6 replies to this topic

[Paolo]

I am currently involved in a research about tyres.
Needing some data, I was extremely pleased to discover the site :

http://www.avonracing.com/frames.htm

from which I could download some very interesting excel files; especially, F3000int2002.exe , a packed file that when executed releases data about F3000 equipment.

I think releasing these data for researchers is extremely generous of Avon.
Only, something seemed odd, and I wrote them for explanations.
Since I got no answer, I wonder if anybody on the Forum can help me.
Here is a "privacy-amended " copy of my questions.






"Dear Mr. ****,
I write to ask some explanations about the F3000 tire data available for download from www.avonracing.com

...

My group is starting a research about tire simulation, and would like to use, for comparison with the analytical formulas I am developing, the tire data Avon kindly releases.

Unfortunately, we are having a problem with the F3000 tire data.
We downloaded an Excel file called Stabfront.xls, wich , as You of course know, represents the behaviour of a F3000 tire in different conditions.
At the moment, our attention is focused on the lateral cornering forces, the values of which are given in the columns marked with CF.

Values are given that vary from 4.90 for a lateral slip angle of -8° to -4.69 for a slip angle of 8°, for a vertical load of 300.

We would like to know the units for these values.

Reading the P96model.doc file, I understand that lateral values are given in Kilo Newtons.
Thus, a value of 4.90 in position C7 of the Data Sheet should indicate 4900 Newtons of lateral force generated.

If this is true, obviously the vertical load indicated as "300" cannot be expressed in Kilo newtons too : I believe Avon tires to be very good, but an Adherence coefficient of 16.33 seems a little high...

A more reasonable coefficient (around 1.6) is obtained if 300 is meant as a vertical weight in Kg...
but then another question arises :

I see data are given for vertical loads of 300, 450 and 600.
I assume these loads, and the related cornering forces, are referred to a single tire.
Now, given the weight of a F3000 car, of about 600 Kg in race conditions, these vertical loads, should they really be in Kg, seem very high for a single tire

It is of course possible to obtain them because of downforce at high speeds, but expecially the 600 figure seems a little high even for the Eau Rouge at Spa.
And it seems strange that no data for the low speed loading condition are given.

Now, I am wondering if our assumptions are correct ...
Is it exact to read the CF values as KN and the load values as Kg ?
And are these values referred to the forces on a single tire ?

We'd really need an answer...

Thank you for your patience and attention.

Best regards

.....

"

[red300zx99]

Is 600kg for a single tire after downforce plausible?

[Ben]

I've used the Avon data as part of my tyre modelling section of my lap time simulation project. I had always taken the data to be cornering force in kN and normal load in kg. It's an odd way of doing it, but it was certainly like that on the F3 data.

Ben

[Greg Locock]

Yes, that's the way I read it. I think the OP needs to check all the documentation, I don't guess at these things (the guys have just handed me a set of data off a car in which one group used mph and inches, the other used kph and mm, OFF THE SAME f....g car and instrumentation setup).

And of course, given downforce etc it is entirely reasonable to test at several times the static corner weight.

[Paolo]

Originally posted by Greg Locock

And of course, given downforce etc it is entirely reasonable to test at several times the static corner weight.

Had it been a structural calculation, I'd agree with the idea of testing at higher loads than the ones actually encountered.

Alas, Avon data provide slip-force curves under different vertical loads, and it would have seemed more reasonable to have the curves for loads actually encountered in service : the only relevant to dynamics calculations. .

Better these data than no data, but it is really strange that no curve is provided for a reasonable low speed load (say, 150 kg) and they bothered with testing under 600 Kg .

I can extrapolate from Avon data , anyway.... there seems to be a general consensus about the units, so be it.


Uh...- Greg , what's an OP ?

[Paolo]

Originally posted by red300zx99
Is 600kg for a single tire after downforce plausible?

Well, I was sure it was not when I started this discussion...
but now I am revising my positions.

I just made some quick "back of the spreadsheet" calculations and found that a load of 600 Kg on the outside rear wheel can actually happen if the car is capable of developing 1080 kg of downforce (calculations are made indipendent of speed)

This with the following data :
Rear track 1.6 m
Center of mass height : 0.3 m
Roll stiffness distribution : 50/50
Weight distribution : 40/60
Downforce distribution : 34/66
Avon F3000 tyres

These data seem to be in the ballpark for a F3000.... so Avon had their reasons for putting 600 Kg of vertical load , on the rear tyre at least. Probably they loaded the front tyre in the same way to allow direct comparisons.

Thanks for your help, gentlemen, it was invaluable as usual.

[Greg Locock]

OP=original poster

Good, glad you agree with them testing at several g, I didn't think it through, just went by the 'F1 cars develop 4g' rule of thumb expressed in another thread.