Machinery's Handbook, 31st Edition
2734 SHAFT ALIGNMENT 3rd Arrangement.— Place rim and face indicators as shown in Fig. 3a.
r
f
A
A f B A f C
2 2 ! ! # ! ! #
F r R r
= + − = + −
F
R
B
C
Fig. 3a. Dial Indicator Arrangement 3
-
+
O
+
+
+
-
+
O
o
O
O
-
+
O
-
-
-
Fig. 3b. Interpreting Dial Indicator Readings for Indicator Arrangement 3 Solid lines represent the desired location for the dashed lines (movable unit). The plus, minus, and zero readings on the indicators are represented by one of these nine scenarios. Depending on the magnitude of the variables, the generic graph gives a mental picture of what the formulas should yield. Example: Calculate the shims necessary for a pump and motor alignment where dimen sions are A = 4.25 inches, B = 8.875 inches, and C = 28.75 inches. The two indicators read r = plus (+)0.042 inch and f = minus ( − ) 0.036 inch respectively. Solution: Only the lower left block in Fig. 3b corresponds to a negative face reading and a positive rim reading. The diagram indicates that shims will be required under both front and rear feet. The required shim thickness for front and rear feet is calculated as follows:
A f B
A f C
! ! #
! ! #
F r
R r
. 2 = + − = 2 0042 = + =
. 2 = + − = 2 0042 = + =
. 425 0036 8875 . . #
. 425 0036 2875 . . #
+ − −
+ − −
. . 0021 0244 0265 . inch
. . 0021 0075 0096 . inch
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