Skidpad Times

[formula_geek]

Hey guys-

I've been mulling over some recent numbers from skidpad testing this last week and am trying to quantify how our car stacks up against the previous year's car as well as data from last year's competition.

I have a few questions:

First off, does anyone recall the approximate temperature on the Friday of last year's competition?

How would skidpad performance vary with temperature? Obviously the data available from Goodyear does not include varying temperature. Can we assume a linear rise in performance with temperature? Unfortunately I don't have access to enough empirical data with the same car in the same trim at varying temps.

Thanks

Travis Slagle
Test Engineer
Kettering University Formula SAE

[formula_geek]

Hey guys-

I've been mulling over some recent numbers from skidpad testing this last week and am trying to quantify how our car stacks up against the previous year's car as well as data from last year's competition.

I have a few questions:

First off, does anyone recall the approximate temperature on the Friday of last year's competition?

How would skidpad performance vary with temperature? Obviously the data available from Goodyear does not include varying temperature. Can we assume a linear rise in performance with temperature? Unfortunately I don't have access to enough empirical data with the same car in the same trim at varying temps.

Thanks

Travis Slagle
Test Engineer
Kettering University Formula SAE

[Denny Trimble]

Here's a simple experiment for ya:
1) set up your skid pad (one direction is simplest)
2) take "cold" tire temps
3) run 10 laps, timing each lap (beacon or lights required) - watch the oil pressure!
4) take "hot" tire temps (tires should reach full temp after 10 laps)
5) let the tires cool back down to "cold" and repeat a few times to try to eliminate driver learning from the data.

You should see a significant performance gain as the tires reach operating temp. It's possible to beat last year's times on hot tires, but at comp it's all about what you do in 2x2 laps.

Your question may have been more about weather than tire temps. It was pretty cold (55deg?) last year. Looks to be warmer this time!

And no, it's not a safe approximation to scale your skidpad times by a temperature factor... linear extrapolation of a nonlinear system is just asking for false expectations http://fsae.com/groupee_common/emoticons/icon_smile.gif

Gettin' excited for comp!
-Denny

University of Washington Formula SAE ('98, '99, '03)

[Michael Jones]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Denny Trimble:

Your question may have been more about weather than tire temps. It was pretty cold (55deg?) last year. Looks to be warmer this time!

And no, it's not a safe approximation to scale your skidpad times by a temperature factor... linear extrapolation of a nonlinear system is just asking for false expectations http://fsae.com/groupee_common/emoticons/icon_smile.gif

<HR></BLOCKQUOTE>

Cold does affect times, but not linearly. Around 65F and higher it's pretty consistent, in our experience - and it gets progressively slower as the mercury dives down from that...at 10F it's not only slow but painfully cold.

Last year was 40F when we ran, which really cheesed us off. We were consitently running sub 5s in practice, and were looking to beat our 2001 record time of 5.083.

We'll try again this year...

---
Cornell Racing
http://fsae.mae.cornell.edu

[GIJoeCam]

I don't have our numbers from 02 in front of me, but I DO know that my times netted us a 5th place finish in the skidpad. The first time around on cold tires it just wanted to push and never settled. I goosed the throttle on the exit in an attempt to generate a bit more heat as well. The second run was only 15 or 20 seconds after I stopped and it made a WORLD of difference. The car took a plant in the first 1/8 of the circle and held it hard for the rest of the 2x2.

I don't have the data we collected during our testing, but again, above about 65 degrees, the car performed pretty consistently. It was right around that temp when we ran and the sun had just gone behind the clouds (much to my dismay) but it still worked out well for us.

-Joe

2002 LTU FSAE Co-Leader
2002 LTU FSAE Brake System Engineer

[Keysmer]

I've read that depending on the tire, performance may be affected by the number of heating/coiling cycles. Have you noticed that? I haven't made yet a test to confirm it.

[Agent4573]

Most tires have a certain number of heat cycles you can put them through before the compound starts to harden. This is basically like buying a harder, less grippy tire. So yes, performance is definately based on number of heat cycles the tire has seen.

[TomF]

During this year's Formula Student event, we did test skid pads on the exact location were it was held during the real event. It was quite hot (some 27 degrees Celsius) and we managed to do a 4.999 run. We did make sure we ran with cold tyres each time to have a fair comparison. Also it was always on the second run that we got the best times, as expected. At the competition, the temperature had dropped to just below 20 degrees and when we were finally in front of the queue, it started to rain just a bit. However we did still manage to do a 5.09 run, so tyre/track temperatures definately make a difference!