First Paper: Sliding Friction between Lubricated Rollers

Abstract

The design and development of a power circulating rolling contact disc machine is described. Each disc is mechanically coupled to a separately excited d.c. electrical machine whose armatures are connected electrically. When the discs develop traction, power circulates by one machine acting as a motor and the other as a generator. In this way controlled traction with a stepless variation of sliding speed can be maintained between the rolling discs. Dawson has shown that the pitting fatigue life of steel discs depends inversely upon the ratio of surface roughness to oil-film thickness. The disc machine has been used to measure the sliding friction between rolling discs under conditions similar to Dawson's fatigue tests. Large variations in surface roughness and film thickness resulted in relatively small changes in friction force. It is concluded that the effect of surface roughness and film thickness upon pitting life cannot be accounted for by changes in the friction force transmitted between the discs. The insensitivity of the observed friction to variation in the surface roughness of the discs is explained in terms of the shear behaviour of the lubricant film at high contact pressures.