· 2019-10-23 · Africa, biltong, which is the meat of the antelope cut very thin rather like a...

www.americanradiohistory.com

January, 1953

JANUARY,1953

VOL. XXNo. 229

NEWNES PRACTICAL MECHANICS 141

PRACTICAL EDITOR

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

FAIR COMMENT By The Editor

ImportantFOUR important scientific develop-

ments have taken place since theprevious issue of this journal went

to press and they are bound, in time, tobring about important changes in thefields of electronics, power supply andlocomotion.

SOLAR ENERGYThe first relates to the use of solar

energy, concerning which a report wasrecently published by the NationalPhysical Laboratory, based on the find-ings of the Committee on the Utilisationof Solar Energy. It may come as asurprise to many to learn that there isin existence even to -day some practicalapplications of the use of solar energy.They show that we can learn somethingfrom what hitherto were considered theunenlightened races. " Alas ! the poornegro with untutored mind," wrote thepoet. Yet for a long time past they havebeen utilising, though on a small scale,solar energy for cooking. In SouthAfrica, biltong, which is the meat of theantelope cut very thin rather like a rasherof bacon, has been cooked and dried bythe heat of the sun. They also, by asimple system of lenses or collectors,make use of the .heat of the sun forlighting fires.

The committee was appointed sometime ago to investigate the possibilitiesof using solar energy and to indicatewhether research work on the subjectcould be undertaken by the Departmentof Scientific and Industrial Research.Attention was chiefly confined to directapplications of solar energy, and indirectsources of such energy, including wind-mills, were ignored. There have beenone or two projects for using solarenergy, but nothing on any considerablescale for power and heating. The greatproblem, especially in non -tropicalcountries, is the intermittence ofsunlight and the fact that least solarenergy is available when it is required.At present the cost of designing andbuilding collectors is high and thatprobably has deterred many fro mexperiments.

The committee reached the conclusionthat whilst present trends are notencouraging, and that we cannot expectto have solar energy in the immediate

Scientific Developmentsfuture, some applications may be possiblein specially favourable circumstances.It is already successfully applied to theheating of water and house heating bymeans of collectors, the cooling of airfor air conditioning by means of anammonia absorption machine, cookingon a stove by means of a mirror, theproduction of power by means of a hot-air engine, developing power by thermo-electricity, producing fuel by photo-synthesis, and one or two other minorapplications. These uses are chieflyin tropical countries. The amount ofheat from the sun reaching the earth'ssurface varies only to a small extent andaverages 1.35 kW per square metre. Ifsomeone could discover a practicablemethod of applying solar energy wecould be independent of coal.

POWER FROM THE AIRThe second important development

relates to power from the air. A companyhas been formed in France under thetitle of The National Association for theUtilisation of Aeolian Power, which reallymeans the power of the wind. Progresshas been such that experimental apparatusgives over 8o per cent. efficiency against15 per cent. of the ancient windmill.One great advantage of this new systemis that generating stations can be set upin series, whereas water turbines must bespecially adapted for each particular place.

AIR TYRES FOR LOCOMOTIVESThe third development relates to the

successful demonstration in France of theuse, of pneumatic tyres for underground

SUBSCRIPTION RATESincluding postage for one year

Inland - - - - 14s. per annum.Abroad - - - - I4s. per annum.Canada - - - - I3s. per annum.Editorial and Advertisement Office : " Practical

Mechanics," George Newnes, Ltd.,Tower House, Southampton Street, Strand, W.C.2

'Phone : Temple Bar 4363Telegrams : Newnes, Rand, London.

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

Copyright in all drawings, photographs andarticles published in " Practical Mechanics" isspecially reserved throughout the countriessignatory to the Berne Convention and theU.S.A. Reproductions or imitations of any of

these are therefore expressly forbidden.

trains. A 12,000 -mile test has just beencompleted on the Paris Metro Railway,and after the test the tyres were foundto be as good as new. The carriages runon specially prepared wooden flooringand it is stated that each tyre will lastfor 18o,000 miles. The cost of upkeep,of course, is very much smaller than withiron tyres running on the iron road ; andthe passengers travel in greater comfortand with very much less noise. TheLondon Underground is investigatingthe system. The noise of roiling stock asthe wheels pass over the expansion gapin each section of the track is considerable,and apart from noise the succession ofjolts at fairly high periodicity causesexcessive wear and crystallisation of someparts of the rolling stock.

TRANSISTORSThe fourth and probably most

important development relates to tran-sistors. The Radio Corporation ofAmerica has announced that they havesuccessfully harnessed transistors, whichare really tiny germanium crystals, andthat they now perform many of thefunctions of electron tubes- in a widerange of electronic applications such asradio, television and computors. Ademonstration was given showing themoperating an experimental televisionreceiver, radio sets, loudspeaker systems -and miniature transmitters. The, tele-vision receiver was no larger than aportable typewriter case and it made useof a 5 -in. cathode-ray tube. But for thisthere were no other tubes in the set.In other words it was valveless. Itgave excellent results and, of course,can be operated by use of a battery. Acar radio receiver employing transistorsoperated direct from a car battery with-out the usual rectifying unit and trans-former. This receiver had push-buttontuning and used II transistors. Novalves whatever were employed, and ituses only one -tenth of the current of thestandard radio receiver. R.C.A. alsodemonstrated a tiny radio transmitteremploying one transistor and a fewsimple components.

These are important developmentsquite outside the sphere of conjecture,and a great deal more will be heard ofthem in the near future.-F. J. C.


142 NEWNES PRACTICAL MECHANICS January, 1953

THE design and drawings are for themaking of an instrument of simpleform, but of such size, construction and

completeness as will enable the user. to doserious and useful work in microscopy. It ispossible to change the power of object glassesand eyepieces ; there is a revolving or rotarystage and an arrangement for taking a sub-stage and mirrors ; there is no coarse rackand pinion focal adjustment, but there is ascrew fine adjustment. The mechanicalcoarse adjustment is not really essential sincethe approximate focal position of the instru-ment in relation to the object under observa-tion can be obtained by sliding the body ofthe barrel by hand and then getting criticalsharpness by means of the milled head of afine screw.

The Optical SystemBefore describing the practical construction

of the microscope, the optical principles ofthe instrument must be dealt with, for everyuser of this magnifying system should under-stand the basic laws on which it works. Read-ers are referred to an excellent article whichappeared -in PRACTICAL MECHANICS for May,5949, under the title " Lens CalculationsMade Easy," written by Mr. J. A. Storer,B.Sc. There are one or two points relatingto lenses which are not referred to and it iswith these that it is proposed to deal.

Fig. r shows in cross-section six lenses,of which the first three, A, B and C, havethe property of bringing light rays to a focusat a point and forming a real image ; theseare known as converging lenses. In all suchlenses the point at which parallel rays meet,after passing through the lens, is called itsprincipal focus and the distance of this pointfrom the lens is its focal length. If therays proceed from a point, pass through thelens and meet again at another point, theradiant point and its image, after refrac-tion, are known as the conjugate foci. Theaxis of a lens is a right line drawn perpen-dicular to its two surfaces, as the linethrough the centre of Fig. 1.

There is a very real relationship betweenthe curvatures of lens surfaces and the result -

C

a MICROSCOPEConstructional Details of a Practical Instrument for the Student

and the Laboratory

By E. W. TWINING

ing foci and the drawing Fig. 2 illustratesthis. Parallel rays falling upon a double -convex lens are brought to a focus in thecentre of its diameter ; conversely, rays eman-ating from that point are rendered parallel.The focus of a piano -convex lens having, onone side, the same curvature as the doubleconvex, will have a focus equal to twice thatof the latter. Actually the exact distance ofthe focus from the lens will depend to someextent upon the refractive index of the glassof which it is made as well as upon curvature.A lens of crown glass will have a longer focusthan a similar one of flint glass, since theflint has a greater refracting power thancrown. For all practical purposes, however,we may consider that the principal focus,for parallel rays, of a double -convex lensis at the centre of its radius of curvature andof a piano -convex at the opposite side of thecircle. For a given radius of curvature the

Fig. 2.-Foci of double- and piano -convexlenses of equal radius.

foci of a piano -convex and a double -convexare as 2 to t.

The principal focus of a meniscus lens,as C in Fig. t, having surfaces of differ-ing curvatures may be found by multiply-ing the radius of curvature on one sideby that of the other and dividing theproduct by half the sum of the tworadii.

The refracting influencelenses D, E andF, in Fig. r, willbe the oppositeof convex; paral-lel rays whichfall upon themwill diverge, asif from a princi-pal focus which,in this case, isknown as thenegative focus.This will be, fora plano-concavelens, F, at :hediameter of thesphere of curva-ture, and for a

Fig. t (Left).-Sixdifferent forms oflenses ; A, B andC, converging, aridD, E, F, diverging.

of diverging

double -concave, E, in the centre of the sphere.Almost the only use which is made ofdiverging lenses is in conjunction with thosewhich converge the rays, as will beexplained in the following paragraph. Otherapplications of it alone are: as an eyepiecein opera glasses, for spectacles for the correc-tion of short sight, and by artists as areducing glass.

Abberations in LensesIn the construction of a microscope, either

simple or compound, the curvatures of all

Note : All measure-ments can be takenoff the scale at theright-hand side, butmost of the dimen-sions are given in the

detail drawings.

Fig. 8.-Sideelevation of thecompleted micro-scope, reproduced

half full size.

o-


January, 1953 NEWNES PRACTICAL MECHANICS

- 4YELLOW

,,iRED

4RED`YELLOW.OWE

Fig. 3.-Diagrams indicating aberration,spherical and chromatic.

the lenses are spherical ; converging lenses,however, with such curvatures have thedefect of not bringing all light rays passingthrough them to one and the same focus,each circle of rays from the axis to the cir-cumference being converged to a differentpoint. This is shown by the upper diagramin Fig. 3, where it will be seen that the mar-ginal rays, A,A, are more refracted and cometo a focus at At, nearer to the lens thanB,B, and B falls nearer than C, the centralray being the longest of all. This defect isthat known as spherical aberration, and it

LLI

1111 No i/illi!LR. I

In

11101111.)---------nn

716 4 A

45A

CA

t

results in the image of the objectviewed being rendered indistinct byall other rays than those, either centralor marginal, according to the distancefrom the object at which the lens isheld. In the microscope and the tele-scope there are two ways in whichspherical aberration can be eliminated;the first, only partially, by cuttingaway or stopping off the marginal raysand so utilising only the central andthose immediately around the centre,and second, by making the lens of twoglasses, each of different refractiveindex, one of crown glass and theother of dense flint. The resultingcombination would then be as if A,in Fig. s, were placed in juxtapositionwith D or F ; convex side of A ioconcave side of the negative lens, thelatter being the flint.

As I have said, microscope lensesare all of spherical curvature ; this isbecause, ,by reason of their small size,it is not possible to grind, polish andfigure them to any other form ; largelenses, however, can be made whichovercome the aberration and these aregiven curvatures which may be spheri-cal on one side and either elliptical orhyperbolic on the other.

There is another, quite serious, faultin all single lenses ; that is chromaticaberration, and by no alteration ofform or figure can this be corrected.Any single ray of light passingthrough any part of a lens, exceptthe optical axis, is split up into all the coloursof the spectrum, in the manner and in theorder shown in the lower drawing, Fig. 3,from which it will be seen that the blue raysare the most refrangible, that is to say, themost bent. Fortunately, by careful compu-

Fig. 4 (Above).-Sir David Brewster's handmagnifier. Fig. 7 (Left).-Longitudinal andcross -sections through the microscope, limb,

and stage.

tation and design it. is possible to combinecrown and flint glasses of such refractiveindices that both spherical and chromaticaberrations are greatly reduced and may, ata monetary price, be entirely eliminated.Examples of this complete freedom fromaberration may be found in the highest gradephotographic lenses, the photo -visual objectglasses of telescopes and in the best micro-scope objectives.

The Simple MicroscopeThe microscope in its most simple form

consists of a single lens only, which, carriedin a circular frame with a handle, is commonlyknown as a magnifying glass. Perhaps themost powerful form of such single lens isthat designed by Sir David Brewster andillustrated in section in Fig. 4. It is knownas a Coddington lense, simply because a Mr.Coddington, of Cambridge, had cne of themmade by an optician who gave it his client'sname, supposing that it had been inventedby him, though Coddington never laid claimto it, knowing, as he did, that Sir David had,

52

143

A2

Fig. 5 (Above).-The opticalprinciples of an elementarycompound microscope. Fig. 6(Right).-The optical system of

the microscope.

nine years before, publishedhis design. The form of thelens is that of a perfect sphere,with an equatorial belt groundaway to form a cylinder, andwith a deep circumferentialgroove around the centre of it. This groovehas a depth of less than half the radius ofthe sphere and, when blacked, acts as a stopor diaphragm. As a magnifier it performswell and has a large field of view. It hassometimes been used as a telescope eyepiece.The focus, for ordinary crown glass, is 3/2the radius of the sphere. It will be founda most useful accessory by the microscopistwhen walking abroad collecting specimens forexamination later under higher powers.

The Compound MicroscopeThe limit in power with P single lens is

reached and the next step is the combiningof two lenses to obtain increased magnifica-tion; this is the compound microscope which,in its elementary form, is shown in thediagram Fig. 5, where two lenses arearranged in line above an object, letteredA, B. The lens nearer the object is theobjective, and this is of short focus; theshorter it is the greater is its magnification.

A real inverted image of the object isformed at At, Bt. This image is thenviewed through the eye lens, which forms anenlarged virtual image, Az, Bz, resultingfrom the rays refracted by the eye lens andreaching the eye as if they come from pointsbelow the lens, where they would meet.Thus the final image, as seen by the eye, isthe proportion between A, B and Az,B2.

Such a system possesses all the faults ofaberration to which I have referred, and togive good definition both the objective andthe eyepiece are composed of more than onelens. An objective of low power is anachromatic combination of one crown andone flint glass, but in higher powers there areoften two, or perhaps three of such combina-tions, mounted in a cell, one above theother. The eyepiece is nearly always of theHuygenian form-invented by the famousastronomer, Professor Huygens-with two


144

piano -convex lenses, placed a distance apartequal to half the sum of their two foci, withtheir convexed sides towards the objective.Optically, these eyepieces are exactly similarto those of astronomical telescopes.

Fig. 6 represents the low -power system ofthe microscope, the construction of which Iam about to describe. The achromatic objec-tive has a focus of 32 millimetres and theeyepiece an equivalent focus of 42 mm. Inthe diagram, which is drawn to scale, 0 isthe object glass, or objective, F the field lensof the eyepiece and E the eye lens with,between E and F, a stop or diaphragm S. Thecourse of the light is shown by three raysdrawn from the centre and three from eachend of the object; these rays, if not preventedby the lens F, or the stop S, would forman image at A, A, but as they meet withthe lens F they are converged by it and,meeting at the stop, which is placed thereto cut off all extraneous light, a further mag-

-'47 B 5 F.,26rPi

f.116 -

3-3

'AMMO3.a

Fig. 9.-The tripod base, standards, and limbpivot.

nification of the image is effected by the eyelens E, precisely as if it were an originalbut larger object.

Design and ConstructionIt will be seen from Fig. 7, which shows a

vertical section through the optical centreline, through the limb and the stage, thatthe barrel of the instrument is made up ofthree tubes, one within the other. On theright-hand side they are also drawn incross-section. The innermost is the draw -tube D, by means of which the distance be-tween the objective and the eyepiece may bevaried. This slides in the second, or middle,tube M, which carries the objective at itslower end. The objective tube is carriedand slides in the outermost and, to all intentsand purposes, fixed tube F. This outer tubeis not actually a fixture, because it has asmall up-and-down movement in guides G,carried by the limb L.

The amount of this movement, a total ofhalf -an -inch, is controlled by the screw S,and is required for fine adjustment of thefocus on the object 0 under examination onthe stage ST. SB is the sub -stage bar, thepurpose of which will be apparent from thenext drawing, Fig. 8.

Velvet and Suede LiningsThree others items bearing reference letters

in Fig. 7 are the 32 mm (ilin.) objectiveOG, a 42 mm eyepiece EP, already shownin Fig. 6 (these, together, for low -powermagnification) and a 25 mm eyepiece, alsomarked EP. The linings of all the tubes,lettered V, V, are indicated by stipple. Theselinings are of black velvet, each with thepile turned inward towards the polished

NEWNES PRACTICAL MECHANICS

surface of the tube, which has to slide in it.In the innermost tube, D, the velvet is reallyonly required to form a cushion surface atthe top for the eyepiece, but as velvet is abetter non -reflector of light than even dead -black lacquer it may as well be carried rightdown to the bottom of the tube. For thelining of the outer tube, in which M willslide, use suede leather, with the suede sur-face inwards: in Fig. 7 this lining is shownsomewhat thicker. If leather is used itshould be put in not in one piece, but instrips each about half an inch wide; sixstrips, equally spaced, around the innercircumference. An alternative would bestrips of cork. If, when the leather or cork isfixed, it is found that tube M is held tootightly, the surface can be reduced by No.glasspaper, glued around a wooden mandrel.

With regard to the adhesive for stickingthe velvet and the leather or the cork to thetubes. Glue is of no use; it would become

brittle and leave the metal. The best planis to clean the tubes with a piece of nottoo fine emery cloth, leaving a scratched androughened surface. Give a single coat ofthin shellac lacquer and then two coats ofgood oil varnish, either " oak " or " copal."When the second coat is tacky, i.e., partiallydry, pass in the velvet or leather strips andpress down on to the varnish; then leave thetubes open, at both ends, for three or fourdays for the adhesive to harden.

The design and arrangement of the guidesG will be obvious from Fig. 7, but theattachment of the plate, through which theshaft of the screw S passes, may not be soclear. It is silver -soldered on the ends ofthe two dove -tailed guides which carry tubeF, and the best way to do this silver -solder-ing will be to take another piece of the sametube and drill and tap and screw on theguides and use this tube as a jig to hold theguides in an upright position, resting uponthe plates, the latter being supported hori-zontally on a piece of firebrick or asbestoscard. Then, with a blowpipe, do the silver -soldering, taking care that both guides get anequal flow of solder.

Soft solder can be used in other places onthe microscope; for instance, the rings insidethe ends of all the tubes F, M, and D canbe soft -soldered, and so can the ring intowhich the objective screws. This ring willbe a small casting, turned all over and screw -cut, in the lathe, for the objective. Thethread is lin. diameter, with a pitch of fortythreads- per inch, but obviously the objective,all the objectives, in fact, complete in their

January, 1953

cells, had better be obtained before the screw -cutting is done, so that the fit can ,,e testedas the screwing proceeds.

Objectives, Eyepieces and MagnificationBoth objectives and eyepieces can be pur-

chased from Messrs. Broadhurst, Clarksonand Co., Ltd., 63, Farringdon Road, London,E.C.I. Eyepieces cost 22s. 6d. each, and the32 mm objective is priced at 45s. Addi-tional objectives vary between this figure and£4 los., acording to the focal lengthrequired. High -power objectives are oftenmade up of three achromatic combinations,the smallest nearest to the stage, and alldead central and true on the optical axis ofthe instrument. The smallest of these maybe less than fin. diameter. The readercannot buy the bare lenses and mount themhimself, as few workers outside the opticalinstrument trade have either the tools, the

skill, the knowledge or theexperience that such mountingof lenses calls for.

As it will be of considerableinterest and importance to themicroscope user to know whatmagnification he is gettingwith his objectives and eye-pieces we are enabledthrough the courtesy ofMessrs. Broadhurst, Clarksonand Co to give the tableshown below.

The full list of objectivescovers no less than ten ofdifferent foci, giving magnifi-cations ranging from 7 to1,275, all with the three eye-pieces listed above, but certainof those whose focal lengthsare in intermediate numbers ofmillimetres are omitted. Itshould be noted that an inter-mediate of 3 mm (not listed)and the 2mm objective are foroil immersion. The user ofthe microscope is recommendedto purchase the first two eye-pieces, the 42 and the 25 mm,

and the first four objectives in the abovelist, leaving oil immersion to be acquiredlater.

Approximate magnifying powerObjectives

focallength

with eyepieces

42 mm 25 mm 17 mm

32 MM 25 45 6516 mm 62 Ito 7558 mm 775 200 2854 mm 285 490 6902 mm 530 900 1,275

To resume the making of the instrument.It may be noticed that reference has beenmade to screwcutting, in the lathe, the threadto take the objective. A much quicker wayis to bore first and then, as the workrevolves, to chase the thread with a chasingtool having teeth of 40 per inch pitch;but unless the reader is highly skilled inthe use of this tool it is far safer toscrewcut.

Referring again to Fig. 7, the limb L isa brass or gunmetal casting, as are also thedovetailed sliding guidepieces each securedby four screws, to the barrel F. The footof L is a projecting bracket which carriesthe stage ST and the sub -stage bar SB.The top face of this bracket must bemachined or filed to present a perfectly flatand true surface, square in all directionswith the guides.

Fig. 9 shows full details of the three -footed base, the two supporting brackets andthe 7/16in. diameter pivot and clamping pin.

(To he continued)


January, 1953 NEWNES PRACTICAL MECHANICS 145

OIL -BURNING UNIT FOR STOVESConverting a Slow -combustion

THE simple and practical oil -burningunit about to be described is intendedfor use in conjunction with slow

combustion stoves, small boilers, etc., andwhen fitted will enable waste sump oil ofthe motor trade to be substituted for thecoal or coke normally used, which to -dayis not only expensive but frequently difficultto obtain during the winter months. Theburlier described will enable fuel costs to becut almost to nil without any falling -off inheating efficiency. No difficulty whatevershould be encountered in obtaining plentifulsupplies of waste oil as it is accumulated byevery garage carrying out servicing, and asit is a most difficult substance to dispose of-it cannot be buried and should not bepoured into the sewers-in the majority ofcases the proprietor will be only too pleasedto dispose of it cheaply to anyone who willtake it off his hands.

Burners constructed to this pattern areparticularly suited to use in workshops,greenhouses and garages, such being theusual locations of the type of stove men-tioned, and although in point of fact theburner would function equally well fitted toa bungalow range or other enclosed type ofdomestic heater, the main difficulty herewould be in arranging a suitable positionfor the feed tank, added to which thepurring sound made by the burner whenworking would probably prove objectionable.The apparatus built by the writer was fittedto a cylindrical cast-iron stove standing 4ft.

Reservoir

Regulator

Precipitator

Od inusl- fallclear or tube

I ISupporting

bracketto

Stove or Small Boiler to Oil Fuel Burning

By W. A.

high and is in regular use for heating abuilding of some 13,000 cu. ft., where itraises the temperature much more quicklythan was possible using coke and, moreover,when once the desired degree of heat hasbeen reached it may be maintained for areduced consumption of oil with no moretrouble than just a slight adjustment of thetap, immediate control such as this beingquite impossible with solid fuel.

Preparing the StoveThe first essential to success is a good

natural draught, and where combustion isknown to be sluggish or smoke puffs backinto the building steps should be taken toremedy this state of affairs by lengtheningthe chimney pipe in order to carry it clearof the roof and any adjoining buildings. A

j16"Movement

OD BS P threads

x fi'kes' Anglesection

Fig. t (Left).-Section ofstove with burner fitted (inset detail of oilseal). Fig. 2 (Above).-Part section showingarrangement of trough, nozzle and flash -plate.

cowl should also be fitted if one is notalready in position. If coal has been inuse it would also be as well to have thechimney swept. Next the fire bars willrequire to be covered up, either with a discof sheet steel which may easily be fittedthrough the ash door if first divided in two,and then covered with an inch or so of sand,or a layer of fire -clay could be used. Thedamper should be removed and the openingfilled with either fire -clay putty or a puttymade of wet asbestos fibre, and any otherchinks in the stove should be similarlytreated, the object being to exclude all airexcept that taken in through the ash -door

via the burner, leakages else-where reducing ,the effciency ofcombustion.

Constructing 'the BurnerReference to Fig. I will show

how the burner fits into thebottom or ash -door of the stove,the door itself being lifted upout of the way, and it is themeasurements of this openingthat restrict the dimensions, ofthe burner and also, to, some

Asbestos fibre

extent, the heat generated. This latter, how-ever, will not be a disadvantage, assuming asuitable size of stove to have been installed in''the first instance, as in any event more heatwill be generated from the oil than resultedfrom the use of solid fuel.

While no exact measurements can there-fore. be given for width or height-thesevarying with different sizes and makes ofstove-in the case previously referred tothese dimensions were gin. and 4in. respec-tively-experiment has shown that theremaining measurements are more critical,those given showing the best results andshould be carefully adhered to. A clearanceof fin. all round the burner is necessaryto permit expansion. Examination of Fig.will reveal that there is only one movingpart, the choke, the purpose of which willbe evident later, along with a removablecover for cleaning purposes, and a replacableflash -plate, necessary due to the light metalused in its construction having a compara-tively short life. The bottom, sides, back,trough -front and cover are cut from mildsteel strip, fin. thick is suitable for a largeburner, while tin. would be ample in one

not wider than sin. Thesections should be cut andassembled with due regardto the proposed method ofjoining, which may be bydrilling and tapping to takelin. or 3/16in. metal -threadscrews, in which case thesides will be butted againstthe bottom and the jointscaulked in the region of thetrough. But where there isaccess to welding plantadvantage should be taken ofthis as a more rigid and oil -tight job will result, andbottom and sides should nowbe arranged corner to corner(see Fig. 3) enabling theangle so formed to be filledwith weld. After the backand trough -front have beenfastened in, suitable strips ofmetal must be secured to the

sides and bottom forming a stop to preventthe burner entering too far into the stove andalso to help exclude air. The cover plateshould now be assembled and light legs ofsuitable length attached to the end of theburner remote from the stove. The flash -plateis the next consideration and this should bebent up to the shape shown from about 18s.w.g. sheet steel, and a replacement could hemade at the same time. When fitting the flash -plate to the burner a piece of asbestos mill -board or a small quantity of asbestos stringor fibre should be inserted between it and theback, thus conserving the initial heat. Theplate is merely dropped into position with-out any permanent fixing, being held inplace by the cover. A small hole shouldbe drilled in the edge of the choke to enableit to be adjusted with a stout wire hook.

The Vaporizer and NozzleSufficient 9/16in. steel tubing, depending

on the size of the stove and the position ofthe feed -tank, should now be obtained alongwith four collars and four " T " joints. Asmall brass tap that will fit into one of thecollars will also be required. The " T "joints are used at the angles to facilitate

Split to bend

Flash - plate


146

cleaning and should be drilled and tappedB.S.F. opposite the leg of the T "

and fitted with an extra stud, so as to enablea piece of wire to be passed through eachof the tubes in the system. The tubes arenow fitted together as shown in Fig. a andfor this purpose a a B.S.P. die will be neces-sary. Two sin. holes must be drilled inthe casing of the stove, one centrally abovethe open ash -door (about 6in. above the topof the burner) and the other opposite tin.higher up. These are to accommodate the

II joints shov.:nwelded on this -

sketch

Fig. 3.-General view of burner(alternative method of assembly).

vaporiser tube. The three " T " joints con-nected to the vaporiser at the back of thestove form an oil seal and enable a lowpressure to be generated. Screwed into acollar at the bottom end of the front tubeis the nozzle, this being made from a shortlength of tube reaching from the level ofthe trough edge to the underside of the cover -plate, and is drilled right through with aseries of holes, three in each direction.

As only unfiltered oil is used in the burnerthe sediment must be removed by precipita-tion and this is achieved by fitting the deviceshown to a collar at the top of the backpipe, about a foot above the top of the stove,and removing and emptying as required.This is simply a canister attached to a shortpiece of tube which passes through its basereaching to within Sin. of the top andsecured by nuts and washers at each side.Between the upper washer and the metala second one of soft leather should be placedjust to make the job oil -tight, or alternatelythe whole could be welded together.

