Four-Wheel Steering; Crab Steering - Manitowoc Grove 5540F Service Manual

5540F/YB5515 SERVICE MANUAL

Four-Wheel Steering

During four-wheel steering, the front wheels steer in the
direction that the steering wheel is turned, while the rear
wheels turn in the opposite direction. This mode provides an
extremely short turning radius. It allows the rear wheels to
follow the track of the front wheels, which is an advantage in
muddy or sandy conditions.
When turning to the right Figure 10-8, hydraulic oil under
pressure from the steering pump flows through the priority
flow control valve to the P port of the steering orbitrol in the
operator's compartment. When the steering wheel is turned
to the right, hydraulic fluid is directed through port R of the
steering orbitrol to port P of the steering select valve. The
steering select valve has four solenoid valves. These valves
are activated by the steering select switch in the operator's
compartment. When the steering select switch is placed in
the four-wheel steering mode solenoids C and D are
actuated. Oil passes through the porting of the valve block
and out port A to the rear axle steering cylinder. Oil is
directed to the rod end of the left steering cylinder and base
end of the right cylinder, causing the rear wheels to turn to
the left. Return oil under pressure from the rear steering
cylinders flows into Port B of the steering select valve block
and out Port T to the front steering cylinder. The left rod of
the steering cylinder extends and the right rod retracts,
turning the front wheels to the right. Return oil from the front
steering cylinder flows into port L and out of port T of the
steering orbitrol and back to tank.
GROVE

Crab Steering

During crab steering all the wheels steer in the same
direction. This mode allows the operator to move the
machine sideways. This is especially helpful in tight areas on
the job.
When turning sideways to the right Figure 10-9, hydraulic oil
under pressure from the steering pump flows through the
priority flow control valve to the P port of the steering orbitrol
in the operator's compartment. When the steering wheel is
turned to the right, hydraulic fluid is directed through port R of
the steering orbitrol into port P of the steering select valve.
The steering select valve has four solenoid valves. These
valves are activated by the steering select switch in the
operator's compartment. When the steering select switch is
placed in the crab-steering mode solenoids B and C are
actuated. Oil passes through the porting of the valve block
and out port B to the rear axle steering cylinders. Oil is
directed to the base end of the left steering cylinder and rod
end of the right cylinder, causing the rear wheels to turn to
the right. Return oil under pressure from the rear steering
cylinders flows to Port A of the steering select valve block
and out port T to the front steering cylinder. The left rod of the
steering cylinder extends and the right rod retracts, turning
the front wheels to the right. Return oil from the front steering
cylinder into port L and out of port T of the steering orbitrol
and back to tank.
Published 10-21-2010, Control# 198-04
STEERING SYSTEM
10-9
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