F1 roll stiffness values?

[boyracer]

Hi, I am doing some vehicle dynamics calculations on an F1 car to determine the sort of loads I can expect on tyres under cornering. I need approximate values for the roll stiffness of both the front and the rear of the car. I know that these will vary considerably depending on the track and setup, though I am trying to model a fairly stiff front end and a softer rear end and am looking for some ballpark figures. Haven't had any luck trawling through the internet and various resources, was wondering if anyone here had any better ideas?!

Thanks!

[Jersey Tom]

Why stiff front and soft rear?

[boyracer]

I'm modelling this for the Silverstone circuit - according to information I found on the F1 website, most teams tend to run their car with a stiff front end and a softer rear end around the track. Hence trying to find approximate values for a stiff front end and softer rear end.

[Jersey Tom]

Stiff in what regard though? Stiff springs? Stiff bars? Stiff tires? The thing's still gotta be balanced.

Modeling this for Silverstone.. but what's the end goal? What are you trying to achieve? Doing it just for the hell of it?

You could suppose that the TLLTD and aero split are roughly proportioned (or inversely proportioned) to the static load distribution and go from there.. the absolute values of the roll stiffness aren't really as important as the relative split between them.

[Tim.Wright]

I'm modelling this for the Silverstone circuit - according to information I found on the F1 website, most teams tend to run their car with a stiff front end and a softer rear end around the track. Hence trying to find approximate values for a stiff front end and softer rear end.

As a general rule, your roll stiffness will be front biased. Typically your total load transfer distribution is designed to be about 5% higher than your front weight distribution. This requires higher roll stiffness at the front.

If we make some assumtions:
mass 605kg 40% front
CGh 220mm
track 1400m (avg)
Ay 5G (copse and becketts)

this gives weight transfer of:
(5G x 9.81 x 605kg x 220mm)/1400mm ---> approx 4660N

If we assume this is distributed 45% front by the suspension design, your wheel loads are;
3284N -909N
4343N -782N

Add 1500kg of downforce equally to front and rear:
17999N 13805N
19058N 13932N

Oh and to answer your original question on the roll stiffness. to get the load transfer distribution of 5% higher than the weight distribution your roll stiffness will divided front/rear in a "similar" proportion. So that would be 45% front.

If our car above rolls 2.5deg at the said 5G, then your roll stiffness is:
roll moment of (5G x 9.81 x 605kg x 220mm)/2.5deg
2611Nm/deg

with 1175Nm/deg at the front (45%) and 1436Nm/deg at the rear.

This is a very basic calc which doessnt take into account different track widths front and rear and roll centres are assumed on the ground. In addition to this I havent checked to see if its actually correct!

You should be able to confirm these numbers to yourself after a little research on roll theory. I canät think of any net resources for this right now though.

Tim