Parts of a Drum Brake
Drum brake is a type of vehicle braking system that uses friction created by brake shoes which presses a rotating drum-shaped component known as brake drum. There many components to a drum brake.
The backing plate serves as the base for other parts. It is attached to the axle sleeve and act as a rigid non-rotating surface for the brake shoes, wheel cylinder and other hardware like the brake springs. The backing plate has to be strong and durable as it receives all sorts of forces from all braking operations.
The brake shoes are usually made of two pieces of sheet steel welded together. The friction material is either riveted to the lining table or attached with adhesive. The crescent-shaped piece contains holes and slots in different shapes for return springs, hold-down hardware, parking brake linkage and self-adjusting components.
The edge of the lining table generally has three notches or tabs on each side called nibs which rest against the support pads of the backing plate to which the shoes are installed. Each brake assembly has two shoes, a primary and secondary. The primary shoe is located toward the front of the vehicle and has the lining positioned differently from the secondary shoe.
The brake drum is normally made of a particular type of cast iron that is heat-conductive and wear-resistant and rotates with the wheel and axle. When a driver applies the brakes, the brake lining on the shoe pushes against the inner surface of the drum, and the resulting friction slows or stops rotation of the wheel and axle, and thus the vehicle. This friction generates substantial heat.
