B8 - Brakes

Abstract

This chapter focuses on the various types of brakes. There are three main types of brakes: band brakes, drum brakes, and disc brakes. A flexible steel band lined with friction material is tightened against a rotating drum. Because of its self-servo action, a band brake can be made very powerful. Positive self servo occurs when the frictional force augments the actuating force so, increasing the torque, that is, the brake has a high brake factor. Shoes or drums are lined with friction material; usually over an arc of 90–110 deg. Shoes may be leading or trailing. By suitable combination of shoes or by altering the geometry of the brake, the amount of servo required for the actuating force available and the amount of stability required can be obtained. A caliper carrying friction pads straddles the rotating disc and the pads are forced against the disc to apply the brake. The brake factor is low and equal to 2μ, but the disc brake is stable and less affected by high temperatures than the band or drum brake. The diameter of the disc and the area of friction material can be obtained from the torque curves.