ELECTROPLATING AT HOME

www.americanradiohistory.com May, 1953 NEWNES PRACTICAL MECHANICS 317

M AY, 1953 PRACTICAL EDITOR VOL. XX F. J. CAMM No. 233 MECHANICS Owing to the paper shortage "The Cyclist," "Practical Motorist," and "Home Movies " are temporarily incorporated. By The Editor Fair Comment 3-D DEVELOPMENTS filmsand wouldrequireonlymildpurpose. Cameras have gradually STEREOSCOPIC films have beenalteration to existing apparatus. acquired more lenses and up to six are much discussed in recent weeks Great strides are being made almostnow accommodated on the lens turret, innewspapersasthoughtheyevery month in the science of television,providing a wide and flexible range of were a modern invention.The fact isone of the latest being automatic pictureviewing angles.Dangerous research can that from the earliest days of the cinema-control, whichwasrecentlydemon-be made more safe by the use of suitably tograph there have been literally dozensstrated in London. sited cameras.Electrically, experiments ofinventionsforthree-dimensional In many TV areas to -day a certainconnected with circuit breakers operating films.In almost every case the vieweramount of signal fading occurs.Someat high voltages are too dangerous for is expected to wear special glasses, andplaces are far worse than others, but inanyone to approach nearer than 2ooft., the three-dimensional films being shownmany districts, at some time during anwhereas a camera can be placed into to -day, with two exceptions, still makeevening's entertainment, controlshaveposition only 3ft. from the main rotor use of that system, which has manyto be reset due to a change in signalof a 40o kV generator, providing the defects, not the least of which is that ifstrength. It is claimed that automaticengineerswithaclose-upof what one's eyes are not perfectly matched, orpicturecontrol TV willprovideahappens whenageneratorisshort if there is myopia or astigmatism in onesteady picture of constant contrast andcircuited through tests. of them, the picture is not seen in threebrilliance even though signal strength Remote control of a large crane by dimensions but becomes blurred. varies by as much as z0 to i. radio and TV permits the crane to handle Althoughcolourfilmshave made dangerousproductssuchasatomic This was proved convincingly at thematerial in bulk, and the operator can marked progress in the last twenty yearsdemonstration, and although the picture see what the craneisdoing without they are still far from perfect.No oneblacked out completely on an ordinary has produced a film in natural colours ;TV receiver due to signal fading, theexposing himself to danger. theyalllook lurid and unreal.Theautomatic picture controlset was not same applies to colour photography. noticeably affected. DEVELOPMENTS IN SAFETY AT SEA Withtelevisiontheprojectionof A further advantage with this new set pictures in colour has made some pro- device for saving lives at sea isthe " interference damper," a deviceANEW gress-no more than that.Such de-which makes for a considerable reduc- was recently demonstrated in Lon- monstrations asI have witnessed, in-tion of " snowstorm " interference.Indon.It consists of a transmitter fitted cludinga demonstration by thelatethe bright areas of the picture streaks ofinto a small box no larger than 12in. x Bairdandanother by a well-knowninterferencestaywhite,butindark7in. x Sin. deep, bolted to the underside television manufacturer, merely indicateareas where they have shown up whiteof the thwarts or seats of a lifeboat. that colour television is possible at somebefore on the screen they now become The only action that the unfortunates distant date. in the boat have to take is to mount the grey and are practically invisible. rod typeaerial by a simple plug-in PROJECTION TV TV AS AN AID TO INDUSTRYaction and then turn the handle of the UNTIL someone candiscover a meansA RECENT application of TV is astransmitter until a small neon light comes of amplifying light as we can now an aid to industry and science inon and continue turning the handle until amplifysound,thedevelopmentof the signal is seen to be going out.This observation techniques, and the threeis shown by means of another neon in- projection TV will be hampered, becausecompanies manufacturing TV cameras dicator which blinks accordingtothe as the picture is " blown up " the lightareallproducing apparatusforthis diminishes and the picture takes on a morse signal being radiated. woolly aspect.This is not particularly Part of the signal is a continuous tone noticeablewithpictures upto,say, SUBSCRIPTION RATES and rescuing ships can use it for direction loin. square, but forbig screen tele- including postage for one year findingandnavigating ontothose vision the problem becomes more diffi- Inland - -- - 14s. per annum. adrift. cult of solution.It is my view, however, Abroad---- 14s. per annum. It is true that, by regulation, wireless that eventuallyall TV receiverswill Canada- - 13s. per annum. transmitters have to be fitted in a pro- Editorial and Advertisement Office :" Practical make useof atinytube whichis Mechanics," George Newnes, Ltd., portionof theship'slifeboats, and cheaply replaced, in conjunction with Tower House, Southampton Street, Strand, W.C.2 although it may be possible in a large 'Phone : Temple Bar 4363 anopticalsystemincorporatingthe Telegrrns :Newnes, Rand, London. number of cases to find the lifeboat with Bresnel lens. Registered at the G.P.O. for transmission by the transmitter, it is virtually impossible, 3-D television is already on the way Canadian Magazine Post. in anything like a heavy sea, for a flock Copyrightinalldrawings,photographs and and is being considered by the BBC. articles published in "Practical Mechanics " is of lifeboats not so equipped to keep Viewers will not need special glasses, speciallyreserved throughout the countries within hail of the transmitting boat. asimpleattachmenttothe signatorytotheBerne Convention and the Itis merely U.S.A. Reproductions or imitations of any of with the object of equipping viewing screen.This system can easily these are therefore expressly forbidden. these other boats that this transmitter be adapted for the cinema showing of has been developed.-F. J. C.

www.americanradiohistory.com 318 NEWNES PRACTICAL MECHANICS May, 1953

. . LITCY OTLEFE gATEE The Theory of Electroplating and its Practica Application in the Home Workshop ELECTROPLATING is the process of By E. HARRIS MORGAN, B.Sc. proton and one electron. This is the atom depositing on a base metal a thin, of hydrogen. In Fig.tthere are shown uniform, adherent, non -porous coating the atoms which result by taking first one, of some other metal, from a solution of aelectronisanextremelyminuteparticle then two, then three protons, and soon.It suitable salt of this metal, by the use of an(about t/t800th of the mass of a proton)will be noticed that in the nucleus of all the electric current. possessing unit negative electric charge. atoms, except that of hydrogen, there appear a Now the atom iselectrically neutral andnumber of neutrons. It so happens, that in Reasons for Electroplating therefore must contain an equal number ofthe atoms illustrated in Fig. t, the number of There are many reasons why such a coat-unit positive and unit negative charges, or,neutrons is the same as the number of protons ing may be advantageous. For reasons ofto put it another way, an equal number ofbut this is not necessarily always the case.In mechanical strength and ease of working, theprotons and electrons. The positive charges,the case of the element lithium, it will be seen two metals most commonly used in engineer- that the extra electron takes up a new path, ing are iron (including steel) and brass. Both Orbit and that we now have two orbits. Each iron and brass are subject to attack by gases Nucleus additional electron enters the second orbit of the atmosphere. In the case of iron, rust- 0- ELECTRON until there are eight electrons in this orbit, ing with consequent loss of strength occurs, and then a third orbit is started.Itis an O while in the case of brass, tarnishing spoils 0 PROTON (P) interesting fact that the elements with eight the appearance of the article.Electroplating electrons (or an octet) in their outermost orbit both iron and brass with a coating of some are all chemically inert ;that is to say, they () NEUTRON (N) Helium suitable metal, such as nickel or chromium, Hydrogen do not join with other elements to form com- prevents the process of tarnishing and at the pounds. same time provides a surface of permanent and attractive lustre. In the case of car lamp reflectors, the coating serves another Electrolytes purpose.The reflector is easily spun from There are two main classes of compounds, brass, but brass tarnishes rapidly and would electrolytes and non -electrolytes.Itis the require constant polishing, and, added to this, electrolytes with which we are concerned in brass has a yellow colour.Coloured objects Lithium Beryllium Boron electroplating, and the theory which follows possess their colour by virtue of the fact that is confined to this class of compound. they absorb and abstract certain wavelengthsFig.1.-Diagrams illustratingthestructure The atoms of active elements, in combining from white light ;thus coloured objects do of the atoms of a few of the elements. to form compounds, either give or receive not reflect all the light which falls upon them. electrons so that the outermost orbit possesses By coating brass with a " white " metal, a a complete octet.In Fig. 2a the atoms of higher proportion of the light is reflected andorprotons,are clusteredtogetherinthepotassium and chlorine are shown diagram- the reflector is thus made more efficient.Thecentre of the atom together with a certain matically. Itwillbenoticedthatthe metals commonly used for plating reflectorsnumber of neutrons,and this cluster is knownpotassium atom has one electron in its outer- are chromium and silver.Whether electro-as the nucleus. Around the nucleus revolvemost orbit, and the atom of chlorine has seven plating beautifies an object is a controversiala number of electrons equal to the numberelectronsinitsoutermostorbit. When subject with which I am not going to dealof protons in the nucleus. These electronspotassium andchlorine combinetoform here ; some readers may hold one opinion andrevolve in well defined paths, or orbits, about potassiumchloride,eachpotassium atom others another.There is one charge, how-which more will be said later. gives one electron to each atom of chlorine, ever, that cannot be laid against electroplating, The simplest atom is one which has oneas shown in Fig. 2b.Each potassium atom and that is that it covers slip -shod work.If anything, the very reverse istrue, for the effect of plating a roughly finished article is to bring out allits deficiencies.More will be said about this later when the practical aspect of the subject is dealt with.Beside the advantages mentioned above, there are other specialised uses for electroplating which need not concern us here. Theory of Electroplating Inordertounderstandthetheoryof electroplating, it is necessary to know a little about the atomic structure of the elements. The full theory of this structure is, of course, a complicated affair, and so, in the following paragraphs, I have attempted to develop a simplifiedversionwhichcoversjustthe ground that we require. Atomic Structure Every material thing in this world, indeed in the whole universe, is built up of an enormous number of minute particles which we call atoms. The atoms themselves are built up of three types of extremely small particles. These particles are known as protons, neu- trons and electrons. The proton is a rela- tively large particle which possesses a unit positiveelectric charge. (The significant word here, is " relatively," since the actual mass of a proton is approximately o.00000000000000000000000t7 grams. There are about 28 grams in one ounce.) The neutron isaparticlewhichisof approximately the same mass as a proton but Young soldiers receiving instruction in electroplating at the Army Technical School, Arbarfie d, whiet possesses no electrical charge. The Berks.

www.americanradiohistory.com May, 1953 NEWNES PRACTICAL MECHANICS 319 is now left with a complete octet and eachis called the cathode, and that connected toFactors Governing the Nature of the chlorine atom also possesses a complete octet.the positive pole is called the anode. Deposit There isa very important outcome to this Ihave shown that thesolution ofan To be effective the deposit of the metal change however.If the charges at the centreelectrolytecontains chargedparticles,theusedforplatingmustpossesscertair (the protons), and the charges in the orbitsions. The effectofpassinganelectricproperties.It must first be uniform.This (the electrons), are balanced, it is found thatcurrent through an electrolyteistocausecondition is obtained by placing the article the potassium atom now has an extra unitthe electro-positive ions or anions to move tobeplatedasacathode between twc positive charge, and the chlorine atom antowards the cathode where they receive ananodes,or,incertaincases,by making extra unit negative charge. Thus, potassiumelectron, so converting the ion back into aarrangements for the rotation of the article in potassium chloride is not in the form offree atom.The cations, on the other hand,during the plating operation.Secondly, the a potassium atom but in the form of a posi-move towards the anode where they are dis-deposit must have good adhesion with the tively charged atom, and the chlorine in thecharged and converted into atoms, their sparearticle being plated.In order to obtain this form of a negatively charged atom. Theseelectrons being absorbed into the circuit. condition all surfaces to be plated must be charged atoms are known as ions, and have scrupulouslyclean andfreefromgrease. verydifferentpropertiesfrom uncharged Details of the process involved in cleaning atoms. A positively charged atom is known and preparing for plating will be given later. as an anion, and a negatively charged atom The third desirable propertyisadeposit is known as a cation.Since the ions of which is already in a highly polished condi- potassium and chlorine are present in equal tion, or one which can be worked up to a quantitiesin potassium chloride, these high polish.This last property is one which charges cancel each other, and the net result is most difficult to obtain, as the nature of is that potassium chloride has no charge. Electron flow the deposit depends on a number of factors. The above theory can be applied to any The solutions used are not merely solutions electrolyte, and it therefore follows that any Resistance of simple salts, but are solutions to which electrolyte can be divided into two sets of O other chemicals, which play an important particles, anions carrying apositive charge part in the process, have been added.The and cations carrying a negative charge. temperature of the plating solution isalso of importance, different types of deposit being Electrolytes in Solution produced by solutions at different tempera- When an electrolyte is dissolved in water 1 tures. Another importantfactoristhe it breaks up (or ionises) into its constituent NC- Arc current density.This is the current flowing ions (to a greater or lesser degree).Since Electron flow persquareinch of surfaceareaofthe these ionscarryelectriccharges they are cathode.Beside these factors, others, such capableofcarryinganelectriccurrent. as the ratio of anode area to cathode area Thus, solutions of electrolytes are conductors and the strength of the solution, play their of electricity. Anode Cathode parts.A good deal of research has been It is now necessary to consider the nature made on these factors enumerated above, and of an electric current.An electric current the result has been a series of formula and may be regardedasaflowofelectrons technicaldetails- whichmakessuccessful throughawireorotherconductor. AFig. 3.-(a) Electron flow in a simple circuit.electroplating a practical possibility. battery or generator can be considered to be (b) Electron flow through an electrolyte. a pump which promotes thisflow. The Apparatus Required direction of the flowis from the negative The apparatusrequiredtoelectroplate pole of the battery, through the circuit and It is thus possible to deposit the electro-successfully in the home workshop depends then back to the positive pole. positive or metallic part of the compound (This is inonthecathode,theelectro-negativeparton the size of the article to be plated.In the opposite direction from the conventionalbeing deposited on the anode. general, the larger the article, the more com- direction of flow of an electric current,i.e., By a suitableplicated and expensive becomes the apparatus from positive to negative.This -is becausechoice of electrolyte, and by using the sameneeded. metal- forthe anode asispresent inthe For small articles, such as the model the convention was decided upon before thecompound, itis possible to ensure that theengineer might require toelectroplate,the true nature ofelectricity had been estab- apparatuscanbereasonablyinexpensive lished.)Fig. 3a is a diagram showing theelement or group set free at the anode attacksand uncomplicated. flow of electrons through a circuit.If wethe anode and dissolves it in the form of ions. replace the resistance of Fig. 3a by a vesselThus the strength of the solution is main-Plating Vat tained and metaliseffectivelytransferred containing an electrolyte, leading the currentfrom the anode to the cathode.This is the A glassbeaker,suchasisusedina into and out of the electrolyte by means ofprincipleofelectroplating,althoughforchemistrylaboratory, makes amost con- metal plates, we get the arrangement shownpractical reasons certain departures are madevenient plating vat for small articles.These in Fig.3b.The metal plates whicharefrom the simple theory outlined above. beakers can be obtained in a variety of sizes used to introduce the current into the electro- from any laboratory suppliers or chemists lyte are known as electrodes.The electrode Copper wires and are not expensive.Since the plating connected to the negative pole of the battery solutions are used hot, a beaker made of heat- resisting glass should be chosen. Thermometer Athermometerwhichhas thescale engraved on the stem is necessary.There Moveable are many typestochoose from and one electrode should be selected which can be read easily. Copper) Two temperature scales are in current use, Electrode the centigrade and the Fahrenheit, and for detail this reason temperatures willbe given on Potassium atom Chlorine atom both scales.The thermometers should read from o deg. C. -s so deg. C. in the case of the centigradescale,andfromodeg.F.- 250 deg. F. in the case of the Fahrenheit scale.

Coppersulphate Electrical Instruments solution Suitableinstrumentscan bepurchased (4oz/prnt) Fixed electrode from advertisers in this journal. Two instru- ©Potassiumion Chlorine ion (Copper) ments are normally used,a voltmeter and Stone jar an ammeter.Of these the ammeter is the Fig.2.-(a) Diagrammatic representation of most important, and, indeed, for simple work atoms of potassium and chlorine.(b) Ions ofFig. 4.-Circuit resistance.Variation of thethe voltmeter is not essential.The amateur potassium and chlorine formed by the transferresistance is obtained by altering the position isadvised todispense with the voltmeter. of an electron from the potassium atom to theof the movable electrode. Some simple arrange-The ammeter range depends on the type of chlorine atom.(Note that the ions have eightment formaintainingtheelectrodeatthe plating and the surface area to be plated. electrons in their outermost orbits.) required height should be adopted. For most small work an ammeter reading

www.americanradiohistory.com 320 NEWNES PRACTICAL MECHANICS May, 1953 up to 5 or to amps is suitable, but if largethin, has very little effect on the appearancebeforethedegreasing operation), andthe areas are to be plated, instruments readingof the finished article, but when we come tocurrent to be used is calculated by making up to3o amps may be necessary.Itis plate the article, the grease, being a non-use of the figure given for current density. possible to purchase an instrument which canconductor, will prevent the flow of electricityThus, if the article hasasurface area of be converted to the required scale by addingat various points and thus prevent the forma-20 sq.in., and the current densityisci.t simple resistances as shunts. tion of an even coating of the plating metal.amp/sq. in., then the required current will Moreover, when plating does occur, there willbe 20 x o.t = 2 amps.The article is sus- Circuit. Resistance be poor adhesion with subsequent peelingpended in the vat with the current switched The circuit resistance is capable of varia-of the plating. An oxide layer will produceoff and the resistance settoits maximum tion,sothatthecurrent flowinginthethe same effects,anditisimportantto value. The current is now switched on and circuit can becontrolled. The resistanceensure that once the article has been pre-the resistance gradually decreased until the should bevariable between about o andpared itis plated without delay. ammeter indicates the appropriate value.If 15 ohms, and should be capable of carrying itisdesiredtoinspect thearticle during the maximum current to be used.Ready-Degreasing plating,the current must be switched off made sliding resistancesareavailable, but In order to degrease the article, it shouldbefore thearticleiswithdrawn from the they are expensive, and the reader is advisedbe immersed ina hot solution of causticsolution. If this precaution is not taken, a to construct one as shown in Fig. 4. soda for about five minutes. The causticvery high current density will be produced soda solution can be prepared by dissolvingat the edges of the article and the plating Power Supplies two ounces of caustic soda in one pint ofwill be marred at these points. When the For small work, an ordinary six -volt drywater.A glassvessel should be usedas plating is completed, the articleis removed battery gives quite satisfactory results, but it acontainerforthesolution.The articlefrom the bath and given a thorough rinse. is preferable to use a bank of three accumu-is then rinsed in clean water and immersedThe plating can now be brought to a high lators, which have the advantages of beingin a dilute acid.Sulphuric acid is used forpolish by the use of a buffing wheel, or,if able to deliver a much greater current and ofthe treatment of iron and steel articles, andthisis not obtainable, by the use of metal beingrecharged.A six-or 2 -voltcarnitric acid for articles of copper and brass.polish on a soft cloth. battery, if available, is admirably suited forThe dilute sulphuric acidismade up by the operation. diluting one ounce of concentrated sulphuricFormulae :-Copper Copper israrely used as a final plating, butisgenerally usedasan intermediate plating.Since,however, the process and formula are quite simple and the chemicals k6Volt- battery are comparativelyinexpensive, I have Circuit included details of the process here so that Voltmeter resistance (may be omitted) it can be used as an initial exercise in elec- troplating. Copper sulphate 4 oz. Sulphuric acid (conc.) r oz. Distilled water 2 pints. """---- Switch Article being Anode plated The copper sulphateisdissolved in the water and the sulphuric acid added cautiously Plating while stirring the solution. Anode vatNote : The plating solution Plating iscarried out at room tempera- Fig. 5.-Diagram of the is brought to the requiredture and the current density employed should circuittobesetup for temperature before switch-be o.x amp/sq. in.The plating tame should plating. ing on the current. be 20-25 minutes. Two anodes of copper sheet are used. This solution can be used repeatedly since Switch acid with three pints of water, and the nitricthe copper deposited on the cathode isre- Some simple switching arrangement, capa-acidbydilutingfourouncesofcon-placed by copper dissolved from the anodes. ble of making and breaking the circuit at thecentrated nitric acid with three pints of water. particular current value used,isnecessary.(WARNING.It is important to note thatNickel When the current is below 5 amps, a knifethe acid must be added to the water, and Although nickel plating requires a fairly switch of simple design is satisfactory, butnot the water to the acid.Stir well whenhigh current density,itisa process which for higher current values a switch designedcarrying out theaddition.) The time ofcan be carried out quite easily and effec- to make and break at that value should beimmersion should be between one and twotively by the amateur when small articles are used.(Of course, there is no objection tominutes. A further rinse inclean waterplated. The metal is softer than chromium usingaswitch designed for 3o amps tofollows, and the article is then given a finaland the plating has a warmer colour.Nickel break a circuit carrying 2 amps.)A low -polishwitha dampclothchargedwithis often used as an intermediate plating on voltage switch of the required type- can bepumice powder.After these operations theiron and steel in the operation of chromium obtained from a dealer in car accessories. article is given a thorough wash in runningplating. water and transferredimmediatelyto the Chemicals plating bath.It should not be dried between Nickel sulphate 4Z. The various chemicals used in the pro-degreasing and plating. Ammonium chloride oz. cesses will be detailed under the appropriate Duringthedegreasingoperation,the Boracic acid oz. article should not be touched by the fingers. Distilled water 2 pints. headings. Itis an easy matter to bend up a simple pair of tongs from wire or strip, and these The plating bath should be usedata Other Apparatus should be used to handle it. temperature of about 90 deg. F. (32 deg. C.), A quantity of connecting wire (copper 16 and a current density of 1.5 amps/sq. in. The gauge) and a few crocodile clips are neces-Setting Up the Apparatus plating timeisfour to five minutes.The sary for setting up thecircuits. A pint The apparatusissetupasshownin anodes should be pieces of nickel sheet, one measure will also be required for making upFig. 5 (the voltmeter being omittedif notbeing placed on either side of the cathode. the solutions. available).The vatisfilled with the plat-As with copper, the plating solution can be ing solution at a temperature a few degreesused repeatedly. Preparing the Article for Plating above that given (in order to allow for cool- The golden rule of electroplating is thating during the operation). The solution canChromium the quality of the plating can never be betterbe heated by placing the vat in a saucepan Chromium isone ofthe most popular than the surface finish of the article beingof water over afire. A more convenientmetals for plating and thereisno reason plated.Every care should be taken, there-arrangement is to heat the vat directly, bywhy successful results should not be obtained fore, to obtain as fine a finish as possible.standingit on a wire gauze placed ona bytheamateuriftheinstructionsare All tool marks must be removed by thetripod, and heating with a bunsen burner.followed. In the case of steel and iron, judicious use of emery paper or a buffingInthisway,agreatercontrol overthean intermediate coating of nickelwillbe wheel. temperature of the solution is obtainable. found to be advantageous. During itsmanufacture, thearticlewillMethod of Operation Chromic acid 5 oz. inevitably have picked up an uneven layer of The surface area of the article is obtained Sulphuric acid (conc.) 20 drops. grease. This layer, being normally quiteb7 direct measurement (this should be done Distilled water x pint.

www.americanradiohistory.com May, 1953 NEWNES PRACTICAL MECHANICS 321 The operating temperature of the platingabrasions .on the hands. At this juncture68 deg. F. (20 deg.C.), and the current bath should be about 104 deg.F. (4o deg.C.),it might be well to say that many of thedensity 0.2 amps/sq. in.The anodes should and the current density 0.5 amps/sq. in. Thechemicals used in plating are of a corrosivebe of silver, and the bath will last indefinitely. plating timeisto -i5minutes. Inthisnature and should be kept out of contact Copper and brass can be plated directly, case anodes of lead are used, and after awith the hands, clothes, and so on. Abut iron and steel should receive an inter- certain amount of usage the bath will becomebottle of household ammonia should be keptmediate coating of copper before being silver exhausted. The quantities given above shouldat hand, and if any of the plating solutionplated. be sufficient for plating about i,000 sq. ins.,is accidently spilled, mopping up should be after which the bath should be discarded. preceded byaliberalapplication oftheConclusion ammonia. If a large quantity of plating The processes given above are not the Silver solutionisspilled,it can be satisfactorilyonly ones which can be used.Other metals The amateurisadvised toavoidsilverneutralised by adding washing soda.(Vine-beside copper, nickel, chromium and silver plating for two reasons.First,itisan gar is a good antidote for caustic soda.) can be deposited electrolytically.Itisalso expensive process, and, secondly, the chemi- possible to deposit alloys, and, by suitable cals used in compounding the bath are of Silver nitrate t oz. choice of solutions, various grades of brass an exceedingly poisonous nature. Ifan Potassium cyanide toz. can be formed.In general, however, the attempt at silver plating is made, great care Distilled water II pints. applications of deposits of metals other than should be taken that the plating bath does those outlined above, are outside the scope not come intocontact with any cuts or The working temperature of the bath isof the requirements of the amateur.

to the bottom by means of winches.This operation was carried out without incident Submarine Oil Drilling and, soon after the jacket had been lowered into position, four corner bearing piles were driven home by a steam hammer in order A Scheme for Drilling for Oil in the Sea Bed, Employingan to anchor itsecurely.This was necessary as the main piling operation was a long job Aerial Ropeway for Carrying Men and Materials occupying several weeks and was frequently interrupted by unsuitable weather conditions. BY the end of this year the first majoriron. The jacket rests on the sea bed in about submarine oil -drilling operation in theSoft. of water, and befofe the drilling plat-The Aerial Ropeway British Commonwealth from a plat-form was erectedsteel bearing piles were form fixed on the sea bed will be underinserted into the guide piles and driven deep The long span of the aerial ropeway con- ' way in the South China Sea, about a mileinto the sea bed until the required bearingnecting thedrilling platform to the shore off the coast of British Borneo. made it necessary to place intermediate struc- capacity had been obtained. Four rakingtures on the sea bed at 840 ft.intervals, Initiated by Shell, the plari is to drill wellspiles have also been incorporatedinthethese structures being supported on smaller into the sea bed in an endeavour to find anstructure in order to give greater stabilityjackets of a similar type to those employed under -seaextensionoftheSeriaoilfield, and strength. largest single oilfield in the British Common- for the main drilling platform, each being A special technique had to be employedsecurely anchored by fourbearingpiles. wealth and now producing 5,000,000 tonsfor assembling and placing the jacket.ItLifts of up to five tons for materials and ofcrudeoilannually. The under -waterwas decided, therefore, to fabricate the jacketequipment can be handled over the ropeway extensionofthefieldhassofarbeenalongside the .shore in the sheltered river atand a transporter car for personnel has also explored only by deviated wells drilled fromKuala Belait and support it on two bargesbeen provided. theland and from platformserectedin clear of the water, each barge being equipped Royal. Dutch/Shell engineers were respon- shallow waters near the shore. with special framework Made up from Baileysible for formulating the whole project and bridging. The whole assembly was thendesigning the steel structures and the drilling Four Wells from One Platform towed out to sea and the jacket lowered onplatform. For this project, four separate submarine oil wells can be drilled from a single fixed platform.The foundation for the platform is a tubular steel jacket, which, prefabricated in harbour, is carried out to a selected loca- tion and securely fixed in position on the sea bed.It is capable of supporting a weight of up to zoo tons. The technique of drilling four wells from the same platform is designed to obviate the expense of building a platform at each separ- ate location.One well can be vertical, and the other three can be deviated, thus enabling a large area of the underlying formations to be tested. Two Problems The setting -up of a platform sufficiently rigid to permit drilling to proceed posed one problem.A second and, in this instance, even more formidable problem was to provide access to the platform itself during the long spells of stormy weather encountered in the South China Sea.Since vessels cannot be brought alongside on account of the heavy swell experienced in this region for most of the year, a solution was found in the con- struction of an aerial ropeway linking the drilling platform with the shore.By means of this facility, constant communication can be maintained with the platform, which has been specially contructed to accommodate all the equipment required for drilling. Technical Description The drilling platform covers an area of a 'oft. x 45ft., and is built on to a jacket composedoftwenty-eight24in.diameter verticalsteelguidepilestiedtogether by Underwater drilling project in the South China Sea, off Seria, British Borneo. Four separate horizontal and diagonal bracings of angle submarine oil wells can be" drilled from a fixed platform.

