Estimating Torque and Lining Pressure for Bendix-Type Drum Brakes

Internal shoe drum brakes of the Bendix, or servo, type have neither of their two internal shoes permanently attached to a fixed anchor pin. Both are free to shift position slightly as the direction of the drum rotation reverses, so that for either direction one shoe pivots about the fixed anchor pin and the other pivots about its end of the adjusting link between shoes. It is the absence of a fixed pivot point for the primary shoe that introduces additional complexity into the analysis of these brakes.

This paper demonstrates that with the aid of a personal computer the significant influence of lining pressure distribution upon brake performance and upon the contribution of each shoe to the braking torque can be examined.