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Extracting tyre data from RAF files
(9 posts, started )
#1 - w126
Extracting tyre data from RAF files
Hello,
I wrote a program that extracts some data from RAF files, adds some calculations and produces csv output that may be used to analyse (at least to some extent) the characteristics of LFS tyres. The program is called RAFTyreExtract.

There is also another simple program (MultiDim) that may be used for plotting data from RAFTyreExtract, unless you have a better tool to do it that you are already familiar with.

See the attached picture for an example of what is possible with these programs. It shows FZ50 rear tyre lateral grip vs slip angle for various tyre normal loads.

I hope there will be some people here who may find RAFTyreExtract useful and help me verify if its ouput is correct, especially parts which are calculated and not taken directly from RAF file.
Attached images
sa_lag_nl_c_sr_c_c.GIF
Attached files
RAFTyreExtract.zip - 98.4 KB - 229 views
MultiDim.zip - 114.8 KB - 208 views
Cool, could be very interesting, will give it a look and report back.
#3 - axus
Interesting. Just out of curiosity - how did you work out the grip of the tyre?
#4 - w126
Grip is actually only added for convenience, as it's very simple once you have the forces. I am not even sure if 'grip' is a good name for what it means here.
Here are the definitions:
tyre longitudinal grip = (tyre longitudinal force) / (tyre normal load)
tyre lateral grip = (tyre lateral force) / (tyre normal load)
Yeah grip is easy, it's essentially just how many Gs you can pull.

So far cars without downforce, that formula just gives the mu of the rubber on asphalt.
Hey, nice work. I did the same thing manually using excel a while back but really have enough data points to make it work well.
This basically gives us a convenient way to work out things like tyre load sensitivity.
Would it be possible to see how the tyre model is failing to simulate the grip at low speeds, using this data?
#8 - w126
Low speeds are tricky. You can study the forces at low speeds, but some way is needed of verifying if they are correct at low speeds. It may be convenient to look at lateral grip vs slip angle plots, but there may be different ways of calculating slip angle (and also slip ratio) than one used in RAFTyreExtract. At the moment RAFTyreExtract outputs 'classic' slip ratio and slip angle. Probably for low speeds it's better to use another definition of slip ratio and slip angle, one with relaxation length.
The attachment contains an example. There are strange looking points there (red colour), which are at speeds below 36 km/h. I'm not sure why they look like that. It may be a bug in RAFTyreExtract, maybe it will look completely different when slip angle with relaxation length is used. I checked the replay and these strange red points correspond to very tight turning after a spin out.
Attached images
sa_lag_s_c_sr.GIF
Quote from Frankmd :Would it be possible to see how the tyre model is failing to simulate the grip at low speeds, using this data?

I believe it happens because there seems to be some factor in tire physics that isn't simulated properly in LFS, yet. Like separate treads in tires and their independent bending against the ground. But i'm just guessing anyway..

Extracting tyre data from RAF files
(9 posts, started )
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