View Full Version : Question re: aerodynamics
The question below comes from a friend of ours who casually follows auto racing. He saw Kenny's crash on the news and was wondering about the difference between c-wagons and ChampCars, specifically the seeming tendency for the former to become so easily airborne. Can someone give me a concise answer for him??
"Do the IRL race specs call for a lighter engine and chassis? If so, would getting more front end weight help or would the cars have to generate more downforce than they are currently capable of?"
Thanks in advance.
those cars'll need emergency 36 hour long uncrapification surgery.
Warlock!
10-14-03, 01:48 PM
After looking at the Krosnoff wreck, Jeff's car clipped Johansson's right rear which started the launch. It looked like the car was going to continue at an angle of about 30 degrees and quite possible NOT blow over, until the bottom of his car hit Johansson's rear tire. At that point the car was launched WAY the heck into the air and into the fence. The biggest difference was that I suspect the Earl cars were travelling 40-50 mph faster, contributing to an easier blow-over.
I can't imagine that there is too much difference between the two cars to make the crapwagon blow over sooner than a champcar, but the Mario thing really blows my mind.
How's that for a non-answer? :D
Warlock!
I think it's an imbalance between wing downforce and sidepod downforce. Less big wing would equal greater sidepod downforce and less chance to get it off the ground. Why they haven't announced windtunnel time to the public is beyond me, but I suspect they might have to give up their sidebyside formula to get it fixed, and they ain't going there. So, more people will get hurt.
The IRL cars get most of their downforce from the wings, while the champ cars get most of theirs from the undertray. I wonder if the larger wings, and flatter bottoms make for a better "wing" when air rushes under the car.
It should be noted that this year is the first year that the IRL cars have shown the tendancy to blow over. In the past, when one of them has gotten wheels off the ground, it has done much of the same thing that a champ car does - fly close to the ground.
One of the head on replays showed that the car was well into getting airborne as soon as the front wings cleared the top of Sheckters car. From that head on, the car really started getting air quick after the front wings caught air.
http://www.motorsport.com/photos/irl/2003/tx2/irl-2003-tx2-mj-0216.jpg
I've done a couple frame-by-frame reviews of it and came to the conclusion that what got the car airborne was the shape of the rear of the sidepod on Scheckter's car. Notice the sharp upward angle at the rear. Brack's left-front rode right up that angle. Once his nose got above the sidepod, the air got under the car and the rest is history.
Warlock!
10-14-03, 04:09 PM
OK... I looked at the replay of Brack some more.
Brack's front left wheel touches Schecktard's sidepod, causing Tommy to turn hard right. Brack's spinning LF wheel causes his car to climb onto Tom's sidepod, where the nose of Brack's car rests for a fraction of a sec. Tom is now slowing down at an alarming rate (going sideways and all), but Brack's momentum continues, forcing his car to slide over Tom's sidepod and then up and over his airbox, tossing his nose back at an extremely agressive angle (probably close to 45 degrees). At that point the air seems to take over and finish the job. The air's not catching the the front wings as I had originally thought, 'cause Brack's LF wing was torn off by the initial impact. At one point of the video, all you can see is the flat bottom of the car, which the air has no trouble getting underneath and lifting it into the fence.
A champcar could very well have just leapt over the other, being as there is no launching ramp in the form of an airbox taking up 1/3 the length of the car.
Warlock!
so in other words, it has nothing to do with their intrinsic crapiness, but rather the imparted velocity from the wheels to the other chassis, as all open wheel cars are prone to be subjected to. nothing different from krosnoff then...
Methanolandbrats
10-14-03, 09:10 PM
The bigger the wing, the shallower the angle of attack to make downforce. Big f'n wings on IRL ****boxes use the shallow angle. It turns into an airplane wing if the nose tilts up.
How fast was Krosnoff going compared to Brack?
Or for that matter Takagi?
http://news.bbc.co.uk/media/images/38391000/jpg/_38391305_takagi_airborn_pa300.jpg
I remember Rahal going over a few years ago. Just can't remember where. Good look at the underside of his car.
