Laboratory Device Detecting the Magnitude of the Static Friction Coefficient of Brake Lining

Abstract

The paper describes the design of laboratory equipment, which was created for verification and determination of the value of the static coefficient of friction in the contact surfaces of the brake lining and the brake drum of the drum brake with external shoes by experimental procedure. Suppliers of brake linings state the values of the friction coefficients which correspond to different operating temperatures, but do not state the values of the friction coefficient of the respective brake lining with regard to the state of contamination of the contact surfaces. In practice, the brake contact surfaces are exposed to moisture, dust, lubricants and oils; these weather and operational influences significantly affect the value of the coefficient of friction. The results of the laboratory tests performed with two types of brake linings (commonly used in practice) (fabric, hardened rubber) show that the coefficient of friction of a given brake lining is strongly influenced by the state of contamination of the contact surfaces.