On Some Results of Impact Test on Carbon Brush for an Electric Car

Abstract

For impact strength of carbon brush, an impact testing machine can be used, that is, a loaded brush specimen is placed on the spring and impact will be given by revolution of the spring under varying conditions of impact number and brush loads.
In this way, tests have been made to decide whether failure of brush is caused by falling impact or by the force working in the direction of revolution due to frictional factor which occurs between the spring and the falling brush block and throwing the block against the brush grip.
With regard to the direction of the layer resulting from press-forming of brush material, percentage of failures is predominant in the direction of liability to scaling and tends to rise as the gap between the brush and the brush grip increases. Further, higher frictional coefficient causes higher percentage of failure; this can be proved by a test showing that there will be no failure if the friction of the brush on the revolving spring can be prevented by some device.
It can be concluded that prevention of brush failure can be assured by elimination of a layer structure, small frictional coefficient and minimum gap between the brush and the brush grip.