Wheel Brakes
Service, emergency, and parking brake systems exert their decelerating or clamping forces on the wheel brakes. Drum and disk brakes are used as wheel brakes.
a) Drum Brake
Drum brakes can generally be realised in the form of band or shoe brakes. The frictional braking force acts on the rotating brake drum in one of two ways, internally outwards or externally inwards. The conventional design consists of the internal shoe brake which generally includes two shoes in one drum.
According to the form of transfer of the clamping force and the shoe support, drum brakes are classified into different categories:
Simplex-brake
Duplex-brake
Servo-brake
Duo-Duplex-brake
Duo-Servo-brake
As far as the shoe support is concerned, one can distinguish between leading and trailing shoes. As a result of the support of the leading shoe, a self-energization of the brake effect results from the frictional force which acts around the centre of rotation of the shoe in the running direction. Correspondingly, in the trailing shoe the friction force leads to a self-attenuation since it does not act around the centre of rotation of the shoe but against the clamping force.