouldagain be checked by this method.

The Angle -plateThe angle -plate is a right-angled casting

with slots in it similar to those in the face-plate, and the angle -plate is attached to theface -plate in a position suitable to the castingbeing operated on. For example, if it wererequired to bore the mouth of a crank -caseto receive a cylinder, the crank -case would bebolted to an angle -plate attached to the face-plate in this way. The angle -plate is alsouseful for boring or turning work at anangle ; it is only necessary suitably to packthe work to bore a hole to any required angleof casting,

The Independent Jaw ChuckThe independent four -jaw chuck (Fig. 34)

can similarly be used to hold work of_irregu-lar shape. It has the great advantage ofquick adjustment, for by means of a keyeach jaw can be moved independently andthe work " thrown over " until the settingis correct, according to the work to be done.

There are many other methods of chuck-ing work: sometimes it may be necessary tosolder the work to a round disc held in thechuck when the work itself is of such acharacter that it cannot be operated on inany other way, or it may be shellaced to apiece of metal or secured to a piece of wood.From this the reader will perceive that themethod used to hold the work is absolutelydependent on the work itself.

Fig. 31.-Various applications of the knife tool.The bent knife is used when the saddle can be

advanced to the work.

Tool Angles

BronzeCastIron Steel

WroughtIron Brass

(a) 5° 55° 20° 25° xe°(b) 3° 3° 3° 3° 3°(c) 3° 3° 3° 3° 3°(d) 85° 70° 6o° 56° 80°

I111101111I1(11111111

lemma

110,11111k' 11,1.11,111111

ill11111181181111111110

4111111115 WN

Fig. 32.-Various tool ,applications.

Turning ToolsThe first thing the amateur will discover

on attempting to turn is that the tool needsto be ground to a special angle according tothe material being turned, that it needsto be driven at a certain speed according tothe diameter and the material being torned,and also that tools of various shapes arenecessary to operate on particular shapes ofwork.

Roughing OutFor roughing out, a deep cut and a fairly

coarse feed are used, as shown in the topleft sketch of Fig 32 ; and for finishing, alight cut and slow feed is used, as in theright-hand sketch of the same figure. Asharp -pointed tool should never be used as,however fine the feed, it tends to cut ascrew -thread. For this reason tools of the

Fig. 36.-Various types of face -plate.

form shown in the lower sketch (Fig. 32)tend to give a smoother finish.

The cutting and clearance angles of toolsare shown by Fig. 35, which should be usedin conjunction with the small table shownabove. The use of the knife tool is clearlyindicated in Fig, 31.

(To be continued)

Fig. 34.-The four -jaw independent chuck.This is chiefly used for holding irregular -

Fig. 33.-Another method of turning cylindrical shaped pieces and for accurate centring of work.work between centres. It is not a self -centring chuck.

a

Fig. 35.-Tool angles (see Table).

September -October, 1950 NEWNES PRACTICAL MECHANICS 15

Britain 's Pro Tess in AzrcraAfterthoughts on the Royal Air Force Display, 1950

By THE MARQUIS OF DONEGALL

FRIDAY was the lucky day at the recentR.A.F. Display. Everything, I believe,went according to plan.

Saturday was only unlucky in the sensethat a cross -wind had blown up and there-fore I was denied the thrill of seeing Lt. -Commander J. K. Quill inducing the BleriotXI off the ground. However, Wing -Com-mander T. D. Calnan got the 1911 Deper-dussin off on its 25 h.p. engine, andSquadron -Leader G. Banner urged the 1912Blackburn to dizzy heights of 3o feet or so.

The Sopwith Pup, ace -fighter of that far-off war, even did aerobatics.

The other unlucky thing about the Satur-day display was that the nylon tow -ropebroke and thousands were denied the experi-ence of seeing a Dakota pick up a stationaryglider while travelling at some 13o m.p.h.

Since I first saw this feat. performed inFrance, shortly after D -Day, I have con-sidered it to be one of the most spectacularthings anyone could hope to witness.

The Canberra BomberSo we can now take the Saturday's pro-,

gramme. Except for the cross -wind, theweather could hardly have been better.

The English Electric Canberra bomberwith two Rolls-Royce Avon jet engines, per-formed aerobatics with the grace and neat-ness of a fighter. And. as the pilot came downflattening out from his dive, he was acrossthe four miles of the airfield almost beforeyou could locate him. This, at about 200 ft.over our heads.

One expects fighters to go very fast, andthe Meteor N.F. 1 r combined unbelievablespeed with the beauty of a bird. It is alovely sight to see these jet -fighters, includingthe de Havilland Venom and the newHawker 1081 streak across the airfield andthen go into a vertical climb until they dis-appear into the clouds at 2,000 feet. We hadindividual aerobatics by a de Havilland Vam-pire. This is the standard R.A.F. single -jetday -fighter. Its speed is 531 m.p.h. and itholds the world's altitude record of just on60,000 feet.

Many of you will remember the historicR.A.F. attack on the Prison at Amiens in1944. A reconstruction of the attack wasstaged in memory of Group -Captain Pickard,D.S.O., D.F.C., who led the attack, stayed

t

The de Havilland 112 in flight. This aircraft, named the Venom, and powered with ade Havilland ghost jet engine, is a single -seat fighter, and can be used as a fighter-bomber.

afterwards to see that the job had been doneand did not return. There were too French-men in the prison under sentence of death.Through the Resistance they made it knownthat they would rather take a chance if theR.A.F. would bomb the place. So accuratewas the bombing that most of the Frenchprisoners survived and most of the Gestapowere killed, as it was known that the Ger-mans lived in the right-hand end of thebuilding.

Just as they did on that occasion in realwar the R.A.F., at the Display, blew to piecesthe right-hand side of the reconstructedAmiens prison and left the rest intact. Itwas one of the most impressive demonstra-tions of accuracy that I have ever seen. Theyhad to have a whole -area, beyond the airfield,cleared of every living thing . just in casethey overshot the target. They didn't ...at 500 m.p.h.

Saturday's display started at 10.3o a.m.with Apprentices' and Cadets' Massed Bands.

Gliding DemonstrationThis was followed by the gliding demon-

stration by four of well over 2,000 A.T.C.Cadets who have recently qualified for their" A " gliding certificates. They were accom-

The English Electric " Canberra" jet bomber, powered by two Rolls-Royce " Avon" turbo -0engines, is the world's first jet bomber.

panied by their instructors in Slingsby Sedburgh sailplanes, sent off by motor -winchesand, after circling for a while, they landedin a very small space.

We then had the Sin. mortar demonstra-tion by the R.A.F. Regiment. An attackwas made on a prepared area of the flying -field which was covered with white powder.Doubtless the attackers achieved their objec-tive. They certainly raised an incredibleamount of dust in the process with the resultthat the success of their efforts was difficultaccurately to assess.

On Friday, the Cooper Trophy Race forthe zo Auxiliary Air Force Fighter squadronswas won by Flying -Officer Hazelwood of600 Squadron in a Meteor MK.4 at a paceof 511 m.p.h. The finish was so close thatno spectator could hope to decide the winner,and it seemed to take the handicappers sometime before they made up their minds.

On Saturday, this item was replaced byair drill performed by 12 Spitfires and 12Vampires, all of the Auxiliary.

Rehearsal for this type of item is particu-larly difficult for business and professionalmen. On this occasion various circumstances,including weather, made a complete rehearsalimpossible. Had I not been told this, Iwould certainly not have guessed it fromthe high standard of the formation flyingof the -Spitfires, integrated with that of theVampires.

Next, I saw the demonstration by the twoChipmunks which are used for training theVolunteer Reserve and the UniversitySquadrons. The aerobatics of Flight -Lieutenants Roxburgh and Gibbons werebeautifully synchronised as they met eachother from opposite ends of the flying area.

This Display ended with the two machinesflying towards each other going 'into a per-fectly timed spin and flattening out into lineto a perfect landing one behind the other.

Low Speed AerobaticsAs a contrast to the low speed aerobatics

of the Chipmunks (top speed 143 m.p.h.),we had individual aerobatics by Flying -Officer Nick Carter in a Vampire (top

'16 NEWNES PRACTICAL MECHANICS

In the foreground is another view of the de Havilland I 12 Venom, which is equipped with anengine 66 per cent. more powerful than the Vampire. Behind is the de Havilland Comet

four -jet air liner, the world's fastest commercial aircraft.

speed 531 m.p.h.): This machine was theVampire 5 which is a fighter-bomber asopposed to the Mark 3 which is a fighter.Flying -Officer Carter streaked across, put-ting the machine on its back over the centreof the flying ground, and then going intoa hesitation roll (8 point). He then didvarious other rolls which were performedvery quickly.

Then came the efforts of the veteranmachines already mentioned, followed by in-dividual aerobatics by a Meteor 4, perhapsthe most impressive feature being the amaz-ing vertical climbing power of the Meteor.

It is worth recalling that in 1946 a Meteor

established the world speed record up to thatdate of 66o m.p.h., and that the presentmodel climbs at a rate of 7,350 feet a minute.

Formation FlyingAs the afternoon wore on there was forma-

tion flying by Harvards-famous veterantrainer of the war days which is still inservice. These were led by Captain G. D.Stephenson, C.B.E., spelling out the lettersR.A.F. as the perfect formation, which Icounted as 35, swept over Farnborough. Itwas a most impressive sight.

The circus of three helicopters calledGertie, Gladys and Gussie, and their ring -

The Model Engineering ExhibitionBy W. J. B. L.

ITHINK the Twenty-fifth " ModelEngineer " Exhibition in London musthave been a surprise to many who had

been critical of some of the features intro-duced into recent exhibitions. Chief butt forcriticism was the working models arena,which took up so much space in the RoyalHorticultural Hall, as well as giving riseto a great deal of noise from time to time.In 1949 many enthusiastic visitors interestedin the competition models expressed regretthat so much of this section was displayedon shelves against the walls, where examina-tion of individual models was difficult. Thisyear all the competition models were on fourstands in the centre of the Hall, where theymade a most impressive exhibit all togetherand were in a good light for critical examina-tion by keen model -makers. The standardsof workmanship among both competition andloan models were very high indeed.Demonstration Area

In place of the working models arenathere was a Demonstration Area, wherevisitors could see demonstrations of model -making, on models actually under construc-tion. This feature proved most interestingand instructive. The passenger -carryinglocomotive track was at one side of the Hall,but this year the track was elevated five orsix feet above the ground, which the youngpassengers appeared to appreciate very much:in fact, they seemed to prefer it to the groundlevel track of previous years.

The new layout of the Exhibition Hallallowed for good space to be allotted to clubstands, which was much appreciated by clubstaking space. I was glad to see old friends

at the stand of the Society of Model andExperimental Engineers. When visiting theModel Railway Club stand I received a warmwelcome from the club's chairman, Mr.G. P. Keen, who showed me many of theexcellent exhibits provided by club members,incorporating some outstanding examples ofimprovements in standards of railway model-lers' work.D.S.I.R. Display

A most interesting addition to this year's

September -October, 1950

master in the proverbial pink coat and top -hat, caused much laughter, and has beendescribed in detail many times.

Apart from the attack on Amiens prison,already mentioned, we had individual aero-batics by a Spitfire 16. We had a mockattack by enemy bombers, the conversationbetween the defending Meteor leader and hispilots being broadcast over the loudspeakersystem. The most noticeable feature of thisdisplay was the apparent manoeuvrability ofthe normal-engined machines as opposed tothe jet-propelled type.

After formation aerobatics by a team ofVampire 5's, during which trails of red -white -and -blue smoke were very effective, we hada demonstration by new aircraft types. Mostimpressive to my mind, as mentioned before,was the English Electric Canberra. Othersincluded the Hawker to81 jet -fighter, theD.H. Venom fighter and the very gracefulMeteor NF. r I.

Mass Fly PastThe whole Display wound up with two

parts of a mass Fly Past. In the first partmachines seemed to arrive from every direc-tion including Sunderlands, Dakotas, Has-tings, American Super -Fortresses and-Lincolns, which flew above the others, toremind us of the night -bombing tactics ofthe war. The Royal Australian Air Forceand the Royal Canadian Air Force wererepresented, a Dakota of the Indian AirForce, and two of the New Zealand AirForce. The South African Air Force flewaircraft belonging to R.A.F. TransportCommand.

Few people have .seen every R.A.F. Dis-play since the first one in 192o, but havingseen about half of them I can definitely saythat this year's surpassed everything everattempted before.

exhibition was a display by the Departmentof Scientific Industrial Research. The modelsshown by this department came from threeof their stations: the National PhysicalLaboratory, the Fuel Research Station andChemical Research Laboratory. The shipdivision of N.P.L. displayed an example ofmodel ships used in the testing tanks: thesemodels are made in paraffin wax from thelines supplied by a ship designer. The Aero-dynamics Division of N.P.L. exhibited amodel wind tunnel with a compensated mea-suring mechanism which records the forceand moments of model aeroplanes in its airstream. The Fuel Research Station provideda model of a calorimeter building, which isused for domestic heating research.

An attractive exhibit was this 2i11. scale model of the Mogul type express loco entered byL. Billingham, of Haywards Heath. The small model is an 0-2-2 Rain/nil Rocket -type

loco entered by J. W. Powell, of Ashton Keynes.

September -October, 1950 NEWNES PRACTICAL MECHANICS

Producirz Hz:Ah VacuaWhat it is, How it is Obtained, and its Uses

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

(continued from page 385, August issue)

Pumps For High Vacua Needing A Fore -Vacuum.THE principle of this pump is founded upon

the Kinetic Theory of Gases, referredto previously. It will be remembered that themolecules of a gas strike the surroundingboundaries and rebound at random underforces due to thermal agitation. If one ofthese boundaries were to be given a motionof translation then the molecules strikingsuch a boundary would have imparted tothem a component of velocity equal to thevelocity of the said boundary. Referring tothe diagram of Fig. 12, there is shown inschematic form only the fundamentals ofthe Gaede Molecular Pump. A cylinder isarranged to rotate within a stator the clearancebetween the periphery of the cylinder and theinner wall of the stator being very smallexcept at that portion located between theinlet port m and the exhaust port n. Whenthe cylinder rotates inside the airtight statorgas is dragged from m to n and a pressuredifference is built up as shown by themanometer. Gaede has shown that at ordinarypressures the difference in pressure effectedby the pump is given by the relationship

Po6 nuL

(7)d2

where n is the viscosity of the gas, u thevelocity of the cylinder, L the length of theslot between m and n, and d the clearancebetween the cylinder and the stator betweenm and n. If, however, a fore -vacuum pumpis used in conjunction with this pump thelow pressure obtaining at m ensures that themean free path of the molecules is largecompared with the dimension " d " and. thenumber of molecular collisions becomesrelatively small as compared with the numberof collisions between the gas molecules andthe walls of the slot between m and n.Consequently the molecules are given motionby the rotating cylinder, but the relationshipat equation (7) is, however, no longer true.The pressure ratio now becomes constantand independent of the fore -vacuum pressureand dependent only on the speed of rotationof the cylinder. It follows that reductionof the fore -vacuum pressure below a certainvalue does not produce any increase inpumping performance.

The Diffusion Pumps or CondensationPumpsDiffusion or condensation pumps are

pistonless and employ as the working mediuma vapour into which the gas molecules passby diffusion and are then removed to a part

PuOoerTubing

FineClearance

Manometer

Cylinder

;Ns-Stator

of the pump where the vapour is condensedto be evaporated again in the boiler of thepump and re -circulated as a vapour to maintainthe evacuation process. The limiting factorfor the ultimate vacuum is the vapourpressure of the working medium at thetemperature at which it is condensed.According.to the working medium employed,so is the pump classified ; there are two maingroups, those using mercury as a workingmedium, and those using organic liquids oflow vapour pressure such as "ApiezonOils."

The Mercury Vapour PumpThe mercury vapour pump was pioneered

by Gaede' and Langmuir°. It consistsessentially of a boiler for the mercury whichsends a stream of mercury vapour up a centraltube to issue through one or a plurality of jets,the mercury vapour stream trapping the gasmolecules which diffuse into it from the vesselto be evacuated. It is general practice to

To HighVacuum

WaterJacket

To ForePump

Return Pipe ForCondensing Mercury

LaggingVapour

Water Out

Mercury VapourStream

MercuryBoiler

Electric Heater

Water In

Mercury Pool

Fig. 13.-Mercury vapour pump

exhaust the vessel to be evacuated by a fore -vacuum pump through the mercury vapourpump, the mercury being then boiled at thepressure produced by the said fore -pump.A condensation type mercury vapour diffusionpump is shown in Figs. 13 and 14, and thecomponents. are dearly designated, theoperation of the pump is exactly as described,and the water jacket ensures that the down-wardly directed stream of returning mercury

To Vacuum

Fig. 12 (Left).-Schematic diagram ofa Gaede molecular

pump.

Fig. 15.-Sectionaldiagram of a freezing

trap.

To Pump

LiquidAir

Lagged Vessel

17

Fig. 14.-Mercury diffusion pump, with maleand female flange -to -cone adaptors.

vapour is condensed and fed to the boiler.In early pumps of the diffusion type a carefulregulation of the mercury vapour temperaturewas necessary, but with the condensation typethe mercury vapour does not tend to enterthe upper parts of the pump provided theend of the jets are inside the water jacket.The maximum pumping speed is found tooccur when the pressure is such that themean free path approaches the dimensionsof the jet from which the mercury vapourissues.

Special devices known as freezing traps areoften used to ensure that no mercury vapourreaches the vessel, being evacuated. Atypical freezing trap is shown in Fig. 15,the freezing mixture being either solid carbondioxide mixed with ether, or liquid air.

It will be obvious to the reader that thelimiting factor deciding the ultimate vacuumto be attained is the vapour pressure of theworking liquid (mercury in this case) at thetemperature at which it is condensed. Thispoint has been referred to before and it isowing to this that new liquids have beenmade available having very low vapourpressures at room temperature. The mostimportant of these are termed " ApiezonProducts," Apiezon being from the Greekainesov meaning " without pressure."

Since mercury has a vapour pressure ofapprox. to-2mm. Hg. at room temperature itcannot achieve a better vacuum than its vapourpressure, unless, of course, a freezing trap isemployed, but this reduces the effective speedof pumping. The oil condensation diffusionpump, however, overcomes thesedisadvantages.

The Oil Diffusion PumpThis type of pump is similar in con-

struction to the mercury vapour pump, butthe working liquid is " Apiezon Oil " havinga vapour pressure of the order of to-7mm. Hg.at room temperature. This means that such apump may produce a vacuum of to -'mm. Hg.without any form of cold trap, and the pump-ing speed is kept at a high value.

A modern three -stage primary oil diffusionpump is shown in Fig. 16. It comprises aboiler for the oil heated by electrical means ;the oil vapour rises up the central pipe systemand issues from the jets. The distance fromthe wall of the pump to the jet is termed the" pumping radius," and since this is large forthe top jet, the compression ratio upon the gasIs low and the other jets have gradually

!4..-`'

18

decreasing pumping radii so that the com-preSsion ratio is gradually built up to permitthe evacuated gas to be efficiently handled bythe fore -pumps. It is important to prevent theoil from becoming overheated ; this may arisefrom too high a heat input or too low a volumeof cooling water in the coils. Also, it may beproduced by allowing the backing pressure tobecome too high. For this reason the heatersare not used above a backing pressure of0.3 mm. Hg. The two main requirements ofthe oil used are :

a. Low vapour pressure at room tempera-ture.

2. Sufficient thermo-stability.It will be noted that no lubricating action

is necessary.Four Apiezon oils specially developed for

pumps of the kind described are given inTable 3 below.*

Regarding Pumps in GeneralAll vacuum pumps are characterised by the

following three criteria :(a) The pressure it exhausts into.(b) The final vacuum it generates.(c) The speed of evacuation (i.e., pumping

speed) at any given pressure, that is thevolume or the mass of gas abstracted

let

Jet

Jet

From High Vacuum

PumpingRadius

CoolingCoil

Direction OfOil Vapour

to. EX/1OUSt

Oil Boiler

i---ElectricHeater

7:727 /// /7/7 /2/7/7/ /77/

Fig. 16.-Three-stage oil diffusion pump.

per unit time, measured at that pressure,from an enclosure containing gas at thesame mean pressure this is due toW. Gaede. It will be noted that thisdefinition very correctly gives the speedat a specific pressure, and does notattempt to give a general pump speedfor all pressures. The equation/ = dv

dtapplies here where f is the pumpingspeed, and it may be attained byplotting " v " against " t " and obtainingthe tangent of the slope of the curve.

Finally, it should be carefully noted that in

TABLE III

Product ApplicationApprox. Vapour

Pressure at RoomTemperature

Oil "A"Oil "B"Oil "C"*Oil "G"

Diffusion Pump

For iLge ind'ustrialhig vacuumpumps

'0-6 mm.Hgfo-7 mm.Hgso -8 mm.Hg

mm.Hg

t Specially developed by Metropolitan -Vickers tocompete with Dow Corning Silicone Oil 703.

* The data regarding Apiezon Products is givenby courtesy of Shell Chemicals, Ltd.

