nd
forth under the brushes, one at a time, with the sanded side of the
paper against the brush. This will clean the brushes and shape the
contact surfaces to fit the curve of the commutator. Brushes should be
discarded when they be come so short that they do not make good
contact with the commutator. See that the brush holders and brush
wires are all tight and clean. Watch for loose connections of wires,
as these will cause voltage loss when the generator is charging the
battery. Watch for "high mica," which means a condition in which the
insulation between the segments projects above the surface of the
commutator, due to the commutator wearing down faster than the
insulation. If this condition arises, the mica should be cut down
until it is slightly below the surface of the commutator. An old hack
saw blade makes a good tool for this purpose. A commutator may have
grooves cut in by the brushes. These grooves do no harm as long as the
brushes have become worn to the exact shape of the grooves. When the
brushes are "dressed" with sandpaper, however, they will not fit the
grooves, and the commutator should be turned down in a lathe until the
grooves are removed.

A steady low hum will be heard when the generator is in operation.
Loud or unusual noises should be investigated, however, as a bearing
may need oil, the armature may be rubbing on the field pole faces, and
so on.

Watch for overheating of the generator. If you can hold your hand on
the various parts of the generator, the temperature is safe. If the
temperature is so high that parts may be barely touched with the hand,
or if an odor of burned rubber is noticeable, the generator is being
overheated, and the load on the generator should be reduced.

Switchboard. Clean off dirt and grease occasionally. Keep switch
contacts clean and smooth. If a "cutout" is on the board, keep its
contacts smooth and clean. If the knife switch blades are hard to
move, look for cutting at the pivots. Something may be cutting into
the blades. If this is found to be the case, use a file to remove all
roughness from the parts of the pivot. See that no switches are bent
or burned.

Keep the back of the board clean and dry as well as the front. See
that all connections are tight. Keep all wires, rheostats, etc.,
perfectly clean. A coat of shellac on the wires, switch studs, etc.,
will be helpful in keeping these parts clean.

Care of Battery

Cleanliness. Keep the battery and