HOIST
NBT40 SERVICE MANUAL
5-12
Published 8-01-2017 Control # 287-11
Brake
Refer to Figure 5-10 and the Hoist Parts List on page 5-10
for the following brake service steps.
1.
Evenly remove the four capscrews (Item 11) holding the
brake cover (Item 20) in place. Spring pressure will raise
the cover as the capscrews are loosened. Remove the
cover from the brake housing.
2.
Remove the springs (Item 24) from the piston and check
the free height. Each spring should measure at least
1.200 inches with no force on them.
3.
Remove the brake piston (Item 10) by installing two
pieces of 3/8"-16NC all-thread in the bottom of two
spring pockets. Using jam nuts, screw the all-thread
pieces in evenly until the piston is clear of the housing.
An alternate way of removing the piston is to use a
portable power unit or shop air to slowly pressurize the
brake cavity until the piston is out of the bore. 4. Remove
the brake driver/clutch assembly (Items 13, 14, 15, 17,
34, and 38) from the brake housing (Item 21).
4.
Remove the brake driver/clutch assembly (Items 13, 14,
15, 17, 34, and 38) from the brake housing (Item 21).
5.
Remove the stator plates (Item 19) and friction discs
(Item 18) from the brake housing and check them for
excessive wear, then replace if necessary. Additionally,
check the top stator plate for scoring caused by the
removal tools and polish if necessary. Friction discs
should measure no less than 0.055 inches thick and
stator plates should measure no less than 0.064 inches
thick.
6.
If necessary, with a hook wire or pry bar, remove the seal
(Item 7-7) from the brake housing.
7.
Examine the bushing (Item 39) in the brake housing for
wear and, if worn, replace it.
8.
If the brake housing (Item 21) is removed from the hoist,
examine the journal on the brake housing where the seal
(Item 7-6) runs for wear. If severely worn, replace the
brake housing.
9.
Carefully disassemble the brake driver/clutch and note
the side in which the markings on the clutch (Item 34)
are facing. The clutch assembly must be re-assembled
with the markings facing the proper direction in order for
the hoist to function properly. Inspect the surface on the
input and brake drivers (Items 13 & 38) where the clutch
(Item 34) runs. If there is any pitting or spalling on the
drivers then both it and the clutch must be replaced.
10.
Re-assemble the driver/clutch assembly, making sure
that the clutch is installed properly.
11.
Install a new seal (Item 7-7) into the brake housing. If the
brake housing is removed from the hoist, temporarily
install the input sun gear (Item 38) into the brake
housing and slide the driver/clutch assembly onto the
sun gear spline.
12.
Install the stator plates (Item 19) and friction discs (Item
18) into the brake housing starting with a stator and
alternating friction discs and stator plates. There is one
more stator plate than friction disc so you will finish with
a stator plate.
13.
After installation, check the brake stack-up to make sure
that the dimensions are within the tolerance shown in
Fig 5. If your measurement is greater than shown, either
some friction discs and stator plates have been left out,
or the friction discs are worn beyond acceptable
tolerances. If your measurement is less than shown, too
many plates or discs have been inserted or they are not
seated properly.
14.
Coat the new o-rings and backup rings (Items 7-3, 7-7,
7-8, & 7-9) with light oil and install onto the piston (Item
10). See Figure 5-11 for proper o-ring/backup ring
installation.
15.
Carefully install the piston (Item 10) into the brake
housing (Item 21) and gently tap it down until it is seated.
16.
Install the springs (Item 24) into the spring pockets of the
piston. If working in a horizontal position, coat the
bottom of each spring with chassis lube to keep it in
position.
17.
Coat the new o-ring (Item 7-3) with light oil and install it
into the groove on the brake cover (Item 20).
18.
Install the cover (Item 20) onto the brake housing (Item
21) and draw it down evenly, alternating between
opposite capscrews. Make sure that the cover is aligned
properly with the brake housing in order to correctly
orient the motor and vent/drain plugs.
19.
Check the brake release with a portable hydraulic pump.
Full release should be obtained at 225 PSI ±10%.
FIGURE 5-11
7-8
7-7
7-3
7-9
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 ...
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