Aerodynamic down force
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From: saratoga, ca
Burning Brakes
Joined: Oct 2004
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From: Kelowna, BC, Canada
This isn't exactly what you're looking for, ut if you're already set up with a data logger, you can do your own my-car-in-the-real-world testing. I strapped a pair of $5 (used, ebay) sensors from a 1995 Lincoln Continental to my front and rear suspension pieces, and did some steady-speed tests (both directions to correct for wind) on a remote stretch of freeway near my house. I was able to see consistent and repeatable changes in ride height from as-small-as-4-degree changes in my wing setting. I packed up all my pieces, and tested them all one Saturday afternoon.
It works on the track, too.
It works on the track, too.
That is STILL one of my all-time favourite threads, ever.
Yes, I think I have a man-crush on Jack.
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Joined: Nov 2002
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From: Chicago
I thought that was common knowledge. If you tell me your axle weights, wheelbase, and horizontal distance from rear wheels to wing, then I'll tell you how much front lift you get per pound of rear downforce. Just algebra.
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Joined: Jun 2001
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From: Los Angeles
Algebra is tough for some of us. 
The sandbag picture took me back to testing my wing -- I used 350# of sand. It looked ridiculous, but it held (which wasn't bad for six pounds of aluminum and adhesive).
And I'm glad you liked that thread, jgrant. I still can't believe I had the spare time to do all of that, but I'm glad I did it. It was a lot of fun for a non-engineer type like myself.
The sandbag picture took me back to testing my wing -- I used 350# of sand. It looked ridiculous, but it held (which wasn't bad for six pounds of aluminum and adhesive).
And I'm glad you liked that thread, jgrant. I still can't believe I had the spare time to do all of that, but I'm glad I did it. It was a lot of fun for a non-engineer type like myself.
Pro
Joined: Nov 2004
Posts: 526
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From: in the Hinterland
Hey Jack,
I missed that whole adventure of yours on Pelican, so I was glad to catch it this pass.
Great stuff.
As I told Steve (Weiner) when i forwarded it to him to read,
"...gotta hand it to Jack for his curiosity, intuitiveness, and inventiveness."
Granted, your research methodology was affected by handmade equipment and some generalization;
but, your thought process was very linear. To that end, progress was made.
I would love to have seen the face on any CHP in the area as you blitzed between on-ramps!!..LOL!
I've been grappling with the same issue of trying to keep the nose down..it's not an easy nut.
The rear is anchored very nicely, which , as you pointed out, is exacerbating the front issue.
Going to review the two links you posted as well.
Nick
I missed that whole adventure of yours on Pelican, so I was glad to catch it this pass.
Great stuff.
As I told Steve (Weiner) when i forwarded it to him to read,
"...gotta hand it to Jack for his curiosity, intuitiveness, and inventiveness."
Granted, your research methodology was affected by handmade equipment and some generalization;
but, your thought process was very linear. To that end, progress was made.
I would love to have seen the face on any CHP in the area as you blitzed between on-ramps!!..LOL!
I've been grappling with the same issue of trying to keep the nose down..it's not an easy nut.
The rear is anchored very nicely, which , as you pointed out, is exacerbating the front issue.
Going to review the two links you posted as well.
Nick
Race Car
Joined: Jun 2001
Posts: 3,929
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From: Los Angeles
Thanks, Nick. No doubt there's a whole lot that's less-than-rigorous in my testing, but -- as a guy who stopped his hard science in freshman year's 'Physics for Poets' -- I appreciate the compliment. It was interesting to take a real-world look at those pieces and modify them based on a repeatable (if not fantastically precise) testing regimen.
I was lucky with the CHP. At a few points, I think they could have easily cited me for reckless ridiculousness:
I was lucky with the CHP. At a few points, I think they could have easily cited me for reckless ridiculousness:
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Race Car
Joined: Jun 2001
Posts: 3,929
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From: Los Angeles
The tuft test picture is on the 10 Freeway here in Los Angeles, a fairly busy stretch of road. At one point I'd worked up an air-pressurized 'confetti cannon' to shoot sparkly glitter in front of the wing so that I could photograph how the air was flowing over it at freeway speeds.
I'm still amazed I never the cops never pulled me over.
I'm still amazed I never the cops never pulled me over.
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From: Berkeley, CA
Chris -
Do you mind telling us the backstory behind this? I've been puzzling over it since I saw it. I realize they're trying to simulate aero load but why w/ bags of top soil? Did they not run on a 7-post rig previously? Or have the suspension geometry all mapped out? It looks like a Rennlist, club-racing level science project, rather than a Champcar-level science project.
Do you mind telling us the backstory behind this? I've been puzzling over it since I saw it. I realize they're trying to simulate aero load but why w/ bags of top soil? Did they not run on a 7-post rig previously? Or have the suspension geometry all mapped out? It looks like a Rennlist, club-racing level science project, rather than a Champcar-level science project.
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From: yorba linda, ca
Actually this was an exercise in load cell validation and calibration. It was done at the track where a shaker rig wasnt available, whereas a feed store was
Notice the zip-lock bags under each tire? Even with this weight on the thing, one could easily move the car side to side. Very easily.
Notice the zip-lock bags under each tire? Even with this weight on the thing, one could easily move the car side to side. Very easily.
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Joined: Oct 2001
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From: Berkeley, CA
Actually this was an exercise in load cell validation and calibration. It was done at the track where a shaker rig wasnt available, whereas a feed store was
Notice the zip-lock bags under each tire? Even with this weight on the thing, one could easily move the car side to side. Very easily.
Notice the zip-lock bags under each tire? Even with this weight on the thing, one could easily move the car side to side. Very easily.
Thanks Chris! Did you manage not to break open any of those bags?
Was this at Firebird Raceway?
Instructor
Joined: May 2006
Posts: 164
Likes: 1
Jack,
That is, without doubt, the COOLEST example I have yet seen of personal/vehicular exploration for a cause. The last shot of your drive down Hwy 10 makes me laugh in recognition of "the madness", but also makes me shake my head in awe. I most humbly submit that my hat is off...
Chris W.,
If that Image doesn't make it into the Motorsports Hall of Fame, I'll be sincerely disappointed. That's one of the greatest images I've seen on Rennlist.
Thanks guys. Cool thread!
Regards,
Dave
That is, without doubt, the COOLEST example I have yet seen of personal/vehicular exploration for a cause. The last shot of your drive down Hwy 10 makes me laugh in recognition of "the madness", but also makes me shake my head in awe. I most humbly submit that my hat is off...
Chris W.,
If that Image doesn't make it into the Motorsports Hall of Fame, I'll be sincerely disappointed. That's one of the greatest images I've seen on Rennlist.
Thanks guys. Cool thread!
Regards,
Dave
Formula One Spin Doctor
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From: RPM Central
A Feeder Rig ? ...............................