Charge oil for the propel system is supplied by the steering
system. The steering system sends filtered charge oil to
pumps (3). Flow from the pumps is controlled by the propel
control lever on the operator console. A control cable connects
the lever to the front pump. A linkage rod connects the front
pump to the rear pump. The operator uses the propel lever to
control direction and speed of the machine. The pumps supply
oil to drum and axle drive motors (4) and (5). Case drain oil
from the motors flows through thermal bypass valve (9). Oil in
the bypass valve flows either to oil cooler (13) or back to
hydraulic oil tank (10).
The speed shift control valve sends charge oil to the drive
motors to change the motor displacement for high and low
speeds. The parking brake valve controls the flow of charge oil
to the brake in the drum drive motor.
Below Operator Platform.
(3) Tandem propel pumps.
Propel pumps (3) are located under the operator platform. The
propel pumps are variable-displacement piston pumps that
provide minimum pressure to the system when the machine is
Left Side Of Drum.
(5) Drum drive motor.
Drum drive motor (5) is located on the left side of the drum.
The motor is a variable displacement, bi-directional piston type
motor. When the machine propels it receives high pressure oil
from the front section (pump closest to the flywheel) of the
tandem propel pump. It transmits the torque through a
planetary gear reduction gearbox to the drum. Isolation
mounts are used to isolate drum vibration internal gearbox and
(4) Axle propel motor.
Axle propel motor (4) is located on the rear of the axle. The
motor is a variable-displacement, bi-directional and piston-type
motor. When the machine propels, the motor receives high-
pressure oil from the rear section of the tandem pump. The
motor transmits the torque through the axle assembly to the