3.4 FRICTION DRIVE

3.4.1 TYPES OF FRICTION DRIVES (BELT AND SHEAVE)

Adjustable While in Motion (Nonenclosed)

• These are usually sold as separate, complete pulleys, designed for mounting directly on a motor shaft. These pulleys are normally spring-loaded and may have either one or both of the disk halves capable of axial movement. They are designed to drive a fixed-diameter sheave. Output speed variation at the fixed sheave is controlled by varying the center distance between the fixed and spring-loaded sheave. This usually involves a sliding-motor mounting base. 
• Pulleys with one fixed and one movable disk may be used to drive either a flat-face or a V sheave. Note that as the pitch diameter traversed by the belt on the spring-loaded sheave changes, the center line of the belt moves axially. If a flat-faced pulley is the driven element, both motor shaft and driven shaft must be parallel, and the motor should move perpendicularly to the driven shaft.