Manitowoc National Crane NBT40 Series Service Manual

6
National Crane Published 8-01-2017 Control # 287-11 6-11
NBT40 SERVICE MANUAL SWING
Outer Race Torquing
The outer race bolts (1, Figure 6-7) are located on top of the
bearing.
1. Extend and set the outriggers. Fully elevate the boom.
Torque eight bolts (Figure 6-5) to 470 lb-ft ±20 lb-ft
(637 Nm ±27 Nm) using the following sequence pattern;
1, 17, 9, 25, 4, 20, 12, and 28. Tools used are the socket,
multiplier, backlash adapter, necessary extensions, and
torque wrench.
2. Return to bolt 1 and torque all bolts sequentially in a
clockwise direction to 624-676 lb-ft (846-916 Nm). The
same tools are used as in step 1.
BEARING CLEARANCE
If a swing bearing exhibits the following symptoms, it may
have reached the end of its useful life.
• metal particles in the grease
• increased drive power required
• noise
• rough operation
• acceleration in the increase of normal wear in bearing
clearance
Measure the internal clearance of the swing bearing to
determine if it needs to be replaced. (Reference National
Crane Technical Support Information TSI #10)
1. Place the boom over the front and set the outriggers.
2. Put a dial indicator (2, Figure 6-8) opposite the boom on
the T-box frame (3).
3. Place the dial on the top of the turret bearing plate (1,
Figure 6-8).
4. Power the boom down onto the boom rest.
5. Set the dial indicator at zero.
6. Raise the boom about 76mm (3 in) above the boom rest.
7. Record the deflection indicated on the dial.
8. Repeat steps 4 through 7 three times and average the
readings.
9. If the average is greater than 2.2 mm (0.090 in), replace
the bearing.
10. If the average is less than 2.2 mm (0.090 in), repeat the
measurement at every 45° around the total working area
of the crane (Figure 6-9).
a. Measure the deflection at positions 2, 3, 7, and 8 for
180° rotation and positions 2 and 8 for 360° rotation.
b. Use another crane to support the end of the boom
when the boom is powered down.
c. Locate the dial indicator opposite the boom.
d. Set the dial indicator to zero.
e. Raise the boom about 76mm (3 in).
f. Record the reading on the dial indicator.
g. Repeat steps (d) through (f) three times.
h. Average the readings.
i. If the averages is greater than 2.2 mm (0.090 in) at
any position, replace the bearing.
FIGURE 6-7
1
1
3
FIGURE 6-8
2
8831
Reference Only

Manitowoc National Crane NBT40 Series Specifications

General

Brand	Manitowoc
Model	National Crane NBT40 Series
Category	Construction Equipment
Language	English