Evaluation of Ball-Bearing Performance in Liquid Hydrogen at DN Values to 1.6 Million

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Abstract
Experimental data were obtained in liquid hydrogen (−423 F) on two series of 40-mm-bore ball bearings utilizing various retainer materials. Effects of diametral clearance and retainer material on limiting DN value (product of bearing bore in mm and shaft speed in rpm) were investigated at thrust loads to 500 lb and at speeds to 41,200 rpm. An analysis was made to determine the effect of ball size and race curvatures on the heat generated in bearings of both series as a result of ball spin. The results, supported experimentally, indicate that higher limiting DN values at a specific thrust load could be obtained with an extremely light series (1908) bearing with open-race curvatures than with a light series (108) bearing. Successful operation to a DN value of 1.6 million was obtained with 1908 bearings (at 110 lb thrust load) using two different retainer materials. The glass-fiber-filled PTFE (polytetrafluoroethylene) retainer exhibited much less wear than the MoS2-filled phenolic retainer at these test conditions.