"Want to make
a millions dollars?"
Gus Wilson,
veteran auto mechanic and half owner of the Model Garage, pulled his head
from under the hood of the car on which he was working.
"Hello, Pete,"
he said, "What's the big idea now?"
Pete Dilbow
glanced furtively about over the tops of his spectacles. "You're going
to be out of a job soon!" he announced impressively, "All these cars are
obstacles. They'll go straight to the junk pile soon as I get some of
the little details of my latest invention worked out. It's a new kind
of automobile that doesn't use gasoline. I thought since you're in
this business, maybe you'd go in with me for about a tenth share. That
would bring you at least a million and maybe ten times that much, if we're
lucky."
Gus had been
offered shares in Pete's inventions many times, but nothing had ever come of
any of them.
"Sounds
important, Pete," Gus told him. "Tell me about it."
At that Dilbow
drew out a neatly folded sheet of brown paper and spread it out in front of
Gus.
"Here,"
he explained, "is the design of a new kind of automobile. Learning how
an ordinary car works, I had a wonderful idea. Instead of using a
little motor to start the engine, I put in a motor big enough to run the
car, then I put in a big generator or dynamo and a large size storage
battery. The current from the battery runs the car and the dynamo
keeps the battery charged. What could be simple than that?"
"Sure is one
grand idea, Pete," Gus chuckled. "There's only one trouble with it.
It won't work."
"I'd like to
know why not," Dilbow demanded.
"Well," Gus
explained, "if it did work, that would be perpetual motion, and there isn't
any such thing."
"Wouldn't this
motor drive the car?" Dilbow asked.
"Wouldn't this
dynamo charge the battery?" Dilbow insisted.
"It surely
would if you kept it spinning at the right speed," Gus admitted.
"Then,"
snapped Dilbow, "what do you mean by saying the idea won't work?"
"For the
simple reason," Gus explained, "that electric energy is just like water
power or steam power or any other kind of power. It takes more power
to pump water up hill into a tank than you can get back again by letting the
water run down through a turbine.
"What do you
think would happen if you made an auto like that drawing? When you
turned on the juice, the car would start because current would flow through
the motor, but if you put in a dynamo or generator big enough to make as
much current as the motor ones. It would take more power to drive it
than the motor would produce. The car would start all right, but the
minute the generator cut in, it would stop as though you'd slammed on the
brakes."
"If that's
so," Dilbow interrupted, "then how do they get away with such small
generators on automobiles? Isn't that generator," he added, pointing
to the one in the car on which Gus had been working, "as small as the
self-starter and doesn't the self-starter motor have power enough to turn
over both the engine and the generator at the same time? And doesn't
it keep the battery charged?"
"Listen,
mister," Gus said, "you can't judge a book by its cover. And you can't
judge how much power a generator will take or a motor will give by its size.
"The
self-starter motor on a car is a specified job. It has to develop as
much as a half horse power or more for just a few seconds of time and it has
to do it on only six volts of electrical pressure. To get that result,
the armature is wound with solid copper bars and the field with a few turns
of heavy copper ribbon. Then there are four copper brushes with a wide
commutator. When you press the starter button, the juice flows through
the starter motor in a regular flood. Maybe as much as three or four
hundred amperes go shooting through the starter motor windings for the
fraction of a second it takes to 'break loose' a cold engine. Even
after the crankshaft starts to turn, maybe seventy-five to a hundred and
fifty amperes keep on flowing until the ignition takes hold. No
starter motor could stand that load for long. The only thing that
keeps it from burning up is the fact that it only has to run for a few
seconds at a time.
Now the
generator is a different proposition. It's on the job as long as the
engine is running above idling speed. So it's designed to produce not
over eighteen or twenty amperes and it keeps the battery charged only
because it runs a lot longer than the starter motor. If you tried to
make a regular size generator produce more current than about twenty
amperes, it would soon burn out.
"Mechanically,
too, there are differences. The bearings on a starter motor are pretty
crude because they don't have to stand steady running. Generator
bearings, being made for continuous use, are much more durable.
"The copper
brushes needed to cut down the resistance and let lots of current through
the self starter motor windings are not nearly as good for steady use as the
graphite carbon brushes used in the generator."
"That reminds
me," Dilbow cut in, "The self starter on my old car doesn't always work.
Sometimes when I step on the pedal it turns the motor over in a sort of a
rough, bumpy way. The next time, it won't stir at all. What's
the matter?"
"Turn on the
headlights and watch the ammeter when you step on the starter," Gus advised.
"If the starter takes hold and the needle flickers to beat the band or the
starter doesn't work at all and the needle stays still, probably the
self-starter commutator is worn and burned so badly the brushes only make
contact part of the time.
"There are
other things the ammeter needle tells you about your electrical system," Gus
went on. "It shows you whether or not the generator cut-out is
working, besides telling you when the generator is on the job. It
tells when one headlight burns out by the difference in the needle position.
It shows you what happens when you move the third brush and how much to move
it to get the result you want. If the motor suddenly cuts out when
you're breezng along, a quick glance at the ammeter will tell you whether to
look for a break in the primary ignition wiring, something goes wrong with
the breaker points, a burned out condenser, or a shorted distributor head."
"How do you
tell that?" Dilbow asked.
"Simple
enough," Gus explained. "When the ignition system is working, it takes
current and the needle shows on the discharge side. If the primary
circuit is open or the breaker points have backed away so they don't touch
or they're burned so badly they don't let any current through, the needle
goes right back to zero. If the needle acts as usual you can be sure
that the contacts are working and the trouble must be in the condenser, the
high tension winding of the coil, the high tension who from the coil to the
distributor, or the distributor head.
"See how this
all brings you right back to this new invention of yours." Gus added,
fingering the drawing. "You'd never have wasted any time on this idea
if you'd figured out what the ammeter shows. It's really like a gear you
could put on a water pipe to show you how much water is flowing."
"I get you,"
Dilbow observed. "The starter motor uses electricity by the basketful
for just a few seconds and the generator puts it back, a spoonful at a time,
and the only reason it works at all is because the generator is on the job
all the time."
Slowly he tore
the brown paper plan into long, thin strips. "I guess I won't waste
any more time trying to get something for nothing!" he added.
END
