FSAE Tire Test Consortium -- Round 3

[Edward M. Kasprzak]

Scott,

Yes, I replied to you, but the mailer-daemon couldn't deliver it to your address.

[Edward M. Kasprzak]

Milliken Research has been contacted regarding problems with the aligning toruqe expansion. We've scheduled it among our current work and hope to have a resolution next week.

[simon_o]

Hi,

I just started using the tire data from FSAE TTC. I am building a vehicule dynamics model but I am not sure in wich direction is the FY returned by the MRA Nondimensionnal model. Is it always perpendicular to the belt displacement or is it in another direction (perpendicular to the tire) ?

Does anyone can

[VinceL]

simon_o

The MRA models follows the SAE tire axis system. That means that lateral force is perpendicular to the wheel heading direction and positive to the right. It doesn't matter what the slip angle is or how the tire is distorting. The only thing that matters is the wheel.

[simon_o]

Ok thank you!

[GooDLuC]

Is it me or the "camber effect" on lateral and longitudinal loads is reversed for the Goodyear tires?

We plotted a graph showing FY vs SA for a given FZ and various camber. According to SAE tire axis system, negative IA should produce a negative FY @ SA=0 but on the graph we find a positive FY @ SA=0. Also, we can see the tire generate FY load for IA=0 while other tires generate nothing @ IA=0.

On a second graph showing FX vs SA for a given FZ and various camber. The graph shows that the higher the SA, the higher FX is. This don't really have sense.

Am I right? Could someone tell me how to correct this problem. I looked at other tires (round 1, 2 and 3) and "camber effect" seems to be right for those tires.

Have the runs 53, 54 and 55 (with the tire in the backward direction) been included in the tire modeling process? Should we take into account the comment in the DVD content file (reverse sign for SA, IA, FY, ...) when using the MRA model or have this been done already when generating tire model?

Thanks!

[FryGuy]

I don't think you are allowed to post those on the internet as of tire consortium contract.

[GooDLuC]

FryGuy, you're right... I forgot about that. I removed the graph. I hope my post will be clear enough without graphs.

[FryGuy]

I would re-check all your graphs, they didnt exactly look right to me. That tire at certain loads does have some interesting camber effects but it still seems like your graphs didn't quite look right. They could be right but i didn't get a real good look at them before you removed them.

[GooDLuC]

Hi, I investigated a little further and now I think FX curves for the Goodyear tires have sense.

However, I still can't explain the FY curves behavior.

For exemple: with a 250 lbs vertical load, SA=0 , IA from 0 to 3?) I got:

*0 FY force for IA=0 (which have sense)
*an increasing neg. FY force as IA from 0 to 1 (which is in opposition of what would "normally" happen with other tires)
*an increasing FY force in the pos(+) direction for IA from 1 to +... (which correspond to the expected behavior of a tire).
*For negative IA, the same happen but with sign reversed for FY.

I also plot the same graph with the raw data of run 4 and 54 and what I see is FY going positive as IA increase (expected behavior).

I saw a lot of hysteresis on raw data graph i.e. for IA=4? tests pass trough SA=0 four times and 2 curves indicates a lot of FY+ and the 2 others indicate approximately 0.

I don't know where the error come from but I would appreciate if M. Kasprzak or M. Milliken could take a quick look at the Goodyear tires models vs Raw data and told me why I get these results and may be help me to correct the problem if possible.

Thanks!