Belt Drives

Author: E.E. Kimberly

A series motor should not be connected to its load by a belt because failure of the belt would permit the motor to reach a dangerous speed. A shunt or compound motor may be used with belt drive. Where a great speed reduction is obtained by using a very small driving pulley, excessive belt tension must be avoided in any attempt to prevent intolerable slipping. Such tension may cause the adjacent motor bearing to be overloaded. Also, a pulley which is too long may allow the center of belt tension to fall too far from the motor bearing and thus cause excessive shaft deflection.

The latter difficulty may be avoided by providing an outboard bearing on the motor shaft. Because of the evils of excessive belt tension and dangerous shaft moments, a minimum diameter and a maximum width of pulley for any motor will be specified by the manufacturer on request.

The economic aspects of group drive of machinery by belts vs. individual drive will be discussed in Chapter 23.