race and engine side of the housing. When the crankshaft is forced toward the generator, the generator
frame must be as far away from the engine as possible without putting an end thrust on the coupling.
This arrangement provides the maximum amount of clearance required by expansion of the generator
shaft and engine crankshaft as they heat up. The armature shaft is forced toward the coupling end of the
generator before coupling to the engine.
2.19. GENERATORS AND MOTORS
Inspection and maintenance procedures are the same for generators and small motors. Both
should be protected from dust, dirt, oil fumes, smoke, and changes in temperature. Figures 2.7, 2.8, and
2.9 show cutaway views of the main generator, auxiliary generator, and traction motor.
Standard maintenance includes inspection of the following parts: engine starting contactor, field
coils and leads, armature, brushes and brush holders, commutator, insulation, generator or motor bearing
assemblies, traction motor axle bearings, and axle and pinion gears. These are discussed in the next nine
a. Remove dust from the engine starting contactor with a brush and lubricate the bearings with
a drop of oil. Never apply oil to the contact tips. While inspecting the contactor, remove the contacts to
protect them from dust, oil, and metal particles. During inspection, operate the contactor by hand.
Silver contacts may become blackened; this does not affect their operation and they should not be
b. Field coils and leads are cleaned and repainted. Cleaning the windings with liquid cleaner
destroys their protective coating and causes them to crack. They should be cleaned by a steady stream
of air and, if necessary, wiped with a dry cloth. Also clean, dip, and bake insulation. Retape and paint
field coil and brush holder connections, if necessary.
c. Pull pinions at 250,000 miles and inspect armature shaft. Clean, dip, and bake armature. A
complete rewinding of an armature consists of removing bands, cutting coil leads to commutator,
stripping coil from core, cleaning and repairing the core, repairing the commutator, inserting formed
coils, connecting coils to commutator, making a bar-to-bar circuit test, applying temporary bands,
soldering, dipping, baking, and applying permanent bands. A banding machine holds the armature in
much the same manner as a lathe,