NEWNES PRACTICAL MECHANICS

most vacuum systems a network of pipingexists between the pump and the enclosurebeing exhausted, and this offers a resistanceto gaseous flow which is dependent upon aconductivity factor ; the rates of flow of gasesat the same temperature being proportional tothe square roots of their respective molecularweights when the connecting pipe dimensionsare kept the same. Further, the limitingvacuum within the enclosure may only bemaintained by continual pumping, should theenclosure be sealed off a pressure in excess ofthe limiting vacuum will be obtained °Wing tothe liberation of gas from the sealing, and thismay only be removed by getters.

Gauges for the Measurement of HighVacuaA great variety of gauges have been designed

for the measurement of high vacua, eachgauge operating upon changes in the physicalproperties of the gas as the pressure is changed,the only exception being the comparativemanometer gauge which is based uponBoyle's law. It is not possible to treat allthe novel and interesting gauges in turnas they provide a most detailed study ;readers who are more than casually interestedare referred to the bibliography under theheading " Pressure Gauges," where theleading articles upon this matter are recorded.

Three gauges in much use to -day areselected for consideration in detail :

(a) The McLeod Gauge.(b) Pirani Gauge.(c) Ionization Gauge.

The McLeod GaugeThe McLeod gauge operates upon Boyle's

well-known law. If a given volume of gas" V " at an unknown pressure " p " iscompressed to a smaller known volume" v ' and the pressure P observed, thenaccording to Boyle's law

P=PVA simple McLeod gauge is shown in Fig. 17.It consists of a bulb B to which is attacheda capillary tube " bb," and this is connectedto the low pressure to be measured at thepipe joint X, a mercury tube M and a mercury

From Vacuum From vacuum

r

L J

September -October, 1950

Fig. i8.-Rubberless andgauge.

enclosed McLeod

reservoir R is also connected to the bulb Bas shown. To overcome difficulties in readingthe gauge a comparison tube " cc" is pro-vided, the bore of this tube being identicalwith the bore of the capillary " bb.'

To operate the gauge the mercury reservoirR is raised, thereby forcing the mercurycolumn up the tube M past the joint X andthus trapping gas in the bulb B. Furthercompression of the gas in B is effected byraising the reservoir R still higher untilfinally the mercury in the capillary " cc "is level with the upper end of the capillary" bb." The pressure of the gas in bb 'is then equal to the height of the mercurycolumn " h," this is more readily seen fromthe enlarged view of the gauge shown inthe circle of the diagram.

If the cross-sectional area of the capillaryis " a " and the height of the mercury column" h "mm., then :

h x ah ah=

p= V - VAlthough the McLeod gauge is constructed

in many forms, the glass -steel McLeod gauge

Fig. 17 (Left).-Diagram of aMcLeod gauge andenlarged detail of

upper end.

Fig. 19 (Right).-Diagram of

Pirani gauge.

To Measuring'Bridge

ToVacuum

LongTungstenFilament

September -October, 1950

manufactured by W. Edwards and Co. isone of the finest for precision work and itsrobust construction overcomes the difficultiesoccasioned by long rubber connectionsbetween the reservoir and the bulb. Thisvery fine gauge is shown in Fig. 18 and itis seen to comprise a steel mercury reservoircapable of vertical movement connected bystainless steel tubing to the glass capillarysystem.

The Pirani GaugeThe Pirani gauge operates upon the

phenomenon of gaseous thermal conductivity.It is well known that in a gas at normalpressure the coefficient of thermal conduc-tivity is independent of pressure ; when thepressure is greatly reduced, however, thematter is quite different.

In the description of the Kinetic Theoryof Gases it was shown that if the gas pressurewas reduced to such a low pressure that themean free path of the molecules is largecompared with the dimensions of the evacu-ated enclosure, then many of the gas moleculescollide with the walls of evacuated enclosurewithout any intermediate collisions withother gas molecules.

If an evacuated enclosure is providedwith a hot filament the heat conductiontherefrom may take place directly from thefilament to the walls, provided the pressureis of the low order discussed above. It is

FromVacuum

GaugeFilament

9256 11

CompensatingFilament

10,000 fl

Ce//s

Ldi

Fig. 20.-Bridge system for the Pirani gauge.

the variation of thermal conductivity of thegas at low pressure with variations in thatlow pressure that enable measurements tobe made.

Although Pirani" invented the mostsuccessful gauge of his time, Hale 12 perfectedthe original design and the gauge is usuallytermed a Pirani-Hale gauge in recognitionof the work of each investigator.

Hale's improved Pirani gauge is shown inFig. 19, the current in the filament beingmaintained constant, while the change involtage drop is observed as a function ofpressure.

The complete gauge utilises a WheatstoneBridge network, Fig. 20, to measure thechange in resistance. One limb of the net-work contains the gauge filament coupled tothe vacuum system while in another isinserted a compensating filament. The othertwo limbs of the network comprise a 925.6Qmanganin wire R, and a Dekadenstopfelresistance of 1o,000f2, R2. The milliammeterM, records the constant current which is somaintained by the variable resistor R,.Readings are taken from R1 which is adjustedto keep the galvanometer reading zero andthus the network balanced.

Various developments and improvementshave resulted in gauges of this type whichhave a high sensitivity and are easily read-able ; the modern version of the Piranigauge is shown in Fig. 21, these instrumentslend themselves to bench or panel mounting

NEWNES PRACTICAL MECHANICS 19

Fig. 21.-Pirani gauges.

and alternative forms of the gauge head areclearly visible.

The Ionization GaugeWhen an electron stream is caused to pass

through a gas at low pressure from a heatedfilament to an anode structure ionizationof the gas molecules occurs, whereby someof the electrons are removed from the neutralatoms of the gas producing H- ions which maybe collected on a grid or third electrode havinga negative potential. There is a certainminimum velocity of the electron stream forionization to occur and this is given by therelationship :-

mu' = Vewhere " m " is the mass of the electron ;" u " the electron velocity ; " V " the voltagerequired to produce the velocity " u " ; and" e " the charge on the electron.

It will be understood that the amount ofionization increases with the pressure for afixed value of electric current, and this pro-vides a qualitative guide for the measurementof low gas pressures.

Yarwood 13 suggests that an ordinary triodevalve such as the LS5 may be used as anionization gauge but it is more satisfactoryto use a gauge having a specially designedelectrode system.

A circuit diagram for such a gauge employ-ing what is termed the inner collector arrange-ment, that is to say a negative grid forcollecting the + ions, is shown in Fig. 22.

Milliammeter

NMI

Vacuum

Anooe

(,rid

FllamAt

'I'HFig. 22.-Diagram of an ionization gauge.

Many workers and investigators haveadvanced the design and accuracy of theionization gauge, and a selection of the paperson this subject appear in the Bibliography.

ConclusionIn conclusion it is desired to acknowledge

the many sources of information used in asurvey of this nature, and it is thought thatthis has been taken care of in the extensivereferences quoted ; in particular the writerwishes to thank Messrs. W. Edwards & Co.,Lower Sydenham, London, for the finephotographs so readily supplied and usedto illustrate the subject matter of the article.

Bibliography1. Jnanananda : High Vacua. D. Van

Nostrand, Co., 1947.a. I. Langmuir: G. E. Review, 1920, p. 5o3

Phys. Review, 2, 450, 19133. Child : Phys. Review, 32, 492, 5911.4. Dushman, Dr. Saul : G. E. Review, June, 1920,

P. 496.5. 0. E. Meyer: Kinetic Theory of Gases,

1899.6. Sutherland : Phif Mag., 36, 507, 1893.7. Encyclopmdia Britannica.8. Gaede : Phys. Zeit, 13, 864-70, 1912.9. Gaede,:

xo. Langmuir :t. Pirani:

12. Hale :

13. Yarwood, J.:

Pressure GaugesType :Radiometer :

Ann. d. Phys., 46, 357-392,1915.

Phys. Rev. 8, 48-51, 1916.Verh. d. deut. Phys. Ges.

24, 684-94, 1906.Trans. Am. Electrochem.

Soc. 20, 243-5E, 1911.High Vacuum Technique,

p. 26.

M. Knudsen, Ann. d. Phys.,32, 809, 1910.

Molecular: I. Langmuir, Phys. Review,1. 337, 1913.

Dushman, Phys. Review, 5,212, 1915.

Pirani-Hale: Campbell, Proc. Phys. Soc.,1921.

Penning, Philips Tec. Review,July, 1937.

Ionization: Dushman and Found, Phys.Rev., 17, 7-19, 1921.23, 734, 1924.

Buckley, Proc. Nat. Acad.Sci., 2, 683, 1916.

Misarnichi So. Proc. Phys.Math. Soc. Japan, r, 76,1919.

Viscosity Langmuir, jour. Amer. Chem.Soc., 35, 107, 1913.

Thermal and Ionization : Instrumentation, Yoh 2, No. 3.Sept. -Oct., 1946, p. 14.

FOURTH EDITION.

REFRESHER COURSE4 IN

MATHEMATICSBy F. J. CAMM8/6, by post 9/-

20 NEWNES PRACTICAL, MECHANICS

Electric Gas LighterSIR,-With reference to a

letter in a recent issueconcerning an electric gas -lighter, about six years ago Imade a gaslighter similarto the one which P. V.Buckley describes, with the addition of a micro -switch in the primary of the transformer, and a24 -volt pilot lamp in the secondary. The switchis operated by a lever (similar to the hook leveron wall telephones), and the ignition pencil wasmade from a piece of 5/ 16in. brass rod drilled inone end, a few strands spring steel wire beingfixed in the hole. I have found that steel wiregives the surest ignition. I also fastened awooden file handle to the other, end of thebrass rod, with an eyelet screwed into thehandle for hanging on to the lever. Thereason for using brass rod was to give thenecessary weight to actuate the micro -switch.The function of the pilot light was to givewarning in the event of a power failure.

The switch was taken from surplus disposalequipment, /rid the switch assembly, switchlever and pilot light were all mounted in asmall wooden box about 4in. x 4in. x tin. Thetransformer in this instance was installedunder the house, and the box containing theswitch assembly is screwed to the wall adjacentto the gas stove. I am not enclosing a diagramof the switch assembly, as all sizes would varyaccording to the material on hand.

My reason for making the switch is thatthe ignition pencil must be placed in a positionwhere it cannot short-circuit, and as hangingsolves that problem, it is easy to hang it sothat it switches off the power to the trans-former.

I may mention I have been a constant readerof your magazine for many years and lookforward to it each month.-H. P. J. WHITLEY(Launceston, Tasmania).

A Mathematical PuzzleSIR,-In the July issue of PRACTICAL

MECHANICS, Mr. A. Delfont asks for anexplanation of the following :

7 7x 7=6, - -F 7

The essential problem is to find two quantitieswhose product equals their sum :

Put mn = m nThen mn -m= n

m(n-I)= nm = n

n -ISubstitute this value of m in the originalequation :

n nx n= +nn- I n -1This is the formula you gave ; and a similarformula for more than two quantities can beas easily drafted :

x P - SPSI P -where P and S are the product and sumrespectively of any number of given quantities.

If P=2x3x4x5=x2oThen S=2+3+4+5= 14And X2 X 3 x4 X5I

14= +2+3+4+5119

The latter formula brings out the truerelationship between the quantities. Thisrelationship is disguised in the formula fortwo quantities where p = s =n.

A particular case, included in the abovegeneral formula and which may be of interestto readers, is when we take x quantities each

equal to x x-1

1(x -x -1)x = x x-1 = x.x x-1Therefore : 2 X 2 =2 + 2

1 1 1 1 1 13 2 x 3 2 x 3 2 = 3 2 + 3 2 + 3 2

1 1 1 1 1 1 1 1

43x43x43X43=4.+43+4.+43-A. B. THOMAS (Manchester).

etc.

SIR,-Reader A. Delfont's " puzzle " is justone of those mathematical problems

which can be explained most easily by algebraas follows :

Take the general formula.(proved by numerical

n -IIf n x n= n + n

n-1 substitution).

then n' n+n(n-r)(n -r) n -r

and n2---n[t +(n-i)](Evaluating the square bracketr+n-r=n) A.C.Therefore n2 =n x mains

-E. B. DEW (Milton).

Fire -alarm SystemSIR,-With reference to a recent query by

your reader P. C. Campbell, of Stone -haven. Having had experience with variousalarm circuits myself, I was interested in thefire -alarm circuit which was published inanswer to the query.

May I suggest that by very little alterationthis circuit could be greatly improved thus :

KlaxonHorns

Indicators

I

SinglePole

Push Buttons

Bel/Contact

Relay

Diagram of a modified fire -alarm system.

September -October, 1950

By using an additional pair of contacts onthe relay, and a single -pole switch mountedin a central position, the system will continueto operate for an indefinite period withoutconstant pressure having to be maintainedon any of the push buttons. Merely to pressany one of the buttons once only will besufficient to set the system in continuousoperation.

Connecting the switch to battery and throughthe additional contacts to one side of the relaycoil, as shown in the accompanying diagram,is all that is necessary to carry out thismodification.-F. SLATER (Spalding).

" The Automatic Doctor "SIR,-I read with deep interest the article

in the July issue of PRACTICAL MECHANICSon " The Automatic Doctor," by A. M. L.

I should like to state that there is such aninstrument in existence. This instrument notonly diagnoses the disease, it will also revealhow much medicine to take to correct thedisease. My explanation is very vague, but Ican supply further information if required.May I state that the instrument is workedon the electronic reaction of the humanbody. It is a well-known fact that all diseaseshave a vibration of their own, but how todiagnose disease is not known to the medicalprofession fully. This instrument certainlydoes give correct results.

May I state that I am speaking from actualexperience of having been tested by thisinstrument and was given a correct diagnosis,when doctors had failed. Now it is agreed bythe medical profession that I do suffer fromwhat the instrument found out.

In conclusion I quite agree with A. M. L.that the " strongest trade union in the world "would oppose anything they don't like, regard-less of how much good it will do.-R. G.SALMON (Salford).

Ex -Aircraft Motor GeneratorsSIR,-After experimenting with ex -aircraft

motor generators (type 29) I find that

Diagram showing position of suppressor for anex -aircraft generator.

best results are obtained by connecting up asfollows :

Connect H.T. armature and the field inparallel ; the L.T. brush gear must be movedround 90 deg. and shorted out with a piece of18 s.w.g. wire.

The starting torque is quite good andthe power is about 1/6 h.p. ; the motor canbe run without overheating for about threehours. A condenser can be connected acrossthe H.T. brushes to act as a suppressor, asindicated in the diagram.

This machine has run a tin. compoundlathe with good results.-E. PRIESTLEY(Bradford).

read with interest the letter from" Mr. Andrew (Barnsley), in the Julyissue :

May I be allowed to point out that arepulsion induction motor does not performas a series motor. A R.I. motor runs as asingle-phase machine. Starting as a repulsionmotor it subsequently is changed to a more orless squirrel cage motor having a short-circuited rotor ; this is accomplished byshorting the commutator bars of the arma-ture.

A plain repulsion motor would perform asa series motor, its speed varying with the

September -October, 1950 NEWNES PRACTICAL MECHANICS 21

load; the repulsion and R.I. motors aredifferent in their set-up and performance.

A rotary would not be started in the mannersuggested by your correspondent, the correctprocedure would be to run it up on D.C.,synchronise it to the supply and then connectit. The matter of insulated laminations doesnot really come in because these laminationsusually carry an oxide in some form on oneside of the stampings. It is not the practiceto -day to insulate stampings with tissue paperas in the old days.-J. W. COOPER (Enfield).

cIR,-It may interest your correspondents to" know that I am successfully using atype 31 generator to drive my bench lathe.Fortunately I have a heavy duty mains trans-former, giving an output of 12 volts and about'3o amps. max. I therefore removed the brushesfrom the output commutators and wiredarmature (input commutator) and field inseries (ignoring the shunt tapping). Themotor runs quite cool-even after 3o minutesunder load, and the casing is only warm to thetouch. The speed is high-about 5,000 r.p.m.-but a ro : 1 reduction to the countershaftgives a useful spindle speed which does notalter much under varying loads. Incidentallythe D.C. input is rated as x8 volts 12 amps,but I find,that at 12 volts A.C. the current atstarting is about 15 amps.

This seems the only way to get real powerfrom these machines, but if one has to buya suitable transformer it would probably be

cheaper to invest in a suitable induction motorat the start. These remarks may be helpfulhowever to those who have a transformer, orcan build one.-H. D. RArrEmtuav (Chep-stow).

Automatic Gear Changingread with very much interest. the

article in PRACTICAL MECHANICS entitled" Power Transmission Methods," dealingwith variable gears, in which it was statedvarious attempts had been made to auto-matically adjust the gear ratio under varyingconditions.

While I was in the Army I came across someCadillac carriers, where all one had to do wasto press on the throttle and it would changegears automatically according to the roadconditions. If you removed your footaltogether it would drop directly into neutral.We had these vehicles about nine months,and no maintenance was needed. I am notquite sure, but I believe the system wasreferred to as an hydromatic gearbox.-C. ASPEY (Wigan).

Trisecting an AnglesIR,-With reference to Mr. W. Duncan

Needham's letter on " Trisecting anAngle," I would like to point out that hisconstruction is definitely not accurate. Itcan easily be proved that :Cotangent CAM-Cotangent + CAD+

cotangent J CAD and that this relationshipis not the same thing as :

CAM=1 CAD.I give below a table showing the error in

Mr. Needham's construction.AngleCAD Angle CAM Error

I0° 3° 20' 1.70 1.7°20° 6° 40' 14" 14030° IO° 0' 460 46040° 13° 21'49' I' 50"50° 16° 43' 35" 3' 35060° 20° 6' le 6' 14"70° 23° 30' I" 10' I"8o° 26°55' 3" 15' 30go° 30° 21' 4r" 21' 41'

100° 33° 70 70Ho° 37° 20' 340 40' 340r2o' 40° 53' 36' 53' 36"130° 44°31'20" 1011'20"140° 48° 8' 16' I° 28' 16'150° 51°50'50" I° 50' 50016o° 55'37'35" 2° 17'35'170° 59° 29' 6' 2° 49' 6"18o° 63° 26' 6" 3° 26' 6"

-M. DAVIS (Bexhill -on -Sea).

Circular RainbowIR,-On June 4th I was on Ferring beach

when I observed that the sun wassurrounded by a circular rainbow, starting atabout 3o deg. It lasted from 3.3o p.m. till4.15 p.m. when it promptly disappeared.

Others on the beach witnessed the incident.-R. LAW (Ferring-on-Sea).

Staines and District Society of ModelEngineers and CraftsmenTHE above society held their annual

exhibition at the Staines Town Hall, onSeptember 15th and 16th. As usual therewere four classes in open competition, locomo-tives, boats, aircraft, and general. An addedclass this year was the club contest consistingof three nominated models from one club.Loan models were also greatly appreciated.Lone hands desiring information concerningthe club should contact R. F. SLADE,Hon. Secretary, 166, Kingston Road, Staines.

Morley and District Model Aircraft ClubTHE above club continues to be successful,

and is now holding outdoor meetingsamongst members every Thursday eveningand Sunday mornings. This will enableus to build up club funds to a satisfactorylevel.

The club is now 5o members strong, andall are looking forward to the exhibition tobe held on September 16th. It is intendedto make it a club contest, and also an openone.

Our club president, R. Crewdson, haspromised us a cup and £ ro in prizes. Thelocal flying club have donated three free tripsin aircraft. The R.A.F.A. a prize yet to bestated. Messrs. Coles and West not lessthan three guineas value in kits. Competi-tors this year should not be disappointed inany way. Also the club intend to give con-trol -line flying exhibitions every eveningduring the Battle of Britain Week. Thiswill take place in the recreation ground ina completely fenced -in enclosure, with thespectators on the outside. The local councilhave already unofficially agreed, and we arenow awaiting their confirmation. Our first

exhibition was successful ; in fact, publicinterest was higher than was anticipated.-B. H. WORTHY, Hon. Sec., c/o Mrs. C.Riches, Council Houses, Sutton, Norwich,Norfolk.

Ilford and West Essex Model RailwayClubAVERY enjoyable meeting was held on

July 5th when Messrs. Theobald,Skinner and Pearce, footplate inspector, fire-man and guard respectively, from the EasternRegion (B.R.) gave talks on their duties andexperiences over long periods of service onthe railways. The talks and replies to ques-tions which followed were presented inhumorous style and proved not only veryinstructive but equally entertaining.

The best thanks of the meeting wereextended to the three speakers and the hopewas expressed that the club might again havethe privilege of their company at a futuremeeting.-E. W. CORNELL, Hon. Secretary.42, Lincoln Road, Forest Gate, E.7.

Books ReceivedQuestions and Answers on A.C. Machines

and Equipment. By E. Molloy. Pub-lished by George Newnes, Ltd., i34pages. Price 5/- net.

