TM 11-6125-240-34
4-14. Replacement of Bearings
h. Before assembling rotor endbell, and housing
with the bearings, apply a thin film of high-tem-
WARNING
perature molsulphide (surfcote 1000, or equivalent,
Even if received under the proper NSN (3110-
00-689-7392), do not install bearings if they
manufactured by Hohman Plating, Dayton, Ohio,
are unsealed (unsealed bearings are those
FSCM01094) to the bearing bore. Remove any excess
type where the ball bearing can be seen).
lumps of compound.
Before pressing new bearings into place on the ar-
i. Slide the endbell gently over the bearing. Do not
mature shaft, read the following procedure thoroughly.
hammer or otherwise force this operation.
Bearings are critical items. Failure to observe this
NOTE
procedure may result in premature bearing failure and
If a bearing must be removed from the shaft
damage to the motor-generator.
for any reason, replace it with a new bearing
a. Use only bearing specified in parts list. DO NOT
even though the bearing removed is new and
SUBSTITUTE.
unused. The act of removal has a damaging
b. Rotate bearing stock. Use oldest first. The life of
effect on bearings. When replacing a bearing
bearing lubricant is 5-3/4 years from the date imprinted
which is secured with a locknut and key
washer, always use a new key washer at
on the bearing package wrapper. Do not assemble
equipment with bearings older than 3-3/4 years. Older
reassembly.
bearings should be returned to the manufacturer for
4-15. Reassembly of Generator Section
rehabilitation.
c. Each equipment having the bearings replaced
Before beginning the following reassembly procedure,
shall be marked (date) AGE CONTROLLED ITEM,
clean the parts of the generator section, if necessary, as
The date entered shall be the date code shown on the
described in paragraph 4-7.
outside of the bearing container. New equipment will
a. Connect the two lead assemblies (62) to their
be designated AGE CONTROLLED, necessitating date
respective brush holders inside the ac endbell (58),
change only.
using a flat washer (61), lockwasher (60), and screw
NOTE
(59).
The marking of AGE CONTROLLED ITEM is
b. Slide each of two capacitor assemblies (53) into a
recommended but not mandatory. If this
loop clamp (54). Assemble a flat washer (52), capacitor,
procedure is not carried out, keep a record of
clamp, and a second washer and secure to ac endbell
bearings replacement with appropriate date
with a screw (51). Tighten clamp screws to a torque of
reflected.
12 pound-inches. Capacitor terminals must be on top of
d. The work area must be neat and clean and free of
all lead terminals. Refer to figure 4-8 and make ter-
lint and abrasive or other harmful particles.
minals and lead connections as shown.
e. The bearing must not be removed from the storage
c. Attach the air duct (57) using a flat washer (56)
container until immediately before installation on the
and screw (55). Tighten air duct screw to a torque of 12
shaft. If necessary to set the bearing down temporarily y,
pound-inches.
place it on its own wrapper or on a piece of clean
d. Center a brush spring pin (35) in each brush
oilproof paper or plastic film.
holder (22). Install a setscrew (36), but do not tighten.
f. Be sure the shaft journal surface, locating
Install two brush springs (34) on each brush spring pin.
shoulder and undercut are free of dirt, roughness or
With a screwdriver, turn each brush spring pin clock-
burrs which might interfere with complete and proper
wise, to produce 18 to 22 ounces of pressure; tighten
seating of the bearing. Shaft shoulder shall not be
setscrew.
nicked, rolled or damaged.
e. Mount each of two capacitor units (28), using a re-
g. When pressing bearings onto shaft, position so
taining clamp (27) and screw (28).
that when practical the bearing markings are outward,
CAUTION
away from the shaft shoulder. Use an arbor press
Two brush holders are electrically insulated
(Greenard Model # 3) or other suitable tool for press-
by bushings, and two are grounded to the dc
ing bearings onto the shaft. Apply pressure uniformly
endbell. Be sure to install as described below
to the inner race only. Avoid any pressure to the outer
and illustrated in figure 4-7. If these parts are
race and be extremely careful not to touch the shield or
installed in the wrong location dc + will be
seal with the pressing tool. The bearing itself must not
applied directly to ground, the inverter will
be touched, as damage may occur.
not run, and system damage will result.
NOTE
f. Attach the insulated brush holders to the dc
If rotor cannot be installed into the unit in the
endbell using two bushings (33), flat washer (31) and
same day, cover the bearings with plastic film
screw (29). Note that brush holder mounting screw
or oil proof paper.
4-18