Arranging the BaffleIn order to prevent the burning gases from

being drawn straight up the chimney, sowasting their heat, a baffle must be con-structed of loosely placed fire-bricks-or partbricks if a small stove-in such a way thatthe flames are forced upon the vaporisingtube and against the sides of the stove beforemaking their escape. In the writer's stovethe bricks are stacked as indicated in Fig. 4and the efficiency of the arrangement isshown by the fact that within an hour oflighting the cast-iron casing can be made toglow at a bright -red heat for more thanhalf its height, and, of course, heat con-tinues to be radiated by the bricks for aconsiderable period after the oil has beenshut off.

The Oil FeedAto-gallon drum is quite suitable as a

reservoir, although any sort of tank of similarcapacity would answer equally well, and thisshould be located at a convenient point abovethe height of the stove and fitted with asuitable length of tube to reach just abovethe precipitator where it is terminated with


a small brass tap or valve with which tocontrol the oil consumption and the heatgenerated. If a convenient beam is avail-able the drum can be suspended by sheetmetal straps in a horizonal position. Thetube should project into the drum some Sin.or so as an added precaution against sludgeor water reaching the vaporiser. A hole ofsuitable size must be made at the oppositeside of the drum to the outlet to permit offilling, and probably the simplest method ofcarrying out this operation is by means

Cover ),

Inside face4rof back -plate,

Split andweld to bendto side and

back

Fig. 4 (Right).-Plan of bafflecourses.

Top row

Ek

of a stirrup -pump from a 5 -gallon drum onthe floor.

Cycle of OperationTo start the stove, first of all open the

tap and allow the oil to come level with thetop of the tube in the precipitator. A scrapof cotton waste is then placed in the troughjust beneath the nozzle and a gill of paraffinis poured into the top of the tube withinthe precipitator (here a warning against theuse of petrol should be noted, as the vapourwould inevitably be drawn into the body ofthe stove with disastrous results as soon asa light was applied) and with the coverremoved from the burner to reduce thedraught, the waste is lit. Replace the coverand close the choke right up to the nozzle,when the paraffin will burn fiercely. Nowis the time to open the oil valve again,regulating it at first to give a tail of oil

January, 1953_

about t/t6in. thick. Until the vaporiserheats up, wet oil will run from the nozzleand burn in the trough, and care should beexercised to ensure that the trough does notrun over. After about five to ten minutesit will be seen that the oil in the trough isdrying up and that a fierce flame is generatedround the nozzle, now burning completelyvaporised oil. The flame spreads to the fullwidth of the burner, following the flash -platefrom the trough up to the choke opening,whence it is sucked down and into the stoveby the force of the incoming air, hence theneed for an efficient chimney and the sealingof all chinks. At this stage the choke isfully opened (tin. gap) and the feed regulatedto provide the required heat, when the stovewill burn all day without further attentionother than the occasional removal of carbonfrom the trough with a small scraper, andeven this may not be necessary unless theoil is very dirty.

Accelerating CombustionIt should be " explained that the purpose

of the flash -plate is to accelerate combustionin the early stages ; once the burner hasbecome properly heated (550-600 deg. F.) itwould function equally well if this wereomitted. Although the cotton waste wouldburn away in time, a cleaner flame will resultif it is pushed into the body of the stovewith a piece of wire as soon as the surfaceof the oil in the trough is well alight.Maximum oil consumption in a large burnershould fall short of a gallon an hour, andfor average needs two to three hours to thegallon can be expected. Before starting upon subsequent occasions the plugs in the endsof the vaporiser and burner tubes shouldbe screwed out to enable these tubes to becleaned with a stout wire or rod, and theholes in the nozzle should be cleaned atthe same time.

Central Heating BoilersIn conclusion, it should be mentioned that

in some types of boilers, such as the " RobinHood," it will be found impracticable to passthe vaporiser through the body of theappliance, and when adapting them to useoil, the burner, which should not exceed 4in.in height, must be fitted in the lower partof a plate made to cover the ash -dooropening. A double vaporiser tube is thenarranged to pass through the upper part ofthe same plate, the oil seal being fitted atthe side of the burner. Where the heightof the ash opening is insufficient to accom-modate both burner and tubes, the latterwould have to be arranged in a separateplate fitted to the upper opening and directeddownwards towards the flames inside theboiler.

-------------- BOOKS FORBy F. J.

Screw Thread Tables, 51-, by post 513.Refresher Course in Mathematics, 816,

by post 91-.Gears and Gear Cutting, 61-, by post 616.

Workshop Calculations, Tables andFormula, 61-, by post 616.

Dictionary of Metals and Alloys, 1016,by post 111-.

Wire and Wire Gauges (Vest PocketBook), 316, by post 319.

Newnes Metric and Decimal Tables, 316,by post 319.

ENGINEERS --------------,CAMM

Practical Mechanics Handbook, 12/6, bypost 13/-.

Screw Thread Manual, 6/-, by post 616.Slide -rule Manual, 51-, by post 513.Mathematical Tables and Formula, 5/-,

by post 513.Every Cyclist's Pocket Book, 7/6, by post

7/10.

Published by

GEORGE NEWNES, LTD., TOWER HOUSE,SOUTHAMPTON STREET, STRAND, W.C.2



An Electric Floor PolisherConstructional Details of an Inexpensive Appliance for Home Use

By E, G. H.

The completed floor polisher ready for use. -

THE machine described below wasoriginally made for polishing the sawdustcomposition floors which are being

extensively used in these times of timbershortage. It will, however, give a highpolish to linoleum, parquet, etc.

Although the machine is similar outwardlyto some commercially made polishers, thedetails are modified to enable it to be easilyproduced in the amateur's workshop. A3iin. lathe will cope with all the turning,which is quite straightforward.

The machine is purely for polishing, theapplication of polish being by hand.

Rubber draught excluderfixed to edge vasSteel plate toof board toprotectturni

II

44Pact

ir44

6frkentres

'Pathos

-4

these dimensions3' securedis I underneath

t-- 4Hole to a,clearmotorpulley

/2"CentresDrilled to receive mounting

studsDural plate with 4 -'Whit. screws passing

through to steel plate underneath

-712

When adjusting beltkeep thisclearance as J Press studssmall 83 on J"pitchpossible circle

Pad carriercarrier as inFig #

Fig. 3 (Above).-Plan of base layout.Fig. 8 (Below).-Underside of base showing

the path of the vee belt.

3ift. 8in. x aft. Sin.

18 '

loin. x Sin.zyd.

coin. x sin.zft. x 8in.

3393

i3itydi sq.

General ArrangementThe appliance consists of a motor mounted

vertically over a triangular plywood board,and driving on the underside three ball -bearing pad carriers by vee belt. The driveis so arranged as to rotate the front padcarrier in the reverse direction to the othertwo. Detachable felt polishing pads take theplace of the conventional (and expensive)rotary brushes. A tubular handle is hingedto the two lower motor feet, and carries an" on -off " switch in a convenient position.

Spindle and covermachined back tosui t thrust race

07

End cover

Bronzebush

The MotorThis is a h.p. induction motor running at

5,425 r.p.m. It should be noted that as thisunit is mounted vertically there will be anappreciable end thrust on its lower bearingdue to the weight of the rotor. A ball -bearingmotor will support this weight withouttrouble, but should the reader have a motorwith bronze bush bearings trouble mightdevelop due to the shoulder of the rotorspindle sinking into the end of the bush.However, a motor of this type can be used

Fig. a (Left).-Spindlethodification withSingle thrust bearing.

Steel washer presserin recess andbored to clear

shett,

I ICombiner/thrust race

Fig. 2 (Right).-With angular con-

tact hearing.

The tee handle is large enough to give com-plete control over the machine when in use.

The following details need not be strictlyadhered to as the reader may have similarcomponents or materials to hand which hewishes to utilise.

The machine described, however, hasbeen found to be the most satisfactory ofseveral types constructed, and has given thewriter trouble -free service over the pastthree years.

s's efiffrdh.1162

Felt- dustexcluder

quite satisfactorily by modifying the lowerbearing in either of the ways shown inFigs. t and 2.

Modified BearingsWhich method to use will depend on the

design of the end cover. Some types have acompartment surrounding the actual bearingand containing an oil -soaked worsted packing.Reference to the table of race diameters givenbelow in conjunction with the spindle sizes

MATERIALS REQUIRED

Amount or No.Required

Iift. 6in.

f h.p. motor suited to mains supply5 amp. " micro break " switch3 -pin plug to suit supply pointfin. conduitfin. 3 -way junction box

2fin. brass bushes

eft. 6in. 'in. O.D. cycle tubingfin. gas socket .

ift. 6in. 'fin. x fin. fiat mild steel "2 fin. bore rubber grommets

6in. fin. x r/r6in. spring steel , clip.ift. 6in. fin. round mild steel (bright pivot.

t f t. fin, x fin. flat mild steel , bracket.fin. x sin. hexgonal bolts Bracket bolts.fin. plywood Base.fin. x sin. B.S.F. round -head steel screwsI& g. dural or aluminium 7, (slots).Rubber draught excluder protector:fin. mild steel plate " (a djus tment).fin. hard fibre or seasoned plywood Pad carriers.fin. x sin. Whitworth set screwsfin. Whitworth hexagonal nutsfin. flat washersI fin. fin. bore ball races (Hoffmann No. LS7)

press studs Pads.3/'6in. art felt2..4.in. x fin. vee pulley (bore to suit motor) DriveSin. vee belt (54in. approximately)ufficient rubber 3 -core flex.

Sundry washers, screws, etc.

Use

Handle-


148 NEWNES PRACTICAL MECHANICS

will enable the reader to determine if thehousing can stand boring out to carry an" angular contact " single -row bearing.

If the foregoing method is decided upon,set up the end cover in the 4 -jaw chucktrue to the register, and bore out a tight pushfit for the race as shown in Fig. 2. Therotor spindle should also be machined to be atap fit in the bore of the race, care being takento form the shoulder to bring the rotor intoits original position. Before assembly therace may be lightly packed with soft grease.A flat washer, bored to clear the spindleand pressed into a counterbore above thebearing, will protect the race from grit anddust and help retain the grease.

The alternative method is to still use thebronze bush, but to take the rotor weight ona single thrust bearing. Again the end covershould be set up in the lathe true to theregister, but in this case only faced back toaccommodate the race. To a void reducingthe length of the bush too drastically, theshoulder on the spindle may also be machinedback. Here again care should be taken to

1/2Flef washersOuter race secured by

/Alf let washer as shown

uir 46,

kin. mild steel, whichprovide belt adjustment, aredrilled and tapped din.B.S.F. and secured to theunderside of the board byround -head steel screws.The aluminium pieces sur-rounding the adjustmentslots add to the appearanceof the machine and alsoprevent the screw heads fromsinking into the wood.

A' length of mouldedrubber draught exchider issecured to' the edge of themotor board by suitablelarge headed nails andprevents woodwork, etc.,from being damaged if incontact with the machine.

The motor itself is mount-ed on the board by fourspecial studs (Fig. 7), whichtake the place of theend cover securing crews (or nuts).

Head of 21'1104:set screwshouldered down tO be push fit

in inner race

/ 77 Aft Zj''I. ADM Mir#1ff, 11

Recess to keep -T press studsMin clear of floor

Dural Belt tensionadjustmentsheet Slotted plate

Felt polishing padsretained by carpet press studs

-Te Includedangle

Rubber draughtexcluder round edgeof board to protectskirting etc: '

ml

The

Felt cushion glued to face of pad carrier

Figs. 4 and 5.-Sectional views giving details of pad carrier bearing and arrangement ofmotor and rear pad carriers.

ensure that the rotor is brought into itsoriginal position.

The Motor BoardThis is a piece of tin. plywood 'shaped as

shown in Fig. 3. The three slotted plates, of

Fig. 7.-Detail of motor and lower end ofhandle.

Dimensions of Hoffmann Angular ContactBearings

Bore Outside Diam. Widthi in. i 5/t6in. in.sin. I 9/16in. 7/16in.i!ri. t "Alin. 9/16in.

No.LS 5 ACLS 7 ACLS 8 AC

Dimensions of Hoffmann Single ThrustBearings

No. Bore Outside Diam. WidthW gin. in. I 9/32in. sin.W 9/16in. 9/16in. I 13/32in. tin.W tin. tin. 1 13/32in. tin.W din. tin. I 17/32in. tin.

size of these studs will, of course, vary withthe make of motor.

The Polishing Pad CarriersThese are made from tin. hard fibre or

seasoned plywood to the dimensions given inFig. 4. It will be seen that the front carrier isvee grooved, but the two rear ones aremachined to take the back of a standard gin.vee belt. The belt is fitted round the motorpulley and pad carriers as shown in Fig. 8.On the original machine the length of veebelt required was 54in., but slight variationsin diameter of pulleys, depths of grooves,etc., may necessitate a belt of different length.

The ball races used are the plain singlerow type of a suitable size. Those used bythe writer were Hoffmann LS 7, which havethe same dimensions as the LS 7 A.C. raceshown in the table. The races should project1/64in. above the pad carrier to enablethe securing washer to pinch the outer track.

The carriers are part covered on the under-side with felt to provide some degree ofresilieitcy when polishing uneven surfaces.A proprietary adhesive may be used, but

January, 1953

Close-up view of the polisher.

carpenters' glue has given no trouble on thewriter's machine. The pads are of art felt(about 3/16in. thick) and should be 4in.larger in diameter than their carriers. Theyare secured by three carpet press studs suchas are used in car upholstery. It is suggestedthat at least three sets of pads be made fornormal usage.

The HandleThis is quite straightforward, and here

again the details need not be strictly adheredto. On no account, however, should the teehandle be replaced by the " vacuum cleanertype or difficulty may be experienced in con-trolling the machine.

The stem of the handle is tin. O.D. steelcycle tubing, brazed at the upper end to a three-way junction box, which has been shouldereddown to receive it, and at the lower end intoa bored out -sin. gas socket brazed to theyoke (Fig. 6). Two din. lengths of lin.conduit screwed at both ends and two bushescomplete the handle. A 5 amp. " micro -break " switch (contacts of which are heavierthan the ordinary type) is fitted to the junctionbox. The three -core flex is now threadedthrough a grommet fixed in the back of thebox and the live side cut and taken into theswitch. The earth wire should be bared fora length of tin. and looped under the head ofa 2 B.A. brass screw and washer tapped intothe inside of the box. The flex may now be

(Continued on page 169)

Fig. 6 . -Front andside views of

handle.

Grommetfor cable

Cleats'/for cablewhen notin use



Auxt iary Engine Units forPedal Cycles

The Power Pak unit with synchromatic drive.

THE display of auxiliary motor units, or" clip-ons ' as they have come to becalled, was more comprehensive than

ever at the Earls Court cycle show this year.

The "Cyclaid "On Stand No. 148 the British Salmson

company were displaying the " Cyclaid," abelt -driven unit fitting directly over the rearwheel. The " V " belt of rubber textureoperates from a pulley on the engine to a rimsecurely bolted to the rear wheel spokes.

The unit, a 2 -stroke of 31c.c., has a com-pression ratio of / : 5.6. The cylinder is analuminium casting with a steel liner withdetachable head. Extension hub bolts andnuts are supplied with the unit, and theseare hollowed to take a 3-speecl, cable if neces-sary. Throttle control is of the twist griptype and should be fitted on the right sideof the handlebars, and the decompressor onthe left. The motor support is adjustableto take various sizes of wheels. The unit ismade by British Salmson Aero Engines Ltd.,76, Victoria Street, S.W.I.- The retail priceis £24 complete.

" Cyclemaster "The very popular " Cyclemaster " on

Stand No. 140 has been improved by increas-ing the capacity to 32 c.c., and incorporatinga coil in the dynamo for lighting purposes.

The Cyclaid bah -driven unit.

A Review of Some of the Latest Models Shown at the RecentCycle Show at Earls Court By R. L. JEFFERSON

This unit is supplied as a built-up wheelcomplete with tyre and tube, the rim beingof extra'heavy gauge. The braking is of theback-pedalling hub type with positive action.Although the capacity of 32 c.c. may seemsmall the makers claim a performance equalto many larger engines due to the advanceddesign of the inlet valve. Drive is throughchains and an oil -bath clutch, this latter

Showing the compact arrangement of the

enabling the engine to be kept running whenthe cycle is at rest. Lighting and ignitionare built in and consist of the Wipac unit.The complete unit retails for £27 tos. andis guaranteed for six months.

On Stand No. 5o Britax (London) dis-played a new and novel unit, The " LohmanMotor." This is of the compression ignitiontype and, of course, dispenses with sparkingplug, magneto and carburettor. The unitis *fitted unobtrusively below the bottombracket, and transmission is by a roller ofeasily adjustable type ; it is claimed to benon -slipping.

The capacity is 18 c.c. with bore and strokeof 28 mm. and 3o mm. The engine achieves.75 b.h.p. at 6,000 r.p.m. The fuel con-sumption is given as 35o m.p.g., and theweight is II lb., which latter is an amazingfigure for such a performance. The price is24 guineas.

The " Cucciolo "Britax also displayed the Ducati " Cuc-

ciolo " (" Little Pup "). This little unit hasseveral very distinctive features. It is a48 c.c. four-stroke with overhead valves, and

Cyclemaster.

has a two -speed pre -selector gearbox. Thedrive to the rear wheel is direct by chain,lighting current is supplied by separate L/Tcoil. The positioning of the unit at thebottom brackets makes for stability. Theengine develops 1.25 b.h.p. at 5,250 r.p.m.Lubrication is, of course, indepedent and fullyautomatic. The machine is a first-classexample of Italian workmanship. The price

complete is £40, and H.P.terms are available. Theaddress is Britax(London), Ltd., 115-129,Carlton Vale, N.W.6.

The " Mosquito "Mosquito Motors Ltd.,

Moorfields, Liverpool, 2,were showing their wellknown units and also acomplete cycle. Thislatter has been speciallybuilt to take the unit.Seat tube length is 2t in.and all tubes are of heavygauge, as are the chainstays. On this model thestandard fork is a heavyduty type with largediameter ball bearings. Aspring fork can be sup-plied for an extra £4.Braking is by Perrycoaster hub to the rearwheel ; the front brake isa heavy duty stirrup type.When spring forks arefitted the control is bycable. The equipmenton this cycle includespump, toolbag and tools,taxholder and bulb horn.The panniers in the illus-tration are an extra at59s. 6d.

The " Mini -Motor "Trojans were occupying Stand No. 149

and were showing the new Mini -Motor MarkIII, which has been reduced in price to£18 ifis. od. There are several detailimprovements; an entirely new lever enablesthe engine unit to be raised clear of thetyre or lowered into contact with it. The

The Cucciolo four-stroke unit with overheadvalves.



An exploded view of the Power Pak unit.

engine is a 49 c.c. 2 -stroke. The tank, whichhas a capacity of I of a gallon, is rigidlyattached to a chassis of new design; theelecompressor is in conjunction with thethrottle level to facilitate starting.

from last year's model. The price has beenreduced to £19 19s. od.

The "Mobylette"This firm also distribute the Mobylette

autocycle of 49 c.c., the price of this hasbeen reduced to £39, plus £m 16s. 8d. pur-chase tax.

The machine which really took my eye onthis stand was the super de -luxe model at£69 12s. sod. This machine has a clutch andinternal expanding rear hub brake, theframe has twin top tubes_ which are bracedat the junction of the seat tube, and continuethrough to the rear fork -ends. The downtube of substantial diameter is slightlycurved to accommodate the engine. Thetransmission by chain is 'lin. by .305. Igni-tion and lighting are from the flywheelmagneto. The tyres are oversize balloonsin white rubber, and brake levers are of theinverted type. The capacity of this modelis the same as the standard model. Tele-draulic forks of neat design completed avery attractive machine.

The "Power Pak"The popular Power Pak was on Stand No.

74 at the reduced price of £25 4s. od. Thedistributors, Sinclair Goddard and Co., 162,

The " Mobylette" unit has

Trojans have special easy terms of only£2 down, the balance can be spread overnine months. There is a fitting charge of15s., tax, insurance, etc., bring the amountup to approximately £5 sos. od. Theaddress is Mini -Motor (Great Britain) Ltd.,Trojan Way, Croydon, Surrey.

On Stand 111 Motor Imports Co. wereshowing the front wheel drive " Berini."This company have taken over the distribu-tion of this unit which remains unchanged

he Mini -Motor, which is a friction -drive onthe back wheel.

several distinctive features.

Queensway, W.2, were also showing animproved model at £27 6s. od.

This model incorporates synchromaticdrive of self -engaging type with single plateclutch starting, stopping and clutch operation

The front -wheel drive Berini unit.

The VeloSolex with the engine mounted overthe front wheel.

are automatically controlled from a singlelever.

Both the standard and improved models areof 49 c.c. They are supplied with magdyno,anti -splash guards and a Power Pak pennant.

It should not be forgotten that theDunlop " Motorette " tyre was evolved incollaboration with the Power Pak experi-mental staff.

"VeloSolex "A frame of advanced design was that of

the VeloSolex, which is of the open swanneck type built up in four units to facilitatereplacement should the need arise.

The engine, which is a two-stroke 3 -portof 45 c.c., with bore and stroke of 38 mm.and 4o mm. develops .4 h.p. at 2,000 r.p.m. ;the carburettor is of the floatless type fedby a Solex fuel pump. The engine is coilsprung and rubber suspended. Drive is byroller from the ballraced crankshaft. Thismachine, a complete autocycle, has a dryweight of 6olb.; the price is £37 los. od.,plus £m 8s. 4d. purchase tax.

The 1949 Cycle Show was conspicuousfor the absence of these little units, but atthe 1951 show there were ten firms displayingthem. This year there were even more. Allhave been improved, some very greatly, andmany have been reduced in price.

The answer to the dismal prophets whocalled them a flash in the pan is the numberone sees on the roads of nearly every countryof the world.

Showing the panniers fitted to Mosquitomotor -driven cycles.



The Armament of Ship ModelsWith Particular Reference to Models of Old-time Vessels

MANY builders of " period " shipmodels, unless they are working toa really authentic plan (of which

there are lamentably few) tend to over -armtheir vessels, both as to the number of gunsand their size. A small galleon under sail,displaying what appear to be about fiftybeer -bottle necks on each side, may, or maynot, be decorative ; but it is certainly notaccurate.

The average period model of about 3ft.

Two types of carriage

Making wreath ports

By R. K. BATTSON

a short distance, and paint with finely -groundbrass paint, or black to which a little brownhas been added ; the latter for bronze oriron guns.

Carriages can be built up from thin wood(two side pieces and a floor), the sides beingnotched for the trunnions, and cap hingesadded in thin card. Four slices of dowel

Breech,ng gear

Run -out tackle -

. Tram tackle

Swivel gun

Fig. I.-Component pans and tackles for old-time cannon.

in length, is approximately AM. scale ; andan upper -deck gun in this scale is only Sin.long overall, including the carriage, so itwill be seen that some restraint is called for.Commercial firms mostly offer guns whichare quite the wrong shape, and grossly over-size for all but a really huge model. So itis better (and less expensive) to make one'sown.

It should be noted that, except whenactually about to fight, a ship's guns wererun in, and, under sail, most of the portlidsclosed, so that it is neither necessary nordesirable to display serried ranks of grinningmuzzles. Not too much notice should betaken of old ship pictures in this respect;the artists were rarely seamen (as their pecu-liar ideas on sails and rigging disclose) andthey loved the mass display of impossiblylarge cannon.

Making. CannonOwners of lathes will, of course, need no

advice from me to turn their guns in brass,but less fortunate folk can get by very nicelywith fine dowel rod. This should be slightlytapered towards the muzzle, and the reinforc-ing rings represented by narrow strips ofglued paper wound neatly in place. A pieceof stout wire passed theough a previously -drilled hole will represent the trunnions, anda pin, driven up to its head in the breechend, the cascabel. Bore out the barrel for

rod will provide the trucks (wheels), and canbe glued in place, and a small elevating wedgeinserted under the breech end of the barrel.

Later developments of the carriage werebuilt up of separate timbers instead of havinga solid floor.

Where the scale permits, some attemptshould be made to show the breeching gear,run -out and train tackles, but in the normalAin. scale, the blocks for these purchaseswould be about the size of a carroway seedand, rather than fit over -scale gear, it is muchbetter omitted.

In a solid hull, lower and between -deckguns, where only the muzzle portion is visi-ble, can be mounted on plain block carriages,inserted in a morticed hole, somewhat largerthan the gunport, cut in the hull before theside and bulwark pieces are pinned in place.

In some of the elaborately -decorated shipsof the i7th and 18th centuries, carvedwreath -ports were fitted. These can beworked up either in plastic wood, or, betterby first shaping a round stick of wood tothe outside diameter of the wreath, and thenboring out the middle to the interior diameter,to the depth of an inch or so. The edgeis then rounded and lightly carved, eitherwith a small file or carving chisels, and thinslices cut off (being careful not to break thepiece across the short grain), glued to thehull over the gun -port proper, and gilded ;when two or three slices have been cut fromthe stick, it can be bored deeper.

Small swivel -cannon can have their barrelsmade as described, the handle being formedfrom a pin bent at right -angles, and thewhole mounted in a soldered -up wire crotchfitted in the bulwarks.

Eighteenth -century carronades were alto-gether shorter and fatter than the gun ; insome forms, they were mounted on slidesinstead of carriages, with screw elevatinggear. The slide carriage pivoted at one end,the other running on the deck on rollers toprovide a training arc.

Modern ArmamentModern turret guns are quite straightfor---tempi

Blast bags on old -type turret

Blast screens on forecastle superstructureForecastle breaswater

Fig. 2.-Modern types of Naval armament.

Old patternA A. gun



ward, and can be arranged to elevate ifdesired by drilling right through guns andturret at the breech end and mounting onstout wire which is a tight fit for the holes,and the ends of which are nipped off andfiled flush with the turret sides. The older.pattern guns had white canvas covers (calledblast bags) fitted at the point of entry intothe turret, and these can be worked up inplastic wood or putty, to hang in realisticfolds, and are then painted white.

Old pattern A.A. guns and destroyer guns,the former with all their works exposed, andthe latter fitted only with splinter shields,are rather more difficult, especially in small

scales. It is usually sufficient, however, toshape the barrels with a file, solder on therecoil cylinders and run -out boxes, and addsmall trimmings, such as breech -mechanismlevers and training handles, in fine wire,which can be quite safely glued in place.Dial sights can be made from thin cardstamped out on an office punch and paintedbrass. Splinter shields can also be shapedfrom thin card, creased at the angles andglued on.

Pedestals can be worked up in wood fromsolid, and, if the scale allows, can permitboth training and elevation. But, as ageneral principle it seems best, in small-

scale work, to fix everything down once andfor all ; delicate working fittings are all -too -ready victims,to the ham-fisted admirer.

The chief thing, when trying to makewood look like metal, is to get a superfinefinish before painting ; and to be extremelyparticular about metallic paints. Some" brass " paint appears to consist of brassfilings mixed with treacle and will ruin asmall model gun. If you cannot get reallyfinely -ground brass paint, use artist's gold,and subsequently varnish it, which willslightly yellow the finish and look much moreconvincing.

A Cricket Score BoardThis Design was Submitted in Response to a Request Published in Our "Letters from Readers"

Page in the September, 1952, Issue

THE drawings give a good idea of thesystem used and, as will be seen, bothnumbers hung on hooks and numbers

on an endless belt showing through aper-tures in the board are used. The tens andunit figures of the batsmen's scores and thetens and unit figures of the total are regis-tered by means of the belts and the others areindicated by means of plates hung on hooks.These plates may either hang on the frontof the board or at the rear and show throughapertures cut for the purpose.

The BandThis is an endless belt of stout black linen,

or canvas, on which the numbers are painted.As the operator pulls in the direction ofthe arrow (Fig. 2) the successive numbersappear in the appropriate window. In orderto register the numbers accurately a whiteline is painted horizontally across the backof the board and corresponding numbers ona white line on the inside of the band: thus

Last -

.14

Total

011111

Ba "ea 11111

Bowlers

Last player

El

wicket -

Opponent's score

By J. B. CHANNON

at the position shown in Fig. 3 the numbershould bT visible at the window.

