Page 300 - Machinery Component Maintenance

282 Machinery Component Maintenance and Repair

Rotor
4 I /

Figure 6-26. Rotor held on arbor with clamping nut.

eccentricity of the rotor mounting surface to the arbor axis and/or loose-
ness in the fit of the rotor on the arbor causes balance errors.
To determine the balance error U (Le., unbalance) caused by eccentric-
ity e of the rotor mounting surface (and by rotor clearance), use the fol-
lowing formula:

U(g in) = W(g) e(inches)

Where:

W = Weight of rotor (grams)
e = eccentricity (inches) (= 1/2 Total indicator runout (TIR) of
rotor mounting surface relative to arbor axis, plus 1/2 clear-
ance between rotor and arbor)
U(1-4) = Unbalance (gram - inches) caused by eccentric rotor mount-
ing surface and/or rotodarbor fit clearance.