Section E - Hydraulics
Operation Description
Transmission Motor Operation
E - 15 E - 15
9803-9450-2
Transmission Motor Operation
The basic components of the transmission motor are the
cylinder block containing eight radially positioned pistons
with attached rollers working inside a circular cam, the
distributor, shuttle valve and flushing valve. The pistons
and rollers are located in bores in the cylinder block. The
rollers bear against the convoluted inside face of the cam
so that as oil is fed under pressure to each piston in turn
the cylinder block is forced to turn.
Oil from the pump is fed into the appropriate cylinder bores
by means of the distributor plate. As the cylinder block
rotates the distributor delivers oil to the appropriate
cylinders to continue the rotating force.
The drive from the cylinder block is transferred to the
output sprocket by means of a splined drive shaft.
Loop Flushing System
The purpose of the loop flushing system allows oil from the
closed loop to be fed into the motor casing at Z during
operation for cooling of the motor components.
When there is no drive and no pressure difference in the
loop the shuttle spool Ma is held in the central position by
its springs. The diagram shows the high pressure in one
side of the loop causing the shuttle spool to move to the
left. Oil from the return port is fed from the opposite end of
the shuttle to the relief valve. When the return pressure
exceeds the pressure within the motor casing the relief
valve opens allowing the oil to flow into the casing to cool
the motor before returning to tank. When the oil flow is
reversed in the motor the shuttle spool moves in the
opposite direction.
2 Speed Operation (optional)
When the 2 speed motor is in the low speed mode it
operates as described above. When high speed is
selected the 2 speed spool Mb is pressurised and moves
to close off two galleries in the distributor. This results in oil
being supplied to only half the number of cylinders, the
others remaining idle. As the flow of oil through the motor
is the same as before the operating cylinders and pistons
work twice as fast and therefore the output shaft turns at a
faster speed.
Table 8. Key
Fig 12.
Ma Shuttle spool
Mb 2 Speed spool
Mc Hydrostatic brake
Md Relief valve
PA Pump high pressure
PB Pump low pressure
T Return to tank
X 2 Speed feed
Z Motor flush
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