Quote:
Originally Posted by rat_rod_russell
And I appreciate the conversation. So many people treat IRS suspension like a black box and never really discuss it. I was of the understanding that on the C3 / C4 corvette suspension and Jag type IRS suspensions that use a U Joint half shaft for the driving shaft AND one of the suspension links that a percentage of the torque reaction was pushed out to the knuckles?
And your right I got my link forces backward. I sat down to draw it out and realized my mistake. What can I say, I'm dyslexic and I still get my left and right backwards all the time. I'll leave my post unedited so I can receive my flogging.
I know right now I have a 71 corvette and a stock 88 corvette in my shop both getting work and I've driven both quite a bit in the last few days (buddies cars, they told me to  ). The 71 with its single forward arm (and very short instant center) will squat if you look at it wrong. Stand on the brake and put it into gear and the back end will try to squat, any acceleration with traction will squat hard and the moment you break traction the back end tries to jump from the unloading spring. The 88 (and my past 57's) don't squat like that because of the dual forward arms. The instant centers moved up to the front of the car giving the load a longer lever against the car's suspension. Is that not torque reaction transmitting through the suspension to the tires?
Thanks again
-Russell |
First let me say I am not overly familiar with the differences between generations of Vette IRS designs. I am merely speaking from looking at general geometry.
What you are talking about with one design squatting and the other not has to do with the percent ani-squat built into each design.
Anti-squat is independent of torque reaction. This is completely geometry dependent. The theoretical convergence point of the 2 links forms the Instant Center. The location of this instant center in relation to the CG is one of the factors that go into this calculation. With this in mind if you look under the newer car as you state both arms are point up to the front of the car. On the older design or single arm design this angle is not as steep. With the 2 arms pointed up to the front, when the tires start to roll forward and push the chassis the tires are forced down as they try to drive under the chassis. The reaction to this is actually trying to lift the chassis to some degree. This counter acts the reaction to the torque being applied to the center section. This reaction is trying to lift the front end of the car and because of the moment arm length, the rear goes down. The center section and it's mounting are the only components that are affected by torque. Without this angle, there is less to counter act the torque being reacted from the center section so the rear squats.
These are just my thoughts on what you are seeing. Suffice it to say, I still believe your links will be in compression during acceleration. So, as you are accelerating out of a corner with body roll involved you will be loading those links in compression and bending. Is it going to be a problem? Don't know. Could it be? Yes. Were it me I wouldn't take the chance and just tweek the bar design a bit. I attached a quick sketch of how maybe to change the swaybar mount to stiffen the bar and not worry. Anyway, please don't take any of this as more than some interesting conversation. I love talking about this stuff. Keep up the great work!
