Screening contact materials for low speed slip ring assemblies

As part of a program to improve overall performance, a study was undertaken to evaluate forty potential replacement alloys for either the brush or ring members of a slip ring assembly. A reciprocating crossed rod technique was employed to monitor friction coefficient, electrical noise, and relative wear. Tests were performed in air and two candidate fill fluids. Initially, all the alloys were tested as potential brush replacements. These tests were run with the brush alloys riding against a hard gold electroplate (typical of the current materials). Based on these initial results, seven of the alloys were selected as potential ring replacements. Each of the candidate ring alloys was then tested against ten potential brush materials. A numeric rating system was developed which considered changes in wear, noise, and friction. A number of the candidate alloys were selected for additional longer term testing in actual slip ring hardware.