Page 215 - Machinery Component Maintenance

Machinery Alignment 197

of completeness. Graphical methods, as shown later, are easier and
faster. In particular, the alignment plotting board should be judged ex-
tremely useful. Readers who are not interested in the mathematical
method may wish to skip to page 192, where the much easier graphical
methods are explained. But, in any event, here is the full mathematical
treatment.
In our first example, we will reuse the data already given in our setup
No. 1 data sheet.
First, we will solve for vertical corrections:
Using Nelson’s method, we found it necessary to make a 0.053 in.
shim correction. Let us arbitrarily say this will be a shim addition be-
neath the inboard feet. At the coupling face, we then get a rise of:
(:) (.053) = .069 in.

Since we were already .0055 in. too high here, this puts us

.069 in. + .0055 in. = .0745 in.

too high. Therefore, subtract .0745 in. (call it .075 in.) at all feet. Thus
our net shim change will be:

Inboard feet: .053 in. - .075 in. = .022 in. shim removal
Outboard feet: .075 in. shim removal

For the horizontal corrections, we proceed similarly:
30
(.014) X - = .lo5 in. Outboard (west) feet must move north,
4 inboard (east) feet must move south,
or a combination of the two, for
angular alignment.

Let us say the outboard feet move north 0.105 in. This makes the cou-
pling face move south, pivoting about the inboard feet:

9
- (.lO5) = .0315 in.
30

Sincc it was already .0145 in. too far north, it is now:

,0315 - .0145 = .0170 in.