IN this handy little book, in convenientform for immediate reference, will be

found the answers to most of the questionswhich are likely to arise in connection withthe installation, operation and maintenanceof A.C. machines and equipment. Thefirst part of the book deals with questions andanswers concerning elementary principles ofall the main types of A.C. machines and

equipment and their application to particularelectrical equipment. The second part ofthe book gives detailed explanations concerningPower Generation and Measurement, Trans-formers, Rectifiers and Convertors, Lighting,Motors and Control Gear, and A.C. Heatingand Welding Equipment. The book,is profusely illustrated with line diagrams,should prove invaluable to practical menand students who require concise answers tothe many questions which arise in theireveryday work and studies.

Manual of the Miniature Camera. Editedby T. L. J. Bentley, D.I.C., A.R.C.S.,B.Sc., A.R.C.S. Price, I2S 6d. 256 pages.Published by George Newnes, Ltd.,Tower House, Southampton Street,W.C.2.

THIS important book covers almost everyangle of miniature camera work and in

this, the third edition, a comprehensive revi-sion has been made, to include details of thelatest types of cameras, enlargers and acces-sories, and to generally bring the work com-pletely into line with present-day practice.

Separate chapters are devoted to exposure,negative film processing, and projectionprinting, with particular reference to thenewest products and recent developments inminiature photography. Techniques such asWild Bird, Travel, Action, Press and Colourphotography are also dealt with in articlescontributed by experts in these fields.

Workshop CalculationsTables and Formuke

Ninth Edition

by F. J. CAMMFrom all booksellers, 6/- net,by post 6/6 from the publisher,

GEORGE NEWNES, LTD.(Book Dept.),

Tower House, Southampton Street,W.C.z.

22 NEWNES PRACTICAL MECHANICS September -October, 1950

Fig. 1.-The telescope pointing south.

FROM time to time there appears in thepages of this and other journals illus-trations of astronomical telescopes

constructed by amateur instrument makersfor their own use. In many cases there isevidence of good design and workmanship,but the builders appear to have no object,as the outcome of their labours, beyondvisual observation.

It is, of course, a delightful thing to beable to see, by optical means, what cannever be observed by the unaided eye. Butthere are limits to what it is possible for theeye to see, and, moreover, as the result ofprolonged observation, the eye becomesfatigued and so sees less and less. Thenagain we cannot always be quite sure ofwhat we have seen, or thought we saw, fordifferent observers of a celestial phenomenonwill sometimes make widely differing reports.

The only satisfactory way in which to seeand at the same time record an astronomicalcondition or happening, is to do so throughthe medium of a photographic plate. Lookthrough the telescope first by all means andthen -change the eyepiece for a camera attach-ment and expose a plate or film.

It was the realisation of the limits to whichvisual observation can be carried which ledme, many years ago, to build an instrumentwhich I thought would enable me to takephotographs. It was. a refractor, with a4in. object glass by a good maker, equatoti-ally mounted and clock driven. For visualwork it was excellent, but photographicallywas very disappointing, and the reason wasthis: that the ordinary achromatic objective,though sufficiently free from colour-chrom-atic aberration-for visual observation isnot sufficiently so for photography ; inother words, it is not corrected for the wholeof the spectrum. I found that although suchfully corrected objectives were made-theyare known as " photo -visual objectives "-the cost was prohibitive and that it wouldbe cheaper to scrap a part of my work,abandon the refractor and make a reflector.I sold the object glass, discarded the tele-scope barrel, retaining the equatorial head,

photographicWith Notes on the Construction of a 61in.

the clock, the breech piece which takeseither the eyepiece draw tube or the plate -holder, the finder and the following telescope,counterpoise and all other fittings. ThenI bought a 61in. parabolic mirror anddiagonal flat mirror and built a new barrel.The result is shown in the illustrations,Figs. I, 2 and 3.

Mirror is AchromaticI do not know whether all of those readers

who have built reflecting telescopes areaware of the fact that the mirror of thereflector is absolutely achromatic and has,when newly silvered, greater light -collectingpower than the refractor.

These facts make the reflector the moresuitable and, incidentally, the cheaper formof instrument for astro-photographic work.But, since some exposures will run into hoursof duration-on faint star groups andnebulae-the telescope must be driven by a

, clock or power motor to keep sidereal time.That is to say, the telescope must be rotatedabout the polar axis at such a rate as willkeep the heavenly object always in exactlythe same position on the plate during thewhole of the exposure without any variation.

Since, however, no clock or piece ofmechanism was ever made with sufficientaccuracy to accomplish this, without somemeans of control and correction, a gear isintroduced in the clock which, operatedeither electrically or by hand, enables themovement of the telescope to be either re-tarded or accelerated as may be required.Apart from possible inaccuracy in the cuttingof the gears in the clock and those of theclock drive, there are other factors whichprevent perfect uniformity -of motion, suchas friction in bearings and other rubbingparts and lack of perfect balance in the tele-scope itself, its counterpoises and fittings.

I have said that the telescope must keepsidereal time, but if the moon is to be photo-graphed this statement will not apply ; themoon has, of course, a retrograde movementacross the heavens and so provision must bemade in the clock for altering the speed fromsidereal to lunar rate. The means wherebythis can be done will be referred to later. Inthe meantime, I will answer the obviousquestion which will occur to the reader:how are we to know during a long photo-graphic exposure whether the clock is gainingor losing ? Well, it is done by means of afollowing telescope, a refractor having anobject glass of about one-third of the aper-ture of the main mirror. The follower isclearly seen in Figs. 1, 2 and 3 ; the O.G.is 2,kin. diameter.

Follower With Spider WebsThis smaller telescope is used like a gun -

sight and, like a theodolite, is provided withcrossed spider webs in the eyepiece. Inphotographing the moon or portion of theterminator, when the moon is not full, aparticular .part of a lunar crater is kept deadon the point of intersection of the webs,these being visible as crossed black lines,but when faint objects such as star groupsare being photographed the webs are in-visible against the dark background of thesky and so they must be rendered visible inone of two ways: both by electric illumin-ation. One of these methods is the " brightfield," and the other " bright webs." Theformer is much simpler to make and fitbecause eyepieces are not interfered withand different powers can be applied-pro-

vided they are all fitted with webs-withoutaffecting the illumination, whereas withbright webs, that is to say, a dark field, thewebs have to be illuminated by an obliquebeam of light from a lamp on the side ofeach eyepiece. The bright lines are inclinedto be somewhat dazzling unless some meansare adopted to dim the lamp. With thebright field dimming must be resorted toand it is an advantage to be able to get threeor four degrees of brilliancy. The reflectorshown in the illustrations is fitted withbright field illumination and the lampholderwhich also carries a tiny mirror is seen inFig. i near the upper end of the follower.In Fig. 2 may be seen, on the main telescopebarrel, a resistance coil, a rheostat switchand a terminal block.

Fig. 4 is a diagram of the electrical con-nections and this shows a small three -cellbattery, also mounted on the telescope. Inmy own instrument the battery was separ-ated from the telescope and was connectedto a pair of terminals, near the rheostat, bya long flex, which flex was a nuisance, andI therefore recommend the battery on thebarrel. In this' diagram the tiny mirror isshown as being cut from a small piece of tinplate. If polished with plate powder orrouge it serves the purpose admirably ofthrowing a glow of light into the telescopesufficiently luminous to show the webs asdark lines and yet not too bright to dimthe star chosen as the target.

Fig. 2.-The telescope pointing north-east.

September -October, 1950 NEWNES PRACTICAL MECHANICS 23

Reflector TelescopesReflector

The Driying ClockNow I come to what is perhaps my main

purpose in writing this article ; to give someparticulars of a driving clock which shallbe suitable for any reflecting telescope offrom six inches to eight inches aperture.Although a clock cannot, within reason, betoo large for a telescope it can, verydefinitely, be too small. Both the clock andthe whole equatorial head shown in Figs, I,2 and 3 are just a little on the small sidefor a 61in. reflector. They were originallymade for the 4in. refractor, and the re-flector is the heavier of the two, quite 5o percent. heavier.

So, in preparing the accompanying draw-ings of a driving clock I have kept this pointin mind and made all gears, spindles andbearings larger than my own and largeenough for such an instrument as the eight -inch telescope for which I give a drawing inFig. 5. Most of the details of the construc-tion of the clock will be obvious from theaccompanying drawings Figs. 7 and 8, but thesubject of Fig. 6 first claims attention. Thisis the important part of the drive at theequatorial head. Of the head itself PF isthe polar axis frame with conical bearings,

By E. W. TWINING

PA the polar axis, DF the declination frameor crosshead, into which the polar axis isscrewed and pinned, DA the declination axis.CC are clamps and the gunmetal plate whichcarries these is attached to DF through themedium of a socket attached to the plate bythree screws. Into this socket fits a steelpin DP which is screwed into DF. Thissocket and pin drives and rotates the polaraxis, and with it the telescope, when theclamps are closed on to a flange on the tan-gent wheel TW in the teeth, on the peri-phery of which the screw TS engages.

Turning now to calculations relating togear ratios, revolution speeds and other par-ticulars of the -clock we will commence atthe tangent wheel: this for convenience Ihave divided into 36o degrees and 36o teeth.The screw TS which engages with it isgin. diameter and is screw -cut 14 threadsper inch ; therefore:

36o

14-25.7I43in. circumference or

3.=8.185in. diameter.

Now 36o represents 24 hours or 24 x 6o-1440 minutes.

I440 =4 minutes per tooth and 4 minutes360

per revolution of tangent screw.From this it will be seen that as the gear

ratios at the end of the tangent screw, Fig. 6,and at the lower end of the long driving rodB2, Fig. 7, are both r to r, the shaft Br willmake one -quarter revolution per minute.

An Epicyclic GearBetween shafts Br and B there is a drum

containing differential, or epicyclic gearing,consisting of four gear wheels marked b, br,b2 and b3. It is by the slow rotation ofthis drum by hand and by pulling on thecord in one or other direction that the move-ment of the telescope is either retarded oraccelerated without affecting the speed of theclock.

As the ratio between b3 (on shaft Br) andb2 is I ,to 2 and between br and b2, I to 2,

the shaft and wheels Bwill make r.p.m.

The rest of theratios and revolutionspeeds in the clockare :

Fig. 5.-An 8in. reflecting equatorial telescope.

3 CELLBATTERY

Fig. 3.-The telescope pointing north, laidover the Polar Axis.

Shaft R.P.M. Ratio

Drum 11A - ii 4B i

C 4}4

41D aE 90

5

RHEOSTAT 0\

ERMINALS

Shaft R.P.M. Gr.Ratio

B x 4Bi 11 x

Bz .1

T. x

Screw il

The shaft F is fixed, held by ratchet It;and a, on a spindle attached to the drum,revolves around f, thus driving wheel A. Fis only revolved-turning by means of ahandle fitting on the squared end-for wind-ing the clock. Through a the drive to A isstill maintained even whilst rewinding thecable upon the drum.

The drum is made in three parts,machined all over, and the barrel screw -cut,with a spiral groove on the outside to takethe stranded steel wire cable. The end

PRESSSWITCH.

MAIMTELESCOPeBARREL

.

FOLLOWINGTELESCOPe

Fig. 4.-B4ht field illumination of follower.

r

24 NEWNES PRACTICAL MECHANICS

pulling screws are arrangedin pairs, at equidistantpoints circumferentially,means are thereby providedfor so adjusting the ringthat its lower surface isexactly parallel with theplane of rotation of thegovernor balls and withthem the two leathers inthe cups.

But there is more thanjust a matter of parallelismrequired to secure correcttime adjustment. The ringmust be sufficiently low toensure that the leathers are

wiPssigt1/4%,'WV\N 11*VAV4441eel67

ar

PF

cheeks can be sweated into the barrel withsoft solder. Anchorage for the cable isprovided by a hole drilled through the barreland flange of the cheek at the rachet end;the cable is passed through this, the wiresopened out, bunched up and made into aknob with solder. There should be twenty-one turns in the spiral groove, so that, asthe drum revolves at the rate of 8 minutesper revolution, the length of run of theclock, without rewinding, will be: 8 x= 168 minutes, or approximately two andthree-quarter hours. This would be longenough for many photographic exposures.

Clock Speed ControlThe first of the two revolution tables

shows that the speed of spindle E isgo revolutions per minute. With thespindle the two " fly -balls " or governorweights turn and the principle of the con-trolling action is: that these balls fly out-wards by centrifugal action. The balls areeach threaded on a screwed arm tapped intothe lower arm of a bell crank, pivoted ona casting pinned on E. The outer ends ofthe upper arm are formed into cups bysinking with a quarter -inch drill. Into thesecups leather punchings are inserted-cutfrom very thick shoe -sole leather-theyshould be cemented in and then oiled.Mounted above the governor is a heavy castgunmetal ring, carried by screws from thetop gunmetal plate, which, in turn, is sup-ported by four stout brackets rising up fromthe clock case.

The screws carrying the ring should havea fine thread such as No. o or No. z B.A.There are three screws tapped into the topplate only, these are pushing screws, andthree which are a clearance fit through thetop plate and are tapped into the ring, theseare pulling screws. As the pushing and the

Fig. 6 (left).-The tangent wheel,

screw, etc.

Fig. 7 (right).-Sectional view ofthe driving clock,showing the wind-ing drum and

governor gear.

scALE:.

September -October, 1950

check against excessive speed; it must becapable of giving up some of the workwhich is being put into it as well as absorb-ing more. There should be a nice sharingup, between the governor and the telescope,of the power expended by the falling weight.

In addition to, and in conjunction with,the height of the ring, further adjustment isavailable by the positioning of the balls onthe screwed arms; to increase the speed andreduce the leather friction the balls arescrewed inwards and vice versa. For perfectrotation balance both balls must be exactlythe same distance from spindle E and theyshould be secured by the knurled lockingnuts shown in Fig. 7.

r1CRIEVI1APT.1 TANGENT

rubbing when the full load of driving thetelescope comes on the clock; not revolvingwithout making contact nor even just lightlyrubbing, for the governor is not merely a

Fig. 8.End view of driving clock.

2, a M 5,INCHES..

In the mechanism of the clock there is onegear which calls for some explanation:that large internal one with whichpinion a meshes. The shape of wheelA is such that it is not possible,with ordinary cutters, to form teeth of theusual pattern; therefore the wheel ismachined with an internally projectingflange. This flange is carefully and accur-ately divided up to the correct pitch, on ascribed circle of pitch -diameter, drilled andsteel wire pins inserted to serve as teethwith which a will engage. This type of gearis perfectly satisfactory: it has been fittedin far ,larger driving clocks than the onewith which we are now concerned. Nearlyall alarum clocks have this form of construc-tion in pinions.

The spindles or shafts in the clock are allof steel. Gear wheels and pinions of hardbrass or gunmetal with the exception of E.which is turned from a length of pinion wire.The case of the clock is of steel plate; plan-ished plate, if it can be obtained. The longdriving connection B2 is of heavy -gaugebrass tubing. All bearings are of cast gun-metal.

Changing the Driving SpeedThe changing of the driving speed from

sidereal to lunar rate, to which I made earlyreference, is accomplished by a simple devicewhich raises the spindle E, and with it thegovernor balls and leathers ; thus, by aslight increase of friction, causing the clock,and with it the telescope, to rotate moreslowly. The design for this changing device

September -October, 1950 NEWNES PRACTICAL MECHANICS 25

is shown partly in Fig. 7, and more com-pletely in Fig. 8, where it will be seen thata long -armed bell -crank is fitted. The upperhorizontal member terminates in a flat en-largement on which, when the arm is raised,spindle E rests. The lower end of the verti-cal arm has a radially curved part with asloping face; on this face presses an adjust-able screw carried by a semi -rotary leverwhich, by a knurled nut, can be clamped in

either position L or S, Fig. 8, L being thelunar rate position and S the sidereal. Thusit is possible by slackening the knurled nut,swinging the lever and re -clamping, to in-stantly change from one rate to the other.

Electric Slow-motionBefore closing this article I might add that

it is possible to fit electric slow-motion tothe epicyclic drum on the clock in place of

the hand -operated cord, and if any readershould be sufficiently interested I will, afterreceiving an inquiry, give particulars. Itwas my original intention to provide this onmy qin. reflector, and that is what therectangular downward projecting piece ofplate, below the clock bracket, was for. Itwas intended to take a six -volt reversiblemotor, acting on tangent teeth on the rim ofthe drum, but it was never fitted.'

Colour MusicThe Possibilities ofOrgan

this New Science and Details of a ColourBy Prof. A. M. LOW

0NE day in the not so distant futurewe may go to the cinema to see colour

films ; not the colour films of to -day,which are photographs .of objects in theirnatural colours, but symphonies in colourwhich are as " abstract " as symphoniesplayed by orchestras, and where the form ofthe colour in relation to actual objects willmatter as little as the relation of music tonatural and artificial sounds in the real world.

Few people realise that it was more orless a matter of chance whether in the courseof evolution human beings gained theirappreciation of music through their ears orthrough their eyes. The sense of rhythmis instinctive, found in the lowest animalsand in every main form of life. Perhaps thefirst appreciation of rhythm in all creatureswas produced by the regular rise and fallof tides. In the course of evolution someanimals developed organs particularly sensi-tive to rhythms in the air-what we now callsound. An irregular tapping on a piece ofwood produces noise, but if the taps arespaced at regular intervals and the air isregularly vibrated, it may be sound, or even" music." A xylophone, after all, is only aninstrument for producing fairly pure soundsof this kind.

High FrequenciesMany human beings hear only the vibra-

tions produced in the air with a frequencysomewhere between 52 a second and 5,000a second. This " waveband " is but a frac-tion of possible sounds. In fact, childrencan hear much higher notes and dogs canappreciate frequencies greater than areaudible to any human being. It is easyto make a whistle that can be heard by adog but is " silent " for human beings.

Over the course of centuries we have pro-duced a very complicated appreciation ofthese sounds, singly and mixed, and theresult is the art of music. In a similar waywe have also built up an appreciation ofcolour. There is good reason to believe thatearly animals, like the cat of to -day, couldrealise only the presence or absence ofcolour and not its great variety. They sawthings in terms of black, grey and white. Wehave evolved eyes which are able to dis-tinguish far more narrowly between thedifferent light vibrations, just as we haveevolved ears able to distinguish between thedifferent air vibrations we call sound. Per-haps only an unbelievably expert musiciancould distinguish between two tuning forks,one giving 44o vibrations and the other 44tper second, but the great mass of people areable to distinguish between sounds " aquarter tone " apart and thus hear melody.

So with light. It is estimated that a well -trained eye can distinguish between some-thing like too,000 different colours or" shades " which, of course, is far more thanthe range of frequencies produced even by

a full orchestra. The ordinary person could,perhaps, distinguish between half this num-ber of colours. Even this represents only asmall fraction of the " possible " colours.The shortest light waves that can be appreci-ated by the eye are those we call violet-is/ too,000,000ths of an inch long. Thelongest are 3o/too,000,000ths of an inch.Obviously, between these two ranges thereare millions of minute differences. In addi-tion there are theoretical reasons for believ-ing the evolution of the eye is not completeand that, as we have come from the blackand white stage of the cat to our presentsensitivity, so we may go on to the pointwhere we sense not four primary colours butover too.

Association of Sound with ColourThere is no doubt that certain sounds are

associated with various colours. It is noaccident that many famous pieces of musichave " colour " names ; heavy chords aregenerally thought of in terms of sombrecolours. Many experiments have been madeto determine the reaction of the averageperson to sound and colour in combination ;it is now well established that the humanbrain has become more sophisticated in itsdemands for pleasure. Simple primarycolours please primitive peoples. Towndwellers demand not only subtle shades incolour, but colour also as an accompanimentto their entertainment, particularly dancingand theatricals.

The various colours are just as capable ofbeing built up into " music," with melody,harmony and rhythm as is sound ; indeed,it was more or less an accident that we chosesound rather than colour for our music.Colour " music " can appeal to the eye assound music appeals to the ear. At varioustimes attempts have been made to introduceperformances of colour music ; in the mainthey failed because they could rely only onplacing the colours side by side or by usingprisms which did not give any blending orevaluation of each colour note. They weretherefore as crude as a native orchestra anddid not sufficiently entertain the civilisedcolour sense.

A Colour OrganThe possibilities of colour music have long

fascinated artists, and a large number ofexperiments have been made in attempts todiscover how colours could be produced atwill by a musician. It seems clear that thedesired effect of blending could never beobtained by the aid of solid screens andprism effects, however complicated, andthat liquid colour is the only possiblesolution. This is the principle of the latestdiscovery, a colour organ. The actualinstrument is very small and consists of aglass screen over which a thin film of watercan be made to flow. This screen need be

no larger than a penny and is placed almostimmediately opposite the source of light ina position equivalent to the gate of a cinemaprojector. Surrounding the liquid constantlymoving screen are tiny colour containers,each providing its own spectrum colour-violet, indigo, blue, green, yellow, orangeand red.

Each container is operated electrically bya valve connected to keys like those of anorgan ; the actual drive is by compressedair. By playing on these spectrum coloursit is possible to project not only any colourfor any desired length of time (the rhythm),but also any combination (the harmony andmelody). The colours can be thrown on toa screen, but a different type of display canbe obtained by directing the colour beamson to forms ; human forms or a wall. At thetouch of a key a bowl of flowers can beilluminated with invisible light so that theflowers appear to stand out against darknessin colour which can be changed at the flickof a button. The keys can be operated bya colour musician or by a record whichwould repeat any pre -determined rhythm ofcolour. Colour resPonse can also beobtained automatically from definite musicalnotes.

