10 - Clutches and Brakes

Abstract

This chapter describes the basic principles of frictional clutches and brakes, and outlines design and selection procedures for disc clutches, disc, and drum brakes. Clutches and brakes are similar devices providing frictional, magnetic or mechanical connection between two components. The objective in clutch design can be stated as maximization of a maintainable friction coefficient and minimization of wear. The chapter further discusses the design of the primary geometry for disc clutches. Two basic assumptions are used in the development of procedures for disc clutch design based upon a uniform rate of wear at the mating surfaces or a uniform pressure distribution between the mating surfaces. The equations for both of these methods are outlined. The chapter offers details about the configuration design of disc brakes and introduces the design of drum brakes, rotating clutches and brakes, and specifically the design of friction-based devices. Looking at brakes, the control system enables significant advantages over purely mechanical devices enabling the prevention of wheel lock-up during braking and as a result retain greater drivability. The detailed design of a clutch or braking system involves integration of a wide range of skills, such as bearings, shafts, splines, teeth, flywheels, castings, frictional surfaces, hydraulics, sensors, and control algorithms. Both brakes and clutchs can be purchased from specialist suppliers, or alternatively, key components such as brake pads or clutches discs can be specified and bought in from specialist suppliers and integrated into a fit-for-purpose machine design.