TABLE OF CONTENTS The purpose of the braking system is to slow down or stop the vehicle and, when the vehicle is stationary, to hold the vehicle in the chosen position. When a vehicle is moving it contains energy of motion (kinetic energy) and the function of the braking system is to convert this kinetic energy into heat energy. It does so through the friction at the brake linings and the brake drum, or the brake pads and the disc.
Some large vehicles are fitted with secondary braking systems that are known as retarders. Examples of retarders are exhaust brakes and electric brakes. In all cases, the factor that ultimately determines how much braking can be applied is the grip of the tyres on the driving surface.
Two basic types of friction brakes are in common use on vehicles; these are:
the drum brake
the disc brake
Figure 7.1 shows a drum brake as used on a large vehicle. This cut-away view shows that the linings on the shoes are pressed into contact with the inside of the drum by the action of the cam. In this case the cam is partially rotated by the action of a compressed air cylinder. The road wheel is attached to the brake drum by means of the wheel studs and nuts.
A brake of this type has a leading shoe and a trailing shoe. The leading shoe is...