Jonezzy_33
10-15-03, 01:01 AM
Correct me if I'm wrong, but I seem to remember the cars that go airborne most this year are the Dallaras (haven't watched much IRL), ie. Mario's accident, Dan Wheldon, and Kenny's. That flat nose needs to be looked at.
Yup, ...like NASCAR's roof flap...the earl needs a nose job...a nose flap...
chop456
10-15-03, 01:50 AM
Rahal's flip was at Motegi.
Warlock!
10-15-03, 07:19 AM
Originally posted by chop456
Rahal's flip was at Motegi.
And didn't he get backwards before he flipped over? (and Wheldon too, for that matter?) I would think that cars using air to push them to the pavement as they move forward would have a pretty easy time flipping over when running backwards if the aero bits are intact.
Warlock!
indyfan31
10-15-03, 08:04 PM
I've read somewhere that a formula car's aerodyamics (wings included) go to pot as soon as the car turns sideways, so they're not providing downforce or lift. BTW, for a car's wings to act like an airplane's they'd have to be upside-down.
One area that no one's brought up is the construction of the suspensions. Cars get airborne because their tires climb on each other or the body of another car (with the exception of Mario). If the suspension were to collapse as that's happening I believe we would see less of these types of events. Remeber Al Jr. getting up on two wheels in one of the Canada races? Theoretically the suspension should have collapsed. Of course, there's a fine line between strong enough to last the race and too strong.
Jag_Warrior
10-15-03, 09:52 PM
Originally posted by Ankf00
so in other words, it has nothing to do with their intrinsic crapiness
No, I think it's more about the intrinsic crappiness. I've got a spread sheet populated with proven data and a slide rule held against an image of Eddie Cheever's car... oh yeah, and sworn testimony from a guy named Jake. Yeah, it's the intrinsic crappiness. Definitely the intrinsic crappiness. No doubt in my mind.
the intrinsic crappyness IIIIIIIS pretty, well, crappy.
Originally posted by anait
Can someone give me a concise answer for him??
http://www.racinglines.com/ezimagecatalogue/catalogue/variations/1704-250x250.jpg
I don't know.
Originally posted by FRANKY
Or for that matter Takagi?
I don't think Takagi's wreck was due to the car lifting aerodynamically, it seemed to be more of a typical wheel/wheel launch.
We need an engineer. But this works for almost everything in engineering.
"Its a combination of factors."
From what other engineers have said here and at crap wagon.
The big front wing is a big factor. All wings can generate both lift and downforce, it just depends on the angle. (Stick your hand out the window of a car. Vary the angle. Sometimes your hand will lift, sometimes it'll drop.)
When the nose pops up, the IRL has bigger front wings, it generates more lift, it flies much higher.
Two, someone was explaining here one of the makes of crapwagon is more likely to pop up than the others due to weight distribution and length of the car.
In any engineering problem, there are a number of solutions. Smaller front wings would definitely help. The most popular solution over at crackforum would probably be putting the engines in the front.
I doubt the front wings have much to do with it. Brack lost one of his in the initial impact. (Usually you do lose a front wing just before wheel to wheel contact like that. The wing needs to be out of the way before the wheels can touch.) Its hard for something that isn't attached to provide lift.
I suspect it has more to do with them having a pretty flat undertray that has gotten larger and larger every year. The front wings aren't like your hand out the window, the entire car is!
It might be made worse by the giant gearbox at the back of the car. That keeps the rear down when the nose goes up. The gearbox is almost a pivot point in the blowovers.
One wing will still generate lift when tilted up into onrushing air. The car will just twist as it rises. Which I think is what happened to Brack. (I didn't watch very closely.)
And I think that flying Mario still had both front wings.
You're right though, once enough air builds under the IRL chassis the entire car becomes a wing and generates lift. And that has happened to some sportscars, so you don't need big wings to have a blow over.
Like I said, "a number of factors."
Krosnoff got his altitude because his front wheel made wheel to wheel contact, and on the way up, his rear wheel also made wheel to wheel contact.
Takagi's car didn't blow over, it got drilled in the side and launched. The most similar CART accident in recent memory would be Tag taking flight over Haberfeld at Road America. I don't know how high he got, but his car didn't cartwheel like Mario's, Wheldon's, or Brack's.
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