This chapter discusses the design procedures for pinion and gear, rack and pinion, belt and pulley, chain and sprocket, and bevel gear transmission systems. Several examples are given to make the procedures clear. The power transmission systems are common in mechanical drive applications. Power is generated from an engine, a motor, or a windmill. The power is then transmitted to a mechanism to perform some function. Transmission is generally through the use of elements such as gears, pulleys, and chains. The Toolbox offers quite a number of design tools for bearings, bolts and screws, jig bushings, keys, nuts, O-rings, and power transmission elements. These design tools assist the design engineer performs his/her work more effectively and efficiently. Power transmission is achieved by specially designed belts and pulleys. The demands on a belt drive transmission system are large, and this has led to many variations on the theme.