The apparatus is minute ; a valve nolarger than a pin gives the effect of a shim-mering snow -storm on a building by inject-ing on the glass screen a trifle of aluminiumpaint. But the " snow -storm " through thelight beam could embrace the whole ofBuckingham Palace and be of any colourshade or localised colour. In practice, andon a full scale, the effect is like that of agiant provided with enormous brushes work-ing on a great canvas, stippling or splashinga corner of a building or " washing " thewhole surface in a fifth of a second and thenchanging to another colour in the same way.Parts of the screen can be coloured in avariety of colours by light, quick touches onthe keys, and depth is controllable by " base "keys exactly as in the case of sound music.Our imaginary giant could wash a buildingin an instant with one colour, graduallyedging it away with others if he wishes, orin another moment alter the whole set andbuild into it colour pictures and tones justas a musician would play a sonata on thekeys of the finest organ in the world.

PossibilitiesThe possibilities of this new art are

exciting. No doubt we shall have " high-brow " abstract compositions in whichcolours and tones are blended and succeedeach other like the notes in a quartet orsymphony, without any regard to naturaleffect or form. But, at first, it might beexpected that colour music would be usedrather as an adjunct to the other arts, justas for many years music was more or lessrestricted to aiding or illustrating dancingand marching.

Colour organs may soon be seen in dancehalls, where they could provide tremendousatmosphere and " backing " to the musicmuch more subtly than by the present crudeswitching on and off of lights. A new arthas certainly been born ; it has immenseand very beautiful opportunities.

26 NEWNES PRACTICAL MECHANICS September -October, 1950

Scale Model "Duke of Lancaster" : Model Foden Steam Wagon : A Fine Architectural ModelWE do not need to be seafarers to appre-

ciate the fascination of a ship model,whether it be a four -masted sailing shipor the latest modern liner. I know readerswill be interested to know something abouta model of s.s Duke of Lancaster, oneof three ships built for the L.M.S. Railwayin 1928 by Wm. Denny & Bros., Ltd.,Dumbarton. The two sister ships were

By "MOTILUS"

repainting and reconditioning for BritishRailways, London Midland Region. Themodel is to a scale of * in. to I ft.

Model Foden Steam WagonNot long ago I heard from an enthusias-

Fig. 1.-A model of S.S. " Duke of Lancaster," built in 1928 for the L.M.S. RailwayCo., for the Heysham -Belfast service. The model, to a scale of tin. to ift., has recentlybeen reconditioned, as shown in the photograph, and is now in the possession of the London

Midland Region of British Railways.

Duke of Argyll and Duke of Rothesay, andall three were for the Heysham -Belfast ser-vice.

The ships were similar in size : length36o ft., moulded breadth 53 ft., tonnage3,794. The shaft horsepower was 8,1ooand maximum speed 21 knots ; they couldeach carry 1,50o passengers. During thewar these steamers were requisitioned andtook part in the evacuation from St. Valery,the Dieppe raid and D -Day operations.

The Duke of Lancaster was first em-ployed as a military transport at the out-break of war but soon afterwards returnedto her home port. She was again calledup and converted to a hospital ship inreadiness for D -Day. During the ensuingactivities she was the first hospital ship tocarry out successfully her mission with-out mishap. She continued in this servicefor four months, and in October, 1944, wasdiverted to the services from Ostend, Dieppeand Cherbourg. After the war she was re -equipped for peace -time duties and returnedto Heysham.

The illustration, Fig. r, shows a modelof the Duke of Lancaster after recent

tic model -maker in Australia, Mr. GeorgeWaines, of Innisfail, N.Q. Mr. Waines hashad a Foden steam wagon under construc-tion for some considerable time and wroteto tell me it was at last completed. He alsosent me some photo-graphs of thefinished model, oneof which is repro-duced here (Fig. 2).All the material andfinished fittings forthis model camefrom England.

Mr. Waines sup-plied me with quitea number of detailsabout the materialsused, .etc., whichmay be of interest toother model -makers.The boiler is madeof 3* in, diameter,13 gauge brass tub-ing. The fire -box isof 12 gauge sheetbrass and the end -

Fig. 2.-The modelInnisfail, Australia.

plates are cast brass. Five boiler tubes of7/16 in. outside diameter are fitted and theboiler is fired with a silent Primus burner.The eccentrics are an exact copy of thoseused in actual practice. A 5/16 in.diameter, double throw, built-up, 9o° crank-shaft drives through a train of gears to a

in. pitch cycle chain and 2 -toothsprockets.

Regarding castings, the flywheel is iron,chimney, smokebox and wheel hubs arealuminium alloy, and the remainder are allgunmetal. All were made at local foundries,to Mr. Waines' own patterns. The body-work is done entirely with 18 and zo gaugesheet steel. The finished model weighsabout 3o lb., unladen : its measurementsare, overall length 29 ins., height 53 ins. andwheelbase 17 ins. Incidentally, most ofthe machining was done on a wood -turninglathe over a hundred years old.

A Fine Architectural ModelA well -constructed architectural model

always has an appeal for lovers of goodcraftsmanship. The model just "completedthis year by Bassett-Lowke, Ltd., of theextensive buildings of Messrs. J. Bibby &Sons, Ltd., Liverpool, is a good represen-tative example of this type of modelling.To those who do not know these largefactory and warehouse buildings on Mersey-side, the accompanying illustrations, Figs. 3and 4, will convey some idea of the extent ofthese premises.

Messrs. J. Bibby & Sons, Ltd., are anold -established company, their historydating back to 1829, when the Bibby familycame into possession of the Condor flourmill, purchased by Mr. Edward Bibby. In1854 Mr. Bibby died and his second son,James, took over the mill and opened awarehouse in Lancaster for the sale df flourand provender. Later he took into partner-ship his two younger sons, Joseph and James,and in 1878 the name J. Bibby & Sons wasadopted. Within the next ten years the

Foden steam wagon built by Mr. G. Waines, ofA trim model, with some good detail work.

September -October, 1950 NEWNES PRACTICAL MECHANICS

business expanded rapidly, introducing newideas in cattle feeding preparations. During1885 premises in Liverpool were acquiredand the head office moved to Liverpool in1888.

Since that time the company have under-taken vegetable oil production soap manu-facture, compound cooking fats manufac-ture, as well as continuing their animalfeedingstuffs business and engaging in pro-gressive research and development. Twoexperimental farms, established in Cheshire,assist in the development work in produc-ing nutritive animal feedingstuffs.

Remarkable DetailThe model illustrated here does not show

anything of the amazing interior of thesefactory and warehouse buildings, with theirnumerous complicated machines and equip-ment connected with the business. It isa wholly exterior model, built to a scaleof 1/16 in. to t ft. and measuring 5 ft.to in. long, 4 ft. 2 in. wide and 15 in. high.It incorporates the five major buildingblocks, and shows clearly all approaches byroad, rail and river. There are railwaysidings and a portion of the elevated railway,with locomotive and trucks; transport

Fig. 4.-Another view of the model of Messrs. Bibby's premises, this time showing the roadfrontage, with the administration offices at the extreme left.

vehicles are shown approaching along theroadway, and barges and a small cargo vesseladd realism to the riverside aspect.

The buildings are shown in- full relief,with recessed glazed windows, recessedpanels in brickwork, all pilasters, plinths,

. mouldings, copings, etc., and glazed roof -lights, connecting bridges and pipework.Finished in correct colours, the model is amost realistic presentation of the extensiveand varied premises of this well-knowncompany.Popular Model Railway Gauges in U.S.A.

Last March an American model railwaymagazine reported its annual survey of modelrailway fans in the U.S.A. The two mostpopular gauges among model " railroad "owners are still HO (00 in this country) andGauge 0. Gauge HO came first with 69.3per cent. and Gauge 0 second with 22 percent. Others gauges made up the remaining8 per cent. or so.

The survey is most comprehensive, andnot only measures the popularity of thevarious gauges but also gives percentageson the occupations of the enthusiasts, theirages and incomes.

The largest percentage of owners are in

27

Fig. 3.-A complete view of the fully -detailed architectural model of the factory and ware-houses of Messrs. J. Bibby & Sons, Ltd., Liverpool. The model is to a scale of 'tin.

to 'ft.

the professional classes (22.3 per cent.), butstudents run very close, being 22 per cent.Skilled workers make up another 19.9 percent. In the age groups, about 7 per cent.of model railroad owners are under 55 years,18 per cent. are between 25 and 29 years,16 per cent. between 3o and 34 and 13 percent. between 35 and 39. By the time theyreach 70 years and over they have dwindledto .3 per cent.!Standard Gauge I Dimensions

Model makers interested in Gauge r modellocomotives and railways will be glad tolearn that standard Gauge 1 dimensions havebeen drawn up in collaboration with enthus-iastic Gauge 1 modellers. Blueprints, in-corporating all these details, are nowavailable. They are comprehensive and dealnot only with locomotives but also withsignals, tunnels, under- and over -bridges,points, platforms and other necessary mea-surements for Gauge s indoor or outdoorlayouts. The measurements are given ininches and millimetres. The price for theblueprints is 3s., post free, from Bassett-Lowke, Ltd., Northampton, or from theirLondon and Manchester branches.

Newnes' Engineers' Reference BookEdited by F. J. Camm

THE third edition of this important standardreference book contains nearly 300

pages of new matter in addition to completerevision. The new sections cover FanEngineering ; Centreless Grinding ; Induc-tion Heating ; Plain Bearings ; Belt Trans-mission ; Investment Moulding ; Lappingand Honing ; Hobbing ; Surface Finishing ;Properties of Plastics ; A'r Compressors ;Compressed Air Data ; Corrosion Treat-ment ; Mirror Finishing Polishing and Buff-ing ; Gas Welding ; Weights ; AdditionalScrew Thread Tables ; eights ofMaterials ; Use of Rubber in Presses ; Shaft-ing ; Pipe Flanges ; Lighting of Buildings.

The book comprises over 1600 pages, fullycross-referenced, and hundreds of diagrams,tables and formula' of great value to mech-anical, civil, structural, automobile, and aero-nautical engineers, designers, draughtsmen,works managers, gauge and toolmakers, timeand -motion study engineers.

It costs 45s., or 46s. by post.

OUR COVER SUBJECTTHE National Aeronautical Collection at

the Science Museum, South Kensington,London, S.W., was re -opened to the publicrecently. Located in the Western Galleriesof the Museum the collection contains manyof the world's most famous and historic air-craft. Fully representing the history anddevelopment of aeronautics from the earliestconception of flight to the latest rocket -propelled aircraft the National AeronauticalCollection has become the rendezvous of allinterested in the history and development ofaeronautics. Progress in aviation is exten-sively illustrated from the original Lilienthalglider to the world's first successful jet-propelled aircraft. The rapid developmentof aircraft propulsion is clearly shown in allstages from the original steam aero-engine ofSir Hiram Maxim to the latest Rolls-RoyceDerwent V gas -turbine.

Our illustration shows a view lookingthrough the galleries. The plane hangingfrom the roof is a Vickers Vimy Rolls-Royce.This aeroplane made the first direct trans -Atlantic flight on 14th/15th June, 1919,piloted by Alcock and Brown.

28 NEWNES PRACTICAL MECHANICS

Compound Mitre and Shaving MachineANEW machine, known as the Mitor

No. 302 compound mitre and shavingmachine, was recently placed on themarket by Mitor, Ltd., 4, Vaughan Road,Harpenden, Herts. The machine, which is

The Mitor No. 302 compound mitre andshaving machine.

made from the best quality mild steel, hasa tungsten steel blade, and will produce per-fect mitres and joints. It will also cut atall angles from 45 deg. to 90 deg. in bothdirections, flat or on edge. Provision is madefor precise mechanical locking at bothextremes, and there is a clamping screw forall intermediate angle settings. The newmachine, which has a cutting capacity of tin.by tin., weighs 251bs. and is priced at 98s. 6d.

Multicore Model Television FactoryAT the National Radio and Television

Show, Birmingham, Multicore SoldersLimited specialised in practical solderingdemonstrations, and the special manufacturingfeature this year was undertaken by factoryoperatives from the works of the GeneralElectric Company.

The complete centre section of Multicore'slarge island stand was laid out to representan interesting cross section of a typical tele-vision assembly line, together with an ingen-ious floor design enabling the public to viewthe assembly operations very closely. TheG.E.C.'s works staff, who come fromCoventry daily, assembled R.F. units for theG.E.C. Television Model No. BT.2547, eachunit involving the assembly of approximately6o parts. The complete operation, including53o Ersin Multicore solder joints, took morethan one hour, and the completed units werethen despatched to Coventry for testing andincorporation. A special collection anddelivery service between the Multicore standand the G.E.C. works enabled the dailysupply of parts and completed units to beexchanged.

September-bctober, 1950

Cable End IdentificationTO simplify identification in complicated

electrical circuits, the use of some formof cable marker is now becoming standardpractice. Various forms of marker havebeen employed, ranging from the hand-written paper tag to the more elaboratethimble -shaped, engraved, plastic cable -endferrule.

Due to its Suability, neatness and legi-bility the last named has always been regardedas the most satisfactory method of identifica-tion, but even this has its disadvantages asmany firms find it impracticable to carry

The Critchley interlocking plastic cable -endferrule.

large stocks of these specially engravedferrules. In order to eliminate this difficulty,Critchley Bros., Ltd., of Brirnscombe,Glos., have designed a fully interlockingplastic ferrule consisting of several units,each of which is engraved with a single digitor letter.' From these an almost unlimitednumber of code numbers or combinationscan be built; in fact, more than 5,000 differ-

made up from astock of ferrules numbered from o-9, usingonly a three -figure code.

To prevent the digits or letters from move-ment, each ferrule unit is made with a keyand keyway (see illustration) which ensuresthat they can only be assembled with theengravings in line and cannot come out ofalignment at any time. These ferrules canbe supplied in black with white engravingor vice -versa, and other colours can be sup-plied to order.

Entry of cables from both right and left,without one side reading " upside down " isprovided for by ferrules being engraved foreither hand as required.

Duraplug Plugs and SocketslAT W. HAFFENDEN, LTD., Rich -If V borough Rubber Works, Sandwich,

Kent, have recently placed on the market arange of rubber plugs and sockets, designedto withstand the hardest knocks. The all -rubber casings ensure perfect insulation, andthe flexible pin mounting provides good con-tact, and permits use in standard 2 -pin

A " Duraplug " 5 -amp. rubber socket, and aplug.

A Review of the LatestAppliances. Tools and

Accessories

sockets by the removal of the earth pin. Thenew Duraplug is fitted with a cord gripand, apart from the feature that it is un-breakable, it has the advantage that no metalparts are exposed. If necessary, it can beused as a floating connector. The plugs andsockets are made in three sizes -2 amp.,5 amp., and 55 amp. at retail prices rangingfrom 5/9 to 3/6.

"Marlco Tool ProtractorANEW tool for the rapid and accura:e

measurement of tool angles was recentlyintroduced by W. H. Marley and Co., NewSouthgate Works, 105, High Road, London,N.55. Correct tool shape is recognised as anessential factor where maximum productionis to be attained, and visual inspection of thefinal shape has in the past resulted in a greatdeal of wasted time and effort. With thisinstrument, which is simple to operate, thefinal shape is accurately measured whetherthe tool be hand or machine ground. Allangles relative to the cutting edge of suchtools as turning bits, can be measureddirectly. It is also useful for measuring theindividual components of any compoundangle.

The " Marlco " tool protractor is a preci-sion instrument, the bearing end of the

The " Marlco " tool protractor.

pointer being hardened and tempered, thusensuring long life. An indent plungerlocates the upper bracket (carrying the mainscale), in the zero position, and it is in thisposition that the majority of angles aremeasured. The price, packed in a steel boxwith instruction card and table of suggestedtool angles, is £6 5s.

15 -amp. rubber

Ex -Government RadioEquipment

THE Clydesdale SupplyCo., Ltd., have just

issued their new list (No. 7)of Ex -Government electronicand radio equipment. Thishandy list, which runs to236 pages, includes suchitems as accumulators, ampli-fiers, cathode - ray tubes,chokes, condensers, televisionequipment, metal rectifiers,transformers and a host ofother components in demandby experimenters. The list,which is priced at 6d., isobtainable from the abovefirm at 2, Bridge Street,Glasgow, C.5.

September -October, 1950 NEWNES PRACTICAL MECHANICS 29

1500 FEET BEAM RANGEFOCUSING TORCHThis latest addition to our range of American Type Focus-ing Torches uses five U2 type batteries.

Solid brass nickel -plated construction with pull outcarrying loop in base and spare bulb container.

ADJUSTABLE RING FOCUS HEADTits torch is specially suitable for protective purposes.Other long bearn torches as previously advertised are still

available as follows :-Tyne A. 700ft. beam range, otherwise as above 15/11 postType G. 600ft. beam range, small diameter head

for concentrated beam, otherwise as above 13111 Free.

MOTOR ALTERNATORSA super Admiralty equipment in grey

steel cabinet. With a D.C. input of 24 v., afully regulated output of 230 v. 50 c/s. A.C. isobtained. The equipment incorporates astarter switch, and the output is meteredby means of an A.C. Voltmeter. A controlswitch and fuses in both A.C. and D.C.circuits are also incorporated. 14Rating 80 watts. BRAND NEW.

STORAGE BINSA useful steel bin. Size 6in. x 5in. x

Open at both ends (6in. x 5in.), and rein-forced at the open ends. Fixing 1

bracket fitted. Plain mattblack, pest free.

MINE DETECTORSBrand new equipment com-

plete in transit case as pre-viously advertised.

FLEXIBLE COUPLERS 6 forAn Insulated spindle coupler

to take tin. dia. shafts. Outside 7dia. of coupling liin. post free.

CANVAS JACKETSA very durable men's canvas jacket.

Ideal for cyclists, mechanics, Al 11working M garage, etc. Twopockets fitted. Two sizes. post free.

EYESH I EL DSFor the cyclist, motor -cyclist, etc. Assupplied for use in anti- 20 forgas measures. Ideal for pro-

tection of eyes when using grind- 3/6stone, lathe, etc., or for workingunderneath car chassis, etc. post free.

79/6carr. paid.

Th-22/6 free.?

Complete with bat-teries and b u 1 b.FULLY GUARAN-TEED. 3lin. dia. head.1 5in. overalllength. Sparebatteries 5d.each. Spare bulbs,ed. each.

TAPE AND WIRE RECORDERMOTORS MADE BY B.S.R.

This small induction motor is speciallydesigned for magnetic twee and wirerecorders. Absolutely sileift in operatiqnand vi rtually free from vibration.Minimum, stray magnetic field. 2ft -For A.C. mains 100-250 volts 50 1cycles, rost free.

100 WATT AUTO TRANS-FORMERS

Small, sturdy and reliable auto -trans-former, for using 110 volt equip-ment on 200-230 V. A.C. mainsor vice versa. BRAND NEW, 9d. postage.

Terms : Cash with Order

MAIL ORDER SUPPLY CO.The Radio Centre

33, TOTTENHAM COURT ROAD,LONDON, W.1.

Telephone : MUSeum 6667/8/9

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The Pelman Course is based onover 5o years' intensive study con-current with experience in dealingwith the difficulties, failings, fears,aspirations and ambitions of morethan '5o,000 men and women of allages and occupations in all parts ofthe world.

You would like your affairs toprosper and your income to increase.Pelmanism will .help you to achievethis and will enable you to developthat zest for living which comes withan awakened mind ; also withquickened mental powers, your.awakened ability will enable you toenjoy those purchasable pleasuresthat come with extra money.

The Pelman Training is scientific,precise and individual. It can help tomake this year a fruitful one for you.

Pelmanism will rapidly and per-manently banish such defects and .weaknesses as :-Worry, Frustra-tion, Indecision and Lack of Con-fidence.

Remember-Everything you do ispreceded by your attitude of mind

HOW TO LEARN LANGUAGESThe Pelman Languages Instituteteaches French, German, Spanish andItalian without translation. Write forparticulars and specimen lesson of thelanguage that interests you, whichwill be sent gratis and post free.Reduced fees for serving and ex -Service

members of H.M. ForcesPelman Languages Institute,

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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

Rooms, 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& S ON, LT?ILFORD EsT. 1857 ESSEX

30 NEWNES PRACTICAL MECHANICS September -October, 1950

The 84 pages of indexed place -to -place road routes areinvaluable to the tourist, rendering maps unnecessary.

EVERY Cyclist's Pocket Book, just published at 7/6, or7/10 by post from George Newnes, Ltd., Tower House,Southampton Street, Strand, W.C.2., contains 400

pages and t r8 illustrations, is a pocket book in the real sense.Measuring only sin. by 31in., it contains facts, figures, form -nix and data never before published, on almost every aspectof cycling.

