Part 6 (1/2)

Every axle of a railway train carries a wheel at each end, rigidly attached to it When rounding a corner the outside wheel has further to travel than the other, and consequently one or both wheels entle, however, that the aine, motor car, or tricycle the case is different, for all have to describe circles of very sth of the vehicle Therefore in every case a _coear_ is fitted, to allow the wheels to turn at different speeds, while pererated sketch of the gear The axles of the s and a central casing (not shown), and tere bevel-wheels, C and D Between these are s drum If the latter be rotated, the bevels would turn C and D at equal speeds, assus We will suppose that the drum is turned 50 times a minute Now, if one wheel be held, the other will revolve 100 times a minute; or, if one be slowed, the other will increase its speed by a corresponding ae_ speed remains 50 It should be mentioned that drum A has incorporated with it on the outside a bevel-wheel (not shown) rotated by a smaller bevel on the end of the propeller shaft

THE SILENCER

The petrol-engine, as now used, eh pressure If unchecked, they expand violently, and cause a partial vacuum in the exhaust pipe, into which the air rushes back with such violence as to cause a loud noise Devices called _silencers_ are therefore fitted, to render the escapea number of small apertures The simplest form of silencer is a cylindrical box, with a nu fro into the box her than that of the at froentle hiss rather than a ”pop” There are numerous types of silencers, but all employ this principle in one form or another

THE BRAKES

Every car carries at least two brakes of band pattern--one, usually worked by a side hand-lever, acting on the axle or hubs of the driving-wheel; the other, operated by the foot, acting on the transenerally arranged to withdraw the clutch simultaneously Tests have proved that even heavy cars can be pulled up in astonishi+ngly short distances, considering their rate of travel Trialscar and a four-in-hand coach gave 25-1/3 and 70 feet respectively for the distance in which the speed could be reduced from sixteen ards speed,journeys In fact, feats perfor the Gordon-Bennett and other races have equalled railway performances over equal distances

When we come to record speeds, we find a car, specially built for the purpose, covering a mile in less than half a minute A speed of over 120 ines of 150 hp can now be packed into a vehicle scaling less than 1-1/2 tons Even on touring cars are often found engines developing 40 to 60 hp, which force the car up steep hills at a pace nothing less than astonishi+ng In the future the motor car will revolutionize our es effected by the advent of the stea” laas abolished in the British Isles, the motor has reduced distances, opened up country districts, and generally quickened the pulses of the community in a eneration will live

_Note_--The author is much indebted to Mr Wilfrid J Lineham, M Inst

CE, for several of the illustrations which appear in the above chapter

[8] Steam-driven cars are not considered in this chapter, as their principle is much the same as that of the ordinary locomotive

[9] On so from the top of the cylinder to the tank, fro cooled, to the bottom of the cylinder

[10] For explanation of the induction coil, see p 122

Chapter V

ELECTRICAL APPARATUS

What is electricity?--Fornet--Lines of force--Electro-nets--The electric bell--The induction coil--The condenser--Transformation of current--Uses of the induction coil

WHAT IS ELECTRICITY?

Of the ultiht, we are at present ignorant But it has been clearly established that all three pheno the universe By means of suitable apparatus one form can be converted into another form The heat of fuel burnt in a boiler furnace develops ine which the boiler feeds with steaine revolves a dynaenerated can be passed through wires to produce ht Wethat electricity is energy or h the ether from molecule to ation has taught us how to produce it at will, how to harness it to our uses, and how to measure it; but not _what_ it is That question may, perhaps, rereat difficulty attending the explanation of electrical action is this--that, except in one or two cases, no coases and fluids When dealing with the stearasps the principles which govern the use of stearams show, it is hoped, quite plainly ”hoorks” But electricity is elusive, invisible; and the greatest authorities cannot say what goes on at the poles of a net or on the surface of an electrified body Even the existence of ”negative” and ”positive” electricity is problematical However, we see the effects, and we know that if one thing is done another thing happens; so that we are at least able to use terms which, while convenient, are not at present controverted by scientific progress

FORMS OF ELECTRICITY

Rub a vulcanite rod and hold one end near some tiny pieces of paper

They fly to it, stick to it for a time, and then fall off The rod was electrified--that is, its surface was affected in such a way as to be in a state ofthe electricity in suitable receivers the strain can be e accoht flash This form of electricity is known as _static_