Onan UF Series Instruction Manual And Parts Catalog page 70

12 M A I N T E N A N C E
Each spring is permanently attached to a metal plate which snaps into
place, as illustrated. To replace a commutator brush, first remove the
spring by pushing the spring plate inward and away from the brush guide.
To replace a collector ring brush, first remove the spring by pulling
straight outward on the spring plate. When installing a new
brush in its guide, be sure that the "low" or shorter side of the beveled
top of the brush is toward the spring-plate side of the guide. Be sure
each brush is free in its guide. Keep the brush rig and end bell cleaned
of carbon dust, etc.
The surface of the commutator may become worn down level with the
mica insulation between the bars. If the commutator is worn smooth,
the mica between the bars may be cut down to 1/32" below the surface
without removing the rotor. Remove the end bell only, carefully tagging
or otherwise marking all leads disconnected.
Remove each spring and brush from its guide. Pull the end bell off
carefully. An undercutting tool may be fashioned from a hack saw blade
grinding the blade teeth to a thickness equal to the mica between the bars
of the commutator. Use care not to scratch the surface of any bar
while undercutting the mica. Remove any burrs formed along the edges
of the bars.
If, due to unfavorable operating conditions, the commutator or slip
rings become worn out of round, grooved, or pitted it will be necessary
to remove the armature and turn the commutator smooth in a lathe.
After turning down the commutator, undercut the mica between bars as
previously described.
BRUSH RIG "NEUTRAL" POSITION. - Each time brushes and springs
are serviced, see that the brush
rig witness mark is aligned, as illustrated.
FOR PROPER N E U T R A L POSITION
A L I G N YELLOW P A I N T OR C H I S E L
REFERENCE MARK ON BRUSH RIG
TO TOUCH EDGE OF END B E L L NEAR
BRUSH RIG MOUNTING SCREW.
BRUSH \ \ rREFERENCE
R I G — / MARK
MOUNTING
SCREW
FIG. 4 - BRUSH RIG POSITION
The position of the brush rig assembly in the generator end bell is very
important. The correct setting of the brush rig was determined at the