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Mats
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Traction circle diagrams (data aquisition)

Post by Mats »

Hey gang

Thought you might be interested in some traction circle diagrams from my racecar. These are from race laps so you they are not always "perfect laps" i.e. some transitions or curves are stressed or cars are in the way and so on.

Gelleråsen: Link to Google video
Image

Knutstorp (you know, the twisty one with the elevation changes): Link to video
Image

Sturup: Link to video
Image

Kinnekulle: Link to track video
Image

Another lap from Kinnekulle, note the difference in the line indicated. Guess what that is...
Image


Anyway, I thought you might be interested and might be a nice discussion starter. :)
Last edited by Mats on Tue Oct 16, 2007 10:13 pm, edited 1 time in total.
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Post by MALDI »

Is each plot one full lap? No more, no less?
'84 GTV6 3.0L
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Mats
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Post by Mats »

Yep.
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Post by x-rad »

is the point to have relative smooth plots and to track your progress towards smooth plots?

It certainly looks like you got better towards the bottom..
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Post by Maurizio »

You're not doing very well in art class :lol:
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Post by Barry »

You got to keep the kids away from your stuff!! 8) :D
French cars are shit and shit expensive to service and bloody awful and unreliable and expensive and friends don't let friends drive french cars and you wait years for parts.
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Post by Greg Gordon »

Mats, those are some very impressive numbers. Obviously your car can really corner. It's braking and accleration numbers are impressive to. A lot of people talk about how well thier car corners, I think you are the first one here to back it up with hard data. Good Job!
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Post by Mats »

Thanks Greg. Yeah, as you know hard data is paramount when you are trying to figure out what is happening.
Basically you only need a stopwatch to realize that the correlation between what you think is fast and what really is fast hovers around zero. 8)

Next step is to get some software that creates a virtual dash to overlay on my videos, that will be interesting. Get one of those g-bungycord-diagrams as thay have in the F1 broadcasts and tach/speedo.
I was a bit suprised to see in my logs that my speed at Kinnekulle when I turn in under the bridge on the straight is actually over 160Km/h, I was quite certain it wasn't over 140Km/h (remember, I didn't have a tach until recently).

About the plots in my first post, the idea is to use all the available grip during the transition from braking to cornering, ideally you want the plot to follow one of the circles. For instance, if I can brake and corner at 1.2g the plot should go from full brake, follow the circle to 1.2g at full cornering. That means that you will have to release the brakes at a perfect rate during the turn-in, not an easy task (but the F1 drivers seem to be able to nail it every turn...)
The tracks we drive are seldom just corners with a straight leading up to it though, usually there are a lot of stuff going on at the same time and that's why you can see strange loops from when I brake in a long corner for instance.
The "weirdness" in the last graph is from a lap where I actually go from the left hander under the bridge to the loong right hander without going straight in between, the braking have to be squeezed in there somewhere and that's why you see the large hump with the little twist on it.
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Post by Greg Gordon »

You are right about the correlation about what you think is fast, and what really is fast. When I drive the Fiat 600 up through second gear to 8000rpm and go through a corner with some leaning and a little oversteer it feels so fast it's downright scary. Then I look down at the speedometer and realize I am really not going very fast.

I wasn't really looking at the transitions on the traction circles. That's more of a driver's skill measurement than anything, now that I am looking at it it looks like you can really drive that thing. I will watch the video soon.

Looking at the cornering and braking limits shows the car can really corner. It pulls 1.2Gs of lateral acceleration over and over. I know that's with race tires on a race track, but still...it's impressive.
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Post by Mats »

If you look carfully it's actually almost 1.6g lateral on Knutstorp. 8)
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Post by Greg Gordon »

I didn't see that until you pointed it out. That's a huge number for any car, not to mention something from the 70's!
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