JLG 4017RS Service Manual - Manual (Page 58)

Boom
3-18 3614RS, 4017RS
3.9 BOOM SYSTEM - 4017RS
3.9.1 Boom System Operation
The four section boom consists of the first, second, third and
fourth assemblies with double third section extend chains, a
single fourth section extend chain, a single third and fourth
section retract chains.
As the extend/retract cylinder, which is anchored at the front
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 first, second, third and fourth boom sections are
connected by extend and retract chains. These chains are
routed around sheaves on the second and third boom
sections. As the second and third boom sections are forced
out, the extend chains pull the third and fourth boom
sections 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 the retract chains pulls
the third and fourth boom sections back into the second
boom section.
This mechanical linkage formed by the chains and
supporting hardware, extends and retracts the third and
fourth boom sections at the same rate.
The first boom section does not extend or retract, but lifts
and lowers via action of the lift cylinder.
3.10 BOOM ASSEMBLY MAINTENANCE -
4017RS
These instructions must be completed in sequence. The
second, third and fourth boom sections are removed from
the first boom section.The third and fourth boom sections
are removed from the second boom section.The fourth
boom section is removed from the third 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.The boom assembly consists of the first, second
and third section booms and supporting hardware.
Note: Before removing the boom or boom section, the carriage
or any other attachment must be removed from the quick
coupler.
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.
During service of the boom, perform the following:
1. Check wear pads. (Refer to Section 3.16.1, “Wear Pad
Inspection.”)
2. Check chain rollers.
3. Apply grease at all lubrication points (grease fittings).
(Refer to Section 2.7, “Lubrication Schedule.”)
4. Check for proper operation by operating all boom
functions through their full ranges of motion several
times.
Depending on your particular circumstance, the following
procedures explain the removal/installation of individual
boom sections or removal/installation of the complete
boom.
WARNING
NEVER weld or drill the boom unless approved in writing
by JLG. The structural integrity of the boom will be
impaired if subjected to any repair involving welding or
drilling.