www.americanradiohistory.com 322 NEWNES PRACTICAL MECHANICS May, 1953 PLASTER CASTING

Making the Master Forming the Mould : Casting Painting and Finishing

ByE. S. WEERA The Mould the model is flat and firm against the bottom Aspreviouslymentioned,therearea of the box, take a round stick or rod and number ofbrandsofflexiblemouldinghold against the lip or side of the saucepan. materials on the market.Prices range from The liquid should then be poured down six shillings up to18 shillings per pound.the rod quickly (see Fig.3), and into one Two pounds of low -melting -point mouldingcorner of the box ;not directly on to the material were needed to make each of themaster. At first there may be slight bubbling, illustrated models. These are roughly 6in. xbut this should soon stop, and the liquid 4in. x tin. begin to set.Tiny air bubbles will probably Instructions as to melting temperature andform round the sides of the box. These can sett'ng time are sent with orders ;but thebe ignored, but should they form over the procedure is much the same for most kindsmodel itself, they can be burst by jabbing of th's product. quickly with a needle.If there are too many Before melting down, the moulding com-to burst,itisasure sign that the liquid pound looksandfeelslike medium hardhas not been cooled down enough. With rubber blocks or slabs.It is necessary to cutmoderate bubbling it is still possible to get a good mould but thetopsurfacewillbe pocketed with holes and tiny bumps. Fig. r.-A wall plaque in plaster. Three to four hours should elapse before attempting to take the master model from MAKING plaster models is an easy and the mould.Thisisdone by running a fascinating hobby.There is a ready sharp knife round thebox,pressing the market for good quality work and mould with the fingers away from the walls th's should well repay the initial cost. of the container, and then by turning over The following method of making plaster same and gently knocking the bottom. The wall plagues, statues, ornaments, etc., is well mould, complete with model, should then within the scope and pocket of everyone.In slide out. the past the greatest difficulty in this kind of By flexing the mould the model can be work has been in making a suitable mould ; withdrawn.Ifthisisplasticine,itmay but now there are a number of rubber or leave traces inside the mould which must be synthetic resin products on the market which removed with a soft cloth. A clay or putty solve this problem forall. These mould- model will pull out cleanly and will be in ing materials are melted and, when set, form the same condition as when made. a rubber -like, flexible mould which will wear It may be necessary to split the mould. A long enough for several hundred models to be statue or similar ornament will need this cast. The material can be melted down and treatment, butit does not require halving. used again and again. One side of the mould can be cut with a sharp knife and the mould flexed to allow Making the Master the model to be eased out.(See Fig. 4.) While it is desirable to make models from A split mould willstill hold the liquid your own ideas and work, it- is not essen: plasterifitisheldtogetherby rubber tial. A mould can be made for any small, bands, making sure that the joint matches up cleanly. non -porous object ;there seems little point, Fig. 2.-Another plaster wall plaque. however, in merely copying something that has already been made by someone else. these up into smaller pieces and drop themCasting Clay, china -clay, plasticine or even puttyinto a saucepan. Having made the mould the next stage is can be used to make the original model.Of It is very important not to melt quickly ;casting a plaster replica of the original model. these, plasticineisthe best to use for thea very low gas or electric stove will do theFine white plaster isused, costing a few novicemodeller. Ifthisisuseditis jobadmirably.The product willgive offcoppers per pound; one pound will make necessary to coat the finished job with threeastrongrubber -likesmellbut,generallyseveral models. or morecoats of cellulose varnish.Thisspeaking, itwill only give off fumes when The plasteris mixed in a suitable basin holds the shape of the model long enough forover -heated. and added to the water ; do not add water the hot, molten mould to take its form. A low gas will satisfactorily carry out the The wallplaquemodelsillustratedinmelting in 20 or 3o m:nutcs, but the time Figs.t and 2 were made in this way.Tryvaries acording to the type of material used. to model something from life, a good draw-By using a full gasit can be melted in a ing, or photograph ;it is not nearly so hardfew minutes but will then be burnt and too as it seems, and after practice you will soonhot to pour.If you do not have a thermo- Fig. 3.-Using a rod be able to fashion a good likeness to the sub-meter the best and safest policy is to take for pouring the ject.Use areputable brand of plasticine.plenty of time over melting. moulding compound. By warming, flattening out and rolling,it The liquid should be sfrred gently with soon becomes easy to work with and thea clean stick or rod.While the melting is only tool required is a small, pointed stick,going onthe master model can be made with which to put in tiny lines, marks, etc.ready. If clay is used it needs slightly more skill The clay, putty or plasticine model will to produce a good model. The clay must behave been dried or cellulosed and the next kept moist while modelling and be driedstepisto placeitin a box, which can be off before making the mould ;it need not,wood, tin or even strong cardboard. An however, be baked to hardness. ordinary cooking dish or bowl can also be Putty is perhaps the most difficult to useused for this. Makc sure that there are but quite good results can be obtained. Hereno holesin whatever isused to hold the again itis necessary to dry off the finishedmould.Any holes which do exist can be model.Putty and clay can be used againplugged with putty or plasticine. after making the mould ;plasticine, on the After completely melting the compound, other hand, is usually melted and mixed uptake it off the gas and allow it to cool down with the cellulose skin.If a large model isfora few minutes ;thiswill prevent the made itispossible to recover some of thehot liquid from bubbling when itis poured plasticine by scraping off the cellulose. on to the master.After making certain that

www.americanradiohistory.com May, 1953 NEWNES PRACTICAL MECHANICS 323

In ten minutes the plaster should havepaints will take on plaster.Of these, water hardened and is now readyto be takencolours combined with poster paint give the from the mould.Due to it still being wet,best results and also the widest range. the model will break rather easily, and a Should the model be of an animal or little care is needed here. something from life, a common-sense study With the finger tips gently flex the mouldof the real thing will make it easy to decide away from the plaster, gradually working itwhich colours to use. off the model.In the case of flat objects, Plenty of water is needed with poster and such as wall plaques, calendars, or similarwater colour paints.The plaster will absorb things,allthat is required is to place onethe water and, after painting, it should be dried for about twenty minutes. A coat of clear cellulose varnish brushed on the dried 4.-Splittingthe model will preserve the colours and finish flexible mould. the model off.The models illustrated were painted in this way. Cellulosepaint can be brushed straight on to the model, and no other treatment to plaster or great difficulty will be experi- is required.This is the best paint to use enced in mixing properly. when the effect needed is that of one or two For a model of the sizeillustrated, one colours only. tea cup of water is sufficient.To this was Ordinary paints will give good results but added seven tablespoonfuls of plaster, one have the snag of taking a long time to dry. spoonful at a time.Each helping of plaster Here again, a coat of clear varnish can be added to the water should be quickly andFig. 5.-Method of fixin; a hook for supportingapplied to the finished job. thoroughly mixed, in before adding any more. a plaque. There is no limit to the things that can Itis advisable to mix' the plaster quicklyhand under themould and carefully bend because it reaches the . stage when itwillone end away from the model.(See Fig. 6.) rapidly begin to set and harden.It should The plaster model is dried in a low gas still be liquid when poured into the mould.or electric oven.It can also be satisfactorily If it has begun to set,- it will not flow intodried by placing before -an open fireplace or every corner of the mould, 'anda modeleven in the strong sunlight, The one thing withholesorparts -missedoffwillbeto remember isthat if the drying is done obtained. too quickly, the model is liable to distort and The mould must be laid on a flat surfacemost certainly- to crack.Having gotthis before itis filled with plaster.After pour-far,itis wiser to take' three or four hours ing in the plaster quickly a brief shake ofin slowly drying the model. the mould will get rid of any air bubbles. A wall plaque may have been made, inPainting and Finishing which case a hook will be required in the No matter how well cast a plaster model finished job.A good method is to bend amight be, it can be completely, and horribly paper clip and simply drop it into the liquidspoilt by haphazard, careless painting. A Fig. 6.-Bending the mould away from the cast. plaster.The plaster will set hard and the badly -cast model, however, is vastly clip be cast in, the bend in it preventing itimproved,thefaultshidden,bycarefulbe made from plaster or to the effects that from pulling out when the plaque is hungpainting. careful painting can give.Aim at life -like- on a wall.(See Fig. 5.) Ordinary, water colour, poster or celluloseness, 'unusual design and original ideas.

sliding doors per compartment. The opening B.R. New Hopper Wagon mechanism for each door is a rack and pinion operated from eitherside of wagon by a To meet the requirements of bulk convey-by screwed eyebolts.A roof vent is usedremovable handle. The doors can be sealrd ance of chemicals suzh as soda ash,with or without valve, according to traffic, andby wire seals. sodium tripolyphosphates or catalysts, this acat walk isa'so provided to give ready In the case of soda ash or sodium tripoly- wagon has been designed at Derby, and toaccess to the filling doors. The interior itphosphate a coupling of a quick detachable obtain the maximum Capacity within a totalcompletely flush and thehoppers can bevibrator is welded to the sides of the hoppers gross load of 35 tons, the body takes fullcompletely discharged by gravity through two to assist unloading. advantage of the loading gauge. The length of the vehicle over buffers is 24ft. 6in. and the wheelbase is soft. 6in. The underframeisof special designto accommodate the hoppers through which the load is ejected between the frames.It is of all -welded construction and is 2Ift. 6in. long with standard buffing and drawgear with three linkcouplings. The wheeldiameteris 3ft.'lin. with loin. by 5in, journals and fabricated steel axleboxes.Standard lamin- ated springs 3ft.6in. long are fitted with standard spring shoes. The most recent design of. brake used can be applied from either side of the van and operates one block on each wheel of one axle. The body is of welded construction and is built up of *in. mild steel plates for the roof and sides whilst kin. thick plates are used for the ends and the hoppered portion of the body.Tee sections and gusset plates stiffen the body and are welded to the underframe ; the combined body and underframe giving adequate strength and stiffness. A kin. thick partition divides the body into two compart- ments and two 2 -hinged doors 6ft. t sin, long and 2ft. 5in. wide are -provided in the roof, fitted with rubber weather seals and secured The new hopper wagon for British Railways.

www.americanradiohistory.com 324 NEWNES PRACTICAL MECHANICS May, 1953

THEgrpapiEJOF fftfilteVT° The Reasons for Sweptback Wings and the ProblemsWhich They Introduce.Delta, V and Crescent Wings, and Possible Shapes for Supersonic Speeds

BETWEEN 1939 and 1945 we, in thecal advancement, but inthiscountry the United. Kingdom, were too busy win-biggest strides in the aerodynamic field have ning the war to do as much funda-been taken since the war and were the directFig. 4.-All wing mental research in aerodynamics as, we oughtconsequence of jet propulsion, which made itair liner projected to have done.The Germans, rather curi- in5945 - ously, found time to do much more basic research, and if the war had continued much " The Shape of Wings to Come" was Itisquite possible thatit may be the longer we should have found ourselves in a firstpresentedasapaperby David forerunner of others like it, and it is included difficult position against the rocket propelled, Keith -Lucas, B.A., M.I.Mech.E., here toshow how low -speedaircraftare swept. wing fighters which were just begin- F.R.Ae.S.,ChiefDesigneratShort developing in comparison with high-speed ning tocome fromthe Germanaircraft Brothers, Rochester, in Belfast, Septem- types. industry. ber, 1952. Before the war the difference between a War always provides a stimulus to techni- high-speed and low -speed aircraft was mainly one of degree.They were both flying at subsonic speeds and aerodynamic laws were the same for both.The high-speed aircraft therefore had more power and less drag, but was not necessarily very different in outward shape, from one designed for low speed. To -daythepicture isquitedifferent, because by "high speed " we have come to mean that the aircraft flies at supersonic or, at least, very high subsonic speeds, and, by passing through or even approaching the speed of sound, it has entered a new regime of aerodynamics.Itisa natural corollary that -theaerodynamicshapes havetobe different, too, and as aircraft speeds increase we can expect a continuing divergence be- tween the design of " low speed " and " high speed" types. The Purpose of Sweepback The outstandingdevelopmentinhigh- speed aircraft is the swept wing in its differ- ent guises. It is often stated that sweepback enables a wing to " slide " through the air in rather the same way as a bread knife or a scythe isdrawn across what itiscutting.This, of course, is the principle of the guillotine, Fig. I.-Hurel-Dubois HDio with aspect which always had a swept back or " delta " blade. But we are talking ofair, which ratio of 321. behaves differently from bread, grass or the possible to fly at higher speeds and enhancedhuman neck.Indeed, the analogy isdan- the importance of being able to do so. gerous, if not actually misleading, for at low Germany had reacted sooner than we to the challenge of jet propulsion and we owe a lot to the lead given to us by the German research work. Itishealthy,ifalittle frightening, to recall that Lippisch, in Ger- many, was working on a high-speed delta design even before the last war. It is intended to review the reasons which have led to the sweptback, crescent and delta wing forms andtrytoseewherethese developments are leading us. Ishall deal mostly with high-speed air- craft, although recent researches have led to at least one rather intriguing shape for low speeds, namely the Hurel-Dubois light 'plane which is shown in Fig.I.As will be seen, the wing of the Hurel-Dubois has a very large span and small chord.Its aspect ratio, that is, the ratio of the span to the mean chord, is 321 compared with a maximum of about 12 on the wartime bombers and about Fig. 2.-Diagram of a swept wing in a wind Fig. 3.-The Hill Pterodactyl of 1925. four on modern fighters. tunnel.

www.americanradiohistory.com May, 1953 NEWNES PRACTICAL MECHANICS 325 second one is particularly important if theof a design which was projected by Short aircraftisdesigned fora maximum speedBrothers in 1945 as a transatlantic airliner 2 anywhere between,say, 8o percent.and to much the same specification as the Braba- SLOT 15o per cent. of the speed sound, i.e., for azon. With a wing of 22 per cent. thickness : Iy mach number between o.8 and 1.5. chordratio,ithadtobe averylarge aircraft to provide sufficient headroom in the All -wing Aircraft cabin. Now sweepback was first introduced into On paper it showed an advantage in pay- a 02 04 06 oa to aircraft design for quite a different reason.load and speed over a conventional design, CHORDAL POSITION With the development of cantilever mono-but the passengers' view would have been Fig. 5.-Suction wing aerofoil section. planes designers began to think in terms ofpoor and the stability and control problems thicker wings and explored the possibility ofneeded further investigation. speeds the drag of a swept wing is no lessusing aerofoil section of up to 25 per cent. than that of astraight one; the advantagethickness :chord ratio,As the size of theBoundary Layer Suction is only at high speeds. aircraft increased it became tempting to try One of the objections to using the thick Perhapsthebest way toillustratethetosubmergethefuselage byputtingit wingsectionsdemanded bythissortof purpose of sweepback is to take a rather far-athwartships, inthe wing,sosavingthedesign is that the drag of the wing becomes fetched example from a wind tunnel.Let usweight and drag of the fuselage.Italso unduly high.A thick boundary layer of suppose that we have an untapered wingreduced the bending moments at the wingrelatively stagnant air builds up round the which spans the tunnel and,ifyou like, roots,arising from the upward liftforces, wing and is shed as a wake from the trailing sticks out a bit at either side.The tunnelby spreading the load more uniformly acrcssedge.The drag can be very much reduced speed is 400 mph and the pressure distribu- if this boundary layer tion round the wing is, clearly, appropriate issucked away near to its incidence to the airstream and to the thetrailingedgeof speed. the wing anditbe- Now let us suppose that the wing is made come.] possible to use much longer, so that itsticksa long way verythicksections, out from one side of the tunnel, and that we such as that shown in proceed to pushitthrough the tunnel at Fig. 5, without incur- 30o mph atrightanglesto theairflow. ringanypenaltyin Apart from some slight corrections due to drag over normal skin friction, the pressure distribution over thinsections. The the wing is unaltered and is still that appro- engineering difficulties priate to 400 mph.But if we consider any are considerable as one point of the wing it is, by simple vectors, thequantityofair in an air stream of 50o mph to which the which has to be re- wing is swept back at tan - or about moved isvery large, 35 deg.This is shown diagrammatically in butitcan be done, Fig. 2. and it makes the all- The flowroundthe wing istherefore w:ng design both behaving like that round a straight wing at feasible and attractive. 40o mph, whereaS the actual speed is 500 Fig.6 showsan mph. An aircraft with swept wings can Fig. 6.-Australian suction wingglider. experimental glider therefore fly much faster than a correspond-the span.The obvious development of thisdevelopedandflownbytheAustralian ing one with straight wings before meetingidea was to dispense with the tail becauseAeronautical Research Laboratories. thecompressibilitytroubleswhich, ona there was no longer anything to support it. straight wing, occur at and around the speed It has a wing section of 311 per cent. The longitudinalstabilityand controlof thickness :chord ratio with boundary layer of sound.These troubles include increasethe aircraft was then restored by sweeping ofdrag,lossoflift,changesoftrim, suction. In alecturebeforetheThird the wings back and, in effect, carrying theAnglo-AmericanAeronauticalConference, deteriorationinstability and control, andtailplane on the wing tips. also the possibility of unpleasant buffeting. Mr. T. S. Keeble explained that the experi- This explanationreally amounts to no The HillPterodactyl, of1925was a ment was directed towards an all -wing air pioneeringeffortinthisdirection andis liner and that, basing the design on the more than saying that we can resolve theshown in Fig. 3, from which it will be seenresults of the glider tests, he calculated that velocity into two component's, cne at rightthat although thereisstill angles to and the other along the wing, and a fuselageitis such an air liner could carry 4o per cent. that we can then neglect theflow alongonly a small one.Fig. the wing.For some strange reason most4 shows an example people find the wind tunnel analogy easierFig. 7.-(Below) Pro- to visualise. posalforasuction In practice, due to boundary layer and endwing air liner. effects, the advantage that can be realised isFig.8.-(Right)Air- only about half ofthat indicated by thiscraft with delta wing- over -simpletreatment. But,inspiteof Avro 707. that,sweepback has twoveryimportant contributions to offer. In the firstplace,it reducestheadverse effectsofcompressi- bilityandinthis respect a swept wing behaves in much the same way as a much thinner, straight wing. In the secondplace sweepbackpostpones t h e compressibility effects to higher speedsand, ifthe angle of sweep is suffi- more load4oper- cent.tasterthan one cient, can even post- designed on conventionallines, whilestill pone them tospeeds consuming no more fuel for the same range, well above the speed offering a large advantage in operating costs. ofsound, whichis Fig. 7 shows the general arrangement of something which thin- Keeble's air liner.Itis an attractive pro- ness by itselfcannot position and looks like a high-speed aircraft, do. although,infact,itcruisesatunder Bothcontributions 3oo mph. are important, but the Alternativelythe same devices may be

www.americanradiohistory.com 326 NEWNES PRACTICAL MECHANICS May, 1953 used to obtain wings of very high aspectaircraft. In America the controversy betweenAileron Reversal ratio like the Hurel-Dubois, but without thethat type of design and the high aspect ratio An example of the sort of problem that need for the strut and therefore of lowerwing with a long, slender fuselage has beenI have in mind isthe designer's old bug- drag. dubbed the " big wing " against the " bigbear of aileron reversal.Consider, say, the The great problem with such slender wingsstick " and long-range bombers have beenstarboard wing of an aeroplane on which the is to provide sufficient stiffness and strengthdeveloped to both formula.Both types ofaileron is deflected downwards with the in- in the wing structure without making it tooaircraftweredesignedforrelativelylowtention of increasing the lift on that side and heavy, and 'socancelling the aerodynamic speeds.As the speeds of military aircraftmaking the aircraft roll to port. advantage. The thickersectionspossible have increased, the old controversy has died On aperfectly rigid wing the resultant with boundary layer suction make the ideaaway and a new one has come to take itsrolling moment would increase as the square more practical and it becomes very attractiveplace.The new argument is between theof the- speed, but in practice wings cannot for low speed, long-range aircraft, and espe-different rhapcsof swept wings, and thebe perfectly rigid and the behaviour is more cially for those which require -long endurancebig wing and big stick appear now as thecomplicated. The air loads due to the down- as opposed to range, as, for example, Coastaldelta wing and the sweptback or V wing asward aileron .produce a twist in the wing, Command aircraft engaged on anti-submarineused on the Boeing B47 and B52 and on theup at the trailing edge and down atthe patrol. Consolidated B6o jet bombers.These twonose, so that the wing loses incidence and types are shown in Figs. 8 and 9. loses lift and so produces a rolling moment Tailless Aircraft which isin the opposite directionto that We have got so used to the conventionalAero-elastic Effects arrangement of aircraft with a straight wing, We have already seen how sweepback wasdue to the aileron itself. a long, slender fuselage and a tail, that wefirstintroducedasa means of providing The amount of the twist increases with are apt to look on a tailless design as some-longitudinal stability and control on taillessspeed because the air loads become greater thing of an unnatural freak. Butif weaircraft.The odd part of the story is thatin comparison with the elastic restraint of observe nature carefully we notice that sea-nowadays we are concerned with theill-the wing structure.Finally, there comes a gulls and ducks and many other birds are,effects of sweepback on stability, both longi-speed at which the rolling moment due to in effect, tailless, at least in straight flight,tudinal and lateral.It seems asifit hadthe twist equals that due to the aileron and and bats are tailless the ailerons become totally ineffective. at all times, and are At still higher speeds the effect of the twist probablythemost exceedsthat due tothe ailerons and the manoeuvrable ofall aircraft rolls in the opposite direction to that fliers. Gulls use intended by the pilot. theirtailsin The designer has to see that the " aileron manoeuvring but, as reversal speed " falls well outside the opera- far as one can see, ting speed range of the aircraft and to do more asairbreaks this he may have to make the wing much thanas elevators, stiffer in torsion than would otherwise be a n d, incidentally, necessary. they use their feet in Aileron reversalis a problem which was the same way. , well known in the days of straight wings, There is a strong but sweepback has made ita more subtle argument for a tail- enemy. Not only must we now consider less design on struc- the stiffness of the wing in torsion but also we tural grounds.In a must see that the bending deflections do not pull out from a dive cause a loss of aileron power. It is not imme- or a high-speed turn Fig.9.-Aircraft with V wing-Boeing B47. why this should happen. there isalarge up -load on the wing andturned about and was now kicking for the The best way to see it is by deflecting an usually a download on the tail.On a con-other side; but still,if we keep a careful actual model.Fig. ma shows a model of a ventional -tailed aircraft with sweptback wingseye on its behavioUr itis very well worthsweptback wing.The pointeratthetip the moments due to these loads cancel eachitsplaceinthe teamforitshigh-speed shows the incidence of the wing in the line other out only through the long path up the qualities. The instabilityinitscharacterof flight. The two vertical rods show whether fuselage and the wing to the centre section.shows itself in various ways, of which thethe wing is twisted along its span.In Fig. With a tailless design, on the other hand, themost pernicious are aero-elastic effects,tip ioa the wing isundeflected and untwisted. download of the tail occurs at the wing tips,stalling and rolling moment due to sideslip.In Fig. sob a load applied centrally at the and so we not only avoid the need for aIt is the aero-elastic effects, the aerodynamic tip has deflected the wing while leaving it structurallystrongandstifffuselagebuteffects of structural distortion in flight, which untwisted but, as the pointer shows, there reduce the bending moments in the wingsoften have the biggest influence on the choice This also.There is therefore a potential gain inof wing planform. is a severe loss of incidence at the tip. structure weight as well as in drag, which in turn means a loss of lift which opposes must be offset against the fact that the tail- The fact that the sweepback is employed theintendedeffectoftheaileron.This plane, if we may call it that, has a shorterto allow high-speed aircraft to fly atstill characteristic of sweptback wings may, as moment arm and therefore has to be larger.higher speeds is, initself, a fair indicationwe have seen, produce a serious loss of aileron that we are likely to meet severe aero-elasticpower but cannot, by itself, produce aileron Delta or V Wings problems because at high speeds even quitereversalbecausetheeffectdiesaway to Even without bondary layer suction theresmall distortions may give rise to large aero-nothing as the aileron power diminishes. is a good case for the all -wing and taillessdynamic forces. (To be continued.)

