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
Attachment 65946

C-4 Suspension
Attachment 65947

C6 Suspension w/Camaro Differential
Attachment 65948

Multi-link Mock-up
Attachment 65949

DecaLink
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Old Track car
 

Wondering what you have heard about the CV joints
vs old spicer/u-joint shafts.... one of my Pantera buddies
states the harmonics are better on the CV joints... I have
seen one of the big block cars tear up a set of CV joints
but u-joints can also fail

Also been told the CV joints need to be maintained
I am toying with changing out the shafts on my Pantera

By the way the Big block Pantera has a C-5 suspension
adapted to his car.. Thanks to you an Ron for all the info

Bob

Hey Bob,

If you are referring to the u-joint shafts with splines to absorb the length changes during suspension travel, there are some problems with spline friction/binding with high horsepower applications. Friction in the splines causes inconsistency in suspension geometry. The newer CV joints are very strong - in fact some drag and standing mile cars are hitting them with 2000+ WHP. I ordered the "1250 HP" CV joints/shafts from Detroit Speed - should be plenty good for a track car with 8-900 HP.

Pappy

Old track car
 

Thanks for the info
Yes was talking about cv joints

Bob

Great discussion!!

I'm not a suspension "guy" --- frankly -- I could care less about it. I have a guy that knows a guy that knows a thing or two about that stuff.... so I can keep my pretty little head as empty as possible....

My many many years of experience with C3 "stuff"...... I could always find the weakest link. Usually the little stub axle. Shear those little POS easy.


The setup Pappy has found is certainly NOT C3..... and Detroit Speed should know a thing or two about horsepower! Looking forward to updates when you finally hit the track with this!

Thanks Greg. Building it for NASA TTU/STU, so maybe we can get together on track - figuratively, not literally. Got the intake today - nice piece. Moving the motor down 2 more inches (small flywheel and Tilton bell housing and shallow dry sump), but will still have to have a 4 inch cowl hood to get plenty of room for airflow.

Pappy

Attachment 65985

Attachment 65986

Old Track Car
 

Hogan's manifolds are always a work of art
Thought about just having one in my office
to smile at on a bad day

Looks like your vette has all kinds of great items

Bob

Getting on track with friends..... YOU BET PAPPY!!! Let's do this!!!

A little progress. Motor is almost done and ready for the dyno. Hogan is doing a little more on the manifold and the harness for the Motec is in work. Ron Sutton just spec'd the front sway bar and will soon get the JRI shocks for a little "secret sauce". That finishes the suspension. Sorry for the quality of the cell phone photos.

Pappy

Attachment 66530

Attachment 66531

Attachment 66532

Hey Pappy, any updates on this?