It is a technical pocket book and a general pocket book,the need for which has been felt ever since the author'sprevious volume, Every Cyclist's Handbook, a best seller,went out of print over n years ago. This present volume,which will be a constant companion to the cyclist, the cycletourist, the cycle mechanic and the technician, is packedwith information not to be found in any other one book,It deals with every part of the bicycle, including maintenance.overhauling and re -enamelling.

Apart from the technical information there are no lessthan 84 pages of indexed place -to -place road routes, whichwill save a great deal of map hunting, aud, in fact, forordinary touring purposes render maps unnecessary.

The book is lavishly illustrated, and the following list ofsection headings indicates its truly comprehensive nature :Bicycle Measurements ; The " Gear " of a Bicycle ; Frames ;Standard Frame Angles ; Handlebars ; Saddles ; Brakes ;Pedals Chains ; Chain Wheels and Sprockets ; The VariableGear flub ; Derailleur Gears ; Tyres ; Rims ; Clothes andEquipment ; Tandems ; Lamps ; Cyclometers ; AdjustingBearings ; Re -enamelling a Bicycle ; Overhauling a Bicycle ;Wheel Building ; Calculating Spoke Lengths ; Summaryof Cycling Law ; Touring ; Touring by Numbers ; Map

A

CYCLIST'S

"BIBLE"!

Just Published

The HandiestPocket Book

forCyclists

A New 400 -page Pocket-size ReferenceBook, Road Guide and Technical Hand-book for Cyclists, Written by F. J. Camm

Reading; Road Routes Simplified; Cycle Camping; TouringAbroad ; Interesting Cycling Facts ; National Clubs andAssociations ; Railway and Cloakroom Charges ; CalculatingSpeed from Pedal Strokes Table of Gradients ; Constantsfor Reckoning Speeds; Table Showing Speeds per Hour;Gear Table for Single -speed Machine ; British StandardCycle Threads ; Cycle Threads for Spokes and Nipples ;Lighting-up Variations; Road Records and Routes; Recordsand Standards ; Women's Road Records ; Principal RoadRoutes of Great Britain ; Road Statistics ; and Bicycles inUse Throughout the World.

The technical, information includes : The Proportion ofCycle Screw Threads ; Chain Sprockets and Chain Wheels ;Spoke Lengths; Speed in Miles per Hour; The Three -speedHub ; etc. etc. A fascinating section is that entitled" Interesting Cycling Facts."

The author of this volume needs no introduction tocyclists. He has been intimately associated with the industry,pastime and sport all his life. Famotis as the author of manystandard text -books on engineering, radio, mathematics andtelevision, and as editor of an important group of technicaljournals, he has served on many important cycling com-mittees, was founder -editor of The Cyclist, founder of theCyclist Road Club, founder member of the Roadfarers'Club, Famous Time -keeper and expert on Horology. Hestill maintains an active interest in cycling as a pastime,as his articles in The Cyclist Supplement to this journalindicate. His shrewd criticisms are valued through cycledom,and his advice on all cycling topics is keenly sought.

The publication of this book is an event because it representsthe accumulated knowledge of a lifetime, and makes good aserious gap in cycling literature.

The handy size of this 400 -page pocket book, packed with hundreds of facts andfigures, is apparent from this illustration.

September -October, 1950

GALPI N SELECTRICAL STORES

4C8, HIGH STREET, LEWISHAM,LONDON, S.E.13

Tel. : Lee Green 0309. N r. Lewisham Hospital.

TERMS: CASH WITH ORDER.NO C.O.D.

THURSDAY EARLY CLOSING.

EXTENSION P.M. SPEAKERS, 3/,,in.by Johnson & Phillips, will handle I watts.New boxed, 716 each. Post 9d.EX R.A.F. MICROPHONE TESTERS.These contain a 2Iin. scale 0 to 450 Micro -amp meter shunted to I mIamp. calibrated0 to 10 volts moving coil, complete with

1 mA. rectifier, "Mike transformer," etc.,all contained in polished wood box, as new,1716 each.MAINS TRANSFORMERS, 2001250volts input in steps of 10 volts, output350101350 volts 180 mlamps., 4 volts 4 amp.,5 volts 3 amps., 6.3 volts 4 amp., 3716 each,ditto 500101500 volts 150 mlamps. 4 volts4 amp., 5 volts 3 amp., 6.3 volts 4 amp..4216 each ; ditto 425/0/425 volts 180 mlamps. 6.3 volts 3 amps. twice, 5 volts 3amps. (Williamson Amplifier), 3916 each ;ditto, 35010/350 volts 180 mlamps. 6.3 volts8 amps. 5 volts tapped 4 volts 3 amps.,3916 each.EX R.A.F. D.C. TO D.C. MOTORGENERATORS, 24128 volts input, 1,200volts 72 mlamps. output, as new, 716 each,post 116.MAINS TRANSFORMERS, 230 voltsA.C., 50 cycs. input 17,1, volts 50 amps.output, 5216 each, carriage 51-, anotherauto wound, output 14 and 17 volts outputat 30 amps., 351- each, carriage 3/6 ; anotherwith 2 x 4 volt 20 amp. windings, 251- each,P1f.PRE -PAYMENT II- SLOT ELECTRICLIGHT CHECK METERS, all elec-trically guaranteed, 2001550 volts 50 cycs.

I ph., A.G. input, amp. load, 2716 each ;

5 amp. load, 351- each ; 10 amp. load, 4216each ; 20 amp. load, 501- each, carriage 21 -extra ; in quantities of one dozen or morea special discount of 10";,.POWER TRANSFORMER AUTOWOUND voltage changer tapped 0, 110,150, 190 and 230 volts at 1,600 watts,E5151- each, carriage 316 ; ditto, 2,000 watts,E6151- each, carriage 3/6 : another tapped0, 110, 200, 230 volts at 350 watts, at 4716each, carriage 21-.MAINS TRANSFORMERS input 2001250volts, 5011 in steps of 10 volts, outputtapped 0, 6, 12 at 24 volts at 10112 amps.,471- each ; ditto as above but at 25130 amps.output, 6816 each.MAINS TRANSFORMERS, 2001250volts 5011 ph., in steps of 10 volts. Output500101500 volts 300 mlamps., 6.3 v. 8 a.,6.3 v. 8 a., 6.3 v. 4 a., 5 v. 4 a., 4 v. 4 a., at6716 each : another same input, outputs,450101450 volts 300 mlamps., 6.3 v. 8 a.,6.3 v. 8 a., 4 v. 5 a., 5 v. 4 a., at 6216 each.CELL TESTING VOLT -METERS, mov-ing coil, reading 31013 volts by well-knownmakers, complete with test leads, 716 each.MAINS TRANSFORMERS, 200/250volts, input in steps of 10 volts, output350101350 volts 300 mlamps., 4 volts 4 amp.,5 volts 4 amp., 6.3 volt. 8 amp., 6.3 volts8 amp., 6216 each. Smoothing chokes 10Henry 100 mlamps. 200 ohms D.C. resis-tance, 5/- each.MAINS VARIABLE SLIDER RESIS-TANCES, protected type, by well-knownmakers, 450 ohms, .9 amps., 2216 each ;

ditto, 1,500 ohms to carry .45 amps., 2216each, not protected, 0.4 ohms, to carry25 amps., I0/- each ; 14 ohms to carry114 amps., 1216 each.EX GOVERNMENT AUTO WOUNDTRANSFORMERS (as new), 1,000 wattsoutput 1151230 volts or vice versa, (41101 -each, carriage 51- ; another 1,000 wattsfrom 5 to 230 volts with various tappingsinclusive of 110, 150, 60, 90, etc., etc., alltapping at 1,000 watts, E51101- each, carriagepaid.MAINS TRANSFORMERS, input 2001250 volts in steps of 10 volts output350101350 volts. 300 mlamps. 4 volt 8 amp.,4 volt 4 amp., 6.3 volts 6 amp., 3.6 volts 2amp., tapped at 2 volts (electronic) at 5716each ; another same input as above, output500/350/013501500 volts 250 mlamps. 5volts tapped at 4 volts 4 amps. twice, 6.3volts tapped at 2 volts 2 amps., 6716 each.MAINS SMOOTHING CHOKES bywell-known makers, weight 7lbs. for 50cycle mains, 415 henries at 250 mlamps.D.C., resistance 50 ohms, 151- each,carriage II-.EX R.A.F. ROTARY CONVERTORS,24 volts D.C. input. 50 volts 50 cycs, 1

phase at 450 watts output complete withstep-up Transformer from 50 to 230 voltsat 450 watts, E81101- each, carriage paid.

NEWNES PRACTICAL MECHANICS 31

toHOBBY KNIVES and TOOLS

with interchangeableSCALPEL -SHARP BLADES

No. 5 Knifefor really heavy duty.Takes all blades, thesix gouges, the fourrouters and the twopunches. With r ILone No. 19 blade, Jr.'

You do finer work faster withX-acto knives. The scalpel -

sharp blades are the sharpest

you can buy -and they stay

sharp. They do not bend

over or work loose, the

draw collet of the X-actohandle holds them in a

vice -like grip - yet they

can be changed in a few

seconds. There are

thirteen blade shapes

for special jobs, and

the larger knife

takes punches,

gouges androuters as well.

No. 2 Knifefor normal cutting.Takes all thirteenblades. With oneNo. 22 blade, 2/6

No. I Knifefor light and delicatework. Takes bladesNos. to, II, 16 and17. With oneNo. 1 1 blade, 4/0

* Write for details of the complete range of X-acto knives and tools,and the name of your nearest stockist.

TRIX LTDII, OLD BURLINGTON ST., LONDON, W.I

HIGHSTONE UTILITIESCrystal Sets.Our latest Modelis a real radioreceiver, whichis fitted with aPermanent crys-tal detcctor.Whynot have a set inyour own room ?

6d. De

cabinet,inpolished

Luxe Receiverotia6k,

Spare Permanent Detectors, 21- each.When ordered separately, 2/6. With clipsand screws, 2/10, post 3d. Headphones,brand new, S. G. Brown, G.E.C.. etc., 15/,23,-, and super -sensitive, 30.1- a pair, post 8d.New Headphones. 10/- a pair.. Balancedarmature type (very sensitive). 12/6 a pair.Both post 6d. New Single Earpieces.3.6. Bal. armature type. 4/6 ex-R.A.F.earpiece, 2;-, post 4d. Headphones in.good order, 41 and 5/6 (better quality.7 6). all post 6d. Headphones with movingcoil mike. 15,-. Similar phones withthroat mikes. 12/6, post 8d. headphoneCords. 1,3 a pair. post 3d. ReplacementBands, 1 3, post 4d. Wire Bands. 6d.(All Headphones listed are suitable foruse with our Crystal Sets,)

Bell Transformers.These guaranteedtransformers workfrom any A.C.Mains, giving 3. 5.or 8 volts output at1 amp., operate bulb.buzzer or bell. Will

supply light in bedroom or larder. etc.PRICE 8/-. post 8d. BELLS for use witheither the above or batteries, 6/-. post 6d." Big Ben " Chimes. Housed in CreamPlastic Case. Easily connected to giveTwo -Note Chime from Front Door, andSingle Note from Rear. Operates from 6-9volt Batteries or Transformer. 15/8. post10d.Ex-R.A.E. 2 -valve (2-501t) MicrophoneAmplifiers as used In 'plane inter -corn..in self-contained metal case : can be usedto make up a deaf aid outfit, intercommuni-cation system, or with crystal set; completewith valves, 201-, post 116. Useful woodenbox with partitions to hold amplifier, 2/ -extra. Ditto. less valves. 10/-. One valveamplifier, complete with valve. 9/6, Post 1/..Hand Microphones, with switch in handleand lead, 4,-. Similar instrument, movingcoil, 7/8, post 6t1.Sparking Plug Neon Testers, with vest-pocket clip, 33, and with gauge, 3/6, post 3d.S.B.C. Neon Indicator Lamps, for use onmains, showing " live side of switches.etc.. 3/6. Post 4d.

SolderingIrons. Ournew stream -o lined Iron issupplied with

two interchangeable bits, one each straightand curved ; 200250 v. 50 wafts. 9'-. post etl.Standard Iron with adjustable bit, 2001250v.. 60 watts. 9"8. post Bd. Heavy DutyIron, 150 watts, 126. post 8d. All partsreplaceable and fully gbaranteed. SmallSoldering Irons, for use on gas, 1,4, post4d. Resin -cored solder for easy soldering.Eld. packets, or 11b. reels, 6'-, postage extra.Mierophones.-Just the thing for im-promptu concerts, room to room communi-cation. etc. Bakelite table model, 619:Suspension type. 8'6. Post 6d. MikeButtons (carbon), 2'-. Moving Coil, 4/6 :Transformers, 5'-. All post 4d. each.Rotary Transformers. 2.4v. input ; Output1,230 v. .2 amp. In case with suppressors.etc.. easily converted to run as a highvoltage motor,, 25'-, carr. 3'6. Also 12v.input ; Output 6v. 5 amp . 150 v. 10 mA..and 300v. 20240 mA., 22/6, carriage 3/6.Morse Keys. -Standard size keys wired towork Buzzer or Lamp. 3', post 6d. Slightlysmaller keys. 2'6, post 4d. BUZZERS.3/-, or heavy duty, 4 6. past 5d.Terminals, brass. 2BA. mounted on strip,6d. pair. .0005 Airspaced Variable Con-densers, 213, Post 4d. .00003 twin gang withtrimmers, 2'6. post 44. 24 -volt 15 m/m.M.E.S. Bulbs for model railways. etc.,l'- each. 10/- doz., post 4d. Wander Plugs.Brass, 1'6 doz., post 4d. Fuses. -1 amp.,llin , packet of 10. 2 6. Post 3d. Also 150 mA.and 250 mA. same price.Bargain Parcels of really useful equip-ment, containing Switches, Meters, con-densers, Resistances. Phones, etc.. 10/-,or double assortment. 178 : treble, 251 --All carriage paid. This country only.Field Intercommunication Sets, completewith ringing hand generator, bell, signallamp, morse key, relay, in strong metalcase with circuit diagram, 25/- each, carr.2,6 : 47'6 pair, carr. 3'6. Ex-G.P.O. Tele-phone Twin Bells, with box, 51-. post 9d.Telephone hand generator, with handle, 7/6.post 1,6 : Bell, 411. post 6d.Meters. 10v., 2' in. Rectifier (A.C.), inwooden carrying case. 14'6 15v.. 2lin.mre., 9:6 150v., 2in., m c.. 10:- 3,500 v..3iin., m'c., 20/. ; 6,000v., al in.. min., 57/6 :15,600v.. 2in., m'c., double reading, 8/-100 mia., 2in., m/c.. TO ; 3.5 amp. 2in., T.C.,51- : 4 amp., Vin.. T.C., in case with switch,71. Meter Movements. 2in, size withmagnet and case (500 microamp), 2/6. Allmeters post extra.Money refunded if not completely satisfied.

HIGHSTONE UTILITIES,58, New Wanstead, London, E.11.

Letters only.New Illustrated List sent on request with

ld. stamp and S.A.E.

32 NEWNES PRACTICAL MECHANICS September -October, 1950

Plans for amodel of the

Inca raftKON-TIKI '

The craft which driftedfrom Peru to the South

Sea IslesThor Heyerdahl, the builder of the' KON-TIK1,' believed that the South SeaIsles were first populated by a fair -skinnedrace, who fled from Peru by raft when theIncas conquered them about 1,000 yearsago. To demonstrate that his theorywas plausible he and five companions, fiveNorwegians and a Swede, made the samejourney on a balsa wood raft of the typewhich the ancient inhabitants of SouthAmerica are known to have used andwhich the Incas inherited from them.It is an epic story which you should readand commemorate by making a model ofHeyerdahl's ' ship.' Four sheets of /8plans size 20" x 15" post free -fM ODELCRAFT LTD.77(L), Grosvenor Rd., London, S.W.I.

LATHES ARE SOUNDIN THE HEAD

Lists 2,'- set. Refundable first order.TUe Portals Lathe & Machine Tool Co.Buttermere Rd. Tel : 51353. Sheffield 8

REFILL YOUR OWN

BALL PENVISCOID REFILL KIT

Post Free 3/8 inc. tax.COMPLETE WITH TOOL AND ILLUS-TRATED FILLING INSTRUCTIONS

CONTAINS SUFFICIENT INKFOR 15 AVERAGE REFILLS

AVAILABLE IN BLUE, RED& GREEN

TRADE ENQUIRIES INVITEDVISCOID INKS (P -M),6, SHERLOCK MEWS,

BAKER ST., LONDON, W.1

The STEPPING STONES

TO SUCCESS!Don't hesitate about your future ! Go forward,confident that The Bennett College will seeyou through to a sound position in any careeryou choose. The Bennett College methodsare individual. There's a friendly, personaltouch that encourages quick progress and

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MIDLAND INSTRUMENT CO.For Govt. Surplus Stock, etc.

SERIES MOTORS, 12 v. 20 amp. D.C.,I h.p., fitted fin. shaft, weight 9 lbs..the Ideal motor for electrically pro-pelled vehicles, electric lawn mowers.etc., new unused, 15/-, post 1/6. AUTOTRANSFORMERS, 1.6 kva., 230 v.1 phase 50 cycles. tappings for 40-80--110-120-160490 v, at 7 amps.. new unused,45/, carriage 5 -. BELL TRANS-FORMERS, input 200-250 v., output4 and 8 v. at I amp., new unused. 2/8.post 7d. RECTIFIERS, full waveselenium, A.C. input 15 v., D.C. cutput12 v. at li amp., new unused 7/6, post 7d.IMMERSION HEATERS, for waterand other liquids, 230 v. A.C./D.C.. 500watts, fitted high grade thermostatwhich cuts out at 80 deg. " C " and inat approx. 3 deg. less, fits hole 1)in.dia., flange 211n. dia., new unused 12/8,post V-. MOTOR GENERATORS,Type 34, D.C. input 24 v. 1.7 amp.,output 200 v. at 30 mA. and 6.3 v. at2 amp., new unused condition, 5/,post 1/6. BOX KITES, dinghy antennatype, in metal containers with screwcap with special flying cord, new unused.usual price 12/6, to clear 10'-, post 10d.ROMEC VACUUM PUMPS, alsosuitable as air compressors, rotaryvane type gives constant pressure atapprox. 30-40 lbs. sq. in., fittea 2in.long lin. dia. shaft, new unused 10'-.post 1/4. MOTORS fitted enclosed fanblowers, 12-24 v. A.C./D.C., new 'mused7i6. post 10d. MAINS MOTORS,200-250 v. A.C., suitable for stirrers,fans, etc., fitted 3,16in. shaft, Qin.long, 2lin. dia., 7/6, post V-. TELE-SCOPIC DINGHY MASTS. length14in, extends to 7ift.. base tin. tapersto 7 161n., weight 6 oz., ideal foraerials, microphone stands, tents.fishing rods, etc., new unused 5/-, post7d. THERMOSTATS, glass enclosed,cuts out at 120 deg. " F," new unused2'6. post 3d. NEON LAMPS, s.b.c.fitting, strike at 70-80 v.. 14 post 3d.VARIABLE RHEOSTATS, wirewound on vitreous steel, balcelitecontrol knob, 1 ohm 12 amp., newunused 3/8, post 10d. ACCUMULA-TORS, 2 v. 10 Ail, by " Exide," slackbakellte cases size 6in. x 2in. x5 -plate type with wood or zinc separa-tors, supplied dry, new and unused,5'-. post 10d.: 3 for 131. post 1,4 ;

6 for 24/, post 1/6.Hundreds of other interesting Radio,Electronic and Mechanical Viems.

Send S.A.E. for current lists.MOORPOOL CIRCLE

BIRMINGHAM, 17.Tel.: HARborne 1308 or 2664.

LONG-PLAYING RECORDS ANDRECORD PLAYERS by Decca nowavailable from stock. Send 21d. forlist of 1st release records and RecordPlayers (33 1/3 r.p.m.) with pick-up(Price £8 185.). Records available fromus by post. G.P. 20 Pick-ups. 71/5.SENSATIONAL NEW AMPLIFIERby N.R.S. : The Symphony No. 1 isthe most flexible on the market today !Three separate channels giving entirelyindependent control of bass, middleand top, also scratch cut for records.Gram. and Tuner inputs. 5 watts un-distorted output matched to 3 or 15ohms. Price £8 19s. 6d.SYMPHONY No. 2. Same theme asNo. 1, but having 10 watts push-pulloutput, superb quality. 3. 7.5 and 15ohms. Inputs for magnetic, crystaland hi-fi pickups, full provision, forTuner built on handsome black -cracklechassis, Woden mains and outputtransformers. Price 13 gns.No. 1 HIGH -QUALITY TUNER.specially recommended for aboveamplifiers and Leak, Williamson.Charles, Rogers and other qualityamplifiers. L. and M. wave T.R.F.with infinite impedance detector,illuminated " Airplane " dial withescutcheon and glass. virtually dis-tortionless. Price of Complete Kit,£4 10s.. or Ready Built, £5 10s.No. 2 QUALITY SUPERRETTUNER, L. M. and S. wave, large full -vision dial assembly, spin -wheel tuning.As Kit. £7 10s. Built. £8 105.FULL BARGAIN CATALOG UE:2i d.