Fig.to.-Distortion of a model sweptback wing. a-undeflected. b-untwisted but with loss of incidencec-no loss of incidence at the tip, but the at the tip. wing is twisted.

www.americanradiohistory.com May, 1953 ,NEWNES PRACTICAL MECHANICS 327 A Grease-spotPhotometer Constructional Details of an Inexpensive Instrument; for the Amateur Photographer By W.L. PEACOCK Preparation of the To save space the bulb -holder was dis- Grease Spot mantled,onlythethreadedportion,the The greasespotitselfsolderingtagsandtheinsulatedspacing is made by dropping candlewasher being retained. These parts were then grease on toapieceof fixed to one end with a wood screw, as art paper and scraping off shown. the excessgrease. Itis The other components can now be added, bettertopreparea fewcare being taken to adjust the height of the such spots on one piece offilter so that it is just above the bulb. paperand toretain and The switch,ifused, fixed and variable usethebest specimen,resistance and bulb are now connected in which should be about *in.series, the leads being taken direct to the dia. and symmetrical. voltage control unit or the bell transformer. A celluloid ring and disc Itwillbe notedthatalug has been as shown inFig.raresoldered to the locking nut of the scale to prepared and after paintingensure ease of locking. onesurfaceofthering black the three parts areVoltage Control Unit The completed grease -spot photometer. cemented together, as shown. The photometer as described here origin- THE instrumentdescribed below is similarFilter Mount ally operated from dry batteries, but if an toa commercial grease -spot photo- The filter mount is of card and the sameA.C. mains supply isavailableit may be meter and can be constructed for little sizeasthering usedinthe grease spotconnected to this via a suitable bell trans- outlay by the average home mechanic,as assembly. former. no doubt most of the required components The control unit, Fig. 2, consists of a to will be found in the oddments box. ohm variable resistance, a voltmeter fitted Basically,itconsists of an electric bulb with a plain scale with a mark at about 5 fixed below a grease spot, the brightness of volts, a switch and a 6 volt dry battery. An the bulb being regulated by means of a vari- Ever -ready 6voltbattery, No. 996,will able resistance.If such a system is placed supply current for this instrument for a few beneath another light source the grease spot years before its voltage drops to the mini- will either appear light against a dark back- mum required for its accurate operation. ground or dark against a light background, In practice, the power supply is switched depending upon whethertheupperlight on and adjusted to the mark by means of the source is weaker or stronger than the lower variable resistance when the variable resis- one. By altering the brightness of the lower Fig. 2.-Circuit diagram of control unit. tance in the photometer is fully out of cir- source the grease spot fades into the back- cuit, i.e. the lamp is at its brightest. ground, and at this point the relative inten- As the cord is opaque, and mounted close Itcould equallywell beset withthe to the bulb, it serves to restrict the beam ofresistance fully in the circuit, so long as this sities of the two sources are equal.Hencelight reaching the grease spot. it is possible to measure the intensity of the procedure is always adopted. upper source. Assembly Calibration To obtain as great sensitivity as possible the range of brightness controlled by the The woodenbaseandendsandthe The method of calibrationis to use the variable resistance should be spread over asaluminium top and sides, were given a coatheight of the enlarger head above the easel great an arc as possible. This is arrangedof black cellulose after being drilled to takeand theiristoobtainaseriesoflight by choosing a value for the fixed resistancethe various components. intensities one-half of the previous one.The such that it cuts down the brightness of the Pointer knob lighttoaboutthegreatestthatwillbe f/2 dia. hole Small pointer for Paper speeds Plate soldered to lock required for normal enlarging purposes, and nut to provide easy using a variable resistance of such It value Insidating Aluminium locking of dial Wooden ends washerora...... 4.t.aiop )(ides that it dims the light to almost zero over an a base .1 arc of about 18o deg.This represents an Grease spot assemb/ 2T-41

= = exposure range of about 3o minutes on the 1 ." 4Ellue filter attached ' -=-L- r 1' final scale prepared for the instrument. ., to card ring -._,_ . --7.- 1-* The values of the resistances ;so ohms 4v.3a. bulb ____ k for the fixed and 25 ohms for the variable Toggle one are not claimed to be the most effective, switch but gave in the original instrument a fairly Celluloid disc .743" dia. ' Variable resistance 25.n. longscaleasmentionedintheprevious ContactsLampholder paragraph, when an initial voltage of about 5 volts was used. The blue filter was included to compensate forthegreaterpercentageofredlight emitted by the low voltage bulb compared Leads to with the normal enlarging bulb, and also to Celluloid ring outside voltage enable the balance point to be arrivedat dia. z$" inside dia. le control more easily. One surface painted unit The actual filter used, was the pale blue .black compensatingonesuppliedwithDufay- color, but a piece of celluloid tinted with phototintsor a square ofbluegelatine (iix exposure as used in portraiture) may be purchased. If the photometer is to be used in con- Grease spot aboutle junction with a voltage control unit the switch dia on art paper may be omitted, it only being necessary if a belltransformerisused,direct on tothe Fig. 1. -Details of celluloid disc Fig. 3.-Sectional elevation and plan of the grease -spot mains. and ring, and grease spot disc. photometer.

www.americanradiohistory.com 328 NEWNES PRACTICAL MECHANICS May, 1953 spotisbalanced out for each setting andsquare of a piece of paper, in turn in the anegative withthatofavailablepapers the position of the knob marked on a dummysame position each time,isavailable,theenables the most suitable grade to be chosen. scale. calibration will be all the more accurate, as The contrastrangeofthenegativeis Prepare a dummy scale(2in.dia.) andthere can be quite a variation in tone alongdetermined by taking a highlight and shadow attachtothephotometer,lockingitin a large test strip.Alternatively, test stripsreading and expressing the results as a ratio: position with the lock -nut provided ; replaceoftheshadowandhighlightercanbe Highlight reading ... so the pointer knob. prepared and the average exposure used. Shadow reading ... 48o Set the voltage controlunitasalready Now place the photometer on the easel in Contrast range ...48:1 the position occupied by the test strip at the described and with the enlarger head in the To determine that ofpaper,raisethe lowestpositioninwhichitisusedin portion ofit which was correctly exposed ;enlarger head high up on the column, stop practice, open the lens to the first " whole "balance outthespot. Leaving the knob in this position unlock the scale and rotatedown thelensslightly and throw out of stop number and throw slightly out of focus. focus. Using this dim light source, place Place the photometer in the centre of theuntilthecorrect exposurerequiredisina strip of paper on the easel and prepare a easel and balance the two light sources .byincidence with the pointer,then lock thegrey scale, each section receiving twice the moving the knob until the grease spot is not scale. The paper speed may now be readexposure of the previous one:Ex. 5,to, visible against the background. off against the pointer on the outer scale. 2o, 4o, 8o, 16o and 32o secs, may be used. Under these conditions the intensity of the To obtain the correctexposure for any light from the enlarger will never exceedother negative printable on this paper take Develop, rinse and fix the test strip. a reading on the middle tones or an average The ratio of the exposure required for the that used in practice, as with a negative in last pure white dividedinto that required position even in the highlight there will bewith thedialsetatthis particular speed, and read off the exposure required againstfor the first pure black gives the contrast some cut in the intensity. Ifa bulb of range of the paper. higher voltage is substituted later, however,the pointer at the balance point. it may not be possible to balance the spct Contrast range: with the head in this position and the lensMeasurement of Contrast Range Maximum exposure for pure white. wide open. The comparison of the contrast range of Minimum exposture for pure black. Care must be taken to ensure that a series of stops are used which will give half the lightintensity of the previous one. Two methods of marking are in general use, the English and Continental, a suitable series of stops being 2.8, 4.o, 5.6, 8,I1,-16, 22,and Plastic Thread Holder 3.2,4.5,6.3, 9,12.5,18,25, respectively.This Device, Submitted by Mrs. M. Garrick, Wona Prize in Our If any intermediate values are employed the scale about to be prepared will not be linear. Recent £200 Prize Competition When balancing out thespotfor each setting of the light intensityitisdesirable WHILE looking at my card of tangled -updrical shape and hinged to open, as in the to approach the balance point from each side stocking threads, the idea came to mysketch.The various shades of thread on in turn, and to take the average value asmind that ifa container were available tospools could be placed in the lower half, the actual point recorded. separate the different shades of threads andeach spool in a separate compartment.The After marking the firstpoint, close thealso stand up to a lot of rough handling itfree ends of thread could be fed through holes lens one whole stop and balance again, con- tinue until the lens is fully closed. Next, reset the pointer back one division and opening the lens to the original stop used, raise the enlarger head until a balance isobtained,closethe lens one stop and rebalance, proceedaspreviouslydescribed until about 12 points have been made. Snap clip By setting the pointer back one division before rebalancing by raising the enlarger head itis possible to check the accuracy of the last mark. Lever clamping When a sufficient number of points have thread against been recorded remove the scale, draw radial cylinder body lines through each mark and measure the angle subtended by each pair. Totalandaveragetheresults. Any deviation from the averageis duetothe non -uniformityofthevariableresistance employed. Next prepare on apiece ofplain card and markoff6deg.intervalsalongits edge,so making 6o divisions, which will Hinge 1 Lever in the eventually be used as paper speeds ; number \ thread released as shown in Fig. 3. \\position Pi Using the average angle subtended by each Theplasticthreadholder point on the dummy scale mark off a con- (shown open) and an end view centricscalein suchapositionthatthe showingthethread -clamping - pointed knob isjust in linewith it,and lever. END VIEW number the pointsI2,4, 8, 16, 32 (secs.), I, 2, 4, 8, 16 (mins.) as shown in Fig. 3. would save a lot of time and frayed tem-above each reel to the outside of the top half Cement thefinishedscale between twopers.This magazine type of holder wouldof the case, the protruding thread being stop- pieces of celluloid and fix it to the photo-be suitable for workbaskets or handbags.Iped from moving, except when required, by a meter. think it could be made of plastic, of a cylin- locking rod, as shown in the diagram. Determination of Paper Speeds 0 KSFORENGINEERS------. The speed of any type or batch of paper By F. j. CAMM is determined as follows: Screw Thread Tables, SP., by post 5/3. Dictionary of Metals andAlloys,10/6,bypost Set up the enlarger with a negative most 11/-. Refresher Course in Mathematics, 8/6, by suited to the type of paper whose speed is post 9/-. Wire and Wire Gauges (Vest Pocket Book), 3/6, by being determined, and make an accurate test post 3/9. Gears and Gear Cutting, 6/-, bypost 6/6. strip using the middle tones of the negative. Metric and Decimal Tables, 3/6, by post 3/9. Develop, wash and fix in the usual way, and Workshop Calculations, Tables and Formulae, 6/-, decide the correct exposure by examination by post 6/6. Practical Motorist's Encyclopaedia, 17/6, by post 18/, of the strip in white light.If a test strip FROM GEORGE NEWNES, LIMITED, TOWER HOUSE, SOUTHAMPTON STREET, STRAND, W.C.Z. holder of the type which exposes a small

www.americanradiohistory.com May, 1953 NEWNES PRACTICAL MECHANICS 329 Modern Inventions and New Ideas Exhibition Some of the More Interesting Exhibits at the Recent Show THE Modern Inventions and New Ideas By THE MARQUIS OF DONEGALL vented hexagonal chess, played on hexagons Exhibition opened recently under the of three colours.I am open to correction patronage of H.R.H. the Duke of In the inventions part of the exhibition afrom infuriated chess players, but I believe Edinburgh contained much of interest in anumber of recent industrialinventions orthatthisgivesthe King twelvepossible small space. discoverieswere displayed. One develop-moves, the Queen twelve directions and the One presumesthatthe sub -divisionofment was in the use of the cathode-ray tubeKnight twelve possible cells-or squares, as "New Ideas " was an afterthought to coverto reduce the regulation of watches from daysthey would be in the old game.All that I the large number of commercial stalls sellingto minutes by making the " tick " visible.Ascan say about it is that it would appear to be a diversity of novelties from tubes of plasticIsaunteredalongarotary machine wasnot quite as bad as three-dimensional chess, for blowing bubbles to a new and very effi- which I once saw demon- cient needle -threader. strated, or playing against The " New Inventions " section was under a machinewhich was the auspices of the Institute of Patentees, of guaranteedtowin,asI which Professor A. M. Low ispresident. once did at an exhibition in " Unhappily," said Professor Low, as usual Geneva.Not the least in- making a great deal of sense, " the inventor furiatingpartofthis seldom receives more than honour.Yet it machine,which wasthe is of ten from the humblest beginnings that inventionofaSpaniard, commercial sucess has sprung.This exhi- was a metallic voice from bition sets out to show how, by concerted the machine's inside which effort, inventors can be encouraged." cried" JaquealRey! " There has long been a need in this coun- every timeitwas check; try-whetherGovernment sponsored or addedtowhich,ifyou private-for somecentralorganisationto triedto move into check, help inventors on their way.Most of them the machine said in Span- are befuddled with the intricacies of patent ish," You can'tdo that law and are awed by the cost, operating on there'ere,"or wordsto a rising scale, of attempting to protect their that effect. property from the machinations of unscrupu- Housewiveswouldap- lous persons.Obviously, no individual can prove of the ironing -chair afford the kind oflitigationthat ensued -indeed,Ihaveoften right up to the House of Lords such as that wondered why it has been in which the Raleigh Industries' " Dynova " thought necessary to make patents were eventually set aside. ironing even more tedious by standing up to do it. Improved Car -park Themechanised car - park, of which there was a scale model to be worked by turning a handle, was. one of the best things in the exhibition. One mechanised section (Above.) Mr. W. Glinski, of London, with his new or unit of the car -park was inventionof Hexagonal Chess.By employing shown,andtherecould hexagonal cells instead of square the movements presumably be any number of the chessmen have been increased. ofthese 'unitsfor which (Left.) A new Ironing Chair which was demon- spaceisavailable. Each strated at the exhibition. A tubular steel crank unit takes twenty cars on links the ironing board to an ordinary chair, enabling an endless belt.The time a person to sit in a comfortable position. Invented calculated for releasing any by Mr. J.Vickery, of Croydon,Surrey. given car is one and a half minutes, and it is reckoned replacing broken -off handles onthat three hundred cars could be parked on tea -cups at the rate of twentythissystemwherepreviouslyonlytwo a minute. hundred could be stored with any degree of Another part of the exhibitionworking practicability. contained individual models by Even with two hundred cars the average about a hundredinventors.timeforreleasingtheleast -conveniently These weredisplayedinthe hope of catching the eye of theparkedvehicle would beseven oreight potential commercial sponsor. minutes.One can only hope that this inven- Cyclists' hand -signals and ation did, in fact, find a sponsor through the stop -light for the bicycle wereexhibition. useful and topical contributions Still in the Inventors' Section, there was and, while onthesubject ofan anti -dazzle screen, with a cut-out section accidents,mentionshouldtefor looking through, whilethe remainder made of the deck -chair that is eliminatestheglare. AnotherdeviceI guaranteed not to collapse. noticed was an animal controller, for clamp- ing the noses of such animals as bulls as an Chess Improvements improvement on the usual nose -ring.The As though checkmate wereegg -boiler, which automatically switches -off not already adifficult enoughwhen the eggs are ready, seemed a useful operation,somebody has in - device, as did the very simple idea of the

www.americanradiohistory.com 330 NEWNES PRACTICAL MECHANICS May, 1953

bread -board withaslitto keep the knifethat a gremlin had got into their telephone A revolving gear -box, claimed to increase straight, thus ensuring a regular slice. and rang off in a panic. mileage per gallon by 5o percent., was There is nothing particularly new aboutalso exhibited.It eliminates gear -changing, Home Improvements athermostaticfire -alarm,either, althoughbut whether it is an improvement on existing A compact unit to supply hot water, warmthe one exhibited was undoubtedly a very methodsofeliminatinggear -changingin airfor space -heating, and ventilation, wassimple device, relying on the fusing ofa motor cars is impossible to judge by looking one ofthe many exhibitscontributing topiece of metal at 16o deg.F. to establish anatit.It appeared no more bulky than an living comfort, as were the convertible bed -electric -bell circuit. ordinary gear -box. settee, the office -chair on which all the leg - Finally, in the Inventors'Section, there Lastly, there is no doubt that were we all jointswererubber -mounted,theportable is much to be said for a picnic -seat givingto install stoves such as the " M.I.," invented oven and reversible windows for cleaningback support and folding -up into the size ofand produced by an Anglo-Polish inventor in from inside. an umbrella. Bournemouth, or the many ether stoves of There were many ideas which were by There was a wool -winder transforming the no means new to me.For instance, I had,skein into a ball, the strands being crossedsomewhatsimilardesign,we wouldget severalyears ago,adeviceforrecordingover in such a manner that the ball couldwarmer houses and save a good fifty per cent. telephone messages in my absence installednot unwind accidentally. of our fuel bill.But will we?I am afraid in my office.There was nothing wrong In the industrial field,I liked the strapthat there is something about the old English with the machine exceptthatcallers, onand rollers for attaching to a suitcase, muchopen fire that will cause inventors of more hearing " Lord Donegall is out.Will youas has been done for many years with golf -efficient heating devices a headache for many please speaka message! " usually thoughtclub bags. years to come. MakinganAnemometer A Simple Device for Gauging the Speed of the Wind N anemometer, or wind speed measurer,56 teeth, and is fixed firmly by a set -screw to is easily made, but, at the same time,a spindle, D, which runs in bearings in the is a most fascinating piece of apparatus.two brass strips, E E. Four semi -circularcups form a kind of A dial of cardboard, graduated into 20 equal horizontal windmill which spins slowly orparts and numbered I 2 up to too lootoo is glued to the front strip. The front strip and half the dial is shown in Fig.1. The Box This is about 6in. long, Sin. deep and 4in. high.It should be firmly screwed together. A sheet of glass forms the front, through which Fig. a.- the dial is read. The bearing in the top of the General view box is formed by screwing a piece of sheet of the brass on and boring a hole just large enough completed to allow the spindle to revolve freely.The anemometer. hole in the wood should be a little larger to allow perfectclearance. Fixthemodel firmly in an exposed position, as high as Fig. 2.-Side view of the worm and pinion. possible, but so that it can be read easily. If made exactly to these dimensions, 56itpasses in one minute, orfiveminutes. revolutions of the cups-i.e., one revolution of the pinion and pointer-equals of aSuppose it moves from o to -1-10-: in one minute. mile. Each division on the dialis thus - -This means a speed of '!u miles in one toominute or six miles per hour.If the pointer of a mile. doesfourcompleterevolutionsinone When the wind isblowing, watch theminute, this is V5 of a mile per minute, which pointer and note carefully how many divisionsis 48 miles per hour. rapidly, according to the velocity of the wind. By means of a worm and pinion gear a pointer moves over a graduated scale, from which can easily be found the speed of the wind in miles per hour. The cups are beaten out of circular pieces of sheet copper, exactly 4.71in. in diameter, and when finished must be exactly Sin. in diameter. If you do metal work this is a simple task ;if not, you can get them made quite cheaply. The Four Arms These are made of Ain. diameter brass rod, 115n. long.The vertical spindle con- sists of a suitable length oflin.diameter mild steel rod. The boss, A, is 'lin. diameter andin. deep. Run a thread on the end of the rod and tap the hole in the centre of the boss ; then tapfourholesLin.deep exactly at right angles' to take the threaded ends of the four arms.Solder the cups firmly in position as shown and screw the arm firmly into the boss, which is then tightened down on the spindle. The worm wheel is fixed securely to the spindle by its set -screw (seeFig.I).The bottom of the spindle is pointed and runs in a hollowed bearing block of steel, B. A collar and set -screw, C, keep the spindle in place. The pinion, which engages in the worm, has Poffin says : "It's amazing haw Camm's harmonograph gets you after a time."

www.americanradiohistory.com May, 1953 NEWNES PRACTICAL MECHANICS 331 Magnet Escapement Radio -controlled

To "waiver relay circuit Model Actuators Notes on Their Construction, and How They Operate

ByF.G. RAYER as .1 milliamp, and various relays are especi-and the actual rotary force does not have to ally produced for this purpose, and should bebe provided byit. As aresult, heavier Rotating member used. mechanisms may be operated. Fig. 3.-An escapementactuator. When thetransmitterisoperated,the In simple models, rotationisfrequently armature is released, thereby completing theprovided by a twisted skein of elastic.A THE equipmentinaradio -controlledbattery circuit shown.If this circuit weresmall clockwork motor can also be used, or model may bedividedintothreewired directly to an electric motor, the motorsome similar form of spring -driven mechan- sections. First comes thereceiver,would run when the key at the transmitterism. Where some other source of continuous which may employ one or more valves. Therewas depressed, and stop when the key waspower exists, as with a steam -driven model, will also be a propulsion motor (except inreleased. This would only be sufficient in thethe toothed wheel may be driven through a sailing craft) and similar equipment connectedvery simplest type of model. friction clutch.It will then rotate each time withtheactualpowering ofthe model. A further circuit might be connected tothe transmitter is momentarily keyed. Betweenreceiverandpropulsionand/orthe lead " X," but this would, in most cases, guiding motors and mechanisms comes theserve no useful purpose. One circuit would Rotation of the axle upon which the wheel third section of the equipment-the actuator.have to be switched on when the secondis fixed is made to fulfil some useful purpose. Many different types of actuator can be made One means of accomplishing thisis made was off, since the armature cannot be broughtclear in Fig. 4.Here, a disc with projecting up, and the actual construction of suitabletorestin a central position.As a result, units is not particularly difficult.In a sense, pin is fitted to the axle.This disc may be the actuator transforms the received impulse made to take up any one of eight positions. into the desired action, which may be start- With the steering arrangement shown, this ing, stopping, reversing, or speed -control of To nvey would enable the rudder to be set in any the propulsion motor, or so on. circuit one of five positions, namely, straight ahead, half to port or starboard, and fully to port Actuator battery or starboard.Steerage of the model to this extent would thus be possible. A rotary switch with eight contactsis also driven by the spindle.In the circuit Electro magnet shown, provisionis made for forward and asternrunning, with" Off "positions between each.It would also be possible to wire up so that only one contact was unused, providing an " Off " position.Other con- tacts could then bring a resistance into cir- cuitfor "Half Speed " running. Or,if desired, only oneAstern " setting need be provided. To receiver In all cases switching of the circuit will Fig.i.-Connections for receiverrelay. Fig. 2.-A magnetic actuator. take place simultaneously with movement of the rudder. Eight different combinations may The types of actuator described here arethe second circuit could not be used to operatebe arranged for, and a good degree of con- primarily intended for single -valve and othera steering motor, or for any similar purpose.trol will, therefore, be secured. A sequence single -channel receivers. With such receivers, Without an actuator the degree of con-such as the following would be possible. all desired operations in the model must betrolis,therefore, the same asthat which Positiona. Rudder straight,full speed controlled by the opening and closing of awould be afforded by asingle on/off orahead. single circuit.Accordingly, inall but thechange -over switch in the model. Position2.Rudder half to port, full speed very simplest model, some type of ahead. actuatorisessential.Without an actuatorHow Actuators Function Position3. Rudder fullytoport,full mechanism,radio -control(with a single All actuators change the simple makingspeed ahead. channel receiver) would have to confine itselfand breaking of a circuit(as provided by Position 4. Rudder half to port, half speed to one purpose only ;for example, the start-the relay) into more complex functions. Oneahead. ing and stopping of a model boat's propul-method of doing this is shown in Fig. 2. PositionS. Rudder straight, half speed 1 sion motor. With an actuator there is almost Here, an electro-magnet and pawl assemblyastern. no limit to the amount of control which maycauses the rotation of a toothed wheel. Each be exercised.For example, the propulsiontime the magnet is energised, the wheel is Rotary switch motor could be started, stopped and reversed.caused to rotate one tooth. Such an arrange- It could also be made to run at half speedment isquite straightforward to make up. in either direction.In addition, steerage ofThe magnet needs to be fairly powerful, and the model, both when in motion forward orthe pawl should move just sufficiently to take astern, could be effected.If desired, otherone tooth each time the circuit is energised. actions (such as the rotation of gun -turrets) By keying the transmitter, the wheel may could be provided for.It will, therefore, bebe made to take up any one of eight posi- seen that the realistic operation of a modeltions.If necessary, undesired positions may makes an actuator mechanism essential. be passed through almost instantly by key- ing the transmittera number of times in Principles of Control succession. With a single -channel receiver, the trans- A different type of actuator is shown in mitteriskeyed sothatacarrier -waveisFig. 3.Here, the wheel is constantly endea- radiated when desired. This causes thevouring torotateinthe direction shown. anode current in the receiver to fall, so thatEach time the magnet is energised, the wheel a relay is released.Such a relayis shownis allowed to rotate one tooth. This arrange- Slotted arm Spring in Fig.I.It is of sensitive type, so that itment has a number of advantages in some will operate with a current change of as littlecases.The magnet only acts asa release,Fig. 4.-A reversing ani steering arrangement.

www.americanradiohistory.com 332 NEWNES PRACTICAL MECHANICS May, 1953 Position 6.Rudder half to starboard, half In Fig 4, reversing of the motor is obtainedmechanisms where mains -voltage circuits are speed ahead. by reversing the polarity of the supply. Thisinterrupted. Position 7.Rudder fully to starboard, fullcan only be accomplished by using a per- speed ahead. manent -magnet motor.If the motor has aMotor -driven Switching Position 8.Rudder half to starboard, fullwound field, the polarity of the supply to A small motor may be used to operate a speed ahead. either field or armature should be reversed,rudder, or other units, including switches In each case undesired positions are passedto reverse the direction of rotation. of suitable rotary type. Such switches become through quickly by keying thetransmitter almost essential when very complex circuits a number of times in succession.The modelSecondary Relays are necessary. may thus be controlled to an extent permitted The receiver relay may complete a circuit A method of operation is shown in Fig. 6, by the selection of any of the positions. which energises a secondary relay with addi-where a small motor drives a rotary switch Many of the simpler actuators provide notional contacts. More complex circuits maythrough worm gearing. " Yaxley " rotary intermediate position of the rudder, and eventhen be used. A reversing circuit is shownswitches, such as used in radio receivers, are these are quite effective, since the model canin Fig. 5. A double -pole change -over relaysuitable, provided the spring locator mechan- isused, and wiredsothat the motoris ism is removed. Double -pole change -over relay reversed. When suchamethod ofswitchingis This type of circuit has a number of appli- cations, usually in conjunction with an actua- Multi -pole rotary The type switch To tor such as has been described. receiver of relay used here is of about 200 to 500 Worm relay) ohms resistance, is quite small, and normally gearing energised by a 3 to 4.5 volt dry battery. The meal sensitive type of relay such as used in the 6 16m. receiver is not required.For example, the controlling circuit may be transferred from one motor or actuator to a second, by the change -over switching of the relay. This change can, in turn, cause yet other relays To and mechanisms to come under control. motor Secondary relays must also be used when V the current flowing is heavy, or of fairly high To circuits To battery voltage.The contacts of the receiver relay Fig. 5. Motor reversing by means of a secondaryoperate a trifle slowly, and the contact pres- Shaft driven from motor relay. sure is small, especially when the model is at range. Accordingly, the contacts will- not be turned upon a new course in either direc-satisfactorily make or break circuits passing Fig.6. -Multi -circuitswitching. tion.If reversing were not desired, such ana large current.They will, however, ably actuator could provide for full speed ahead,deal with small currents, at low voltage, andadopted, there is almost no limit to the com- full speed to port, full speed to starboard,can, therefore, serve to control the energisingplexity of the circuits which may be used. and " Motor Off " with rudder ahead. Theof a second relay.Such a relay might beThe motor should, for preference, be rever- wheel ontheactuator mechanism wouldpowered by a 3 or 4.5 volt battery, as men-sible, as described. Such switches may bring require only four teeth. This would make thetioned,anditscontactscoulddealwithinto service further sections of equipment, method shown in Fig. 2 impossible, but thathighervoltagesandcurrents. Such a such as small motors to rotate turrets, latch- shown in Fig. 3 would be equally suitable.secondary relayisessentialin non -mobileing relaysto switch on lights, and so on.

through which the stone, starting from rest, would travel in / second. Back to FirstPrinciples As regards the first calculation, since the positivedirectionis now downwards, the 4. -Gravitational Force By W. J. WESTON equation of motion is : v2= u2+2gh, or since u=o (the stone starting from rest), indeed,isone of the things I.The velocity at any point is: v=u-gtv2=2gh. that we are bound to accept, without II.The space travelled is :s=-ut gt'. The Answer: Space through which a body explanation,as a condition of our lifeIII.And, combining I and II: v2=u2- 2gs.starting from rest falls in / second =1 gt2= inthe world. Through experiment and Since, therefore,at the highest point -(16 x )ft. =oft. observation we are able to say much withwhich we denote as h -v =o, then u2=2gs. The velocity of the stone when it reaches confidence about the force -about the results TheAnswer. s=128 x 5 - (32) x 25 =the window is 4ft. in the / second, i.e., 8ft. of this tendency towards a centre of attraction.24oft. up. per second. We speak of the " law of gravitation " as 128 And, since v2=2gh, being that whereby " the attractive force of But the greatest height is reached in - 82=2 X 32h=64h. bodies variesdirectlyas their masses and gt That is, 8=8N/h or inversely as the square of the_distance betweenseconds, i.e., t is 4 seconds. The height above the window is, therefore, them.' But, assuming that Newton's won- After 5 seconds, therefore, the ball has derful guess is absolutely correct, this is abeen moving downwards for r second, i.e., The Problem : A ball is propelled vertically statement of what happens, and what we areover 16ft.The total distance, therefore, iswith a velocity of 56ft. per second. At what impotent to change.The explanation of240+16 up +16 down=272ft. height is it moving at 4oft. per second ; and why each particle of matter tries to come Since theballfalls below the point ofwhat is the time between the instants when closer to every other particle still eludes us ;projection, s 'becomes negative.So : it is at this height ? we only know that it does. -120=128 X t -160 The Comment :'Thisis merely a variant The Problem : A ball is thrown vertically i.e.160-128t =120 of the first problem studied, and we apply upwards at a speed of 128ft. per second. 15 the equations with the necessary modifications. Find where itisafter 5 seconds, and the i.e. t2-8t = 'total distance it has actually travelled.If it 2 The Answer :The equationof motion 47 where u is the initial upward acceleration and falls past the point of projection into a well(Add i6 to each side) v the velocity at the time, and h is the height in noft. deep, find when it strikes the bottom. 2 feet reached is v2=u2-2gs. The Comment : We work on the assumption V23.50 = 4.82 Or 40 X 40=-56 X 56-2 X 32S that the accelerating effect of gravity -we (t - = i.e., 64s =562 -=40926=x(5i66+ 4o) (56 - 40) shall denote this by g -is 32ft. per second; t =8.82seconds. it is a little less than this up the mountain, s=24ft. a little more than this down the mine.If The Problem : If a stone falls past a window we denote the number of seconds by t, then8ft. high in half a second, find the height An upward acceleration of 4oft. per second gt is the acceleration due to gravity ; and / gtfrom which the stone fell. is wholly lost in will be the average speed. The distance The Comment : This involves the calculation -40 seconds, i.e., inI seconds. travelled, therefore, isigt2. of the velocity of the stone when it reached grt If now we denoteaninitialupwardthe window :thatvelocity would operateAnd since a downward acceleration of 4oft. acceleration asit, we are able to expressduringthepassageof the window overper second is gained in the same time, the these three equations: second. We need to calculate also the spacetotal time required is :21 seconds.

