A401130
E
3 - 5
Section H
9803/3280
Section H
3 - 5
Issue 1
Basic System Operation
4 Wheel Steer Machines
Electrical Operation
Three steering modes are available:
- 2 Wheel Steer (front axle)
- 4 Wheel Steer
- Crab Steer
The three modes are selected in the cab from a three
position switch
A
which operates relays in the steer mode
control unit
B
. The relays switch the energising supplies to
the solenoid operated steer mode control valve
C
. Proximity
switches on the front
D
and rear
E
axles signal when the
wheels are in the straight ahead position.
Lights
L1
,
L2
or
L3
on the instrument panel illuminate to
indicate the steer mode currently operative.
In 2 wheel steer mode only the front wheels are steered. In 4
wheel steer mode both axles are steered, giving a smaller
turning circle and so improving manoeuvrability. The crab
steer mode allows the machine to be driven diagonally into
loading/unloading positions which might otherwise be
inaccessible.
The system is prevented from changing mode until the
relevant proximity switch is energised. If, for example, the
system is set in 4 wheel steer and 2 wheel steer is then
selected, the system will stay in 4 wheel steer untill the rear
wheels are turned to the straight ahead position, thus
energising the rear axle proximity switch. The rear wheels
are then hydraulically locked in the straight ahead position.
D
B
C
A
D
E
A
B
L1
L2
L3
C
A401140
