TM 5-4310-343-35
CHAPTER 4
MAINTENANCE AND TROUBLESHOOTING
4-4. Brushes
4-6. Commutator
Inspect brushes on motor after 1,000 hours operation to
Under normal operating conditions, the commutator
determine wear factor.
Do not permit brushes to
rarely require attention. It should be kept clean and free
become worn shorter than 7/16 inch as damage to the
from dirt or oil. If it becomes slightly rough or grooved
commutator may occur. When replacing brushes, it is
due to foreign deposits, it may be polished with fine (No.
most important that they be properly "seated" to the
000) sandpaper or a commutator polishing stone. DO
contour of the commutator. Always check to make sure
NOT USE EMERY. If the defects cannot be removed in
that brushes are free to move in the brush holders and
this manner, the commutator must be turned down in a
that the brush springs have the proper tension (14-16
lathe. Refer to paragraph 5-6.4.
oz.)
4-7. Bearings
4-5. Brush Seating
Motor bearings should not require any maintenance
during the life of the machine, however, should a bearing
To correctly seat a brush, insert a strip of thin, fine (No.
become defective producing excessive heating,
000) sandpaper, approximately 1 x 12 inches, between
vibration, or clicking noses, the bearing should be
the brush and the commutator, with the abrasive side
replaced.
Refer to paragraph 5-6.3 for method of
toward the brush. DO NOT USE EMERY. With the
replacing defective bearings.
brush in the holder and under pressure, withdraw the
sandpaper in the direction of rotation of the motor,
4-8. Control Components
keeping it close to the contour of the commutator.
Control components such as relays, timer, valves,
Release pressure on the brush before returning the
diodes, capacitors, and resistors employed in the control
sandpaper for the next stroke. Check progress of
circuits are considered non-repair items and should be
seating by running the machine several minutes at no
replaced when found defective
load, with brushes riding on the bare commutator and
observe the area of seat polished by contact. Continue
sanding until at least 80% of the area of the seat shows
contact when checked in this manner. Reseating of the
brushes is required if brush holders are moved or
replaced, or if the commutator is resurface
4-0-1
