Oil entering one of the ports subjects two gear teeth on the
sembled, inspected, and the problem corrected before
inlet side of the motor to high pressure which tends to
rotate the gears as shown in Figure 5K-6.
11. If the shaft turns properly, install the remaining cap
As the gears rotate around the motor housing, they carry
screws (13) and lockwashers (14). lighten the capscrews to
the oil that enters the inlet side of the motor to the outlet
175 foot-pounds (24.2 m-kg).
side of the motor, where the oil is returned to tank.
12. Install seal (4) in retainer (2) so that the metal race of
the seal enters the retainer first. Press the seal into the
DETERMINING MOTOR EFFICIENCY
retainer using a suitable driver which bears against the metal
The rate of tail drain leakage, from a stalled motor, is a
part of the seal.
measure of the motor's volumetric efficiency. A new
13. Coat O-ring (3) with a small amount of clean grease,
motor, having maximum practical volumetric efficiency,
and install the O-ring in its groove in retainer (2). Coat the
will have a tail drain leakage rate of approximately 3 GPM
(11.36 I/min). A drain rate of 8 GPM (30.2 I/min) repre-
lip of the seal with clean grease.
sents a volumetric efficiency of approximately 80 percent.
14. Carefully install retainer (2) over the end of the output
This is the point at which consideration should be given to
shaft. Install capscrews (1).
replacing or repairing the motor. The final decision on
whether or not to replace the motor, however, must be
based on what torque and speed you consider to be
To measure the motor tail drain leakage, proceed as follows:
This hydraulic motor is a fixed displacement, single speed
1. Disconnect the motor drain hose attached to the end of
gear type motor. The construction of the winch motor is
shown in Figure 5K-5.
2. Install a short piece of hose to the motor drain fitting,
Port connections are located in the motor body. The direc-
and insert the opposite end of the hose in a suitable con-
tion of oil flow through these ports determines the direc-
tainer having a capacity of approximately 5 gallons (18 I).
tion of shaft rotation.
Figure 5K-5. Motor (41Q7)