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4-1
Published 9-04-2014, Control # 422-08
RT765E-2 SERVICE MANUAL
BOOM
4
GROVE
SECTION 4
BOOM
SECTION CONTENTS
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . 4-1
Boom Extension . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
Boom Retraction . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
Disassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7
Boom Nose Sheaves . . . . . . . . . . . . . . . . . . . . . . 4-9
Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10
Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13
Functional Check . . . . . . . . . . . . . . . . . . . . . . . . 4-14
Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14
Boom Alignment and Servicing. . . . . . . . . . . . . . 4-14
Cam Operated Check Valve Adjustment . . . . . . 4-15
Guide Block Adjustment . . . . . . . . . . . . . . . . . . . 4-15
Boom Extension and Retraction Cable . . . . . . . 4-16
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16
Telescope Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . 4-17
Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-17
Theory Of Operation . . . . . . . . . . . . . . . . . . . . . . 4-17
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-18
Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-20
Theory of Operation. . . . . . . . . . . . . . . . . . . . . . . 4-20
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-20
Lift Cylinder Removal. . . . . . . . . . . . . . . . . . . . . . 4-22
Disassembly and Assembly. . . . . . . . . . . . . . . . . 4-22
Lift Cylinder Installation . . . . . . . . . . . . . . . . . . . . 4-22
Swingaway Boom Extension . . . . . . . . . . . . . . . . 4-24
Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24
Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-32
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-32
DESCRIPTION
A four section 35.6 to 110 ft (11 to 33.5 m), full power,
sequenced, and synchronized boom (Figure 4-1) is installed
on this crane.
The boom utilizes two telescope cylinders to extend and
retract the inner mid and outer mid sections with a
synchronized cable system to extend and retract the fly
section. The telescoping sections are supported on graphite
impregnated nylatron wear pads. Side wear pads prevent
metal to metal contact between the sections.
Boom assembly lift is provided by one lift cylinder. Boom
elevation is from -3 to 78 degrees.
An optional auxiliary boom nose (rooster sheave) is available
for the boom to simplify single part cable usage. The rooster
sheave is installed on the main boom nose and is secured by
pins that pass through the rooster sheave and main boom
nose.
A 10.1 m (33 ft) fixed offsetable or a 33 to 56 ft (10.1 to 17.07
m) folding offsetable swingaway boom extension is provided
to obtain additional boom reach. Optional inserts are
available for additional reach.
The Bi-fold boom extension mounts directly to the boom
nose utilizing a four point attachment. In addition, the bi-fold
extension base section and/or fly section can be stowed on
the right side of the boom base section.
THEORY OF OPERATION
Boom Extension
Boom extension and retraction is accomplished with two
telescope cylinders, four extension cables, and two
retraction cables. The lower telescope cylinder rod is
secured to the rear of the boom base section and the barrel
is secured to the inner mid boom section by a trunnion. The
upper telescope cylinder rod is secured to the rear of the
inner mid boom section and the barrel is secured to the outer
mid boom section by a trunnion. The extension cables are
secured to the back of the fly section and run around
extension sheaves on the front of the upper telescope
cylinder to the rear of the inner mid.
The hydraulic fluid in both lower and upper telescope
cylinders is routed through the rods so that the barrels can
extend. There are two cam operated check valves which
control flow to the telescope cylinders. With both cylinders
retracted, the check valve for the lower telescope cylinder is
open and the check valve for the upper cylinder is closed
Reference Only