Dude, Where's My Downforce?

What makes a racecar spontaneously rip a 360 backflip? A perfect storm of hills and tailgating, that’s what. In this case, driver Yannick Dalmas, racing for Team Porsche in the 1998 Petit LeMans at Road Atlanta, was drafting the car in front of him while zooming over a rise. As he crested the hill, the car’s suspension pulled up, allowing more air to flow under the car and creating lift. Simultaneously, the draft from the car in front of him interrupted the airflow over the nose of Yannick’s car, sapping the much-needed downforce that kept the car in contact with the pavement. Without that downforce, there was nothing to stop the car’s nose from continuing upward once it started. After that, it’s pure physics opera: The nose of the car leaves the draft zone and enters the airstream, which accelerates the lift and pushes the nose backward while the weight of the rear-mounted engine continues its forward momentum. Voilà! A fantastic, white-knuckled twirl that—luckily—sustained enough momentum to end upright. Must have been an awesome ride. (Dalmas walked away uninjured.) —Martha Harbison

Click here for more of The Breakdown

Comments

[Cameron]

so, are production cars with flat underbodies just as susceptable to such backflipping? I know it'll be rare to be zooming along right behind someone at racing speeds, but could there be similar situations in other kinds of cars?

[Andy]

Not likely to happen in a production model. The front mounted engine keeps the weight forward, and makes it very difficult for the rear end to continue momentum under the heavier front end.

[Paul]

If you ever watch any kind of supercar racing you'll notice the racers will only draft off the opponent in front of them for a small amount of time. Most of the time they will only draft for a few seconds and pull to the side. This is better for the down-force of the car to keep it stuck to the road yet adds more wind resistance when there is no car directly in front. Just watch sometime and you'll notice this.
A great site to visit to know more about race car dynamics and aerodynamics
http://www.mulsannescorner.com/

[Peter]

While there are few production cars that can do a backflip, there was one French built car that was famous for its aerodynamics and producing enough lift at 35 mph to lift off the ground.
Other production cars can also produce lift and is noticable at higher speeds, but this affects handling around corners and stability at high speeds. Those oversized spoilers on Civics, Mustangs and so on are perfect wings for generating lift.

[Gerard]

Dont want to be in one of those cars when they do their back flip