Figure 3-13.--Cleaning commutator or collector rings.

view A). Secure the canvas with rivets, and wrap linen

Use a vacuum cleaner during the seating operation

tape over the rivets to prevent the possibility of them

to prevent dust from reaching the machine, the

coming in contact with the commutator. When the

machine windings, and the bearings. After seating all

outer layer of canvas becomes worn or dirty, remove

the brushes, blow out the machine with a power blower

it to expose a clean layer. The wiper is most effective

or completely dry compressed air, or clean thoroughly

when it is used frequently. On ship's service

with a vacuum cleaner.

generators, it may be desirable to use the wiper once

For additional information on brushes, brush

each watch. When using the wiper, exercise care to

problems, and probable causes, refer to NSTM, chapter

keep from fouling moving parts of the machine. Figure

300.

3-13, view B, shows the manner of applying the wiper

to a commutator.

Commutator Care

When the machines are secured, you can use a

toothbrush to clean out the commutator slots. You can

After being used about 2 weeks, the commutator

use a clean canvas or lint-free cloth for wiping the

of a machine should develop a uniform, glazed, dark

commutator and adjacent parts. Besides cleaning by

brown color on the places where the brushes ride. If a

wiping, periodically clean the commutator with a

nonuniform or bluish-colored surface appears,

vacuum cleaner or blow it out with clean, dry air.

improper commutation conditions are indicated.

Do not sandpaper a commutator if it is operating

Periodic inspections and proper cleaning practices

well, even if long service has developed threading,

will keep commutator and collector-ring troubles to a

grooving, pits, bum areas between bars, longitudinal

minimum.

irregularities, and so on, unless sparking is occurring

One of the most effective ways of cleaning the

or the brushes are wearing excessively. In sanding a

commutator or collector rings is to apply a canvas

commutator, use a fine grade of sandpaper (No. 0000

wiper while the machine is running. You can make the

is preferred, but in no case coarser than No. 00). You

wiper by wrapping several layers of closely woven

can use sandpapering to make emergency reduction of

canvas over the end of a strong stick between

high mica or to polish finish a commutator that has

one-fourth and three-eighths inch thick (fig. 3-13,

been stoned or turned. Attach the sandpaper to a

wooden block shaped to fit the curvature of the

commutator, and move the block slowly back and

forth across the surface of the commutator while the

machine is running at moderate speed. Rapid

movement or the use of coarse sandpaper will cause

scratches. Never use emery cloth, emery paper, or

emery stone on a commutator or collector ring since

the danger of causing electrical shorts exists.

Additional information on the care and cleaning

of the commutator can be found in NSTM, chapter 300,

"Electric Plant General."

Bearings

Bearings are designed to allow a rotating armature

or rotor to turn freely within a motor or generator

housing. The two common types of bearings found in

motors and generators are antifriction bearings and

friction bearings.

ANTIFRICTION BEARINGS.-- There are two

types of antifriction bearings--ball and roller.

Basically, both types consist of two hardened steel

rings, hardened steel rollers or balls, and separators.

The annular, ring-shaped ball bearing is the type of

Figure 3-13.--Cleaning commutator or collector rings.

3-20