ELECTRICAL PROBLEMS

Wanganui Chronicle, Volume LXXXII, Issue 19478, 26 December 1925, Page 15 (Supplement)

ELECTRICAL PROBLEMS

USE OF A DYNAMO CLUTCH CONDENSER EFFECTS The neat arrangement of magnetc leads on the engine has always been somewhat of a problem. Even at present time the leads on many cars present a straggling, untidy appear anre. In some instances fibre clini an* used at several places to keep th* loads together. Another method is t‘ pass the leads through a fibre v’lb with holes drilled in it tit correct dis tances to allow each separate lead tc pn s through to the sparking plug foi which it is intended. Tt is not easx to improve on this method. On the other hand, a metal tube of brass oi copper looks considerablv better, par tieularly if it he bent downwards towards the distributor of the magnetc •'d the end brushed with a well-round •*d end piece of figre or ebonite, the *mall holes for the separate leads t< pass through being similarly bushed. A Condenser Effsct This method, although mechanic? Th sound, introduces some electrical inefficiency inasmuch a« the metal tube act' as one of the 11 plates’ of a condenser,

the other 1 * plate” being represented by the copper wires of the cables, lane the rubber coating is dielectric. Consequently. as this condenser has to bi alternately charged and discharged, ii ■its a certain amount of check on the flow of the current to the respective plugs. The amount of electrical energy given by a modern magneto is. bower. so considerably greater than i< ueiiially necessary* to ensure ignitior (hat the condenser effect won I<l prob ■ ably not be of any practical import : ance. Incidentally, the condenser effect 1 often proves misleading to those unac : qua in tod with it. For example, it is . sometimes supposed to be a tc-st of a j cable to pass the fingers along the . rubber insulation whilst the engine is i running in a darkened garage. Small i sparks are seen to pass from the cabh j to the fingers, and the inference is ; that the cable is leaky and defective. This effect, however, is observable with a new and sound cable. The sparks seen are solely due to induction through the rubber covering of the i cable. A leaky c’able would, of course I spark through the insulation, but in i this ease the tester would receive a j strong shock, which does not occui when induction takes place. Fitting A Clutch On The Dynamo [ The suggestion once made in the

columns of “The Motor” that the dynamo should be provided with a clutch so that it could be disengaged when not required for charging so as to save wear, is not a new idea, writes a correspondent. The same principle was applied to one or two of the early types of dynamos which had a friction drive from the rim of the flywheel, consequently by mounting the dynamo on a spring-tensioned swivelling bracket the friction pulley of the dynamo could be brought into contact with the flywheel as and when required by an ordinary wire control from the d'ash. There is no difficulty about fitti'.g a clutch, but several objections might be advanced. It would mean a considerable increase in the cost of loctrical equipment. The control of the clutch would have to be combined in some way with the charging switch, otherwise there would be a tendency to neglect the charging. Then there is the question whether this suggested refinement is worth while in the amount of wear of the carbon brushes it would have. Normally there should be no appreciable wear of the commutator or the ball bearings. An alternative and much simpler and cheaper plan would he to arrange a brush-lift-ing device operated from the charging switch, which would enable the dynamo to run practically free and frictionless when not charging. Tn certain cases there is sone undue wear of the commutator and brushes due to excessive pressure of the brushes on the commutator, and the use of brushes of a hard and gritty nature that tend to grind the copper bars of the commutator. A brush-lifting gear would minimise undue wear in such cases. Repairs To Celluloid Battery Cases The eases of celluloid batteries that have seen much service are prone to'

develop cracks, with consequent leakage of acid. Careful examination should first bo made to see if the trouble is due to swelling of the plates thereby causing interior strain on the sides of the casing. If this is so, a repair will not last for long and the battery w T ill soon have to be scrapped, as the plates will continue to swell. If there are no adverse conditions, a crack can be sealed by first preparingsome celluloid cement by dissolving a few’ cuttings from an old celluloid sea-son-ticket case in amyl acetate, a solvent which can be obtained at any largo chemist’s. A patch of the same thin celluloid should he cut, allowing an ample margin. Roughen the surface round the crack with fine glasspaper and rub over with the cement, several coatings being applied, and do the same to the patch. Before the surfaces become quite dry apply the patch, press down well and keep in position for a few hours with a small block of wood secured by string. When the cells are of ebonite—common practice at Iho present time—they will have to bo sent away for repair.

