A bearing dynamometer has been devised and built which enables ready evaluation of bearing materials. Coefficient of friction and shaft speed are presented on an X-Y recorder. By varying the load on the bearing a family of curves may be quickly obtained yielding the basic performance characteristics of the bearing materials under actual bearing conditions. Prolonged tests can be performed during which observation of the bearing characteristics as a function of time can be studied. At present, bearings of ½-in. diameter are being studied to speeds of 2000 rpm and coefficients of friction to 0.7. These ranges are easily extended. The speed determination is made by a dc tachometer-generator. The essential element of the friction measuring system is a linear variable differential transformer acting as a transducer for the friction torque of the bearing.