Old track car project - new update

[mfain]

Ron Sutton gave a good response to questions about an IRS versus an offset 3-link in Greg Weld's Track Warrior project thread. I have been messing with the IRS for 40 years and have stumbled on most of the "issues" that Ron points out. However, I think I am getting close to a solution that solves a lot of the problems.

Background: I first tried an old C-3 Corvette IRS. Lots of issues, the most significant of which were that the half shaft acted as both a drive shaft and a suspension link, and as the suspension compressed it caused toe out roll steer which is why you see C-3 corvettes with the rear hanging out most of the time - fun, but not very fast. Then I went to a C-4 Corvette-based suspension. Better, but the half shafts were still part of the suspension, and the forward links are too short causing fore-aft movement of the tire with suspension travel. This contributes to roll steer, but GM made the toe links long so the rear would toe in with compression (for road safety reasons). Then there are the C5 to C7 Corvette-based systems with upper and lower control arms like a front suspension. If you don't use the Corvette transaxle then you need to fabricate a system for a differential. We did that using a Camaro differential and Corvette control arms in an old Jag. Works okay, but you better get the geometry right the first time because there isn't much provision. for adjustments, as Ron points out.

I prefer (and designed) a multi-link IRS much like the old CanAm cars and some other open wheelers. The multi-link applies drive and braking forces parallel to the car's longitudinal axis (like a 4-link), can be adjusted for bump-steer like a front suspension, and is easier to build in roll center and anti-squat/anti-dive adjustment capability. I was struggling with connecting the forward links to a C6 upright, when along came Detroit Speed's DecaLink. This gave me all the features I was looking for in a multi-link plus the Hammerhead differential is plenty strong and the 1250 HP axles shouldn't give any problems. I purchased the Decalink and will be installing it in the next few weeks, which will cause a little "surgery" since it wasn't designed for my chassis. Nothing a chain saw can't handle. LOL

Pappy

C-3 Suspension


C-4 Suspension


C6 Suspension w/Camaro Differential


Multi-link Mock-up


DecaLink