Service Manual

16
Directional charge checks. (Fig 8)
Directional charge check valves are incorporated
into the charge circuit to direct the charge pump
output to the low pressure side of the drive circuit.
The oil will flow into the low pressure side to re-
place the oil lost through normal leakage. The oil in
the high pressure side closes the remaining charge
check valve so that no high pressure oil can bleed
off into the charge circuit.
Figure 8
Hydrostatic motor. (Fig 9)
On a remote hydrostatic motor type system the hy-
drostatic motors can be a simple gear type motor or
a piston type motor. When the motor is built as part
of the complete assembly like an inline or U type
system the motor is a piston type motor very simi-
lar the piston pump except that the swash plate is
usually a fixed swash plate. Being fixed the stroke
of the pistons remain constant. The motor’s speed
of rotation can not be changed except by changing
the volume of oil that it receives from the pump.
Remember that a given column of oil will cause the
motor to turn at a given speed. More oil will in-
crease the motor speed. Less oil will slow it down.
Figure 9
OVERALL OPERATION
As the engine turns the pump rotating group, the
pistons run on the swash plate which is in the neu-
tral position. (Fig 10) With the swash plate in neu-
tral there is no movement of the pistons so no oil is
being pumped.
Figure 10
As the operator moves the traction control pedal
the swash plate angle increases and the pump pis-
tons begin to displace oil. This oil is directed to the
pump section and the unit moves. (Fig 11)
Figure 11
When the operator needs to change directions the
traction pedal is moved back to the neutral position
and than moved to the reverse position. In the re-
verse position the swash plate moves in the oppo-
site direction as it did in the forward direction. In
this position the oil is pumped to the opposite side
of the motor and the unit moves in reverse. (Fig 12)
Figure 12