Determining the coefficient of rolling friction using hypocycloidal oscillations

The paper presents a method of finding the coefficient of rolling friction based on the hypo-cycloidal oscillation motion performed by a bearing ball into the race of an outer immobile bearing ring. The equation of motion of a ball oscillating on the inner surface of a cylinder is obtained assuming a linear dependence between the rolling friction torque and the normal force. The experimental device consists in an immobile metallic cylinder and a rotor made of two identical balls. The oscillations of the rotor were recorded and the angular amplitude decrease in time is found. For the steel balls a disagreement appears between theoretical and experimental results as the experimental data present a quasi-linear aspect in amplitude decrease only in the final stage of oscillations. The coefficient of rolling friction is established from the condition that the theoretical angular elongation graph must fit best the experimental data.