TERMS C.W.O. or C.O.D.N.R.S., 18. Kings College Rd.,London, NAV.3. Primrose 8314.

MAKE MONEY INYOUR WORKSHOPSETS of CLEAR. CONSTRUCTIONALDIAGRAMS and instructions for

BUILDING YOUR OWN(1) TOY, MODEL or WOOD-

WORKER'S LATHE, 3/6.(2) Power or foot treadle drive FRET

JIG SAW MACHINE, 3/6.(3) Ball bearing Table Model CIRCU-

LAR SAW. 3/6.(or 9/- for the three.)

ALL these well tested, simple machinescan be built EASILY from READILYOBTAINABLE PARTS ANDMATERIALS ONLY and will turn out101 Saleable articles for the shops andmarket. Prompt posting.P. M. BARHAM, Bridge Avenue.

St. Sampsons, Guerns:y, C.I.

September -October, 1950 NEWNES PRACTICAL MECHANICS

QUERIEScouiENQUIRIES

A stamped, addressed envelope, three pennystamps, and the query coupon from the currentissue, which appears on page 8 (THE CYCLIST),must be enclosed with every letter containing aquery. Every query and drawing which is sentmust hear the name and address of the reader.Send your queries to the Editor, PRACTICALMECHANICS, Geo. Newnes, Ltd., Tower House,Southampton Street, Strand, London, W.C.2.

Matt Black Finish on ZincT WOULD like to produce a matt black finish onA zinc, such as is obtained on brass, by heating,dipping in copper nitrate and immediatelyre -heating.

I have tried dissolving zinc in nitric acid toobtain zinc nitrate and proceeded as for brass,but no blackening took place. Any advice you cangive me will be appreciated. -A. Leone Ganado(Malta).7INC. will not behave chemically in the same way" as brass because it is an altogether different metal.Zinc does not chemically blacken very well, so that itmight be advantageous, if you want a very good job, tocopper -plate the zinc, and then to blacken the copperdeposit by immersing the article in a weak solution ofsodium sulphide.

If, however, you want a direct chemical black stainingof the zinc, immerse it in the following solution at atemperature of about soo deg. F. (38 deg. C.) until ablack colouration of sufficient intensity has occurred :

Nickel chloride .. 2oz.'Ammonium chloride (sal ammoniac) .. 3oz.Ammonium thiocyanate (ammonium sul-

phocyanide)Zinc chloride doz.Water gallon

Cementing Rubber Sheeting to a ConcreteFloor

CAN you give me any information concerningthe adhesive to be employed to stick rubber

sheeting to a concrete floor 2-K. C. Pugh (Stret-ford).FOR cementing rubber sheet to a concrete floor

you can use either a compounded rubber solution,which, we think, you will be able to obtain in yourdistrict from the Greengate Rubber Co., Salford, orfrom Messrs. F. Reddayway and Co., Ltd., Pendleton,or, alternatively, you can employ a bitumen solution,which would be cheaper and quite as efficient.

Assuming that you elect to employ a bitumensolution. This, you may he able to obtain from Messrs.James Beard, Ltd., t6, Great Ancoats Street, Man-chester. You can either use such material or one of theblack bituminous paints supplied by Wailes DoveBiturnastic Co., Ltd., Collingwood Buildings, New-castle -on -Tyne.

To s part (by vol.) of the bitumen solution, add3 parts of paraffin or white spirit. Brush this liberallyon to the concrete floor and let it dry to the tacky stage.Treat the underside of the rubber sheet in a similarway. Then, to each of the contacting surfaces applythe full-strength bitumen paint, thinly but quite evenly.Let these dry to the tacky stage. Finally, lay the sheetdown in contact with the floor, and, preferably, use aheavy roller so that air pockets are not left between thefloor and the sheet.

This procedure will give good contact, and after afew days the rubber flooring will be found to be cementedfirmly in position.

It should be borne in mind, of course, that rubbersheeting cemented by this means is very difficult totake up again without damage. If, for any reason, itshould ever be required to remove the sheeting from thefloor, you would have to rely on the solvent powers ofhot paraffin.

" Decarbonising" SolutionsWHEN decarbonising my two-stroke motor-

cycle I find it easy enough to clean thepiston and cylinder head of carbon, but experiencegreat difficulty in cleaning the exhaust andsilencer. The baffles in the silencer prevent mefrom scraping the carbon, etc., out. Can yousuggest a simple method ?-F. H. Duggins (Bir-mingham).

DISSOLVE in a bucket of water each of sodiummetasilicate and trisodium phosphate. Dis-

mantle the silencer and immerse it, with other necessaryparts, in the solution for two or three days. This willremove the oil and grease and will loosen the carbondeposit. Alternatively,...you..can_use_in the sense volumeof water lib. caustic soda. In this case the solution must

33

not be placed in a galvanised bucket because the causticsolution would dissolve the zinc coating of the bucket.

There is no ordinary_ substance which has theslightest solvent effect on carbon. Hence, practicallyspeaking, carbon cannot be dissolved away, despiteall statements to the contrary. The grease whichaccompanies the carbon deposit, however, acts as abinder, and when this oil and grease has been dissolvedaway, the carbon is usually in a loose condition so thatit is easily dislodged by knocking or scraping.

Naturally, every trace of the solution must beremoved ,from the parts by thorough rinsing beforethey are reassembled.

If the silencer is highly plated outside, it is notadvisable to immerse it bodily in the solution. In thiscase you will have to fit a bung to one end of it and thenfill it up with the solution so that the latter does notmake contact with the alkaline liquid.

Not all highly -finished platings are susceptible tostrong alkalies, but many are. Hence, it is best to becautious about the matter when applying such alkalitreatment.

Readers are asked to note that we havediscontinued our electrical query service.Replies that appear in these pages fromtime to time arc old ones, and are pub-lished as being of general interest. Willreaders requiring information on othersubjects please be as brief as possible

with their enquiries.

Preventing Tarnish on Drawing Instru-ments

CAN you suggest a method of removing andpreventing tarnish on drawing instruments ?

-G. W. Mayes (Northampton).WE cannot give you a "general" method for removing

and preventing the tarnish on drawing instru-ments. It all depends on the metal from which theinstruments are made. Assuming, however, that theseare brass and steel, you can only remove the tarnishby fine glass -papering, because a chemical solutionwhich would remove tarnish from brass might blackenthe steel, and vice versa. Hence, with these instru-ments, it is not safe to use any chemical treatment.

To prevent the re-formation c fthe tarnish, the metal-work, after rinsing and drying and final polishing, mustbe lacquered. A good and simple lacquer for thispurpose can be made by dissclving film scrap (clear

THE P.M. BLUEPRINT SERVICE12 FT. ALL -WOOD CANOE.. New Series. No. 1.

3s. 6d.10 -WATT MOTOR. New Series.* No. 2. 3s. 6d.COMPRESSED -AIR MODEL AERO ENGINE.*

New Series. No. 3. 5s.AIR RESERVOIR FOR COMPRESSED -AIRAERO ENGINE. New Series. No. 3a. Is." SPORTS " PEDAL CAR.' New Series. No. 4.5s.F. J. CAMM'S FLASH STEAM PLANT.* New

Series. No. 5. 5s.SYNCHRONOUS ELECTRIC CLOCK. New

Series. No. 6. 5s.*ELECTRIC DOOR -CHIME. No. 7, 3s. 6d.'

ASTRONOMICAL TELESCOPE. New Series.No. 8 (2 sheets). 7s.

CANVAS CANOE. New Series. No. 9. 3s. 6d.'DIASCOPE. New Series. No. 10. 3s. 6d.*EPISCOPE. New Series. No. II. 3s. 6d.

PANTOGRAPH. New Series. No. 12. Is. Ed.*820 CAR*

(Designed by F. I. CAMM).10s. 6d. per set of four sheets.MASTER BATTERY CLOCK*

Blueprints (2 sheets), 3s. 6d.Art board dial for above clock, Is.

OUTBOARD SPEEDBOAT10s. 6d. per set of three sheets.

SUPER -DURATION BIPLANE*Full-size blueprint, 2s.

The I-c.c. TWO-STROKE PETROL ENGINE'Complete set, 7s. 6d.

STREAMLINED WAKEFIELDMONOPLANE --3s. Ed.

LIGHTWEIGHT MODEL MONOPLANEFull-size blueprint, 3s. Ed.

P.M. TRAILER CARAVAN'Complete set, 10s. 6d.

P.M. BATTERY SLAVE CLOCK' -2s:

The above blueprints are obtainable, post free,from Messrs. George Newnes, Ltd., Tower House,

Southampton Street, Strand, W.C.2.

An denotes constructional details are available, free,with the blueprint.

celluloid) in a mixture of equal parts of acetone andamyl acetate until a solution of varnish consistency isobtained. About 5 drops of castor oil should be addedto every eggcupful of this solution so that it will drywith a non -brittle, flexible film which will attachitself well to the underlying metal, and will not peel off.

Apply the lacquer to the metal by means of a camel-hair brush. Two thin coats are better than a singlethick coat. The lacquer dries within anhour or twoand will harden overnight. Have the metal veryslightly warm before you lacquer it, and do not hang it ,

up to dry in a cold damp room. Remember that thelacquer is inflammable. It must be stored in a corkedbottle, otherwise it will rapidly evaporate.

You can buy lacquer of this type from Messrs. Wm.Canning and Co., Ltd., Great Hampton Street, Bir-mingham, the price being about 7s. 6d. per pint.

Fixing Graphite on Porcelain TubesDLEASE advise me how to fix blacklead on theA porcelain tubes of resistors by spray gun orbrush. -G. Rampartap (Kampala, Uganda).MO fix a conducting blacklead (or graphite) to a

porcelain tube, first of all dissolve so parts ofgelatine in 90 parts of hot water. Brush this on to thetube. When the coating is nearly dry, dust the finestblacklead on to it. The blacklead will adhere to thetube and form a continuous layer with a conductingupper surface.

This method only applies to unglazed porcelaintubes because the gelatine solution will not spreadevenly on a glazed porcelain surface.

In this case you must brush a clear cellulose lacquerover the porcelain surface. When this lacquer is nearlydry, dust the graphite on to it as before, and then waituntil the lacquer has become properly dry. The lacquerwill now hold the blacklead particles firmly, down tothe tube so that the graphite surface so formed will havean upper conducting surface.

Damp-proof WhiteningT are the ingredients by which I couldWHAT

a really good whitening ?I wish to paint an old ceiling, and also the walls

of a basement, and would like something whichis damp-proof, and that will not rube off. -B.Anderson (Kirkdale).YOU require a flat oil paint for your ceiling and

walls. First of all, prepare and clean thesurfaces. Then brush over them a solution of hotsize made by dissolving five parts of glue in 95 partsof hot water. Let the size dressing dry out thoroughly.Then apply a flat white paint made according to thefollowing formula

Pigment 70 per cent. (by weight).Linseed oil (raw) ..t5Thinner (white spirit) 15 ,

iThe linseed oil must have mixed with t about so percent. of liquid paint driers. This means that everynine parts of raw linseed oil which you use must havemixed with it about one part of paint driers. If youomit the driers, the paint will dry very slowly.

For a white pigment you can use white lead, zincoxide, barytes (blanche fixe) or titanium white, and thepigment which you select can be " extended " ordiluted by admixture of up to half its volume of whiting.The ingredients of the above formula are all mixedvery thoroughly together, the pigment being quite drybefore mixing. The resulting paint (which should beof ordinary paint consistency) is then brushed on tothe surface. It should dry within 3o hours. Two thincoats should be sufficient. It will resist water and willnot rub off.

If you want a cheaper water -paint, dissolve so partsof glue in 90 parts of hot water. Then, using thissolution, make a cream with whiting. Use this forpainting, as you would ordinary whitewash. This willform a sort of distemper which will not rub off, butwhich will not Withstand water. Do not add any blueto the paint. It tends to give the whiting a dirty greycast.

Fixative for Colour DrawingsTS there a method of fixing or preserving theL surface of a finished " pastel painting "-say, by spraying or some such method -to preventthe picture being smudged and spoilt, yet have aflat, glossless surface which will not reflectunwanted lights ?-R. A. Smith (Bristol).

FIXATIVE liquids for spraying on to pencil, pasteland watercolour drawings are made by most firms

of artists' materials manufacturers, and may be obtainedfrom any retail dealer in these products.

You can make such a fixative liquid by dissolvingfour parts of gelatine in 96 parts of hot water. Thisliquid, when sprayed on to the paper surface, willeffectively " seal " the pastel painting or drawing, andwillnot produce a glossy surface. Increased " sealing "-power of the liquid can be obtained by making thegelatine solution stronger, but in this instance there issome risk of the paper acquiring a semi -matt finish.

Instead of gelatine, you may use a solution of fiveparts of polyvinyl acetate resin in 95 parts of isopropylacetate, but, in our opinion, the gelatine solution is asgood as any other. Please note that if the gelatinesolution is to be retained in good condition for morethan a week, it must have a few drops of clove oil orother antiseptic added to it, otherwise it will go mouldyand will become acidic.

In giving this information, we feel bound to say thatmany artists consider that fixatives have the effect of

34 NEWNES PRACTICAL MECHANICS

robbing a picture of a certain amount of its beautyand brilliance in that the highlights and the whiteslook dull afterwards. This is certainly true if thefixative solution is too strong, but with a weak solutionwe do not think that such would be the case.

Stripping Cellulose from Car BodyworkCAN you inform me if there is any rapid method

of stripping cellulose from car bodyworkpreparatory to re -spraying ?

I diave tried one brand of chemical remover,but this is not very effective, and great difficultyis experienced in neutralising it before re-spraying.-W. H. Timperley (Derby).'-j'HE reason why you found the chemical.1 -.paint-

stripper unsatisfactory for dealing with your carbodywork is that these strippers usually contain waxto retard evaporation of the solvents. Hence, afterstripping, the car bodywork would have a film of waxadhering to it. You could remove this wax film bygoing over the bodywork with a cloth charged withbenzole, after which we think that you would find thesurface quite suitable for re -spraying.

If, however, you elect not to use a proprietarypaint -stripper, you can remove the cellulose by wipingover it a cloth charged with a mixture of two partsacetone and one part amyl acetate. This may be dilutedwith about 25 per cent. of its bulk of benzole.

To be of maximum efficiency, the stripping solventsshould be " matched " to the exact type of cellulosemedium used in the original cellulosing of the body-work. You have, however, no means of knowing this.Hence, the above can only be regarded as an " average "solvent mixture, but we think that you will find it quitesatisfactory.

Preventing Colours FadingREQUIRE some means for preventing the sun

fading articles inside my windows, andwondered if there is any other system than thatof the orange Cellophane blind one sees in shopwindows.

If no other satisfactory system exists, could yougive me the name and address of the suppliersof these Cellophane blinds ?-J. A. Johnson(Penzance).IF an article is intrinsically fadeable, the only possible

way of preventing it from fading is to prevent theactinic rays of the sun from impinging on it. It is,mainly, the ultra -violet, the violet, and, to some extent,

. the blue components of sunlight which are responsiblefor the fading of colours. By filtering the sunlightthrough a yellow or an orange screen, these actinicrays are held back. Consequently, the fading does nottake place.

There is no chemical substance with which you couldtreat the glass of the window or the articles themselves.Hence, the use of some sort of light -filter, such as ayellow or orange screen, is essential.

Any of the following manufacturers of outdoorwindow and sunblinds should be able to supply yourneeds :-

Messrs. J. Avery & Co., Ltd., 8r, Great PortlandStreet, London,

Messrs. John Unite, Ltd., 295, Edgware Road;London, W.2.

Messrs. F. W. Watkins & Sons, Ltd., Sandy Lane,Camp Hill, Birmingham.

Messrs. G. Luffman & Co., Ltd., Colston Yard,Colston Street, Bristol.

If you merely want the coloured Cellophane materialitself, send your inquiry to Cellophane, Ltd., Bridgwater,Somerset.

You can obtain coloured " Perspex " sheet, whichperhaps you might find more durable, from Messrs. R.Denny, x5, Netherwood Road, London, W.14.

Varnishes for Field CoilsWISH to make some insulating varnish suitablefor impregnating the field coils of small

electric motors, and have been advised thatshellac is unsuitable due to possible acidity.Could this acidity be removed, or, alternatively,could you give me the formula for another suit-able varnish, using cellulose or some bitumencompound ?-H. W. O'Connor (Dublin).THE acidity of ordinary shellac is usually very slight,

and even a single coating of ordinary shellacvarnish will not break down under 450 volts potential.Any possible acidity in organic varnishes will notaffect any wires which are thicker than 0.02 in. diameter,and even in the case of smaller wires than this thecorrosive action seems to cease as soon as the varnishbecomes dry.

The drawbacks to shellac varnishes are (a) that theytend to absorb moisture, (b) that they are brittle.Brittleness can be decreased to a large extent by mixingin a few drops of castor oil per tablespoonful of thevarnish.

Linseed oil varnishes are good, but only the surfacedries rapidly. The inner layers remain semi -dry for avery long time afterwards.

I Bitumen varnishes are excellent as regards moistureresistance, but they tend to soften at raised temperatures.You can, however, make such a varnish by dissolving amixture of 3 parts Gilsonite and t part of medium softasphaltum in naphtha to the consistency required. Thiswill have a maximum flexibility.

I The bakelite varnishes are very good. You canobtain these from Messrs. Smith & Walton, Ltd.,Haltwhistle, Northumberland, or perhaps you may be

September -October, 1950

able to obtain particulars of the special impregnatingvarnishes direct from Bakelite, Ltd., 58, GrosvenorGardens, London, S.W.i.

It is essential to ensure that the windings are perfectlydry before applying any type of varnish, otherwise theinsulation may tend to break down owing to ionisationcaused by the entrapped moisture. A good type ofcellulose varnish is made by dissolving scrap film in amixture of equal parts of acetone and amyl acetate, Thesolution is attained by shaking the ingredients in a bottleuntil the right consistency is obtained. The solutionshould be plasticised by the addition of a teaspoonfulof castor oil per pint of the varnish.

Hot-water System'n'OR economical reasons I have to install my4- own hot-water system. Your commentson the enclosed diagram would be greatlyappreciated. In particular I would like to knowif the pipe sizes are correct, the effect of varyingsize cold -water tanks, 30, 40 or 6o gallons, andthe causes and cure of airlocks.

The cold tank is in the loft, hot tank, bath andbasin on the first floor, and boiler, gas copperand sink on the ground floor.-A. Green(Walthamstow).DOUR hot-water system layout is quite correct. The

pipe sizes are quite satisfactory, and there is noeffect on the efficiency of the system of a cold -watertank. Provided that the capacity of the tank is sufficientto fulfil the immediate demands of the hot tank andof the direct cold water demands which may be madeon it at any given moment, the working of the systemas a whole will not be influenced. In modern times,there has always been a tendency to install smaller sizesof cold tanks in preference to the 6o or more gallonlead -lined, wood -cased tanks which were formerlycommon.

In your area, keep the pipes as large a bore as possible

main supplyb."2"over flow

44"eNpansion 1/2" to /as'Pipe -441 Cistern

di

41

It

riHrf

Hob.:;*

3/4" to bathir =i7,77,1if II it

it tj

8

1/ .11

fr " k2i11;&,.

GasCopper

From main

o washX(1 bow),d(

itv2(i

I Sink I

34"

t/2

Diagram of a hot-water system (A. Green).

in order to minimise troubles arising from furring anddeposition. This precaution would not be necessaryin a soft -water district.

To discourage airlocks, make all the pipe rises asgentle as possible. This does not mean that youshould eschew vertical pipes, but always, wheneverpossible, do not have a horizontal pipe suddenly turninginto a vertical one. Make the approach to the verticalpipe as gradual as possible. When you have a straighthorizontal pipe, make it gradually rise, or graduallydescend, or else perfectly straight. Do not adopt theswitchback principle. Eliminate sharp loops, bends,or any other formation which will prevent the free flowof water, for it is at such areas (in the hot pipes) thatgases collect, furring becomes greater, and pressuredifferences' occur. Such careful construction willeliminate airlocks. If, in an existing installation, youare troubled by airlocks, search systematically for suchcauses and, having located them, put them right so faras you possibly can .by giving a better run or localcurvature to the pipe in question.

A useful book for you to study would be: " StandardPlumbing Details for Architects, Engineers, Plumbersand Students," by L. Way.

Quick -setting "Putty" for AquariumsOAN you supply me with the formula for- making a quick-settinf cement for glazingaquarium steel frames (painted) ? I understandthere is a kind of bitumen putty for this purposewhich is used by aquarium makers.

As I am likely to be glazing a large number ofaquarium frames it would be necessary for me toget this putty or cement in relatively biggerquantities than is usually sold on the market intubes or tins.-W. G. McKendry (Glasgow).THE quick -setting "putty" to which you refer is

black in colour, although when pigmented withiron oxide it is brick -red.

