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This method assumed that a parallel soft foot existed. However, a large percentage
of problem feet are angular soft feet (similar to Fig 2). Correcting this type of problem
with a full shim can make the condition worse (see Fig 3). Correction should be
determined with a set of thickness gauges (feeler gauges). The result is usually a
wedge shim similar to Fig 4.
Fig 3
The laser alignment system allows you to locate the problem feet and bypass those
feet that are OK. While the hold-down bolts are individually loosened and retight-
ened, the laser system will measure the shaft to shaft position. This actually mea-
sures how much each connection affects shaft alignment. In a perfect condition,
loosening bolts should not move the shafts at all.
Two different laser methods are available to evaluate the measured movement at
the shafts. They are:
• Soft Foot
• Frame Distortion Index (FDI)
Although they evaluate the data differently, both methods give you a sense of soft
foot severity at each location. Soft Foot results are shown by the number of X's dis-
played and FDI results are shown as a numerical value.
B-2
Fig 4
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