3. Applications of Friction in Machines: Journal Bearings A journal bearing supplies lateral support to a rotating shaft. For example the axle on your car. The shaft will roll up the side of the bearing until it slips. It will remain at the point of slippage as long as the shaft continues to rotate with the specified moment. Notice that L and R are equal and opposite, but not collinear. We can determine the torque required to maintain rotation r f is the radius of the friction circle, a small circle to which R is tangent.