ON PISTONS

NZ Truth, Issue 1142, 20 October 1927, Page 13

ON PISTONS

Merits of Aluminium

The modern car and lorry engines have been designed with • view to increased speeds and efficiency, and the use of aluminium pistons has been one of the means of attaining this end. THE two outstanding advantage* ob- *■ tained in using aluminium pistons are lightness and high thermal conductivity. The advantages of smaller weight to accelerate are: (1) The engine can pick up rapidly; (2) Smooth running at all speeds, making high revolutions possible; (3) Bearing pressures are reduced and hence longer life can be obtained from the engine; (4) Connecting rods are less liable to whip; (5) Slight improvement in petrol consumption. The last three advantages are equally important in a lorry engine. Light thermal conductivity is almost as Important as lightness, for the performance of an engine depends to a large extent on the piston temperature. Aluminium it roughly eight times as good a conductor of heat as cast-iron, and an engine fitted with aluminium pistons runs cooler, with these advantages: (1) There is much less tendency to detonation; (2) Lubrication is more efficient; (3) Power is maintained, which indirectly betters the petrol consumption; (4) Less likelihood of seizure.