3

The Roller SupportsThese differ slightly. The slots in

supports (A) slope slightly downwardstowards the board so that, when the spindleof the roller is placed in them, it falls tobring the roller close to the board.Supports (B) have vertical slots long enoughto allow the rollers to hang freely and sokeep the band taut (see Fig. 3). The bandis kept close to the window by metal rodsabove and below the opening, free to turnin holes drilled in L-shaped brackets. Eachband requires two rods.

Using a BoxIf a box is required rather than a board,

a rectangular opening may be made in theboard, as indicated by dotted lines Fig. I,

Figs. I and 2 (left).-Frontand side views of the pro-

posed score board.

and the various screws onwhich plates are hungarranged so as to beaccessible from this open-ing. Alternatively, win-dows could be cut forthem and the plates hunginside the box, possibly ondoors hinged to fit thewindows or on screws.

For a box the bandscould' be run horizontallyacross the roof, with suit-able modification of sup-ports and rods ; thiswould allow a neaterspacing of the othernumber plates.

MaterialsNo dimensions are sug-

gested : the builder canplease himself accordingto the materials available.A board can be made of" hardboard," well weath-erproofed, attached to arectangular frame of stouttimber, and its legs well

Support at A(wood)

Support- at B(wood)

Screw to Rods free to turnback of in brackets

board Plan of roller in supports

Fig. 3.-Details ofband and roller

fittings. Osunk into the ground. This should notrequire staying unless the situation is a verywindy one.

OperatorsTwo operators are almost essential: each

scores for his own man and does his appro-priate share of the " totals " band. Theywill have to settle " extras " betIveen them.

Remember-the more the information dis-played, the less likely is the spectator to beable to understand it.

lust Published

WORKSHOP CALCULATIONSTABLES AND FORMULAE

Tenth Editionby F. J. CAMM

A handbook dealing with methods of calculation,solution to workshop problems, and the rulesand formulae necessary in various workshop pro-cesses. It contains all the information a mechanic

normally requires.From all booksellers, 716 net,by post 8/- from the publisher,

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


January, 1953. NEWNES PRACTICAL, MECHANICS 153

Fig. 2.-Perspec-tive view of thecompleted clothes-airing and drying

cabinet.

THE drying and airing of the washingassociated with a new addition to thefamily can be an embarrassment to

those living in restricted accommodation,particularly in wet weather, and this dryingcabinet was designed and built with thisproblem in mind. It was designed so thatit could be folded into as little storage spaceas possible, while, when opened for use,providing some so, cubic feet or so of dryingcapacity. The drier was built in two mainsections (Fig. which would foldflat, but which could be opened out to forma rectangular cabinet approximately 2ft. by2ft. by 3ft. high.

FrameworksFour wooden frameworks are first con-

structed from s lin. by s lin. timber and jin.dowel as shown in Figs. 3 and 4. The simplejoint shown in Fig. 5 was used and has provedquite satisfactory, but those with greaterwoodworking ability may prefer to use a jointof their own preference. The frames arecovered on the outside with plywood, hard-board or thick cardboard as whim or pursedictates, a spice of tin. or so being left at thebottom of the frames to allow air circulation.Slots are cut in the frame members in positionsshown in Figs. 3 and 4, those in the top

A Clothes -airingand Drying Cabinet

Constructional Details of a Useful Folding Appliance forBy " HANDYMAN "Domestic Use

members (Figs. 4 and 6) being to support thetop grid on which the clothes are hung, andthose in the vertical members (Figs. 3 and 7)being to carry the same grid when the drieris packed away. The frames are hinged intwo pairs, which, when erecting the drier foruse, are opened at 90 deg. and stood togetherto form the rectangular cabinet. Hooks andeyes on the abutting members serve the dualpurpose of holding the two parts together whenerected and holding the folded sections in thefolded position when packed away.

L

Fig. 1.-The two main sections of the

Grid ConstructionThe grid on which the clothes are hung

(Fig. 8) drops into the slots provided in thetop members and also serves to keep thestructure square and rigid. It is made bycutting accurately to length nine pieces oftin. dowel 231in. long and two pieces 251in.long. Two strips of wood 221in. long byijin. wide by lin. thick (ply is suitable) arecut and dressed and the dowel centres markedoff. A tin. auger bit is used to bore half -way

V ,8 B 4,itt.\C

24

C

I P4elli;

25'2

-

,4,4

- ---3

-r. -..., Slot-C C il

710owel C

"

_Ye

through the strip, the point of the bit makinga small hole right through which is used forinsertion of a small screw. The short boredsection and the screw provide sufficient endsupport for the dowels, but a small spot ofglue can be placed on the dowel end beforescrewing up. It is, however, important tobear in mind that this part of the apparatuswill get warm and that contact between warmglue and baby's clothes is not likely to meetwith general approval. The two longerdowels pass right through the side strips and

project about in.each side. Theseprojections slip intoslots B, Figs. 3and 4. Fig. 8 showsthe dimensions of thegrid, and Fig. 9 theenlarged detail of thedowel end support.

The heating ele-ment calls for thegreatest care in con-struction. Two prin-cipal requirementsmust be met : (a) theapparatus must beelectrically safe, and(b) there must be norisk of fire or damageof any degree byover -heating of theclothes being driedFig'. so shows theconstruction adopted,

which has proved effective and safe over severalyears' usage. Although an electric fireelement was used, the heat is dissipated tosuch an extent that clothing can fall from thegrid on to the element and remain there fora long period without any over -heating. Anordinary coiled wire electric fire element of25o volts 600 watts rating was used, but theworking temperature was reduced from thenormal bright red heat to a barely visibleglow by pulling out the element to several

drying cabinet.

4S'1

2431

kv 24

,/,'2"ne dowel

PICab/e hook

--r

7 r:71

$2.

Figs. 3 and 4. -Derails of the framework showing slots and dowels.

Jo"


154 NEWNES PRACTICAL MECHANICStimes its normal length. The heat was furtherdissipated by placing immediately above theelement a sheet of perforated zinc sheet suchas is used for meat safes, etc. Above thisagain, with about tin. spacing between, wasplaced a layer of small -mesh wire netting.With the current switched on, the hand canbe placed in contact with the wire nettingwithout injury. In spite of this low prevailingtemperature, the total heat released within thecabinet is sufficient for its purpose. Theelement wire is supported by asbestos boardand all connections are fully protected againstaccidental contact.

Heater ConstructionThe baseboard is made from lin. thick

asbestos board and the large piece whichcarries the element wire should be cut toshape and dimensions shown in Fig. ro. Thecentral slots (to assist air circulation over theelement wire) and bolt holes for 6 B.A. sizebolts should then be cut. The short endsections are then cut as shown. These areintended to fasten to the main board with

Joint ;4"

Slot 8

Fig. 6.

Fig. 5.

Figs. 5 and 6.-Details of corner joint andslot B.

insulated 6 B.A. bolts in order to protect thecable connections and to cover the nuts andbolt -ends of any part in connection with theheater wire and therefore electrically alive.These sections are fixed later.

The main element terminal screws arefastened to the main board, and intermediateelement supports prepared by cutting piecesof brass shirnstock or similar thin sheetapproximately 2in. by rin., folding in half tomake a double 'in. by sin. layer and makinga small hole in the double thickness to take a6 B.A. bolt. This is shown in Fig. ro.

Terminal

Cable slots

Terminal

Electricelement

Fixing the Element WireThe element wire, which will be very

closely coiled when purchased, is fixed by itsfree ends to the two terminals on the base-board, still in the very close -coiled condition.The centre of the element length is found(by counting the coil turns) and about threeturns at the centre are straightened out. Oneelement support as described above is slippedover this straight section and bolted to thebaseboard at the same end as the terminals(see Fig. so). Each half of the element isagain sub -divided equally into two and thecentre three turns straightened out. Anelement support is slipped over each of thetwo straight sections in turn and a gentle pullis exerted on the supports in order to extendthe coiled wire just sufficiently to allow thesupports to be bolted down at the other endof the baseboard. It is important to see thatthe coiled wire is not over -extended (i.e., thatsome tension remains when the support isfastened down), otherwise the wire will beslack and unsafe on the baseboard.

Fig. t I.-Exploded view of the end sectionof the asbestos board.

The baseboard is next surrounded by aframe, made by bending a length of I -sectionbrass curtain runner to fit snugly to the board,'the flange of the I -section supporting theboard. Dimensions are given in Fig. to. Theends of the runner strip may be boltedtogether with a web -strip or may be butt -jointed and soldered. Stout wire cross -bracing underneath the baseboard may beadded if desired. On the element side ofthe baseboard a number of small L-shapedpieces of brass strip are soldered to the innerside of the runner strip to hold the baseboardfirm.

Brass curtainrunner

Asbestos Aboard

A

Stiff wire supporting gauze and netting

23"

1-.0- 8Stiff wire Soldered

supportAS

I ,

Element

i Section I

A A

DoubleZinc I

gauze Iasbestosboard

B

Clips

mesh w re Asbestosnetting board

Hook

rt-btraV6-N Tex -Asbestos board Element Intermediate element support

Fig. 10.-Details of the heater construction._Wire loop

Fig. 7.

22P;

January, 1953- -

Slot C

Drilled haltway through

2Dowe/

Fig. 8.

44Long extensionto fit into slots

8

°2374Outside

Dowels

Fig.9.

TN Plywood

Fig.7.-Details of slot C. Figs. 8 and 9.-Theclothes grid and details of dowel end support.

A length of three -core cable is nextconnected to the underside of the terminals,sufficient length being separated to lay insidethe cable slots cut in the end board section(Figs. ro and r r). The earth lead is solderedto the frame. All electrically live points onthe underside of the baseboard are nowcovered by bolting up the end sections ofasbestos board (Figs. to and r).

A stout wire frame (lin. diameter approxi-mately) is made as indicated in Fig. to andis soldered to the frame. The perforatedsheet is fitted over this frame as in Fig. so(note particularly sections AA and BB),completely covering in the element wire andbaseboard. The wire netting is next fittedin accordance with the sketch, again coveringin the whole framework of the heater, and asound job made of soldering netting and sheetto the frame.

The heater is suspended permanently fromthe lin. dowel member of the main frame-work by two wire loops soldered to the heaterframe end. Two stiff strip metal hooks aresoldered to the heater frame at the endremote from the wire loops, and with thecomplete drier erected and the heater loweredinto position the hooks are bent so that theysupport the heater by hooking on to the lin.dowel member of the main frame (see Fig. 2).Finally a short length of cord with a lin.diameter wire ring is tied to the wire nettingnear the hooks and the cord length adjustedso that the heater is comfortably suspendedfrom a small hook in the top member of themain frame when in the folded storageposition (Fig. r). Two hooks are screwedinto the frame (Fig. 4-heater half) to carrythe cable when folded.

When setting up, the two parts are openedout at 90 deg., the grid removed from onehalf and the cable unwound from the other.The two parts are stood together as shownin Fig. 2 and hooked together. The heater islowered into position and plugged into anelectric supply. The grid is dropped intoposition and clothes hung over the rods,hanging down inside the cabinet. For airing,it is preferable to lay a large duster or similarmaterial over the whole of the cabinet top.This restricts air circulation and a gentleairing heat is obtained.


January, 1953

MODPINEWNES PRACTICAL MECHANICS 155

LOCOMOTIVEBOILER MOUNTINGS

The Correct Shapes and Curves of Chimneys, Domes, and Safety -valve Casings

UNDER the term " mountings " all itemswhich are attached externally to aboiler should, of course, be included,

but in this article, because I intend to dealwith the subject from an aesthetic aspectand not so much from a technical one, Ishall cover only those most prominent fea-tures : the chimneys, the domes and thesafety -valve casings. It is not the purposeserved by nor the construction of these thingswith which we are concerned, for they arealready well known to model locomotivebuilders, but the accurate reproduction of

N.E.R. PACIFICS. (siftno.,,L cRE5LE

rFig.

L. M. & S. R. 4-6-0.-5XrCLA55 AND OTHERS(5IR WILLIAM STAMM)

ft .tFig. 2

their true external shapes and proportionswhen reduced to miniature size, by scale.

In the majority of full-size prototypes theshapes and curves are very elusive, and someexcuse may be found for model makers whofail to get them true, when it is consideredthat general arrangement drawings-publishedin books and engineering periodicals-andeven small scale diagrams issued by railway

:-works, are scarcely ever correct. Sincethese are the sources on which themodel maker has to depend for his informa-tion how can he be expected to make hisengines look exactly like the prototype ? Forit is an unquestionable fact that if either,or all, of these prominent and importantmountings are not faithfully copied the wholecharacter of the model is altered and itsidentity may be almost, if not quite, lost.

In order to assist the model maker toattain accuracy in the form and proportionsof his three miniature mountings I have pre-pared drawings of the chimneys, domes, and,in some cases, of safety -valve covers, for eachof the four railway groups before nationalisa-tion and, so far as was necessary, of each ofthe biggest of the old companies prior to thegrouping of 1923. These drawings cover aperiod back to about the last decade of thenineteenth century. In a few cases examplesare given prior to this.

Nearly all the drawings have involved aconsiderable amount of, trouble in their pre-paration ; many have been scaled downfrom larger drawings and still more havebeen scaled up from photographs, for whichphotographs a scale had to be constructedfrom known measurements, such as the wheel

By "ENGINEER"

base or wheel diameters. I have given ascale against each item and where I haveshown shading lines the parts so shadedare of polished brass or copper. All un-shaded portions of chimneys, or the wholeof them, are black and domes shown plain arepainted the same colour as the boiler.

The first batch of drawings, Figs. r to6, show chimneys of forms introduced eithershortly before, or after the date of groupingof the railways ; all of them are in use atthe present day.The London and North Eastern Railway

Fig. I shows a very much shortened formof chimney with characteristics originated byPatrick Stirling of the Great Northern andcarried on by Mr. Ivatt. On some of theengines of British Railways it will be foundto be taller owing to lower boiler level, butthe same curves or radii are preserved.The London, Midland and Scottish

RailwayFig. 2. Several classes, beside the 5XP,

have this chimney. Note that true curvesmake up the general form of the shaft; thereare no radii. The chimneys of the Pacifics(4-6-2) are shorter and the curves smaller.The lip at the top is noticeably smaller thanthe diameter of the shaft. Some of the latestBritish Railway locomotives, of course, havedouble chimneys ; these are not shown.

Fig. 3. Here is a chimney which Mr.Stanier (afterwards Sir William Stanier)placed on the smokeboxes of six coupledgoods and many tank engines built or re-boilered by his predecessors. On the tenckrengines many of them are shorter than thedrawing shows thein, whilst on some tankengines they are a little taller. Staiiier, ofcourse, went to the L.M.S. from the GreatWestern and this chimney is a very closecopy of Dean's but with a black top insteadof copper.The Great Western Railway

Fig. 4 shows what is, in the opinion ofmany people, the most handsome and boldestchimney in use to -day. It is somewhat shorterthan the chimney on the " Castle " classengines and where copper -topped chimneysare used on other classes they are both tallerand of a little smaller diameter.

G.W R. ALL BLACK. OM GOODS, MINERAL AND TANK

[MMES.

Fig. 5 (Left)

Fig. 6 (Right)

Fig. 7 (Below)

Many Great Western. engines have the farless attractive, wholly of iron, smoke ventshown in Fig. 5. This is cast in one piecealthough it is made to look like a built-upchimney. At one time some of the two -cylinder 4-6-o engines of the " Saint " class

L.M.S CHIMNEY. 5TANIER RtPLACEMEKr orOLDER PATTERN).

Fig. 3

G.W.R. *KING CLASS]fit 1

Fig. 4

C B.CoLLarr

had this but now all have the cylindrical pat-tern with copper tops. I venture to thinkthat if Mr. Collett's " King " class chimneyis the most handsome, and all that a locomo-tive chimney should be, then this all -blackpattern is the most ugly and most out ofkeeping with Great Western traditions.

The Southern RailwayFig. 6 represents the chimney of the re-

boilered " Lord Nelson " class and others.If the parallel portion of the shaft werelengthened it would represent the smokeboxmounting on engines having lower pitchedboilers.

The domes and valve casings for themodern engines (the L. & N.E.R., theL.M.S. and the S.R.) I have shown in onedrawing, Fig. 7. All three of these shownvary in height on different classes, of engines,although it may be taken that the radius of

SOUTHERN RLY. MR e L MAUMELL


156 NEWNES PRACTICAL MECHANICS

all curves is maintained. On the GreatWestern boilers there are, with a very fewexceptions, no domes, but on the taperedboiler barrels there are the safety valves,the casings of which are of polished brass.Attached to each of these are two coversover the top water -feed check valves. Thesecovers and the lagging plates over the waterpipes are painted. The assembly of one ofthese is drawn in Fig. 8.

The Pre -grouping CompaniesThe old independent companies were in

1923 grouped together to form four greattransport combines covering the whole ofGreat Britain. I cannot deal with them alland have to omit quite a number of thesmaller systems. To commence I shall takethe Midland Railway. Fig. 9 shows thecorrect forms of all the chimneys in use fromthe time that Mr. Johnson assumed office aslocomotive superintendent up to the time ofgrouping, but the Johnson drawing first callsfor comment. Up to some time in the lateeighties Mr. Johnson built up his chimneysin three parts: the base, the shaft and the

R M DE:LEY1904 w 1909

t:_AND RLY 5 W1),,NSOM

7¶

.7 .1

R M DEELEY

Fig. It

r.7. I I,

G. W. R. KING & CASTLE. CLASSES

Fig. 8

this it will be seen that the top was likeJohnson's, but the shaft conical and inverted.When Sir Henry Fowler took office in 1909he also retained the same top, but his shaftwas cylindrical. This chimney was made toreplace Johnson's even when no other altera-tion was made to the engines, notably onJohnson's well-known single wheelers. Eventhough the smokebox did require renewalthere was no reason why the original chimneycould not have been put back again. SirHenry Fowler's dome, Fig. 11, became a

SIR HENRY FOWLER1 1909w 923

NR HENRY FOWLERA0 MAW 01.11.110 93 9T.4114 11.1.4V9

cap, but from about 1889 he cast them inone piece. The dotted lines in Fig. 9 showthe positions of the lapped joints of the baseand cap over the slightly tapered shaft of theearlier chimney.

The lines of the one-piece casting .were-pure curves and resulting in one of the mostpleasing chimneys ever designed. To go withthis chimney Johnson put on his engines theequally attractive dome and safety -valvecasing, which is drawn in Fig. to. On thedome there were two levers, valves andspring balances, side byside, and in the brassvalve case there wa3 onedirect spring -loaded valve.When boilers becamelarger and higher pitched,notably in Johnson's firstcompound engines, thechimney, whilst retainingalmost the same curves,became shorter, and theSalter lever -loaded valvesdisappeared. The domethen became more likethat adopted by Deeleyand drawn in Fig. 11.

Deeley's chimney isshown in Fig. 9 ; from

G.WR. W9 DEAN0377.31902

Fig. 12 (Right)

Fig. 9 (Left)

Fig. to (Right)

L.& N.VV.R. FWWEAB.G WHALE two C1 BOWEN COOKE.

common form with other designers and willbe referred to again later.

The London and North Western RailwayThe mountings for the engines of this

company, shown in Figs. 12 and 13, re-mained unchanged in detail from 1871, whenF. W. Webb took office, all through hisregime and those of Whale and BowenCooke to 1923, the only modification beingthat of height. When Bowen Cooke brought

DEAN -CHURCHWARD1902 To 1921

Fig. 14 -

January, 1953

out his " Claughton class of four -cylinder,4-6-o type engines, the domes, though low,still retained the hemispherical top.

Note particularly the proportions of thechimney top, the square base, and theamount of taper on the dome and upper partof the safety -valve casing.

The Great Western RailwayWilliam Dean was not the originator of

copper tops to chimneys, even on the GreatWestern, yet he evolved the extremely neatform which has persisted down to the presentday and was copied by at least two othercompanies' designers. The standard chim-ney of Dean's own engines is drawn on theleft-hand side of Fig. 14, and in Fig. 15the dome and safety -valve casing whichDean put on his fine bogie singles and alsoon the four 7ft. 4 -coupled bogies, Nos. 7, 8,14 and 16. These were about the largestever put on British engines. All Dean'searlier engines had similar but smaller domes.When Churchward took office, officially it

MIDLAND RLY. 5 W JOHNSON

Li 7

L.&N.W.RFig, 13

F. W WEBB

was in 1902, but unofficially before that, hedropped the use of a dome with his Belpaireboilers and put Dean's safety -valve casingon the boiler barrel. At the same time hecompletely changed the chimney to an all -black, tapered, cast-iron one, as in Fig. 14.This was retained for some years until thecopper top was revived about 1908. Church -ward's chimney had a pleasant appearance,but it never looked right on Great Westernengines.

G. W. R.

DEAN'S 7.8't SINGLES"S.

Fig. 15



The Great Northern RailwayWe have in the Great Northern an

instance of loyalty to an efficient and artisticdesigner, inasmuch as the general characterof Patrick Stirling's chimneys has beenmaintained by Mr. Ivatt and Sir NigelGresley, and exists to the present day.Strangely enough, Mr. Stirling's earlierchimneys were built up, as in the centredrawing in Fig. 16; then the shape was alittle modified and, with the shaft, cap andbase in an unbroken outline, was cast in onepiece, as in the chimney on the left; finallyhe reverted, in his last batch of 8ft., outsidecylindered singles, to the much older form,though I feel sure that these also were cast.

The long, unbroken line of his boilers wasdistinctive. His beautifully -shaped brasssafety -valve casing, the lines of which weretrue curves, occupied the usual position overthe firebox. This valve casing is drawn inFig. 17. Ivatt's chimney, on the right ofFig. 16, was used on his famous Atlantic

G. N. R.

Fe

O.E.R JAMES HOLDEN

Fig. 59

almost like Dean's, on the Great Western,except for the fact that bright brass wasused instead of copper. This chimney firstappeared in 1898 on the handsome 7ft. bogiesingles. After that, though shortened onhigher boilers, this chimney became standardby Mr. Holden's successors.

Mr. Holden's dome and safety valve areshown in Fig. lg. Both were painted, withthe exception of the bead around the top of

HAIVATT.1696To1911

PATRICK STIRLING, ¶866 It596

Fig: 16

G N. R. 5I1RuhO

Fig. 17

ti

G.E.R. ADAMS. BROMLEY,

WORSDELL AHD JAI HOLDENJAMES HOLDENA

J HILL

type, and the dome was similar to Fowler's,in Fig. II.

The Great Eastern RailwayOn this line the plain chimney, with a

simple, beaded iron ring at the top (seeFig. 18) was adopted by at least four suc-cessive locomotive superintendents, and thenJames Holden, after having adhered to itfor about thirteen years, changed to a straightcylindrical chimney with a polished top,

T.W WORSDELL teaz To oo90W. WORSDELL. 1e90 TO 191u

SIR VINCENT RAVEN..No

tow!) FLETCHER, 1.554-188/ N. E. R.Fig. 20

shown in Fig. 21. There were two valvesand levers on the dome, as in the case ofJohnson's, on the Midland engines. Mostdomes of other designers had hemisphericaltops, but Fletcher's were a little elongatedand it should be noted that the radius isstruck from points off the centre line.

The chimneys of T. W. Worsdell and ofhis brother, Wilson Worsdell, were shapedas shown on the right of Fig. 20, althoughthey, of course, varied in height. The firstof Mr. Worsdell's chimneys were wholly ofcast iron, and it was Wilson Worsdell whcintroduced the polished top, which was ofbrass, not copper. Chimneys of this pattern,together with the safety -valve casing shownon the right of Fig, 21, remained in useto the end of 1922. Although the valve casewas elliptical at the top the part whichsaddled on to the boiler lagging was circu-lar in plan. The Worsdell dome was almostthe same as that of the Great Eastern,Fig. 19, with the possible exception that thesplayed base was of little larger radius.

CHARLES SAC RE, 0359 ,o1834

Fig. 18

the valve casing, which was of brass. Notethe slight taper on the dome.

The North Eastern RailwayEdward Fletcher adopted a plain -tapered

shaft with a small bead at the top andterminated at the base in pleasing curveswhich I have reproduced in Fig. 20. Some-times there was, in the earlier chimneys, asecond bead around the waist, at the pointwhere the curves merged into the straightlines.

Fletcher's dome and valve casing are

N. E. R.Fig. 21

TW u.o W WORSDELL

J G ROBINSON0900 ,o 931,

HARRY POLLITTM. 5. & L. AND CI. C. R.09! re MD

Fig. 22

The Great Central RailwayThe name of this company, prior to 1897

was : The Manchester, Sheffield and Lin-colnshire railway.

The locomotive superintendent at that timewas Mr. Harry Pollitt. His chimney isshown in the centre of Fig. 22 and besidethe top of it is drawn the deep iron beadof his predecessor: Mr, Parker ; in otherrespects both chimneys were alike.

Before Mr. Parker, Mr. Charles Sacre wasin office ; he was the designer of the verypretty 7ft. 6in., 2-2-2 engines, which carried

the chimney shown on theleft. The domes, up tothe year Iwo, wereno r ma 1, though Mr.Sacre's were somewhattaller.

The chimney of Mr.J. G. Robinson is shownon the right of Fig. 22and his dome and safety

J G ROBINSON

\G. C. R.

Fig. 23

valves in Fig. 23. Thechimney was finished atthe base with curves andnot radii.

(To he cenchided.)



THE drawings and sketches clearly showthe main features of the side -carchassis, or bogie, for anyone desiring

to construct the arrangement in its entirety,but the special features consist of the coup-ling devices on cycle and bogie respectively,the brake mechanism and its connectionsbetween the cycle and the side -car, and theretractable rests which enable the user todisconnect the main machine and leave thebogie stationary with or without the carattached. These features have beenthoroughly tested in actual practice underpurposely severe conditions. In place ofa child, a sandbag weighing 421b. was carriedas passenger to test the general behaviour ofthe whole arrangement, e.g., reaction toframe of cycle, coupling tube and clamps ;effect of braking on steep hills with andwithout the car fitted, loaded and empty ;reaction on cycle frame and couplings whenrunning bogie over a specially laid bumpytrack with the cycle running on a smoothtrack ; behaviour of side -car assembly, whenstationary and independent of cycle, on anincline, in a fairly strong wind, and with achild passenger rocking the car on its springs.

In service this combination has coveredzoo miles on all kinds of road surfaces in-cluding rocky coastal byeways, country lanesand cart tracks. In all instances the impres-sions obtained were satisfactory to both therider and the child passenger. Furthermore,on reaching one's destination, should thepassenger be sleeping, as often happens, theside -car can be detached from the bogie andcarried indoors as a cot.

Should either parent find it necessary touse the cycle independently the bogie canbe uncoupled in a few seconds, the restslowered, and the cycle is free and un-cumbered while the bogie Jemains conveni-ently intact and ready for reconnecting whenrequired. Speed of assembly and dismant-ling is achieved by the use of wing -nutsand by the design of the coupling fitmentsconcerned.

Is there any need for the fitting of abrake to a side -car or cycle trailer, and hasit any definite advantages ? With regard toits use with a trailer many readers will, Ifeel sure, agree that a suitable brake is anecessity, by reason of the running positionof the trailer in use, but with regard to side-car braking there will be many and variedopinions. In order to put the matter totrial thoroughly, the mechanism sketched anddescribed in this article was devised and, inpractice, it is definitely a great advantage,not only on steep hills where the danger of"running away"is paramount, but also onbusy roas where traffic is plentiful in bothdirections.

