Lull 944E-42 Service Manual - Manual (Page 33)

3-3 944E-42
Boom
3.2 BOOM SYSTEM
3.2.1 Boom System Operation
The three section boom assembly consists of first,
second and third boom section assemblies. Boom
extension and retraction is accomplished via hydraulic
power and chain movement.
As the Extend/Retract hydraulic cylinder, which is
anchored at the rear of the second boom section and the
rear of the first boom section, begins to extend, it forces
the second boom section out of the first boom section.
The second and third boom sections are connected by
extend and retract chains. These chains are routed
around sheaves on the second boom section. As the
second boom section is forced out, the extend chain pulls
the third boom section out of the second boom section.
As hydraulic pressure is applied to the retract port on the
extend/retract cylinder, the second boom section is pulled
back into the first boom section, and retract chain pulls
the third boom section back into the second section.
This mechanical linkage formed by the chains and
supporting hardware extends and retracts the second
and third boom sections at the same rate.
The first boom section does not extend or retract, but lifts
and lowers via action of the lift/lower cylinder.
3.3 BOOM ASSEMBLY MAINTENANCE
These instructions must be completed in sequence. The
third boom section must be removed before removing the
second boom section. The third and second boom
section must be removed at one time before removing the
first boom section.
Before beginning, conduct a visual inspection of the
machine and work area, and review the task about to be
undertaken. Read, understand and follow these
instructions.
3.3.1 Third Boom Section Removal
1. Remove any attachment from the quick attach
assembly.
Note: If replacing the third section boom, remove the
quick attach from the third section. Refer to Section
3.6.1, “Quick Attach Removal.”
2. Park the machine on a hard, level surface, level the
machine, position the boom until it is extended
approximately 3 to 6 inches (76 to 152 mm), level the
boom, place the transmission control lever in
(N) NEUTRAL, engage the park brake and shut the
engine OFF.
3. At the front of the second boom section, remove the
top and side (1) wear pads. Label all parts for
installation.
4. Remove the rear boom cover.
WARNING
NEVER weld or drill the boom unless approved in
writing by the manufacturer. The structural integrity of
the boom will be impaired if subjected to any repair
involving welding or drilling.
MU0981
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MU0221
2
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