Adjustable Pitch Sheaves are used frequently in air handlers. These allow the design engineer to increase or decrease the speed of the driven machine. In doing so, these allow for changes in amp draw of the motor, to maximize efficiency, increase or decrease static pressure and air flow. Also, these sheaves allow for mechanical drive speed variation that is economical, easy to install, and easy to adjust. Using Adjustable Pitch Sheaves design can also help reduce zone air flow without relying on inefficient dampers, which restrict the air flow.