I was reading the physics of racing series earlier today and found a diagram that could prove to be very useful for setups and for figuring out how to get the best out of your car. A traction budget diagram allows you to see what is the maximum acceleration the car can achieve in a certain direction... and also if you have to apply brakes to get the best out of the car around a corner, like the one in the diagram... Could InSim data be used to generate such a diagram? For instance, you have to complete certain tasks like drive around the skidpan at various radii trying to get the best out of the car (which is one of the first tests a new race car has to pass when it is designed). I would love to look into this myself and help with it but unfortunetly I don't have the necessary software to develop the programme. Would anyone be interested in working on this project? I would read up and help from a physics point of view.

If the Insim data provides instantaneous longidudinal and lateral overall G, then a traction circle could be made. Then you just run a few WR hotlaps through it to get good extents (i.e. roughly how much each car generate). Then other people can run their hotlaps through it and see how much they are using their tyres compared to WR.

If the forces for front a rear tyres can be made as well, then you can have the graph as in your link, with separate traction circles for front and rear tyres.

Just a shame I can't program, as stuff like this would be so interesting.

InSim does provide continuous longitudinal and lateral acceleration - gMeter had a display showing this... you could make a circle of what is being used but that isn't necessarily the limit of the car I guess... for instance, the car would never use the maximum amount of forward longitudinal acceleration on a single hotlap. Would slip angles help to find the actual limit and then you could compare what you are using to the limit rather than to what someone else uses? The other thing that this allows you to do is compare setups. I know slip angles are a part of RAF files... not sure if they are in InSim data. Anyone with the physics knowledge to tell us how to find the actual limits of a car?

Well, maximum forward long. acceleration is anytime when the car is in a reasonably straight line and the acceleration is limited by wheelspin. I'd have though that most WR hotlaps in most cars (apart from the under powered ones) would get somewhere near max accel in all directions - thats why they are WR, cos they have exploited as much grip as possible.

I don't see many a WR with more than .6g in a straight line - especially in the road cars. Maybe in the race cars but even a Raceabout I doubt would hit the limit of fowrard acceleration. And we can already plot Lateral acceleration on one axis and Longitudinal on another using an RAF file and f1prefview.

Here is a sample (based on the WR for Blackwood FZ5)... sure makes a nice "traction budget diagram"... not gonna learn much from there.

And could you not do something similar with it, like this? (see attachment). All you need is a system to find out if you've exceeded the grip, and therefore ignore any resulting acceleration data.

Also, tractions circles are rarely round

Edit: Actually, I'd make the lower curve a bit smaller - so that the values in the bottom left touch the curve rather than being a few mm away. This means that the wheels lost grip a few times under braking and in the turns momentarily.

Well, you can get wheelspin, if not from InSim then certainly from RAF files. Now we need to get a programmer guru interested... see what we can come up with - Bob?

InSim can only get acceleration data for the car, not individual wheels. It is entirely possible to log all the data received and create a CSV file for further analysis in Excel or something.

RAF outputs are much more detailed and include intruiging things like slip angles. It's best to create something that analyses this data rather than InSim based, unless you particularly want something that is live when driving.

Edit: Just realised I was thinking of OutSim, so I could have been talking out of my arse there.

So....
How's the weather...?

Is anyone capable and willing to write such a programme? I would look into it but my programming skills aren't on that level now for one thing and for another I have no access to the necessary software at the moment.

What the traction budget basically is is the maximum acceleration your tyres can achieve in different directions plotted relative to the origin (which is obviously 0 acceleration). Up is forward acceleration, down is braking, left and right are lateral acceleration. The problem is that it is not a simple equation, nor is it just a circle or elipse. Grip is basically the coeficient of friction between the tyre and the road, which can be calculated in the following way:


Since your longitudinal grip normally decreases as you use more lateral grip, the way to go about this is probably to use the skid pan - it is flat and you have lines for diferent radii. You can take your car around a certain circle starting at say... 40kph and slowy increasing the spead until you reach the maximum the car can do. I will post a replay of what I mean with an RAF file later. From there you can plot maximum longitudinal acceleration against all the different lateral acceleration values. This is all that the traction budget diagram is - lateral acceleration on the x-axis and longitudinal acceleration on the y-axis. The graph should be symetrical around the y-axis (or close enough to it - maybe slightly more can be achieved in the direction of the driver side in a car which doesn't have the driver in the middle). Lateral acceleration under braking will be a bit more tricky as the graph is not symetrical around the x-axis... maybe BobSmith and tristancliffe have some ideas?

Here is some test data. The layout I used is based on the throttle control lesson layout - basically I added an extra route with a short starting straight on which to accelerate into the layout. That straight contains the starting point, a checkpoint and a finish line in that order (you can only get RAF output from lap 2 onwards, so you have to do this). You drive round and round, slowly increasing speed and warming tyres, until you feel you are at the limit. Then there are cone indicators on the outside - 2 orange, 2 yellow and 2 green. The 'escape route' leading back to the finish line is between the two green cones. Once you are finished driving get the RAF output for the second lap. Unfortuantely I can't seem to upload the RAF because it is some 4MB (2.5min replay), so you have to do this yourself - the increasing replay speed doesn't seem to affect the RAF so you can just play it faster.

EDIT: Perhaps it is best to draw the apparent traction budget for each tyre at first, then we can work from there. Don't try to draw an overall diagram yet.

what name of tyre program plz

There has been no tyre program used in this thread?

The traction budget depends on the tyers temp as well as compound and contact area of the tyre with the surface and indeed the road surface make up. Then there is also the weight of the car and the addition of aerodnyamic downforce that is placed on the wheels as well.

So grip level can change for many differnt reasons, thus the graphing of this data can be EXTREMELY variable from one run on the same set of tyres vurse another, and between cars types.