B. Replace Field Winding Assembly.
with the skin. Wash thoroughly with
soap and water after exposure.
If the field winding assembly is shorted, has an
A-4.
INSPECTION.
open circuit, or has damaged insulation, remove
winding assembly and pole shoes from stator
housing. Install replacement winding assembly
A. Inspect all parts for damage or wear that would
as follows:
affect serviceability. Pay particular attention to
the items listed in the Table II Inspection.
1. Locate short scribe mark (approximately
A-5.
REPAIR OR REPLACEMENT.
1/4 inch long) on edge of stator housing
outside diameter.
Position winding
assembly in stator housing so that winding
A. Repair Armature Commutator.
with terminal (52) is on the same axis as
stud in stator housing (53). The other
If commutator of armature is rough, pitted or
three windings travel counterclockwise in
burned, repair as follows:
housing with a winding on each side of the
reference scribe line, Figure A-4. Field
1. Set armature in Vee blocks and check
terminal wires must be at scribe-line end
that runout or eccentricity of armature
of housing. Assemble pole shoes to
body does not exceed 0.002 inch.
windings and mount on a tight fitting arbor
Replace armature if over limits.
If
to insure keeping bore smooth while
commutator runout exceeds 0.005 inch, or
tightening pole shoe screws. Draw pole
if commutator is rough, pitted or burned,
shoe screws tight. Torque 75-85 inch
turn as described in next step. Otherwise,
pounds. A 2.992 inch diameter gauge
lightly sand commutator with 000 grade
must pass through I.D. of shoes.
flint paper. Blow flint particles out with
dry, compressed air at not over 40 psi.
2. Use solder of 2.5 percent silver and 97.5
CAUTION
percent lead to attach terminals (50) and
(52).
Never use coarse sandpaper or emery
3. Ground test using 500 volts AC.
cloth as these will leave a rough surface
which reduces brush life.
4. Impregnate
stator
assembly
using
Schenectady Isonel No.
31 varnish,
2. To turn commutator, mount in centers on
Military Specification MIL-V-1137A, Grade
an armature lathe and take minimum cut
BC,
Type
M,
manufactured
by
to obtain 90 percent clean copper surface.
Schenectady
Chemicals,
Inc.,
Do not remove any metal from face of
Schenectady, New York, or equivalent,
commutator riser. After turning, undercut
maintained at a temperature of 110 F
mica 0.031 inch deep by 0.025 inch wide.
(43.3 C). Impregnate as follows:
Break edges of commutator bar to
remove burrs and polish smooth. Clean
a. Place stator in a hot air oven and
as described under cleaning.
bring stator to a temperature of 290
Note
- 330 F (143.3 - 165.6 C).
b. Immediately dip into varnish (lead
Deepest pits need not be removed
end up) for a period of 10-14
provided such pits are not concentrated
seconds considered from time the
in one area and do not have sharp or
lower part of stator enters varnish to
high edges. If after turning commutator
time lower part of stator leaves
diameter measures less than 1.880
varnish. Maintain a uniform rate of
inches, armature must be replaced.
immersion and withdrawal.
A-4