www.americanradiohistory.com May, 1953 NEWNES PRACTICAL MECHANICS 333

The Work of Bernhardt Schmidt and its Relation to Telescopy and Other Sciences By FRANK W. COUSINS, A.M.I.E.E.,F.R.A.S. (Concluded from page 292, April issue) reachesthesphericalmirror, D,Newton telescope14 which will be erected which reflectsitas a convergentat Hurstmonceux in Sussex will be of the beam on to the flat mirror, E, atSchmidt construction and the largest, in the 45 deg. to the axis of the cathode-world. The main mirror is to be 98in. dia.; ray tube.The light from E passes throughtheSchmidtcorrector Mirror plate, F, on to a second mirror, G, and finally on to the screen, S, at xN-Avr K. Thisprovidesanenlarged

image of the picture element, A, \ Our artist'simpressionofthe Schimdttelescop2at at K, and is applicable to all the Mount Palomar. other picture elements. Corrector One other use of the Schmidt plate THE second departure is due to Maksutovsystem outside of astronomy isthat of its 9,10,11. Dr. Linfoot discussed this inpart in roentgenology.It has been stated by totheBrockman13thattheSchmidtsystem is Image " The Observatory "and referred surface opticalsystemastheMeniscus -Schmidt.usedtodetectcancersofthestomach. The arrangement is seen in Fig. 12.TheCancer, like tuberculosis, can be detected by aspheric Schmidt corrector plateis replacedX-raymethods,buttheexamination is Fig. r4.-FoldedSchmidt. at focal ratios of f/3 and apertures up tohindered by the very much lower trans- 2 or 3ft. by a meniscus lens, the sphericalmissivity of the gastro-intestinal regions towith a corrector plate of 85in. dia., and the surfaces of which are nearly concentric withX-rays as compared with the transmissivityphotographic plateswillbe i4in. x 14in. ofthechest,andthismeansthattheWhat will such great instruments tell us of the mirror surface.The primary colour our universe ? The answer to such a question error ofthemeniscusiscorrected bya fluroscopic image isfaint.To avoid long spherical interface which takes the form of isnot possible.We can read again,in a doublet with its two glasses of different humility, the words of Prof. Grant quoted dispersions and the same mean refractive in the preamble to this article, and note that index. the telescope has ever been an iconoclast in The off -axis colour errors introduced Image its bythesphericalinterfacethoughnot _surface treatment of the contemporary view- negligible are harmlessly small. Folded and Solid Schmidt Cameras Finally, two adaptations of the classical Schmidt are not without interest.The solid Schmidt camera, Fig. 13, and the Fig. t3.-Solid Schmidt. foldedSchmidt camera, Fig.14,due to exposure and over -dosageofthepatient Spherical mirror with X-rays a fast lens system is essential. Here Schmidt's system lends itself to a really fast camera design, and this, though in the earlystagesofdevelopment, may make possible mass -radiography of the stomach as now doneforthechestinthe war on tuberculosis. Newton Telescope at Hurstmonceux In closing this appraisal of Schmidt's work itisgratifyingtoreportthattheIsaac Fig. 12. Maksutov,orMeniscus -Schmidt telescope. A close-up veiw of the eyepiece end of the Schmidt Cassegrain telescope at St. Andrews University. Hendrix, which places the image surface in a readily accessible position. reducing the speculation of many philosophers Inconsidering the folded Schmidt to ashes. Thefuturemay well be camera it is convenient to draw attention to iconoclasticfor many currentideas;the the optical system used in modern projection enigma of the universe is far from solved. television.Fig 15 shows the system used by Mullardla.Incontra -distinction tothe REFERENCES telescope aspect we have considered through- 9." Journal of Optical Soc. America " 34, May, 1944, p.27o. (New Catadioptric Meruscus System.) out :the televisionapplication placesthe D. D. Maksutov. image on the image surface asitsinitial so." Scientific American," Oct., 1944. stepinthelightpath ;andtheimage 11." The Observatory " 66, p. 239. 12." Mullard Outlook," Vol 2, No. 4, Jan., 1952. surfaceisthefluorescentscreenoftheFig. 15.-Schmidt sys- 13." Journal British Astronomical Association," vol. cathode-ray tube, AB (Fig.15). Consider tem for television. 14.`?.TFrp.ne5s6kogress of Science,"April, 195o, p. 8 ; point A, a singlepicture element.LightCompare with Fig. 14. also " Optical Instruments, Proceeding of,'' London radiated forward from picture element A Conference, 595o.

www.americanradiohistory.com 334 NEWNES PRACTICAL MECHANICS May, 1953 111 ST EOSCOPES Instruments Suitable for Viewing Two -lensed Camera Slides and Single-lens Camera Stereos ByE. W. TWINING the other.This is stereoscopic photography,possessing allthe solidity and relief of the the result of which is a pair of photographicoriginal subject. prints, mounted side by side, which, in order to be viewed stereoscopically, must be lookedStereoscopefor Two -lensedCamera at through a stereoscope. Pictures Obviously, the two prints must be mounted Itisproposed to give drawings of two incorrect order.If the left-hand photo-stereoscopes, dealing with the larger one first. graph were placed on the right side of the Thisisofthe size and type whichis mount and the right-hand on the left, thenrequired for viewing pairs of pictures taken the more distant objectwould appearin with a double -lensed, orthodox, stereoscopic

pEOPLE who have lost the sight of one eye can never see objects in the round or in relief, and are only able to judge distances by moving the head from side to side.The normal sighted person, using both eyes, canjudgedistancewithout moving the head.The reason why this isso and why all objects in nature appear in relief ; why they have depth as well as breadth and height is because the images formed on the retinas of the two eyes are not exactly the same ; the right eye sees the subject from a different viewpoint from the left.Thisis on a table a bottle and a candle ;let the candle be the nearer almost in line with the bottle.Now close and then open one eye, then the other; do this repeatedly in rapid succession and it will appear that the candle keeps moving, first to one side of the bottle and then to the other.This is stereoscopic vision. If we substitute for the eyes two photo- graphic lensesattached toadouble -width camera, fitted with sensitised plates or films, Fig. 1.-Showinghow thelenses bend thelightrays. we can photograph exactly what the two eyes haveseen. The tworesultingpictures,front of the other and the perspective andcamera, using single plates which are long takenbydifferentlensesfromslightlysolidity ofthe objectswould be reversedenough to accommodate two views, side by different positions, may appear to be alike,and all wrong. side, each measuring 3fin. by 31in.This but if the subject photographed was a simple The stereoscope compels the left eye tomeans that the optical centres of the lenses one, likethe candle andthebottle, thensee the left-hand picture and the right eyemust be34in.apart,whichtheynearly careful examination and, perhaps, measure-the right-hand.The two views arethenalways are.In thestereoscope two lenses ment,willshow thatthecandlein onesuperimposed by the optic nerves, producing,are required, onefor each eye.Now, as picture is a little nearer to the bottle than in inthebrain,theeffectofonepicturethe human eyesareapproximatelyzlin.

OPTICAL CENTRE LINE

Fig. 3.-Side and front end elevations of a large stereoscope.

www.americanradiohistory.com May, 1953 NEWNES PRACTICAL MECHANICS 335

MOUNT any one of which canaffecttheresults Fr:-.1 PICTURE-4F.-- et. enormously. The second scheme for making stereo- scopic pictures and a stereoscope for view- ing them may be welcomed by thousands of people who own and use ordinary box -type cameras, or any hand -camera which, having a flat underside, will stand upon a flat sur- face.There are quite a number of modern cameras of this type on the market, ranging Fig. 2.-Cutting up the reading glass. in price from £50 or more down to a little over £t, all taking pictures either 3,tin. by apart andas they havetoview pictures zlin., or zlin. square, and all suitable for spaced at 34in. centres the lenses must, to I propos:, to describe. ..---- use in the manner I some extent, act as prisms and possess the CENTRES OF PICTURES There are others which fold up, with bellows faculty of bending the light rays from the extensions, andthesealsocan beused, pictures and at the same time magnifyingFig. 6.- Pair of 38in.>: 2 lin. prints mounted.though the trip ad top may have to be made theimages.Inthistypeof stereoscope, a little differently to suit the bottom of the therefore, ordinary circularlensesare not camera. usually used, but they are shaped as shownUsing the Single -Lens Camera in Fig.5, which figure also shows how the I have mentioned the two -lensed stereo-Stereoscope for Standard Negatives picture images are caused to converge to thescopic camera for the .taking of pictures, and when itis necessary, or advisable to make Firstwithregardtothesteroscope: eyes.Such a pair of lenses can be made by Fig. 5 shows asomewhatsimplycon- simply cutting into halves, on its centre -line,both exposures simultaneously, the double -structed viewing instrument. Fig. 6 an ordinary reading -glass lens of about 8in.lensed instrument is essential, but for ordinary shows the correctmeasurementsand focusandzlin.dia.Withthefurtherlandscape work aquarter -platesingle-lensarrangement for a cardboard mount carrying removal of other thin portions, near the edge,camera canquite well be used, mounteda pair of stereo prints, either 3* x zlin. or two square prismaticlenses,as drawn inupon a cross -sliding head to the tripod stand.zlin.square, thelatterbeing,ofcourse, Fig. 2, are the result.The stippied portionsIn this case the two views are taken onetaken by one of the many cameras which are the parts to be removed. after the other, first with the camera on theare made to produce square pictures.These The cutting of such a lensasthisisa left and then on the right.In some respects,mounted photographs are sometimes termed somewhat delicate operation, unless one is aand wherever itis possible, this method has" stereoscopic slides,"and, for want of a better title,Ishall use the word, although 924' they do not in any sense slide.The double dot -and -dashlinesacrossFig. 6indicate the positions which the zlin. square pic- tures are to occupy.Any titles to the pic- tures can be written underneath, and should appear under one picture only, so as to be read by one eye.With 31in. pictures, titles may be put on the backs of the mounts or in fine writing at top or bottom. The stereoscope is made of cardboard ; the yellow -brown type which is known as " strawboard."Itischeap andisreadily obtainable. The thickness should be not less than 5/56in.All the pieces shown and dimensioned in the drawing, Fig. 5, should be cut out with a pointed knife and steel straight -edge, cutting being done preferably on glass. Then all the parts should be given a good soaking coat of strong size and allowed to dry thoroughly. The bottom of the stereoscope is made to form a box which, when closed, should hold from55tozoslides,according totheir Fig. 4.-Plan view of the stereoscope. degree of flatness.If prints are pasted on both sides of a mount, back to back, the card skilledglass -cutter,anditisone whichadvantages, because both pictures are takendoes not tend to curl, and the slides should should be done with a glazier's diamond inwith the same lens and with exactly the sameremain flat.In this way thirty or forty views preferencetotheordinaryglass -cutter'sstop value.When two lenses are fitted oncan be got into the box of the stereoscope. wheels.Itis recommended that all of the astereo -camera they haveto be perfectly The folding parts of the instrument are cuts be made with the diamond before anymatched: for colour in the glass, for equiva-joined to each other by hinges formed by one fracture is completed ;then, obviously,lent foci,for diaphragm apertures and forstrips of fabric, arranged as in the enlarged the first cut to be parted isthe main onemounting on the front of the camera, factors,sketches, at the left-hand lower corner of across the centre of the lens.It might be advisable to get a glass -cutter to do the job. 4>t" INSIDE The two lenses are mounted as shown in -aPICTURE TO TITRE Of LENSES Figs. 3 and 4, which drawings give all the details of the construction of the stereoscope. 2-vf -CEtITRIS-.4

Both the lens panel and the picture stage, r I ' together with a handle underneath, are made to fold, for convenience in storing.As may be seen, the stage is made to slide, for adjust- Nor ing the focus to suit different sights.Loose- ness in slidingis prevented by a strip of ..4OUTSIDE---+r-0- OPE PI sprint -brass, which should, atitsmiddle, i// pressdownwards onthemainbar,or baseboard. Although ordinary grained wood is shown in the drawings, plywood will be most suit- able for all the principal parts and only a few bits of straight -grained material will be DETAILOf FABRICH 1146E9 called for.To hold the lenses in the lens CLOSED panel, either wood veneer or cardboard may [--IV OUTSIDE - be used ;the former being best for appear- ( INLARGED) ...... ance, if the whole instrument is polished or varnished natural colour. Fig. 5.-A folding stereoscope for 31in. by 2Iin. pictures.

www.americanradiohistory.com 336 NEWNES PRACTICAL MECHANICS May, 1953 the two camerapositions,a distanceofends are inwards, the carriage is stopped at LENS 31in.,thecrosslengthoftheplatform3kin.separation, whileifthe turnbuttons between the side ledges will depend upon theare placed parallel with the ends of the plat- PLAN OF FROM EDGE Or BASE BOARS. width of the camera.Cameras vary greatlyform and with neither end inwards, the full in width, as well as in other dimensions, andtravel is available for 41 -in. separation. Other the reader must make the platform to suitintermediate travels are possible by having his own particular camera.Measure thethe buttons differently placedat opposite width of the camera at the bottom, add theends. The plan view of one end of the result to and the sum of the two willplatform, with a bit of the camera cross -slide be the length for the platform between theshowing, is added at the top of Fig. 8.The ledges.In using the platform the cameraplatform and the main part of theslide must be pressed up into the angles formedshould be made of plywood, the latter of by the front as well as the side ledges, thus5 mm. and the former of 9 mm. thickness, the camera will be kept square and point inthat is to say 3/16in. and kin. The rebating the same direction for both exposures. of this can be such that two of the plys are left the full width of the platform and three Varying Lens Separation plys removed to form the rebate. The finish Another, more elaborate scheme is drawncan be shellac varnish, leaving the wood in Fig. 8, where provision is made for vary-natural colour or, on top of the shellac, a ing the amount of movement of the camera,coat of eggshell -black lacquer can be given. in order to increase the separation of the lens positions from the standard 31 -in.toClose-up Stereos 4 -1 -in. withseveralintermediatemeasure- Should the reader wish to make stereo- ments.The purpose of increasing is some-scopic views of really close-up objects and times important and this ability to increasecan put magnifiers over his camera lens, he is where the single camera scores over thecan make slides of such things as still life, Fig. 7.-Using a box camera for taking stereo-full, double -lensed, type, where the lensesfruit and flowers and models, etc.In that scopicpictures. are fixed.If photographing a distant land-case the camera movement will require to scape,with mountainscenery,withoutbe less than 3/in.; probably much less, say, Fig. 5.These strips are not allowed to stickforeground and no objects nearer than, say, 2tozlin. or according to thesize and to the edges of the card but only to thesooft., a separation of 3iin. would not bedistance of the object.Whatever the camera inner and outer faces,so that the hingedsufficientto give the necessary amount ofmovement is, be it tin. or 4zin., flowers or piece of card has a full 18o deg. of move-stereoscopic relief and solidity.In such adistant landscape, the mounting of the prints ment. case 41in. would be only just enough to yieldwill be the same, as given in Fig. 6. I suggest that the stereoscope be covereda realisable amount.In taking pictures for I think itis perhaps advisable to remind entirelywithgoodqualitybookbinders'the stereoscope it is the variety of distancesthe reader, before he sets out to do stereo- cloth of any approved colour, preferably darkofforegroundobjects whichareall-scopic work with his one and only hand green or black, and if this idea is adopted,important.The following may be lookedcamera, that only " still " pictures can he bits of the same cloth can be used for theupon as a safe guide-A: 6ft. to zoft., taken.There can be no snapping of moving hinges, such hinges being put on before theB: loft. to soft., 3kin.; C: soft. and beyond,objects; even in pure landscapes there must cloth covering. 41in.The lowest figure, 6ft., is the shortestbe no wind-blown tree movement, but the The lenses, since these will be approxi-distance that can be allowed between theuse of the instantaneousshutter can be mately the same distances apart as the cen-nearestpartofthe foreground and the tres of the pictures, do not need to be pris-camera; not because it would be out of focus PLAN OF ROTARY / matic, and two exactly similar lenses, either-that can be corrected by stopping down- STOP PIECE/' plano,convexordouble convex,willbebut because, were it nearer, than 6ft. there required.They should each have a focus BASEBOARD of 4in. and diameter kin.If they are piano - :ROSS convex, insert them in the spectacle plate SLIDE with the convexed sides towards the pic- tures.They need not be cemented or stuck in any way, but. will be held in the " plate" by two rings of card, glued on either side of the strawboard.The remaining details of the stereoscopewill be obvious from the drawing.

STOPS The Tripod w:314-cENTRES A I C B A CENTRES 8 The camera arrangement for taking the 4,1c rims r pictures involves the use of a folding tripod of thesize usual with quarter -platefield r-64-77 it cameras, having folding and sliding legsand a wooden top. There are tubular brass - legged tripods, with small metal tops, but although they are somewhat smaller when shut up and atrifle more convenient for carrying, they are too large to go into the pocket ;and, what is of greatest importance, are too subject to vibration, even from light wind pressure, to be of any use in making time exposures in stereoscopic work.I have one wooden tripod which folds and slides, Fig8.-Tripod top withcross -sliding camera carrier. made of ash, which weighs, with itstop,would be difficulty in seeing that particulardropped, in most cases of doubtful light, only and itis the upper part of thisbit of foreground stereoscopically; when thewith advantage.The best way is to stop which is drawn in Figs. 7 and 8.I stronglytwo pictures are mounted the eyes would notright down, getperfectly sharp detailin recommend the interested reader to obtainbeabletosuperimposethe two imagesforeground and distance and make " time" one of these. though all the rest of the picture may be inexposures, though, of course, the timing of proper relief. both exposures must be exactly the same. The Platform Fig. 8 shows the platform, on the tripodWith the smallest stop and long exposures The most simple arrangement for a fittingtop, with rebates, on each of the long edges,there is no difficulty in getting the timing to go on the tripod top is a rectangularto receive a sliding carriage or cross slide, exact.Of course all this depends upon the wooden platform with a ledge around threewhich carriage is made so that the cameracamera, the lens, the type of shutter fitted sides of it,as shown in Fig.7.On thisfits snugly into it.The platform is madeand the speed of the film being used. With the camera is placed, first on one side and thelonger than is required for 3iin. separationan expensive outfit having a lens working at first exposure made, and then on the otherand, at each end, itis fitted with a turn -a big full aperture and depth of focus and side for the second exposure.No dimen-button having unequal ends. When the longerwith high-speed film, time exposures would sions for the platform are given, the reasonends are both turned inwards to A, the crossbe rarely necessary; only perhaps in building being that since the lens must move, betweentravel of the slide is 3in.; when the shorterinteriors.

www.americanradiohistory.com May, 1953 NEWNES PRACTICAL MECHANICS 337 The Manufacture of Pins With aDescription of the Types of Machine Used

AQUANTITY of the wire produced in By H. SANDERS From these pointing mills the wires are most countries goes into the manufac- passed to a hopper, whence they are periodi- ture" of safety -pins, particularly those Precisely as the wire is severed from thecally removed. embodying a sheath of metal to actas astock, a finger descends and forces the wire There is another method in which the pin receptacle for and protection of the point.squarely into the gaps of the drum teeth.is wholly made in one single machine. Figs. 3 In making these, the preliminary stage com-The teeth thus engage the wire and carry itand 4 showtheprincipleofonesuch prises straightening, cutting off and pointingforward untilitis forced to pass under, amachine, the invention of B. L. Goodman. the wires.This cannot be done exactly assaddle formed like the drum periphery.TheIn this machine the strip is fed by a couple with needles.In the first place, itis vitalwire is held square by the teeth, and simul-of rolls across a drum, which slightly oils the that the cut-off wires should be of identicaltaneouslyitisrolledover length, or it would be impracticable to per- againstthesaddlebythe , Cut-off form thelater operations.The necessaryrubberdrum. Behindthe accuracy cannot be secured when the grinding Feed rolls drum is a plate against which Revolving straightener of the points is done by means of a wheelthewiresbutt,andthis running away from the point.The grindingensures the dead accuracy of must be done towardsthepoint, and intheir frontal protrusion. Figs.r and z the principle of the machine In front of and alongside used is indicated. the drum on the right isa The wire supplied in the normal coils isswiftlyrevolvingsteelmill, placed on a swift to the rear of the pointinghaving teeth of file type. This machine, and pulled forward by a revolvingis concave, as shown in Fig. straightener consisting of a number of pegs inz, and islocated in such a arevolving frame. The actualdrawingway in relation to the drum through of the wire is carried out by twothat the requisite curved taper Fig. 1.-Method of grindingthe points of he pins. feed rolls actuated by a double -crank feedingis acquired by the pin point. mechanism. Each strokeofeithercrankThe mill, revolves in the direction of theunderside of the strip.It then passes be- carries forward sufficient wire to form onepoint, and the grindingsare removed bytween 'two press tools, which form a blank, as pin.This pin is then cut off. means of an exhauster.The diameter of theshown in Fig. 3.This blank is then carried mill is approximately 2-2.5in., but it revolves through to another press, in which a blunt - The Drum at 5,000 r.p.m. and rubs rather than cutsnosed punch drives the blank through a hole To the front of the machine is a barrel oraway the metal.The file teeth are speedilyin thedie,thus making the cap in one drum which rotates on a horizontalaxis,worn down, after which the mill functionsoperation.Under the die are two fingers, roothed drum Presses Drawing -through Capping Stec,' Blanking Head forming tools Presser mill Rubber drum behind here Spring fingers

Coiling Hopper of spindle Spit wires

Picking up Par Transterer Poo t ing mill Coil of caP strip Carborundum mill Figs.3and 4.-The lank principle of the pin -mak- Fig. 2.-Details of the drum and the ing machine invented by steel mill. B. L. Goodman. and as the wire comes forward it protrudesin the same way as a circular friction sawwhich are rocked forward as soon as they over this.The drum is composed of threeused for cutting up steel girders.In short,receive the cap and force it through aslit individual discs, two of them, those external,its high speed causes it to burn rather thanin the bolster.The cap is then transported have teeth round their peripheries.Thesecut its way through.Eventually, when theto a capping press, with its open end to the teeth are generally inserted so as to makeserrations have worn down to nothing, andfront, awaiting the shaped wire.Care must replacement easier in the event of damage.the mill has acquired a high polish,itis be taken to prevent the drawing -through tools The middle disc is rubber -covered and causedremoved and re -toothed.The friction offrom scratching the metal, these scratches to revolve by interior gears at twice the ratethe mill brings the wire to a red heat, but asbeing due to the presence of a slight fash or of the toothedsections, butinthe samesafety -pins do not have to withstand stressesburr on the upper edge of the blank, which, direction. likely to be serious, this heating up of theif not perceived, scores every cap and quickly wire need not be taken into account. grows bigger, since they become glass -hard and can only be eliminated by hand rubbing. Forming pun& Head The Steel Mill finishing From the steel mill the wire passes to aHead -forming Tools tool similar carborundum wheel situated as shown The pointed wires are fed from a hopper Ceiling spit in Fig. 2.Though this mill may be at anon the right-hand side of the machine, and (fixed) angle to the drum, as shown, it is sometimesare picked out singly by a rising bar, whose Formoo bed placed in a frame parallel with the drum face,upper edge is nicked with a vee,so that each and reciprocated in such a way as to followtime it lifts it takes a wire.A light presser Driving peg the form of the point.'Lastly, a third millmaintains the wire in the vee until horizon- barely makes contact with the point atatally moving spring fingers arrive and seize rather obtuse angle, thus givingitaset it.These transport the wire to the head - corresponding to that of an edge tooth. forming tools, as in Fig. 5.The stub end A steel millis used in advance of theof the shank isheld between punch and carborundummillbecauseotherwisethebed.The middle of the wire is supported Fig. 5.-Showing how the horizontally movinglatter would be too quickly destroyed byby a stationary spit emerging from the end fingers transport the wire to the head -forminghaving to grind the square point.This theof a coiling spindle.This spindle also has tools. steel mill is much better fitted to do. an out -of -centredriving peg which bears

www.americanradiohistory.com 338 NEWNES PRACTICAL MECHANICS May, 1953 against the other side of the wire and coilsno doubt, be consulted.Itserves as an it about the peg as the spindle revolves. Theindication of the ingenuity devoted to the spindle revolves itimes so as to make themanufacture of these useful articles. spring loop, while simultaneously the head - finishingtoolfunctionsandfinishestheSafety -pins shaping of the J -end to be fixed in the cap. In Fig. 6is shown adifferent type of Thus, the wire shank is now finished, andmachine,madebyEdwardWhite, of isreleased by the reversal of the coilingRedditch.In this machine the wires are spindle for a quarter of a revolution.Thiscoiled into the form of a safety pin.The liberates the central spit from the grip ofmethodistobeginwithwiresalready the wire. Axial withdrawal of thespitpointed on thelinespreviously indicated, then occurs, and the coiling spindle drawsand then to pass them through this machine. back to permit the transfer fingers to seizeThe caps are then soldered on, being made the pin.Immediately the fingers seize, thewithahand press,theresultbeing the head -shaping tools let go the other extremityfinished safety -pin. of the wire. Thereare,naturally,otherformsof Other processes following include scour-safety -pin in addition to those with a metal ing, cleaning, plating and the like.Itis sheath or cap.One such pin is composed probable that the machine described abovewholly of wire, having a coiled loop at each is no longer obtainable, but the patent can,end,andismanufacturedinmachines based on similar principles to those already described.In these instances, the pointed wire is removed from the hopper, and oneFig.7.-White'sautomatichairpin -making end inserted in a press having a vee notch machine. intheanvil,withacorrespondingtool above.The coming down ofthepresswire is coiled, placed on a swift, and pulled presses out the wire end into a spoon shapethrough a number of pegsthatserve to whose recess finally serves as a sheath forstraightenit. The wire when straightis the pointed end of the pin when closed. projected for cutting off by a cam -actuated Another outletfor wireisthe hairpin,tool.The wires are then rolled forward though this, of course, isless popular thanon their own axes and travel across the faces it was some forty years or more ago. Fig. 7of two mills, running at high speed, and showsWhite'sautomatichairpin -makingprovided withfileteeth. The angle of machine, whichautomatically producespresentationensureseliminationofthe hairpinscomplete,straight from thecoilburr or fash due to the cutting tools, and ofwire,eitherplainor crimped. Theforms a blunt, cone -shaped point, which is actual work of bending the pinsiseasy,all that is necessary.The wires then move being done by simply tugging a length offorward and fall on to guides where the wire by the middle between two stops, thusbendismade. Ifcrimpsaredesired, folding the two ends together. crimping tools then seize the wire and carry Fig. 6-Safety-pin coiling machine. The principle of this machine is that theout their work.

angle between so deg. above orso deg. ADJUSTABLE WING below the horizontal. All -metal Wings Full span leading edge flaps are fitted and the wings are all metal structure with ply- RESEARCH AIRCRAFT wood covering the leading and trailing edges.

