The Steady-State Dynamics of Jewel Bearing with a Free Ball

A type of jewel bearing employing two sapphire cup surfaces (one fixed and the other movable) which were in contact with a free steel ball were analyzed. This arrangement reduced wear substantially as compared to conventional jewel bearings and had more degrees of freedom. The analysis of the ordinary jewel bearing was extended to the present case in order to determine the bearing steady-state motion reached asymptotically from an arbitrary starting state. Two different steady-state motions were investigated, i.e., when the ball was motionless (stationary), and when the ball attained pure rotation with reference to the frame. In the first case, there was no relative motion at the contact area with the fixed cup, and the relative motion at the contact area with the rotating cup consisted of rolling, sliding and spinning. In the second case, the relative motion at the contact area with the fixed cup consisted of rolling, sliding and spinning and the relative motion at the contact area with the rotating cup was pure rolling. The analysis was supported and validated by numerical simulation.