Abstract: A piston comprises a crown (10) and a ring band (11) carried on two gudgeon pin bosses (12a, 12b) by two supports (20). There are upper and lower pairs of struts (21a, 21b, 21c, 21d) on each side of the gudgeon pin bosses, one strut of each pair projecting from one gudgeon pin boss and the other strut of each pair projecting from the other gudgeon pin boss. Each pair carries a respective arcuate skirt portion (22) which extends only part the way round the and is symmetrical about a plane including the piston axis (28) and normal to the gudgeon pin bore axis. There are thus axially and circumferentially extending gaps (25) of constant axial width both between the upper arcuate skirt portions and the ring band between the upper arcuate skirt portions and the lower arcuate skirt portions. This provides a lightweight piston which is very conformable and can be fitted tightly in an associated cylinder or liner to reduce noise.

Abstract: A cast light metal piston has a plurality of longitudinally extending reinforcing members. These reinforcing members may be disposed at predetermined positions in the piston as cast and are designed to impart a compressive stress to the material of the piston in the regions where the reinforcing members are located. Conveniently, the reinforcing members may be located adjacent the opposite sides of each of a pair of gudgeon pin holes provided in the skirt of the piston.