Ackermann

[David Pozzi]

Bobby,
Great comments! Can you describe your testing methods? I assume you use a skidpad and vary toe out/in to get the best lap time, then modify the linkage to incorporate that amount of ackerman change? How many different corner radius do you use?
David

[B_Alley]

Thanks David!

Yes, we used test method: bunch-o-circles, aka, skidpad testing. It was for a small formula car, so the radius were quite a bit tighter. We did 25, 50, 75, 100 and 150 ft radius circles (dont see more than that in autocross, at least at nationals) We also had a slalom that we'd test different settings on. We actually kept pulling more and more g's with larger the radius (we run aero) but Gs at 75 and 100 ft were the same, and at 150 ft it was less. This is because the steering geometry we chose was not suited for this big a turn. We had made toe plates that attach to the upright that allowed us to choose different ackermann settings.

One thing we used to do, set the car up for parallel steer, then run different toe settings on different radius' circles to see what works best. Then design a system that achieve the best of both worlds. I'm not sure how much you can alter these systems by shimming things, I'd have to take a look!

We absolutely rely on data acquisition to see what works best, especially for the slaloms, watching what the driver is doing and how the car is reacting.

Does that come close to answering your question?

[David Pozzi]

Thanks, I wish I had access to somewhere to test, it would help so much!

[B_Alley]

Haha, I don't know where your located, but if your in California, Buttonwillow Raceway, near Bakersfield has a good 300' skidpad that I'd love to test some cars on! Rental rates arern't too bad.

When we couldn't get our practice track, we always just snuck out to a nearby church or Homedepot at 1:00 in the morning!