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Reelmaster 3100−D Hydraulic System (Rev. C)
Page 4 − 11
Traction Circuits
Forward
The traction circuit of the hydraulic system consists of a
hydrostat connected in a closed loop circuit to three or-
bital vane wheel motors.
The engine drives traction pump (P3) indirectly through
pulleys and a V−belt. The traction pump is a variable dis-
placement piston pump. The traction pedal connects
through a cable to the trunnion shaft and swash plate of
the pump. With the engine running and the traction ped-
al in the neutral position, P3 supplies no flow to the
wheel motors. When the traction pedal is pressed to the
forward position, the cable from the pedal positions the
swash plate in the traction pump so oil flows out of the
lower port. Oil flow out of the lower port goes to the wheel
motors and turns them in the forward direction. Oil flow-
ing out of the wheel motors returns to upper port of the
hydrostat and is continuously pumped out of the lower
port.
The rear wheel motor has a small check valve across its
ports that allows the rear motor to over run during tight
turns in the forward direction.
The traction pump uses a small amount of hydraulic fluid
for internal lubrication. Fluid is designed to leak across
pump parts into the case drain. This leakage results in
the loss of hydraulic fluid from the closed loop circuit that
must be replenished.
The charge pump (P2) is a fixed displacement gear
pump. It is driven directly off the traction pump. The
pump replenishes the closed loop circuit with fluid from
the hydraulic tank. The charge relief valve supplies suffi-
cient head so that charge pump flow is guided to the low
pressure side of the traction circuit through one of two
check valves. Pump flow in excess of replenishment re-
quirements is relieved through the charge relief valve
back to the gear pump inlet.
Reverse
The traction circuit operates essentially the same in re-
verse as it does in forward. However, there are a few dif-
ferences in operation.
When the reverse traction pedal is depressed, the cable
from the pedal positions the swash plate in the traction
pump so oil flows out of the upper port. Oil flow out of the
upper port goes to the wheel motors and turns them in
the reverse direction. Oil flowing out of the wheel motors
returns to the lower port of the hydrostat and is continu-
ously pumped out of the upper port. Oil by−passes the
rear motor in reverse because of the check valve inside
the rear motor.
Hydraulic
System