Nothing has such power to broaden the mind as the ability to investigate systematically and truly all that comes under thy observation in life.

Marcus Aurelius, Roman Emperor

This chapter deals with clutches and brakes, two machine elements that are very similar in function and appearance. Brakes convert mechanical energy to heat, and are widely used to bring all types of machinery to rest. Examples are the thrust pad and long-shoe, internal expanding (drum) brakes on automobiles, and external expanding and pivot shoe brakes in machinery. Clutches serve to bring one shaft to the same speed as another shaft, and are available in a wide variety of sizes. Both brakes and clutches use opposing surfaces, and rely on friction to fulfill their function. Friction causes heat generation, and it is important that brakes and clutches be designed properly to ovoid overheating. For this reason, clutches for high power applications are often operated while submerged in a fluid (wet clutches). However, thermal and material considerations are paramount for effective brake and clutch designs. The chapter begins by analyzing thrust brakes and clutches, as well as the related cone clutches. Block or short-shoe brakes introduce the concept of self-energizing brake shoes, which is further examined with drum brakes and clutches. Band brakes, pivot-shoe brakes, and slip clutches are also discussed.