LIGHT ALLOY PISTONS

Manawatu Times, Volume LIV, Issue 6910, 16 May 1929, Page 10

LIGHT ALLOY PISTONS

There are many interesting phases in connection with (ho modern auto-mobile-with which the motoring public is quite unfamiliar. It has been pointed out, for instance, that the piston of an automobije engiue is one of the most active and important little parts of the car. For every mile that the average six-cylinder car runs, the pistons havo to travel more than two and one-half, .miles as they slide up and clowniu -the cylinders. Each piston momentarily, starts and stops . some G,OOO times for every mile an automobile is driven. la the earlier clays all pistons were made of cast iron, which had desirable qualities with the exception of weight. Heavy metal required heavy parts with which to operate. This in turn meant more power and greater petrol consumption in order to lift the heavy piston up and down in its constant high-speed traveliing. Bo thoughts were turned to lighter metals in an effort to reduce weight without affecting efficiency. After years of constant experimentation, a new light alloy for pistons was developed, that would greatly reduce weight, and at the same time maintain a high rate of heat conductivity which is essential to efficient motor performance. The objection to some of the earlier efforts in connect with light alloy pistons was their great epansion under heat which made neces-

sary a piston clearance that .was too extreme and therefore impractical. At this stage of experiments struts were introduced. These arc backbones or braces of special alloy steel struts which are cast in and become an integral part of tile piston permanently' anchored in place. The advantage of this will bo noted when it. is explained thaL this type of design scientifically controls expansion and contraction. In other words, the modern light alloy steel backbone piston has all the advantages of the old type cast iron piston with none of its disadvantages, namely, weight.

Expansion and contraction are now so perfectly controlled that a much better tit of pistons to the cylinder walls is possible. Thus the modern motor is made 'to operate with intinitoly more efficiency, and much of the remarkable acceleration which one enjoys to-day in a motor car is duo to this new development of the light alloy piston.