jcb JS 200 Series, Service Manual

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3 - 1
Section F
Transmission
9803/6400
Section F
3 - 1
Issue 1
Motor/Gearbox
Operation
Traction Motor Assembly
The traction motor assembly consists of a counter balance valve, cross-over relief valve, 2-speed switch mechanism, swash
plate-type axial piston motor with parking brake function and the gearbox.
The piston motor converts the liquid energy of the pressurised oil sent from the hydraulic pump to mechanical energy and
transmits high speed low torque power to the reduction gear. The gearbox converts this to low speed high torque power and
transmits it to the crawler.
Its characteristics are:-
a. The parking brake is self-contained and when the motor stops, the mechanical brake works.
b. The motor is designed to be small, light-weight and compact and is contained within the gearbox.
c.
The counter balance valve and the cross-over valve make-up the braking system.
d. The counter balance valve controls motor speed in relation to the supply amount and prevents motor runaway.
e. The cross-over valve alleviates the shock at starting and stopping times and gives good feeling performance.
f. It is possible to change the motor speed to high and low by the 2-speed switch valve.
g. It is possible to automatically select the motor speed according to the motor load by the automatic 2-speed function.