Abstract: Bearing assembly is one of the most important and key parts in fly wheels. The value and the variation of the friction torque of the bearing assembly have direct influence on the performances of fly wheels. In this paper, the startup friction torque and the lowspeed friction torque are measured by using the developed lowspeed friction torque tester, and the theoretical analysis is also presented. The results from the experiments show that the bearing assembly with a larger startup friction torque will lead to a larger current at the working speed, but the two parameters have no strict proportional relationship. With the increasing preload, the startup friction torque of the bearing assembly increases linearly in the experimental range. With the speed increasing, there are two minimum points of the friction torque which cannot be predicted theoretically. Nevertheless, with the same speed, the friction torque of the bearing assembly under an increasing speed is larger than that under a declining speed.

Key words: bearing assembly, friction torque, elastohydrodynamic lubrication, oil film