Any Suspension/physics Gurus Out There?!

[brumster 135 1 Cars]

A slightly diverse question, but I think it's in the right section to target the people I need...

 

I'm building up a real-life rally stage in a PC simulator called rFactor - a stage of the Rally of the Midlands - and once that's done I'd like to model my 205 stage car so that you can drive it in the sim. The sim is very, very detailed and in order to accurately model a vehicle you need to configure various aspects of the suspension and chassis. Some things I've no idea of, some things I could work out or possibly find in a Haynes manual, but I think it might be good to ask on here if anyone has any ideas.

 

If you specify any values for me, it would be good to know whether it is DEFINITE or an ESTIMATE, and also to what model of 205 it applies (if it differs). I am primarily after values that match my stage car, not a standard car - so that's a 1.9 but with adjustable Grp.A lower front arms, 309 shafts/steering arms/ARB (309 track, basically), bilstein coil-overs on the front with forest inserts and tarmac springs, and a 205 rear with 23mm torsion bars, standard ARB and 3-way Proflex. The latter I appreciate can be twiddled to whatever I have it set to, but some ranges would be useful.

 

Here's the fields the sim accepts/requires :-

 

Wheelbase

Mass (inc driver, ex fuel)

Front/rear weight distribution

Height of CoG

Track (front/rear)

Roll centre (front/rear)

Camber (front/rear) - front I have

Roll camber rate (deg/deg) - front/rear - amount camber changes per degree of roll, I assume body roll

Ride height front/rear - again something that's variable given the setup of the car, but standard will do for now

Bump travel front/rear - amount of bump travel

Droop travel front/rear

Kingping inclination

Scrub radius

Castor

Trail

Ackerman angle

Anti-dive as a %age (not sure what relevance or measurement this physically relates to; an angle from the centreline of the wheels to the steering rack maybe?)

Steering arm length

Anti-squat for the back (again as a %age)

Front/rear spring rates (N/m)

Compression and Rebound (front/rear) as N/m/s - low and high speed configurable for stuff like the proflex, although I suspect the front bilsteins aren't that fancy

Transistion speed (m/s) of the damping :S

Motion ratios of the wheel to the spring - thinking near direct at the front, but the back I've no idea

Effective rollbar length front/rear

Effective rollbar level length front/rear

Outer diameters for roll bars

Inner (if any were hollow, which I don't believe they are?)

 

Nasty stuff, as you can see. Not expecting answers to all of them, but any thoughts will always help. A lot of it I suspect I can 'fudge' by changing, testing how the car handles, and tweaking one way or t'other so it's not the end of the world if we can't figure them all out. In addition, limits of the game mean it can only model double wishbone or a live axle type arrangement, so essentially a lot of the values need to be 'fudged' in for a car like the 205, so that it handle as similarly as you can get it. There is no direct way to model strut suspension, or trailing arms so some of the above may be irrelevant anyway. Hey, let's get the basics first

 

Cheers,

Dan

Edited August 14, 2008 by brumster

[brianthemagical 1]

Most of the will need to/can be measured on your car and altertions in some areas, like the wishbone dimensions, will alter others, like track, roll centre, roll camber rate, KPI, scrub radius and scrub, caster and trail.

 

Motion ratio on the front is 1:1, as i think the rear is.

 

All of them are easy to find if you know where to look. Best bet will be to find some books on the subject otherwise you'll have no idea what the alterations you make will be.

 

Dampers give the manufsctures a call for the intended dyno graphs of the dampers.

 

Sorry there's no actual values in the above.