(c) Low free speed and high current
draw indicate: tight, dirty, or worn
loose pole shoes allowing armature
to drag, shorted armature, grounded
armature or fields.
(d) Failure to operate with high current
draw indicates a direct ground in the
terminal or fields.
(e) Failure to operate with no current
draw indicates an open field circuit,
broken brush springs, worn brushes,
commutator bars or other causes
which would prevent good contact
(f) Low no-load speed and low current
draw indicate a high internal
defective leads, dirty commutator
and causes listed under (e).
(g) High free speed and high current
draw indicate shorted fields.
(3) Lock-Torque Test (fig. 7). The lock-
torque test requires the equipment
high current capacity should be used.
The cranking motor should be securely
Figure 7. Lock torque test
mounted and a brake arm hooked to the
(1) The drive, armature and field should not
When specified current is applied, the
be cleaned in any degreasing tank, or with
torque can be computed from the reading
grease dissolving solvents, since these
on the scale. A one foot brake arm will
would dissolve the lubricant in the drive
directly indicate feetpound. If the torque
and damage the insulation in the armature
is low, the motor must be disassembled
and field coils. All parts except the drive
for further tests and repair.
should be cleaned with oleum spirits and
a brush. The drive can be wiped with a
(1) Scribe marks across drive housing, lever
housing, frame and end bell to facilitate
(2) If the commutator is dirty it may be
reassembly in the correct relationship.
cleaned with No. 00 sandpaper.
(2) Refer to figure 8 and disassemble the
Caution: NEVER USE EMERY CLOTH
TO CLEAN COMMUTATOR.
f. Inspection and Repair.
(1) Inspect housings and frames for cracks
and distortion. Inspect threads in tapped
holes for damage.
Replace defective parts.