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 TM 55-1925-204-12
(8) Assemble the unit on the motor in reverse
(4) Withdraw motor from adaptor plate and lower
order of disassembly.
motor to engine room deck plates.
(9) Adjust brake (b) (6) above).
d Replacement of Roller Brakes.
(1) Remove bearing caps by removing capscrews
NOTE
and lockwashers.
After unit has operated a few times, adjust
NOTE
to ON position on indicator with current
To remove the bearing on the commutator
off.
end of motor it will first be necessary to
remove the brake from the motor.
5-67. Master Switch
(2) Pull bearings from motor frame one at a time.
a. General. A master switch (controller) is located near
(3) Test bearings for roughness of rotation while
the capstan on the main deck. The switch provides five points
holding in hand. Replace defective bearings.
of acceleration for both inhaul and outhaul. An emergency
(4) Pack bearings with lubricant in accordance
stop switch is provided on the master switch to stop the motor
with LO 55-1925-204-12-4.
in an emergency by deenergizing the line contactors and the
(5) Replace bearings in motor frame in reverse
brake contactors. The emergency switch should never be
order of removal.
used for normal stopping, because it causes motor to come to
e. Replacement of Brushes.
a sudden stop and results in hard wear on the brake.
(1) To replace brushes remove the four
b. Maintenance and Adjustment.
capscrews from each of the access covers and remove cover.
(1) Keep moving parts free from corrosion.
(2) Blow loose dirt and carbon dust from motor
(2) Do not apply paint to emergency stop switch
windings and vicinity of brushes with clean, dry, low-pressure
shaft, or master control lever shaft. These controls must
air.
operate freely.
(3) Inspect brushes for freeness of movement in
CAUTION
brush holders. Replace brushes worn to one-half their original
In the event of water leaks into the switch
length.
inclosure, do not operate the equipment
(4) Inspect commutator for grooving.
If
until it has been thoroughly dried.
commutator is deeply grooved report fact to higher
(4) Inspect contacts and springs.
Replace
maintenance level.
contacts worn to one-half original thickness. Replace springs
(5) Check brush springs for proper tension.
that have lost tension.
Replace springs that have lost tension.
c. Disassembly.
(6) Replace access covers on motor frame.
(1) Remove cover from switch housing.
f. Repair of Shunt Brake.
(2) Disconnect electrical connections to switch
(1) Back off the four socket head capscrews and
mounting board.
free the housing (5) from the end plate (1),
(3) Remove mounting bolts from end of mounting
(2) Back off six setscrews and remove brake
board and lift board and switch assemblies from housing.
assembly from motor.
d. Cleaning, Inspection, and Repair.
(3) Disconnect lead wire connections from coils.
(1) Inspect the switch housing for signs of leaks.
(4) Withdraw brake assembly from motor frame.
If there is evidence of leakage through gaskets or seals,
(5) To remove rotating disc drive gear from motor
replace as required.
shaft, loosen setscrew from gear and pull gear from shaft.
(2) Inspect contacts for burning and wear. Dress
(6) Inspect coil for damaged insulation, open
excessive roughness from copper contacts with a fine file. Do
circuits, and shorts. Replace defective coils.
not file silver contacts. Replace worn contacts.
(7) Inspect brake linings for wear. Replace linings
NOTE
worn to 1/8 inch thick as follows:
When replacing contacts, replace both
(a) Drill out old rivets and remove linings.
the stationary and movable contacts.
(b) Check discs for wear, distortion, and
(3) To replace contacts and springs.
cracks. Replace defective discs.
(a) Remove cotter pin, washer, and spring (4,
(c) Position new linings and rivet securely
in place.
5-149
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