Development of composite spherical bearing

Abstract

The conventional spherical bearing composed of a metal-race and metal-ball journal for the elevation driving mechanism (EDM) of guns has the seizure problem between the race and ball since it should support high dynamic load at low rotating speed without oil lubrication. Carbon composite materials are employed in heavy-duty bearings due to their inherent self-lubricating properties and thermal stability. In this work, a composite spherical bearing (CSB) composed of carbon composite race and steel ball is developed to solve the seizure problem of conventional metal-metal spherical bearings for the elevation driving mechanism (EDM) of a future battle tank. In order to eliminate machining and assembling processes of the composite race, it was manufactured with precise compression molding on the ball surface directly. Self-lubricating layer was formed to improve the tribological properties of the inner surface of the composite race. Also the compressive strength of the carbon composite was measured to verify the applicability of the carbon composite spherical bearing to the future battle tank. In addition, the reliability of the composite race of the EDM under dynamic load induced during firing was investigated with respect to environmental temperature and humidity changes. Finally, the bearing clearance and the friction torque of the CSB, which affected the targeting accuracy and the driving force, were measured by a pneumatic bearing tester that could simulate the ball journal oscillation under compressive bearing load.