The Oskaloosa herald., 1915-12-23


that il will charge at seven amPeres 1t
| press the contact point on the cut out
out at the start. | can slow down the
motor so that il will cut out, and then
speed up and will cut in by itself, but II
| stop the motor and start again it will
not cut in without help. ! have clean
ed both commutators with fine sand
paper and soldered all connections.
What is the cause for il not cutting in
when starting the motor after il has
been idle for some timer
From the information you give II
would seem that the mica between the
commutator bars Is a little too high.
1t is entirely proper that this should be
scraped out so as to be below the sur
face of the commutator. In other
words, it is necessary that there be
grooves between the segments OF the
commutator, first, because of the high
speed of instruments Of this type. and.
second, the copper, being softer than
the mica, which is used as an insula-
tor separating these segments. that
should the mica protrude above or
through, expanding from contact with
Oil or dampness, prevent the brushes
from making constant contact with the
segments, the efficiency will be greatly
impaired.
} The commutators and brushes of
these instruments should be examined
at least every week or ten days to find
out their condition. If the commute
tors are dirty or the mica protrudes
above the surface the condition can be
detected from the action of the genera
tor as follows:
The relay win not close and the
generator will not charge even though
the engine is speeded up to a very high
r. .. N. If, however, the engine is
speeded up until it corresponds to
car speed Of fifteen to twenty miles
per hour and then the contact points
of the relay are closed with the finger
the generator will start to charge and
the contact will remain closed. If the
engine IS now slowed down the con-
facts will open. and they will close
properly upon speeding the engine up.
However, If the engine Is stopped for
q few moments and then started IL
will be necessary to close the contact
points Of the relay with the finger be-
fore the starter will charge the bat
! terry.
In order to eliminate this condition it
is necessary to scrape out the mica
from between the cOmmutator bars
until it is below the surface by about
three sixty -fourths of an inch. No
mica should be left above the COM
mutator surface.
Before attempting to remove the
mica it Is advisable to remove the
starter generator from the car and
then withdraw the armature. A spe-
cial jig can be made for large shops or
individual repair men. This tool can
be made of a hack saw blade about
eight inches in length, one end being
ground sharp like a parting tool on
lathe or planer to the thickness of the
mica between the copper bars. The
other end should be shaped like a
hook. but having the same kind OF
point Around the center Of this tool
should be folded piece of heavy tin
wrapped with adhesive tape, making 1t
easy to handle and less Akely to break.
The mica Is removed by forcing the
sharp edges of the tool from the outer
edge of the commutator surface to the
inner edge. 1t can be finished with
the hooked edge being drawn back In
the opposite direction. Do not cut
away the copper, as this will increase
the width of the slots and give very
poor results. 1t viii be found convent
ent to place the armature in a wise
while underwriting the mica IN this
manner Do not use a sharp needle
pointed tool, as this VIII not give good
results.