THEORY OF OPERATION - CONTINUED
An engine driven, variable displacement pump mounted under the cab provides hydraulic flow for the steering.
Refer to Hydraulic System in the work package. The steering wheel actuates a small hydraulic pump directing oil
to the two steering cylinders which steer the front wheels. An adjustable relief valve assembly is mounted at each
side of the chassis above the front axle. Also, refer to Front Axle Assembly in this work package for location of
hydraulic cylinders at front axle.
When the steering wheel is not being turned, the oil in lines and cylinders cannot move and the front wheels stay in
position. If the side of one of the front wheels hits a obstruction (material that will not move), the positions of the
front wheels will move. The force on the side of the wheel causes an increase in the pressure of the oil in the cylin-
ders and in one of the lines to the cylinders. When the pressure of the oil in the line gets to 1,700 psi (11,721 kPa),
the relief valves opens. The high pressure oil in the line goes through the open relief valve and into the other line to
the cylinders. This lets the position of the front wheels change.
LINE TO TANK
LINE TO HEAD END OF
RIGHT CYLINDER / ROD END
OF LEFT CYLINDER
LEFT STEERING CYLINDER
OIL TO TANK
RIGHT STEERING CYLINDER
LINE TO ROD END OF RIGHT CYLINDER / HEAD
LINE FOR OIL TO
(RELIEF AND PRESSURE LINE TO LEFT
END OF LEFT CYLINDER
This system provides hydraulic oil flow to the steering if the engine fails or implement hydraulic flow is lost while
the machine is operating. The main components are the electrically driven motor/pump mounted in the engine
compartment, and a sensor mounted on the hydraulic combination valve. Refer to Hydraulic System in this work
The sensor activates the motor/pump when pressure is lost in the hydraulic system. A switch on the engine gover-
nor prevents automatic activation of the motor/pump during normal engine shutdown. A switch on the panel acti-
vates the system for testing or for use during towing.