Cleaning Disassembled Parts of Pump Motor

TM 10-3930-609-35

j. Remove armature terminal, insulating washer,

f. Inspect bearing mounting surfaces on armature

internal insulator and jumper from inside front yoke.

and bearing bores in yokes for enlargement, scoring or

other damage due to bearing failure.

k. Remove capscrews and lockwashers which

g. Inspect armature for damage to conductors due

secure front yoke to motor ring and disengage front

yoke from motor ring.

to overheating. Check armature on a growler for opens

and shorts. Also check for foreign matter between

l. Remove ball bearing from front yoke.

segments of armature commutator and check

m. Remove machine screws, lockwashers, nuts

commutator for grooving and pitted segments.

and flatwashers which secure rocker plate and brush

Blackening of commutator if grooving, pitting or other

mounting ring to inside of front yoke and separate these

damage is not apparent does not impair motor

parts.

operation.

n. Remove flathead screws which secure rocker

h. Inspect brushes for excessive wear and for

plate to brush mounting ring and separate brush

security of shunts and terminals.

mounting ring, insulator and rocker plate.

o. If brushholders require replacement, remove

3-96. Repair and Replacement of Pump Motor Parts

eight screws which secure brushholders to brush

a. Replace all cracked or distorted parts and all

mounting ring to remove brushholders.

parts damaged by overheating.

p. If field coils require removal, take out eight hex

b. Repair minor thread damage with a tap or

head capscrews which secure pole pieces to inside of

thread chaser.

motor ring and withdraw pole pieces and field coil

c. Repair wrapping on field coils by rewrapping

assembly from motor ring. Separate pole pieces from

loose or damaged areas with glass fiber tape. Then

field coils.

apply electrical insulating varnish to rewrapped areas.

d. Replace brushes if worn to a length less than

3-94. Cleaning Disassembled Parts of Pump Motor

3/4 inch or if shunts, or terminals are loose or damaged.

a. Wash front yoke, rear yoke, covers, motor ring

e. Replace both ball bearings at each reassembly.

(from which field coils have been removed), pole

pieces, rocker plate; brush mounting ring, brushholders,

f. Replace armature or either yoke if bearing

bearing retainer and miscellaneous small metallic parts

mounting surfaces are damaged to extent that bearings

in SD. Dry parts with compressed air under moderate

cannot be properly installed.

pressure.

g. If commutator on armature is grooved or pitted,

b. If field coils have not been removed from motor

chuck armature in a lathe and reface commutator

ring, use compressed air to blow dust from coils, pole

segments. Do not remove more metal than is required

pieces and inside of motor ring. Clean outer surfaces

to produce a clean, bright, continuous surface on all

with cloth moistened with SD.

segments. Minimum allowable diameter of commutator

c. Use compressed air to blow dust from crevices

after turning is 2.125 inches. Maximum allowable

surface roughness of segments after turning 16

and surfaces of armature.

microinches rms. After turning, undercut insulation

between segments to a depth of 3/64 inch using a 0.025

3-95. Inspecting Parts of Pump Motor

inch wide saw. Clean all chips and slivers from between

a. Inspect front yoke, rear yoke, motor ring, rocker

segments.

plate and brush mounting ring for cracks and distortion.

b. Inspect all threaded parts and tapped holes for

3-97. Reassembly and Testing Pump Motor (fig. 3-

stripped threads or other thread damage.

17)

c. Inspect field coils for damage due to

overheating and for damage to wrapping. Also, using a

Note

resistor bridge, check that total resistance of field coils

Ball bearings are greased packed,

in series is 0.00109 10 percent ohms at 70 .

therefore, no lubrication is required

d. Check that brushes slide freely in brushholders

during assembly.

without binding or excessive looseness.

a. Insert pole piece assemblies into field coils and

e. Check brush springs for distortion and for

assemble field coils and pole piece assemblies

damage due to overheating. Also check brush springs

for proper tension after installation as described in

paragraph 3-97.

3-31