"It's funny
how we seem to have runs first on one kind of work and then on another,"
observed Joe Clark to Gus Wilson as the two partners prepared to close the
Model Garage for the night.
"Right now
it seems to be all electrical troubles," agreed Gus.
"Here's
another one, I'll bet two cents!" Joe muttered under his breath as a shiny,
new car pulled up in front.
The driver
of the car looked as though he had been doing strenuous work.
"The
self-starter is on the blink. Can you fix it?" he called out.
"I had to
crank it by hand to get down here. I can't see why it should go bad
all of a sudden. It worked fine up to now."
Gus didn't
ask any questions. He climbed in behind the wheel and, after testing
the lights and noting that they seemed to be working at full brilliance,
stepped on the self starter pedal. There was a clank as the starter
motor gear engaged with the teeth on the engine flywheel. The lights
immediately went out, but the starter motor appeared to be too weak to spin
the engine. Gus took his foot off the self-starter pedal, and the
lights at once returned to full power.
"Humph!" he
grunted, "I don't think there is anything the matter with the self-starter.
The trouble probably is in the battery connections.
"That's it,
all right," he continued, after he had pulled up the floor boards and
examined the clamps on the battery terminal lugs. "Look here!
This one is loose."
It was so
loose, in fact, that he was able to pull it off without touching a wrench to
the clamping bolt. Joe handed him a piece of sandpaper, and Gus
proceeded to give both the battery terminal and the clamp on the end of the
cable a good polishing.
After he
had bolted it firmly back in place, he removed the other terminal and gave
it the same treatment. "And while we are about it," he observed.
"I'm going to inspect the battery to make sure that it's getting enough
charging."
When Gus
had put the floor boards back in place, Burns the owner of the car stepped
on the starter pedal, and the starting motor spun the engine at a great
rate.
"Gosh,
that's fine!" exclaimed Burns.
"It's
simple enough when you know how, I suppose. Still, I don't see why the
lights should work when the self-starter was dead as a doornail. I
always thought that electric current either flowed if there was a circuit or
didn't flow at all if the circuit was broken. I didn't know there were
half way points."
"That
idea," Gus explained, "is responsible for a whole lot of electrical trouble
on automobiles. Electric current going through a wire is a whole lot
like water flowing through a pipe. It's a matter of pressure and
volume. In the spark plug circuit you have thousands of volts pressure
to shove a small volume of current through the resistance of a poor contact.
Conditions in the starter motor circuit are just the other way around.
The storage
battery only develops a pressure of six volts, and yet you have to push as
much as two hundred amperes through the windings of the starter motor to get
power enough to start the engine when it is cold and stiff."
Burns was
interested. "I had no idea that the self-starter took so much current.
That explains why they put in such a big cable to connect up the battery
with the starter switch and motor."
"Right,"
Gus replied. "The big cable is absolutely necessary.
"Even when
all the connections and the switch are in good condition, there is still a
chance for trouble. If the brushes that make contact with the
commutator of the starter motor get burned a bit, the extra resistance will
cut down the current enough to make the self-starter sluggish and irregular.
"The
queerest trouble I ever ran into," Gus continued, "wasn't due to anything
wrong with the wiring or the brushes, although this self-starter certainly
acted as though there was a poor connection somewhere. One time it
would spin the motor just as it ought to, and the next time it would fail to
work at all. I went over all the connections, cleaned the switch and
sandpapered the starter motor brushes. But it didn't help matters
enough to notice.
"I finally
located the trouble under the frame of the self-starter motor. You
know the current goes back to the battery by way of the frame of the car,
and bolts holding the self-starter under in place had worked loose.
The car had been at the seashore for quite a while, and the dampness had
caused rust.
Some
sandpaper cured the trouble."
"But why
didn't the current get to the frame through the self-starter pinion and the
gear on the flywheel?" asked Burns.
"Part of it
must have gone that way," Gus replied. "But there isn't much chance
for a lot of current to flow through the oily bearings of the crankshaft or
the fabric facings of the clutch plates."
"And I
suppose it couldn't get to the flywheel gear anyway on account of the oil on
the pinion and gear," added Burns.
"You're
wrong there," laughed Gus.
"The bendix
type of starter gearing that is used on so many cars now is a peculiar piece
of mechanism. It's the one moving part of the car that works better
without oil. Don't ever oil it.
"A man who
lives down the street here wouldn't believe me when I told him that, and he
smeared a lot of cup grease all over the self-starter. It worked all
right for a while, and then one chilly morning he stepped on the pedal and
the starter motor hummed at a great rate without engaging with the flywheel.
He tried
again, and the engine started.
Then it
wouldn't disengage, and the strain busted three teeth out of the flywheel
gear. He believes me now!"
"Light oil
wouldn't gum up like that when it got cold," suggested Burns.
"Why not
use that?"
"Don't do
it," Gus insisted. "Even light oil is bad because it picks up dust and
dirt, and after awhile the starter gets all gummed up."
"Well, it's
a relief to know that there's at least one part on the car that will work
best if I neglect it!" laughed Burns as he stepped on the self-starter.
END