THE Short S.B./5-the "adjustable 1.- ICC- 3" -.1 wing " research aircraft which first flew Tail plane at maximum negative last December-has now completed a con- incidence position siderable number of flights.The research programme for the aircraftiswell under way and further details about the S.B./5 can now be released. Its main task isto investigate problems which arise in the handling of swept -back wing high-speedaircraft. Difficultiesare 43. 6° encountered in maintaining full and imme- 47.4" Dependent upon , diate control of swept -wing aircraft at low U/G positron --4-14-65Max speeds owing to a tendency for the airflow 10'--108"min to break away or " spill " in the region of Side and front elevationsand the wing tips, thus causing loss of stability planof the Short S.B.I5 and a tendency for the controls to appear not to respond atcriticalspeeds such as taking off or landing. 50°0Contiguration 35'-227" Theundercarriageisa The resultsof theflyinginvestigations 69060 - - 36-6-02` non -retractablemain-and carried out by the S.B./5 will be made avail- " 25-11-72" nose -wheel unit. The atti- able to the whole of the aircraft industry tudeoftheundercarriage for the benefit of British aviation. can be changed to enable each configuration to be tested at various C.G. positions. Adjustable Sweep -back The S.B./5 was designed so that varying Single Jet Engine degrees of sweep -back can be applied to the The S.B./5 is powered by a single Rolls- wings. The tail plane can also be positioned Royce Derwent jet engine whichisposi- either at the extreme top of the fin or below tioned wellaft of the pilot.The pilot's the rear part of the fuselage and its angle cockpit incorporates an ejector seat. of incidence isvariable. A programme of test flying to investigate The aircraft is fitted with anti -spin and the low -speed handling characteristics of all 5o deg. High tail unit. braking parachutes. the combinations available is to be carried 6o deg. Low tail unit. Pilot in all the test flying has been Tom out. 6o deg. High tail unit. Brooke -Smith,chieftestpilottoShort The varying degrees of wing sweep -back Brothers & Harland Ltd., of Belfast, manu- angle are achieved by fitting alternative com- 69 deg. High tail unit. facturers and designers of the S.B./5.So ponentsandfourconfigurationscanbe The angle of incidence of the tail planefar all flying has been carried out with a tested.These are : can be varied in flight and set to any desiredsweep -back of So deg.

www.americanradiohistory.com May, 1953 NEWNES PRACTICAL MECHANICS 339

111110111111111111111111111111111111111111111111.111 All Items Carriage Paid. WILCO ELECTRONICS MAINS OPERATED BELL -At last a The following are just a few items in our eskill stocks. Send 6d. in stamps for compre- doorbellwithoutBatteriesor atyour hensive list giving full details of Poten- Transformers.Operates direct from tiometers, Condensers, Resistors, Tele- MainsSupply. 3in. Magnetotype phone Key Switches,Rectifiers,etc. Bell by famous manufacturer completely selfcontained. Equallysuitablefor PHOTOGRAPHIC burglar alarms, etc. 200-250 A.C. ENLARGER TIMER Supply only.Unrepeatable at 6/6. HIGH PRESSURE REDUCING finger S * A first-classclockworktimer, constructed from an ex -Govt. VALVE. -Complete with0-3,000lbs. unit giving to16 -second ex- per sq.inch pressure gauge.Suitable posures with each winding. for Compressors, Cylinders of Gas, etc. CompletewithFootSwitch, Brand new, 8/6. Calibrated Dial, Focusing Switch. TOGGLE SWITCH. Single -hole panel Readyforconnectiontothe mounting, 250 v.2 amp. Single -pole mains, at the very low price of change -overoron/off. BrandNew, 50/-, plus 2/6 post and packing. 6 for 5/-. PORTABLE P.A. SPEAKER CASE DIMMER SWITCH. 96 ohms resistance. for 12in. Speaker.-Rexine covered, 191n. On/off position.6 for 5/-. x 171n. x 13in. ;removable back, carrying EX-R.A.F. handle, keys, provision for cable, metal - protected corners. Brand NEW. Special SIGNALLING value, 70/-, carriage and packing 10/, LAMP. -Trigger POWER AMPLIFIERS. -50 watt " Tan- action control. Al- noy " rack mounting, less valves, only ignment Sights as 58/10/- to clear. Carriage 7/8.Voltage illustration. Com- Amplifiers,28. The transformers and chokes are guaranteed O.K., but some small plete with 6ft. components may require replacing, and Cable and 2 pin wiring renewed ;4 amplifiers on one P.O. plug. Easilycon- Rack for £25. Carriage £2. verted to Car Spot AMPLIFIERS. -l5 watts, Marconi Type 6, Lamp.Price excluding Bulb 10/6. using 2-PX25, MHL4, rack mounting, com- plete with power pack, 200-250 volts 50 BRAIDED RUBBER TUBING. 3/I6in. cycles. meter, etc., less Valves, £6. Carriage bore x iin. o.d., suitable for gas, air lines, 7,6. A few incomplete but with trans- etc.Limited quantity, 10ft. lengths, 4/, formers, 50/, to clear. CONDENSER LENSES. Plano Convey ACCUMULATOR optically ground and polished.Post, 1/-, CUT OUT. 24v. 1(1n. Diem. 21in. Focus ... 7/8 each 60 amp. Ex-R.A.F., 31n. 10/- each 4in. 28in. 15/- each originally cost 4in. , 101n. mtd. irs. 32/8 pair over E6 each,. Sin. 9in. 30/- each suitable for battery 6in. 10in. 38/8 each LAMP HOUSES withpair of tin. conden- charging, e t c . ser lenses, nd focusing mount, suitable for Limited quantity flood or spetlight, es. at 15/- each. CINF3PROJECTORS 16 mm.-" Ensign " silent, complete with Dallmeyer 21n. Super- EX-R.A.F. GLIDE PATH RADIOS. lite lens, transformer and carrying case, R.I 124 £271101-. comprises 6 valves-3/9D2's GB MODEL 1.516. -Sound, complete with (VR.I06), 15D2 (VR107), 8D2 (VR108), valves. lamps, lens, speaker, resistance, £55. 4D1 (VR09), N.F. 7 m/cs, 6 switched 27B.T.H. MODEL S.R.B.ound,S complete, frequencies.30.5-40 m/cs plus a host of 5. valve -holders, screening cams, 2 trans- METRO-VICK AUTO TRANSFORMERS. formers, 33 fixed condensers, 30 trimmer --230/110v., 500watt,totallyenclosed, £4/10/-. condensers, 35 resistors, 6 coils, 5 wafer PHOTOFLOOD LAMPS, " Eke° "1,000 rotary switch,potentiometers, etc., watt. I0/- each. Post 1/- unrepeatableat 30/-, carriage paid, LENSES.-Aldis anastigm. at 1/2. Llin. focus new and boxed. (no iris), 50/- each.- DIM-BRIGIIIT FOOT SWITCH for con- ALTIMETER. 0-3,500ft.Aneroid instru- trolling Photoflood lamps for 230v. 5 amps, ment suitable for conversion to baro- 32/6 each.Post 1/-. meters. 8/6. PROJECTION LAMPS. -115v. 750 w. Prefocus. Brand New, 25/-. BROMIDE PAPER, Slim it 5lln., glossy, soft, 7/8 per gross packet. RESISTANCE MATS. -Make ideal heating mats for Aquariums, Photographic solu- tions.Print dryers, etc.Mains voltage, 150 or 620 watts. Black heat, size 10in. x 61n., 2/8.Post free. HAND GENERATOR or Battery Charger. -6 volts .D.C. at 4 amps. contained in a strong metal case irith;automatic cut-out, very useful where no mains are available, could be converted to a wind charger. Only 30/-.Carriage 51-. BALL BEARINGS. -No. EE2.lin. x lin., 31-, post free. THRUST RACES. -13/161n.x 116, AIR POSITION INDICATOR. Con- post free. taining a wealth of gears,drives and MTCROAMMETERS.-F.S.D.50.Flush type 211n. dial scaled 0/100, contained in test shafts, 3 infinitely variable gears, lamp - set No. 28, 70/-. Complete. Post 2/-. holders, repeater motors. Veeder VOLTMETERS. -0-300 A.C. Moving Iron counters, has been used by many Silo. Flush or Surface Type, 25/-;0-20, Universities as a basis of a calculating tin. Flush Moving Coil, 7/8 ;0-40, tin. Flush machine.(As illustrated.)E2/7/6. M.C.. 1043 ;post 1/-. MOVING COIL METER with 1 M/A movement, 211n. flush, rectifier type, scaled 0/100 volts A.C.Resistance 100 k. ohms. A very useful basic meter, 30/-, post free. PORTABLE TEST METER. -Just the lob for the home constructor, in neat case, 6in. x Sin. x 4in., reading 1.5, 3, 150 volts, 6 and 60 mla. D.C., 5 k. and 25 k. ohms, 37/6. Post 1/6. HEADLAMP completewithBattery Case. Fits on forehead. Leaves both hands You get immense satisfaction from X-acto, accurate free, 7,6.Post V-. SELF -PRIMING PUMP. Self-contained VEEDER, COUNTER 0-9999, lin. x lin. x Sin. Very useful, 10/-.Post 8d. motor 12 v. D.C., immersed type pump. cutting is so easy. You select one of the interchange- AERIAL RODS.-12in. long, }In. diameter. Flange mounting suitable for bilge pump, able X-acto blades to suit the work in hand; quickly Any number of sections can be fitted to- caravans, etc. (as illustrated), 30/- each. gether. PA dozen, 61- for 3 dozen, 11/- half ANTI -VIBRATION MOUNTINGS. 3 lock it to the appropriate handle and you have a firm, gross, 20'- gross, £8 per 1,000. SLOW MOTION DIALS. -61n.Scaled complete sets of 4,suitable for radio rigid knife with the sharpest blade you can buy. 0-100, reduction 200 to 1 or direct, ideal for chassis, compressors,etc.,8/- per doz. There is an X-acto blade for every cutting job. wavemeters, signal generators, etc. Our EAR PIECES. Single head set type.Low price, while they last, 513.Post 1/-. See the full series at your X-acto Stockists (who will FLASHING SWITCH UNIT with 6 impedance, suitable for telephone sets, contacts. Full rotation 60 seconds, operated etc., 2/3 each. also show you the range of X-acto knives and tool kits) by a Sangamo Synchronous Motor. 230 volts A.C. 2 watts.In metal case, 3in. x TERMS -CASH WITH ORDER. or write for illustrated folder. 2iin. x 21M., 15/-.Post V-. INTERESTED IN FISHING? -Then send NO C.O.D. Blades from 2/6 for five. Knives from 3/6 each. for one of our tapered whip aerials and make yourself a fine rod worth pounds. Tool kits from 23/- to 84/-* Consists of three tubular steel, seamless copper plated sections,4ft.long, which TRIX Ltd., Dept. A, rr Old Burlington Street, London, W.i screw into each other and are well finished, SHERMAN'S 7/6. Carriage G.B., 2/-.Eire, 8/8. CUTTER HEADS.-" Recording"high SUPPLY COMPANY P.M. impedance. A bargain at 55/-.Post 1/-. STUART PUMPS. -230 volt A.C. motor, 126, KENSAL ROAD, LONDON W-10 will lift 400 gals. per hour 15ft.. 111/15/ - larger size, -Ih.P., 222/10/-. Carriage 7/13. 204, LOWER ADDISCOMBE ROAD, 11111111.1111.11.1111111MIINNIIM Gag CROYDON

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340 NEWNES PRACTICAL MECHANICS May, 1953 GALPINS Telephone: MUSEUM 9594 ELECTRICAL STORES 408 HIGH ST.,LEWISHAM,S.E.13 H. FRANKS Tel.:Lee Green 0309. Nr. Lewisham Hospital 58-60, New Oxford St., London, W.C.I TERMS CASH WITH ORDER. NO C.O.D. One minute from Tottenham Court Rd. Station All goods sent on 7 days' approval against cash. 12/24 VOLTS HOOVER BLOWER MOTORS, Ref. 10KB/115, as recom- EARLY CLOSING DAY THURSDAY mended for car heaters in the March issue.Price 27/6 each. EX -NAVAL ROTARY CONVERTERS, COMMANDO LIGHTWEIGHT 110 volts D.C. input, output 230 volts A.C. PERISCOPES. Size 10in. x 4in. x lin. 50 cycles, 1 phase, 250 watts capable of 50% Ideal for sporting events, etc.. 10.' - overload, weight 100lb..price E10/101. each. each, carriage forward. TUFNOL PULLEYS. Fitted ball races, external diam. 211n., internal diam. ROTARY CONVERTERS, 24-28volts easy 3 '16in., 219 each, 301- per doz. D.C. input1,200 volts 70 ni/amps, D.C. DITTO.41in. external, fin. internal, output, I0/- each, P.F. 0 depentlakilA 5/- each, 55/- per doz.2,000 of both MAINS TRANSFORMERS (NEW), you II haildbfig typesavailable. always DRIVING GOGGLESby Zeiss. input 200/250 volts in steps. of 10 volts, out- high r?Pe an Goertz, etc., supplied with spare set of put 350/0/350 volts 300 m/amps, 6.3 volts grade bog qualities clear lenses. Set of anti -dazzle lenses. 8 amps twice, 4 volts 4 amps, 5 volts 4 amps, 4 precision in in maker's cartons. 11/- per set. 70/- each, carriage 3/6 ;ditto, 450/0/450 llaldens AIR TEMPERATURE GAUGES, volts 250 m/amps, 6.3 volts 8 amps twice, 4 instruments Ref. No. 6A/510.fitted Mercury in volts 4 amps, S volts 4 amps, 70/- each, range Steel, Capillary Tube, Transmitting drawing set type. Reading --30050+ Centigrade. carriage3/6; another,input asabove, of Suitable for greenhouses. etc.Price output 500/0/500 volts 250 m/amps, 6.3 volts squares scales, 18/6 each. 8 amps twice, 6.3 volts 4 amps, 4 volts 4 office slide DYNAMOTORS. Ideal for car radio, 12v.d.c., amps, 5 volts 4 amps, 75/-, carriage 3/6. accessories and rules, Input 1.2 amps, output Another, wound to (electronic) specifica- general 125v. d.c. 40 ma. drawing " KLAXON." 24 Volts d.c.shunt tions, 350/0/350 volts 250 miamps, 4 volts are wound 1,20th h.p. motors, 2,500 r.p.m. 8 amps, 4 volts 4 amps, 6.3 volts 8 amps, available continuous rating, 401- each. every 0/2/6.3 volts 2 amps, 70/- each, carriage paid ; at WESTLNGHOUSE RECTIFIER another, input as above, output 500/350!0/ branch SITS. Style 238 G.P.O. Input 200115.0 of volts a.c., 50 cycles, output ro volts 350/500 volts 250 m/amps. 6.3 volts 6 amps, d.c.,14 amps.. 70 -.Carriage 10,'-. 0/2/6.3 volts 2 amps, 0/4/5 volts 4 amps MINATURE IMPULSE MOTORS twice, 75/- each, carr. 3/6. made by " Gents " size 3 x 2 x suitable for operating models, MAINS TRANSFORMERS(NEW), switches.etc.,operatesoff4/6v. suitable for spot welding, input 200/250 a.c.id.c. and is very powerful for its volts, in steps of 10 volts, output suitably size.Price 8,6 each, post paid. tapped for a combination of either 2/4/6/8/10 SYNCHRONOUS CI.00K UNITS. or 12 volts 50/70 amps, 95/- each, carriage 7/6. Self-starting 200-250 v. a.c. 50 cycle. fitted Sangamo motors consumption MAINS TRANSFORMERS (NEW), 24 watts, size 21In. diam.. 21n. deep, 200, 250 volts input, in steps of 10 volts, geared 1 rev. 60 mins. friction reset. output/0, 6,12, 24 volts 6 amps, 42/6 each, Ideal movements for electric clocks. post 1/6. Another as above but 10-12 amps, With gear train and Sin, hands.Price 22'6 each, post paid. 55/- each, post 1/6; another, as above but SANGAMO MODEL S7 SYNCHRON- 25/30 amps, 75/- each, carriage 3/6 ; another, OUS MOTORS. 200/250 v.a.c. 50 input as above, output 0/18/30/36 volts 6 cycles, final speed 1 r.p.m., 2716 each. amps, 47/6 each, post 1/6. SANGAMO MOTOR UNITS, MODEL 7, final speed 1 rev. 24 hrs. 200,250 v. MAINS TRANSFORMERS(NEW), a.c. 50 cycles, 27l8 each. input 200/250 volts in steps of 10 volts, out- SANGAMO MOTOR UNITS, MODEL put 350/0/350 volts 180 m/amps, 4 volts 4 7, final speed 1 rev. per 7 days, 21XIM0 amps, 5 volts 3 amps, 6.3 volts 4 amps, 45/ - v. a.c. 50 cycles, 30'- each. Ex _Air Min. GEAR PUMPS. TyPe each, post1/6 : another 350/0/350 volts RFP/1, made by Rolls-Royce, size 180 m/amps, 6.3 volts 8 amps, 0/4/5 volts approx. 6 x 51 x 5in.Price 30:- each, 4amps,45/-each,post1/6 ; another post paid. 500/0/500 volts 150 amps, 4 volts 4 amps HOUR METERS, 200-250 v.a.c.50 C.T., 6.3 volts 4 amps, CT., 5 volts 3 amps, cycles, 1/10th to 10,000 hrs. recording; 47/6 each,post ; ideal for life testing. process timing. 1/6 another 425/0/425 etc., 42/6 each. volts 160 m/amps, 6.3 volts 4 amps, C.T. SLIDING RESISTANCES. Enclosed twice 5 volts 3 amps, 47/6 each, post 1/6. MAKE IT YOURSELF WITH OUR type 20 OHMS 2.3 amp.Price 22/6 MAINS TRANSFORMERS (bywell- each. VARIABLE RHEOSTATS with screw known makers).Input 100 and 230 volts, thread control, 71 OHMS 4 amp., all output 6 volts 1,3 amps twice, price 7/6 each, READY TO ASSEMBLE KITS new, unused.Price 2211, post paid. post 1/-;another 200/250 input, output 25 VARIABLE RHEOSTATS, fitted ver- volts 4 amps C.T., 25/- each, carriage 1/6. nier control, 50 OHMS, I amp., all Tea Trolleys, TV Tables, Book Cases, Bedside Cabinets, new unused.Price 15/- each, post MAINS TRANSFORMERS, 230volts paid. input,150/0/150volts200 m/amps,6.3 Needlework Boxes, Coffee Tables, Foot Stools, Children's ROTARY RHEOSTATS. If OHMS volts 8 amps, 5 volts 2 amps output, 23/ - 5'6 amps. Price 12'- each, post paid. each. Chairs,Smokers'Stands,StandardLamps,Table 500 - OHM ELECTRO - MAGNET COILS. 51 per doz. AUTO WOUND VOLTAGE Lamps, Chandeliers, Wall Lights, Candlesticks, 60 - OHM ELECTRO - MAGNET CHANGER TRANSFORMERS, tapped COILS, 10,000 available of both types, 0/110/200/230 volts 350 watts, 55/- each, Marquetry Veneers. 5,6 per doz. post1/6; as above, but 500 watts, 70/ - SLIDLNG RESISTANCES. 3.4 OHMS each, carriage 3/6 ;as above, 200 watts, Send 6d. and self-addressed envelope forIllustrated 12 amps. Price 22/8 each, post paid. SYNCHRONOUS MOTORS. 200/250v. 40/. each, post 1/6. Booklet. a.c. 50 eyes. with gear -trains.Final EX-U.S.A. W.D. ROTARY TRANS- speed 1 rev,perhour. Ex -Time FORMERS, 12 volts D.C., input 500 volts, Operated Units by well-known 50 m/amps, 275 volts makers, size 31 x x 3In. Price 21/6. 100 m/amps D.C. B. KOSKIE (Dept. A) post paid. output. Complete with smoothing switches, DITTO 2 revs. per hour. Size 31 x 3 x 31. fuses, etc., as new, 17/6 each, carriage 2/6, 72-76, LEATHER LANE,HOLBORN, E.C.I Price 16/6. post paid. can be run on 6 volts, giving half the stated 12 volt KLAXON HORNS, all new, output. Open 8.30-5.30.Closed I o'clock Saturday.Phone: Holborn 4777 16,6 each. HAND GENERATOR POWER MAINS TRANSFORMERS, input180/ UNITS Type No 7 ZA 17571. giVing an 250 volts, output 435/0/435 volts 250 miamps, output of 6 volts D.C. at 31/4 amps., 6.3 volts 10 amps, 6.3 volts 8 amps, 6.3 volts for charging. These are unused and 8 amps, 5 volts 6 amps, 65/- each ;another PARKER'S SHEET METALFOLDING MACHINE housed In metal cabinet 17 x 10 x 7in., input as above. Output 4,000 volts 21 Heavy ViceModel. 47/6. miamps, 4 voltsI amp, 2 volts 2 amps, 45/ - Capacity 18 gauge LONDEX RELAYS, Type 220, Ref. No M.S. x 2ft. wide. - 10F/494. two heavy break contacts., each. Loose Attachments, if 24 volts, fitted in metal cases, 41n. x SMOOTHING CHOKES, 4henries, required,forRadio On. x 21in., 816 each. Chassis, Tray or Box 6 -VOLT LONDEX RELAYS, with 2 250 m/amps, D.C. resistance 120 ohms, 12/6 making. break contacts, fitted 4 -way Jones each. Weight 22 lbs.Price socket, 3/- each. 40i- per doz. CONDENSERS, 0.1 mid.,6,000volt 42/3. Attachments 1/6 SOLENOIDS, Heavy Duty. 12;29 volts, working, 6/6 each. per ft.Carriage 41, d.c.. 10/6 each. With Attachments 5/8. G.E.C. DOUBLE POLE CHANGE- LARGE STUD TYPE DIMMER RESIS- ALSO OVER RELAYS, Platinum contacts, TANCES, 10 ohms, 9/18 amps, 32 studs, Coil resistance 2,500 ohms, 13'- each. 35/. each. PARKER'S FOUR IN 24 -VOLT MAGNOVOX HEAVY ONE REVOLVING DUTY SOLENOIDS, 19'- each. 3 KILOWATTS DOUBLE -WOUND DRILL VICE RECTIFIER UNITS,input200/250 VOLTAGE CHANGER TRANSFOR- Comprising : volts, a.c.. 50 cycles, output 24 volts MERS, 110/230 volts or vice -versa, as new, Upright Vee. d.c., 3i amp., £4 each. weight approx. 100lbs..f12/10/-each, Inclinable Vee. STAINLESS STEEL HELIOGRAPH carriage forward. Right Angle. MIRRORS, 4 x 41n., 3/-. FlatSide. Admits CLOCKWORK MOVEMENTS fitted RESISTANCE BOXES (sub standard), stock of Sin. dia. " VENNER "Escapement, runs 10 200 ohms, in steps (variable) by well-known Weight 13 lbs. hours one full wind, final speed 1 rev. makers, 37/6 each. Overalllength 13in. 75 sees.Price 9'- each, post paid. Price 42/6. " STANCOIL" U.S.A. 2.5 K.V.A. 50160 ELECTRIC LIGHT CHECK METERS, Carriage 2/6. cycle auto -transformers. Input; 1151 useful for subletting, garages, etc.,all for Send for details. 250 v. Output, 110v. Completely 200/250 volts A.C. mains, S amp load, 19/ - WHEATCROFT WORKS, WELLINGTON shrouded.£11 each. each ; 10 amps, 22/6 ;20 amps, 27/- ;25 STREET, BATLEY, YORKS. amps, 32/6 ;40 amps, 38/6 ;50 amps, 46/6 ; A. B. PARKER FULL MAILING LIST PRICE 6D. and. KO amps, 57/6 each, all carriage paid. Telephone BATLEY 426.

www.americanradiohistory.com May, 1953 NEWNES PRACTICAL MECHANICS 341 series of events stretching away from our " present "-in both directions. We are taught that space is not infinit0 but curves back upon itself to form a bound LETTERS less but finite whole in much the same way that the surface of the earth-in two dimen- sions-is also boundless butfinite.Now, " space " and " time " are in modern teaching closely inter -related and ittherefore seems r° THEEDITORto me unlikely that a finite space can exist The Editor does not necessarily agree in infinite time. Relativity teaches us that for eachindividual" observer "timehasa with the views of his correspondents. different meaning and a " time " in which no space and hence no observers exist can Melting Milk Bottle Tops I might mention my own unit had a two-have no meaning at all! I suggest, therefore, SIR,-With referencetothequerybyyear test before the article was published,the probability that, like space, time is also Mr. H. G. Williams, of Twickenhamand is still in good order. finite and curved back on itself so that, in it, (March issue), the idea of melting down milk In conclusion I would like to thank Mronly a finite number of events take place. To bottle tops in sufficient quantities to makeSewell forhisappreciativeletter.-A.F.round off such a theory we may speculate castings is almost a practical impossibility,PARKER (Swanage, Dorset). that the total time length possible in our if, as he says, his only source of heat is a particular cosmos is equivalent to the time it laboratory Bunsen burner. Toning Wallpaper would take a beam of light to travel round In our school workshops we have success- SIR,-With regard to the above query offinite space and arrive back atitsstarting fully melted large quantities of tops in a C. S. Brown in the February issue ofpoint(thoughtheidea of an expanding carborundum crucibleon theforgefire,PRACTICAL MECHANICS, I would say that ituniverse and hence an expanding time raises using coke as fuel and a variable speed fanwould be impossible to evenly stain or tonesome difficulty). blower for the forced draught. a grained imitation wood wallpaper without Summarising the foregoing we arrive at a As pointed out in your reply, oxidationobliteratingtheprinted patternunlessitcosmos in which both " space " and " time " and fusing must be overcome, and in orderwas sized first to prevent the stain penetratingare finite and in which, therefore, only a to combat these troubles the tops must bethe paper.This is best done after the paperfinite number of " eventsoccur and occur bulked together in some way. For thisis hung. simultaneously. Through it each " observer's " purpose we use a vice as a press, and an old A practical method is as follows : Paste theconsciousnesstravelsobservingonlythat metal bush about zin. bore as a die. paper rather liberally with good strong pastecross-section of these events which corre- By this means we have, so far, recoveredand allow to soak for some minutes.Severalspondstohisindividual" present."It about 281b. of pure aluminium, which welengths of paper can be pasted at one time,is to be noted that an " observermay equally have cast into ingots of aboutrib,each.folded to delay drying, and hung in sequence.well be you or I, a prehistoric man existing Allowing for loss due to unavoidable oxida-When dry, the wallpaper is sized by applying50,000yearsagoorasuper -intellectual tion, our recovery is about 65 per cent., anda coat of hot jelly -size, using a clean dis-existing 5o,000 years in the future (as we we reckon that about 2,000 tops are requiredtemper brush, and brushing on lightly toimagine it).In this cosmos cccasional cases to produce Ilb. of pure metal. avoid frothing. Re -heat the size as the workof precognition occurand are due toa Whatever form of heating is used, itis proceeds, and make sure that the whole oftemporary shiftof the " observer's " con- important to note that melting should bethe surface is covered. When dry, a secondsciousness from hisindividual" present " fairly rapid to prevent gasification, and thecoat of size is applied. When bone dry, theto some other cross-section of the events. shiftbeingcaused crucible should be covered during melting.wallpaper may be stainedtothedesiredThe eitherby some abnormal circumstanceortoaloosening Pouringmustalsobedonequicklyasdepthwith a " scramble "stainsuchas aluminium freezes quickly, especially whenMander's " Matsine," thinning this out toof the tie binding his consciousness to his casting thin sections. The life of the crucibledirections and applying sparingly and evenly.own " present " during sleep. will be prolonged if it is internally paintedAs an alternative, a stain could be mixed up What happens when the" observer's " with a solution of water -glass before use,using " burnt umber ground in oil," mixedconsciousnesshastravelledfullcircleis and cleaned out after each melt. quite thin with equal parts of linseed oil anddifficult to conceive though no more difficult If your correspondent requires any furtherturpentine, and adding a small quantity ofthan trying to conceiveinfinity. The views details I will be pleased to help him,if possible.paint dryer.If this is thought too warm inof yourself and of other readers of your paper -H. E. WHITE, A.M.S.E. (Derby). tone, a little green could be added.If jelly -on this and the foregoing ideas in general size is unobtainable, the packeted powderedmightbeinteresting. --T.H. MORRIS SIR,-We,theundersigned,readwithsize can be made up to the directions and(Farnborough). interest the letter regardirig the meltingallowed to cool and " jell "totestthe of milk bottle tops in the March issue ofstrength.It should set like a weak table -Einstein's Theory PRACTICAL MECHANICS. jelly. SIR,-I thank Mr. P. H. Jackson (Buxton) AtourmetalworkcentreatDarnall, The surface can afterwards be coated with forhisreply to my letter (PRACTICAL Sheffield, we melt them with a blowpipecopal varnish if a glossy finish is desired, andMECHANICS, December issue), but am still and then add a little copper. From thisit will then give many years of service.-unable to appreciate that there can be any alloy we make castingsforsmalldieselH. POSTLETHWAITE (Easton Grey, Malmes-difference whatever in the time a 'plane would engines,ash -trays,etc.-F. PRINCE, D.bury). take for an out and back journey across PALMER (Sheffield). windcomparedwiththesamelength out and backjourneyparallelwiththe Electric Chime Timing Unit " The Mystery of Time " wind. Ifeelthereissomething wrong SIR,-In the March issue of PRACTICAL SIR-Theopening sentence ofthatwith his premises and/or calculations.If, MECHANICS thereappearedaletter portion of your editorial dealing with thefor instance, one works out his figures for, from Mr.Jas.L.Sewell concerning myabove subject implies, Ibelieve, that timesay, three examples where the wind speed electric Chime Timing Unit published inextendsinfinitelyinto thepast and willin relation to 'plane speed isprogressively the March issue of 195o under the nom -de -extend infinitely into the future.I suggest togreater, the results show increasing disparities plume " Handyman.' you, however, that, in the light of presentin times, and if a wind speed of 75 m.p.h. I have since made an improvement to theknowledge, this is by no means certain. and a 'plane speed of too m.p.h. are used the unit which may interest Mr. Sewell and Dunne, in his" Experiment in Time "disparity between the times is so great as to others. (which, by the way, was not a " novel"),be very improbable. Inthepublishedcircuitthe time lagconceives that time does not " flow " nor do I think the true conditions are that in the between the first two notes depends on thefresh events keep on happening in it but thatcross -wind flight the 'plane, in order to keep time the front door push is kept pressedall events, both (tous) past and future,on its ground course, must trim its centre only (this does not apply to the trademen'shappen together simultaneously and that itline towards the wind at an angle to the door push, which only sounds the last two isour consciousnessthattravels throughground course equal to the proportions of notes). theseeventsobserving across-sectionofwind speed to 'plane speed.Thus, if the By connecting another condenser of similarthem only, corresponding to our " present,"'plane speed is too mp.h. in still air and the value to the existingones across the coilas it passes.This theory appeals to me aswind speed is 25 m.p.h. the 'plane will be connections of relay No. I we have a timeproviding the only adequate explanation forturned at an angle which results in the 'plane lag also between notes one and two. theundoubtedoccasionaloccurrenceoffacing the equivalent of a direct head wind of Should the push be rapidly pushed andcases of precognition of " future " events.one-fourth of the wind speed of 25 m.p.h., released several times the first two notesBut Dunne, who I think wrote his book beforeviz., 6f m.p.h. The 'plane's net speed along will not now be kept repeating, to be sedately'the implications of the theory of relativitythe ground linewill thus be 93f m.p.h. followed by the third and fourth. ' were widely known, still conceived an infinitewhich, if the distance out and back is 200

