(1) Remove cotterpins, pins, and two
c. Installation.
Install boom point and idler
turnbuckles from pendant wire ropes (fig. 4-21), then
sheaves by reversing steps (6) through (1) in a above.
remove cotterpins and pins from pendant wire ropes and
remove wire ropes from jib boom and strut.
4-21. Jib Boom, Strut, and Sheaves
(2) Remove capscrew, lockwasher, and
keeper rod securing strut sheave pin; remove sheave
a. Installation. When use of jib boom is required, it
pin, spacer and sheave from strut. Remove fitting and
will be installed as follows:
bushing from strut sheave pin.
(1) Build cribbing at end of cribbed jib boom
Note
Do not remove bearings from
boom.
sheaves unless replacement is
(2) Lower hook block to ground, remove two
required.
clamps (fig. 4-20) from hoist cable, remove hook block,
(3) Remove four cotterpins from two strut
then wind hoist cable onto drum.
pins, remove pins, then remove strut from jib boom.
(3) Lower crane boom (para 2-12b) to rest on
(4) Remove three nuts and lockwashers from
cribbing (fig. 4-19).
two capscrews and bolt, remove bolt and capscrews,
(4) Move jib boom into position over crane
then remove sheave guard.
boom point and install jib to boom point pin (fig.
(5) Remove nut, lockwasher, capscrew, and
keeper rod securing jib boom point sheave shaft,
and capscrew.
remove shaft, spacer, and sheave. Remove fitting and
(5) Install strut on jib boom, install two strut
bushing from sheave shaft.
pins, and secure pins with four cotterpins.
Note.
(6) Position pendant wire ropes at strut, install
Do not remove bearings unless
pins through sockets and secure with cotterpins.
replacement is required.
(7) Connect wire ropes to jib boom point,
(6) Reassemble by reversing procedure of
install pins and secure pins with cotterpins.
steps (5) through (1) above.
(8) Connect longer wire ropes to eyebolt of
d. Cleaning, Inspection and Repair.
turnbuckle, connect turnbuckle to crane boom foot,
(1) Clean all parts with an approved cleaning
install pins and secure with cotter pins.
solvent and dry thoroughly.
(9) Refer to figure 2-7 and reeve crane hook
(2) Visually inspect jib boom for cracks,
block and jib boom hoist cables.
breaks, or bent sections. Inspect sheave pins and
(10) Raise boom (para 2-12b).
shafts for excessive wear. Inspect mounting hardware
b. Removal of Jib Boom.
for stripped threads or elongated holes.
(1) Move crane-shovel unit into position for
(3) Repair breaks and cracks by welding,
placement of jib boom, then build cribbing (fig. 4-19).
straighten all bends, and replace all worn, damaged, or
defective parts.
(2) Lower jib boom weighted hook to ground,
remove clamps, then cable from weighted hook. Wind
cable onto hoist drum.
4-22. Boom Backstop
Note.
If crane boom is to be removed,
a. Removal and Installation.
remove hook block in a manner
(1) If necessary, raise boom (para 2-12b) to a
similar to (2) above, winding cable
moderate angle and take pressure off mounting
onto digging drum.
hardware; remove four nuts, lockwashers, and
(3) Lower boom (para 2-12b) until jib boom
capscrews (fig. 4-22) then lift tow bearings from gantry.
rests on prepared cribbing, then disconnect two pendant
(2) Lower boom to a horizontal position with
wire rope turnbuckles from crane boom foot.
cribbing at boom point (fig. 2-46).
(4) Remove capscrew, lockwasher, and
(3) Remove two cotterpins from pin securing
keeper rod securing jib boom point pin, then remove pin.
bearing (fig. 4-22) at boom; drive pin from bearing, then
Note.
remove boom backstop.
If crane boom is to be removed,
(4) Install in reverse order.
proceed as directed in paragraph 4-2.
b. Disassembly and Reassembly.
(5) Move crane-shovel unit away from
(1) Slide bottom bearing, spring, seat, and
cribbed jib boom.
pipe as an assembly (fig. 4-22) off of two pipes
c. Disassembly and Reassembly.
connected to upper bearing; unscrew two pipes
4-20