LARGER ENGINES

SOME AMERICAN TENDENCIES. Although American light sixes with power units of less than Sin bore are increasing in popularity, there is no doubt that the American motorist still inclines strongly toward powerful cars with exceptional top-gear performance and accelleration. While there is scope for still smaller and lighter American ears similar to many of the British four-seaters, the low price of petrol enables the American motoris to attach very little importance to the economy of an engine. Taxation on the basis of formula, horse-power does not worry the American designer, as it harasses British producers, and when greater power is demanded the American manufacturer adopts the simple expedient of increasing the bore of the engine. During the last year the engines of four famous American cars have been increased in size, thus proving that for home use power is a vital consideration. The latest car to feature an enlarged engine is the 1926 Buik. Tt followed the example set by the Chrysler ami the Essex. The Standard Buick for 1925 had an engine with a bore of 76 m.m. which gave a rating of 21.6 h.p. and a capacity of 3127 c.e. The engine of the new Standard Buick has been increased three millimetres in bore giving a capacity of 3353 c.e. and 23.4 h.p. The Buick Master Six previously rated at 27.5 h.p. is now 29.4 h.p. as the result of an increase of three millimetres in the bore. The Chrysler Six of 21.6 h.p. now carries a larger engine rated at 23.4 h.p. The bore has been increased three millimetres, causing the capacity to be increased from 3266 c.e. to 3586 c.c. Essex Sixes for .1924 were* rated at 16.5 h.p. The engine was 66. G m.m. by 101.5 m.m. For .1925 both the bore and stroke were increased to 68. 3 m.m. and 108 m.m. respectively, bringing the capacity from 2130 c.c. to 2374 c.c., and the horse-power to 17.3. The .fourth car to adopt a larger engine was the Rugby . Former models had a bore of 79.4 m.m. and .15.6 h.p. The type of engine fitted for this year had a bore of 85.7 m.m. and a horsepower of 18.2.

Several American manufacturers will not introduce their .1926 models until the New York Show next January. It will be interesting to observe if there are further developments in the craze for large engines. While any increase of power may enhance a car in the eyes of an American, and perhaps a colonial motorist, it is not likely to commend itself to Ihe English buyer. Larger bores mean increased taxation at the rate of £1 per horse-power. When there is any reason for increasing the power output of the modern English engine, it is usually effected by some refinement in design or balance, or perhaps by an increase in stroke, thus avoiding heavier taxation. In building bigger engines the American designer is probably meeting the requirements of his own vast home market against which the British sales are iclativelv small.

THE SPARE WHEEL USE MEANS LONGER LIFE. PERIO DIG A L EX A ATI NA TION NECESSARY. Detachable wheels are most useful things to have on one’s car, and a spare wheel tyre in case tyre trouble is encountered —that is to say, so far as it is pissible, for a second ])uncture, or, if two spare wheels are carried, a third, will make it necessary to do some tyre rt,‘pairing on the road. When away touring, it is a wise precaution to always repair or replace a punctured tube and inflate same to driving pressure at the conclusion of a day’s run, or before nightfall if the run will extend into darkness. The degree to which the tyre on the spare, wheel should be inflated is open to argument. Some motorists inflate up to front wheel pressure, in which ease it is necessary to use the inflator if it has to be fitted to a rear wheel, but it would be rather less trouble in the end to inflate it to roar wheel pressure and let out some of the air if it is wanted on a front wheel. Releasing air is less tremble than inflating, but in any case the pressure should be tested with the guage before resuming one’s ’journey after changing a wheel, and if the spare wheel tyre has not been kept up to the regulation pressure it may be necessary to go to the trouble of getting out he pump in any case.

This brings one to another point. It sometimes happens that a wheel is very difficult to remove, especially if one has to work single-handed by the roadside. If the car be new, this may be due to the enamel or paint making it stick on the hub; if the car has seen much service, it may be because the parts are rusted. It is therefore a very good plan to make a practice of removing all the wheels from time to time ami thoroughly greasing the inside parts. This may be done at the time of the periodical overhaul, or the wheels may be taken singly at any time which happens to be convenient. Some owners have a habit, which may be strongly recommended, of changing each wheel in turn with the spare wheel at moderate intervals. In this way all the five tyres get approximately an equal amount of wear. The owner becomes an adept at wheelchanging, and the wheels may be relied upon not. to stick. The 1a.4 two items will be the means of saving many minutes —ami perhaps very valuable minutes —on the road. The first is perhaps not quite so obvious; but tyres depreciate like all rubber goods with lime and exposure, therefore the spare tyre should be used from time to time to prevent perishing of walls of casing. Some motorists leave their spare tyre unused or exposed for many months at a time, with the result that its useful life is considerably shortened. It is more economical to use a spare tyre than leave it unused in the carrier for a lengthy period.