JLG 18RS Service Manual - Manual (Page 40)

SECTION 3 - CHASSIS & TURNTABLE
3-2 – JLG Lift – 3121284
3.2 DRIVE ORIENTATION SYSTEM
The Drive Orientation System (DOS) indicates to the operator
conditions that could make the direction of movement of the
chassis different than the direction of movement of the drive/
steer control handle in the platform. The system indicates to
the operator the need to match the black and white direc-
tional arrows on the platform control panel to the arrows on
the chassis. The system consists of a proximity switch
mounted on the underside of the turntable, an indicator light
and an override switch on the platform display panel. The
proximity switch trips when the turntable is swung ± 43
degrees off center of the normal driving position (approxi-
mately when the boom is swung past a rear tire). When the
turntable is in the normal drive position with the boom
between the rear tires, no indications or interlocks are made. If
the machine is actively driving when the turntable is swung
past the switch point, the system is ignored until drive/steer is
released. When drive is activated with the boom swung past
the switch point, the DOS indicator will flash and the drive/
steer functions will be disabled. The operator must engage the
DOS override switch to enable drive/steer (High Speed drive
will remain disabled). When the DOS is enabled, the DOS indi-
cator will be illuminated continuously and a 3-second enable
timer will be started. The enable timer will continue for 3 sec-
onds after the end the last drive/steer command. If the timer
times out, the DOS override switch must be re-engaged to
enable drive/steer.
3.3 DRIVE SYSTEM
The Drive system consists of a variable displacement closed
loop pump, 4 low speed high torque orbital type motors,
directional control valves, and a series of flow dividers.
Drive Speed is controlled by a combination of engine RPM,
drive pump displacement and flow division between drive
motors (2WD / 4WD). Traction and torque are controlled
through the flow divider system. There are three drive modes
selectable at the platform control box, and the functionality of
the drive system is dependent on the position of the boom (in
or out of Transport Position. The following chart describes
how the system works in each drive mode.
Table 3-2. Drive System Mode Chart
Boom Position Drive Selection
Engine Speed when
Drive is Actuated
Drive Pump
Displacement
Flow
Dividers
Max. Speed
MPH (kph)
In Transport
2 Wheel Drive High-2500 RPM 100% Engaged 2.8 (4.5)
4 Wheel Drive Mid-1800 RPM 100% Engaged 1 (1.6)
4 Wheel Drive High-2500 RPM 100% Engaged 1.4 (2.25)
Out of Transport
4 Wheel Drive High-2500 RPM 52% Engaged 0.75 (1.2)
4 Wheel Drive Mid-1800 RPM 74% Engaged 0.75 (1.2)
4 Wheel Drive High-2500 RPM 52% Engaged 0.75 (1.2)