FLzwe4 4

Fig 7 Brake trigger. T.(See a/so fig la)

...1/6" holes and rivets7a

rjmajt

17;

Brake ApplicationThe rear brake of the cycle is applied with

one hand while the side -car brake is appliedwith the other. A little practice soon enablesthe user to exert initial pressure to thecycle brake before bringing the side -carbrake into action so that all the retardingstrain is not thrown suddenly on to the

The side -car chassis fitted to a cycle.

couplings and frame of the cycle by the dragof the moving but decellerating side -car.The action must be spontaneous but smooth,and is comparable to the foot movementson clutch and accelerator when changinggear in an automobile ; first pressure on

Material is sheet meta/

holes

ritdr,^ .14cTo sidecar

34/ 1st stage of lever \

Brake to cyclewheel (front)

An Efficient Outfit wit}

The completed side -carready for use on the

road.

cycle brake and immediately apply pressureto side -car brake. The result is an effec-tive two -wheel retard with no ill effects orundue strain on the parts acted upon. .Theabsence of front -wheel braking is apparentsince both the rider's hands are engaged,but the combined action of the dual brakesis found to bring the combination to evena skidding halt which the action of a front -wheel brake application could do little toimprove. During experiments the side -carand cycle rear -wheel brakes were synchron-ised so that they would both act frompressure on one lever, thus leaving the otherhand free to apply the forward brake.Results proved that the forward brake wasuseful but not necessary, since the rearbrakes had to be applied first, and that action.alone sufficed before ever the forward brakecould be effective. To apply the front brakefirst was undesirable, as it tended to jerkthe side -car forward quite an appreciableamount, causing severe stress on couplingsand frame. After extensive trials the originalarrangement was reverted to, and the for-ward brake left idle. When the side -carbrake is operated, a tendency for thehandle -bars to veer left is experienced, butonly a slight tendency, which is readilyarrested by the rider himself.

The trigger shown in the accompanyingdrawings is designed so as to be placedwithin finger-tip reach and the lever givesjust sufficient pressure for the operating ofthe brake mechanism. Anyone wishing todispense with the specially made triggercan do so by using the brake lever fitted tothe front wheel of the cycle. The Bowdencable from the forward brake is disconnectedfrom the lever and the nipple of the side -car

Ws"

0416ov-IP

The oil hole isje'diamCsk,

remaining holeare Uri/ie.-el totake t.

bolts in thepose ions as

snow()

Fig ICCoupling andangle brackets

25%

Figs. 6 and 7.-Details of braketrigger components. (Note : A des-

k. Whit. csiceolt cription of Figs. 6 and 7 will be givenrig.6 Detail at f:Fistl. next month.)


4P2 31-761

7.="


cycle and when the side -car is not in use isstill there ready and is no great extra weightfor the soloist to carry. Furthermore theleverage obtainable from the standard brakelever is too severe for the brake mechanismhere described-the object of our brake beingto halt the side -car, not the whole combina-tion. The halting of the whole combination,or the gradual slowing down of same, isachieved by the combining of the cycle andthe side -car brakes. Neither will do it suit-ably alone.

The method of arranging the brakingsystem can be adapted to suit most existingready-made chassis, but for those intendingto build the whole side -car from " scratch,"

brake inserted in its place. No great gain to be connected up again. By utilising the attention should be paid to the constructionalis derived, however, because when using the trigger fitting none of the standard fittings design so that it will be of such a naturecycle for solo purposes the front brake has of the cycle are disturbed. It is left on the as to co-operate with the braking system. In

SIDE -CABrake and Retractable Rests for Use When Detached

By D. V. PRIEST, A.M.Inst.Mechs.

fig! Plan of bogieand brake position

Fig. 2 Side elevation With wheelin place end brake mechanismshowing. Also retractable restin dote) and retracted position

Detail of coupling end angleBowden cable

bracket also hinged c/amp shownto cycle open

7.4'S

Brake trigger TBreak release ,spring and pecking,

piece

Section ofwheel rim -N

OHinges rivetted Go tubes

/2"

3A6Tie rod on D

rest -)1

Brakeart/sting

FScrew

I C

G

Brakemechanism

L

w

I I -

I

N,

a

G

2%A

S

2

8E2' 1.3*

_

4

Li

L

- -..' K

Outline,oF splash, guard:3

/ \/ \8V/ \/ . Broke release springi -..-047-- -.414- ,-4--

I/-

9'G Spring Hinged demos G N

-AX-C ,,,,,, All C, pring

11111111*WIll IIIITAMIMIIIIIIoponc_- --

Briake shoes To suit axialof wheel

124

Fig.3 End elevation in direction of- arrow with wheql removed' to

show position of the brake blockson bogie

I

Wingnuts- 2.D

2'g+-

8

6

I. dia.

Rubbershock Washers-----°.

absorber 1st. stage ofdetail at L

7."4.4ft.component L

4

Cable linkL6

Slot totakecable Method of

securing toW member H

Drill to suitbolt on sl;:cy

Brakeshoe.

10.V.Ilt..r

1;

f7,

i diem

111

2nd,stage ---;Diam.hole Forbrake release spring

4W: -114. Ak/'

i. iL, end La

Fig SDetails,4 5..,6' !--4"

of brake .,,t,- ______Li4. °"mechanismmechanism 3 -" icomponents

Fis 4 Exploded view of bogie showingclamps in closed position

1.3 and L4- 31=-Irt t6

-4#Ls

Figs. t -to 5.-Detaih of bogie frame, brake mechanism, and retractable rest.



Co,

any cycle side -car combination there is acertain amount of drag which, of course,leads to stress and strain between the cycleand the attachment. This is to be expected,due to the cantilever like form that couplingarrangements often take and because of thedifficulties of designing a coupling suitablefor attachment to the meagre holds affordedby the rear forks of the cycle. It either hasto be a heavy arrangement to give the neces-sary strength where required or it has to bea light but large arrangement which whenfitted to the machine covers quarter of therear wheel, picks up mud and generally getsin the way during repairs.

Coupling RigidityThe bogie is often found to be of rigid

construction, and, although allowance is pro-vided for "lean" when cornering and so on,the rest of the steelwork is decidedly robustand holds itself rigid from the coupling tothe hub of the side -car wheel. Thus anyjolt received by the wheel is transmitteddirectly to the coupling and into the cycleframe.

To avoid these harmful reactions the side-car bogie, the couplings and the brake mustafford just enough rigidity for safety in usebut with enough " give " to cut out as muchas possible the shudders arising from bumpyroads and other contributors to the detri-ment of the machine's welfare.

Referring now to the drawings, Figs. 1,2 and 3 show the general constructionalfeatures in three views. Fig. x is a planview of the bogie without the wheel butshowing the position of the brake and itsparts including (in Fig. la) the cable connec-tion to the brake trigger on the cycle handle-bars. At lb are shown details of the coup-ling clamp in the open position, while Fig.lc is an exploded view of the clamps -andangle -iron brackets, one being for the for-ward and the other for the rear positionsrespectively. For convenience in referenceeach part on the principal views is letteredand the lettering applies in all views given.Fig. 2 is a side elevation of the bogie withthe wheel in place and it must be noted thatthis particular wheel is 13in. diameter acrossthe rims. It is important and is the govern-ing factor in the correct positioning of thebrake arms (detail " L ") and, of course, theheight above ground level of the couplingtube and fork clamps to be described later.In Fig. 2 the rests (item " J ") are shownin the down position while the retractedstation is indicated by the dotted lines. Thesprings used to support the actual carriageare marked " S " with cross -member " G "in place. The inset is an end view in twodirections of the hinged clamps " C." Oneview showing the hinges and the other theplacing of the angle -iron bracket, the clamparms and the main frame " W." Fig. 3 is anend elevation looking through the wheel butwithout the wheel in place. The brakeshoes and brake release spring are alsovisible with the splash guard and axle sup-port " K."

ConstructionStarting with the main frame " W," a

length of 3/16in. x sin, mild steel flat stripwas chosen as the most suitable material.It proves stiff enough for safety, but due toits thickness it allows for a certain amountof flexibility when made up. A piece3ft. yin. long was taken and forged to theshape illustrated, the bends for the wheelguard being of tlin. radius. A piece of thesame material is cut to 28in. long and bentto the inverted U shape needed for the splashguard support "K." From the bends inthe frame " W" to the extremities of thearms measures 194in. (see Fig. 2) and on

completion of the forging operation these arecut. The distance across the arms isto the inside and train. to the outside (seeFig. t). Next two t4in. lengths of tin. xlin. flat strip are cut to form parts " Hi "and " H.2." This thicker material was chosenin order to prevent any fore and aft rockingmovement in the bogie, i.e., to ensure itsbeing perfectly horizontal and parallel to theroad under all running conditions. Thesestrips were welded to the frame in the posi-tions shown, t3in. from the outer edge to theouter edge in one direction and having riin.overhang in the other. When welding it isadvisable to deal first with the cross -member`11," as once it is in place the legs will notclose in as would be the case if the othermember was welded first. The heat appliedso close to the bends causes the material tostraighten and so alters the set of the arms.With member "H1" secured first, this isavoided and the parallelism retained. Withthese cross -members secured the part " W "is complete apart from drilling the holes andattaching item " K." This latter is drilledto suit the wheel axle diameter and then

View of the side -car chassis, showing theretractable rest.

springs and

slotted as shown to allow for any verticaladjustment and also for removal of the wheel.A distance of 2in. is marked from the endsof each leg and this gives the position forwelding to the frame " W " on the one sideand cross -member " H2 " on the other." K " is placed at right angles to " W " andis, of course, centrally placed on the wheelguard, i.e., on the 9.1in. mark. Three lin.holes are drilled to accommodate the splashguard bolts, a lin. hole is drilled at each endof the cross -members "H1" and "fl," toretain the springs " S " (see Fig. 2), a tin.hole is placed in the centre -line mark ofmember "H1" and on "H2" at tin. fromthe main frame " W " on either hand a lin.hole is placed to accommodate the brakearms " L.' The positioning of these holeswill, of course, be governed by the diameterof the wheel from rim to rim, but in thisparticular case they are as stated.

Clamps and BracketsReferring now to Fig. Ic, the couplings

and angle -iron brackets are dealt with. Theclamps " C " consist of two pieces of tubingof inside diameter tin. with a wall thicknessof preferably Bin. making for skin. outsidediameter. These are carefully sawn to forma top and bottom as in a split bearing. Thearms " D " of the clamps are of uin. x skin.mild steel flat strip the bottom arm being4in. long and the top arm ruin. long. Theseare drilled to take kin. dia. bolts at 2in.centres. The holes are elongated to affordadjustment when setting the wheel track and

the pieces are then welded to the top andbottom halves respectively of the split tube.It is advisable to do the welding with thetwo pieces firmly bolted together so that agood seating of the two arms is ensured.With the welding completed, the hinges cannext be fitted. These are ordinary steel butt -hinges, size lin. They are bent to conformto the outer wall of the tube and are thenriveted. Countersunk rivets are used with theheads inside the tube the holes being counter-sunk for this purpose. This is done by mark-ing the holes on the outside, drilling them,parting the two halves and countersinking theholes on the inside. The two halves are againbolted together, the rivets inserted, a roundbar or bolt of sin. diam. pushed throughthe bore to hold them in place, the hingesplaced on the rivets and the heads formed byusing a small ball -pane tack hammer insteadof dollies. The rivets may be of aluminium,as the hinges do not take any strain in ser-vice-the weld and clamp arms do that. Bypassing a bearing scraper over the inside ofthe now completed tubes any flats or burrscan be removed from the rivets so that a good

smooth bearing surface remains.The addition of a small oil hole asshown is useful as a final touch.

Track AdjustmentThe brackets marked " E " are

made from two pieces of 14in. xdin. 3/16in. angle -iron, skin. long.It will be seen that they are drilledas front and rear pieces. The flangestaking the clamps (" C " and " D ")are drilled lin. at 2in. centres to suitthe holes in the clamps. These arenot elongated, however, because onlyslight track adjustment is required.The centre of the hole. nearest thecycle is lin. from that edge (seeFig. rc). In the remaining flange,marking lin. from the wheel end,/lin. holes at in. centre are drilled.These are then transferred to theframe " W " by placing part " D "on " W " with the end of the angle -iron flush with the end of the legsof the main frame. The holes are

scribed through and drilled. The brackets" E " are secured to " W " by only one tighttin. bolt and the clamp arms " D " are like-wise secured by one bolt. The remaining holesaccommodate the free bolts and their wing -nuts shown by the arrows in Fig. 2.Before tightening the securing bolts a lengthof rubber of skin. is inserted between theflange of " E " and the leg of " W." Thisconsists of ordinary draught -stop such as isplaced around the edges of doors and servesas an ideal shock absorber at this vital con-structional point. An examination of theviews at Figs. I and 2 will show that betweenthe cross -member "Hr" and the securingbolts " N " there is a kin. length of therm. x 3/16in. main frame " W." Thisnarrow section may be termed the weakestpart of the chassis frame but it is thus thepart which takes the unwanted stiffness outof the arrangement.. The tin. section of theside -car bogie, though it is not long enoughto allow bending, is long enough to allowspringiness. The stiffness at the weld on"Hl" plus the stiffness at the bolt " N "is an additive to the functioning at this im-portant point. The rubber insertion is notessential but is a precautionary device anduseful in so much that it fills up the gapcaused by the joining of the flat face at " W "to the tapered flange of the angle 'iron bracket" E." It also cushions the faces and acts asa mild form of spring -washer for the retain-ing of the wing -nut which holds the restsin the retracted position, as should thesefall down, through vibration while travelling,the results would be annoying.


January, 19-53

Carriage SpringsThe frame with brackets and clamps is

now complete except for the carriage springsand members " G." Fig. 2 shows the springsin place on the extremities of the cross -members "H1" and "H2." They are 3tin.long in their relaxed state and t -in. dia.,having six coils. If it is at all possible fouridentical springs should be obtained,although, provided they are strong and reli-able, odd ones would do in these days ofscrap shortages. They are retained by kin.dia. bolts in the holes provided on "H1" and"H2." The members " G " are also of3/16in. thick flat strip kin. wide and 13in.long. These strips are identical and it is aswell to drill them both together. The holesfor the springs have their centres lin. fromeach end and are of kin. dia. The holes forretaining the carriage are also tin. dia. butthose nearest the splash guard are drilled 2in.from that end while those nearest the cycleare zlin. from the end (see Fig. t). Thisis to afford as much clearance as possible forthe rider's leg between the pedal and thefore part of the carriage. The distance be-tween the hole centres is 81in., as shown.The holes for the springs on members " G "are countersunk for obvious reasons and thenut manipulated on to the bolt inside thespring coils. Once they are secured they arepermanent: A tight jawed spanner simpli-fies the job by holding the nut while the boltis screwed into it from above. At this stageof the work the wheel may be fitted intoplace ready to receive the brake fittings.

/7

NEWNES PRACTICAL MECHANICS 161

Fig. 3 is merely an end elevation. The dottedline from part "L " to " L " represents thebrake release spring of which more will besaid later. Fig. 4 is an exploded view of themain components from detail " C" to detail" Y." No dimensions are given for the sakeof clarity in this view.

The Brake ComponentsIn Fig. 5 the components of the brake

mechanism are shown.. These are marked Lfor the arms and La, L2, L3, L4, L5 andL6 for the other pieces. The full-size illus-tration on the extreme left is self explanatory,the lock -nuts being fitted to ensure securitybut freedom for the arm to pivot on the bolt.The washers are used to centralise the brakeshoes so that contact with the rim is madeas near diametrical as possible. More orless washers May be needed than are shown,these being merely to denote their presence.In the centre view is shown the arms. Theyare of tin. angle -iron, 4in. long and oft/t6in. flange thickness. They are identicalexcept for being right- and left-hand. Theview is of the left-hand arm and illustratesthe method of cutting and bending thehorizontal and vertical flanges. In order toretain as much strength as possible a mitre -cut is made in the horizontal flange. Thisextends for tin. from the brake shoe toakin. on the mitre, leaving a t/t6in. x lin.strip which is bent back to meet the angleof the wheel rim. Here again the amountof bend must be ascertained whilst doirig

the job, since the brake shoe must carrythe block into contact with the, rim in thebest and firmest way during its operation.The hole for the brake shoe is kin, fromthe edge and of a size to take the boltprovided with the shoe. These fittings arestandard cycle brake shoes and blocks. Theonly other hole in the vertical flange is a3/32in. dia. one placed a t/t6in. fromthe end of the arm and kin. from the edgeof the flange. This is to accommodate thesmall hook in the brake release spring. Onthe horizontal flange two kin. dia. holes aremade at akin. centres starting kin. from theother end of the arm which is radiused offas shown. The connecting strips (Fig. 5 rightcentre) are of- mild steel t/t6in. thick x1in. wide. Little need be said of theseexcept to note that on the piece marked L5one hole is kin. dia. and the other3/16in. dia. Great care should be takento ensure the exact positioning of all holes,however, as any slight error will upset thewhole arrangement. Component L6 is madeto hold the nipple of the Bowden cable andis also t/t6in. x 1in, strip bent to the shapeshown, with a slot for the cable to passthrough freely. It will be seen that at/t6in. gap is left for joining the link tocomponent L5 which is held inplace by a3/16in. bolt and wing -nut. This is pro-vided for purposes of disconnecting whentaking the wheel out, etc., the other stripsbeing joined by rivets. The view of thecable link is full size.

(To be continued.)

Water Pinhole disc.

Casing

Aircock

Draw 011cock

_Plugs

A Perpetual Table Fountain

Upper tank

A sectional view of the completed fountain.

THIS little fountain is quite self-containedand does not need a constant supply ofrunning water.. It is portable, and can

be useI either indoors or in the garden. Atfirst glance it looks as though the secret ofperpetual motion has been discovered. Thewater in the basin is forcing itself in a jet toa height of loin. or more above its ownsurface! Actually, however, the jet willcease when all the water in the upper tankhas been forced out.

The fountain is made quitesimply. If you have a coupleof old petrol cans of equal sizethey will do splendidly for thetanks and will give about forty-five minutes' working withoutattention. They should befixed on their sides, one abovethe other, with a space of aboutBin. between them. A simpleframe of wood or metal can beeasily rigged up to keep themin position. The lower tankmust have an air cock at thetop and a draw -off cock under-neath; old gas fittings will comein useful here. The top basincan be made from any handymetal ; it rests on the uppertank and has a filling plug, asshown.

Pipes A, B and C are tubesLower tank of kin, or smaller diameter, pre-

ferably of brass. It is best tosolder all joints between pipesand tanks, as they must bequite watertight. To finish thejob, solder on the top of pipeC a thin brass disc in which apinhole has been drilled. Onthe size of this hole dependsthe volume of the jet and the

length of time the fountain will play.

How the Fountain WorksTo start the fountain, first put a plug in

the top of pipe A. Remove the plug fromthe bottom of the basin, fill the upper tankadd basin with water and put back the plug.Now unstop pipe A and the fountain willstart to work.

Magic? Not at all. When you un-plugged pipe A, the water ran down and

compressed the air in the lower tank. Pipe Btransmitted the pressure to the water in theupper tank, which was forced up pipe C andso out through the pinhole, forming thefountain jet. The flow will go on becausethe head of water in A is acting against asmaller head in C. No water flows throughB.

Of course, as the water rises in the lowertank, the "working head " of water is reducedand the jet weakened. The jet does not, how-ever, become a mere dribble but stops quitesuddenly when the lower tank is full of waterand the upper tank full of air. The waterlevel in the basin remains the same.Restarting

To restart the fountain, plug pipe A,open the air cock and empty the bottom tankthrough the draw -off cock. That tank willnow be refilled with air and the air cockshould be closed again. Now refill the basinas originally described, and the fountain isready for another " run."

A painted casing, of either wood or metal,will give the job a finished appearance. Thefountain is silent except for the sound of fall-ing spray.

$

THE MODEL AEROPLANE HANDBOOKAn Important New Work

By F. J. CAM M312Poges,303111ustrations,1216,bypost13/-Construction and Principles of All Types !

j GEO. NEWNES LTD., TOWER HOUSE iSOUTHAMPTON STREET, STRAND

LONDON, W.C.21.,.,14=1.11.1410.4

Published by



Miniature Plugs andMaking the Body

The hexagon bar should be checked in acentre or capstan lathe, faced and drilled5/32in. dia. to a depth of 9/16in.

Constructional Details of a Small Ignition Coil and PlugSuitable for Model Aircraft and Model Boat Engines

C oil CoreTHIS is made from soft iron wires, zin.

long. It is important, for good results,that the right type of wire is used.

It can be obtained from an old car ignitioncoil to ensure that it is of the right quality.Sufficient wires to make a core of 3/16in.dia. are required, and the finished core shouldbe wrapped with empire cloth insulation (onelayer).

Primary WindingThe, primary winding consists of approxi-

mately four layers of .o.24in. (23 S.W.G.)enamelled copper wire, hand wound on tothe insulated core, reversing the winding sin.from each end (D.C. resistance, .4 ohms).

Secondary WindingThis consists of 8,000 turns of .0024in.

(46 S.W.G.) enamelled copper wire (D.C.resistance 5,000 ohms). A winding fixture orbobbin is required to produce the secondarywinding successfully, and a suitable fixturefor this purpose is shown in Fig. i.

A former made from adhesive paper tape,skin. wide, should first be wound on to thespindle of the winding fixture. Four layersare required, and care must be taken tosee that the former is not too tight on thespindle, or there may be difficulty in with-drawing the finished secondary winding fromthe winding fixture. Start winding thesecondary, interleaving each layer with paper.00t in. thick and reversing each layer kin.from each end of fixture. Make off the

Electrode. cocklechrome wire

insulatorSteatite

JP

Plug body M.S.

start and finish off the winding with a flexpigtail for connection purposes.

Withdraw the secondary winding from thewinding fixture when complete.

AssemblyInsert the core and

primary winding insidethe secondary windingformer, and place theassembled coil in asuitable container, join-ing the finish of theprimary winding to thestart of the secondarywinding, and leadingthis through a suitableaperture, windingthrough the casing atsuitable points in asimilar manner.

Now immerse thecomplete coil and casingin hot paraffin wax,leaving it for a fewmoments until all airinside the container hasbeen expelled. With-draw from wax anddrain off.A Miniature Sparking

PlugMaterials required:a. Hexagon mild

steel bar, tin. acrossflats.

2. Old radio resistor

SCrew.52threads per inch

Assemble plug and spintapered portion of bodyover insulator

Plug

Primary winding

Core Insulated fromprimary winding withlayer of Empire taoo

CoilsFinish of winding

8000 turns interleaved paper00/ 'thick. se/f supporting whentaken off winder

Sot/ iron core 2. tong 416.:`,S

Co/mpiete cod

Fig. i.-Details of coil windings.Winding fixture for secondary coil

body, with holethrough t h ecentre, madeof Steatite, amaterial simi-lar to porce-lain.

3. A pieceof nickelchrome w i r eobtained froman old electricf ire elementof a diameterto suit thehole in theresistor.

4. A smallquantity o fgasket cementas used onmotor - carjoints, and alittle frenchchalk, addedto gasketcement to givebody.

Too/ for spinning body over insulator MS.

Complete plug i;sseintily Fig. 2.-The finished plug and sections ofits component parts.

This hole should next be counterboredkin. in diameter to a depth of kin. Turn theoutside of the bar to gin. dia. for a distanceof 3/32in. and chamfer down to the kin.hole to form a feather edge. Part off togive body a length of lin.

Reverse the body in the chuck and turndown to kin, dia. for a distance of 3/16in.and then screw cut or die the kin. dia.32 threads per inch.

Making the InsulatorGrind one end down to kin. dia. for a

length of 3/16in. and chamfer out to kin.dia. at the same angle as drill used to counter -bore the body.

Next, grind to kin. dia. for a distance of3/16in. from shoulder of chamfer, and thengrind down to 3/16in. dia. with radiusedshoulder. Grind off and face end approxi-mately tin. from start of shoulder.

The ElectrodeGrind one end of the wire to a fine point,

and bend it over at right angles. Make asmall ferrule to fit the top of the electrode.

AssemblySmear the inside of the plug body with

jointing compound and insert the insulator.Spin over the feather edge of the plug bodyon to the radiused shoulder of the insula-tor, using the special tool shown in Fig. 2.

Paint the electrode with jointing compound,insert the insulator, and then fit the ferruleon the end of the electrode and carefullyspin over, using tool in drilling machine.



4

111

THIS VALUABLEBOOK

which details the wide range of Engineering and Commercial

courses of modern training offered by E.M.I. Institutes-

the only Postal College which is part of a world-wide

Industrial Organisation.

Courses include:-

Mechanical Engineering Radio & Television Civil Engineering and Building Production Engineering & Management

Gen. Mech. Eng. Gen. Radio &T,V Eng. Civil Eng. Gen. Prod. Eng.

Diesel Engines Radio & T, V Servicing Building Construction Industrial Admin.

Refrigeration Radar Heating & Ventilating Works Management

Metallurgy Sound Recording Sanitary Eng. Production Planning

Workshop Practice Industrial Electronics Surveying Personnel Management

Maintenance Eng. Advanced Radio Clerk of Works Time & Motion Study

Machine Tools & Metrology P.M.G. Certificates Carpentry & Joinery Costing

Marine Eng. Radio Amateurs Licence Builders Clerks Office Practice

Draughtsmanship Electrical Engineering Automobile Engineering Aeronautical Engineering

Eng. Drawing & Design Gen. Elect. Eng. Gen. Motor Eng. Gen. Aero, Eng.

Tracing Installations & Wiring High Speed Oil Engines A.R.B. Licences

Jig & Tool Design I.E.E. Theory Garage Management A.P. M. Certificates

Also Examination Courses for:-General Certificate of Education, B.Sc. (Eng.), Common Preliminary, A.M.I.Mech.E., A.M.I.C.E., A.M.I.Struct.E.,

A.M.Brit.I.R.E., A.M.I.P,E,, A,M,I.I.A., A.M.I.M.I., A.M.I.H. M.R,San.l., A.M.I.San.E., A.M.I.Munc.E., A.M.I,E.D., A.M.S.E., 1.1.0.8.

Also CITY and GUILDS Certificates in Mechanical, Electrical, Aeronautical, Automobile, Telecommunications and Structural Engineering;

Refrigeration, Heating & Ventilation. Courses also provided for all branches of Commerce and Business Management.

Em I INSTITUTESassociated with

MARCONIPHONECOLUMBIA & Voice)

(HisMaster's

COURSESFROM

PER MONTH

-- POST NOWNoose send, without obligation, the above FREE book.

E.M.I. Institutes, Dept. 14443, Grove Park Road, Chiswick, London, W.4.

Subject(s) which interest me

Name

Address

IC 10G


164 NEWNES PRACTICAL ,MECHANICS January, 1953

THE

TECHNICAL SERVICES CO.SHRUBLAND WORKS,

BANSTEAD, SURREYTerms : Cash with Order. No C.O.D.All goods on 7 days approval against cash.POCKET VOLTMETER0-12 v., 0-240 v. AC/DC. Diameter. 21n.,depth lin. Brass case, moving ironsystem. For testing L.T. and H.T.batteries, house wiring, etc. Price, 19/ -each, post and packing 1/-.THERMOSTATType L.A.40. 1 a. 240 v. A.C. 21n. x lin. xin. For tropical fish tanks, etc. Price,

3/9 each, post 3d.THERMOSTATType BW/1. 3 amps., 250 v. A.C. Forcontrol of hot plates, vulcanisers. etc.,50-550 deg. F. Price, 15/6. Post 4d.ROOM THERMOSTATType PF. Wall mounting. 2 to 15 amps..250 v. A.C. 51n. x lfin. x 2in. deep. Intemp. ranges, 30/90, 40/100. 40/80, 60/100deg. F. Price, 1.2/0:0, Post 6d.AUTOMATIC FLASHERModel MIT. For signs, warning beacons.etc. up to a total load of 1 kW. on200/50 A.C. or 24 watts on 12 v. D.C. -3 seconds " On." 3 seconds " Off."2 7/16 in.x 11 in. a Tin. Price,81/0/2.post 6d.DRAWING AND INSTRUCTIONSFor making a 601n. x 30in. electricblanket from our heating cords. Price,2/6 Post tree. .

ASBESTOS HEATING CORDFully flexible for electric blankets andexperimental heating. Stocked in 15,25, 200, 400 ohms per yd. Price, 1/- peryd. post free.III -METALStandard thermometal ready cut to1S in. x 3,161n. a .0361n. For making smallthermostatic assemblies. Price, 6d.each, post free.ASBESTOS SLAG WOOLFor thermal insulation. Price, 1/ -per lb. or special price for our standard561b. sack.

