Report of the Automobile Research Committee on Contraction of Aluminium Alloy Bearings

Abstract

The nature and the causes of contraction of aluminium alloy bearings have been investigated. Previous test results indicated that contraction is due to plastic straining of the bearing material. This is confirmed by calculation of the stresses set up in the bearing alloy, which are caused by the interference fit between bearing and housing and the differential thermal expansion of aluminium alloy and steel.The variables affecting bearing contraction are then considered under the headings:—( a) Strength of material; ( b) interference fit; ( c) bearing wall thickness; ( d) bearing size; ( e) connecting-rod wall thickness. Finally, the effect of temperature upon bearing clearance is considered.The results show that contraction can be prevented by a suitable choice of the bearing material and control of the dimensions. In particular, the interference fit should be kept low, and an alloy should be used which has a relatively high elastic limit in compression.The application of the results may be extended to light alloy bearings in general and for both bush type and split bearings fitted in steel housings.