16-21. PISTON PUMP - REPAIR (Contd)
Example: Lets assume the depth
readings were 0.029 and 0.027
inches. Add these two figures
together and divide by two to
obtain the average (nominal
0.029 + 0.027 = 0.056
0.056/2 = 0.028 (nominal
Nominal Calculated Value -
Nominal Preload Value = Required
0.028 - 0.008 = 0.020 inches of
If calculated shim thickness is greater
than 0.020 inches, another shim must be
added to the opposite side of the yoke
to reduce total shim thickness to less
than 0.020.Shim thickness at either
pintle must not exceed 0.020 inches.
This is necessary to provide proper
O-ring compression and prevent pintle
d. Install correct shims (27).
e. Install pintle cover (29) and
cross tighten cover screws (28) to
175-185 lb. in.
Yoke (26) rotation will be stiff, but
should be loose enough to be moved by
hand (approximately 20 lb. in. torque).
This tightness/drag indicates that
bearings (31) are preloaded. If yoke
(26) cannot be moved by hand, preload
is too great and the preload adjustment
must be repeated until correct.