INTRODUCTION 777 SERVICE MANUAL
1-40 Published 10-01-2012, Control # 045-08
To ensure crane travel in a straight forward or reverse
direction, both crawler hydraulic drive circuits in the travel
system have pressure senders and shuttle valves. When
traveling, the PC monitors signals from pressure senders
and adjusts the displacement of the travel pumps to achieve
and maintain equal pressure in each crawler drive circuit.
This causes the crane to track in a straight and controlled
condition.
Travel Detent Button
Travel detent button, located on right crawler control handle,
allows any travel command to be locked in. This allows the
crawlers to be operated in either direction at a selected
speed without the operator’s hand being on the crawler
control handles. When travel detent button is lifted into the
dome of the handle, the PC memorizes and locks in the
travel command received from one or both crawler control
handles. When the operator releases the handle(s) back to
the off position, the PC maintains selected speed and
direction of travel.
Lifting travel detent button again or moving either control
handle in the opposite direction, opens the travel detent
circuit and returns direct control of the travel system to the
operator via actuation of the control handle(s).
This control also serves as a parking function. Lifting the
travel detent button when the crawler control handles are in
the off position, locks in the off condition (brakes applied) and
ensures the crawler control handles are inoperable until the
detent button is released.
FIGURE 1-26
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