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Old 06-19-2006, 07:02 PM
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Yet another asymmetric 3link

I've come up with yet another way to bias a 3link to provide equal rear tire loading on launch (and no squat or rise). I believe this has some advantages over the other designs in that the link loads are more equal and there should be fewer packaging problems. The results are the same, of course.

http://home.earthlink.net/~whshope/id16.html

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Old 06-19-2006, 07:18 PM
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BillyShope,

It sounds good but your got any drawings. I am a visuial kind of guy myself.
Scholman
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Old 06-20-2006, 10:39 AM
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Okay, here's a picture. The original is from "Race Car Vehicle Dynamics," but it's been highly modified with photo software. Any resemblance to a real car, living or dead, is purely coincidental.

Last edited by BillyShope; 06-20-2006 at 11:29 AM.
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Old 06-20-2006, 11:45 PM
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BillyShope,

I got the picture. So you want to change the length of all the attachment points on the rear housing. Then change the anchor points on the frame and body. Lots of work but I think it will work. You want to check the pinion angle with this set-up too. As the housing twists it will change the place the tire meets the track when the power is put the the drivetrain. So the weight of the car will end up behind the tire footprint. Just a thought is all.

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Old 06-21-2006, 02:29 AM
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Quote:
Originally Posted by scholman
BillyShope,

I got the picture.
Scholman
I'm afraid you've missed the picture. You're reading too much into that picture I posted. It's merely a "cartoon," and a rather crude one at that. I don't want to "change the length of all the attachment points on the rear housing" or "check the pinion angle" or "change the place the tire meets the track." The ONLY significant information obtained from the cartoon is that, while the lower left link is straight in the plan view, the other two links are rotated clockwise slightly. Again, that's the ONLY thing to be noted. When you hit the "Display" button at my blog, the first two tangents are for those plan view angles and the last two are for the angles as viewed from the side.

So, for instance, if you were to use this scheme on a 2005 Mustang, you might choose to keep all the front link mounts in their stock location and merely fab new mounts for the axle housing to provide the proper angles.
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Old 06-21-2006, 06:58 AM
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Dumb as I am, wouldn't that set up push the rear axle to the left under load?
If you mounted the panhard rod (a half assed Watts linkage) the other way - frame mount on the left - it would reduce this axle displacement.
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Old 06-21-2006, 07:15 AM
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Remember, Ian, that, during launch, the upper link is in tension and the lower links are in compression. So, with the proper angles, the lateral forces are equal and opposite.
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Old 06-21-2006, 05:28 PM
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Why not move the upper link to the right to counter act the unloading of the RR tire. That what we do on dirt.
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Old 06-22-2006, 03:37 AM
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Yes Billy, but in spite of your 'no rise/no squat ideal I still feel that the driveline loading will be greater on the rr until the rear end is 'forced' to the left, thereby evening up the tyre loading 'seen' both by computer simulations and wheel scales.
I see your premise, I just don't agree. BTW we've had 1 inch of rain in 6 months and now 28 consecutive frosts - still only early winter.
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Old 06-22-2006, 05:59 AM
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Quote:
Originally Posted by johnsongrass1
Why not move the upper link to the right to counter act the unloading of the RR tire. That what we do on dirt.
Yes, that was the original answer and was used first (to my knowledge) by Jaguar on the early C-Types. I worked with a car that ran at the El Cajon 3/8 paved (and that won the track championship) with an offset upper link. We also used this on the first Ramchargers' C/A.

I see this latest configuration, however, as having some advantages, mainly in packaging and in a more even distribution of link loads.

Go to my blog and you'll find spreadsheets for the setup of the offset link, this new design, and other possibilities.

http://home.earthlink.net/~whshope
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Old 06-22-2006, 06:11 AM
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Quote:
Originally Posted by IanRiordan
Yes Billy, but in spite of your 'no rise/no squat ideal I still feel that the driveline loading will be greater on the rr until the rear end is 'forced' to the left, thereby evening up the tyre loading 'seen' both by computer simulations and wheel scales.
You seem to be missing something, Ian. First, the no squat/no rise feature has no direct effect. It only ensures that the link loading is predictable and, thus, the driveshaft torque is completely canceled.

And, the rear end is never "'forced' to the left." Since the suspension springs are unaffected, loading is essentially instantaneous. Since the transverse force components in the upper link and lower right link are equal and opposite, the rear axle assembly is never "forced" to either the right or left.

Neither a computer simulation nor wheel scale readings were used in the development of the spreadsheet. It was simply a matter of application of d'Alembert's Principle to the linkage configuration.
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