by Craig Langman

Physics 211

November 30, 1999

Learn how Auto-racing brings man and machine together at the outermost limits of speed.

In the 1960’s racecars approached 200 miles per hour with huge engines and by streamlining their vehicles, but this made cars like a wing. They were low to the ground, and flat on the bottom.

This made the air on the top to have to go farther than the bottom, therefore creating lower pressure and lifting the car off the ground.

In 1965 Jim Hall found the solution to high cornering speed. At the time, the auto-racing world was dominated by Ferrari, Porsche, and Ford. But Jim Hall won in Florida at age 24 with his homemade ‘chaparral’ roadrunner built in Texas.

He discovered by adding a rear wing, a negative-lift was created, causing downforce, keeping the car from loosing control on corners.

Modern Indy Cars not only use a rear wing, but also a front wing. They entire car, including wings, are made of space age carbon fiber. Modern Indy Cars travel at speeds around 230 miles per hour – that’s over 1 football field every second, all with an engine no larger than an everyday sedan, yet they put out 800 horsepower!

It is necessary to balance the downforce between front and rear, and this is a difficult task. If there is too much downforce on the rear, it will cause the car to ‘push’ into the walls on corners – whereas is there is too much downforce on the front it will cause the rear to spin-out on corners.

Also modern cars have an under-tunnel, also called a Venturi tunnel. This non-flat bottom sucks the car downward due to the creation area of low pressure.

In order to test wings, a wind tunnel such as this one at Ohio State University is used. This tunnel tests ideal conditions at 150 miles per hour.

With the computers at Ohio State’s Wind Tunnel, negative lift (downforce) can be compared with drag, or air resistance, to optimize the wings performance, to get the needed downforce for corners but reduced drag for straightaways.

While cornering, the driver undergoes more than four G’s, or four times the acceleration due to gravity. There is enough downforce for the car to stick to the track even if it were upside down. A drivers heartbeat exceeds 180 beats per minute, mainly due to these high pressures.

It takes a team of engineers to design and maintain an Indy Race Car. All of these engineers understand physics very well – aerodynamics & fluid mechanics, motions of all types. Without the knowledge of physics, these cars wouldn’t even be possible.