4
10
National Crane
Published 8-01-2017 Control # 287-11
4-3
NBT40 SERVICE MANUAL BOOM
MAINTENANCE
When tightening/loosening the first (adjustment) nuts on
cables, secure cable using the wrench flats at the front of the
cable ends to prevent cable twist. Excess twisting of cables
can cause premature failure.
Ensure boom is completely assembled and fully retracted.
1.
Mark the front of each section with a chalk line as
indicated in Figure 4-2.
2.
Extend and retract boom several times to establish
working state of cables.
3.
Extend boom so scribed lines are exposed by
approximately 12 inches.
4.
Measure the extension gaps between each boom
section and scribed line and note values.
5.
Retract boom so that the scribed lines are exposed by
approximately 6 inches.
6.
Measure the retraction gaps between each boom
section and scribed line and note values.
7.
Extend and retract the boom a few times and then
repeat measuring the extension gaps.
8.
Adjust all corresponding cables according to
instructions.
Cable Tightening Sequence
1.
Cycle boom approximately 3 m (10 ft) out and in a few
times (.75 m (2.5 ft per section). Fully retract the boom.
Tighten the 4/3/2 retract, 2/3/4 extend, 3/2/1 retract and
1/2/3 extend cables (Steps 2-5) to remove slack and
properly sequence bottoming out of boom sections.
2.
Torque 4/3/2 retract cables at front of the 2nd section to
5.42 Nm (4 ft lbs). Start with two inside cable ends
equally, then the two outside cable ends equally.
3.
Torque 2/3/4 extend cables at back of 2nd section to
30.51 Nm (22.5 ft lb) each. To reach 2/3/4 extend cables,
extend the boom out approximately 610 mm (24 in.); 115
mm (4.56 in) per section, and tighten through hole in
back of base section.
4.
Equally torque 3/2/1 retract cables at front of base
section to 4.07 Nm (3 ft lb), start with two inside cable
ends, then the two next outside cable ends, then the two
outside cable ends.
5.
Torque 1/2/3 extend cables, (rear base section) to 14.91
Nm (11 ft lb) each.
6.
Check to ensure all boom sections are bottoming out
simultaneously.
a.
If the 2nd section is bottoming out first, equally
loosen 1/2/3 extend cables, tighten 3/2/1 retract
cables, tighten 1/2/3 extend cables, and extend and
retract the boom a few feet. Torque 3/2/1 retract
cables as in step 4 and torque 1/2/3 extend cables
as in step 5. Repeat until 2nd section bottoms out
correctly.
b.
If 3rd section is bottoming out first, equally loosen 3/
2/1 retract cables, tighten 1/2/3 extend cables, and
extend and retract the boom a few feet. Torque 3/2/1
retract cables as in step 4 and torque 1/2/3 extend
cables as in step 5. Repeat until 3rd section bottoms
out correctly.
c.
If 4th section is bottoming out first, equally loosen 4/
3/2 retract cables, tighten 2/3/4 extend cables, and
extend and retract the boom a few feet. Torque 4/3/2
retract cables as in step 2 and torque 2/3/4 extend
cables as in step 3. Repeat until 4th section bottoms
out correctly.
Repeat step 6 until all sections are bottoming out
simultaneously.
7.
Repeat steps 2 through 5 using the following torques.
Torque 4/3/2 retract cables to 10.852 Nm (8 ft lb). Torque
2/3/4 extend cables to 61.01 Nm (45 ft lb) torque 3/2/1
8860-5
8860-6
FIGURE 4-2
Reference Only
Summary of Contents for National Crane NBT40 Series
Page 1: ...Service Manual National Crane NBT40 Series R e f e r e n c e O n l y ...
Page 2: ...R e f e r e n c e O n l y ...
Page 216: ...SCHEMATICS NBT40 SERVICE MANUAL 10 2 THIS PAGE BLANK R e f e r e n c e O n l y ...
Page 218: ...NBT40 SERVICE MANUAL APL 2 THIS PAGE BLANK R e f e r e n c e O n l y ...
Page 219: ...R e f e r e n c e O n l y ...
Page 220: ...R e f e r e n c e O n l y ...
