National Crane 1-21-2019 Control # 104-07 4-3
1400A SERVICE MANUAL BOOM MAINTENANCE
Boom Disassembly Alternative #1
NOTE: If wear pads and shims are removed, tag all shims
and wear pads for proper reinstallation.
1. From the rear of the boom, loosen the capscrews that
secure the keeper plates, the extend cable anchor, and
the retract cables in the rear of the 3
RD
section. Remove
the keeper plates.
2. Extend boom about 60 cm (24 inches).
• Remove the nuts which secure the extend cables to the
cable anchor plate.
• Tag and disconnect the hydraulic lines from the extend
cylinder.
3. Place the extend cables inside the boom and slide the
cable anchor plate out of the side of the hoist mount
(hoist removed).
4. Remove the two capscrews, lockwashers, and spacers
that anchor the extend cylinder rod butt plate to the rear
of the 1
ST
section.
5. Remove the two capscrews and lockwashers that
secure the spacer bar to the inside top of the front of the
1
ST
section. Remove spacer bar.
6. Remove the four capscrews that secure the wear pads
to the bottom of the 1
ST
section. Removal of side wear
pads is optional. Adequate clearance exists between
adjoining section side pads for boom disassembly. If the
side pads are removed, tag all pads, and shims for
proper reassembly.
7. Support the 2
ND
-3
RD
-4
TH
assembly at the front with an
adequate lifting device. Raise the 2
ND
-3
RD
-4
TH
assembly
inside the 1
ST
section and remove the bottom wear pads.
8. With the 2
ND
-3
RD
-4
TH
assembly supported, slide the
assembly out of the 1
ST
. Relocate the sling point on the
2
ND
-3
RD
-4
TH
assembly for proper balancing of the
assembly as it slides out of the 1
ST
section. Keep tension
on retract cables as the assembly is pulled out of the 1st
to minimize the chance of retract cable damage.
9. Place 2
ND
-3
RD
-4
TH
assembly on a suitable horizontal
surface. Take care not to pinch or crush retract cables
while lifting or supporting assembly.
10. Lift the top rear wear pads on the 2
ND
section off the cam
plates. Do not remove or loosen the capscrews holding
the cam plates to the 2
ND
section. This affects the side
clearance during reassembly.
11. Remove the four capscrews securing the rear bottom
wear pads on the 2
ND
section. This pad serves as a wear
pad and retract cable keeper under the retract sheaves.
Remove this pad to remove the retract cables from the
retract sheaves. Place the retract cable ends in a
location to minimize the possibility of damage.
12. Remove the six capscrews securing the retract sheave
pin and the retract sheaves to the 2
ND
section. Remove
the sheaves and pins.
13. Remove the two capscrews functioning as the upper
retract cable keepers. Remove the retract cables.
14. Remove the two capscrews securing lock bar to the
extend cylinder collar. This bar constrains the vertical
movement of the extend cylinder. Remove the bar.
15. Loosen capscrews retaining the extend cable anchor to
back of the 4th section.
• Remove the capscrews to dissemble the cable anchor.
• Back the capscrews out about 12 mm (0.50 inch) so that
the anchor assembly can slide back and out of the
section as the extend cylinder is removed.
16. Support extend cylinder with an appropriate lifting
device and pull the extend cylinder out of the boom while
keeping the extend cables tensioned slightly by hand to
minimize the possibility of damage to the cables. Pull
cylinder to within 91 cm (3 feet) of complete removal
from the boom sections.
17. Reach into the rear of the 4
TH
section and pull the extend
cable anchor out from its retaining pocket on the bottom
of the 4
TH
section. A slight angle applied to the anchor as
it’s being pulled to the rear permits easier removal
through the 2
ND
and 3
RD
sections.
18. Remove the extend cylinder from the boom. Do not
allow the sheaves to fall off the front end of the extend
cylinder. Remove the extend cables. Place the cylinder
and cables in suitable area to prevent possible damage.
19. Remove the two capscrews, cable guide, wear pad, and
spacer bar from the front top of the 2
ND
section.
20. Remove the four capscrews that secure the bottom pad
plate to the 2
ND
section. Slightly lift the 3
RD
section, and
remove pad plate.
21. Slide the 3
RD
section out of the 2
ND
section. Removal of
the side pads is optional. If the side pads are removed,
tag all shims, pads, and corresponding locations for
proper re-assembly.
22. Remove the two capscrews, cable guide wear pad, and
spacer bar from the front top of the 3
RD
section.
23. Remove the four capscrews attaching the bottom pad
plate to the 3
RD
section. Slightly lift fourth section, and
remove pad plate.
24. Slide the 4
TH
section out of the 2
ND
section. Removal of
the side pads is optional. If the side pads are removed,
tag all shims, pads and corresponding locations for
proper reassembly.
25. Remove all remaining capscrews and wear pads from
the sections.
Fo
r
Reference
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