Calculation of ARB´s for little Formula cars!

[Dean4.0]

Hello,

i´m new here and i have a question about ARB.

How can I calculate what stiffness in Nm/° of the ARB I need for a little formel car, without high downforce. Like the formula student cars.

The max. Roll has to be 1,5° per g. The Stiffness of the front and rear Springs I now. For example 44N/mm and 45N/mm.

The Motionratio is 1,25

I don´t now if there are any easy formula to calculate it. What other parameter I need?

Sorry for the neebwie Question but im interested in it. Lot´s of books talk about the generally suspension but I found nothing about ARB and the calculation of that.

Next semester I want to go to university and try to join a formula student team.

Thank you for your answer

Dean

[Jersey Tom]

If you know your desired roll gradient, vehicle weight, and rough idea for CG height... you can then determine the total suspension roll stiffness required to hit that roll gradient target. Can include tire rate as well.

If you know the wheel rates and track width (or spring rates and installation ratios in place of wheel rates), you can determine how much roll stiffness is generated by the springs.

Take your total required roll stiffness, subtract the spring component, and you are left with what's required from the bars.

[Dean4.0]

Hey Tom ,

Thank you for that answer. Is there any where on the internet a good site who shows all these things and give few Basic mathe formula?

[Jersey Tom]

They're probably all in racecar vehicle dynamics.. or you could just derive them out if you make a little drawing of a car. It's really simple stuff.

Or.. my suggested approach.. would be to read some basic material like the "____ to Win" series by Carroll Smith, if you want some 'light' reading material before college...

It took me a couple years while working on my engineering degree to really sort out even the basics of how this all works as a system, and why.

What exactly are you trying to do with all this? Seems more than "just being curious"

[Dean4.0]

thanks for that book tipps. Yes sure im very interesting in suspesion and stuff like this. The University i go in september has started with a formula student team. They need people for suspension and ARB. In the get to now week i meet a few people of them and they say if i would work for that team i have to learn the basics (all others too ) and my projekt is the ARB calculation together with an other people.

before that i´ve try to understand the influences with Games like GTR2 and speed of live and other Motorsport simulations.

[mep]

How can you joint the team when you just started on university?
On my university it was just possible to join on the final year and I think its even written somewhere in the rules that you need some semesters until you can join.

For the calculation I think you could get quite far with a simple physiks book and a good technical understanding.
You can writte your idea here on the forum as well.

[Mystery Steve]

There is no rule that I am aware of about freshman joining FS/FSAE, at least not officially. Hell, you don't even technically have to be a member of the university as far as I understand. You just need an SAE membership (in the US, that is... or have the European/wherever equivalent). It's possible that some universities may have their own rules regarding membership, though.

OP: Like Tom said, if you're just starting out, the "To Win" series is a good launching point, particularly "Tune to Win" and "Engineer to Win". Once you've made it through those books and have a basic understanding, you'll find chapter 16 of "Race Car Vehicle Dynamics" by the Millikens to be useful.

Also, I'm not sure from the wording of your question whether you are trying to design the components of an ARB to meet the required stiffness, or if you just want to know what the required stiffness would be so that someone can then design it. If you are actually designing the ARB, it would also be helpful to get a book from your university library on mechanics of materials, and read the chapters on elasticity (stress-strain curves) and torsion.

[Dean4.0]

Thank you all men. I order the books in our library hope they come soon.

@Mystery Steve i do only the calculation how stiff that ARB has to be.