TECH TIP: Softfoot and belt-driven motors

Soft foot can cause the base and motor to twist. PHOTO: FOTOLIA

Check for soft foot condition when installing a belt-driven motor system.

Although soft foot has little impact on the ability to align or tension the belts, it will cause the base and motor to twist, putting high tension on the frame and causing a variation in the motor airgap. The result is reduced mechanical component, including bearing life, reduced system efficiency due to increased friction losses, and vibration.

Try to rock the motor on the base. Add shim, as required, to prevent rocking. Tighten down all mounting bolts. Place a dial indicator on the base and the tip on one of the motor feet. Loosen that bolt and observe the dial indicator reading. If it’s greater than 0.001 inches, add (or subtract) shim. Repeat for each foot.

To properly evaluate worn belts and sheaves, or other defects (cracks, over- tensioned, under-tensioned), you need the diameters of the sheaves and the centre-to-centre distance between them. It doesn’t matter whether the measurements are in metric or imperial, as long as they are consistent.

Source: With permission, MotorDoc Newsetter