Influence of the cage on the friction torque in low loaded thrust ball bearings operating in lubricated conditions

•A complex analytical model to evaluate the friction torque in a small thrust ball bearing with three balls mounted in a standard steel cage in the presence of the lubricant and loaded with a very low axial force.•Was evaluated experimentally the differences between total friction torques for the thrust ball bearing with three balls mounted in cage and total friction torques for the same thrust ball bearing with three balls but without cage. The differences in total friction torques for rotational speed between 60 and 240 rpm were correlated with the analytical model.•Has been evidenced that for very low loads the frictions between cage and balls have important contribution to the total friction torque and quantitative results were obtained.

The authors investigated analytically, and experimentally the friction torque in a modified 51100 thrust ball bearing. The operating tests and modeling were made at very low axial load in lubricated conditions by using only three balls and a standard steel cage. Two analytical friction moments in the ball-cage contacts based on the friction in the hydrodynamic lubricant film, were developed. An analytical methodology to evaluate the film thickness in the ball - cage contacts was developed, as well. The experiments were conducted by using spin-down method for two viscosities and for rotational speeds between 60 and 240 rpm. Both experiments (with three balls without cage, and three balls mounted in the cage) have been made to validate the proposed models.