It is made by dissolving bitumen in any volatileorganic liquid and then by absorbing the resultingsolution into whiting.

A mixture of acetone (2 vols.) and amyl acetate (1 vol.)is a suitable solvent mixture, although a very light petro-leum oil (such as a high-grade petrol) also makesgood solvent. About 3o parts of bitumen are dissolved(by shaking) in 7o parts of solvent. The bitumen usedshould not be too hard. That which is described as" 65 penetration bitumen " (obtainable from any firmof asphalters) is about the best because it adheres well.

The putty is made by working together into a thickmass about 7o parts of common dry whiting (the whitingmust be dry) and 3o parts of a medium thick bitumensolution prepared as above. The preparation is a verymessy task when done on a small scale. Furthermore,it must be done very quickly, owing to the volatility ofthe bitumen solvents. The product must he stored intubes or else in tins with tightly -fitting lids. In thelatter containers it will not keep for very long withoutgoing hard. Note that tar and 'or bitumen -tar mixturemust not be used. Tar usually contains very poisonousconstituents which would be fatal to all aquarium life.Bitumen, on the other hand, is quite innocuous.

Painting Asbestos SheetsIWISH to paint some newly -erected asbestosA sheets. I have been told that ordinarypaint will not do. Is any pre-treatmentnecessary, or can a special paint be bought ?The job is indoors.-T. E. B. Wardle (Sark,Channel Islands).WE presume that, your asbestos sheets are of the

hard asbestos -cement variety. These have analkaline reaction, and the alkali tends to saponify theoil of the paint, thus bringing about the deteriorationof the latter. The best treatment is first of all to brushon to the asbestos sheets a to per cent. solution of glue,the solution being used hot. When this has dried off,give the sheets a thin coat of any priming paint-whitelead, red lead or grey priming paint. Over this apply athin coat of aluminium paint. Finally, apply one ortwo coats of the finishing paint of your choice. For thispurpose a cellulose paint or enamel is rather better thanan oil paint for indoor use. So far as we are aware,there are no paints formulated specially for asbestossheet work. Any good quality paint can be used forthe above purpose, but the paint must be of really goodquality.

Producing Nitrogen from AirT UNDERSTAND there is a "Brian's process"J. for the extraction of oxygen from the air.Could this method be used to supply a reasonableamount of nitrogen quickly in a small apparatus ?If so, would you tell me : What kind of apparatusis needed or what book describes it ? Is bariumoxide (baryta) easily obtained, and where can itbe bought ? Would nitrogen combine readily inthe presence of fire or heat with other substancesand produce another poisonous or explosivematerial ?-A. Littlejohns (Cobham).DARIUM oxide is readily obtainable from any-/-1 chemical supply firm, such as Messrs. Vicsons,Ltd., 548, Pinner Road, Harrow, Middlesex. It isnot poisonous, nor is it in any way dangerous to handle.It is produced in the form of a white powder. In theBrinn's process it will last quite indefinitely and willnot need renewing.

The Brinn process, however, is quite unsuitable forthe production of nitrogen. Even for the manufactureof oxygen, for which it was originally designed, it isnow obsolete. It is unsuited even for the small scaleproduction of oxygen, because it merely removes a'portion of the oxygen from the air and leaves someoxygen still remaining in the residual air, as well ascarbon dioxide and other gases; the use of this processwould not produce even an approximately pure nitrogen.We do not advise you to consider this process for nitro-gen production.

If you wish to produce a fairly pure nitrogen fromair, the following is an outline of the method

Pass a slow current of air through a wash bottlecontaining a solution of sodium hydroxide (causticsoda) to remove carbon dioxide, and then through awash bottle containing strong sulphuric acid to removemoisture from the air. The air is then passed througha 2ft. or 3ft. long glass or porcelain tube containingcopper turnings. The tube is heated to red heat. Theheated copper combines with the oxygen of the air toform copper oxide, and the removal of the oxygenfrom the air is complete, provided that the tube islong enough (2ft. minimum) and that the current ofair is not fast.

The gas issuing from the tube will now be " atmos-pheric nitrogen." It will contain about 99 per cent.of pure nitrogen-the remainder being chiefly argon,with traces of other inert gases, such as krypton, neon,xenon.

You will usually find detailed illustrations of thismethod in any textbook of inorganic chemistry, as,for example, in J. W. Mellor's " Modern InorganicChemistry " (Longmans, Green & Co.).

Gaseous nitrogen is extremely inert. It does not, asa rule, combine with anything, even at red heat. Hence,in experiments with gaseous nitrogen there is nodanger of explosion, or of the production of poisonousmaterials.

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September -October, 1950 NEWNES PRACTICAL MECHANICS 35

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All the above coil packs aredesigned for 465 kcis LF.

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36 NEWNES PRACTICAL MECHANICS September -October, 1950

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September -October, 1950 THE CYCLIST e.1

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1

Editor : F. J. CAMM

VOL. XIX SEPTEMBER -OCTOBER, 1950 No. 342

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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 MonthThe C.T.C. and Motorised BicyclesIN view of the attitude of the C.T.C.

towards dootor-assisted bicycles, whatis to happen to the hundreds of

members of this club who own them ?According to the C.T.C. they are motor-cyclists, and the fact that the machine iscapable of human propulsion does not dis-courage them from labelling it as a motor-cycle.

They further argue that no one institu-tion could defend a cyclist and a motor-cyclist involved in a collision if they wereboth members of the C.T.C. Then whatwould happen if two cyclists, members ofthe C.T.C., were in collision and eachsought the aid of the "legal department"of the C.T.C. ? It could not defend both,especially if a case against one of them wasbrought by the police.

Incidentally, we should like to know alittle more about the Legal Departmentof the C.T.C. What is the name of itsresident lawyer ? How many cases does itinvestigate each year ? In how many doesit succeed ? In how many does it fail ?In how many does it take no action becauseinvestigation shows that its members are toblame ? C.T.C. members glibly talk about"licensed libertines " (a phrase which causedus to rebuke a contemporary and its con-tributor) and " murderers," and write ofthe " callous and immoral attitude ofmotorists," and an answer to these questionswould enable us to judge whether they areentitled to presume that the motorist isalways wrong, and the cyclist is alwaysright. Investigation of road accidents byimpartial bodies, including the police, hasshown that most accidents are due to care-lessness on the part of pedestrians, cyclistsand motorists. The C.T.C. has no right,therefore, to presume that cyclists are anymore careful as road users than pedestriansor motorists, and as there are more cycliststhan motorists there must be more carelesscyclists than motorists. We also notice thatthe secretary of the C.T.C. has not answeredour very pertinent question asking him toname the statute which says: " It is notmerely common sense but the law of theland that the protection of cyclists cannotbe combined with an interest in the welfareof motorists." As the C.T.C. has a legaldepartment, which presumably approvedthe above remark which was published ina contemporary, it should not have beendifficult for him to Ideate the statute I Butthen perhaps the secretary of the C.T.C.takes a safe line of refusing to be drawn ;for he knows that he could not name such astatute, and that his argument is purebunkum. The C.T.C. is so blinded by hatethat it has developed a vocabulary ofsplenetic words which it trots out in further-ance of its self-appointed campaign of "fight-ing for cyclists' rights."

The C.T.C. should at once call for the

By F. J. C.resignation of every one of its members whoowns a motor -assisted bicycle and refund aproportion of the subscription. Whatattitude would the C.T.C. take if one ofits members was pedalling a motor -assistedbicycle and become involved in a collision ?C.T.C. members, wielding their Excalibur ofopprobrious terms, have become, as we havepointed out elsewhere, a gang of peripateticGeorge a'Green gangrels perpetually drawingattention to road accidents and the dangersof cycling instead of doing what it is paidto do, namely, encourage cycle touring-oris that its object ? As we pointed out lastmonth, the C.T.C. does not seem to knowwhat purpose it is supposed to serve, forits secretary has also stated that the chiefobject of the club is not to promote touringbut to protect cyclists. We should havethought that it was in the best interests ofthe club to confine its activities to drawingattention to the undoubted pleasures ofcycle touring instead of to the dangers of it.It gleefully announces to the world at largethe results of any case in which it hasobtained damages for one of its members.We hear nothing of the cases it loses, orthe cases it does not bring. By its irrespon-sible and reckless language the C.T.C. hasshown itself to be a body incompetent torepresent cyclists, and its latest boneless -wonder gyrations on the subject of motor -assisted bicycles show the measure of itsincompetence. When did the C.T.C. con-duct an independent investigation into thecauses of road accidents which enables itto draw the conclusion that everyone is outof step except C.T.C, Little Willie ? Itsattacks on magis-trates and coronersare largely based oninformation suppliedfrom press cuttingswhich, being abbre-viated, omit vitalevidence.

Once again weappeal to the C.T.C.to purge the AtigeanStable and to confineits attention to en-hancing the hobbyof cycle touring. Byso doing it might in-crease its member-ship, instead of sofrightening parentsthat they decline tobuy their childrenbicycles. It mightalso command therespect of the indus-try, which is by nomeans solidly be-hind it, as we havereason to know.W h e n- is thisNational Committeegoing to issue a

statement disclosing its attitude towardsmotorised bicycles ?

A Bicycle is a Carriage.SINCE the case of Corkery v. Car-

penter was decided by the DivisionalCourt in July, 195o, doubts expressed bytext -book writers are removed. It will beremembered that this case concerned acase of being drunk in charge of acarriage, the carriage in this case being abicycle. So far as the Licensing Act, 1872, isconcerned, a bicycle is a carriage. It declaresthat " Every person who is drunk while incharge on any highway of any carriage com-mits an offence," and the court has inter-preted " carriage" as including a bicycle.

Lord Chief Justice Goddard said in thecase quoted: " Since the object of thesection is the protection of the public andthe preservation of public order, the wordcarriage in it can include any sort of vehicle,certainly a vehicle capable of carrying aperson. A bicycle is a carriage because itcarries. A drunken man in charge of abicycle on the highway is dangerous whetherhe is riding the bicycle or pushing it. Ifhe is pushing he has not proper control overit and can push it into anybody or causevehicles to swerve, and he is a danger tohimself."

Lord Chief Justice Goddard need nothave gone to such lengths to argue the point,because the bicycle and tricycle becamecarriages and entitled to all the privileges ofvehicles on the public highway by virtue ofa clause in the Local Government Act of1888-the Cyclists' Charter.

The tOME_. etHUMTINJGbON

44E0,,,v -The {-amour .oad coachinqinn, its -foie galleried courtyard..

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learah ramsACV

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Castleton, Derbyshire. The great Keep of the Peak Castledating from 1176. Mani Tor, 1700 ft. dominates this

ancient village, famous for its remarkable caves.

Ninety-seven Years Young

JOHNTHOMAS, of Immingham, North

Lincs is 97, but he is still a cyclist,although -he does not ride as hard or as faras he did when he first learnt to cycle as alad of 7o. At a time when the average manhas been retired for some years, young Johnbought himself a bicycle so that he couldride a total of 22 miles a day to and fromhis work. He can't do it now, but he canmanage a few short trios now and again.The other day he kicked off at a local footballmatch, but he really doesn't have much timeto spare for sport as he is "too busy in thegarden these days."

Nine -speed CycleTHE ordinary three -speed cycle can now

have nine speeds by the attachment ofa special gear kit produced by an Americanfirm, which is of the derailleur type. Thesingle sprocket on the three -speed hub isremoved and replaced by a triple -sprocketassembly, and a second gear change lever ismounted on the crossbar. The two leversare operated in conjunction to provide anygear required for any gradient. One wouldimagine, however, that for a time the riderhas to think very carefully before he changesgear, and would often find his machine in agear which was a complete surprise to him!

Mechanised Pied Piper

BECAUSEthe so - charmingly - named

" rodent operative " employed by Rush -den (Northants) Urban District Council is

THE CYCLIST

finding it difficult to fit in allhis clients, the council is tomechanise him. He is to besupplied with a tradesman'scycle, with a capacious box inwhich to carry his traps andpoison, or maybe his lunch.So long as the local childrendon't think the rat catcher isthe " Stop Me and Buy One "man, everyone looks like beingquite satisfied-with the possibleexception of the rats.

The Two White Lines" T DO not think there' are

j" many people who knowthat," commented a member ofTowcester (Northants) RoadSafety Committee when thepolice superintendent explainedthat when two white lines on.the road, denoting three trafficlanes, converged into one singlecontinuous line, it means thatit is unwise to overtake untilthe two lines re -appear again.Several members of the com-mittee said they had neverheard of this fact and theysuggested that there should bemore publicity about it.

Leicester Speedway PresidentCOUNCILLOR HARRY

BOWERMAN, father ofAlec Bowerman, a formerLeicester Speedway motor-cyclist, has accepted the invita-tion from members of theLeicester Cycle Speedway Asso-ciation to become their presi-dent. Councillor Bowerman isa keen all-round sportsman,having for 35 years been a judgefor the Leicester Amateur Ath-letic Association, of which heis now vice-president, and hesays that if he can do anythingto help the young riders bybecoming their president he isvery pleased to do so.

Diesel -driven CyclesAGERMAN engineering company, the

Lohmann Company, of Bielefeld, hasturned to the production of a lightweightDiesel engine for attachment to bicycles, asa change from the more usual petrol engine.Weighing nib., the engine runs on anythingfrom heavy fuel oil to paraffin, and on onefilling of the gallon tank can travel toomiles. The engine simply clamps below thebottom bracket of the cycle and a frictionroller drives the rear wheel. It is only .6 h.p.but it is claimed that it gives a speed up to12 m.p.h. without difficulty and can take anynormal hill without showing signs of strain.

A Dual-purpose CycleABRIGHT inventor has thought up a

new type of cycle which can be takenin half. The front wheel is removed, com-plete with forks, handlebars and half theframe, and the rear half of the cycle is thenattached to a two -wheeled box carrier, whichcan be used for carrying anything from thebaby to the week's groceries or a sack ofcoal. A swivel coupling between the backpart of the cycle and the truck enables thetruck to be steered in the ordinary way.

Too Narrow After boo YearsHUNTINGDONSHIRE County Surveyor -

has been instructed to prepare a schemefor the widening of the 600 -year -old bridgestanding on the main road between Hunting-don and Godmanchester. The old bridge is

September -October, 1950

scheduled as an ancient monument, andalthough the roadway is to be widened to.t8ft. with 6ft. footpaths on either side, thepresent design of the bridge will be retained.The bridge was finished in the year 1332,and, no doubt, there were a few harsh wordsspoken about the foreman in charge of thejob, for while the bridge was being builtfrom both ends simultaneously someoneslipped up and the two ends did not meetproperly in the middle, which resulted inthe roadway having a permanent kink in it.

Pedal -driven " Water -cycle"WITH an eye to combining the pleasures

of cycling and bathing, an inventorhas built himself a " water -cycle " uponwhich the rider lies at full length and pedalswith his hands. - Two aluminium pontoons,about 8ft. long, are connected together bystays and support the pedals and themechanism through which a screw propelleris driven. To stop or reverse, the pedals aresimply turned backwards. The wholemachine weighs only 501b. Lubrication insea water would, however, appear to be adifficulty.

Televised Cycle HintsMR. RONALD ENGLISH, of t t, Bar-

rowby Road, Grantham, who tookpart in a ten-minute talk and televisiondemonstration to help cyclists to enjoy aday's outing, has for many years been akeen cyclist himself, and is cycling contri-butor to the " Boys' Own Paper," whoseeditor assisted the producer in preparing the -programme. Mr. English showed viewershow to prepare a cycle for a day's trip, whatto pack and the quickest and best way ofmending a puncture. A Grantham -bornman, Mr. English is a postal and telegraphofficer at Grantham Head Post Office.

Peterborough Riders Want TrackDURING Regatta Week at Peterborough,

local cyclists held their first serioustrack events, and it is hoped to hold suchevents each year during Regatta Week.Unfortunately, the city has at present nofacilities for training track cyclists, and localriders are urging that some land should bemade available for training purposes. It hasbeen suggested that, temporarily, the trackused during Regatta Week should be madeavailable for training purposes and that aproper stadium for sporting events should beprovided as soon as possible.

Efforts Show FruitDURING the last year, since there has

been police examination of cycles riddenby Chesterfield schoolchildren, a consider-able improvement in the condition of thecycles has been noticeable. Out of 5o5machines examined, 247 were in good order,and there were only minor defects in theremainder. Of the 238 cycles examined dur-ing the previous period, only 82 were foundto be in good order. Five additional schoolshave recently asked to be added to the list ofschools to be visited by the police for cyclechecks.

Grimsby Rider's National RecordRIDING in the Kesteven Aces junior 25 -

mile trial at Grantham, open to ridersunder 18, 17 -year -old Malcolm Paling, ofGrimsby Clarion Club, was first with a timeof I hr. I min. 20 secs., setting up a nationalrecord.

CYCLORAMAWe greatly regret that H. W. Eley's regu-lar feature "Cyclorama" is unavoidablyheld over, owing to the recent printing

trade dispute.

September -October, 1950

The Social Three-wheeler with dual controlreferred to on this page.

Fahting for Sahclists' Rahts

T DO not know whether that is the correct-1- pronunciation as used by the morerabid sections of the Northern cyclingpublic, and no doubt I am being very hig,but isn't it time that the C.T.C. and theother bodies ceased talking about accidentsand fahting for sahclists' rahts, and emphasisedthe great advantages of cycle touring ?Parents are not likely to be encouraged toput a bicycle in their children's Xmas stockingif they are led to believe that cycling is adangerous pastime. The C.T.C. has brokenaway from the Royal Society for the Preven-tion of Accidents because it thinks that theSociety favours drivers.

" Propaganda by the Royal Society hadencouraged leniency by spreading the ideathat victims of accidents are themselves toblame, and that it is not altogether reasonableto expect drivers to accept the responsibilityfor avoiding accidents," say the C.T.C.

They add : " The consequences of thatattitude have now reached the dimensionsof a national scandal.

" Vigorous action is called for, and theclub hope to collaborate with other like-minded organisations in a campaign torestore safety, law and justice to the roads.

" Such a campaign would be impossibleWhile we remained a member of the RoyalSociety."

The Society replied :" The assertion that the society's propa-

ganda aims at victims and not at drivers iswholly inaccurate and made without know-ledge of the facts.

" If anyone doubts our impartiality weinvite him to visit our H.Q. or our trainingcentre at Hyde Park Corner to see for himselfhow all -embracing our propaganda is."

Numbering MachinesAM- glad to know that bicycle manu-facturers are considering the suggestion

from the National Committee on Cyclingto' have the frame numbers stamped on thelug under the saddle pin. There should besome standard location for this number.It will not, of course, stop the cycle thieffrom filing it off, but it will enormously aidthe police. By the way, Sir Harold Bowden,Bart., has been re-elected president of theNational Committee on Cycling ; MajorH. R. Watling, chairman ; Mr. G. HerbertStancer, vice-chairman ; and Mr. RobertWilliamson, secretary.

THE CYCLIST c3

Around theWheelworld

By ICARUS

The Next Cycle ShowTHE 26th International Bicycle and Motor

Cycle Show will be held at Earl'sCourt in November, 1951. I am glad thatthey are not following the lead of the radiomanufacturers and holding it in Birmingham,which is quite unable to accommodate alarge influx of -visitors. As a resultattendances were poor.

50,000,000 TyresTN the five years since the war ended

50,000,000 bicycle tyres have been madeat Fort Dunlop, which is proof of the ever-increasing popularity of the modern Giant'sBoots.

Registration of Bicycles Going Abroad

H.M. Customs have accepted the specialarrangements for effecting overnight

registration of bicycles going to the Continentand machines will now be accepted, on Fridayevenings only, from 8 to to p.m. Owing tothe limited number of vans thus far equippedthe arrangement will meantime be limitedto the Newhaven -Dieppe service.

Cycle ExportsEXPORTS of the bicycle and motor-

cycle industries were £15,139,449 forthe first half of the year, Mr. H. R. Watling,director of the Manufacturers' Union, tolda conference of export managers in Coventry.The total shows an increase of £165,892over the first half of 1949.Leading buyers of motor-cycles were Australia(£1,217,o17), U.S.A.(£520,445), Canada(£357,337), and Switzerland(£300,214) ; and of bicycles,Pakistan (£875,138), Malaya(£864,944), British WestAfrica (£735,506), Eire(£507,507), Brazil (£450,647),British East Africa (k417,49I),Iran (L399,72o), and theBelgian Congo (£304,547).

Mr. Watling, who has justreturned from talks withmore than too trade andGovernment officials in Can-ada and U.S.A, took anoptimistic view of the future,particularly of the prospectsin Canada.

New Phili_dyne Twin -bulbDynamo Set

THE De Luxe type L.C.,Philidyne twin -bulb dy-

namo lighting set has just beenmarketed by Philips Electricalat ,Ct 18s. 6d. It is similarto their G.C. model exceptthat the headlamp is of thetwin -bulb type, streamlinedand chromium plated. Itaccommodates a space for abattery for use when themachine is stationary. A two-way switch is incorporatedon top of the lamp, eachswitch being in circuit with

Prof. A. M. Low, cyclist. Our contributorhas been a regular cyclist for many years.

the rear lamp. Two 6-vOlt .5 -amp. bulbsare used; while' the rear lamp of polishedaluminium has the lens prismed internallyto serve as both reflector and rear light.

