Drive Controls; Track Controls - jcb JS300 Service Manual

Track Controls

WARNING When the cab is swung around so that it is facing the track motor end of the undercarriage, the
action of the track controls is reversed. Take extra care!
The machine is fitted with hydrostatic track motors. The motors have a built-in spring-applied parking brake
which is automatically applied shortly after the pressure feed is removed from the motor. The operator is able
to control the feed to the motors by means of two pedal and lever operated valves mounted under the cab
floor. When the pedal/lever is released the valve automatically returns to the central position which removes
the motor feed. Service braking is accomplished by a counterbalance system built into the motor. The system is
designed so that the machine is stopped by the hydraulic braking when the feed is reduced/removed and then
held by the mechanical parking brake when it has stopped. The motors are of the swash plate type with two
swash angles. The angle is set by hydraulically operated pistons which can be controlled by the operator (by
means of an electrical switch). When these rams receive servo pressure, the motor swash angle is reduced,
reducing tractive effort but increasing speed for a given flow and pressure. The motors automatically shift to
the higher swash angle if the pressure rises above a threshold.
The two levers/foot pedals at the front of the cab control the travel.
The left travel lever and pedal are connected, so are the right travel lever and pedal. To control the travel either
can be used.
Each travel lever/pedal controls the track on the same side. For example the left travel lever controls the left
track when the cab faces forwards, (towards the recoil units).
Before a travel lever/pedal is moved, check if the undercarriage faces forwards or backwards.
A Left travel lever
B Right travel lever
C Right travel pedal
D Left travel pedal
Do not travel with the track motors in front, particularly on hard or rocky ground. The recoil units will not be able
to absorb the shocks and damage can be caused to the track running gear.
When the machine is not travelling, do not put your feet on the travel pedals.
Push the left and right travel levers slowly forwards, to travel forwards or pull them towards you, to travel
backwards.
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Drive Controls

Figure 50.
A B
C
D
9831/1100-2
Operation
Drive Controls
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