VARNISHED CAMBRIC TAPEBias cut, width tin., thickness .0061n.In 72 yd. reels for coil insulation.Price. 6/3 per reel, post 3d.ELECTRIC MOTOR200/50 v. AC,DC, 40 w.. 8,000 r. p.m. (light).Suitable for hairdryers, blowers, drinkmixers, etc. Each motor Is brand newand by a well-known maker. Price,£1/17/6, Post 8d. Four blade fan to fitmotor spindle. 2/.. each, post 4d.MIRRORSCircular 211n. diameter. Brand new.Price, 8d. each, postage 4d.ELECTRIC BLANKETModel TS/1. Single heat, 60in. x 30In..100 w., 200,50 v. AC/DC. Complete withdetachable washable cover. Individuallyboxed and guaranteed 12 months.Price, 97/10/0. Poet free.ELECTRIC HAIRDRYER -Model TS/A. Moulded bakelite. Hotand cold air. 200/50 v. AC/DC. Weight28 ox.. Overall size Bin. An attractivewell balanced hairdryer. Fully guar-anteed 12 months. Price 83/11/0, postfree.Ask for details of our Easy Payment Termson Electrical Blankets and Hairdryers.ASBESTOS DISCSBin. diameter. Iin. thick. Ideal assoldering Iron rests. Price, 2)- per doz..post 6d.CONLAI UTATO It7 segment. 29/6410. O.D. x 29/641n. bore.Price, 2/- each, post 9d.CONVECTOR HEATER BODIESThese bodies are ideal for the construc-tion of attractive convector heaters.Stove enamelled in cream and green.All air vents are punched and only theinstallation of an element is required.Price. £1/510. carriage 2/6.CONVECTOR THERMOSTATModel C.S. For control of space heaters,low temperature ovens. To cover any40 deg. F. between 40 deg. and 120 deg. F.15 amps., 250 v. A.C. 411n. x Din. x Din.Price. 81.I5i0. post 6d.SILVER TIPPED CONTACTSCREWStin. x 7 B.A. brass. Fitted with conicalfine silver tip. For making up smallelectrical assemblies. Price, 6d. eachpost free.CERAMIC ELEMENT FORMERTUBELength 510., O.D. 7/161n., bore }in Spir-alled for resistance wires up to 30 s.w.g.30 t.p.t. For making immersion heatersup to 400 w. loatfing az for fish tanks.Price. 2)6 each, post 9d.THERMOSTATModel MB. For control of electric Im-mersion heaters up to 3 kW. range.90/190 deg. F., 15 amps., up to 250 v. A.C.Stem length Mo. Also for control ofplatens, baths, drying cabinets andovens. Price. 22/0/0, Post 9d.All our goods are Brand New and of !Bah

Quality.

Price a. 15. 0

E.D. Mk. III. 2.46RACING ENGINE.Specially designed for useas a diesel, glo-plug orspark ignition engine, the

.2.46 developsover j b.h.p. at14,000 r.p.m.plus. Totalweight 5 oz.

Price E4. 2. 6

DIESELSFO.RODYETT

E.D. .46 BABY.Specification : Bore R.P.M.9,000-12,000. Height lig in,Stroke in. cu. capacity 0.46 c.c.B.H.P. 0.04. Weight 1.4 oz. withtank. Length 2) in. Width II in.

Fuel Control placedat 30 deg. for easyaccess.

E.D. 3.46 c.c. Mk. IV.Developing 10,000 r.p.m. tha three -forty -six is one of the finest enginesfor control -line and stunt flying.Stroke 0.625 in.,height 3 in., width

1 in., length 4; in.,weight 5.1 oz.

Price E4. 2. 6

E.D. I c.c. Mark I (BEE).A compact little motor with anoverall height of 2/ in. Weight2) oz. Bore 0.437 in. staticthrust 12 oz, stroke 0.400r.p.m. 7,C00 plus.

Price E2. 17. 6

E.D. 2 c.c. COMPETITIONSPECIALGives 23 oz. static thrust and in-corporates vernier compressionadjustment. Height 3 in., width

ORDER THROUGH YOUR 1) in., length 4 in., weight 51 oz.

E.

MODEL SHOP Price E3. 5. 0

ELECTRONIC DEVELOPMENTS (SURREY) LTD.DEVELOPNENT ENGINEERS,1223 18.VILLIERS ROAD -KINGSTON -ON -THAMES. SURREY. ENGLAND.

NO MAN CAN KNOW TOOMUCH OF HIS PRODUCTFor the closescrutiny offractures or de-fects on sur-faces, cuttingedges, faultsin tools,cracks incastings, theUltra Lensis invaluable. BEttnia MADT

Revealing every detail with startlingexactness, highly magnified and bril-liantly illuminated in natural colourings, itpresents in many instances hitherto unsuspecteddata which can be used to advantage. Price [5.15.0 ,

complete in cardboard case with spare bulb, battery andtransparent measuring scale. Packed in luxury velvet Full particularslined case. I0/- extra. Postage and Packing 1/6. on request

THE LLTRA LENS COMPANT75, Finsbury Court, Finsbury Pavement, London, E.C.2

The Ultra Lens is an illuminated magnifier. It is a re-vealing eye of six actual diametrical magnifications

which brings out points of strength or weakness,and enables the most minute measure-

ments to be gauged accurately.Whether you are engaged in

manufacturing, buyi n g o r.7/ s, selling, it is an ally of

3/A' real value.No instru-ment you

can buywill more

quicklyjustify and

pay foritself.

MAKE MONEY -making casts

with VINAMOLDA grand spare -time occupation

WITHOUT any previous experience, you can massproduce any object from a chessman to a candlestick,statuette or model ship, in plaster, resin, concrete, etc.

. with " VINAMOLD," the flexible mould that givesthe BEST results. Easy to work, can be used over andover again. Needs NO special equipment, provides aprofitable and enjoyable spare -time occupation withminimum outlay." VINAMOLD " is the flexible mould employed byleading industries, including the big film studios. Tradeenquiries are invited.

Write far full details and instructions.

VINYL PRODUCTS LTD., (Dept. P.M.2). Rutter Hill, CARSHALTON.

GALPIN'SELECTRICAL STORES

408 HIGH SI., LEWISHAM, S.E.13Tel.: Lee Green 0309. Nr. Lewisham HospitalTERMS : CASH WITH ORDER. NO C.O.D.All goods sent on 7 days' approval against

cash.

EARLY CLOSING DAY THURSDAY

ELECTRIC LIGHT QUARTERLYTYPE CHECK METERS, all for 200/250volts A.0 50 cycles I phase, 5 amps load,17/6 each, post I/6: 10 amp, 21/- each,post 1/6 ; 20 amps load, 25,'- each, post1/6.RESISTANCE BOXES. Sub/Standard200 ohms, 37/6 each.:1 H.P. A.C. MOTORS, 1,425 r.p.m.110 volts only, OAS:- each.ROTARY TYPE DIMMER RESIS-TANCES, 80 ohms., to 10 amps, 15/ -each, carriage 2/-.

-MAINS TRANSFORMERS (NEW),input 200/250 volts in steps of 10 volts,output 350/0/350 volts 180 miamps' 4 volts4 amps, 5 volts 3 amps, 6.3 volts 4 amps,45/- each, post 1/6 ; another 350/0/350volts 180 m/amps, 6.3 volts 8 amps, 0/4/5volts 4 amps, 45/- each, post 1/6 ; another500/0/500 volts 150 amps, 4 volts 4 ampsC.T., 6.3 volts 4 amps, C.T., 5 volts 3 amps,47/6 each, post 1/6 ; another 425/0/425volts 160 m/amps, 6.3 volts 4 amps, C.T.twice 5 volts 3 amps,. 47/6 each, post 1/6.MAINS TRANSFORMERS (NEW),input 200/250 volts in steps of 10 volts,output 350/0/350 volts 300 m/amps, 6.3volts 8 amps twice, 4 volts 4 amps, 5 volts4 amps, 70/- each, carriage 3/6 ; ditto,450/0/450 volts 250 m/amps, 6.3 volts 8amps twice. 4 volts 4 amps, 5 volts 4 amps,70/- each, carriage 3/6 ; another, input asabove, output 500/0/500 volts 250 miamps,6.3 volts 8 amps twice, 6.3 volts 4 amps,4 volts 4 amps, 5 volts 4 amps. 75/-, carriage3/6. Another, wound to (electronic)specifications, 350/0/350 volts 250 miamps,4 volts 8 amps, 4 volts 4 amps, 6.3 volts 8amps, 0/2/6.3 volts 2 amps, 70/- each, car-riage paid ; another, input as above, output500/350/0/350/500 volts 250 m/amps, 6 3volts 6 amps, 0/2/6.3 volts 2 amps, 0/4/5volts 4 amps twice, 75/. each, carr. 3/6.MAINS TRANSFORMERS (NEW),suitable for spot welding, input 200/250volts, in steps of 10 volts, output suitablytapped for a combination of either 2/4/6/8/10or 12 volts 50/70 amps, 95/. each, carriage7/6.MAINS TRANSFORMERS (NEW),200/250 volts input, in steps of 10 volts,output, 0, 6, 12, 24 volts 6 amps, 42/6 each,post 1/6. Another as above but 10-12amps, 55/. each, post 1/6 ; another, asabove, but 25/30 amps, 75/- each, carriage3/6

'

another, input as above, output0/18/30/36 volts 6 amps, 47/6 each, post 1/6.EX -RADAR MAINS TRANSFORM-ERS, 230 volts input 50 cycles I phase,output 4,500/5,000 volts approx. 80 miamps,6.3 volts 2 amps, 4 volts I) amps, 2 volts2 amps, these transformers are new,immersed in oil, can be taken out of theoil and used as television transformersgiving output of 10 miamps, overall size oftransformers separately 5/in. x 41in. x 4in.and Sin. x Sin. x 2,1in., price 5/ each,carriage paid.EX -NAVAL ROTARY CONVERTERS,110 volts D.C. input, output 230 voltsA.C. 50 cycles, I phase, 250 watts capable of50% overload, weight 100 lb., price L10/10/ -each, carriage forward.MAINS TRANSFORMERS, 230 voltsinput, 150/0/150 volts 200 amps 6.3 volts8 amps, 5 volts 2 amps output, 23/- each.AUTO WOUND VOLTAGECHANGER TRANSFORMERS, tapped0/110/200/230 volts 350 watts, 55,'- each,post 1/6 ; as above, but 500 watts 70/ -each, carriage 3/6 ; as above, 200 watts,40/- each, post I/6.EX-U.S.A. W.D. ROTARY TRANS-FORMERS, 12 volts D.C., input 500 volts,50 miamps, 275 volts 100 m/amps D.C.output. Complete with smoothing switches,fuses, etc., as new, 17/6 each, carriage 2,16,can be run on 6 volts, giving half the statedoutput.MAINS TRANSFORMERS (By well-known makers). Input 100 and 230 volts,output 6 volts 11 amps twice, price 7/6each, post 1/- ; another 200/250 input,output 25 volt 4 amps C.T. 25/- each,carriage 1/6.MAINS TRANSFORMERS, 200/250 v.input, 400/0/400 v. 300 m/a 6.3 v. 8 a.,5 v. 3 a., 2 v. 3 a., 4 v. 2 amp twice at H.P.,82/6 each.ROTARY CONVERTORS, ex-R.A.F.,12 volts D.C. input, 230 volts 50 cycles 1

phase at 100/120 watts, L5/15/- each ;ditto, 24 volts D.C. input, 75/- each ; ditto,230 volts D.C. input, output as above,85/15/- each.



Ship Models

Efievorm or MODELS'By "MOTILUS"

"The Model Engineer" ExhibitionHAVING been a regular visitor to the

annual " Model Engineer " Exhibitionin London for more years than I care

to remember, I view some of the recentinnovations at this popular show with mixedfeelings. I am, however, entirely in, favourof one development that has emerged duringthe past two or three years: this is theintroduction of demonstration stands, wheremodel -makers can be- seen at work on theirhobby.

When I visited " The Model Engineer "Exhibition held last October I thought themodels entered for competition showed betterstandards than ever in this fascinating hobby.Coming, as they do, from all parts of Britainand from amateur craftsmen of ,all ages,these competition models give a goodimpression of what model -makers are doing.Added to this there are the loan models, allof them first-class. specimens of model -making, so that there is a greatinterest both experts and greenhorns.

Railway models, of course, are as big anattraction as ever and some beautiful workis being done on locomotive models. Anespecially fine example was Mr. J. I. Austen-

' Walton's 5in. gauge " Twin Sister " locomo-' tive, scale sin, to aft. (Fig. 1). This

o-6-oT L.M.S.R. class 2F model had theback of the cab removed during exhibition,so that the exquisite detail work inside thecab could be seen. The model was madealmost entirely in stainless steel and all thedetails were functional.

Winner of the Championship Cup in theSteam Locomotive Section was Mr. L. R.Raper, of Wakefield, for his 3kin. gaugefree-lance locomotive, to a scale of *in. to !ft.

(Fig. 2). This was based on a heaVy-dutyo-6-oST contractor's type locomotive.Another heavy-duty locomotive model, byMessrs. G. and P. Wheeler, was awarded asilver medal: this was a 5in. gauge 4-6-4THalton type locomotive, to a scale of tin. to

Ftg. 2.-Mr. L. R. Raper's Sin. gaugecontractor's type locomotive model, for which hewas awarded the Championship Cup for steam

locomotive models.aft. I must mention also Mr. F. Granger's5in. 'gauge locomotive, an o -6-o S.R." Vulcan," which has already hauled 3,50opassengers for the Hitchin Model EngineerClub without major overhaul. Bronze medalwinner, Mr. C. J. Hainge, is to be con-gratulated on his 3kin. gauge o76-oTL.M.S.R. class " 3F " locomotive, built fromscrap materials during service in H.M.Forces.

An extraordinarily large number ofexhibits were to be seen- in the various shipclasses, from tall, graceful sailing ships ofall periods (Fig. 3) to the tiny miniatures,and the inevitable expression of popular art,ships in bottles.

A championship winner that drew muchadmiration was a 5/16in. scale model of ascene with an Admiral's barge, which tookMr. C. A. Chapman four years to build.The barge, a non -working model, was plank -built throughout, despite its small size, andwas made from plans supplied by theAdmiralty. This excellent, detailed modelwas set on a sapphire blue sea as the focalpoint of a gay, tropical scene, such 'as mightbe found in the West Indies. The bargewas drawn up at the quayside, awaiting thereturn of the Admiral from a shore visit,and the figures of natives on the quay werebeautifully modelled. Baskets of tropicalfruit stood around, oranges, limes, pineapplesand bananas, each individual fruit separatelymade. A palm tree' curved gently at oneside made from 3,000 fitted pieces ! Asmall native boy perched on the quay wallwas eating an orange, the peel scattered abouthim. All these points aided the realisticatmosphere that pervaded this model scene.

Among the non -working sailing ships Iwas interested to find a model ship, SeaWitch, built by Mr. D. D. Bilimoria, ofBombay, the model showing a good degreeof- accuracy in its construction. I have sincelearned that Mr. Bilimoria is hon. treasurerof The Bombay Society of Model Engineers,which has been thriving since 1939 under theenergetic guidance of the chairman,Mr. M. P. Poison, A.S.E., F.R.S.A.,F.R.G:S. The Bombay Society was the firstin India and aims at the development ofmodel engineering and allied craftsmanship.

General engineering models were wellrepresented and I noticed a good proportionof well -made traction engines. A slightlymodified skin. scale Fowler showman'sengine won a silver medal for Mr. G. C.Taylor, who had put some very good detailand colour work into his model. Mr. A. L. G.Newman, bronze medal winner, had entered askin. scale Burrel traction engine, built to adesign by Mr. D. Bretherton, who used to bea traction engine designer for Messrs.Burrells. (Continued on page 170)

Fig. r.-Mr. 1. I. Austen-Walton's sin. gauge " Twin Sister" loco- Fig. 3.-Ancient and modern were both well represented in the _sailingmotive model. This has some exceptionally good detail work. Shio competi>ion entries at "The Model Engineer" Exhibition.


166 NEWNE5 PRACTICAL MECHANICS January, 1953

Push-button StarterGreuit

read with in-terest the reply to

K. Copping (Watford)in the September issue,regarding a push-buttonstarter circuit.

May I point out thatthis circuit could notoperate, as it would benecessary to push bothstop and start button atthe same time to ener-gise operating coil.Stop - button contactsshould normally beclosed and opened forde -energising operatingcoil.

I also think the ex-planation of operationis not clearly described, and is misleadinginasmuch as L2 and L3 operate the coil, notL, and L2.

In the remote circuit. both stop -buttonsshould normally be closed. I enclose acircuit, and I think the following informa-tion will answer the enquiry a little moreclearly.

With the operating coil D, A is connectedto L. B through overload trip to stopbutton G, which is normally closed.Through the link to start button 2, froci2 to F on moving contacts. Start buttonis connected to L2.

When H is pressed, D is energised, short-ing out F points, and taking over from H. Hcan now be open circuited. When G is de-pressed the coil circuit is open and operatingcoil de -energised. ----W. J. DOI.AN (Waltham -stow).

[It was intended that the lines L L2, andL3 should be numbered from the bottominstead of the top of the diagram. How-ever, as shown, we agree that the coil issupplied from the lines L2 and L3 and not L,and L2.

We agree that both " stop" push-buttonswitches should normally be closed. Asyou will, no doubt, observe, the four push-button switches have been correctly shown,apart from the fact that the contacts of the" stop" push-button switches have beenshown in the pressed position. You willnote that the position of the buttons

LETTERSrHE EDITOR

The Editor does not necessarily agreewith the views of his correspondents.

attached to the movingcontacts of the push-but-ton switches indicatesthat pressure on _thesebutt o n s opens the"stop" push -buttons andcloses the " start" push-buttons correctly. Actu-ally the contacts of the" stop " bush -buttonswere shown closed on theoriginal diagram, butwere accidentally alteredslightly when the drawingwas prepared for repro-duction.

The diagram whichyou have for w ard e

Moving Kconta,,1/4ctsinii____ contacts---,i\MAN-SMI I I ....--._Li

I

1

F Tomotor

Fromsupply

L3

J

Stan' Stop

fRoerinroev me o/tienk-1 / H 21control L-t7lipit_241.R(rfRemote control

Start Stop

Push-button starter circuit corrected diagram.

appears to indicate that pressure on the" start " push -buttons will open them ; infact, they have been shown as normallyclosed push -but tons .-ED .j

Interplanetary Space TravelSIR,-In the November issue V. A.

Milburn (" Interplanetary SpaceTravel ") contends that propulsion of a bodyacross free space does not seem possible.On the contrary-astonishing speeds may beattained in free space on a minimumamount of fuel. Perhaps the accompanyingdiagrams may help a little. If a point sourceof energy is tapped, the force released willradiate in all directions away from the pointsource as seen at " A." If the point sourceis placed at the position shown in " B " itwill represent the fuel in the combustionchamber situated in the tail of a rocket.Half the force radiated is wasted, as itescapes immediately, but the other half istrapped by the hollow hemisphere ; it is thishalf which does the work. If " B " is arocket in the earth's atmosphere, the rate ofexpansion must be increased until the airresistance and the force of gravity is over-come. The rocket will then ascend.

When the rocket is in free space as indi-cated in " C," it will be in a weightlesscondition ; there will be negligible gravityand no air resistance. " C" gives threeconsecutive positions of the point sourceradiating energy as the rocket is projected.

It will be seen that, apart from theminute power required for projectionacross free space, there would be anenormous build-up of speed even if thesame small rate of expansion was used.Indeed, it would seem that the now weight-less rocket could be projected at a speedequivalent to the expanding energy! A stag-gering thought, to say the least. Havingattained maximum velocity, the motor couldbe cut. and if one so desired the rocket wouldcruise at that speed for ever.

V. A. Milburn's suggestion of a body dis-integrating in free space, ignores the gravi-tational law that matter is attracted untomatter. Each speck has its own centre andforce of gravity, but is influenced by anylarger mass in its vicinity, thus the atomsof a space -ship would still remain together.It is imperative that this must be so, other-wise every single body in existence wouldhave disintegrated long ago.

The same writer's suggestion of " novision in space " warrants closer examina-tion. Light, paradoxically enough, is in-visible, and we are only aware of its presencewhen it strikes a body, such as the moon'sbarren surface or the molecules of ouratmosphere and, in turn, the retina of theeye. Whether the eye would still registerlight if it were placed in a vacuum is amatter of speculation. We do know itcan register light which has passed througha vacuum and enters the atmosphere. Thecontention that we should be unable to takeour bearings in a space -ship falls downimmediately we give our ship an internalatmosphere, which it must have for us toexist. This atmosphere automatically givesthe eye its familiar conditions of functioning,and we should be able to take our bearingswith the utmost clarity and steadiness ofvision.-W. ELLWOOD (Hatfield).

Mr. Ellwood's rocket propulsion diagrams.



Telephone : MUSEUM 9594

H. FRANKS58-60 NEW OXFORD STREET

LONDON, W.C.1

One Minute from TottenhamCourt Road Station

High quality ex-A.M. VACUUMPUMPS, size 6in. x 41n. x 41n. approx.Flange mounting, weight 51b., splineshaft-2in: long, lin. diameter ; needs -

a. h.p. motor to drive samo. Price37'6 each.

MINIATURE IMPULSE MOTORSmade by " Gents size 3 x 2 x 11155.,suitable for, operating models,.switches, etc., operates off 4/6v.a.c./d.c. and is very powerful for its'size. Price 8/6 each. post paid.

SYNCHRONOUS CLOCK UNITS:Self-starting, 200-250v: a.c. 50 cycle,fitted Sangamo motors consumption21, watts, size 21in. diam. ain. deepgeared 1 rev. 60 mins. friction reset.Ideal movements for electric clocks.With gear -train and 5in. hands. Price2216 each post paid.

STEP-DOWN TRANSFORMERS, in-put 230 . 50 cys. Output I2v. 8amps. Price 28/- each, post paid.

STEP-DOWN, Input 200/250v. 50 cycles.Output -tapped, 8. 16, 24, 32v. 15 amps.Price 23.7.6 each, carr. paid.

PRESSURE Operated SWITCHES,comprising a diaphragm unit coupledto switch, ideal for compressors,etc. 3/6 each.ASTROGRAPH UNITS, Mk. 1A.14/- - each.

SANGAMO MOTOR UNITS, MODEL7, final speed 1 rev. 24 hrs. 200/250v.am. 50 cycles. 27/6 each.

SANGAMO MOTOR UNITS, MODEL7, final speed 1 rev. per 7 days. 200/250v. a.c. 50 cycles. 30/- each.'

Ex -Air -Min. GEAR PUMPS. TypeRFP/1, made by Rolls Royce, sizeapprox. 6 x 51 x 51n. Price 80/- each,post paid.

HOUR METERS, 200-250v. am. 50cycles, 1/10th to 10,000 hrs. recording ;ideal for life testing, process timing,etc., 42/6 each.

SLIDING RESISTANCES, Enclosedtype 20 OHMS 2.3 amp. Price 22/6each.

VARIABLE RHEOSTATS with screwthread control, 71 OHMS 4 amp., allnew unused. Price 22/8. post paid.

VARIABLE RHEOSTATS fitted ver-nier control. 50 OHMS. 1 amp., allnew unused. Price 151- each, postPaid.

ROTARY RHEOSTATS. 11 OHMS5 6 amps. Price 12/- each, post paid.Y ItO POWER UNITS, fitted 24v.motor and gear box assembly. givingtwo speeds, approx. 5 r.p.m. and 200r.p.m. Size 51n. x 5in. x 3in. in metalbox. Price 42i6 each.

SLIDING RESISTANCES. 3.4 OHMS12 amps. Price 22/8 each, post paid.

SYNCHRONOUS MOTORS. 200!DOv.a.c. 50 eyes. with gear -trains. Finalspeed 1 rev. per hour. Ex -TimeOperated Units by well-knownmakers, size 31 x 31 x 3. Price 21'6,post paid.

DITTO 2 revs. per hour. Size 35 x.3 x31. Price 16'6, post paid.

RANGE FINDERS, type F.T.37.80 centimetre. These are made underBarr and Stroud licence In Canada,as new in transit case, less tripod.ideal for surveying etc., £15 each,

12 volt KLAXON HORNS, all new18/6 each.AIR THERMOMETERS, mercuryin steel, transmitting type, Mk. IL35 deg. to 55 deg. Cent. Ideal forlaboratory use, hot houses. etc.27/8 each.STAINLESS STEEL AERIAL WIRE,gauge 7/015 in 1,600 foot reel. Price40/- per reel.

TANK PERISCOPES, fitted two opti-cal prisms, size 51 x llins., overalllength dins., width 61 ins., depth llins.New in original cartons. Price 12/6each.

CLOCKWORK MOVEMENTS fittedVENEER " Escapement, runs 10

hours one full wind, final speed 1rev. 75 secs. Price 3/- each P.P.

SOUND POWERED TELEPHONEHANDSETS, type A.P13220, ready tooperate- when - connected- together,suitable for interior telephones, etc;No batteries needed. Price per pair,'32/6, post paid.

" STANCOR," U.S.A. 2.5 X.V.A. 50/60cycle auto -transformers. Input, 115/250v. Output, 110v. Completelyshrouded.' £11 each.

COLD CATHODE RELAY UNITSfitted two S.T.C.'cold cathode tubes,No. G240/2D. two Siemens high speedrelays 1.700/1,700 ohms, size of unit.approx. 6 x 7 x 4in. Price 23.2.6 each;

ELLIOTT MAGNETIC RELAYSTYPE II, coil res. ± 100 ohms. Opera-ting current, low contact 230 Micro -amps, high, contact 378 microamps,totally eneleSed in metal case, 9 x41 x 41n. 24 cacti.

FULL MAILING LIST PRICE 6d.

The Schoolboys' Exhibitionis coming again in January

If you havea camera andlive anywherenear Londonduring theholidays come and learn how you can develop your films in daylightand make your own prints.

PRACTICAL DEMONSTRATIONS-AT WHICH YOU CAN HELP -WILL BE GIVEN ALL DAY LONG

Everything connected with print -making clearly shown andexplained. You will be allowed to do some of the work yourselfunder the guidance of photographic experts. Don't miss thisopportunity. It's going to help you quite a lot.

Horticultural Hall,Westminster, S.W

OPENS DEC. 31CLOSES JAN. 10

Photography explained and made simple by-

JOHNSONS OF HENDON LTD.

Come to Classic for AllYour Tape Recording

RequirementsTAPE DECKS, TAPE EQUIPMENT, COMPONENTS, ANDCOMPLETE TAPE RECORDERS, AVAILABLE FROM STOCK.

Agents fors. d. s. d.

Wearite Tape Decks 35 0 0 Bradmatic Plate Coil ... 9 0Bradmatic Tape Desk 42 0 0 Bradmatic M/U Screens 4 0

Truvox Tape Desk... 23 2 0 Bradmatic Guide Pillars 5 0

Lane Tape Desk ... 16 10 0 Bradmatic 6 RP Heads... 75 0

Simon 2B 60 0 0 Bradmatic 5 RP Heads 65 0

Scophony 65 0 0 Bradmatic 5E Erase Head 65 0Ferrograph 79 10 0 Spare Spools (600ft.) ... 4 6

C.J.R. Portable ... 119 10 0 Spare Spools (1,200ft.)... 6 6

Qualtape Recorder... 16 16 0 Tapes, G.E.C. 35 0Bradmatic Circuits... 5 0 Tapes, Scotch Boy 35 0

Bradmatic Osc. Coil 9 0 Tapes, E.M.I. 35 0

Hire Purchase and Credit Sales Facilities Available

CLASSIC ELECTRICAL Co., Ltd."The Hi-Fi Television Specialists'"

364, Lower Addiscombe Road,Croydon, Surrey ADD. 6061-6062

WILCO ELECTRONICSLOW VOLTAGE CIRCUIT TESTER. -A self-contained unit for making a completeand rapid check of the generator -battery'circuit of a vehicle. Battery voltage, reg-ulator and cut -oat settings and generatorperformance can all be easily determined..American made. Complete with instructionbook. 25.10.0. Post 2/-.VOLTMETERS. -=-0-300 A.C. Moving Iron31in. Flush or Surface Type. 25/- ; 0-20,21n. Flush Moving Coil, 733 ; 0-40. tin. FlushM.C., 1013; post 1!-_._'MOVING -COIL METER with 1 M/A.movement, 21in. flush, rectifier type, scaled0/100 volts A.C. ' Resistance 100 k.' ohms.A very -useful basic' meter. 30/- post free.PORTABLE TEST METER. Just thejob' for the' home Constructor, in neat ease,61n. a 5in. x 41n., reading 1.5, a 150 volts, 6and 60 m/a. D.C., 5 k. and 25 k. ohms. 37/6.

