Re: [Phys-l] race car spoiler

["John SOHL" <JSOHL@weber.edu>]

I had once been told that the old Chevys with horizontal fins had an interesting problem. The story was that when they took models like the 1959 Chevy Bel Air (Google found some pictures at: http://pranksterzette.com/mayfeats08.aspx 2/3 of the way down the page) and put large police car engines in them there was an aerodynamic problem at high speeds. The claim is that the horizontal fins caused a bit of lift that reduced rear wheel traction causing the cars to more easily spin out at high speeds in turns. 
 
I never heard or saw anything that would corroborate this claim and always wondered about it. It just didn't seem like there was enough of a fin there or the right shape to cause significant lift. Also, I can easily imagine other suspension issues that could cause high speed instabilities in turns. What I don't know is if identical suspensions were in use in models without the horizontal fins and if the vehicles behaved differently.
 
Does anyone know anything about the veracity of this claim? 
 
Thanks, 
 
John 
 
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John E. Sohl, Ph.D.
Professor of Physics
Weber State University
2508 University Circle
Ogden, UT 84408-2508

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> > > chuck britton <cvbritton@mac.com> 11/4/2009 8:09 AM >>>
NASCAR has for the last several years, required a special spoiler to 
be built into the rear of the roof that DOES help prevent flipping. 
You only see it once it automagically opens on an already airborne 
car.

Watch clips of the recent Talledega race to lots of such action.
The fans really got their money's worth of crash action there toward the end.

Doubt that the 'standard' spoiler has much effect in crashes.

I'm always amused to see such spoilers on front wheel drive street cars.


At 9:51 AM -0500 11(4(2009, Anthony Lapinski wrote:
> I'm teaching Newton's laws now There are some neat ideas/discussions about
> race cars, friction, tires, etc.
> Like most ordinary cars, race cars are rear-wheel drive and have the
> engine in the front. Many also have a spoiler on the back. When air flows
> past this, it exerts a downward force on the car. This is good for
> traction on curved pavement and acceleration on straight pavement.
>
> Now, does a spoiler also help prevent a race car from flipping over at
> high speeds? I've seen race cars flip, but usually when they get hit or if
> they turn too suddenly. Would race cars be more likely to flip without a
> spoiler? And if so, how does this occur? Is it the
> shape/weight/aerodynamics of the car? At fast speeds air gives it an
> upward  lift from underneath? I'm a little confused with this. Can anyone
> provide an explanation?
>
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