A Study on Drum Brake Judder

On the basis of the dynamometer test data and the observational materials, this paper demonstrates that the drum brake judder is a kind of self-excited vibration. A theory has been developed, which holds that the occurace of the judder depends on the dynamical stability of the braking apparatus which changes from an open loop-system into a closed-loop one with braking(dry friclional action). A 7 DOF dynamical model simulating the judder has been established on the basis of the theory. Two geometrical parameters, the radius difference and the eccentricity of the drum and the shoe, were introduced so as to calculate the braking efficiency factor under different contact states between the drum and the shoes, such as the heel and toe, the crown, complete, etc., which is of vital importance in the analysis of judder.