Brake Shoe and Pad Fundamentals
Brake Shoe and Pad Fundamentals 28.4.1. Brake Shoe Self Energization The drum type brake consists of two internal semicircular shoes, which are lined with friction material matching to the internal rubbing face of the drum. The shoes are fitted on a back plate, also known as a torque plate, between a pivot anchor or wedge type abutment at the lower shoe end and at the upper shoe top end by either a cam or hydraulic piston type expander. In Fig. 28.9 the expander is simply represented by two opposing arrows and the shoe linings by two small segmental blocks in the mid region of the shoes. During clockwise rotation of the drum, the upper tips of the shoes are pushed apart by the expander force, Fe, and a normal inward reaction force, N, provided by the drum, resists any shoe expansion. Consequently the drum slid over the shoe linings and a tangential frictional force Ft = \iN is produced between each pair of rubbing surfaces. The friction force or drag on the right hand shoe (Fig. 28.9)