bearings. Figure 3-15, view B, shows how to get a
rough approximation of motor or generator end-play
movement. You can correct excessive end-play, as
described in the applicable technical manual, by
adding bearing shims.
One cause of motor and generator failure is
overlubrication. Forcing too much grease into the
bearing housing seals and onto the stationary windings
and rotating parts of the machine will cause
overheating and deterioration of insulation, eventually
resulting in electrical grounds and shorts. Overheating
will also cause rapid deterioration of the grease and
the eventual destruction of a bearing. To avoid
overlubrication, add new lubricant only when
The frequency that new grease must be added
depends on the service of the machine and the
tightness of the housing seals, and the requirements
Figure 3-16.--Grease-lubricated ball bearings.
should be determined for each machine by the
engineer officer or PMS requirements. A large
One common method by which the oil level is
quantity of grease coming through the shaft extension
maintained in ball bearings is the wick-fed method. In
end of the housing usually indicates excessive leakage
this method, the oil is fed from an oil cup to the inside
inside the machine.
of the bearing housing through an absorbent wick.
To prevent greasing by unauthorized personnel,
This wick also filters the oil and prevents leakage
remove the grease cups from motors and generators.
through the cup if momentary pressure is built up
Insert pipe plugs in place of the grease cups. Replace
within the housing.
the pipe plugs temporarily with grease cups during
Grease-Lubricated Ball Bearings.-- Preferred
lubrication (fig. 3-16). (Removable grease cups
Navy bearing greases for shipboard auxiliary
should remain in the custody of the responsible
machinery are as follows:
maintenance personnel.) Make sure the grease cups
1. Bearings operating below 110C (230F) in
are clean. After the grease is added, clean the pipe
plugs before replacing them.
non-noise or noise-critical application should use
DOD-G-24508 grease. It is available in a 1-pound can.
The preferred method of adding grease calls for
2. Bearings operating near water (for example,
disassembly of the bearing housing. Although not
rudder stock bearings) should use MIL-G-24139
recommended, renewing the bearing grease without at
grease. It is available in a 5-pound can.
least partially disassembling the housing may be tried
under certain conditions.
DOUBLE-SHIELDED OR DOUBLE-SEALED
BALL BEARINGS SHOULD NEVER BE DIS-
Oil-Lubricated Ball Bearings.-- Lubrication
ASSEMBLED OR CLEANED. These bearings are
charts or special instructions are generally furnished
prelubricated. Cleaning will remove the lubricant
for electric motors and generators equipped with
from the bearings or can dilute the lubricant until it no
oil-lubricated ball bearings. The oil level inside the
longer possesses its original lubricating qualities.
bearing housing should be maintained about even with
the lowest point of the bearing inner ring. At this level,
Permanently lubricated ball bearings require no
there will be enough oil to lubricate the bearing for its
greasing. You can recognize equipment furnished
with these bearings by the absence of grease fittings
operating period, but not enough to cause churning or
or the provision for attaching grease fittings. When