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- By Alison Hine
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- All
four-wheeled vehicles which steer from the front wheels have
basically the same dynamics, whether it's an Indycar, a sports
car, a family sedan, a dump truck, or a little red wagon. I'll
focus here on the basic principles as applied to race cars.
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- In all
vehicles, the force produced by the friction of the tires against
the track or road surface is used to alter the car's velocity
and the direction of its velocity. These alterations are called
acceleration, cornering, and braking. With modern racing cars,
there are two factors which contribute to this force, or adhesion:
aerodynamic grip and mechanical grip.
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- In order
to develop a good race car, we want to develop maximum grip in
all directions, with minimum drag. This will give us the fastest
speeds through the corners, coupled with the fastest speeds down
the straightaways. Obviously we can't have both, so for each
track we will need to find the optimum tradeoff between straightaway
and cornering speeds; on short, twisty tracks, we'll be faster
with a car that emphasizes good cornering, while on fast tracks
with long straights we'll go quicker with a car that sacrifices
some cornering for straightaway speed.
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- We also
want the car's handling to be balanced; that is, when it reaches
its limits of adhesion, we want both the front tires and at the
rear tires to begin to slide at the same time, at the same rate.
If the car is not balanced, either the front tires will begin
to slide first, and we'll slide straight off the track, or the
rear tires will begin to slide first, and the car will spin.
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- We also
want the car to be forgiving. That means that its behavior is
predictable and consistent, and when it starts to slide, we want
the slide to be progressive rather than sudden. We'd like it
to begin to let go gently, with some warning, and get fairly
deep into a slide before it becomes uncontrollable.
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- All
of these things require tradeoffs. Let's take a look at how we
might break down the many factors affecting cornering, braking,
and traction into manageable parts, so we can have a basis to
work from when developing our race car's optimum setup for a
given track.
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