THERMOSTAT. -For frost protection,on at 34 deg. F.. off at 49, deg. F., 11 amps.at 2.50 volts, adjustable.: 4/6, post 8(1.THERMOSTAT. -Bimetal type in sealedglass tuba, 2fin.-x lin. 30 deg. Cent. Ideal

-for-Aquariums,-Waa and Oil Baths, GlUepots,etc. Will control 1 amp. at 240 v., SI-, postTHERMOSTAT.-Satchwell 12in. stem,

. 0/253v. A.C./D.C., 15 amps. A.C., .1 amp. D.C.,10 to 90 deg. Cent., 35/-, Post 14PRESSURE UNIT ILIK.23/AP.-61n. x4in. x 3in., contains a small compressoroperated by a 27 volt D.C. motor withswitches, fuse, indicator lamp, 10ft. of air

-line and 21ft of twin flex in a flexible tubing,etc. American made. Brand new. Only45/-. post 2;6.POWER MICROPHONE INSERTS.-'Truvox. Diam. 2iin. x lin. post 6(1.THROAT MICROPHONF.S.-Americantwin -button type with strap lead and plug,5/-, post 8d.HEAD SET ADAPTOR. -High to lowimpedance. 2/6. post 6d.CLOCKWORK MECHANISM. -Precisionmade movement with contacts making andbreaking twice per second, can be used forswitching on and off lamps, etc. Brandnew in sound -proof cabinet with thermostattemperature control. Ideal for flashingsigns. 17/6, post 1/6.HEADLAMP complete with BatteryCase. Fits on forehead. Leaves both handsfree, 101-, post V-.VEEDER COUNTER 0-9999. lin. x tin, xlin. Very useful, 101-, post 6d.PHOTO FLOOD LAMPS. -1,000 watt,230 volts. 10/- Post 1--.RESISTANCE MATS. -Make ideal heatingmats for Aquariums, Photographic solu-tions. Print dryers. etc. Mains voltage,150 or 620 watts. Black heat, size 10in. x 6in.2/6, post free.

RODS.-12in. long, lin. diameter.Any number of sections can be fitted to-gether. 2/6 dozen, 6/- for 3 dozen, 11/- halfgross. 20/- gross. £8 per 1,000.SLOW MOTION DIALS.-6in. Scaled0-100, reduction 200 to 1 or direct, ideal forwavemeters, signal generators, etc. Ourprice, while they last, 5S. post II-.FLASHING SWITCH UNIT with 6contacts. Full rotation 60 seconds, operatedby a Sangamo Synchronous Motor. 230volts A.C. 2 watts. In metal case, ain. x2lin- a 211n. 151-, post 1/-.ACFIL PUMPS. --These pumps enableyou to fill all accumulators on the benchwith the carboy at floor level. Brand new,only -311/-. post 2/-.INTERESTED IN FISHING 7 -Then, sendfor one of our tapered whip aerials andmake yourself a fine rod worth pounds.Consists of three tubular steel, seamlesscopper plated sections, 4ft. long, which screwinto each other and are well finished,- 7/6.carriage 2/-. (Eire. 6/6)CUTTER HEADS.-" Recording " highimpedance. A bargain at 55/-. post 1/-.CUTTER STYLI', 8/- per doz., largequantity available at special rates.PORTABLE ELECTRIC BLOWERS. -220/230 volts, 220 watts. Completely en-closed, 8ft. flexible hose and nozzle. 7 yds.C.T.S. Flex. Many uses where clean, dryair is required. 27/10/-.ACCUMULATOR CHARGERS in blackcrackle case with fuses and meter, 6 and12'volts at 4 amps. Bargain Price, 24/19/6.Pkg. and carr., 5/-.

ELF " CIRCUIT BREAKER, 220 volts,2 amps., size 3M. round. 10.8, post 1/-.STUART PUMPS. -230 volt A.C. motor,will lift 400 gals, per hour 15 ft.. 211/15/-.carriage 7/6.KLAXON GEARED MOTORS No.11(58B3 -W7. Torque 15 lbs. ins. 175 r.p.m.,220/240 v. A.C. Induction type £10 each.24 -VOLT D.C. MOTORS with double endedshaft 21n. x 31n., 8/6. post 11-. -

TWIN FLEX, in black braided covering,approx. 25 -yd. coils. 7/6. post 1/-.INTERCOM. CABINETS. -Solid back,polished all round, 151in. x Olin. x 6fin..with two 4in, circular frets for speakersand cut-out for control panel, 25/-. post 3/8.HAND TELEPHONE. Brand new withcord. 151- each, post 1/6.INERT CELLS, 11 volts. size tin, x 2in. a5in. Just add water, last for years. idealfor Electric Bells, Telephones, Models, etc.Only 2/- each, post and pkg. 1/-, or 4 for101- post free.MASTS, TELESCOPIC. Extending to12ft. in 7 sections. 15/6, post 1/6.

These are just a few of the items In ourstocks. Send 6(1. in stamps for compre-hensive list giving full details of Poten-tiometers, Condensers, Resistors, Tele-phone Kcy Switches, Rectifiers, etc.

204 LOWER ADDISCOMBE RD.,CROYDON



A CUT ABOVE THE RESTSEARCH where you will, you won't find better knivesthan X-acto.The blades are made from the finest surgical steel avail-able, ground to a really keen cutting edge ; each shapedesigned to do a specific cutting job and to do it well.The perfectly balanced handles lock the blades firmly ina positive grip yet they let go at a twist of the sleeve.X-acto puts snore skill at your fingertips for there's

an X-acto blade for every cutting jobObtainable only .front X-acto Stockists, No. 5 KNIFE

6'6 completeNo. 2 KNIFE

3'6 complete

No. I KNIFE

3/- complete

et° Blades sold in packets from 2;'6 for five; Gouges 5,- for five; Routers 4;- for four.

IFWrite for illustrated folder showing the complete range of X-acto

Tool Kits and Tools to:-

TRI X LTD., (Dept. A), II Old Burlington Street, London W.I.

BENNETT COLLEGE can help you to

success through personal postal tuitionTHOUSANDS OF MEN in important

positions were once students of TheBennett College. They owe their success toPersonal Postal Tuition-The Bennett Collegeway. You have the same chance to qualify for a

fine career, higher pay and social standing.

SEND TODAY for a free prospectus onyour subject. just choose your course, fill inthe coupon and post it

To THE BENNETT COLLEGE, Dept. A.76, SHEFFIELD

Please send me free your prospectus on :

SUBJECT

NAME

ADDRESS

AGE (lf under 21)PLEASE WRITE IN BLOCK LETTERS

One of these courses will lead

Accountancy ExamsAuditingBook-keepingCommerical ArithmeticCostingModern Business Methods

AgricultureArchitectureAircraft MaintenanceBuildingCarpentryChemistryCivil EngineeringDiesel EnginesDraughtsmanshipElectrical EngineeringElectric Wiring

ShorthandEnglishGeneral EducationGeographyJournalismLanguages

to your advancement

Engineering DrawingsI.C. EnginesMachine DesignMechanical EngineeringMotor EngineeringPlumbingPower Station EngineeringPress Tool WorkQuantity SurveyingRadio EngineeringRoad Making

MathematicsPublic SpeakingPolice SubjectsSecretarial ExamsShort Story Writing

SanitationSheet Metal WorkSteam EngineeringSurveying

TelecommunicationsTextilesWireless Telegraphy

Works ManagementWorkshop Practiceand many other;

GENERAL CERTIFICATE OF EDUCATION : R.S.A. EXAMS.


January, 1953

SIR,-I found the letter about interplanet-ary space travel from your correspond-

ent, V. A. Milburn, very interesting ; hisideas show thought, even if they are a bitunorthodox or revolutionary to the ordinaryman. I have no quarrel with the maintrend of his thoughts, as I understandthem (that is not to say I accept them ! ),.but there" is one part which I feel is abso-lutely "off the rails," and, no doubt, youwill receive more than one letter on thisparticular point.

The point at issue is the statement in thefifth paragraph that a traveller in space couldnot see to take bearings because of theabsence of a medium through which toSurely light does not need a medium.:through which to travel? And if it does, thenthat medium (whatever it is) must exist be-cause we do, -in actual fact, see through it.The point in the next paragraph that we seeother planets through atmospheres doesnot prove the following statement: "Thuswe see through or across the interveningspace." If there is a complete void betweenatmospheres through which light cannottravel, then can V. A. Milburn explain justhow light gets from one atmosphere toanother? And further, can he explain howwe see other heavenlybodies which have noatmosphere at all, orwhich is frozen solid?

And how is it thatwe can see objects inan evacuated jar onour own earth-truewe cannot reach aperfect void, but ifsome sort of mediumis required to trans-mit light, then mightnot its " thinningdown " to almostvanishing point in theevacuated space resultin at least a dimmingor " ghosting " ofour perception, of ob-jects within it ?

Let us supposethat we could " seeacross the intervening space " if we lookthrough atmospheres." Then surely thespace traveller will still see, because he willhave at least some sort of atmosphere insidehis space -ship, or his space-suit-after all,he's got to breathe! And I can't imaginehim undertaking that journey with anoxygen mask only over his face, and hiseyes uncovered!

Finally, I would like to ask your core-spondent for more details about his theoryof a hollow sphere shrinking at a terrificrate. Does he mean that the entire Universeis the sphere? If so, why is it shrinking ?What makes it do so ? Do things withinit shrink, too ? Or will they be overtakenby the shrinking sphere, and what happensto them then ? I would like to assure yourcorrespondent, quite sincerely, that I'm nottrying to be facetious at his expense, or topull him to pieces-it's merely that I'mvoicing my first natural reactions to histheory-after all, he may be right!-C. S.WEDLOCK (Harley).

Novel Method of Screw CuttingSIR,-Using the top of a circular saw and

placing two small parallel strips of woodon a pivot, to act as guides, at right anglesto the direction of the saw, I find that itis possible to cut screw threads of any pitch,left hand or right hand, by simply varyingthe angle of the guides in relation to thesaw.

The rod to be' threaded is placed in theguides as shown in the sketch, and fed to


Wood stock

-Guides

End view of set-up

Right : Mr. H. A.D. Joseph's methodof cutting screw -threads on wood bymeans of a circular

saw.

Below : A view ofhis first test piece,the finish of whichcould probably be im-proved with practice.

169

Left handthread

the saw in a rotary forward motion. Thesaw blade keys itself in its own cut and pro-ceeds in the direction given it by the angleof the guides. The accompanying photo-graph shows the first test piece tried out.-H. A. D. JOSEPH (Epsom).

Making a Plaster CorniceSIR,-In the November issue N. J. Wilson

gets some advice about his plastercornice which, in my opinion, is not strictlycorrect.

The drawings given by J. Heelas arevery good, except that the nib rail is notrequired on the ceiling. The nib of thehorse (or mould) will bear on the ceilingand must be held tight to it while " run-ning " the cornice.

The amount of plaster of paris advised byMr. Heelas is not enough. The proper mixfor a good job would be approximately threeof lime putty and one of the plaster. Instal-ling a cornice by this method is really ajob for a skilled man, and if Mr. Wilson isnot one: he would be advised to buy acornice made up in lengths from one of thefirms engaged in its manufacture. He wouldonly have to nail it in position and make upthe joints and mitres by hand.-A. BOYLAND(Celbridge, Co. Kildare).

Boiler for Model Steam LaunchSIR,-I am about to build the Model

Steam Launch described in the Augustand September issues; but find that nodimensions are given for the boiler. Can you

Woodstock

Pivot fixed thro'hole in fable

Guides

Saw table

supply these please?-J. M. DOUBLEDAY(Silloth).

[Dimensions for the boiler are asfallow Length ' 4in. ; dia.. in. It hasend plates sunk in and soldered. The materialis 24g. sheet copper rolled to form a cylin-der and lap jointed. The end plates are of22g. copper. Sheet iron of 22g. is usedfor the boiler casing.-ED.]

Golf -bag " Caddie Cart"SIR,-As a new reader of your journal

PRACTICAL MECHANICS, which I thinkis one of the most interesting journals of itskind published, I would like to make use ofyour query service.

Will you kindly inform me if you haveever published the constructional details fora golf -bag " caddie cart " made up fromaluminium tubing, and if so, could you tellwhere I can obtain details of same ?-J. G. S.COATES (Middlesbrough).

[Ire invite readers' suggestions on thissubject.-ED.

AN ELECTRIC FLOORPOLISHER

(Continued from page 548)

drawn down through the stem of the handleand out through another rubber grommetat the lower end and taken to the motor.Here again the earth wire should be connectedto a convenient screw on the body of themotor. The handle itself is pivoted to themotor by a iin. mild steel spindle passingthrough a double eared bracket bolted to thetwo lower motor feet. A light spring clipkeeps the handle in a vertical position whenthe machine is not in use.

The rubber flex should be of ample lengthand is wound, when not in use, on a pair ofdin. round mild steel cleats brazed to thestern of the handle.

OperationWhen using the finished machine the

polish should be sparingly applied to thefloor and allowed to partially dry. Thepolisher is then switched on and workedwith a " to and fro " motion over the waxedsurface. The pads, when dirty, may beremoved and washed in warm soapy water. Itis; as stated before, a great advantage tohavr at least one spare set of pads.


170

The Modelcraft HandbookTHE handbook lists all the products of

Modelcraft, Ltd., 77(s), Grosvenor Road,London, and these include plans, com-plete kits, separate accessories and wood -packs for, many types of model. Plans andkits are supplied for making lineside modelsfor use with gauge oo layouts, road trans-port models, modern and period houses,many types of old-time sailing craft, sailingboats, yachts and power boats, Royal Navyand Merchant vessels, and for aircraft, cars,weapons of war, etc. The booklet is illus-trated throughout with photographs anddetailed sketches and every item is priced.The Modelcraft Handbook may be obtainedfrom the above address, price Ts. 6d.

Atomic Blade KeenerTHE purpose of this new and extremely

simple device is to re -sharpen the bluntedges of used razor blades, and we are givento understand that some- of its users have

NEWNES PRACTICAL MECHANICS January, 1953

The Korting Keener in use.had months of use from one ordinary double-edged razor blade. The Keener is non-abrasive, does not wear out and does not wear

away the blade. It is used dry and requiresno oil, paste or water; it is finished in whiteplastic. The price, including tax, is 3s. 6d.,plus 6d. postage, and it may be obtained fromthe makers, Korving, Ltd., 54, FrederickStreet, London, W.C.1.

Multicore Silver SolderWITH the co-operation of Johnson

Matthey, of Hatton Garden, London,E.C.t, Ersin Multicore Solder is nowavailable in Comsol alloy. This tin/lead/

- silver solder has a melting point of nearly30o deg. C., which is 113 deg. C. above themelting point of the usual tin/lead alloys.

Ersin Multicore Comsol solder is normallysupplied in 16 S.W.G. and is intended forsoldering processes where components arelikely to be subjected to excessive workingtemperatures. Projector lamps, some typesof electric motors, etc., are examples. It isbelieved that Comsol may also be suitable foruse on radio and electrical equipment beingsubjected to sub -zero temperatures, althoughresearch into this is at present still proceed-ing.

Generally, this new product will be sup- .

plied direct to manufacturers, the price beingslightly less than that charged for ErsinMulticore 6o/4o alloy.

BOOKS REVIEWEDOur Neighbour Worlds. By V. A. Firsoff,

M.A. Published by Hutchinson'sScientific and Technical Publications.336 pages. Price 25s. net.THE author is a fully qualified and practical

astronomer but he writes in a strain thatthe layman can understand. He uses themost up-to-date knowledge of the solar systemto make a survey which is used as a basis forhis researches into the problem of inter-planetary travel, a fairly imminent explorationin which he firmly believes. He delves bothinto the fields of knowledge and of specu-lation, but it is always made clear whether ornot it is fact that is being presented. This isnot an astronomical treatise, nor is it a fantasyof the pseudo -scientific kind : it is an attemptto add the rapidly expanding science of spaceflight to known astronomical information andpresent a few ideas of the prospects. Mathe-matical formulae have been deleted from thebody of the book and put all together in anappendix. The illustrations comprise bothastro-photographs and drawings and photo-graphs of astronomical apparatus ; art paperis used throughout.

The Cyclemotor Manual. By the Staffof " Motor Cycling." Published byTemple Press, Ltd. 107 pages. Price6s. net.THE purpose of this book is to answer the

questions likely to be asked by the newowner or prospective purchaser of an auxiliarymotor. It deals with running costs, legalformalities and routine maintenance, and givesall the technical knowledge needed by thedriver. Units are dealt with individually andeach engine is illustrated by a special " ex-ploded " drawing showing assembly. A fulldescription of the unit and instructions for itsmaintenance are included in the text, and thereis a special chapter devoted to the location andcure of mechanical troubles. There are alsochapters on basic principles and on riding amotor -assisted bicycle. The book is compiledby the staff of " Motor Cycling," who haveridden most cyclemotors available in thiscountry and write from experience.

Motor -cycle Maintenance and RepairSeries : Velocette Motor -cycles, byR. W. Burgess : The J.A.P. Engine, by

A. C. Fenner and W. Phillips. Pub-lished by C. Arthur Pearson, Ltd.Price 6s. net each volume.

'INCLUDED in the well-known Motor -1 cycle Maintenance and Repair Series,these volumes provide owners and repairerswith a guide to the Velocette motor -cycle andthe J.A.P. engine respectively. All the Velo-cette models from 1933 are dealt with, andchapters are included on routine runningadjustments, K and M four-stroke and GTPtwo-stroke engines, clutch and gearbox,carburettors, wheels, chains and brakes, forks,electrical equipment, and a separate chapterdealing with the LE model. In addition tophotographs, many sectional and " exploded "diagrams are included.

The J.A.P. handbook deals with the motor-cycle -type engines, racing units and industrialtypes, and a specialist contribution is includedby W. H. Phillips, Harringay Speedway teammanager and mechanical adviser, on tuningand overhauling racing engines. The book iswell illustrated throughout and containschapters on overhaul, lubricating systems,carburettors, magnetos and a full index.

Motor Cycling Road Tests. Publishedby Temple Press, Ltd. Price 5s. net.THIS first edition of road tests is comprised

of reports published in "Motor Cycling "during the past four years. These reportsanswer the motor -cyclist's questions aboutspeed, handling, performance and economy,and give much -needed information to theprospective purchaser of a new machine. Thisbooklet is illustrated throughout with photo-graphs and drawings, and at the end are 12specially drawn cutaway diagrams to supple-ment the test report in the text.

The Ramsgate and District Model ClubEMBERS of the above club recently

1V1 exhibited at the neighbouring town ofBroadstairs, and at the Ramsgate TradesExhibition, their model of Ramsgate Harbour.

This 32ft. to the inch scale model wasdescribed by the local press as the " piecede resistance." It was certainly admired bythousands of people, and the club must have

obtained a great deal of publicity throughthis project.

Various delicately executed models werealso exhibited by individual members.

A cordial invitation is extended to allinterested persons and fellow modellers, atthe club's premises-Princes Street, Ramsgate.

MR. E. CHURCH, Hon. Secretary, 14, St.Mildred's Avenue, Ramsgate, Kent.

New Ideas ExhibitionTHE Modern Inventions and New Ideas :

Exhibitions will be held at the CentralHall, Westminster, S.W. t, from February18th to 28th, 1953. Promoters, MoorlandExhibition Enterprises.

H.R.H. The Duke of Edinburgh hasextended his patronage to this exhibition, anencouragement which inventors will greatlyappreciate.

It is planned to display inventors' prototypesin a setting of up-to-date equipment from themajor industries of this country, so stressingthe importance of new developments. Medalswill be awarded for meritorious inventionsshown. Inventors all over the country areinvited to participate in this, the first large-scale display of inventions in this countrysince 1939. Correspondence should beaddressed to :

GENERAL SECRETARY, Institute of Patentees,207-208, Abbey House, 2-8, Victoria Street,London, S.W.I.

THE WORLD OF MODELS(Continued from page 165)

Quite a large number of entries appearedin the aircraft sections. " General Crafts-manship " was well represented and therewere many interesting scenic and architecturalmodels.

Radio -controlled ModelsProbably the most attractive of the special

features was the marine tank and radio -control section. The interest in radio -controlled models naturally increases everyyear as more and more operations becomepossible under the direction of radio -control.,Several different types of ship models weredemonstrated here, 'as well as Mr. Tamplin'smodel Churchill tank, first seen at the 1951Exhibition, and modified and improved forthe 1952 demonstrations.'



There is somethingfor every modeller in

THE NEW

MODELCRAFTHANDBOOKTHE newest edition of

this valuable catalogueincludes many new plans,and the entire handbook hasbeen revised, extended andmodernised. It caters for avery wide range of interestsand ages. It also includes acash refund voucher value1/6 for spending on furtherModelcraft products. Sendpostal order for your copynow. Beautifully printedand generously illustrated.Post free -

1/6d

MODELCRAFT(77 L), GROSVENOR RD. LONDON, S.W.1

SPECIAL OFFERSMercury -operated Thermometers.Calibrated o -too Deg. Cen. Suppliedwith approx. 3oft. Capillary Tubing.New and guaranteed. 201- each, Post &Pkg., 1/6.Engine Driven Generators, 12 volt at500 watts, 82/6, Carriage 5/-.24 volt at r,000 watts, 30/-, Carriage 5/,Suitable for Electro-plating, etc.Limited quantity of 2,000 watt typesavailable which are suitable for welding,etc.Fractional H.P. Motors, approx. I/3othH.P., converted R.A.F. motors. Idealfor small Buffers, etc. 200-250 voltsA.C./D.C., 3,000 R.P.M. Price so/ -each, Post & Pkg. 2/-.Similar. Motors to the above, but r/8thH.P. and suitable for small lathes, etc.35/- each, Post & Pkg. 5/-.Crompton Parkinson r/6th H.P.1,425 R.P.M. on resilient Mounting,23o volts A.C. Fitted with ThermalOverload Switch. Suitable for allFridges, Lathes, Drills, etc. AbsolutelyBrand New with our full guarantee.Price £5 each, Carriage 5/-.Reduction Geared Motors xixoth230 volts A.G. final Drive rzo R.P.M.Very powerful, New in cases, £4 each,Carriage 5/ --

Feathering Pumps and Motors Com-plete. This is a combined HydraulicSpur Gear Pump and 12 volt D.C. Motorcapable of delivering an oil pressure ofover too lbs. per sq. in. Few Only at30/- each, Carriage 3/6.Meters o-500 Microamp. sin. ScaleCalibrated o-500, tz/6 each, Post andPkg. 1/, Limited quantity for r monthonly.

Terms C.W.O. Satisfaction or MoneyBack Guarantee.

S.A.E. For List and all enquiries.

JEFFREY H. DAMN13, Church Road, Edgbaston,

Birmingham, is.OVERSEAS & TRADE ENQUIRIES

WELCOME.

STITAGNIN90ffif MEP

The Mole Wrench is a multi -purpose toolof tremendous gripping power. It stayslocked on the job with both hands

removed. Flick the release lever andit's off. Use it as a vice, wrench or aspliers -there's no end to its uses forthe handyman, technician and engineeralike.

Obtainable at your local Ironmonger.7in., 12/6. 10in., 1.5/ -

If any difficulty write for your supplier'saddress.iii

MMOLE £ SON LTD BIRMINGHAM 3

The "LANE" MICRO -LATHEI lin. Centre Height.filo. Between Centres.

Any Item sold separately.STOCK DELIVERY.

C. LANE & SON, Dairy Lane,

PRICE 410-3-2 (Carrirage4, 6age

extra -Ave)COUNTERSHAFT (lesslarge pulley), 12/410.

DRILL CHUCK, " 0 "Shank, 8/3.

ELECTRIC MOTOR, I

Ph. 230/25 V. I h p.Constant Speed, E5/0/0.

Neat Portable HomeWorkshop built from"LANE" components.Photo shows " LANE "Micro -lathe reducinggin. mild steel bar downto kin. IN ONE CUT.GENUINE REPEATABLE

PERFORMANCE.

2lin. x 4 Jaw Indep.Chuck, 38/6.

Houghton -le -Spring, Co. Durham

WIRING ACCESSORIES

1.044 Flat Twin TRS cable, £3. 3.029ditto, £4. 7.029 ditto, 286!6. MO yds.All sizes and types of TRS available.PVC cables. impervious to weather,oil, water, etc. 1.044 fiat twin, £2/1316.3.029 ditto, £311113. 7.029 ditto, 25116/9.Most sizes and types available. Ceilingroses, Did. Switches, 1/7i. 2 -way, 2/2.Lampholders, 10d. Junction boxes.1)3. Poultry Time -switches with 2timed circuits, £6/18. Weatherprooflamp fittings. 17/9. 24/32 v. Lightingplants. Press button start comp. withvoltage regulator and switchboard.Powered by JAP 4B Industrial engine,1,000 r.p.m. New, £321101-. All goods arenew and covered by our money backguarantee. Send for complete lists.

HUNT & CO.,STEPCOTE HILL, EXETER

110111116.11

GENERALCERTIFICATEOF EDUCATION EXAM.

THE KEY TO SUCCESS AND- - SECURITY

Essential to success in any walk of life.Whatever your age, you can now prepareat home for the important new GeneralCer t. of Education Exam. (you chooseYour own subjects) on " NO PASS -NOFEE " terms.SEND FOIL FREE 136 -PAGE BOOK

Full details of how you can obtain thisvaluable Certificate are given in our130 -page Guide -TREE and withoutobligation. Write to -day.11.T.I., 160, AVON DOUSE, 356-386,OXFORD STREET, LONDON, W.I.NO PASS -NO FEE

HIGHSTONE UTILITIESCrystal Sets.Our latest ModelIs a real radioreceiver. whichis fitted with apermanent crys-tal detector. Wh ynot have a set inyour own room ?12/6, post Eirl. DeLuxe Receiverin polished oakcabinet, MO.post 1/-.

Spare Permanent Detectors, 2/- 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/- a pair. postl 1-New Headphones, 10/- a pair. Balancedarmature type (very sensitive). 12/6 a pair.Both post 1/-. New. Single Earpieces,3/8. Bal. armature type. 4/6 ex-R.A.Fearpiece 2/8, post 4d. Headphones, ingood order, 6/- (better quality, 7/6). allpost V-. Headphones with moving coilmike, 15/-. Similar phones with throatmikes, 12/6, post 1/-. headphone Cords,1/3 a pair, post 3d. Replacement Bands.1/3, post 4d. Wire Bands, 6d.(All Headphones listed are suitable for111A0 with our Crystal Sets.'

Bel I ran sforniers.These guaranteedt ranslormers 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 9/-, post 8d. BELLS for use witheither the above or batteries, 6/8L post 6d.

