2 self energizing brakes

AUTOMOBILE

1. SELF-ENERGIZING BRAKES

2. All modern hydraulic wheel brakes of the drum type have a 'self-energizing" or 'servo' feature in which the force of the rotating drum is utilized to increase the brake pressure . In Figure when the vehicle is traveling forward, the drum is rotating in a counterclockwise direction. When the brakes are applied, the primary shoe at the left tends to move in the direc­tion of the drum rotation, because of the friction of the rotating drum . working

3. Since the primary shoe is linked to the secondary shoe at the bottom the secondary shoe is forced around against the anchor pin at the top. The result of this wrapping action is that both shoes are forced into tighter contact with the drum and the braking pressure is more uniformly applied. When the brakes are applied while the car is in reverse, the secondary shoe tends to move in a clockwise direction against the primary shoe, forcing the latter against the anchor pin.