6-29
Copyright 2017 Cummins Inc.
Sample Alternator Runout Readings
When taking the deflection readings described,
make a diagram similar to the example shown in
Figure 6-16, where a total indicator reading of
.025in. (The highest positive value of +.010 and the
largest negative value of -.015”.) The indicator is
closer to the top and further away at the bottom.
This example indicates that the alternator bearing is
high. Since the side readings are equal, the alterna-
tor is centered side to side. To lower the alternator,
remove equal shims from under both alternator
mounting feet. To approximate the amount of shims
to remove or add:
1. Measure the distance between the center of
the alternator shaft to the point the indicator is
measuring at. (For example; a SAE 18 Disc
coupling distance is 10.7in).
2. Measure the distance from the alternator side
of the flex discs to the center of the alternator
mounting bolt, refer to Figure 6-15. (For exam-
ple; a HC6 Frame’s distance is 28.4in.)
3. Compare the distance measured in steps 1 and
2. (28.4in vs 10.7in or a 2.65 to 1 ratio.) Multiply
this ratio times one half the T.I.R. (In our exam-
ple, .025in divided by 2 is .0125in. This, times
2.65 equals .033in. Therefore, remove .033in
of shims from under both mounting feet.)
In general, the T.I.R. should not be more than .001in
for each inch of radius (center of shaft to indicator
axis). If we use our example of 10.7in, then the max-
imum T.I.R. would be .011in. This would only require
a correction of .014in from the T.I.R. of .025in. (A
reading of +.002 at the top and -.009 at the bottom
would fall within the satisfactory range.)
+.010
+.010
-.002
MEASURED AT
BOLT CIRCLE
DIAMETER
-.010
10.7 IN.
-.015
-.015
-.010
-.004
FIGURE 6-16. ANGULAR ALIGNMENT MEASUREMENT READINGS (Example)
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