Big Ben " Chimes. Housed in C: earnPlastic Case. Easily connected to giverwo-Note Chime from Front Door, andSingle Note from Rear, Operates from 6-9volt Batteries or Transformer (shownabove), 23/-, Post 1/-.Ex -MAX. 2 -valve (2 -volt) MicroplAmplifiers 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 and fitting instructions, 20/,post 2/-. Useful wooden box with part'tionsto hold amplifier, 2/- extra. Ditto, lessvalves, 10/-. One -valve amplifier, completewith valve. 10/6 post 1/6.Illand Microphones, with switch in bundleand lead. 4/6. Tanney, 6/-. Similar instru-ment, moving coil. 7/6, post 1)-.Sparking Plug Neon Testers with vest-pocket clip, 3/3, and with gauge 3/6, post 3d.S.B.C. Neon lodieator Lamps, for use onmains showing " side of switches,etc.. 3/6, Post 4d. Neon Indicator, completewith condenser (pencil type), with vest-pocket clip, indispensable for electricians,etc.. 7/6, post 5d.

SolderingIrons. Ournew stream-lined iron isfitted with

A Pencil Bit. 200/250 v. 50 watts, 11/6.post 8d. Standard Iron with adjustablebit. 200/250 v.. 60 watts, 13/6, Post 6d. IleavYDuty Iron, 150 watts 16/6, Post 8d. All partsreplaceable and fully guaranteed. SmallSoldering Irons, for use on gas, 1/4, post4,1. Resin -cored solder for easy soldering6d. packets or large reels 51-, post Ad.Microphones. -Just the thing for Im-promptu concerts, room to -room communi-cation, etc. Bakelite table model, 6/9Suspension type. 8/8. Post 6d. MikeButtons (carbon), Moving Coil, 4/6 :Transiforrners. 5/-. All post 4d. each.Rotary Transformers, 24 v. input ; Output1,230 v.,2 snap. in case with suppressors,eto..- easily converted to run as a highvoltage motor. 25/-, carr. Also 12 v.input ; Output 6 v., 5 amp. ; 153 v.. 10 inA. ;and 300 v.. 20,24i mA.. 22/6. carriaeeMorse Keys. -Standard -size keys wired towork Buzier or Lamp, 3/-. post 6d. Slightlysmaller' keys. 2:0. post 4d. BUZZEIts.3/9. or heavy derv, 4/6. Post 5d.Terminals, brass. 213A. mounted on etrip6d. pair. .0005 Airspaced Variable Con-densers, 216. post 4d. .00003 twin gang withtrimmers, 2/6, post 4d. 24 volt, 15 m,m.,31.E.S. Bulbs for model railways, etc.,11- each, 10/- doz., post 4d. Wander Plugs.Brass, 1/6 doz., post 4d. Fuses. -1 amp,I lin., packet of 10, 2r6 post fld. Also 150 mA.and 250 mA., same price Hydrometers.Standard Type 6,-. post 6d.Bargain Parcels of really useful equip-ment, containing Switches, Meters, Con-densers. Resistances. Pho es, etc., 101-,or double assortment. 17/6; treble 25/-.All carriage 2/, This country only.Field Intercommunication Sets, completewith ringing hand eenerator, bell, signallamp, morse key, relay, in strong metalcase with circuit diagram, 30/- each, carr.2/6; 57/6 pair, carr. Es-G.P.O. Tele-phone Twin Bells, with box, 5/-. post Fal.Telephone hand generator, with handle, 9/6.post 116 : Bell, 341, Post 6(1.Meters. 10 v., 21in. Rectifier (A.C.), inwooden carrying case, 14/6: 15 v., 2110.Mc.. 9/0 : 150 v.. 21n., m/c.. 10/- : 3.5 amp.,2in., T.C. 6/- 4 amp., 2lin. T.C.. incasewith switch, 9/6 ; 100 mA., 21n., m/c. 7/8 :

Meter Units containing 2-500 mlcroemp.movements, 7/.. post 11-.

All meters post extra.Money refunded if not completely satisfied.

HIGHSTONE UTILITIES68, New Wanslead, London, E.11.

Letters only.New Illustrated List sent on request with

lid, stamp and S.A E.


172 NEWNES PRACTICAL

THE `. FLUXITE QUINS.".AT WORK

Fluxifed iron ! Right heat !Lesson Three !

The solder's called humans.

Watch me.Touch the hit-on a flat,And it flows on like that.

For FLUXITE'S the secret, yousee.

For all SOLDERING work-you need FLUXITE SolderingPaste-the paste flux-with which even dirty metals are solderedand " tinned." For the jointing of lead-without solder ; andthe " running " of white metal bearings-without " tinning "the bearing. It is suitable for ALL METALS-exceptingALUMINIUM.

With Fluxite joints enn be " wiped"successfully that are impossible

by any other methodUsed for over 40 years in Government works and by leadingengineers and manufacturers. Of all Ironmongers-in tins,

from 1/- upwards. TO CYCLISTS ! For stronger wheels that will remain round

and true* here's a time -tested tip. Tie the spokes where they crosswith fine wire AND SOLDER. It's simple-with FLUXITE-butIMPORTANT.

FLUXITESOLDERING PASTE

A staunch Companion to Fluxite Soldering Fluid.

SIMPLIFIES ALL SOLDERINGWrite for Book on Me ART OF " SOFT" SOLDERING and for Leaflets onCASE -HARDENING STEEL and TEMPERING TOOLS with FLUXITE.

Also on WIPED JOINTS." Price lid. Each.FLUXITE LTD., Bermondsey Street, S.E.I

MECHANICS January, 1953

DAMAGESSPIRAL BLADE BAN DSAWS

THE 7 in. TYLOR MARVELwin cut Steel. Wood. Foam -rubber. Cork. Plastic, Aluminium. Lino.Leather, Hard Rubber. Fibre Board, etc. Cute smoothly in any directionwithout operator turning work. Requires I h.p. motor.

Overall lit. 191n. ; width, llin.; ht. under guides.glin. ; throat, Olin. Table. 61 in. x 7in. Pulleys givefinal saw speeds of 200. 400 and 750ft. per min.

Example cuttingrates with spiralblade: Dn. mildsteel black plate,31n. per minute:tin. cast Iron,31n. to .4in. perminute.

Machine, complete with 3 -speed pulleys and belt, flat andspiral blade guides, as illus-trated,

En°. 1245Carr. Pkg. 10'-o* Wales. Scotland 13/6. a

ALUMINIUM ALLOYDIE CAST "V" PULLEYSFor tin. belts, diam, 21In., 31-; 31n., 3,9:3tin., 4 6: 4in.. 5!-; 451n.. 511; 51m, 61-:Gin., 7 71n.. 10.-; Sin.. 11'-; tin., 12i6;loin., 15,-; 12 in.,

Please state borewhen ordering.

Postage.' 2 in . andSin. size. 6d.:41n. to 12 in., 9d. ;List of other sizes'free on request.

Illustratedleaflet freeon request.

GAMAGES, HOLBORN,

Less than HALF PRICE !FUSE BOARDSFor lighting Cir-cuits 15 amp, perway, 250 v. Strongsteel case. Blackfinish. Pruldedwith knock - outs.Vitreous porcelainfuse carriers. Doublepole (2 fuses perway). 3 -way. 91 xG x 41in.,

Past & 101-Packing, 2/3.

The FAMOUSGRANVILLE LATHES

on Easy Terms !311n. back geared, screw cutting centre lathe. 18in.between centres. Height of centres, 311n.. swing ingap, 10In. diameter, overall length of bed 34M..overall length of lathe, 411n., bore of headstockspindle tin. clearance.

Bench Model £40/14/3Pam ts of 55or 10 ans. Deposit and 18 monthly /6

Stand Model as illustrated (withougotor) 855:13:3.or 14 gns. Deposit and 12 piontillY

Payments of 75/-Countershaft. 25;17,6. Carr. extra outside van area.Combined Tool and Motor Car Accessories List Free.

LONDON, E.C.1. HOLBORN 8484.

EMI INSTITUTES

EXPERIMENTAL KIT

LEARN THE PRACTICAL WAYA specially prepared set of radio parts from which we teachyou, in your own home, the working of fundamental

, electronic circuits and bring you easily to the point whenyou can construct and service a radio set. Whether youare a student for an examination, starting a new hobby,intent upon a career in industry, or running your ownbusiness-this Course is intended for YOU-and may beyours at a very moderate cost. Available on Easy Terms.WE TEACH YOU: Basic Electronic Circuits (Amplifiers,Oscillators, Power Units, etc.) Complete Radio ReceiverTesting & Servicing.

POST IMMEDIATELY FOR FREE DETAILSTO: E.M.I. INSTITUTES, Dept. 144 KGrove Park Road, Chiswick, London, W.4

* Experimental Kits alsoform part of the follow-ing courses: Draughts-manship, Carpentry,Chemisty. Photography,Commercial Art, Etc.

INSTITUTESAssociated with

MARCONIPHONE

& HMVCOLUMBIA(His Master's Voice)

C



QUERIES andENQUIRIES

A stamped, addressed envelope, three pennystamps, and the query coupon from the currentissue, which appears on the inside of back cover,must be enclosed with every letter containing aquery. Every query and drawing which is sentmust bear 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.

I have a lens with which I hope to build acamera the rating is as follows, B & H

Ansix Type V a y in. (35mm.)f3.5. Please inform meof a scale in fractions of an inch and their equalin J. numbers, the smallest aperture being ! t6in.opening up to ,1 in.

(2) Could you inform me of a method of checkingthe speed of a shutter ?-A. D. Smith (Corsham).

\ GIVEN below are the diameters and stop num-bers for the t gin. (35mm.) lens.

There is no simple way of checking shutter speeds,except by comparing results of exposures made, simul-taneously, with another and reliable camera. The speedsof shutters vary considerably on different cameras forsimilar speed workings. I had two cameras, both withcompound shutters end Zeiss lenses ; the shutters had arange from a second to /25oth, yet the times on oneshutter were noticeably longer then the other.

The only reliable way to check would be to fit up arevolving drum, -making one revolution per second. Fixround the drum a band of sensitised film or bromidepaper. Make a box to fit on the back of the camera,light tight, containing an electric lamp. Point the lens,close up, at the film, start the drum revolving, fire theshutter, develop the film and the proportion that thelength of the fogged or blackened part of the film bearsto the whole length of it, or to the circumference of thedrum, will be the fraction of a second of the exposureThus, suppose the diameter of the drum is 12M., andthe circumference and film length 37in., if the foggedportion is I lin. in length the exposure will be, as nearlyas possible, 1/25th second. Obviously the job wouldhave to be done in the dark room and with a ruby lampfor general lighting. A number of exposures could bemade on the same film and it would not matter if thefogged portions overlapped, providing the lamp at theback of the camera was not very brilliant. The circum-ference and especially the revolution speed of the drumare very critical points.

Stop Sizes and f Numbers : Checking

Shutter Speeds(I)

Lens B & H, Type V, a gin., 35mm., /3.5.English Stop diameter diameter

Stop Number inches in millimetres122 06 1.6ft6 5/64 2.2fit i/13 3.2/8 11/64 4.38f6.5 7/32 5.3814.5 5/16 7.713.5 25/64 10.0

Restoring Pitted Red TilesT HAVE moved into a new house, the kitchen.1 floor of which is formed of red tiles. Thesewere covered with linoleum, and the action of themoisture trapped underneath has pitted thesurface of the tiles rather badly.

Can you tell me any method of bringing themback to a new condition ?-M. Oates (Halifax).VOU arc faced with a difficult problem but mightA find a treatment with coloured cement helpful.

The tiles should be thoroughly cleaned and moistened,especially in the pits.

A mixture of one part of cement with four partsof sand is coloured, when dry, with red iron oxide.The amount of oxide will depend on the exact shade ofthe tiles, and a little trial and error with a sample mixwill give you the proportion of colour to use for agood match with the tiles. The coloured concrete isthen pressed firmly into the damped pits on the tiles,and allowed to set for at least 48 hours before use.When the concrete is in a mastic condition after a fewhours it can be smoothed carefully with the finger,to give a fairly good surface.

An alternative suggestion is to use a floor paint,or lino paint, using this to fill in the pits, if the latterate not deep.

Patching Camera BellowsCAN you give me the formula for a flexible

paint to apply to camera belows to fill pin-holes Is there any such naint on the market, and

if so where can I buy it and what is its approximatecost ?-M. A. Davidson (Liverpool, 14).

THERE is no such thing as a really flexible paint, andthere is certainly no paint which, of itself, would

withstand the strain on it involved by the opening andclosing of camera bellows.

Fortunately, however, the trouble with your camerabellows is not very difficult to cure. The bellows merelyrequire careful patching over the pinholes with smallscraps of thin leather or rexine cloth. Take the camerainto a dark room. Open out the bellows extension fully.Place a low -wattage electric lamp inside the camera andswitch on the light. The disposition of the pinholeswill be seen at once. Cut out suitable fragments ofleather or rexine and stick them in position on thebellows with duroflex adhesive or seccotine. Verylikely the pinholes will have formed on the sharp cor-ners of the bellows. In this case, fresh corners will haveto be made from thin rexine or thin leather. These arethen fastened in position over the faulty corners, lightlyclipped for an hour or two whilst the adhesive sets, andthen, maybe, touched up with a little paint or colour tomatch up with the rest of the bellows. If the bellows,as a whole, are getting dry and are inclined to pinholefrequently, rub them over every other week or so with a

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

with their enquiries.

soft cloth saturated with castor oil. This will help tokeep the leather soft and to prevent it from cracking.

Reversible MirrorsTN the film " The House on 92nd Street " thel F.B.I. agents were shown making use of whatwas described as a " reversible mirror " which,if viewed from one direction, appeared as anordinary mirror but, from the other side, was likea sheet of plate glass. This device enabled the F.B.I.to take photographs of enemy agents withoutthemselves being observed. Will you kindly ad-vise me how this effect is achieved and the scienti-fic explanation ; and whether it is possible to pur-chase this type of glass commercially in thiscountry and, if so, the approximate price and thename of the manufacturers. -D. F. Ecclestone(Suffolk).

THE principle of the reversible mirrors to .which yourefer is achieved by depositing a very thin film of

THE P.M. BLUE -PRINT SERVICE

12FT. ALL -WOOD CANOE. New Series. No. I,3s. 6d.5

10 -WATT MOTOR. New Series. No. 2, 3s. 6d.*

COMPRESSED -AIR MODEL AERO ENGINE.New Series. No. 3, 55.*

AIR RESERVOIR FOR COMPRESSED -AIRAERO ENGINE. New Series. No. 3a, Is.

"SPORTS" PEDAL CAR. New Series. No. 4, Ss.*

F. J. CAMM'S FLASH STEAM PLANT. NewSeries. No. 5, Ss.*

SYNCHRONOUS ELECTRIC CLOCK. NewSeries. 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. 11, 3s. 6d.*

PANTOGRAPH. New Series. No. 12, Is. 6d.*COMPRESSED -AIR PAINT SPRAYING

PLANT. New Series. No. 13, 7s. 6d.'MASTER BATTERY CLOCK.*

Blue -prints (2 sheets), 3s. 6d.Art board dial for above clock, Is.OUTBOARD SPEEDBOAT.10s. 6d. per set of three sheets.

LIGHTWEIGHT MODEL MONOPLANE.Full-size blue -print, 3s. 6d.

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

P.M. BATTERY SLAVE CLOCK -2s." PRACTICAL TELEVISION " RECEIVER.

(3 sheets), 10s. 6d.P.M. CABIN HIGHWING MONOPLANE.

Is.*

The above blue -prints are obtainable, post free,from Messrs. George Newnes, Ltd., Tower House,

Southampton Street, Strand, W.C.2.

An * denotes constructional details are available, freewith the blueprints.

metal, silver for example, on a glass surface. - Viewedfrom one side the glass looks opaque, but you can seethrough it fairly clearly, from the opposite side. Theexplanation is tied up with the optical properties of verythin films, which are so thin as to be transparent, eventhough they may be of metal.

We are not sure that such glass is made commerciallyin Britain, but you might enquire of an optical firm likePullin Optical Co., Ltd., Phoenix Works, Great WestRoad, Brentford, Middlesex.

Cleaning Tobacco PipesT FIND difficulty in cleaning my smoking pipes

by the common method of the pull -throughpipe cleaner. Some of the tar, gum, etc., is re-moved but the job is never thorough and the pipeclean and fresh.

Could you suggest a harmless liquid for gettingrid of all the nicotine, etc. ?

It did occur to me that steam, forced throughunder light pressure, might be satisfactory, butthis is inconvenient and difficult to do.-S.Kremer(Manchester 20).THE main deposits in a smoking pipe are carbon,

resinous products and tobacco juice bonded withtobacco " tar," all of which tend to char with time.

To clean, first of all remove as much deposit as possiblewith a pipe cleaner and scrape out the bowl. Thenplug the mouthpiece temporarily, and fill the pipe withalcohol or methylated spirits. Leave it to stand for aday or two, then rinse out with alcohol, and allow to drythoroughly.

If you are a connoissuer of tobacco this treatmentmay leave your pipe with not quite the flavour you wouldlike, in which event you could swill it through with some-thing like brandy and let it soak. Rum is also a pleasantflavouring. Keep the alcohol away from the outside,for it will dull any high polish on the wood.

Fitting a Direct ViewfinderT HAVE an old folding camera which has the

number indicating hole on the i6 exposureside, but is a 21 x 31 size camera. In order to usewithout cutting case I have masked off for 16exposures.

The viewfinders were never very effective and,now size is changed, I wonder if you can give meany simple information as to how to make up asimple wire viewfinder to fit on side of case, i.e. adirect viewfinder. -S. C. B. Mee (S. W.a5).A DIRECT -VISION finder could easily be fitted.

The aperture in the front of this should have itssides in the proportion of 21 to t 5/8th. An actual sizeof t8mm. by t3mm. is suggested. (This being the

of the frame.)If the lens is of 4l in. focal length, the angle subtendedalong the longest side of the negative will be 3o degrees(approx.). 3o mm. should therefore exist between theframe above mentioned and a small rear frame or plate,the latter having a hole 3mm. in diameter, to which theeye is placed.

The two frames (e.g., front one with 13 x i8mm.aperture, and rear one with 3mm. hole) may be hingedfor folding down ; when erected, they should be 3omm.apart, as mentioned.

A check that the view seen through finder is correctmay be made by removing back of camera and sub-stituting ground -glass or thin tissue paper for the film,and fixing the camera so that a distant scene is projectedon the paper (shutter open). In the event of the lensbeing of different focal length from that" you suggest,it will be necessary to increase or reduce the size of thefront aperture in the viewfinder which is being made, orto move the two components of the finder nearer togetheror farther apart, so that the exact angle of view isobtained.

Building a CanoeT AM considering building a canoe by covering a

light wooden framework with a skin oflaminated paper but I have been unable to finddetails of the type of paper used or the glueused for bonding the lamination.

Would a kraft or imitation kraft paper besuitable and could casein or resin glue be used forbonding ?-Robert W. Hersee (Glam.).

WE suggest the use of strong cartridge paper. Foran adhesive either casein or ordinary glue,

treated with potassium bichromate, might be used,in either case there must be no doubt about its water-proof qualities. Whatever glue is used the paperwould obviously have to be put on in small piecessince large sheets could not be made to lie down onsurfaces which are curved in all directions. It wouldbe preferable to make the skin of several thicknessesof thin, closely -woven canvas. By laying this " on thecross," that is to say diagonally as regards warp andweft in relation to the lines of the hull, a whole side,of the canoe, can be covered in one sheet. This canthen be treated with either cellulose dope, varnish or amixture of paint and varnish and a second sheet laidon and similarly doped ; then a third sheet and so onuntil a sufficient thickness of skin is attained. Finally,the last sheet, when thoroughly dry, is rubbed downwith glasspaper and given finishing coats of enamelpaint.

Spontaneous Glass FractureAT the hospital where I am employed, we are

rather mystified by the peculiar shattering of the clear, plain glass plate forming the detach-able top of an instrument trolley, otherwiseconstructed wholly of metal tubing and mountedon rubber-tvred wheels -normally equipped with



a " safety -chain " to drag along the ward flooring(but not actually in place when the breakageoccurred).

The trolley was stationary, unattended andwithout any equipment of any sort on the glassplate, when a slight report was heard and the glassdisintegrated and fell in fragments, apparentlywithout any interference or change in normalatmospheric conditions.-(Miss) Anona N. Middle-ton ( Grays, Essex).'THE spontaneous fracture and complete disinte-

A gration of the glass sheet to which you refer isquite a well-known, although not nowadays a verycommon phenomenon.

We ourselves have experienced similar effects inwar -time in connection with laboratory flasks, beakersand other chemical glassware which, standing undis-turbed on storage shelves were sometimes found in adisintegrated state and, once or twice, actually shatteredthemselves to fragments with a sound like a rifle shotduring the day and for no apparent reason. Yours is aprecisely similar case.

The reason is that when molten glass is allowed tosolidify it tends to set up great strains within itself.The more quickly the solidification of the glass takesplace the more intense the internal strains. Such glass ifstruck with a light hammer or even nicked with apair of pliers will often shatter to pieces. In suchinstances, there is a sort of chain action throughout themass of glass, the release of a local strain, releasingstrains in other areas, and so on, the strain -releaseeffect travelling through the mass of glass with greatrapidity.

In order to stop this sort of thing happening, goodquality glassware is annealed by heating up to a giventemperature in an oven and then by being allowed tocool down gradually. This slow cooling, although itdoes not entirely remove internal strains, very muchlessens them so that there is very little risk of anyspontaneous strain -release with consequent disinte-gration of the glass.

Occasionally, however, it happens that a glass sheetor other article escapes the annealing process or else isnot properly annealed. When this happens, and theunannealed article passes out into use, there is alwaysthe risk of the spontaneous disintegration happening,and in such glasses, no precaution can be taken againstthis event.

This is the sort of thing which has happened in theinstance which you quote. Either in consequence of someslight surface scratch, some small tremor or vibration,or even as a result of the glass's internal molecularactivity, a local strain has managed to release itself. Achain action has been formed, and the entire mass ofglass has released its own inner strains and has disinte-grated itself in consequence.

Plate glass is rolled, and during this process, someconsolidation and strain relief is given to the glasssurface. Notice, therefore, in the instance of yourplate glass that the surface of the glass has not disinte-grated. It has remained more or less as a continuousskin covering a disintegrated interior and tending tohold the latter together. If the glass had been reasonablyfree from internal strains this event would not haveoccurred.

Cycle Fork OffsetT INTEND to design and build my own cycle

frame but find difficulty in calculating theoffset of the forks. I have been told that forany combination of head angle and wheel diameterthere is only one correct offset and this must beworked out by formula. Is this correct and, ifso, what is the formula 2-C. J. H. Marks(Cornwall).THE easiest way to deal with this question is toA draw the centre line of the steering column atthe desired angle to the horizontal and to set thepoint of contact of wheel and ground about an inchbehind the point where the centre line of the columnmeets the ground. At the point of contact erect aperpendicular to the ground with length equal to theradius of the wheel. The upper end of the perpendi-cular is the centre of the wheel, and its distance fromthe centre -line of the steering column is the " offset."

By adopting a dimension greater than tin. thesteering becomes more stable. By adopting a dimensionless than tin. the steering becomes less stable. If thewheel touches the ground at a point ahead of thecentre -line of the steering column the steering isunstable.

It is not true to say that for any particular steeringcolumn angle there is only one offset that is satisfactory.

Gauge " oo " Station RoofIHAVE just completed a terminus station for a

" oo " gauge model railway. The arch roof,built up on trusses at 6in. intervals, is covered withcellastoid, applied in one piece 49in. long by 231 in.

Po --- Cardboard

Wood

Method of joining cellastoid strips.

wide. The cellastoid is glued down all round.We found that as soon as the roof was movedfrom my home where it was built, to the railway in

a friend's cellar, the celinstold went lumpy.Could you tell me if there is any way of treatingcellastoid to prevent this ?-T. Nelson (Southport).YOUR sheet of cellastoid is obviously much too

large. Expansion and contraction alone arebound to be unequal and when the presence of evenslight moisture is added the buckling is aggravated.You would be well advised to cut the sheet up intostrips running crosswise and arched over the stationroof, inserting light wooden girders, bent by steaming,all to exactly the same curve equal to the requiredcamber of the roof and letting each of these support thetwo edges of adjacent cellastoid strips. Then overevery joint pin down a narrow strip of cardboard.As shown in the diagram. The cellastoid will not becemented in any way and, therefore, expansion andcontraction will take place across the roof; the ends ofthe cellastoid being left free to move.

Electric Motor QueriesIHAVE a 13o/ z/so 134 amp, 2,930 r.p.m. capacity

motor. It has six terminals arranged thusA3 ZaAa - As At and Za are coupled together.A4 Zs

I take it that I shall need condensers to operatewith this motor. Can you tell me what type andcapacity these should be and also what the con-nections will be, also the starting current offload. A formula for future reference would bevery useful.-W. F. Williams (Wilsham Bishops).IT would appear that the motor is one of the capacitor -

start -and -run types and we suggest that you usethe following connections :

Zt and At to be linked as at present. At and Azappear to be the ends of one of the main windings andA3 and A4 the ends of the other main winding, whilstZi and Zz are the ends of the auxiliary winding.

For starting connect line terminal Li to At andline terminal L2 to A4. Connect As to A3. ConnectZ2 to the common connection of two condensers Cxand Cs, the other sides of these condensers beingconnected in parallel to line Lz.

For running connect Li to At and L2 to A4 (same as for starting), Connect As to A4 and to one terminalof Cr. Connect the other terminal of Cr to one terminalof Cs and the other terminal of C2 to Zz. Connect Atto A3.

Ron L2

Circuit diagrams for a capacitator motor.

It will be seen that, for starting, the two main wind-ings are connected in series and fed from the supply,the auxiliary winding being fed from the supply throughthe two condensers in parallel. For running the twomain windings are connected in parallel and fed fromthe supply, whilst the auxiliary winding is fed from thesupply through the two condensers in series. The typeHLAT starter, as supplied by Brook Motors, Ltd., ofEmpress Works, Huddersfield, would, no doubt, besuitable for this motor. The condensers should be con-tinuously rated and could have a capacity of about .40mFd. each. The starting current may be about 25amps. Alternatively, if the motor starts on light loadyou could start up with the two main windings in

series, or possibly in parallel,and the starting winding fedthrough a condenser ofabout 8o mFd. capacity. Themotor may be reversed byreversing the connections toZi and Zs.Cleaning RadiatorTubes : Watch Clean-ing Fluid : MercuryGilding

\ MY house is fitted with a " Neo " No. 2 fireplacekI) for heating water and radiators and I find

great difficulty in cleaning the tubes of coal tar

deposit. Could you give me a formula for asolution to use ?

(a) Could you give a formula for a watch -cleaning fluid that is non -rusting ?

(3) Please give me the formula and method ofapplication for mercury gilding on metal suchas brass, clock cases, etc.-P. Ryan (Northants).

\ A MODERATELY strong solution of caustic soda1) (I in 6) would clean your radiator tubes, but

there would be a danger in using this solution inthat it is a caustic one and is liable to set up corrosion.We advise you to effect the necessary cleaning as muchas possible by scraping and other manual methods.When once the tubes are reasonably clean, you canprevent the further deposition of scale by dissolvingin the water a small quantity of sodium metaphosphate.A slowly soluble form of this chemical can be obtainedunder the name of " Micromet " from Messrs. Albrightand Wilson, Ltd., 49, Park Lane, London, W.', whichfirm, we think, will send you full particulars concerningthis material and its domestic use. The " Micromet "will, of course, not prevent the deposition of tar, whichapparently comes from the fuel which you burn. Thetar deposit can best be removed by dissolving out withbenzole.

(2) The following is a good formula for making thewatch -cleaning fluid in which you are interested :-

Solution i.-Boil 'oz. of oleic add in r quart ofwater.

Solution 2.-Add 6oz. of ammonia to t quart ofwater, then add zoz. of acetone.

Bring this liquid to the boil for a moment and thenadd it slowly to the hot Solution a. Stir the mixedsolution until it is homogeneous.