www.americanradiohistory.com 342 NEWNES PRACTICAL MECHANICS May, 1953 miles, gives a time of 2 2/15111 hours-pre-for the outward journey and not the maximum cisely that occupied by the 'plane out and backofthe" all -burnt "state.Themotor parallel with the wind. certainly would be cut-with at least so per So far asI can see, any theory whichcent, of the fuel unburnt. results in different times for the two journeys After all, one may wish to return.Oh yes, would be just as impossible in practice aswe should have forward motors capable ofInternational Radio Controlled Models is .perpetual motion. supplying thrust for speed reduction and Society As regards my possibly unfortunate choicemanoeuvring. of a book on the subject, I have since read It would indeed be tragic that, having THE International Radio Controlled another book by one of the best-knownexplored a new world, you were prevented ModelsSocietyannouncesthatits physicists. His way of showing that the outfrom returning home through lack of fuel.AnnualInternationalContestsfor Radio and back cross -wind journey would take aNot only would your strange and wonderfulControlled.Models will be held at Southend- shorter time to accomplish than a similarodyssey be lost to mankind for ever, but youron-Sea, Essex, England, on July 25th and journey parallel to the wind is by assumingextinction would be imminent.-WailAm26th, 7953. the cross -wind journey to have been done inELLWOOD (Hatfield). A contest for radio -controlled model boats still air-a second example of what appears will be held on Saturday, July 25th, and to be a wrong appreciation of the conditions contests for radio -controlled model aircraft Alarm ClockSwitching Device on Sunday, July 26th.The aircraft sections affecting the Michelson-Morley experiment. SIR,-The following drawing is of a simple -C. W. CARR (Eastbourne). device to make an alarm clock operateof these contests, comprising a contest for power -drivenaircraftanda contestfor a switch.Itis,to the .best of my belief, Interplanetary Space Travel original. gliders, are held in accordance with the F.A.I. SIR,-In the March issue, Mr. P. Mansfield The idea is to enable a domestic clock toRegulations for International Contests.It is (InterplanetarySpaceTravel)statesbe used without any drastic modifications.hoped 'that a large number of competitors, that a rocket at the commencement of firingThe drawing is self explanatory and the ideaboth from Great Britain and from overseas, is only concerned with gravity as air resistanceand dimensions can be adapted to any clockwill take part in thesecontests. Further V' and V=O. Whilst it is true that gravitywhere the alarm key revolves when the alarmdetails and entrance forms will be available in regard to the rocket must be overcomerings. The hole receiving the falling ball issoon to anyone who may write for informa- when firing commences, it is also true thatobviously located in a suitable position but,tion.-R.ING,36, Sunny Gardens Road, air pressure affects the rocket's thrust fromif necessary, a small funnel could be added toHendon, London, N.W.4. a pressure ratio point of view. allow for slight deviations in its path. Thrust T. is equal to the product of the The end of thecentrecontact -leafisHarrow and Wembley Society of Model insulated to isolate the ball from any live Engineers mass flow of gas -d-t and the exhaust velocitymetal work. The paper clip which holds the THE locomotivesectioncommitteehas Ve, when the gas is expanded in the nozzleball is of bent wire, but can be modified to devised a series of locomotive trials, to to a pressure equal to that of the surroundingsuit any winding key.-EDWARD A. STOTTbe known as the" Arthur Pole Memorial atmosphere.This is called momentum thrust(Rochdale). Trials."A formula which will enable the and the gas is said to be correctly expanded. smallest 3jin. gauge . locomotive to compete Thus, a rocket with a chamber pressure of on equal terms with the largest Sin. gauge 3751b./sq. in. and a pressure ratio of 25: I A/arm locomotive is being worked out by the com- will have an exit pressure equal to that of the clock mittee. A shieldwill be awarded to the surrounding atmosphereatlowaltitude ; owner ofthe locomotivegiving thebest performance during each season. i.e., islb./sq. in.We then have To=--Ve. Starting on April 19th and on the third dt A/arm key If the rocket ascends, and the atmospheric Sunday of each month until September loth, pressuredecreases,say, 21b./sq.in., a series of invitation days have been arranged, the change has no effect on the gas in the when individual clubs will be invited to run nozzle, as it is supersonic.It does, however, their engines on the society's 70oft. track at introduce pressure thrust T..This can be Paper clip theBritish Railways L.M. Region sports definedasthe product of thedifference ground at Headstone Lane, whichis now betweentheexitpressurePeandthe 72°Dia.steel being overhauled in anticipation of a busy atmospheric pressure Pa, and the exit area ball season ahead.-Hon. Sec., K. D. CARTER, 21, of the nozzle in sq. ins. A. The extra thrust Stanley Road, Northwood, Middlesex. in the above case, then, is131b. multiplied by A, and may be stated as T.-A (Pe -Pa). Aylesbury and District Society of Model esk Hole receives Engineers We see,then, that thetotalthrust T fallen be/I available from a constant fuel consumption R. ALLNUTT gaveatalktothe airpressure ; thetotalthrustbeing VA/AC/LIM society on March 18th on the making oftunnels. A large number of members expressed as T=-dt+(Pe -Pa) A. turned up at Hampden Buildingsto hear It is easily seen from this that a rocket's their colleague talk on a subject on which fuel consumption would be less for take -off heiswell informed. Mr. Allnuttis by in a vacuum than for take -off in Earth's Wood beading locates profession an Admiralty civil engineer with atmosphere. clock on base Box built quite- a lot of experience of railway work. around contacts He illustrated histalk with lantern slides Another aspect ofair -resistanceisthe S.Por OP changeover obvious one of drag.The rocket cannot contacts removed obtained from the London Transport.With attainanyvelocity whatsoever unlessair from PO type relay Mr. East operating the lantern, he managed molecules are displaced by the shaped nose. \::\x.\ N.\ % to throw light on what for some members Drag due tocross-sectionalarea may be OIL was a very dark subject.-Hon. Sec., E. H. reduced, but skin drag then tends to increase. SMITH, Mulberry Tree Cottage, Devonshire As a result, any streamlined form is but a Avenue, Amersham, Bucks. compromise with air -resistance. \\ \\\\\\\\\\\\\\\\\\\k\\ It is correct that much of the heat energy Centre leaf in thegas -streamis Weight of be/I extended and converted to kinetic operatescontacts endinsulated BOOK REVIEWED energy through the nozzle.When we consider Model Steam Locomotive Designs and that in free space, where the exit pressure isSide view of the alarm clock unit, and detail Specifications.Revised by Ernest A. zero, the pressure ratio term is at maximumof the switch. Steel.Published by Cassell and Co., and the pressure ratio isinfinite.All heat Ltd., 62 pages. Price 4s. 6d. net. energy is then convertible to kinetic energy ;A Recording Weathervane THIS book, which is a revision of an earlier but this is impracticable as the nozzle would A Correction work by Henry Greenly, gives speci- need to have an infinite exit area. TN the article on the above subject in thefications and brief constructional details of The suggestion that the rocket may move .LMarch, 1953, issueaf PRACTICAL various types of model steam locomotives at a velocity far in excess of its own exhaustMECHANICS, a draughtsman's error occursfrom No. o gauge to a i5in. gauge " Pacific " velocityisquitelogical when consideringconcerning the two cog -wheels. The wheellocomotive. There arealsochapters on projection in free space.The constant thrustat the end of the vertical shaft should meshFundamentals of Design; Cylinders and Valve adding to the ever-increasing velocity of thewith the bottom of the cog -wheel on theGear ;Boiler Design and Handling Model rocket would continue so long as the fuelhorizontal shaft, and not the top of the wheel,Locomotives.The book is well illustrated held out.The maximum velocity, previouslyas shown in Fig.I of the above -mentionedwith line drawings, including 20 practical stated, would be in respect of fuel allocatedarticle. working designs.

www.americanradiohistory.com May, 1953 NEWNES PRACTICAL MECHANICS 343 bench and Cabinet models from stock. MYFORD M.L7. LATHESBench models £48.5.0.Deposit £12.2.0 and 12 monthly payments of 68/7. alternatively deposit £12.2.6 and 18 Monthly payments of 47/11. WE PAY CARRIAGE OUT. Literature gladly sent. THE BOXFORD MODEL C.SCREWCUTTING LATHES ON (lessmotor) £142. Deposit £35.10.1and12monthly CABINET STANDpayments of £9.12.7, alternatively deposit £35.10.11 and TECHNICALSERVICES 18 monthly payments of 86.13.8. Carriage extra.Literature gladly sent. REEVESCO DOUBLE ENDED SLIDING TAILSTOCK DIE - CO. HOLDER fzem.hoguiuMana npc=1.antlep.klg.or31N. :.,grly:T. shank (please SHRUBLANDWORKS BANSTEAD SURREY FOBCO STAR 0-4" CAP.DRILLING MACHINES ii;g,;, tigg Telephone: BURGH HEATH 3830 machine 835.8.8. fitted Jacobs chuck.Deposit 88.17.9 and 12 monthly payments of 50/11. PEDESTAL MODELS 2404.9.Deposit 810.2.9 and 12 monthly payments of 57/-. THESE MACHINES NOW AVAILABLE FIrr.s.D WITH No. 1 M.T. SPINDLE WITH DRIFT (leas chuck). WE PAY CARRIAGE OUT. Illustrated literature gladly sent. THERMOSTAT.LA/40 BI -Metal. Cera- ranisers,, etc.50-550 (103. F. 15.6,post 4d. bench drilling machines for belt drive 0- fin. cap. £8.12.6 mic Case tin. x tin.x fin.50-220 am F. TOGGLE SW ITCH. Single HolePanel REEVESCO NO. 2complete with chuck.Deposit £2.3.0 and 12 monthly pay- fully adjustable overthis range.1 amp., Mounting 250 volts, 2 amps. Sample9(1., ments of 1110,Carriage and packing 7/6 extra. 240 volts.3/9, post3d. Post 3d.7/8 per doz. THEROMOSTAT.5N/40.As above but SERIES PARALLEL SWITCH.1 amp.. pAae 81Ingle with magnetic snapaction, ideal for Fish 250 volts A.C.Fits into line cordbetween SELECTA 6" DOUBLE ENDED BENCH GRINDERS post 3d. appliance and supply. 7/6, post 3d. Deposit 81/- and 12 monthly payments of 2215.WE PAY CARRIAGE OUT.4iin. Tanks. 5/8 each, CORD THROUGH SWITCIIfor DOUBLE ENDED PORTABLE GRINDERS A.C. single phase £7.19.0. Deposit 40/- and 12 THERMOSTAT.CS. ConvectorLINEThermo controlofsmallportabledomestic monthly payments of 10/11.Carriage paid. stetstat for Space Heatersand Low tempera- appliances.5 amps., 250 volts A.C.3/8 ture Ovens.15 amps.,250volts A.C. each, post 3d. PROGRESS JUNIOR BENCH DRILLING MACHINES 40/80 deg. F.2.5/-,post 5d. . ASBESTOS HEATING CORD.A most for belt drive 0-lin. cap. complete with chuck £13.5.0. Deposit 66/3 and 12 monthly payments TIIERMOSTAT.MB.forcontrolof versatile heating medium.Stockedin of 1813. 0 -lie. cap. with motor mounting (less motor) complete with chuck £22. Deposit Electric ImmersionHeaters up to 3KW. 15, 25, 200 and 400 ohms per yard.Price 90/190 deg. F.15amps., 250 volts A.C. P. per yard. £5.10.0 and 12 monthly payments of 30/3. WE PAY CARRIAGE OUT. 21/1510. post 9d. P.V.C. HEATING CORD in 200ohms/yd. £1.5.17.6.DePosit 79/5 THERMOSTAT.PP. RoomThermo- only.1/- per yard. PERFECTO 5" STROKE HAND SHAPERSand 12 monthly pay- stat. 15 amps., 2.50volts A.C.5in. x llin. DRAWING AND INSTRUCTIONS ments of 21110.Machines fitted with Auto feed £17.17.6.Deposit 89/5 and 12 monthly x tin.A beautifulinstrument.Temp. for making a 60in. x 30in. ElectricBlanket. payments of 24/7 Carriage and packing 7/6 extra. ranges 30/90, 40/100,40/80, 60/100 deg. F. 1/6. Heater Cable and blueprint.20/-. as required.82/0/0,post 6d. . DRAWING AND INSTRUCTIONS BURNERD CHUCKS FOR DIRECT FITTING TO MYFORD THERMOSTAT.BW/1. 3amps., - 250 for making a 60in. x 501n. ElectricBlanket. (no backplate required) 4in.3 -jaw G.S. model 30M. £7.19.3. volt A.C. For controlof hot -plates. vul- 18. Heater Cable and blueprint.35/-. M.L7. LATHES 6 -in. 4 -jaw Ind. model 34M 26.5.0.Post paid. S.S. and S.C. centre lathes, complete with C/S. unit and motor HAIGHTONSPulley, aln. 4 -jaw Ind. chuck with screwed body (less motor) 825.17.9. FINE SILVER. CONTACT RIVETS for light arid medium duty. Deposit £6.9.9 and 12 monthly payments of 35/7.Carriage and Packing 76 extra.Illus- Head Head Shank Shank trated literature gladly sent. Ref. Diem. thickness Diem. length Type of Price ALL GOODS DESPATCHED INSURED AGAINST LOSS. AND DAMAGE IN TRANSIT. (in.) (in.) (in.) (in.) head per doz. REFERENCE TO CARRIAGE ABOVE APPLIES TO MAINLAND ONLY. Overseas carriage strictly extra. 110 .062 .020 .025 Hedlund 1/- 111 .062 .020 .040 1./- A 1/- stamp will bring you a copy of our 1953 comprehensive illustrated catalogue. with 113 .091 .030 .050 .035 ,, 1/9 details of blueprints, castings, fittings and materials for many " L.B.S.C." designed small 110 .075 .031 .048 .120 2/9 _ steam locomotives.Also listed carefully selected range of workshop equipment most of 124 .030 .050 .065 Flat 2/9 which is available on our well-known OUT OF INCOME TERMS. 199 .125 ' .062 .062 6/- .156 . .078 Radjused 8/-

211 .18 .062 .091 .235 121- 321 .235 .080 .185 .165 151- - 837A .250 .047 .094 .050 Flat 12/- A. J. REEVES & CO. 837/1 .250 .047 .094 .050 Radiused 12/ -

413, MOSELEY ROAD, BIRMINGHAM, 12 All post free: For Gross Price multiply doz. price by six. Grams:Reeyesco,Birmingham." Phone :CALthorpe 2554 ASBESTOS DISCS. 5in.diem.,tin. ADHESIVE THREAD. 3 strand. 100 thick. Ideal as Soldering Iron rests.2/- yard Tins. A very useful item.7- tin. "THE CHOICE OF EXPERIENCE" doz.. post 64 BEST BLACK RUBBER TUBING. 1/321n. Wall.Internal diameter lin., 5d. FIRECLAY TUBES (Soft). 15/64in. O.D. per foot ;3/16in., 6d. per foot ;lin.7d. a 11/641n. I.D. x 2in., 1/6 per doz., post 4d. per foot5/16in 8d. perfoot;M.,' 8d. PURE NICKEL CONTACT STRIPS, per foot. lin. x 51161n. x SCREWS. 4 B.A. x lin.C/S high temperature elements. (Machine Cut). Gd. doz., post 3d. _GA NI AG E S 1/6 per doz., post 3d, 5 B.A. x tin., C/S Steel. Gd. doz., post 3d. 6 B.A. x lie., Brass N.P. 44. per doz., BAKELITE KNOBS with Aluminium post 3d. SPECIAL OFFER OF 'BMX ' FLEXIBLE riveting shank, foruse as feet or lid 6 B.A. x 3/161n., Brass N.P., 4d. per doz., VICES SHAFT DRILLS handles, post 3d. L5.10 OFF List Price! Grommetts(or Cable Bushes).Black rubber. YOU SAVE43/- Ideal for light grinding operations Ref. No. O.D. I.G. Per doz. Per gross Pos' Record No. 84 steel Fitter's on castings, pottery, sheet metal, vice. welds and light metal. Takes plain 3030R Td i5" 2/- 14/6d. 4d. Slightly used but in _2_'' excellent condition. Made profile wheels up to3in.diam. 3032 16 7/33' 2/3d. 16/6d. 4d. ofsteel throughout and Shaft size 4ft. x 8 mm. 1 h.p. motor 3028 111-" 9/32" 2/3d. 16/6d. 4d. unbreakable in use. Hard- A.C./D.C. 6.000 r.P';£1 is9,, enedsteellawplates. 2/i o 3031 li'ff 2/0d. 14/6d. 4d. List Price £18. 9,+' Width of jaws 41in., depth 2029 TS' 7/33' 2/0d. 16/0d. 4d. 3M., opening 511n. Weight Or 3 gns. Deposit and 5019 _9', 1/11d. 15/0d. approx. 41 lbs. 10 monthly payments of 20/9 Fe' 1" 4d. s4 133 19/38" II-" I/10d. 13/6d. 4d. ListPrice£8.3.0 Carr. & pkg. 5/-Eng. or Wales. -ta" Carr. 4/9 England and Wales. 1033 r 2/3d. 16/6d. 4d.

DOUBLE -END PORCELAININTERLOCKINGINSULATINGBEADS. ANERIOD BAROMETER [41.p. Split Phase Start SPANNERS in Clip ELECTRIC MOTOR Slimly made.Drop forged from manganese silicon C [-- by steel.lin.totin.Whitworth.Tensile strength Induct ion motor 14 11.T.11.,220/230 volt single 90-108 toils per sq. in.Black finish with .16,_ Bore Diam. No. per Price per 4*' phase. 1,425 r.p.m.Rest - bright heads. - SetofSix. 6 I Size (im) ' (in.)) gross Dent mounting. New, but Post & Dig. 1.1- 1 .047 .111 100 8d. slightly stores5 .070 175 72 9d. Thisfineinstrumentisof soiled, * New and Enlarged Edition of Gamages 3 .091 .211 64 1/- handsome appearance and Carr. & pkg. 6/8 Eng. & Wales, 4 .118 .243 61 1/4 would normally cost 05/5/0. 8/9 Scotland. Tools and Motor Car Accessory List 5 .141 .300 44 2)4 An exceptionally advantageous 6 .156 .419 36 4/6 purchase enables us to oiler Free on Request. 8 .196 .453 30 6/8 at 55/- or5/- dep.Balance Post :4d. for gross lots. Orders over £1 post free. 11/- monthly. A perfect " Wed- STURDY STEEL SECTIONED. ding Present." FINE. SILVER TIPPED CONTACT B.C. lampholder.40/100 watts.Mako a SCREWS. show for the Coronation. 71 each. FOLDING BENCH 7 B.A. x lin., 4/- doz. 4 B.A. x lin., 6/- doz. CHATTERTON'S COMPOUND.4 oz. Designed to be securely fixed to wall or other 8 B.A. x On., 416 doz. 6 B.A. x lin., 513.doz. sticks.1/6 per stick, post 3d. upright structure. When closed it projects only III -METAL. 6in. x lin. x .0361n.. 1/- per UNIVERSAL MAINS MOTOR. Length 4tin. and the tool rack provides a lock -up for strip. 1 kin. x 3/161n. x .0361n., 6d. per strip. 3 1/16in. 25 Watts, 230/60 volts.A.C./D.C. tools. On release of fastener it is dropped.to work- MAGNETS.Sintered Bar magnets of Shaft diam. 5/321n. 6,000 r.p.m. (light). ing position with bench top level and rigid. Bench great power and stability for snap action Ideal for Hairdryers, Drink Mixers, etc. top surface comprises 101n. wide steel plate and thermostats, as used in tropical aquaria. 3$1-, post 6d. 2ft. 5in. wide timber.Fitted with vice.Ht. of Ain. a 3/16in.x 1/16in. 91. each. 8'- per doz. FOUR BLADE BLOWER FAN to fit back Oft. 3M.In. of bench 2ft. bin.Bench top CERAMIC ELEMENT FORMER aft. 31n, x lit. Pin. Wt. approx. TUBE. 5in.long. 7/161n. outer diam., above motor spindle.2/-, post 4d. lin. bore. 30 grooves per inch. For making ELECTRIC HAIR DRYER.Ilot and 100 lbs. A6/11/6 small Immersion heaters.2/8 each. post Cold Air, 200/50 volts. A.C./D.C. A won - Carrlage outside our van arm 9/3 England or Wales. 4d. derful gift for girls of all ages.23/8/0 or FLASHING LAMPHOLDER for win- 5/- dep., Balance 11/- monthly Guaranteed dow displays, signs etc.Inserts in any for 12 months. GANIAGES, HOLBORN, LONDON, E.C.1. HOLborn 8484

www.americanradiohistory.com 344 NEWNE$ PRACTICALMECHANICS May, 1953 Build it yourself with these CLASSIC EXAMPLES EX-GOV. BARGAINS OF TO-DAV'S OtTSTANDING HI-FI EQUIRMENT CHORE HORSE LIGHTING SETS.x2-15 v. zo a. (30o w.).Complete ready to use with control box, ammeter, etc.Fully Automatic and self-starting Everything for the Quality Specialist from 12 v. battery. Runs over 05 hrs. to the gal.Slightly used and guaranteed FOR CASH OR EASY TERMS perfect, i16.1o.o each. Two 6 v. 85 a. bats. to suit, f6.to.o.Carr. Paid. MK. 32 TELESCOPIC RIFLE SIGHTS. 34 with E. and W. adjustments, A Selection from our Stocks of TAPERECORDINGEQUIPMENT i7.1o.o each. Wearite Tape Deck - £35.0.0 MOTOR BLOWERS. 24 v. A.C./D.C. Mk. III.Used, 02/6. New boxed, Bradmatic Tape Desk £42.0.0 17/6. (See P.M. July. Hedge trimmer.) Transformer to suit, 07/6. Truvox Tape Desk £23.2.0 RADIO RECEIVERS. 6 v. 121124, complete with valves, 301- each.Huge Lane Tape Desk...... £16.16.0 Quantity of Radio Gear.See our lists. Simon 2B...... £60.0.0 DELAYED ACTION TIME SWITCHES. With 8 -day jewelled watch Scophony...... £65.0.0 movement.Adjustable from 1 hr. to 36 hrs. by a pair of cal. dials. Brand New ...... in sealed tins, 21/- each. Ferrograph ... £79.10.0 DRAWING INSTRUMENTS. Slightly soiled.Will do all that a £to set C.J.R. Portable ... .£119.10.0 will do, price 02/6 each. Quad Tape R...... £16.16.0 Bradmatic Circuits ... 5.0 Bradmatic 6 RP Heads...... £3.15,0 OPTICAL Bradmatic 5 RP Heads...... £3.5.0 ENLARGER KITS. 35 m. or 21 sq.All parts ready to assemble with optical Bradmatic 5E Erase Head £3.5.0 condensers and achromatic lens.98/-.Plans only 3/6. MICROSCOPE UNITS.14X.Use with your ordinary camera for photo- Spare Spools, 600 ft. ... 4s.6d.: 1,200 ft.::: 6.6 micrography. Makes an ant look like an elephant, 45/- each. Cost to times the Tapes, G.E.C., Scotch Boy or F.M.I...... £1.15.0 price.This unit has numerous uses.See our Booklets Nos. t and 2, 2/6 each. GRUNDIG, VORTEXION, E.M.I., WIREK, etc.MICROPHONES,etc. SMALL EPISCOPES. Make your own.Lens and Mirror with plans, E7,6. FULL RANGE OFAMPLIFIERS, including TELESCOPES, ASTRO or.TERRESTBIAL. Make your own. It's dead easy. Rogers Baby de Luxe £22.10.0 We have a wide choice of achromatic OGs and Orthoscope eyepieces at prices to Decca P.A.6 ...... £26.5.6 suit your pocket.See Booklets No. t and 2 for details, 2,6 each. Goodsell Williamson ...... £33.5.0 TELEPHOTO LENSES.Ideal for adapting to Exacta or similar camera". Also DECCA, LEAK ROG ERS, SOUND SALES,etc. All approx. F5.6. Brand New and Bloomed throughout.5M. back focus 3in., 40/-.8in. bf 4in., 45/-.loin. bf 6in., 50,'-.All in plain, screwed sleeve. SPEAKERS, including No iris. EX TUBE to fit the lens only, 7/6. Goodmans 101 8 in. £7.2.9 BOOKLET, " HOW TO USE EX -GOVT. LENSES& PRISMS," No. 1 Sr 2, Tannoy Duo Concentric 15in.... £33.10.0 price 2/6 each.

Wharfdale 10in. Golden ... £8.6.0 3D.Don't be mislead about this subject. It's neither difficult or expensive . if you go the right way about it.Get in on the ground floor. Our New Book MOTORS,PICK-UPS, including " Stereoscopic Representations of Three Dimensional Scenes,"price 7/6, tells Garrard RC75A ... £16.18.6 you all you need to know about 3D. Without Viewers or gadgets.For Cine, Decca GU4 ... £9.19.11 stills or prints.Colour or monochrome. Send for full lists.We also specialise in large -screen TV. Please send S.A.E. for complete lists. THE CLASSIC ELECTRICAL ,T.; H. W. ENGLISH, 352'364,LOWER ADDISCOMBE ROAD, CROYDON, SURREY. RAYLEIGH RD., HUTTON, BRENTWOOD, ESSEX

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www.americanradiohistory.com May, 1953 NEWNES PRACTICAL MECHANICS 345 The Worldo Model Steel Works Tableau Scale Model Ambulance Prize Sailing Ship

AT theInternationalMachineTool Exhibition at Olympia last year there Fig. 5.-Model was displayedaseriesof working yachtsandsailing models in tableau form which depicted steel ships at the Model production over the past hundred years at Engineer Exhibition. the works of Messrs. Samuel Osborne and Mr.Field'scham- Co., Ltd., of Sheffield.The models were to pionshipmodelof a scale oftin, to'ft., and the scale -model the " Cutty Sark " figures included in the tableau were made by isin: the glass case students of the Sheffield Art School. The on the extreme left. first three models showed a crucible melring

Fig. t (Left).-Modelof a 4 -ton hammer shop.Compressed air of a4 -tonhammer now supplies the power instead of a water- shop. wheel, and the heat of the furnace is con- Fig .2(Below).-trolled.In the forge, ingots are hammered Modelofa6 -ton down to billets or slabs, suitable for rolling Heroultelectricarc intobarsorsheets. A modern double - furnace. Both of theseduo rolling mill was the subject of another are part of a tableaumodel. of working models depictings t eel pro-Model Yachts duction over the past The imposing display of model yachts and hundred years. sailing boats shown in Fig. 5, and looking as though they are lined up for the start, were seen at theModel Engineer Exhibition. Presentation Ambulance The fine model ambu- lance displayed in Figs. 3 shop, apairofold-fashionedwater - and 4 was made to the driven hammers and a rolling mill, all of order of County Alder- about a hundred years ago. Model No. 4 , man Harry Lord, M.B.E., (Fig.2)represented a6 -tonHeroult J.P., and was presented electric arc furnace, as used nowadays for by him to the 'Lancashire producing large steel ingots and castings, CountyCouncil.T h e andincluded.exactreproductions of presentation was to com- melting -furnace equipment.The electric memorate theinaugura- furnace is tilted so that the melted and tionofthe Ambulance refinedmetalispouredintoaladle, Service under the raised by a crane, carried to the casting National Health Service pit and the metal poured into the moulds Act, 1945, and the model through a stopper in the bottom of the is to be used as a trophy ladle. for competition amongst Fig. t shows another realistic model, that the personnelof the service toencourage efficiency.The scaleis one -tenth full size.

