It's good to see some sensible points have been raised in this discussion.

Tim to your question on suspension configurations that aren't modelled in ChassisSim. Definitely the lookup table is certainly an option and I certainly haven't ruled out but given the past experience I have discussed I've been very gun shy about implementing about it. That being said in the code in ChassisSim it's really easy to add new suspension geometry configurations and I've done this for suspension configurations such as the F458 rear end and the BMW Z4 link. In this regards a K&C rig is worth it's weight in gold because it allows you to validate what you have come up with. This was really useful when I was developing the F458 rear end.

One thing I do need to touch upon is ChassisSim modelling process. Tim the technique you discussed is pretty much on the money except for the whole fudge factor thing. Yes you do enter parameters such as spring rates, damper curves, pick up points etc to construct the vehicle model. Once you have your data from a flying lap that's where the tyre force modelling comes into play.

The basis of the tyre force modelling toolbox is that using the multi body vehicle dynamics model in ChassisSim to do a whole bunch of track replays to minimise the difference between simulated and actual lateral acceleration. This is where the transient vehicle model comes into play because you can now do the bumps you can get a much better idea of what the loads are. This is where the reliance on fudge factors falls away.

A good question that was raised is how good does the data need to be? Obviously the better the driver the less work you need to do. However given the nature of the track replays if you do have a so so driver you do have something to work with. Let me give you a war story. A couple of years I was doing some work in a junior formula in the states. When I went through the tyre modelling process it was predicting lap times 1s a lap quicker then what the drivers where doing on the home circuit. I made a mistake and trusted the race car drivers. When they went to Sebring they get blown away. After finishing tearing my hair out I reset the grip factors to where they should have been and all of a sudden the car was doing lap times in comparison to the front runners. The moral of the tale is you can get significantly down the road with race data. Also here is your game plan on how to do it,

http://www.chassissim.com/blog/chass...-in-the-blanks

The senior members of the ChassisSim community have found this to be a really useful resource and I recommend it to you.

Also make no mistake this is an iterative process. It will take a couple of goes to get it right. Also everything we have discussed here has been used in formulas as diverse as GP2, Sportscars and V8 Supercars to name a few. Given the results my customers get I think the validity of this approach speaks for itself.

Also just a word on accuracy and lap time simulation. I totally concur with Claude that your goal in simulation is not the correlation game but ensuring what the car does the simulator does. That being said one of the things we have found in the ChassisSim community is that the better the tyre model the accuracy tends to look after itself.

Great food for thought.

BTW - For the Australians and New Zealanders reading this - Lest we forget have a good ANZAC day.

All the Best


Danny Nowlan
Director
ChassisSim Technologies