A still simpler solution for watch cleaning can bemade by dissolving § lb. of ammonium carbonate and

lb. of soft soap in is gallon of water.Both these solutions have good cleaning properties,

but they do not prevent rusting of steel. Hence, theparts so cleaned should be immersed in methylatedspirit or iso-propyl alcohol in order to remove thesurplus water.

(3) Mercury gilding, or " fire gilding," as it is called,is an extremely expensive process, and for your Workit might be more economically preferable to employsome form of electro-gilding, particulars of whichyou will find in any textbook on electro-plating.

Mercury gilding utilises an amalgam of gold andmercury of somewhat indefinite composition. Thisamalgam can be made by dissolving gold filings orpowder in hot mercury. It is essential to use " fine "or pure gold for this purpose, and not the ordinarycarat gold. Fine gold, in powder form, can be obtainedfrom Messrs. Johnson, Matthey and Co., HattonGarden, London, E.C., price about Li per gram.

The article to be fire gilded is degreased andscrupulously cleaned. It is then brushed over witha solution of mercuric nitrate (strength immaterial).This will deposit a very thin film of mercury on thesurface of the brass or copper. A fine wire brush isthen rubbed over the mercury -gold amalgam (whichshould be in pasty, semi -solid form). The wire brushis then rubbed over the article to be gilded. An evenlayer of amalgam is thus applied to it. To increasethe thickness of the gold deposit this operation maybe repeated a number of times, but finally the articlemust be heated in a charcoal fire in order to expel themercury. This " firing " is a dangerous operation,for the mercury vapour which is expelled from thearticle is easily inhaled and is very poisonous. Afterthe mercury film has been driven off by the heat theapplied gold appears as a pale yellow deposit which isrendered more uniform by scratch -brushing. Thecolour of the gold film can be deepened considerablyby passing the work through a paste made of alum,common salt and saltpetre. After this, the work isheated until the residue of the salt mixture on itssurface just fuses. The work is then immersed inhot water, which dissolves out the fused salt mixture.It is then rinsed. Such an operation can be repeatedseveral times, and each time the colour of the golddeposit will be enhanced.

In experienced hands fire gilding gives extremelygood results, but there are very few people able toperform such operations.

Telescope QueriesPLEASE inform me what magnification is

necessary to view the moon and planets(rings round Saturn, etc.). I understand that themagnification is found by dividing the focallength of the object glass by that of the eyepiece;,is this correct ? Where can I obtain the necessarylenses, ex -Government if possible ?-R. G. Clarke(Suffolk).A GOOD magnification for viewing the objectsA named is X40.Such magnification can be obtained with a Sin.

dia. object glass focus 4oin., and an eyepiecehaving an equivalent focus of sin., or a 21 in. O.G. of3oin. focus and eyepiece of lin.

Yes, the power is O.G.; therefore on a 4oin. O.G.

a 4in. f. eyepiece would yield a magnification of So.Try Messrs. Broadhurst Clarkson and Co., Farringdon

Road, London, E.C.s, for the lenses.

PRACTICAL MECHANICSHANDBOOKBy F. J. Camm.

I2/6d. or by post 13/..


NO MORE KEY WORRIESIF YOU USE

the LASSMAN COMBO -LOCK,10,000 KEYLESS

DIFFERS PADLOCK

516EACH

I)x21for yourTOOL -CABINET, LOCKER, CUP-BOARD or ANYTHING ELSE YOU

LIKE.SOLID DIE-CAST with BRASS ROL-LERS and CASE-HARDENED

SHACKLE.Obtainable at your local stores, ironmongers

hardware or cycle dealers.Manufactured byLASSMAN & CO. LTD.

LONDON, W.9CHEMISTRY APPARATUS

Send 21d. stamp forCOMPLETE PRICE LIST

BECK

Booklets :Experi-

ments" 10d.' Formulas "

Home

Oh' mistry "

2/3l'o,r

(Scientific Dept. A)60 HIGH STREET,

Stoke Newington, London, N.16

EITHER IT ISot irisit?

JUBILEE has been our regirtered trade namefor 30 years, and may not be used to

describe any other Op.

THE FINEST CLIP fit.** woadL. ROBINSON & CO., (GILLINGHAM) LTD.,

London Chambers GILLINGHAM KENT PHONE 528211.3263/ R1

WESLEY AIR PISTOLSMarvellouslyaccurate fortarget prac-

tice.No licence required topurchase for use on

enclosed premises.Write for Catalog= of AIRPISTOLS, Alit RIFLES and

Accessories.WEBLEY & SCOTT LTD.,

106, Weaman Street. Birmingham, Eng.

WI ND CHARGINGHeight ensures success and reducesbattery capacity. Lattice tube pylonmasts, easily climbed, erected andextended. Lighter type for aerials.Also Lucas " Freelite " Sets, new,used and spares.

S.A.E TUBECRAFTLong Itchington, Nr. Rugby.

RATCHET & REVOLUTIONCOUNTERS

Ask forLeaflet No. 181 I

Speed up to6,000 r.p.m.

B.& F. CARTER& Co., Ltd., Bolton 5

Members of B.E.S.T.E.C. Orpantsattan.

..16111311

A REALLY SMALL RADIO RECEIVERThis radio receiver Is PRICEonly half the size ofa matchbox but givesloud clear reception

of the B.B.C. Home,Light, and Third Pro-grammes on themedium waveband,about 180-550 metres.

No catswhiskers, POST FREEcrystals, valves, orbatteries are required, and the setworks off a short indoor aerial in manydistricts.

Instructions are included for makinga small, simple, and cheap loading coilfor tuning the Light Programme on1,501 metres.

This oiler applies only to G t. Britain,Irish Republic and Northern Ireland.

SWIFT RADIO (P),137. Cotham Brow, Bristol. 8.

ORDERS BY POSY ONLY.

r_

IMMEDIATE DELIVERYELECTRIC

WELDERand Complete Kit '41,:s\

For Welding, Soldering,Brazing, effecting all metalrepairs in the home and onthe ear or eyrie. Instant heat..6,0000 F. Works from 6 v. or 12v.ear battery or transformer fromA.C. mains. Complete kit of Weld-ing Toole, 9 ft. cable, clip, carbons. -eleareung fluid, fluxes. filler rods, sea -dies, instructions, hints. Thouainds ofthese amazingly low -priced -but re-markab'y effeetive-Electric Welders are Indaily use in Farm Workshops, Garages. etc.throughout Britain and Overseas. c.2/6Welds all metals. Up to one -eighth 'as,gauge. C.O.D. IF REQUIRED Post Free.HARRIS ENGINEERING CO. (Dept. P.M.)

269 Kingslanl Road, Leaden, E.2.

MASTER THE PIANOEASILY, QUICKLY, ENJOYABLY

To learn to play really well is easywith proper teaching I I CAN

TEACH YOU by poet to playbeautifully. Ordinary metricalnotation, no freakish methods.My pupils' roll grows daily, I state

it in every advertisement. It is your as -entrance of success. My class is seldomless than 2,000 pupils. I have taught over86,500 and I CAN TEACH YOU (in 12lemons) even if you do not know a note.FREE BOOK and advice. Say Mod.

Beginner. (Block letters please).MR. H. BECKER

(Dept. 158).The Hall.

Centurion Rd,.Brighton, Sussex

TAPE RECORDERScomplete and in KITS, also AMPLI-FIERS, Recording Tape, Etc. Prices.complete, from I37.10.0. Kits from

432.5.0.Write for Lis:.

RADIO EQUIPMENT COMPANY(Dept. P.M.), Castor Road, Brixham,

Devon.

SAWBENCH ESComplete range for bench or floormounting for 410. to 30in. saws from59/9ki. complete. Spindles, Bearings,Pulleys, Belts. Motors, CompleteAssemblies for 4in. to 301n. saws from24/2d. Combination machines forsawing, grinding and drilling from42ffid.

Send 9d. for Catalogue Handbook.Beverley Products, Ranskill, Notts.

200 SHAVES -2d.Amazing Cyclop' ATOMIC'Blade Keener keeps razorblades equal to new orbetter. 2 0 0 superb shavesfrom only ONE 2d. blade.From Damages, Barkers of

Kensington, or Direct. Post dn.

/6Send s.a.e. (lid.) for leaflet--KORVING LTD., (PMS)54, Frederick St.. London, W.C.1.

When replying to advertisers'announcements please mention

" Practical Mechanics "

Price9 Si. On.

C:17. rstr

MachineVice EA.

The Adept ' BenchHand Shaper

Length of stroke omm 31 ins.

No. 211. II Shaper, Olinstroke

rut iii a*:PRECISION

CASH OR TERMS

DREADNOUGHT

4:"Heavy DutyS.S.S.C.Lathe

BUILT FORPRODUCTION.Dept. P.M.,

Portass,Butterinere

Road,Sheffield, 8.Tel. 51353.

£144CAN YOU BEAT IT ! Guaran-teed A.C. 2.20/240 v. BatteryChargers. " ASCOT " COM-BINED 6 v. and 22 v. D.C.sizes Tin. x 31in. x 64in. x 24A, withchangeover switch £3.3.o, withAmpmeter i4.o.o P. Pd. Wecan also supply Complete Kitsfor making these at £2.5.o andE3.0.o P. Pd.A.C. MODEL RAILWAYS KIT39/6.S.A.E. for list, including Trans-formerg, Technical Books.LAWRENCE FRANKEL

MAIL ORDER,134, Cranley Gardens, London,N.10 TUDor 1404

BARGALN LINESCOLLAR() 3 -Speed Autochangers. play10 101n. or 12in. records at 331 or 78 r.p.m..also Tin. at 45 r.p.m. Our price 212-8-2.Single -speed ditto £9-17-4. P.U. Headsfrom 39/5.DECCA 3 -Speed Gram. Units, completewith Pick-up and Autostop. Price 28-9-0.PORTABLE RECORD PLAYERCABINETS in brown rexine. 39/8. PORT-ABLE MICROGRAM CABINETS, takegram unit, amplifier and BIM. speaker.price 62/6. " SYMPHONY " AMPLIFIERfor A.C. mains, amazing realism, separateBass, Treble and Middle controls, scratch -cut, negative feedback. 5 -watt model10 Ens.: 10 -watt model, 15 gets. BASSREFLEX CABINET KITS, 30in. high, com-plete to last screw, 85/- to 10716. Send lid.for full catalogue.NORTHERN RADIO SERVICES, 18.Kings College Road, Swiss Cottage,London, N.W.3. PRImrose 8314.

IMPETUS Precision PLANERSCircular safety type cutter -head Highquality tempered steel knives. Tablesmounted on machined inclined ways.Ground, table -surfaces. Fencesadjustable to 45 deg. £9.10.0in. MODEL,Motorised. 9113.10.0. 8 in. MODEL928.10.0. Motorised 944.0.0. Send forCatalogues of other Impetus' Products.JOHN P. 51. S. STEEL, Dept. 80.

RINGLET, YORKS.F'hJne ELNGLEY 3551 (4 lines)

ADANA PRINTING MACHINESPrint in the odd hours with anAdana -still the most absorbing

01 crafts. No. 1 ILSMachine t 2447-6

No. 2 ILS MachineE10 - 15 - 0. Willquickly pay tor its

illustraelf.Sendfolder to Dept. P.M.60.

ADANA (Printing Machines) Ltd., Twicken-ham, or call 8, Grays Inn Rd., London, W.C.1

BATTERY CHARGERS2-6-12 volts one amp.

Brand new In steel case with Ammeterfor 200-250 volt A.C. mains.

only 59/6(delivery 2/6) guaranteed.

THAMES VALLEY PRODUCTS (P)"Orart," Eleanor Rd., Chalfont St. Peter, Backs,

10 English Lever Watch Movements MomGold and Silver Cases, accept 30/- the 10Ten Geneva Movements, 201- the 10. TenSwiss Jewelled Lever Movements, 30'- the

10. Very useful to Watchmakers.Merkel's Jewellers. Grey Street

Newea st le -on -Tyne. Postage.The SUPER

' ADEPT ' LATHELila. centres, bin.between

centres.

Frier 65 162. 02- A Good Rangeriles £18 Th. 6d. ro.teyr,. aud packmg 1/6 di K.J. l'heAsk

of Aceesaoeieeyou, dealer. Adept " r it.d.F. 4.3aw tort. is available.Hoyssfoye.,01 by pendent Chuck. Reversible Jaws. 38/I6

F. W. POILTASS. MACHINE. TOOLS. I.TH.ADEPT WORKS. 55. MEADOW STREET. SHEFFIELD. 3.

You Can Become aHANDICRAFTSINSTRUCTOREXPERIENCE NOT ESSENTIAL

Men who enjoy making things inwood or metal can turn their hobbyinto a permanent and interestingCareer ! Short hours, long holidays,and security in a job you wouldreally enjoy, can be yours if youbecome a Handicrafts Instructor.Let us send you details of the easiestand quickest way to get the necessaryqualification.

We definitely Guarantee" NO PASS -NO FEE"If you would like to know about

our unique method of preparing youfor one of these appointments, writetoday, and we will send you aninformative 144 -page Handbook -FREE and without obligation. Markyour letter " Handicrafts Instructor."

British Institute of Engineering Technology591, Shakespeare House, DET

17/19, Stratford P1., London, W.1 N1

TELEPHONE SETS, comprising 2G.P.O. hand -phones, 2 bells, 2 pushesand 80ft. twin wire. Price 65/- postfree. Makes an excellent inter -office,works or domestic installation. Reallyprofessional instruments. Brand new,not rubbish. Single Instruments, 184.BATTERY CHARGERS for A.C.mains. For charging 2 -volt accumu-lators at 1 amp, Parts with diagram,Pale Complete, 264, Postage 1/-.FOR TRICKLE CHARGING CARCELLS, parts with diagram. Outputlj amps. for 6v. or 12v. cells. Price 42/6Post 1/-. 3 amp. output, 50/-.POWERFUL HAND ENGRAVERfor all Metals, Plastics, etc. Operatesfrom 6 v. battery or through trans-former from A.C. mains. Engraver,226. Transformer, 15/-. Post 1/-.Instrument Wires. Ebonite, Metals.Workshop Materials. Illustrated List 2d.

ECONOMIC ELECTRIC Co.64 London Rd., Twickenham

DRAUGHTSMAN'S SETMagnificent set of precision 026/.Drawing Inetrumente - Self fie.

centering compass with ink and 0 N L Ydivider attachments and tele- r,

oatscopic extension arm - Rulingpen -Ink and pencil spring- PRE'bows - Spare leads - Instrument screw-driver. All in handsome velvet lined case.ALSO i Imp. Battened Drawing Beard,T Square, Protractor, Set 32/6

SPECIAL OFFER - A L LITEMS AS ABOVE ...

Cash wills order - Moseybock if nol

WRITE NOW ! F.G.L. Supplies,71 Colney Hatch Lane, London, N.10

STAINLESS STEELCYLINDERS

Working pressure 400P.s.i. Tapped both

24' s 12" ends. t gas. Suitablefor Compressor Tanks, Pneumatic Units,Gases, Hydraulics and Liquids.

W. T. HUMPHRIES,Poughill, Bude, Cornwall Carr. 5/-

35/ -

PLASTICSsold ; Perspex sheets and offcutsin stock, large quantity of clearand all colours, 1/ i thickat cheap price ; Cellulose Acetatefilm, Moulding Powder, etc.Please send your enquiries to :

MULTITEX LIMITED10-11, Archer Street, London, W.1

Tel. : G ER rard 9520 and 5728

Amateur Radio EnthusiastsTHE INCOMPARABLE

GLOBE -KINGSINGLE VALVE S.W. RECEIVER WORLD-WIDE RANGE 11-100 METRES CRYSTAL-CLEAR NOISE -FREE RECEP-TION ELECTRICAL BAND -SPREADTUNING 0 EXTREMELY LOW RUNNINGCOSTS

Catalogue Free. Stamp ror postage.JOHNSONS-(RADIO) -

46, FRIAR STREET. WORCESTER


176

SPARKS'DATA SHEETSare the Safest, Simplest and FinestConstructional Sheets of Guaranteed

and Tested Radio Designs.

THE " MIDDY "The Finest little 2-Valver ever offered to theConstructor. It covers Ship -to -ShoreTransmissions and Medium- and Long -WaveBroadcasting. All -dry battery operation.Fine Speaker results. Most widely Praisedby the many hundreds who have made it inall parts of the Country.Full-size Data Sheet. 3121 Post Free.

THE " BOSUN " 3Last month I asked you to meet the

Bosun." and I still say that if you wantsomething more Powerful than the' Middy,' then the "Bosun "Is IT. It is a' Straight' 3-Valver. All -dry batteries.Ship -to -Shore plus Medium and Longwaves. Well and Truly Tested in Dorset.Economical and Reliable. Full-size DataSheet. 3/21 Post Free.

NOW MEETTHE " SKIPPER "

Here is yet another New Design. .The" Skipper is a T.R.F. 4 -Val ver. All -drybattery operation specially designed forthose who want Range and Power. SingleKnob Tuning. Ship -to -Shore transmissionsplus Medium and Long waves. The idealSet for Reliable Trouble -Free Listening.Full-size Data Sheet. 3/21 Post Free.

IMPORTANT. if you own the " Middy "you can use ALL the parts and Valves inthe " Bosun." If you make the " Bosun."you can. au a later date. use all the parts andValves for the " Skipper."Progressive Construction Without Waste.

SPARKS LEADS AS ALWAYS.SPARKS' DATA SHEETS COVER DE-SIGNS FROM A CRYSTAL SET TO A9 -VALVE RADIOGRAM.

Send Stamp for List.Components Supplied.

0-0 L. ORMOND SPARKS (M)48A, HIGH ST., SWANAGE, DORSET

LANGUAGE PROBLEMSOLVED

By the Pelman MethodTHE problem of learning a Foreign

Language in half the usualtime has been solved. The Pelmanmethod enables you to learn French,German, Italian and Spanish withouttranslation.

By the Pelman method you learnFrench in French, German in German,Spanish in Spanish, and Italian inItalian. English is not used at all.Yet the method is so simple that evena child can follow it.

Specially reduced fees for serving andex -Service members of H.M. Forces.

Grammatical complexities are elim-inated. You pick up the grammaralmost unconsciously as you goalong. There are no classes to attend.The whole of the instruction is giventhrough the post.

The Pelman method of learning lan-guages, which has now been used for over25 years with such success, is explained infour little books, one for each language :

FRENCH, SPANISH,GERMAN, ITALIAN

(Also Courses in Afrikaans and Urdu)You can have a copy of any one of these

books, together with a specimen lesson,gratis and post free, by writing for itto -day.

POST THU FREE COUPON TO -DAY

To the Pelman Languages Institute,130, Norfolk Mansions, Wigmore St.,

London, W.I.Please send details of Pelman methodof learning :

French, German, Spanish, Italian(Cross out three of these)

Name

Address


VIEWMASTER TELEVISION for the Coronation ; the Viewmaster envelopecontains seven full-size working plans for easy screw -together television. Guidebook gives complete price and shopping lists for the various stages, absolutelyPoint-to-point wiring details, and trouble spotting guide. All parts always in stocksent C.O.D or cash with order. State your transmitter area when ordering. TheVIEWMASTER envelope 7s. 8d; NO RADIO KNOWLEDGE NECESSARY.

MODEL BOATS, CARS and AEROPLANES. Send 5s. for full working plansof transmitters and receivers for controlling your models at a distance ; no radioknowledge necessary. Range, 1 -mile for boats and cars, over 1 mile for aeroplanes.All parts in stock for immediate delivery. Send 21d. for list.

MAKE YOUR OWN RECORDS on plastic tape, using your gramophone for drive :records will play back thousands of times without loss of quality, or they can beerased and the tape used over and over again : tape will last for years. All parts instock for immediate delivery, list 21d., data ls.ELECTRIC BLANKETS for the winter months can be made in two hours, usingour warming units, price 35s. 21d. stamp will bring you the details.DECCA GRAMOPHONE MOTORS with turntable, but less pick-up. 78 and 231r.p.m. 230 v. A.C.. 23/1711, plus 2s. postage and packing. Suitable pick-ups from35s. lOd. Many other gram. units in stock, including autoclaangers, send 21d. forlist. Regret no H.P.

AQUARIUM AERATORS, quietest on the market, 230 v. AC., 29s. 8d. ; thermo-stats, 10s. 6d., 13s. 6d. and 18s. fkl. according to size of tank heaters 10s. 641.All 230 V. A.C./D.C., all plus ls. postage and packing.

IVALEK CRYSTAL SETS, de -luxe type in white bakelite case, 21s, : need head-phones at Ss. 9d. and good aerial and earth, 5s. Postage on set is.ELECTRIC MOTORS WITH GEARBOX attached, can be driven off 230 v.A.C./D.C. or 24 v. D.C., or if driven by power (wind or water) will generate abovevoltages. Motor can be adapted for many uses. Price with comprehensiveinstruction sheet, 24s. Sheet separately, 21d.MINIATURE HEADPHONES, super lightweight ; complete with length of flexto plug into radio's extension speaker sockets, good for grandma to listen in. Quitesafe, no risk. 17s. 84. per pair.VIBRATORY POWER PACKS, 6 v. D.C. input, 230 v. output. Tbese'power packswill work a midget radio set provided it has .15 amp. filament valves and enablesdomestic radio to serve as a car radio. Price 57s. 6d., plus 2s. 6d. postage.PHOTO ELECTRONIC FLASH GUN : all parts supplied to enable you to buildyour own at greatly reduced price. Data and price list, 9d.VALVES AND COMPONENTS of all types in stock and quoted for by return.Please let us have all details as shown on the old part. No lists, as stock is too vastto catalogue, but all modern valves and components and many obsolete ones in stock,including parts for television. Send 21d. stamp for reply.ROTARY TRANSFORMERS for working model trains from D.C. mains. Output12 v. at 2 amps. with 5 v. for track lights or signals, 230 v. D.C., 37s. ea., 230 v. A.C..47s. 64. Postage and packing 2s. 6d. extra.

PARK RADIO OF MANOR PARK676/8 Romford Road, Manor Park, E.I2

'Phone ILF 2066.

Car style lightia, for Cycles-

" KING "MINOR

ACA

Modelled on famous Lucas CarLighting equipment, Silverplated brass reflectors. Intensebeam with ample local light.Twin wiring eliminates earth-ing troubles. Detachable cableconnectors. Powerful 6 v.

3.3 w. generator with com-bined universal bracket

and rear light. Ask yourlocal cycle dealer toshow them to you.

Prices: 34/6 to 47/6Minor illus : 34/6

----1,101,11111111010

"ifal *foe/airier

CYCLE DYNAMO SETSJOSEPH LUCAS (CYCLE ACCESSORIES) LTD., CHESTER STREET, BIRMINGHAM, 6

January, 1953

UNUSED EX-W.D. BARGAINS

FRACTIONAL H.P. EX-R.A.F.H.P. BRAND

NEW ELECTRICMOTOR

Made by Hoovers(147-f-46

80.V 37/6Carr. 2/6

Not CO be confused with smaller, cheapertypes. Size Ilin. x 5110. a 51in., weight18 lbs., volts 200-250. State A.G. or D.C.2,000 r.p.m. Ideal for Polishing, Grinders,Washing Machines, etc. Existing spindletin. diam., din. long. All-purpose extn.spindles to screw on, 7/6 pair extra.BATTERIES, unused, vehicle type. Size10in. x Tin- x 81n. depth. 6 volt 90 amp..75/ -plus 5/- carr. ; 6 volt 100 amp.. 90/- incl.:6 volt 77 amp. storage type, 90/- incl.WATERPROOF LEGGINGS, green.quality oilskin, snip, 5/- pair incl.DINGHY MASTS taper telescopic) 151n. to8ft. 6in.. 816 incl. ; ditto with additional40in. taper extension to suit, 10/: -LAMPS, brass ships hanging lamps. 61-Incl.: Bulbs to suit. 1/- extra. (State 6 v..12 v. or 24 volt.)

HEADPHONES, Boxed.Ideal Crystal or Valve Sets.Hospitals, etc.. 7/8 pair incl.TRANSFORMERS,Input 230volts ; output 6.75-0-6.75volts, 19 amps., 40/- incl.SCREWDRIVERS, 91n. Three for 5/8 inclMETERS. Six asstd. Meters and Instill.ments, 2d1-- per parcel incl.BARGAIN PARCELS, " Lucky Dip,".12/8, 17 8, Mt-. Guaranteed value.}CLOW LAMPS, new, 2pt, 'size. PetrolBurning with Pressure Pump, 30/- incl.LISTSHundreds of Other bargains available,send large S.A.E. for full four Lists.

AUTO COLLECTIONS LTD.15, LAWRENCE STREET,

NORTHAMPTON.

ALPHA OFFERSCOLLAR() A.C.37.-Motor variable speed.0-100 r.p.m., 100125 v. 900/250 V.. 3216 each.Post 1/6.METAL. RECTIFIERS. -12 v. 1 amp..1/6 each. 12 v. 1 amp., 416 each. ? to 6.v.1 amp., 3/- each. 250 v. 45 en/a. 619 each.250 v. 75 m/a, 7/6 each. 12 v. 3 amp., 18/6 each.LOUD SPEAKERS. -All 2-3 ,12. Plessey,Goodman, Waterhouse, Lelectrona. 5in.units. Less transformer, 11/6 each. ElseTruvox, 61in. units, 13/8 each. Truvox,61 in. unit with transformer. 17/6 each.Rola 10in.. 25'6. Plessey 10in., 2V-. TruvoxBX11, 12in.. 57/6 each.COLVERN WIRE WOUND VOL. CON-TROIS.-200 ,Q, 500 D. 1,000 12, 2,000 0,5,000 D. 10,000 .Q. 15,000 17, 20,000 Cl, 25,000 17,50.000 D, all 2/9 each.TR uVoX HEAVY DUTY 121n.SPEAKER15 f2 Speech Coil, 26.10.0 each. Carriage 3/-.MOULDED MICA CONDENSERS. -.01,.001, .002. .003, .005. .0001, .0002, .0000, .0005,.00027. etc., all by well known makers,4/6 doz.MAINS TRANSFORMERS. -3 -way mount-ing standard 2001250 mains. MT4. 350-0-850. 80 m/A. 6.3 v. 4 amps, 5v. 2 amps., 16/ -each. Auto transformer. 100/100 volts to200/250 v.. 17/6 each. MT3. Primary 200/220/240. secondary 30 v. 2 amps. with taps at2v.,4v..5v.,6v..8v..9v..10v.,12v.,15v.,18 v., 20 v., 24 v., 17/6 each.EXTENSION SPEAKERS WITHVOLUME CONTROLS.-R.M. 63in. unitin Brown Bakelite cabinet, 39/6 each.Raymond his, unit in two tone cabinetBlack and Green, 42!8 each.VALVES. --Guaranteed new and boxed,majority in makers cartons. 1R5. 1S5,1T4, 184. 8/6 each. Set of 4 inc. post, 33/,SP61, SP41, VU120A, RKR72, EB34, CHP72,PEN23)A, 8D2, 9D2, all 3/6 each.3S4 ... 10/8 6F6 ... 9/- 6V6G Br,51140 9/- 6J5 ... 5/6 6V6GT 9/,5Y3GT 9/6 6K7 ... 8/6 80 9/85Z4M ... 9/8 6106 ... 4/6 VU39 9166C6 7/6 6K8 ... 12/8 VU111 4/66D6 6L6 ... 10/6 35L6GT 9/6We have hundreds of valves BVA and ex -Government at Special Prices. Write forQuotation.TERMS. -Cash with order or C.O.D. MallOrder Only.Full list available send 3d. in stamen.Postage 6d. to 10/-, 1/- to 20/-, 1/6 to 0,-.Minimum C.O.D. Fee and Postage 2/3.

ALPHA RADIO SUPPLY CO.,5/6 Vinces Chambers, Victoria

Square, Leeds, 1


· 2019-10-23 · Africa, biltong, which is the meat of the antelope cut very thin rather like a...

Documents

Transcript of · 2019-10-23 · Africa, biltong, which is the meat of the antelope cut very thin rather like a...