Tentative Manufacture of Carbon Brush for Electric Car Main Motor (Report II)....Fundamental test

Tests were made on stability of pitch cokes to pulverization. Investigations on shape of powder; effect of binder on pulverizability; relation between pulverization and production process, between pulverization of particles and pressure; stability to pulverization, indicate that pitch cokes should have higher mechanical strength. Five grades of pitch cokes were selected and crushed in a hot mill to obtain the particle size distribution. It is observed that two peaks stand out in the curve; the crest of the first peak tends to shift with time toward minor particles. Converting the second peak in terms of the grade of minor particle size gives the final limit of pulverizability and observation of the shifting crest of the first peak gives the hardness of pitch coke. These are stated with theoretical explanations from a new angle.