Figs. 3 and 4.-Two views of the illoth full-size model of a Karrier Ambulance, presented to the Lancashire County Council by County Alderman Harry Lord.

www.americanradiohistory.com 346 NEWNES PRACTICAL MECHANICS May, 1953 separately and the complete kit, packed in a strong, partitioned, cardboard box costs I6s. 3d. The makers are Bi-metals (Britinol) Ltd.,St.Mary'sWorks,BridgeRoad, London, N.9. "Truset" RaniPrecisionBending Machine Wolf Electric Tools at BIF such titles as: Drilling an Oil Well, Refining ECONOMY intube bending, especially WOLF ELECTRIC TOOLS, LTD., areof Oil, Transportation of Oil, Drilling for where off -set bends are required, can exhibiting the complete range of theirOil in England, Chemicals from Petroleumonly be effected when the straight length electric tools at the B.I.F. and the displayand Jet Aircraft Fuels. A set of three 4oin.of tube between the bends isas short as will incorporate some interesting newcomersby 3oin. two-colour wall charts on searchingpossible.To tackle this problem Chamber- to the already extensivelistof industrialand drilling for oil and its refining are avail-lainIndustries Limited, ofStaffa Works, machines.There will be a new saw (typeable, price 4s. 6d. including P.T. and postage.Leyton, E.io, have designed and produced RS7), a new portable grinder (type GQ6) andFilms,filmstrips,episcopephotographs,the Truset Bending Machine incorporating a die grinder kit (type DGi). lanternslides,setsofsamples, molecularan improved back stop with the centre form- The RS7 saw is a smaller counterpart ofmodels and display material are available for ing block. The whole idea is based upon the the popular min. saw and incorporates afree loan on agreed dates. back stop being as narrow as possible and Johnsons Developeryet so designed as to give the necessary grip 468 and support to prevent slipping and distor- TOHNSONS OFt on to the tube during the bending opera- j HENDON, LTD.,tion. have produced a new andimproved M.Q. developer,knownas Developer 468. In powderformthis compound contains developer improver 142 and wetting agent 326.It is supplied in atinto make 200Z. forsubsequentdilu- tionItoIfor con- tact paper and I to 3 for bromide. The developer has been evolved to pro- duce an intense blue - black on all types of Wolf " Cub" equipmentbuilt up as a wood turning lathe. contactpapera n d copying papers, to new powerful motor of advanced design.Ithave great exposure latitude and complete has a 7in. blade, is extremely compact andfreedom from fog.Developer 468 isalso easy to handle and possesses abundant powerexcellentfor bromide papers and permits for high-speed cutting at full capacity.Toprolongeddevelopmentwithoutrisksof The bending machine on its light steel stand. the range of portable grinders is added thestains or veiling.Instructions are enclosed GQ6-a heavydutymodel which isand the special two-part container keeps the Precision bending to accurate dimensions powered by a new motor with exceptionallycontents in perfect condition.The 4o-80oz.is ensured by the back stop, attached to the high speed -torque characteristics, and itis size retails at 25. 9d. tube former, adjusting its grip automatically fitted with a resinoid bonded grinding wheel.Britinol Soldering Outfit in accordance with -the load applied, a feature The DG Idiegrinderkit. hasbeen which will be appreciated by engineers who produced to meet the demands of industry THE " Popular " soldering outfit consistshave suffered with tube slip.Formers are for a versatile tool at low cost to tackle the ofa"'Ilium)! "self -blowingspiritavailableforbending, cold and unloaded numerous jobs in their tool rooms and main-lamp, a telescopic soldering iron, a coil ofthrough any angle up to 18o deg., tube sizes tenance departments.The power -unitof up to a maximum of Sin. (gas tube) and this kitis the well-known Wolf high-speed dia. in copper and light gauge tube. grinder, type EVG3. 1111.1 Qualified technicians will be in attend- C; Another advantage of this machine is the ,,-4M M cunning design incorporated in the centre pin ance to provide continuous demonstrations J POPULAR and handle to ensure that the correct angle of the Wolf range of portable electric tools of lead is maintained at all times.This is including --drills from I' -in. to I tin. capacity, 7000" important, as too little will cause draw and screwdrivers, grinders, polishers, saws, too much, flatting, and isessential for the blowers, hammer kits,hisel mortisers, valve accurate bending of copper and light gauge seatgrinders,valve refacers,valveseat tubing. Of course right and left hand bends grinding kits and the popular " Mobilectric " well beyond 18o deg. can be produced in valve shop. any completed form. Apart fromthefullrangeofelectric The machine consists of two main com- solderguns and soldering irons, there will be ponents-the base and bending arm. The working displaysofthefascinating Wolf The complete " Britinol" soldering outfit. base is circular and carries lugs suitable fof, "Cub " equipment for handymen and home universal mounting on either bench, vice, or constructors.The basic power unit is a tin." Britinol "self -fluxing wire solder,atin of paste solder and a pair of extra wicks forbending stand, and around the base are holes drill, which with the various accessories can for a stop -pin, which when used in conjunc- easily be built up into a drill press, portablethe lamp.The lamp isself acting, easily polishing, grinding or sanding kit, a woodlighted with a match, and has no valves totion with an additional stop screw on the get out of order.It gives an intense heatbendingarm,allowsadjustmenttoany turning lathe or a circular saw bench. and clean blow pipe flame Sin. to 4in. long.angle for repetition work. The bending arm, Pill Literature The lamp cannot leak when folded for therotating about a centre -pin fitted to the base, pocket and has folding supports tocarryconsists of two accurately machined steel bars' THE free literature supplied by the Petrol-the soldering iron. carrying an adjustable bending pin, fitted into eum InformationBureau,29, New This iron has been specially designed forthe head block at one end, and the handle Bond Street, London, W.', includes "Notesuse on the supports of the " Britinol " self -block at the other, this design rendering the) About Oil," whichisan account of theblowing lamp and willfit into the pocketarm extremely robust. origin and early history of oil and the typeswhen closed.The paste solder comprises A light steel fabricated bending stand, illus- of strata in which it is found.Prospecting,finely powdered tin and lead, combined withtrated, can also be supplied with the machine. drilling, refining and transportation are alsoa non-acid flux of great cleaning power. The A small pipe vice can also be supplied dealt with.Additional pamphlets on thewire solder contains a core of the same non-for mounting on the stand so that the, tube 4- variousaspectsofoilproduction includeacid flux.Each of these items is availablecan be secured for further processing.

www.americanradiohistory.com May, 1933 NEWNES PRACTICAL MECHANICS 347 READERS'ZA122. AHD liY,H11'2, The pre -paid charge for small advertisements is 6d. per word, with box number 1/6 extra (mtnimum order 6/-).Advertisements, together with remittance, should be sent to the Advertisement Director, PRACTICAL MECHANICS, Tower House, Southampton Street, London, W.C.2, for insertion in the next available issue. SITUATIONS VACANT TRANSFORMERS, for trains, weld- PERSPEX," clear, coloured, sizes 80w* DIA., 24in, focus, TelesconS ing, low voltage lighting, battery cut, also Corrugated ,Plastics, objectives,achromatic, 42/- ; The engagement of Persons aifswering these chargers, etc. ; alltransformers Aluminium, Asbestos, Mouldings. high power,iin. approx. astro eye- adverttsements must be made through a Local 'fitted with protection " Henry Ltd.,Atom pieces, 35/-, Office of the Ministry of Labour or a scheduled earth Moat & Son, L. Allen, Marble Place, Employment Agency if the applicant is a man screen, " play safe."Write or phone Works,Newcastle, 1. Eastbank St.,Southport. aged 18-64 inclusive or a woman aged 18-5) your requirements toF.W. Whit- inclusive unless he or she, or the employment, worth, A.M.Brit.I.R.E., Model Dept., AIRCRAFT SURPLUS, Flexible MAKE YOUR OWN RANGEFINDER. IS excepted from the provisions of the Notifica- Express WindingCo.,333, London Drive,48in,long, brass unions Full instructions, 3/6, post free; tion, of Vacancies Order 193.). Road, Mitcham.(MIT. 2128.) each end, outer casing tin. dia., 10/6 orinstructions and material,11/-. each.Also Nuts, Bolts.,etc. S.A.E. Elgin,Dept.S., 338,LillieRoad, xyAMINE TOOL FITTERS, QYNCHRONOUS CLOCK MOTORS. forlist. Hulse & Goddard, Bux- London, S.W.6. -LiraMachinists, Turners, with well-. KJ' 230v. A.C. S/Ph 50c., 12/6 each, worth, Stockport. ,establishedfirM;Box No.101,c/o plus1/-. Postage Universal Elec- BALL -RACES, 3/16in., iin. bore, 1/6 PRACTICAL MECHANICS. trical, 217, City Road, London, E.C.1. LENS WORKERS : Supplies of each, 12/- dozen; tin. bore, 3/ - Abrasives. Lists available. each;BevelGears, 3 pairs7/6; CROWN AGENTS for the Colonies.- NUTS, BOLTS, SCREWS,Rivets, Mason & Gantlett Limited, 3, Orford Camera Controls. £2/10/-; Universal Cinema Officer required by the Washers and hundreds of other Place, Norwich. Joints,idealformodels,taketin. GovernmentofNyasalandforthe itemsformodel engineersand or 3/16in.spindles,5/-each;, 6 or Public Relations Department for one handymen;Send now for free list. REJUVENATE your Water Softener; 12 volt. amp.Rectifiers,10/6; tour of 24 to 36 months with pros- Whiston, New Mills, Stockport. New Zeolite, 2/3 lb.; 101b. post ControlBoxesformodelrailways, pect of pensionableemployment. paid.C. G. Nelson,118, Anchorway containing 2 ceramicrheostats, Commencing salary according to age, D UPLEX Decorative Transfers, Road, Coventry. switch, and 2 -pinplug and socket, war service and experience in scale, CoronationTrawlers. Trade - 10/6;IndicatorUnitswith6 -volt £677 rising. to £1,001 a year; includ- marking Transfers. List and samples, .V.LECTRIC MOTORS, B.T.H.230/ bulbs,5/-;smallElectricMotors, ing cost of living allowance ;outfit 6d. " P.M.," Axon Harrison, Jersey. 240,ih.p.,1,425 r.p.m. ;new 24 volt, 2iin, long by ltin. diameter, allowance, £30 ; free passages ; and unused; £5/5/- each.Miniature A.C./D.C., 20/-; 0-1 M.A. Meters; 20/ - liberal leave on full salary.Candi- AMAZING DEVICE,cutsperfect 12or24v.Motors-,A.C/D.C.;ideal and 25/- each;s.a.e. enquiries. dates,between 24 and 35 years- of discs, wheels, etc.to 12in. dia- for models,etc. ;size attn,long. x Bateman, 110, Peartree Road, age and UNMARRIED must be able meter, with any circular saw, 10/6 ; 2in. x New Twin 40w. Ballast Derby.(Phone: 44528.) to manage a mobile cinema, maintain p.pd. ;sample gin. mahogany disc, Units, no starter required ;all vol- andrepairfilmprojectors,radio photo, details, 1/6.Below:- tages, 200/250 supplied ; 25/- ; 1DERSPEX for all purposes, clear or sets,taperecordersand ' domestic requires holders and lamps only to coloured, dials, discs, engraving. -mechanicalappliances.They must H OW TO RE -MIND and Service Denny,15, Netherwood Road, W.14. alsobeabletomaintainafilm Electric Motors,'Generators. complete ;Single 40w.Units,S/H, library. Apply at once byletter, Complete Practical Book only3/- ; 17/6 ;Holders, 2/6 each ;Starters, (SHE: 1426, 5152.) p.pd.Below:- 2/6 each ;24v. Vent Axia Fans, new, statingage,fullnames- inblock 45/- each-; CromptonParkinson "Sparking PlugsoffU.S. letters, and full particulars of quali- OW TO MAKEIT -BOOKS : Chlorinator Pumps, 220v., 230v., A.C.. "ACradio equipment, 3/9 each; fications- and experience, and men- Whittling in Wood ;Inlay Pic- h.p. ;little used ;£10. Harringay Paxolin Strip,8iin. x kin.- x 3/161n, tioningthispapertotheCrown tures,' Marquetry;American- Action Photographic and Electrical' Supplies, 20.each,2/-doz.;packingfree; Agents for the Colonies,' 4, Millbank, Toys ;. 21 Lovely Lamps ;each p pd. postage at P.O. rates. Send s.a.e. for London,S.W.1;quotingonletter Ltd., 423, Green Lanes, N.4. (Tel.; 6 -page list of bargains.The Radio M.33495.E. The Crown Agents can- MOU 2054.) Services, Lr. Bullingham, Hereford. notundertake' toacknowledgeall BUILD YOUR OWN PHOTO Equip- applicationsandwillcommunicate ment, 12 designs in two book& TO OTARY CONVERTER, 230v., D.C., EARTH LEAKAGETRIPS,half- onlywithapplicantsselectedfor Enlargers,printers,dryers,timers, aa to 230v., A.C., 200w.; £10 ;s.a.e. etc.,6/- ;p.pd. Below:- forbargainslistofTransformers, price, Siemens 30 -amp., G.E.C. further considetation. Rectifiers,Valves,etc. Lawrence, 15 amp.;as new.Prices from Box 40POWER TOOLS You Can Make No.103,C/0 PRACTICAL MECHANICS. from scrap, pipe fittings,etc. 134a, Cranley Gardens, N.10. EDUCATIONAL This amazing book of plans for cir- FASCINATING St -eel Tr acing cularSaws,lathes,band -saws,. jig- Machines for copying and en- URGENTLY, Teachers -saws,planes,tappingattachment, larging from newspaper and magazine WANTEDofHandicraft.Correspondence jigs, etc., has sold 250,000 copies, and drawings,sketches;interesting;5/-, MODEL DEALERS Cgurses,bestpreparation Write is a " -must" for every home work- post free.-Clayton.16,Westminster only, shop, 12/6 only ; p.pd.Below:- ATTENBOROUGH ModelRailway.' specialised.College Secretary, . Rd., Bradford, Yorks. Model railway specialists ; Marriott's, Bushby, - Leicestershire. M.ERICAN BOAT BUILDERS finest in the Midlands .Agents for, ,Success assured. L.Annual :28 boat plans, 8-22ft., .SAW BENCHES, 7in.24/151-, 8in. and stockistsof, many well-known BECOME A TEACHER ofWood- andotherhelpfularticles,.7/6 ; £5/10/-;CombinationLathes, firms.Why not ask for -acopy of work or Metalwork.Interesting p.pd.Below:- £10; Planers, £9/10/-; Motors, our A.M.R, Chronicle ?The latest well -paid work with pensionable Spindles.Send 4d, stamp for com- information regarding our stock, 1/-, CAR BODY REPAIRING. Complete plete illustrated booklet.H.P. avail- post free.. -82, Arkwright Street, Not- security. Long holiday& No previous A B C course ; Illustrated.; able. James Inns (Engineers), experience required. Expert rapid 7/6 ;p.pd..;listsfree.A.P.S.(P), tingham, and 64,Narborough Road,' postal coaching; -lowfees. -Books Sedgef ord, Norfolk. Marshall Street, Nottingham. Leicester, provided free. Send now for free The prospectus, Dept. 24, Chambers QMALL DENTIST'S SYRINGES, THE " LEADER" in its class. QHIPS IN BOTTLES.-The construc- College, 148, Holborn, London, E.C.1. S unrivalled " E.W." Lathe. Con- tional kit that tells you how to beautifully made all metal vertible from plainlatheto hand make them ;buildforpleasure or AM.I.Mech.E., B.Sc., CITY & instruments by leading makers. All traverse, backgear, and screwcutting for profits.; kits 6/- ea. from Hobbies Ilk GUILDS, Etc. Guaranteed parts heavily plated, and machined by just adding the appropriate unit. Ltd.,andmodelshops. postalcoursesforall Exams. and fromsolid. Smooth positive action. Cooper - Technical Divisions from Elementary Lapped piston and cylinder.Piston Send for details (20. stamp please). Craft Ltd., The Bridewell. Norwich. rod calibrated0-20. Idealfor pre- Credit terms-Youcanobtainan to Degree standard. Approximately ' cision lubrication without mess, and " E.W." for as little as £4/4/- down. MARINE MODEL SPECIALIST 95% successes. 144 -page prospectus Complete with Protectyourtoolsand equipment Plans, Engines, Fittings, 1/32in. free on request.B.I.E.T. (Dept. 967), many Miler purposes. fromrust.A packetof' V.P.I. " and 1/16in. Ply Stripwood, Timber, 17,Stratford Place, London, W.1. 6 strong hardened steel needles, in platedmetal case with hingedlid paper will do the job.Send 3/9 for Radio Control Equipment, Boat and FREE !Brochure giving details of and fastener.Ex -Ministry, new, un- a packet,orstampfordetails. Yacht Kits, Galleon Kits and Plans. courses in Mechanical and Pro- used. Worth ££££s. Our price Wanstead ToolSupplies,48,High J. Chappell, 393-5. Eccles New Road, duction - Engineering,Draughtsman- '9/6,post 6d.K. W. Logan, West - Street, London, E.11. Salford, 5. ship,etc.,fortheA.M.I.Mech.E., alley, Hitchin, Herts. A.M.I.P.E.,CityandGuilds,and ,SUPER KALEIDOSCOPES, 2/9; LONDON. - Robson's Hackney's other Professional ex amina tions. " CONSTRUCT Your Own Refrigera- carriage paid. Schofield, 5, Model Shop.149-151.Morning TrainwiththePostalTraining tor."This book, written by a TurnerBuildings,Luddenden Foot, Lane, E.9. (Tel.: AMHerst 2928.) Collegeoperatedbyanindustrial refrigerationengineer, isprofusely Yorkshire. Organisation ;moderate fees.E.M.I. illustrated with drawings and photo- BUD MORGAN, The ModelSpecial- Institutes,PostalDivision, Dept. graphs and tells you, not only how POLARIZINGKITS, assorted ist,22,Castle Arcade, Cardiff. PM30, 43, Grove Park Road, London, toconstructa Cabinet orBuilt-in laboratorygradescreensfor (Telephone:Cardiff29065.) Model (Associate of H.M.V.) Refrigerator,butillustratesmany simple adaptation to any size astro. Aircraft,Trix, Tri-ang,Graham W.4. that have -been built by amateurs and or terrestial telescopes, microscopes, Parish, Model Railways and Galleons; IP.R.E. TECHNICAL PUBLICA- are operating satisfactorily, 3/6, post cameras,etc.;suitableforastro. first-class mail order service Send TIONS. 5,500 Alignment Peaks free.Obtainable direct from author daylight observation, micro. analysis, for my 1953 price lists, price 3d. for superheterodynes, 5/9 ;Data for andpublisher,Robert C. Scutt, colour and cloud photography, gem constructing TV aerialstrength RefrigerationEngineer,52,Hadley testing, 3D cinema viewing, etc.; with HOBBIES LTD. have over 50 years' meter, 7/6 ;sample copy' The Prac- Way, London, N.21. experimentalspecimensandillus- experienceof catering for the ticalRadio Engineer,"quarterly trated instructions, detailing applica- needs ofmodellers, handymen and publicationoftheInstitute,2/; PINION WIRE for driving tion,principle, experiments in half - home craftsmen.Branches at 785, membership and examinationdata, B RASSwheels, etc., for model makers, and full -wave extinction,etc.,price New Oxford Street, London, and in 1/-. SyllabusofIpostalcourses 10 teeth x approx. lin. diam., and 6 10/- box; sample screens,2/6pair. Birmingham,Glasgow,Manchester, free and post free. Sec..I.P.R.E., teethxapprox.kin.diem.;-any -Below. Leeds,Sheffield,Hull, Southampton 20, Fairfield Road, London N.8. length up to10ft.,at 1/6 and 9d. and Bristol.Head Office: Dereham, per foot ;sample and postage1/-. ATOMIC KITS, reveals actual Norfolk. Armstrong, 55, Old Hall Street, Han- splitting of atoms, alpha particle FOR SALE ley,S.O.T. bombardment.etc.Harmless;lasts HORNBY DUBLO CONVERSIONS, HOUSE SERVICE METERS, credit for centuries !Comprising of minia- Duchess,Gressiey2 -railscale, and prepayment; available " PICADOR " ROTOSAW.Portable turenuclearemitterandtarget 52/6, 3 -rail scale, 42/6; Tankers 2 -rail, Universal Electrical. 221, circularsawattachmentfor screen built into micro, slides, with 42/6, 3 -rail, 32/6.Sheffield Electrical from stock. yourelectric drillfittedwith 4in 100X area microscope and instruc- Model Engineers, Shalesmoor, 'City Road. London, E.C.1. circular saw bigde, adjustable fence tional data; price 10/-; without micro- Sheffield. CIOMPRESSOR EQUIPMENT.Mis- to cut up to fin, in depth, ideal for scope, for use with own, 61 -.-Below. cellaneous Items; catalogue, lid. wood,plasticor soft metals ;33/- MODEL -MAKERS and Mechanics ! Price. 157, Malden Road, Cheam. each, post paid.Lambs -wool polish- ZAMBONI (VOLTAIL) PILES, 1,500 Hereisthesimple -to -operate ing- Bonnets, 5in., 4/3 each :Rubber volts. inexhaustible potential for Blow -lamp for all soldering jobs; the COMPRESSORS forsale. 3 CFM, Backing Discs,5in.,complete with static electric experimenting, charg. Britinol Self-acting Spirit Blow -lamp; 1801bs.sq.in.,on metal base, key,4/6 each; Abrasive Discs,5in., ing electroscopes, etc.; size 1 x 9iin., price 7/-, or gd. extra post and pack- withdrivingwheelandreceiver, 6 assorted grades, 2/-.Send 2W. for 8/6 ea.; c.w.o.; all postfree. ing, direct from Bi-Metals (Britinol) price £3. h.p. Heavy Duty Motors: listsof Saw spindles,VeePulleys J. K. M, Holmes, " Scientific Instru- Ltd.,BalfourMews,BridgeRd., P.M., price £3 ;carriage forward.Wheel- andBelts,PlummerBlocks,etc. ments," Dept. " Vizcaya," London, N.9.Illustrated list s.a.e. house. 1. The Grove.Isleworth. Sawyers,Ltd..St.Sepulchre Gate, Wolveleigh lice., Gosforth, NeWeastle- (Phone :Hounslow 7558.) Doncaste on-Tyne, 3. (Continued on next pogo)

