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 (b) Insert motor into fan housing and fasten
(h) Support motor and remove two
with mounting capscrews.
capscrews (5). Remove motor from fan housing.
(c) Install grease tubes and slip conduit
(i) Remove brush access covers from
and outlet box into position and make connections.
motor frame.
(d) Install key in armature shaft. and press
(j) Remove brushes from brush holders.
fan on shaft.
Disconnect electrical connections from brush holders.
(e) Lock fan in place with castellated nut
(k) Remove bearing caps from motor end-
and cotter key.
bells.
(f) Rotate fan by hand to detect binding or
(l) Bend tabs of lockwasher back and
rubbing.
remove bearing locknut.
(g) Install hood on fan and fasten with
NOTE
capscrews.
The bearing is push fit on the motor shaft
(h) Tighten nuts on all grease tubes, and
and a puller should be used to remove
install screen on bell housing.
bearing.
(6) Installation.
(m) Remove bearing from endbell.
(a) Hoist fan assembly into position on fan
(n) Remove bolts which hold commutator
foundation and fasten with mounting bolts and nuts.
endbell to motor frame and remove endbell. Remove drive
(b) Make electrical connections in outlet
endbell in same manner as commutator endbell.
box.
(o) Push armature through field frame, and
c. Replacement of START-STOP Switches.
For
motor is disassembled.
replacement of switches, refer to paragraph 5-72.
(4) Cleaning and inspection.
g.
(a) Blow accumulations of carbon dust and
5-75.
Controllers
dirt from motor windings with dry, low-pressure (10 psi) air.
a. General.
The 4-hp engineroom exhaust blower
(b) Wipe all parts with a lint free cloth
motor is controlled by a magnetic controller with automatic
moistened with cleaning solvent conforming to FED SPEC P-
starting acceleration control and manual speed control.
D-680.
Closing the START switch closes the circuit to the magnet coil
(c) Inspect bearing for roughness in
of the line contactor, which operates to close the line
rotation; replace defective bearings.
contactor. The circuit to the magnet coil is maintained, when
CAUTION
the START button is released, by an auxiliary contact on the
When inspecting bearings, rotate by hand,
line contactor. The closing of the line contacts energizes the
do not spin with compressed air.
motor through the starting resistance and closes the circuit to
(d) Inspect brushes for chipping and wear.
the coil of the accelerating contactor. The contacts of the
Replace defective brushes. (TM 55-506).
accelerating contactor close in sequence. The motion is
(e) Inspect brush holders.
Replace
delayed by a mechanical retarding mechanism, so that
defective brush holders.
resistance is shunted from the motor circuit in steps, until full
(f) Inspect motor windings for damaged
voltage is applied. The speed of the motor can be reduced by
insulation. Replace motor assembly if windings are defective.
turning the dial switch toward SLOW; this inserts resistance
(g) Inspect commutator for roughness or
into the armature circuit of the motor. When the motor is
pitting. Smooth with sandpaper. If commutator requires
running, the motor current passes through the heating
turning in a lathe, report fact to higher maintenance level.
element of an overload relay. Excessive current will cause the
(5) Assembly.
normally closed contacts of this relay to open, breaking the
(a) Assemble motor in reverse order of
circuit to the magnet coil of the line contactor and stopping the
disassembly.
motor. To start the motor after tripping from overload, the
NOTE
RESET button on the face of the controller panel must be
After motor has been assembled there
pushed.
should be approximately 1/64-inch shaft
b. Maintenance. For maintenance procedures refer to
end play. Make sure shaft turns freely by
hand.
5-161
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