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 Post subject: Chapparal style wing?
PostPosted: May 14, 2009, 9:48 am 
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Moti, can you make it so the wing's downforce pushes down on the top outboard section of the rear upper control arms? :) (since you're not worried about class rules) That would definitely glue the back end down. :P

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PostPosted: May 14, 2009, 10:58 am 
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It'll make as much sense as putting a snowmobil motor on top of the fuel cell to create suction under the car :wink:

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PostPosted: May 14, 2009, 11:58 am 
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Blackbird wrote:
It'll make as much sense as putting a snowmobil motor on top of the fuel cell to create suction under the car :wink:

Moti

Yeah it was a stupid suggestion. :roll:


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PostPosted: May 14, 2009, 12:04 pm 
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No, I was joking around with your suggestion in reference to Chaparral by making a reference to another one, the 2J "sucker car" used a snowmobil motor to create the suction - http://en.wikipedia.org/wiki/Chaparral_Cars .

Image
Note the bulge in the cover right above the fans, that's where the snowmobil motor was installed (and why I said "right above the fuel cell", rougly the same location :wink: ).

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PostPosted: May 14, 2009, 12:06 pm 
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Call me stupid, but putting the wing termination point on the suspension would seem to negate many of the benefits of the suspension itself. I've always wondered about this, it seems that would inhibit suspension movement.

Downforce = weight (as the car sees it) Putting it on the car proper would seem to add weight without inhibiting suspension or road holding capacities.

Yes, I know it worked well for Jim, but that was in an era of no aero/ground effects/downforce racing so virtually anything would have blown the competition away.

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PostPosted: May 14, 2009, 12:20 pm 
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Roger that Moti, I thought that was your way of telling me to stay out of the liquor cabinet. :) Feel free to split this tangent off of your build log.

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PostPosted: May 14, 2009, 12:21 pm 
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carguy123 wrote:
Call me stupid, but putting the wing termination point on the suspension would seem to negate many of the benefits of the suspension itself. I've always wondered about this, it seems that would inhibit suspension movement.

Downforce = weight (as the car sees it) Putting it on the car proper would seem to add weight without inhibiting suspension or road holding capacities.

Yes, I know it worked well for Jim, but that was in an era of no aero/ground effects/downforce racing so virtually anything would have blown the competition away.


Actually, it makes the suspension work better, since you're not having to put jumbo springs to fight the force of the wing pushing the sprung weight into the ground.

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PostPosted: May 14, 2009, 4:48 pm 
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And doesn't inhibit movement?

And wouldn't that make the wing go up and down with the motion of the suspension? That's what it looks like in that drawing.

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PostPosted: May 14, 2009, 6:56 pm 
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As long as the linkages attaching the wing are designed not to bind it doesn't.

Think about it this way, if you have 100 lbs of downforce being created by the wing, you need 100 lbs of reaction force at the contact patch no matter where the wing attaches. If it attaches to the frame, its going to compress the suspension in the process of transferring that 100lbs; if it attaches directly to the suspension, it bypasses the springs and doesn't cause geometry changes by compressing the suspension.

IIRC, this design was banned from F1 since failure of either the wing or suspension could cause the other to fail and take the situation from bad to really really bad; not only would you lose the suspension but you also lose the aerodynamics that are stabilizing the car at that speed.

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PostPosted: May 14, 2009, 8:22 pm 
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carguy123 wrote:
And doesn't inhibit movement?


No, it doesn't. Movement doesn't matter, movement in relationship to something matters. Massive unsprung weight allows for movement of the tires in relationship to the road, tires bounce loosing traction before they gain it again. The wing inhibits movement of the tires away from the road, because it uses an external force to drive the tires into the tarmac.

Stiffening the suspension does a similar thing in F1 type cars, allowing all of the forces of the weight of the car and the aero package of the car to be delivered to the tires and force their contact with the road. We dont' want suspension to move the tire in in relationship to the road, we may want suspension to move the tire in relationship to the car (think offroad racers). The wing allows for force independent of the car to keep the tire in relationship to the road.


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PostPosted: May 14, 2009, 8:29 pm 
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I seem to remember reading the big issue with the wheel mounted wing was that it applied downforce discriminately to a contact patch so if a wheel came off a curb and went airborn the downforce on that corner was lost and it lead to erratic handling. Of course it wouldn't be off the ground long with the added force pushing it down. Were it chassis supported that downforce would have been transferred along with the weight of the car. Could be wrong... just something I picked up in a book somewhere.

That said, Chaparral did test the chassis mounted wing first and abandoned the project to move to suspension mounted wings. Smoother tracks, different tires and the ability to isolate roll and pitch/heave movements within the suspension helped put the aero onto the body.

Without a ton of work the best you can probably hope for is neutral aero. Despite manufacturer claims the wind tunnel doesn't lie. 'Supercars that actually produce overall downforce' is a surprisingly short list and the count of road legal cars that produce downforce above or equal to having a second person in the car could probably be counted on one hand. If you aren't going to have much downforce you may as well apply it to the tires :mrgreen:

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PostPosted: May 14, 2009, 11:54 pm 
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Well, I have seen the thing work. I was lucky enough to get to see Phil Hill win at Laguna Seca in 1967 while I was enjoying my Basic Training at Fort Ord. What a sight to see. Probably the most incredable racing event of my life.
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PostPosted: May 15, 2009, 9:01 am 
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I was lucky enough to talk with Jim Hall when he brought out the Chaparrals to Road America a few years back. This guy was a real engineer to say the least. I always wondered why the movable wing didn't really upset the stability of the cars when they were moved "up" to apply more downforce when braking. Obviously this causes a lot of drag which, when applied that high off the ground would tend to lift the front of the car. He smiled whan I asked this question and said that there was also what amounted to a trap door at the front of the car that dropped down simultaneously and applied a counterbalancing force at the front. I had never heard of this and I followed the Chaparrals like a hawk in my youth. When I told him this he smiled again and said "not many people ever realized it".

jdgar0649 wrote:
Well, I have seen the thing work. I was lucky enough to get to see Phil Hill win at Laguna Seca in 1967 while I was enjoying my Basic Training at Fort Ord. What a sight to see. Probably the most incredable racing event of my life.
Joe G.

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PostPosted: May 16, 2009, 10:06 pm 
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Speaking of CHAPARRAL ...

Not a bad museum. Lots of explanations of the basic science. Moveable aero is just one of the innovations from Jim Hall and Chaparral

You only get to touch one of the cars - the rest have proximity alarms. DAMHIK

They fire up and drive one of the cars every so often. I'm on the mailing list to get notified, just in case I can slip down there to watch one day.


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