Abstract: A bearing system includes backup bearings for supporting a rotating shaft upon failure of primary bearings. In the preferred embodiment, the backup bearings are rolling element bearings having their rolling elements disposed out of contact with their associated respective inner races during normal functioning of the primary bearings. Displacement detection sensors are provided for detecting displacement of the shaft upon failure of the primary bearings. Upon detection of the failure of the primary bearings, the rolling elements and inner races of the backup bearings are brought into mutual contact by axial displacement of the shaft.

Abstract: The rotatable guide wheel of a transit vehicle is supported by a vertical stationary shaft by at least one main support bearing. Upon failure of that main support bearing the guide wheel shifts position for operation with one of a sleeve bearing coupled with the shaft and a thrust bearing coupled with the shaft below the guide wheel.

Abstract: A rotary hydraulic cylinder for actuating a rotary work holder, on a machine tool. A non-rotary fluid distributor is supported on the cylinder by a bearing sleeve. The bearing surface of the sleeve has an anti-friction coating. The sleeve is rotatable within a housing and is frictionally restrained from rotation under normal operating conditions by O-rings, but can rotate in the event of bearing seizure. Sleeve rotation is sensed through a proximity switch to stop operation of the machine tool.