Gudgeon-Pin Location

Abstract

The gudgeon-pin must be located relative to the piston so that it does not rub against or damage the cylinder. Many methods of location have been used but the circlip at each end of the pinhole in the piston and the pinch bolt on the connecting-rod small end are currently the two most popular designs.

Another design which has met with much favour in the past is the use of a pad firmly fixed in each end of the pin. These pads are of suitable design and material so that, when they touch the cylinder bore, no damage is done.

Some older designs included the fastening of the pin by a setscrew in the gudgeon-pin boss or by a washer on each end of the pin joined by a tie bolt. A pin can also be located by a piston ring on the centre line of the gudgeon-pin boss.

First of all considerations is reliability, as failure of the locating means can cause very expensive damage. Cost and ease of assembly, light weight and simplicity are of importance.

The pinch bolt is a sound design but is slightly heavier than the circlip location and the pinch bolt itself requires to be locked by tab washer or other means. Circlips must be correctly designed and made to prevent heat forming under working conditions.