Gus Wilson's annual visit to his upstate relatives had a way of developing into
a busman's holiday.
On this particular trip, his hopes
for a workless vacation were shattered the second morning of his stay.
This time it was Bill, his eldest nephew, who upset his plans for a week of
rest.
"Uncle Gus," the young man began
timidly as the gray-haired auto mechanic propped his morning paper against the
sugar bowl and leisurely poured himself a second cup of coffee, "will you show
me how to check the steering gear on my car while you're here?"
"What seems to be wrong?" asked Gus
good-naturedly.
"The car keeps running to the
right," explained Bill. "I have to wrestle with the steering wheel to keep
it on the road."
A grunt was Gus's only answer as he
followed his nephew to the front curb where the car was parked.
"First of all, we'll have to find a
good place to work," said Gus after a hasty inspection. "How about running
the front wheels onto the driveway outside your garage? While I move the
car around there, you go to your Dad's workshop and see if you can hunt up a
couple of lengths of wood lathing, a hammer, a saw, some nails, and a large
steel square. And, say, if you can find one of those adjustable spirit
levels bring that along too."
Gus finished parking the car just as
Bill, his arms laden, emerged from the cellar door.
"What are you going to do with all
this stuff, Uncle Gus?" asked Bill as he piled the tools and lumber on the car's
running board. "All I want to know is how to check the steering gear."
"I don't think the steering
gear has much to do with your trouble," replied Gus as he picked up the two long
sticks and sighted along the first one and then the other. "Sounds like
unequal caster."
"Unequal what?" asked Bill.
"Caster," repeated Gus. "Don't
you know what that is?"
"No relation to the oil, is it?"
grinned Bill.
Gus shook his head. "Nope,
it's an angle and it's one of three important front-wheel adjustments. There's
camber, toe-in, and caster."
The puzzled look
on Bill's face told Gus that the subject needed some tall explaining.
"Here, take a look at this," said
Gus as he wheeled out a bicycle that had been leaning against the garage wall.
"Do you notice how the steering pivot for that front wheel is back of the
wheel's center. Well, that's caster. It's just like the arrangement
of the casters on furniture legs. The front wheels at an automobile are
pivoted in just the same way. The king pin on each wheel is tilted by the
axle to give the caster angle.
"Now, if this bicycle wheel is tilted a
little off the vertical," Gus continued as he held the bicycle at an angle,
"that illustrates camber. The front wheels of a car are tilted just like
that. They're mounted to be closer together at the bottom than they are at
the top.
"As for toe-in, that's just what
you'd expect from the name," continued Gus.
"The front wheels are pigeon-toed;
their front edges are closer together than their rear edges."
"How the dickens can two wheels be
like that all at once? Seems like they'd get all mixed up," argued Bill.
"As far as I can see, camber and toe-in are pretty much the same thing, except
one is horizontal and other is vertical."
"Right," agreed Gus, "and if either
the caster or the camber are wrong, they'll upset the toe-in. That's why
toe-in is a check on them all. If the toe-in measures O.K., you can be
pretty sure that the camber and caster are right."
"Sounds like an awful lot of
measuring to me," observed Bill. "How would you check all those angles?"
"Well, the best way is to use
regular measuring instruments that are made for the work. All good repair
shops and service stations have them. Of course, in a case like this, you
can put together some tools that will do a good enough job.
"For instance, camber tilts the
front wheels out at the top, like this," Gus explained, indicating the angle
with his hands. "Well, we can check that by placing a large steel square
flush against the hub and measuring the distances between the rim and the
vertical edge of the square at the top and at the bottom of the wheel. If
the wheel has camber, the distance at the top should be less than the bottom
distance.
"If the car is an old model, two
long laths, pointed at the ends and fastened together one on top of the other
with four or five heavy rubber bands will do to space off the measurements.
Of course, on new cars you'll have to add arms at the ends to get around the
motor pan.
"As for caster, you can use an
adjustable spirit level to check that. The caster angle generally is
obtained by the twist of the axle. So by placing the spirit level
crosswise on the axle, first at one end and then at the other, and adjusting it,
you can measure each angle.
"Suppose some of these adjustments
are wrong," interrupted Bill, "how do you make them right?"
"Well, if the caster, for example,
is wrong, it generally means that the axle has been bent in an accident.
Naturally the only way to fix it is to bend it back."
"Do you have to heat it" asked Bill.
"That's the one thing you shouldn't
do," declared Gus positively. "Heat would spoil the original heat
treatment that's responsible for the strength. If you have to bend it, do
it with the metal cold. It's a tough job, though, and I wouldn't advise
trying it unless you have experience and the right tools. Of course, if
the caster is out only a little, you can correct it by loosening the spring
saddles and driving wedge-shaped shims in between the spring and the spring
seat. That will tip the axle.
"Camber can be changed by bending
the portion of the axle between the springs and the wheels. As for toe-in,
that's the easiest to adjust. All you've got to do is lengthen or shorten
the front axle tie rod."
As Gus talked, Bill was inspecting
each of the front wheels on his car. "But what makes you think my trouble
is unequal caster?" he inquired at last.
"I'm just like a doctor," chuckled
Gus. "I diagnose from symptoms. You complain of hard steering to the
left and a tendency to pull to the right if you don't keep your hands on the
wheel. My diagnosis from these symptoms is that each wheel has a different
caster angle. The car turns to the right; that means that the right-hand
wheel has less caster than the left.
"It's the same with camber, only you
have to look in a different place for the symptoms. If you have too much
camber, the outer edges of your tires will wear faster than the rest of your
tread."
"What are we going to do about my
car?" asked Bill impatiently. "There's no sense checking the caster, if I
can't fix it."
"Well, drawled Gus, "I'd
suggest that you check all three adjustments just for the practice. You
can learn a heap about your car that way. Then, when you find out just how
much the caster is out, perhaps we can fix it with wedges.
"And, by the way, before you do any
checking be sure that the car is absolutely level and that the tires are
properly pumped."
With that, Gus turned and ambled
toward the house. As he reached the front steps, he glanced back and
grinned. Bill was hard at work, and Gus knew that doing was the best way
of learning, and besides - now he could get back in that morning paper.
END
