Help need in car physics model

[c00ler]

Hi Guys
I want to create online F1 simgame, something like F1 manager from EA.
I have strong expirience in web developing (f1grandprixmanager#com)
but i'm almost 0 (zero) in Physics.
So i need an adviser who will help me to create simple car model for my game.
If anyone can help drop me an email

Regards
c00ler

[pompelmo]

Oh My good!!
I'm a student of physics...You want me to explain a simple car model???? You know that is not so simple as you think!! I could explain this to you giving you lectures for a least a month!! 1st I You have to know basics in physics!!

[c00ler]

In principle all i need is some formulas, i have enough skill to understand what which formula calculate. I do not care how
For me its more than enough to programm it.

Sometimes ago, one man created a model for me and its worked.
But need to add several parameters there.
Problem is that, this guy has dissapeared somewhere (one year of silence)

Also i dont need EXACT formulas.

Maybe you will be kind enough to help me.

Regards

[pompelmo]

give me a day or two!

[c00ler]

give me a day or two!

Thank You !
Do you need formulas that i already have ?

Regards

[pompelmo]

no thanks

[pompelmo]

sorry bt you'll get them probably in thursday (I forgot my books in campus)!!!!

[pompelmo]

oh..yea..I'm also a graphic designer if ou need some help with that!!!

[c00ler]

sorry bt you'll get them probably in thursday (I forgot my books in campus)!!!!

No problems, i'm not a God to create a world in 7 days

oh..yea..I'm also a graphic designer if ou need some help with that!!!

Very nice, but our first mission is physic model.

Regards

[Pacifist]

Hey i am also currently working on a car physics engine. If all you want to do is a flat ground physics it is really easy. Check out this site below, it covers everything about modeling flat ground car physics (plenty of fancy equations). The site is really good overview of the physics involved, and it is probably exactly what you are looking for here. However it does leave it to you to actualy impliment it with your model.

http://home.planet.nl/~monstrous/tutcar.html

hope it helps.

~Peace

[c00ler]

Thanks for link !

Regards
Max

[ReubenG]

The website posted is mostly correct, but I noticed one significant error /anomaly(which the author hints at strongly). The author mentions rolling resistance (Frr) but the form in which he presents it is very different from anything I've ever seen. I know that rolling resistance is a bit of a "black art" and there are some very dubious descriptions published on the web, so feel free to present a better model than the one I will give.

The website says:
Frr=-Crr.V (where V=velocity and Crr is the coefficient of rolling resistance and he "claims" a value of 12ish which he even says is dubious).

What I have seen (and used in acceleration modelling before)

Frr=-Crr*N (where N is the normal reaction, or the sum of the weight and downforce)

Crr= (Cro{p} + Crv{p}*V^2.5)
The {p} imply that the coefficients CRo and CRv are functions of tyre pressure - my model used to look these up from a table I was given some years ago. I think the table comes from Miliken & Miliken's text on vehicle dynamics. The functions I obtained from it were essentially linear decreases - i.e. as tyre pressure increases the coefficients decrease.

Now, why I believe that the model I used is "better"
1. It takes into account the normal reaction between tyre and road - it makes sense that ceteris parabis a heavier tyre will have more rolling resistance that a lighter tyre.
2. The rolling resistance is a function of tyre pressure, and higher pressures give lower rolling resistance, which again makes physical sense. In the extreme, a tyre with very high pressure will become very rigid and hence easier to roll than a tyre with very low pressure, which deforms hugely.

I had a look at my rolling resistance numbers - Crr had a range from 0.012 to about 0.018. So if you have a car with a mass of 1000 kg, it takes about 12-18 kg force to overcome rolling resistance. These seam reasonable as my car weights about 1000kg and I can easily push the car from a standing start on a flat road.

Hope this helps rather than complicate your life.

[c00ler]

Hi ReubenG
Thank you for your amendment !
I hope that pompelmo use it.
wanna join us ?

Regards

[pompelmo]

this maybe a stupid question but where does the rolling resistance vector point?? (in the oposite way as the speed??)

[pompelmo]

For c00ler:
Fdrag = - Cdrag * v * |v|
If you don't know:
v=(v1,v2,v3) => |v|^2=(v1)^2 + (v2)^2 + (v3)^2
v1,v2,v3...components of the vector
you'll probably use v1 and v2. v3 is minimal (v3=0) if you use the third
dimension. As I saw from your code you don't use it!!