Page 276 - Machinery Component Maintenance

258 Machinery Component Maintenance and Repair

Centrifugal Balancing Machines

Two types of centrifugal balancing machines are in general use today,
soft-bearing and hard-bearing machines.

Soft-bearing Balancing Machines

The soft-bearing balancing machine derives its name from the fact that
it supports the rotor to be balanced on bearings which are very flexibly
suspended, permitting the rotor to vibrate freely in at least one direction,
usually the horizontal, perpendicular to the rotor shaft axis (see also Fig-
ure 16-15). Resonance of rotor and bearing system occurs at one half or
less of the lowest balancing speed so that, by the time balancing speed is
reached, the angle of lag and the vibration amplitude have stabilized and
can be measured with reasonable certainty (see also Figure 6-16A).

W
0 3
t
2

Figure 6-15. Motion of unbalanced rotor and bearings in flexible-bearing, centrifugal bal-
ancing machines.