www.americanradiohistory.com 348 NEWNES PRACTICAL. MECHANICS May, 1953 (Continued from previous page) WATCHMAKERS WOOD LATHES, Attachments, DRAWING SERVICES Motors and control Gear, Circu- THE B.R. ELECTRICAL PLASTIC GET YOUR TOOLS, Materials and lar Saw Blades, Spindles or Benches, BARGAINS in DrawingInstru- INJECTOR. The only machine Spare Parts from Western Watch Turning Tools, etc. Interested ? mentSetsand Slide -rulers. on the market for compression plastic Supplies Ltd.,17, Yorke St., Wrex- Then send6d.forourillustrated Sendforour catalogue now. BOx injection moulding ata reasonable ham.Send 6d. for lists. catalogue,No.529. D.Arundel& No. 102, C/o PRACTICAL MECHANICS. cost. Makes toy soldiers, brooches, yNTERCHANGEABLEWatch Parts, Co.,MillsDrive,FariadonRoad, etc.; nosmell; notrouble;no 1- Balance Staffs, Winding Stems, Newark, Notts. chemicals;plasticsets immediately Centre Wheels, completeBalance HANDICRAFTS Assemblies,Hands,Buttons,Main- PLYWOOD. -3/16in. Finnish Birch, ltfUSICAL MECHANISMS, Swiss bone hard; works off lighting veryclean,sandedstock ; 4 current; no experience needed ; springs, Tools ;send for lists.H. S. 17-1-made, forfittingincigarette Walsh,28, Anerley sheets,30in.x 30in.,18/- ;carriage makes 100 articles for 4/-. Sample StationRoad, paid.Stamps for lists of mouldings. boxes, etc., 22/6 each.Send 6d. for article free.New list of brooch and London. S.E.20. plywood and complete woodworkers' complete list of handicraft materials. farmyard animal dies; machine dies WATCHMAKERS' SCREWDRIVERS, supplies. Sawyers, Ltd., St. Sepulchre Metwood Accessories, 65, Church and plastic supplied ready for use. high tensile blades, swivel top ; Gate, Doncaster. Street, Wolverton, Bucks. The toy soldiers are better than any setof5graduated sizes,infitted lead soldiers.The only machine of box,5/-, post paid. Sawyers. Ltd.. MAHOGANY PLYWOOD, any its kind in the world; price £8/10/-. St. Sepulchre Gate, Doncaster. parcel £1 ;delivered ;c.w.o. WANTED Write for details of the machine and WATCH REPAIRERS and Experi- Following new:5 at 111 x 66 x lin., WANTED, Polish No. 3 Mine full list of moulds, all free, to :The menters. -10 Geneva watch 6 at 23 x 20 xtin.,12 at 14 x 26 Detector for ferrous- and non- Small Power Machine Co.,Ltd..4, movementsfromGoldandSilver xlin, 14at 14x23x in., 20 ferrous metals. Platts(Matlock). " Sunleigh Parade, Alperton, Wembley, cases, accept 20/- the 10 ;10 Eng- at14 x17 x fin.,30at14 x14 Ltd., New Street, Matlock. Middlesex. (Wembley 1383.1 lishLever Movements, capped and xfin..20at42x51xlin.,32 jewelled,30/- the10 ; 10assorted at 45 x 31 xlin.,8 at 66 x 51 x MODEL MAKERS.You need tools 1 -plateEnglishLeverMovements lin., 20 at23 x 6 x fin., PHOTOGRAPHY and materials.Send s.a.e. for from 18ct. Gold cases, 50/- the10. 16 at 78x 5 x3/16in., 12 at free copy of our catalogues.Ken- Merkel's,Jewellers,GreyStreet, 78 x 51 x3/161n. Following one ENLARGER and Camera Bellows nion's of Hertford. Newcastle -on -Tyne. side slightly glue stained:5at33 supplied ;also fitted.Beers, St. x23x3/16in.,7at23x23x Cuthbert's Road, Derby. HAVE YOU A WATCH youare 3/16in., 16 at 47 x 9 x 3/16in. M. unable to get repaired ?If so, Leader (19201. Gosford Street, HOBBIES send it to us by registered post for Middlesbrough. MISCELLANEOUS HOBBYISTS,handicraftworkers, estimate, no repair too difficult ;all FORMULASfor model - send6d. stamps for our illus- work guaranteed. The Melnor Horo- HANDYMEN.-New Timber, sound, 1,100 logicalDept.,32/2,Waterloo Road, seasoned,selected,thicknessed, makers, engineers. handy- trated catalogue," Perspex " Jewel - neatly bundled.Send for list.fin. men, etc.,3/9.P. M. Ashdown.3, craft, Flowercraft, etc Newing Nottingham. Raynham Terrace, Edmonton,N.18. Co., 96, Grove Vale. London. S.E.22. x lin.,11/3; fin. x 21n, 22/3; lin, x lin.,17/4;fin. x 21n.,32/3;lin. " How touse ex -Gov. TOY CASTING MOULDS, soldiers, WOODWORKING 3in.,48/6;lin.xlin.,21/6;lin. BOOKLETSLenses and Prisms," Nos. 1 and sailors, airmen,animals,etc.; TYLER Spiral Hacksaw Blades cut x 21n., 39/9; lin. x 3in.. 63/-; lin. x 2 price 2/6 ea. ;ex -Gov. Optical lists catalogue,9d.:Moulds for Plaster - in any direction at conventional 4in., 85/6;allper100ft. run; good free for s.a.e.H. English, Rayleigh work, plaques, ornaments and hacksaw speed without turning the lengths; immediate delivery; minimum Road,Hutton.Brentwood,Essex. order c.w.o.;carriagepaid. Coronation souvenirs.Moulds from work, 10in. Hacksaw Blades 4d. each 20/-; NEWNES " Complete Engineer," 3/6 ea. ;catalogue,9d. ; s.a.efor from leading tool dealers.Write to Generous sample bundle, 15/-. 69. Blacknell(Dept.75),Farnborough, 4 vols., with data sheets; first- list.F. W. Nuthall, St. Marks Spiral Saws,Ltd.,Trading Estate, class condition; £2/10/-. Jones, Road, Hanwell. London, W.7. Slough, for details. Hants.(Phone: 106.) Angeldown Farm, Wantage, Berks. GROW wonderfully decorative BUILD YOUR OWN REFRIGERA- miniaturesofRealTreesby The ' Adept Bench The OMR TOR, secret Japanese methods; fascinating, ADEPT 'LATHE all componentsavailable profitablehobby. Send 8/6 for Hand Shaper Iiin.centres,6in. atreasonableprices. Frigidaire guaranteedguideandselectionof Length ofstroke of between flowing cold units, £5; small units, ram slim. centres. Kelvinator,etc..£4; fh.p.heavy seed, or s.a.e. for details:Miniature dutyMotors, Trees.Dept. 90, RoomTwo, 3, No. /12, II Shaper, 8 lin. £3; Chrome Cabinet stroke. 1t Price 25 15s, 0.1. fittings, new, £1; -money back guaran- Bloomsbury Street, London. W.C.1. Price £16 17s. 8d. A good Range tee;s.a.e.for Postage and packing 341 (U.K.).TheofAccessories listand schematic TOLLS HOUSEFITTINGSand ArI1/554, rawer Adept ' 21in. lie. B.S.P. 4 -Jaw lode - is available diagram.Wheelhouse, 1, The Grove, Papers ;Wooden and Metal Toy 4 pendent Chuck. Reversible Jaws, 38,8. Isleworth, Middx.(Phone: Hounslow Wheels (trade supplied) ;illustrated F.W. PORTAS.S, MACHINE TOOLS, LTD. -7558.) brochure ;s.a e.Jasons.135, Nags ADEPT WORKS, 55, MEADOW STREET, SHEFFIELD, 3. Head Road. Enfield. Middlesex. Amateur RadioEnthusiasts IMPETUS Precision PLANERS BATTERY TROUBLES? THE INCOMPARABLE Circular safety type cutter -head High GLOBE -KING quality tempered steel knives. Tables Don't scrap your falling car battery SINGLE VALVES.W.RECEIVER WIRING ACCESSORIES mounted on machined inclined ways. or radio 2v. cell till you have tried WORLD-WIDE RANGE 11-100 METRES Groundtable -surfaces. Fences Renewbat "desulphater and con- CRYSTAL-CLEAR NOISE -FREE RECEP- All goods are of well-known manu- adjustable to 45 deg. ditioner. Works likea charm on TION ELECTRICAL BAND -SPREAD facture and carry a money -back guar- 4 in. MODEL.E9.10.0 middle-aged batteries.Clean and sate TUNING EXTREMELY LOW RUNNING antee.C.O.D. or C.W.O.All carriage Motorised. £18.10.0.6 In. MODEL to use with instructions, car size 3,-, COSTS paid. 228.10.0. Motorised £44.0.0.Send for post 6d. CABLE.-TRS Flat Twin, 1.044, 55/- : Catalogues of otherImpetus ' Products. Catalogue Free. Stamp for postage. 3.029, 75/-7.029, 1151-. PVC Sheathed CHAMPION PRODUCTS, JOHNSONS (RADIO) Flat Twin,1.044,52/8 3.029,70f-. JOHN P. M. S. STEEL, Dept. SO, 43.Uplands Way, London. N.21. 46.FRIARSTREET. 'WORCESTER Allper100yds. PVC Cables are SINGLET. YORKS. Phone: LAB.4457. suitable for both interior and exterior Phone :BINGLEY 3551 (4 lines). wiring, and can even be burled in the WEIBLETAIR PISTOLS ground.All types and sizes of Cables available in 25, 50 or 100 yd. coils. MOTORISED SAW BENCHES Marvellously Heavy cables cut to desired length. PLASTICS accurate for Switches,1/8 ;2 -Way, 2/, Ceiling sold ;Perspex sheets and offcuts Standard Range from 6in. to 301n. Saws. target prac- Roses, 10d. Lampholders, 10d.3 -Pin in stock, large quantities of clear Complete with Saw and motorised. tice. Sw. Sockets, 5a., 4/615a.. 6/8.We 61n.611.15.0.8in. 213.19.6. 121n. £16.10. No licence required to offer a complete service and can supply and coloured, Acetate sheets and Or supplied unmotorised for your power. almost anything electrical. Advice.. rods, Catalin rods, etc. Spindles. Bearings, Motors. Pulleys, purchasefor useon on Installations gladly given. Send Belts. enclosed premises. Please send your inquiries to : Send 10d.for Illustrated Catalogue - WriteforCatalogue01 AIR for Lists. Handbook of Saw Bench and Trans- PISTOLS, AIR RIFLESand HUNT & CO., MULTITEX LIMITED mission design data. Accessories. STEPCOTE HILL, EXETER 10-11, Archer Street, London, W.1 Beverley Products, Ransk114 9, Notts. WESLEY & SCOTT LTD., Tel.: GERrard 9520 and5728 106. Weaman Street. Birmingham Eng. CAN YOUPLAY THE PIANO? If you are a music lover, why have you not se- OF::EDS REFILL YOUR OWN BALL PEN RATCHET & REVOLUTION QUIred this enjoyable accomplishment 1 Has the prospectofpractice Ipractical DAYS APPROVAL KOLOID REFILL KIT practice Idiscouraged you ?It is to aII PRACTICAL MECHANICS readers POST FREE 3/6 PER OUTFIT COUNTERS unnecessary. My pupils' roll grow. COMPLETE WITH ILLUSTRATED Askfor daily I state it in every advertise- INSTRUCTIONS AND TOOL LeafletNo. 1817 ment. ItIs your assurance of success. My class Is seldom leas Contains Ink for I Blue, Violet, Speed-up to 6,000 r.p.m. than 2,000 pupils.I have taught over 12-15 Refills Red, Green. s7,150 ANDICAN TEACH YOU G. H. HOLMES, B.& F. CARTER -- 12 lemons) even if you do not know 67, Brunswick Park Road, London, & Co., Ltd.,Bolton 5 a note. Ordinary musical notation only N.II. used, no freakish methods. FREE Book and advice.Say Beginner, Moderate. Advanced.(Block letters please.) MR. H. BECKER (Dept. 558), GENERAL -The Hall. Centurion Rd.. Packed withfacts,figures and data! CERTIFICATE Brighton, Sussex 4(X) pages instruction, reference, diagrams. tables I Immense contents, Include lathe OF EDUCATION EXAM. work ;small tools ;filing; fitting and EITHER IT IS GROW MONEY marking out :dividing bead ;micro- THE KEY TO SUCCESS AND IN TWELVE EASY LESSONS meter,vernier ; mensuration. screw - SECURITY cutting ;gear-cutang ;hardening, tem- Essential to sueocas In any walk of life. of it isal ROY GENDERS of T.V. Fame and pering ;electroplating :silver soldering : Whatever your age, you can now prepare Authorofnumerousgardening brazing :welding soft soldering ;pa- at home for the important new General Books has written these lessons tents, etc.Get it NOW Cert. of Education Exam. (you choose showing how your garden can ON APPROVAL! POST COUPON NOW .1 your own sub:ects) on " NO PASS-NO JUBILEE has been a, registered trade name supply you( with all the Vegetables FEE," terms. for30years,and maynotbe usedto and Flowers you need and leave a to loonosego so-cs:1-wo-e- I os11111/U SEND FOR FREE 136 -PAGE 1100K describe anyother clip. surplus you can sell for Ws each To: A. THOMAS & CO. (PMI), III, Full details of how you can obtain this year.The Lessons are specially valuable Certificate are given in our written for the Amateur. They are Buchanan St., Blackpool.Send P.M.H. on 136 -page Guide-FREE and without concentrated instruction showing APPROVAL-I enclose13/3OR send C.O.D. I how you can MAKE MONEY FROM obligation.Write to -day. YOUR GARDEN. Send for the can returnhockw thin 5 days for full refund 11.T.1.. 160,AVON HOUSE, 356-366, THE FINEST CLIP is if OXFORD STREET, LONDON,Iva. wed! complete Course costing only 10/-. 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www.americanradiohistory.com May, 1953 NEWNES PRACTICAL MECHANICS 349 ing the efficiency of the unit ?Can Iefficient blowpipe isspecialist work and it increase the discharge pressure ? is suggested that a blowpipe is purchased Will you please advise me on the designfrom a reputable manufacturer. for a coal-gas/air blowpipe for use with QUERIES and whatever method you may advise for useChlorophyll from Grass of the vacuum cleaner.I need as small a flame at as high a temperature asTAM at present producing dried grass possible. Iin commercial quantities.Please ENQUIRIES The discharge pressure of my cleanergive me an outline of method for pro- is approximately .45lb. persq.in.ducing chlorophyll from same. -H. A. (ruin. water gauge pressure). -A. L. N.Taggart (Belfast). Stephens, (Kingston -on -Thames). WE suggest that you " kill " the grass, THE only way you can decrease the bore prior to drying, by immersion in a vat Astamped, addressed envelope, three penny of boiling water. Drain superfluous liquor by stamps, and the query coupon from the current of the discharge pipe without decreasing issue, which appears on the inside of back cover, the capacity of the machine is to reduce thespreading on racks, and then extract by means must be enclosed with every letter containing a ofindustrial length of the pipe toapoint whereits spirit(ethylalcohol). The query.Every query and drawing which is sent alcohol extract of chlorophyll is_then distilled must bear the name and address of the reader. resistanceisequal to that of the existing Send your queries to the Editor, PRACTICAL ain. diameter piping.You will also requirefrom a steam -jacketed still, the alcohol being MECHANICS, Geo. Newnes, Ltd., Tower House, thus recovered, while the chlorophyll remains Strand,London.W.C.2. a fitting reducing gradually from tin. diameter SouthamptonStreet, toin. diameter in order to reduce frictionalbehind. lossestoa minimum.The only way to We would suggest experimenting on the increase the delivery pressure is to increaselaboratory scalefirst,for you may findit unnecessary first to partially dry the boiling Use of Proportional Dividers the fan speed-i.e., the pressure varies as the square of the fan speed.It must, in so doing,water extract -possibly pressing would suffice. THAVE been presented with a pairbe remembered that the horse -power required 1ofproportionaldividersmade Moulding Kaolin nearly a century ago which I hope to use in my work as a draughtsman. THAVE 2 cwt. of powdered kaolin. There are four scales marked on these Readers are asked to note that we have I Can you please give me a formula dividers, three of which I am not sure discontinued our electrical query service. using this kaolin to produce a granite - about. One scale for lines I have used ; Replies that appear in these pages from hard product suitable for tiles or for time to time are old ones and are pub- casting ?-Evan J. Thomas (Aberayron). theothersaremarked" circles," lished as being of general interest.Will " planes " and " solids."Please advise readers requiring information on other THE kaolin must be thoroughly pugged with me whatproportionsof" planes " subject; please be as brief as possible water into a soft paste of such con- " circles " and " solids " can be found by with their enquiries. sistency that, when a piece about2.1.11.diameter these dividers and how the scales have is squeezed tightly in the hand, it will repro- been arrived at. -E. Denham (London, duce the fine lines of the skin.If paste is too N. x6). will also be increased, i.e., the power requiredhard, add a little water and re -pug. A woodetr THE scales are arranged to give the pro-to drive the fan varies as the cube of themould, preferably of teak, must be made, portions marked on each scale as below :fan speed. shod on top and bottom edges with steel Lines :Give proportionate lineal measure- The pressure quoted will be insufficient forstrips about r/ 6in. thick. The thickness of ments. the average commercial spray -gun, and it isthe mould should be that of the tile. Lubricate Planes :Give proportionate areas. considered that it is also too low for blowpipemould with water (slop moulding) or with Solids :Give proportionate cubic contentsoperationif a high flame temperatureis sand(sandmoulding).Next pick up a or volumes. required.The design and construction of anquantity of paste from the mass, " bump " Circles :Give the side length of a polygon it on the previously sanded or watered bench, when the opposite points are set to the radius turn it and bump it five times, and then by a of the circumscribing circle and the fulcrum taut steel wire in a frame slice the mass into joint index has been set to the number of THE P.M. BLUE -PRINT SERVICE " clots " a little longer than the tile and about sides required for the polygon.To use the gin. thick. Dip the empty mould into water instrument, set the joint against the number 12FT. ALL -WOOD CANOE. New Series. No. I, or sand and then place it on the bench which 3s.6d.. has been similarly treated.Lift a clot from of sides of the required polygon, open the 10 -WATT MOTOR. New Series.No. 2,3s.6d.* long points to the radius of the desired circle, the pile, and after throwing it forcibly into then the short points are at the required COMPRESSED -AIR MODEL AERO ENGINE. the mould, compress it and fill up the edges separation equal to the length of the polygon New Series.No.3, 5s.* and corners by a series of blows or punches required. AIR RESERVOIR FOR COMPRESSED -AIR with the hands. Surplus paste is removed by The way the scales have been arrived at is AERO ENGINE. New Series.No. 3a,Is. drawing a wetted piece of wood overit. as follows : "SPORTS" PEDAL CAR. New Series. No. 4, 5s.* Drying -off can be done slowly in an open shed, Lines : Indexgivesdirectproportion F. 3. CAMM'S FLASH STEAM PLANT. New the tiles being stacked in chequer work to aid between lengths of the long and short legs. Series. No, 5, 5s.* ventilation. This can be done only in summer Planes :Index gives proportion between SYNCHRONOUS ELECTRIC CLOCK. New months.For quick drying and hardening, long and short legs, arranged to equal the Series. No. 6, 5s.* artificial heat must be provided or arrange- square root of the index number. For instance, ELECTRIC DOOR -CHIME.No. 7,3s.6d.* ments made to borrow the use of a kiln at should you set the Plane Index to " 3" and ASTRONOMICAL TELESCOPE. New Series. some school of pottery. open the long legs to the length of side of a No. 8 (2 sheets),75.* CANVAS CANOE.New Series.No.9, 3s. 6d.* square area, the other legs will give the length ElectrodepositionQueries DIASCOPE.New Series.No. 10,3s. 6d.* of a square of one-third the area. RECENTLY I saw in Practical Mech- Solids :In a similar way the index here EPISCOPE.New Series.No. 113s. 6d.* anics an article dealing with copper divides the lengths of the legs in proportion PANTOGRAPH. New Series. No. 12,Is. 6d * deposition on non-conductive materials. to the cube root of the index numbers. COMPRESSED -AIR PAINT SPRAYING PLANT. New Series. No.13, I should like more information on the Should you set Solid Index to " 3 " and the 7s. 6d.* following points. long legs opened to the length of side of, say, MASTER BATTERY CLOCK.* Blue -prints (2 sheets),3s. 6d. What type of transformer is necessary a tank, the other will give the length of sides Art board dial for above clock, Is. for 230 volts 5o cycles A.C. input to give of a tank of one third the capacity. OUTBOARD SPEEDBOAT x.2 volts, variable amperage from 6-40 Circles : The index is set to give the correct 10s. 6d.per set of three sheets. amps D.C. output ? What firms would length of side when the long legs are opened LIGHTWEIGHT MODEL MONOPLANE. undertake to build this ?Is it possible to the radius of the circle circumscribing Full-size blue -print, 3s.6d. tobuildthistransformer from ex - the desired polygon, the index setting being P.M. TRAILER CARAVAN. government parts ? equal to the number of sides in the required Complete set,10s. 6d.* When dealing with a number of articles polygon. P.M. BATTERY SLAVE CLOCK -2s. what is the best method of making con- " PRACTICAL TELEVISION "RECEIVER. tact ? Could I put them on copper plate Reducing Vacuum Cleaner Discharge Pipe (3 sheets),10s. 6d. or hook them to a bar as a negative Bore P.M. CABIN HIGHWING MONOPLANE. cathode ? TWISH to utilise my vacuum cleaner to Is.. Theabove blue -prints are obtainable, post free, When using plaster forms what is the I supply air under pressure for use with from Messrs. George Newnes, Ltd., Tower House, best method of contact to the graphite blowtorch and paint gun. How can I best Southampton Street, Strand, W.C.2. film, also what other conductive coatings reduce the 2in. diameter outlet to a bore An * denotes constructional details are available free can be used and where can they be of, say,in. so that I may use a less with the blue -prints. purchased ?-A. Heywood (Ashton -under unwieldy pipe, without excessively affect- -Lyne).

www.americanradiohistory.com 350 NEWNES PRACTICAL MECHANICS May, 1953

thecheapestmethodofcreosote and can be applied to floors, joists, PROBABLYobtaining 6 to 40 amps at i to 2 voltsetc., in a single application. would be by means of a car battery.You (2) You can use the commercial grade may be able to obtain quite cheaply an old carcreosote and when dry wash over all surfaces Information battery which has one or two defective cells ;with a 4 per cent. solution of sodium fluoride. one 2 -volt cell, or preferably two or moreThis substanceisan excellentfungicide. connected in parallel, would be suitable forYou must remember that it is poisonous and Sought your purpose. The battery could be chargedetches glass, so the mixture should be made locally or by means of abattery chargerup in a pail.The chemical can be obtained Readers are invited to supply the required consisting of a step-down transformer andfromVicsons,Ltd., 148,PinnerRoad,informationto answer thefollowingqueries. metal rectifier, and quite a low charging currentHarrow, Middx. could be used. " Socredes," of Glasgow, asks : Could Another method of obtaining a supply ofArtist's Enlarger/Reducer you give me some up-to-date information on 6 to 4o amps at I to 2 volts is by means of COULD you give me some informationthe subject of " shaded poles "in electric a motor -generator set consisting of a mains on building the type of photographicmotors ? voltage motor which drivesasmall D.C. I understand this consists of some slight dynamo, the voltage output being controlledapparatus used by artists for reducingmodification to the pole face. by a variable resistance in the field circuit ofor enlarging the image of a photograph What form does the modification take ? for the purpose of line drawing ? I the dynamo. Another method would be tobelieve this is something like a camera Is such a modification possible on a per- usearotaryconverter. However,suchobscura, and throws an image of themanent magnet, and if so, what effect might apparatus islikely to be rather expensive.photograph on to a ground glass screen.it be expected to produce ? Alternatively, you coulduseastep-down transformer to supply a metal rectifier havingAlternatively, I could make a line tracing Mr. F. E. Siggers, of Ceylon, asks : the required output. Messrs. Galpins adver-of the photograph which could be placedHave you at any time published a construc- in the apparatus and projected on totional article on exhaust -operated three-, four - tise a transformer having an output of 50-70the drawing -boardinthedimension amps at 2 to TO volts, or we could supplyrequired, the instrument being arrangedor five -note horns for fitting to a car, please ? constructionaldetailsforatransformer ifto slide on a horizontal rod as shown inCan you give me enough information to required. A metal rectifier could be obtainedthe accompanying sketch. make one ? from one of the following firms : I have a spare 5in. f4.5 lens previously Standard Telephones and Cables,Ltd.,used in an enlarger and am wondering Mr. H. Comber, Ireland, writes :I wish Connaught House, Aldwych, London, W.C.2.if this would be suitable.-G. Hodgesto make a mixer to handle ice-cream mixes of Crypton Equipment,Ltd.,BristolRoad,(Essex). from two to four gallons. My idea is to fit an Bridgwater. Westinghouse Brake and Signal extension to the shaft of a motor and invert Co.,Ltd.,82,York Way, London, N.T. FOR projectingatracing made from athe gadget into a large can. Partridge Wilson and Co., Ltd., Davenset photograph the best scheme would be (I) What horsepower and speed would the Electrical Works, Leicester. to place the drawing -board horizontally on amotor need to be ? You could either suspend the article ortable, and the box carrying the lens, tracing (2) How should I loin the extension to the restit on three contact points on a wireslide and lamp vertically above it.The boxmotor shaft ? frame, not a plate, connected to the terminalcould then be supported upon three detach- (3) Would the shaft need support other than of the vat. A preliminary coating which youable legs, as shown in Fig.I. that given by motor -bearings ? may find useful consists of a hot mixture of one Fig.2 shows the manner in which the (4) Would a thrust bearing be necessary part of paraffin wax, two parts of beeswax,actual photographic image can he projectedon the motor ? and two parts of powdered graphite, thesedown on to the drawing -board. being melted and mixed together and after- Providing the angle of the 5in. f4.5 lens Mr. R. Hamblin, of Watford, sends the wards evenly applied to the article. When theis wide enough, there is no apparent reasonfollowing query.I wish to construct a plug coating has become quite cold a little powderedwhy this should not be used.It is certainlysand -blasting unit.I have a compressor, also graphite should be sprinkled on the surfaceworth trying out. a lathe. and brushed vigorously with asoft brush. You will have to pro- Please tell me how to set about it. However, this method should not be used on videadequateventila- articles which will afterwards be washed in tionforthelamp or Mr. J. B. Ball, of Morecambe, writes : hot water or the wax may be melted arid the lamps. Will you please tell me how to make a revolv- coating stripped off. ing lampshade which uses the convection currentsproduced bytheheatfrom an Large's Storm Glass electric lamp ? T HAVE a barometer which is called a Suspension and sliding rod I.Large's Storm Glass. It is composed Fig.t. of a glass tube Lin. diameter and 5in. long, sealed at both ends, and contains a liquid and some sortof crystalsin Lens in focusing colla, suspension. When the weather is to be fine the crystals remain at the bottom of the tube and when rain is imminent the crystals rise to the top. Could you give me some indication as to what the liquid is ; what the crystals are and method of construction ?- N. Mather (Coventry). THEREare severalformulaeforthe Slide holding mixture contained in a Large's Storm --tracing Glass, but allcontain the same materials : 120Z. flake camphor, 3oz. muriateof ammonia, 3oz.nitrate of potash, 21,pints alcohol, 2 pints distilled water. A suitable amount of this mixture is placed f within the glass tube and the end scaled by Hot airvents heat.It is not under vacuum. Photograph Lamps Glass to keep Anti fungusCreosote heat outside box TWISH to increase the anti -fungus Drawing 1 properties of ordinary commercial board grade creosote.It is to be used on floors, joists, etc., of a bungalow badly affected Legs (3) by the floods at Canvey. Can you help Lens adjustable for focus and (telescopic) me, please ?-T. Young (Isleworth). Legs adjustable for height YOU can adopt either of the suggestions Drawing given below : (I)Coppernaphthenateis solublein Artist's enlarger/reducer apparatus

www.americanradiohistory.com May, 1953 NEWNES PRACTICAL MECHANICS 351

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352 NEWNES PRACTICAL MECHANICS May, 1953

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LEARN THE PRACTICAL WAY Aspecially prepared set of radio parts from which we teach you, in your own home, the working of fundamental electronic circuits and bring you easily to the point when you can construct and service a radio set.Whether you are a student for an examination, starting a new hobby, intent upon a career in industry, or running your own business -this Course is intended for YOU -and may be yours at a very moderate cost. Available on Easy Terms. WE TEACH YOU:Basic Electronic Circuits (Amplifiers, Oscillators, Power Units, etc.)Complete Radio Receiver Testing & Servicing. POST IMMEDIATELY FORFREE DETAILS TO: E.M.I. INSTITUTES, Dept.144 X Grove Park Road, Chiswick, London, W.4 *Experimental Kitsalso Name form part of the follow. INSTITUTES ingcourses :Draughts- Associated with Address manship, Carpentry, MARCONIPHONEu Chemistry, Photography, COLUMBIA & MV :am Commercial Art, Etc. (His Master's Voice)

I. C. I 2 SPARKS' HIGHSTONE UTILITIES SolderingIrons. -Our new streamlined iron is fitted with a pencil bit, 200/250v. DATA SHEETS 50 watts, 11/8. Standard Iron with adjust- SimplestandFinest 4etwate wimpy able bit, 200,250 v. 60 watts, 13/6. aretheSafest, IleavY ConstructionalSheets ofGuaranteed Duty Iron, 150 watts, 16/6, allpost 6d and Tested Radio Designs. Meters. -15 v.,2iin., m/c., 9/6 ;150 v. Sin., m/c., 10/- : 3.5 amp. 2in.. T.C.(P- S amp., 21in.. T.C.. in case with switch, 9/6 101 m/A, 21n.. mle.. 7/6: Meter Movements Units with 2-5011 microamps 7/., post 1/-. ofaOnce Bell Transformers.- These' guaranteed SPECIAL transformers work from any A.C. Mains, giving 3, 5 or 8 volts output at I amp.. operate bulb. buzzer or bell.Will supply ANNOUNCEMENT light in bedroom or larder. etc., 9/-. Similar Transformer but output of 4, 8 or 12 volts. 12/6.Both post 8d. BELLS for use with either the above or batteries, 6/- poet 6d. BUZZERS. 3/9, or Heavy Duty, 4/6. post 5d. INTRODUCING Ex.R.A.F. 2 -valve (2 volt) Microphone Amplifiers, as used in 'plane inter -corn., in self-contained metal case ;can bo used A NEW to make up a deaf aid outfit, Intercom- munication system, or with crystal set complete with valves and Fitting instruc- tions. 20-, post 2/-.Useful wooden box SERIES with partitions to hold amplifier, 21- extra. Ditto. less valves. 10,-.One valve ampli- fier, complete with valve. 10/6, post 1/6. THE Hand Microphones, with switch in handle, and lead. 4/6. Tammy. 6!-. Similar lnstru " M/S" SERIES OF AMPLIFIERS Precision built with watch -like accuracy. meat, moving coil, 7/6.All post 9d. I am happy to be able to announce that the neat,light and strong. records up to Mike Buttons (carbon), 2/-. Moving Coil. circuits contained in the booklet, " The 10,000 miles and then repeats. Complete 4/6. Transformers, 5/..All post 4d. each. Amateur's GuidetoValveSelection" Sparking Plug Neon Testers, with vest- (published by Messrs. Mallard, Ltd.), ARE with striker and rust -proofhubspindle pocket clip, 3:3, or with gauge, 3/8, post 3d. NOW AVAILABLE, through k led permission bracket.Chromium placed finish. S.B.C. Neon Indicator Lamps,for use on Price 7/6. mains to show 'live " side of switches, etc of 3/6, post 4d.Neon Indicator, complete MESSRS. MULLARD LTD. with condenser, pencil type with vest-pocket clip. 7/6, Post 5.1. in my usual Crystal Sets.Our latest model is a real radio receiver,fitted with a permanent SPARKS' DATA SHEET Form. crystal detector.Have a set in your own room, 12/8. poet 8d. De Luxe Receiver. In THIS UNIQUE INNOVATION places for the polished oak cabinet, 19/6. post Spare first time inthe history of the Radio Permanent Detectors,2/-each. When Amateur, a combination available to every ordered separately, 2/6 :with clips and Constructor which surpasses anything yet screws, 2/10. post 3d. headphones, brand offered - new, S.G. Brown. G.E.C., etc., 15.-, 23/- and super -sensitive, 30/- a pair, post Sd. New THE FINEST VALVE TECHNI- Headphones, 10/- a pair.Balanced arma- ture type (very sensitive).12/6 a pair. CAL SKILL PLUS THE FINEST Both post 8d.New Single Earpleees, 3/6.Bal. armature type, 4/6 ex R.A.F. PRACTICAL DATA SHEET. earpiece. 2/6, post 4d.headphones, in good order,61- (better quality,7/6).all post 9d.(All Headphones listed are suitable for use with our Crystal Sets.) Send 214. stamp for my latest List which Money refunded if not completely satisfied. gives full details of the above, and the 27 other tested and guaranteed designs. ciaeRoad's CYCLOMETER HIGHSTONE UTILITIES 58,NEW WANSTEAD, LONDON, Eat. ItL. ORMOND SPARKS (M) New illustrated List sent on request with 48A, HIGH ST., SWANAGE, DORSET JOSEPH LUCAS (CYCLE ACCESSORIES) LTD CHESTER ST BIRMINGHAM 6 lid. stamp and S.A.E. Letters only.

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