Social Three-wheelerTHE photograph on this page shows a

tricycle with -side-by-side seating fortwo adults and one child. It is being madeby Paris Cycles, of London, N.I6. The driveis by three sets of pedals through chain -wheels, chains and rear sprockets to twocoaster hubs mounted in two small wheelsat the rear. Dual steering is employed. Thecost is about £48 los., not including purchasetax.

Our new Every Cyclist's Pocket Book (7s. sod. by post), reviewedon page 3o is a veritable cyclist's "bible" of facts, figures,formulae and information on all aspects of cycling. t includes

84 pages of indexed road routes.

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RAM+1,44,,C.

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Leith Hill

"elle a proael, to thetowerlow It toy Richard Hui(1766. from the tolownchis lust over 1000ft maninifieentviews are obtained over halfa do3en counties On Clearelar .

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The Veteran CyclistTHE response to these glorious

days of summer makes medelighted to be a cyclist. Thatsimple statement contains a mul-titude of actions and reactionswhich manifest themselves al-most unconsciously as I go onmy way rejoicing. It is glorious to bealive and largely that delight is enshrinedin the activity to go silently away from thecrowd and once again realise the lovelinessof this much inhabited country. Oftenenough I go lonely, for the younger genera-tion does not always approve of my gentleroaming, although it does not say so veryvigorously, but rather persuades me to hurrya little faster ; which I suppose is naturalenough, so I am becoming more and morein love with my own company unless I canfind a companion near my age and blessed-or otherwise-with my inclinations.Recently I had to go on a business trip toLampeter of all places, and took rail toHereford, ate my lunch in the Upper WyeValley, climbed Plinlimmon Pass, glanced atDevil's Bridge, and rolled quietly over thefierce little hills to Tregaran, where tea(rather late) was very refreshing, and in theevening rode miles on a golden -dusted high-way where the laburnums had spilled theirbloom, and the bird song was as glad vespersto a departing day. It was a mere incidentof a journey with a return by way ofLlandovery and Brecon: where I stayed anight, and was home again by 7.3o on thethird day. I wish that sort of thingoccurred mare often, for it would suit meadmirably to pretend I was at work andthoroughly enjoy the wandering. I haveheard people say that stretch of road fromTregaran to Lampeter is tame, and it mostassuredly can be if the mists are low andthe scenes thereby limited ; but given theright climatic setting those wide stretches oflowland with the distant encircling mountainshave a charm distinctly reminiscent ofIreland's West Coast.

Why Don't You ?THE fragrance of the hours we spend along

the road are beyond the telling. Perhapsthey carry a rarer perfume for older riders,as they certainly have more leisure in thetravel, more time to linger and make goud

THE CYCLIST September -October, 1950

all those things we missed when youngbecause of the haste and urgency informingour fitness. Why people, and especiallyolder active people, don't ride a bicycleamazes me. It is so ready for use, so in-formal, and so charged with the potentialitiesof magic, all of which are lost to the folkwho travel with noise. I have no desire tocrab anyone else's form of enjoyment,or be critical of the manner and sub-stance of their leisure, for I realisethat if we were all cyclists the way of ourgoings would be rather crowded. Yet hereis a pastime for any odd hour of time, anexercise of supreme value, and a movementthe silentest on earth. Because the pastimeis cheap in comparison with others it isastonishing it is neglected by the people wholove value for money. On that rather sordidcount, cycling is marvellous, but in its highervalues, health and individual satisfaction, itenters into the mystic realm of things thatare beyond price. Or so it seems to me, aveteran who has been riding for over sixtyyears, and is still enamoured with the game,still as thrilled at the prospect of a tour or aweek -end, and still as confident such experi-ences will bring to him the full flavour ofits delight. I am aware these are old thoughtson the subject, but in this sunshine ofsummer days they are as bright, brighterindeed because of all the polishing of years,as they were when first I went tripping

Wayside ThoughtsBy F. J. URRY

along A$ and saw the pinnacle of theBrieddens arising above the Severn flood.I go more slowly than was once the case forobvious reasons, but that I go more gaily Iam certain, and always I feel as the milesslip by and the hills draw near that the bestis still to come.

The Magic WorksTHERE is so much in this game of cycling

that is un-premeditated as it were, andthat is part of the quality making it so tempt-ing to the fairly fit man with a countrysideto fill his eyes with pleasure. The idle hours-good for us all if they are not too fre-quently indulged-need be but little less ifthey spend them aboard a bicycle, strollingrather than with the deliberate attempt atriding, through the glory of the lanes duringspring and early summer-or at any othertime as far as that goes. It happened tome one evening after tea ; I wanted to dosomething but not very strenuously, that rest-lessness which an armchair attitude on thelawn or in a car would not cure. So I tookmy bicycle up the road, intending to travela very short distance in a very long time,satisfied the exercise and change would dis-miss the doldrums and bring me home gaily.In the ultimate I rode nearly thirty miles,led quietly on by the ever-changing beautyof the devious lanes. I think it must havehappened I was almost unconscious of theriding amidst the turns and twists of theWarwickshire lanes I have known so long,until finally it became urgent to make tracksbefore the late evening caught me lampless,and that journey into the eye of the sunsetwas the culmination of a very happy inter-lude. And on the way home the thoughtstruck me that if sunsets only occured onceor twice in a lifetime how marvellous weshould deem them, and how genuine wouldbe the appreciation of their beauty. Thecrimson light flooded the land over which I

quietly rode and few people, if any, seemedto notice the metamorphosis in the mysticending of another day. These are the thingsthat connote the pleasures of cycling ; theyare ever with us if we will let them be andtheir variance and emotions are innumerable.

Why Wonder ?AFRIEND of mine connected with the

industry expressed surprise to me on arecent occasion that the modern cyclist isprepared to buy at top prices for the rightarticle. He had just marketed a certain pro-duct, more as a matter of prestige andreputation than on strict commercial lines,and had joyfully discovered the call for itamong the knowledgeable people had madehis factory exceedingly busy, and at themoment unable to meet the demand. Why isit. that the heads of the industry imagine allriders are seeking the cheapest means oftravel, have no pride in their possessions,and prefer the cheapest to the best ? Ithink the answer is to be found in the factthat all too few of them are cyclists, coupledwith the idea that no one would ride abicycle if they could possibly afford a car.Thank goodness I know dozens of fellowswho perforce have to use a car in pursuit ofbusiness, but are good cyclists whenever thechance of indulgence comes their way.Personally, I am always glad when thingshappen to prove " the impecunious cyclist,"

broadly applied to all of us, is amisnomer, and would, I think,often be nearer the mark if thedejected adjective was presentedto some motorists, judged by thecondition of their vehicles. Someof us, as cyclists, may be poor andsimple, but, believe me, we know

a good thing when we see it, and if we canstand the price we buy it.

Good MachineryDURING the last few weeks I have been

riding a " Silverthan " machine madeby the Thanet Co. (L. Cassell, of Bristol),the bicycle with the bottom bracket held inthe jointure of the down tube and seat tube,with the chain stays running underneath itand extended to the forward end of thebracket. It is a very good bicycle, slick,comfortable and lively ; in fact, as good asany machine I possess, and better than some.I ordered it in October and got delivery inJune, which suggests a busy demand for thisexpensive machine. It is, of course, equip-ped for an old rider, with t/in. tyres, a bigBrooks saddle and a four -speed Cyclo withtwist grip change giving me approximately4oin., 5oin., 6oin. and loin., quite enoughfor my comfort. The twist grip is good, andit is surprising how small is the movementneeded to click from gear to gear. What achange from the old days of the derailleur,when the late A. W. Rumney persuaded meto import a gear from France, and when adealer friend and myself had fitted it to aDawes machine, we both thought it was theugliest thing we had seen-but it worked !Louis Camillis-the managing director ofCyclo Gear, Ltd.-saw it, got my impressionon the notion, took up the French agencyhere, and later started its manufacture, anadventure which has now blossomed into afine factory turning out excellent gears. Thatstory, however, is by the way, but only goesto show that romance in industry is not yetdead. This combination of bicycle andgears will probably take me thousands ofroaming miles before thz last colours ofautumn fade, and then I shall know moreabout it ; the first impressions are good, buta thousand miles of travel is too slight adistance to claim my superlatives, and I wantto test it against my other possessions. Icertainly like the four -change Cyclo.

September -October, 1950 THE CYCLIST

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THE CYCLIST September -October, 1950

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Write for LeafletsTHE RESILION CO., LTD., 200, LIVERPOOL ROAD, LONDON, N.I

Septemligr-ctober, 1950 THE CYCLIST

for absorbing or rather damping road shocksfor many years, and they claim that theirdevice improves the efficiency of the brake's,relieves the stresses imposed upon thebicycle itself, in addition to transforming thebicycle from a jolt transmitter to a comfort-able vehicle. I support these claims.

The bicycle fitted with them is more stable onwet roads. Tyres can be inflated to a higherpressure, thus improving their life. Theycan be fitted to any make of bicycle.

The diagrams on this page show that thewheel is removed from the foras and theshock absorber is fitted in its place. Thewheel is then secured to the forward limbs.This slightly increases the. wheel base,and this improves steering as well asstability. The other diagram shows whathappens when a road shock is received on anunsprung bicycle. It will be observed that thewhole shock, sometimes of great intensity, istransmitted to the body in full over a shortperiod of, say, s second. With the shockabsorbers the initial blow, due to, say, ridinginto a pothole, is received by the rider at amuch lower intensity and it is damped cutover a longer period as shown in the right-hand part of the diagram.

It seems such an obvious item of equip-ment that one wonders why it has not beenthought of before. It certainly improves notonly riding comfort but the appearance ofthe bicycle. Four of them only weigh fib.One should not have to rely upon specialhandlebar grips and saddle springs, whichreceive the road shocks at the wrong point.'They should be damped out at their pointof generation, namely, between the road andthe wheel hub, and this is what the Palcoshock absorber so successfully does.

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A Cyclist's "Bible"EVERY CYCLIST'S POCKET BOOK

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Bicycle Measurements ; The " Gear " ofa Bicycle ; Frames ; Standard FrameAngles ; Handlebars ; Saddles ; Brakes ;Pedals ; Chains ; Chain Wheels andSprockets ; The Variable Gear Hub,Derailleur Gears ; Tyres ; Rims ; Clothesand Equipment ; Tandems ; LampsCyclometers ; Adjusting Bearings ; Re -enamelling a Bicycle ; Overhauling the:Bicycle ; Wheel Building ; CalculatingSpoke Lengths ; Summary of Cycling Law ;Touring; Touring by Numbers ; MapReading ; Road Routes Simplified ; CycleCamping ; Touring Abroad ; InterestingCycling Facts ; National Clubs and Associa-tions ; Railway and Cloakroom Charges ;

Calculating Speed from Pedal Strokes ; Tablesof Gradients ; Constants for ReckoningSpeed ; Table Showing Speeds per Hour ;Gear Table for Single -Speed Machine; BritishStandard Cycle Threads ; Cycle Thread forSpokes and Nipples; Lighting-up Variations;Road Records and Routes ; Records andStandards ; Women's Road Records ;Principal Road Routes of Great Britain ; RoadStatistics ; Bicycles in Use Throughout theWorld ; Index.

Price 7/6 net, or 7'9 by post, fromGeorge Newnes, Ltd., Tower House,Southampton Street, Strand, W.C.2.

Shock Absorbers for BicyclesNew System of Damping Out

THE bad roads, the solid tyres, the baddesign, the weight and the unwieldinessof bicycles in the early days of the

safety, set the minds of many inventors to.work on the subject of reducing road shocksto the rider. Many attempts were made tomarket devices which claimed to do this.There were spring seats, sprung front forks,leaf -spring handlebars, divided w":eel spokeswith springs between, spring tyres, and evenrubber suspension. They all failed for oneor more of a variety of reasons. The chiefof these was that they did not damp theshock at the point at which it is generated,but transmitted it almost in full to the handsand body of the rider.

To -day we have sprung saddles and rubberhandlebar grips as standard equipment, butevery cyclist knows that they do not eliminateor damp shock. Rubber handlebar gripshelp and so do saddle springs, but they arenot the complete answer, any more than thesprung cushions of a motor -car would inthemselves be sufficient. In the early daysof the motor -car, when the latter were madewithout road springs of any sort, this pointwas soon realised and so leaf -springs wereintroduced. This, however, did not com-pletely answer the problem of shockproofdriving, because it was found that the springscontinued to bounce for some seconds afterthe road shock had been imparted to them.

It was many years later that the problemwas finally solved by means of shockabsorbers so called, but which are properlydescribed as shock dampers. These takevarious forms, but they generally fall intotwo classes-frictional and hydraulic.

Surprisingly enough until comparativelyrecently bicycle manufacturers have not takenadvantage of the research which has madethe motor -car of to -day the comfortablevehicle that it is. Now, however, Palco, of221, Knightsbridge, London, S.W.7, havemarketed the Palco shock absorber at 19/6per pair for the light weight, and 27/6 perpair for the heavy duty type. Weighing onlyabout 4oz. each, and being adjustable to therider's weight, they vastly improve the com-fort of cycling, especially over rough roadsand on long tours. Apart from the comfortto the rider they prevent crystallization ofthe frame due to shock inertia, they prevent

Road Shocks-Important Advance in Bicycle DesignBy F. J. CAMM

The Palco Shock Damper, which can be fittedin a few moments to any make of bicycle.

broken spokes, protect the filaments of thebulbs, increase the life of tyres and chains,and enable one to ride more miles with lessfatigue.

They are of aircraft -alloy construction ;the front and rear absorbers are interchange-able ; they may be fitted in a few minutes byan unskilled person ; they are noiseless inaction, and are suitable for all types ofbraking. The producers of the Palco shockabsorber have been associated with devices

/00

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Shock diagrams, showing effect of unsprungbicycle compared with Palco-damped bicycle.

The Palco Shock Damper undergoing a severe test.

c8 THE CYCLIST September -October, 1950

My Point of ViewBy

beacons fieldrune II !I' 1950

A colourful and busy seenin the old high street as theriders in tite Eighth Triennial.Veterans 100mile ride slop.Tor their mid -morn inglbreak-

"WAYFARER"

Pluvius. While the cricketer or the tennisplayer disconsolately surveys a depressingscene from the platform 'of the pavilion, andwhile the exponents of. certain other pastimesdo likewise, the cycling game goes on.Enclosed in his cape (and perhaps his leg-gings); the cyclist splashes his way forward,unmindful of and indifferent to the ,sympathyof protected passers-by. It is not all " beerand skittles," but the enthusiast's pleasure inthis aspect of his chosen pastime is notsimulated. He makes the best of a " bad "job. He settles down to enjoy himself. Therain may ultimately trickle along his spinal -cord (unless he wears a sou' -wester), and hewill earn a pair of wet feet for his pains,but in 99 cases out of too he will be nonethe worse for his experience. Nay! that isa negative way of expressing the position.Rather he will be all the better, for, super-imposed on the advantages accruing fromhis exercise, there will be a feeling of satis-faction that he has triumphed over his diffi-culties and had a jolly good time in spiteof the aforesaid J.P.

The Impossible HappensWHEN visiting Warwick recently I

observed that the impossible had hap-pened. Two motor vehicles-a coach and alorry-lingered in close embrace at theintersection of two roads which wereprovided with automatic signals. Thesesignals were in perfect working ' order.How, then, did the impossible happen ?One supposes that both drivers tooka chance." Of course, one man maynot have seen the signals-it does some-times happen !-in which event he would beto blame for the collision. Normally, how-ever, it was probably a case of both partiesmaking use of the amber light, which pro-vides a " clearing " period, the man who hasjust lost the green having the right of way.Possibly, however, in the case under notice(and this very often happens), the otherparty did not bear in mind the armysergeant's oft -reiterated command: " Waitfor it!" I believe that it pays every classof wheeled road -user to implement thatinjunction.

" Rain : No Play"THESE words are all too familiar-sadly

familiar-to followers of cricket. Theyhave their significance, too, with other lead-ing outdoor pastimes; they have little signific-ance so far as cycling is concerned, for ourgreat game goes forward despite the idiosyn-crasies of the climate. A wet day presents anot always unpleasant variant of the pleasuresof our game-or is it a fine day that doesthis ? Anyhow, without making a virtue ofnecessity, we can still enjoy our frolicsawheel despite the activities of Jupiter

"Practical Mechanics" Advice Bareaa COUPONThis coupon is available until October 31st, 1950,and must be attached to all letters containingqueries, together with 3 penny stamps. Astamped, addressed envelope en sat also be enclosed.

1

Practical Mechanics September -October, 1950

Recent ReadingMAKING good use of some recent un-

expected idle moments, I have beenreading two books which appealed stronglyto me. In each case there happens to be aslight-very slight-cycling flavour, but theattraction was mainly topographical, with apersonal bias in one instance.

I am a great admirer of John, Buchan(the first Lord Tweedsmuir), a man ofwide interests and almost infinite versatility.If ever a death could be called " untimely,"it was his. In a sudden burst of hero wor-ship, I once went out of my way, on a cyclejourney, to look at his home, Elsfield Manor,near Oxford, a roadside house, which Johnloved, opening on to the village street andlooking across " some 3o miles of woods andfields to the dim ridges above Stow-on-the-Wold." Here, surely, was inspiration forsome of those exciting stories whose sceneis laid in the Cotswolds. His sister, AnnaBuchan, who normally wrote under the nameof " 0. Douglas," has given us, in " Unfor-gettable, Unforgotten," what is. at once anautobiography and a biography, which ismost readable. But almost my only justi-fication for mentioning the book here is

.because one village which figures in it ranga bell in my mind. Many childhood holidayswere spent at Broughton, near Peebles, theold home of Miss Buchan's mother.Broughton ? Surely the name meant some-thing to me ? I went off to my maps, andagain the bell clanged in my mind, becauseone July Sunday, now many years ago, Iexperienced one of my most exacting cyclerides. A friend and I, who had been attend-ing a meeting in Edinburgh, set forth forhome. Down came the rain: cold blew thewind-in July, mark you. We had a mostdifficult journey. A chance lunch atBroughton turned out to be very satisfactory,but my hands were so chilled that it wasimpossible for me to manipulate a knife andfork. So I remember Broughton-thoughthe place was in no wise to blame for myparlous condition.

The other book of which mention hasbeen made is " Green and Gold," by MaryHamilton. It was so well reviewed-though,normally, I view book reviewers and theirwork with the gravest suspicion-that I hadno hesitation in buying a copy. It is a verypleasant book to read; and to possess. It isabout an Ireland which no longer exists-anIreland dominated by " the Castle," anIreland of big houses, well populated andwell staffed, with a live hunting and socialprogramme-an Ireland containing a respect-ful, if possibly serf, tenantry, dependent foreverything on " the big house." Here is theIreland I never knew personally. It wasalready disappearing when I commenced my

. long series of cycle tours in the " Island ofthe Saints,". but it is good to read about.This, of course, is not the place to expressany views as to the merits, or otherwise, ofthe Ireland which no -longer exists, in so faras those views might cross the boundary ofparty politics. All I will say, then, is thatI was not-and unfortunately not-familiar,in person, with that joyous, careless, happy-go-lucky land, of which " Green and. Gold "provides so pleasant a series of pictures.

Good EffortALTHOUGH very disinclined to take

sides in connection with an industrialdispute, I do feel that the action of the2,50o French strikers in cycling-or, rather,as my newspaper significantly puts it," starting to cycle "-38 miles in order tohold a protest meeting is highly commend-able. We are told that " many droppedout " (serve 'em right for not keeping fit!),but it is to be hoped that the survivorsfelt all the better for their (perhaps)unwonted exercise. History does not recordhow the remnant of the 2,50o fared on theway back home-nor what proportion ofthem fell by the wayside, no doubt singingthe French equivalent of the well-knownhymn: " Here we suffer grief and pain."

No MysteryT WAS reading the other day the report-I- of an inquest on a motor -cyclist andhis wife who crashed into the rear of astationary lorry at night and were killed." The reason for the crash," stated thecoroner, " will remain a mystery." Is therereally any mystery about such an accidentas this ? I do not think so. It may be,of course, that there was no rear light, but,if we are proceeding wisely-and by " we"I mean you as a cyclist, or a motor -cyclist,or the driver of a motor vehicle-and rely-ing on our own headlighting, then this sortof accident ought not to happen. We mustlook where we are going and refrain fromgoing if we cannot see. We must rememberthat, in spite of the spate of lighting, thereare still unlighted and unlightable objectslikely to be encountered on the roads-animals, objects dropped from lorries, fallentrees, etc. And we must bear in mind thatrear lights are fickle, and that there havebeen dozens of instances, especially in thecase of lorries, of the red glow going out.Sometimes there is a crash even when thedriver is trying to make the thing workagain: All my experience cries aloud tome as to the safe way of travelling in thedark. If that way were adopted universallythe accident toll would be slashed to bits.Does it not seem worth trying ?

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