Stability issues and "how to" on creating .tbc files to match S397 .tgm tyres?

Discussion in 'Car Modding' started by Oskar, Jun 23, 2018.

  1. Oskar

    Oskar Registered

    Joined:
    Jun 2, 2018
    Messages:
    24
    Likes Received:
    0
    I've read through the S397 blog on the tTool, threads I could find on the forum etc.
    But these all seem to assume some basic knowledge of how the tire physics files work and should be setup, that I can't figure out.
    More specifically, I'd like to try out the slicks that S397 have provided .tgm files for. (https://docs.studio-397.com/developers-guide/cars/car-physics/tyre-database)
    But from what I can figure out, the tire dimensions, stiffness, and other aspects are specified in both the .tbc and .tgm files. How does one go about making a .tbc file to match a .tgm file?
     
  2. Lazza

    Lazza Registered

    Joined:
    Oct 5, 2010
    Messages:
    12,345
    Likes Received:
    6,572
    Nearly all the .tbc stuff only applies to AI cars. As long as the .tbc references the correct TGM and has the tyre radius about right you can probably get away with the rest being a copy from whatever source you want.
     
    Vance Le Garde and Oskar like this.
  3. Oskar

    Oskar Registered

    Joined:
    Jun 2, 2018
    Messages:
    24
    Likes Received:
    0
    Ok, that would explain a lot!
    So the AI's simplified model is based solely on the entries in the .tbc file?
    I'm guessing that the Rim= and Radius= entries have some effect on the human driver? And of course the TGM= entry.
    Is there some convenient way to figure out if some other entries are also being used?
     
  4. Oskar

    Oskar Registered

    Joined:
    Jun 2, 2018
    Messages:
    24
    Likes Received:
    0
    The new tire seems awesome at lower speeds and loads. Until the model explodes, crashing rF2. Which happens very very easily at higher loads and speeds.
    This is using the M_30-65-18x11.5_S9M_Slick_2017.tgm tire. The S7M is much the same.
    I happened to get it to glitch once with the suspension outside it's limits, without rF2 crashing. So I got a datalog from it. Speed is only about 230km/h at this point.
    tire-instability.png
    I'm assuming from this that it's clearly the tire having some internal instability, and once this oscillation gets too large, there is some numerical instability that pushes the suspension outside it's range, crashing rF2.
    The tire is probably being loaded outside it's lookup table range. Which I assume is to 6000N, based on Michelin's specs for the real world version.
    But how would one go about fixing this? I tried increasing the VerticalDampingMultipier= in the .tgm [Realtime] section, and also reduceing the InclinationExtrapolation= value. This might have helped a little. Difficult to say. But definitely didn't solve the issue.
    Am I correct in assuming that the only real fix would be to reduce the CalcPointAccel= value, and learn how to recalculate the lookup tables to higher loads and speeds?
     
  5. Jokeri

    Jokeri Registered

    Joined:
    May 17, 2014
    Messages:
    204
    Likes Received:
    32
    Regarding the tbc file, spingrates are used for player too, they affect the ride height of the car.

    Calcpointaccel needs to be lower if you see waves on the tyre when running it in ttool. There is a test number which will show waves if calcpointaccel is too high but I don't remember what it is. The test number is mentioned on the tyre building spreadsheet.
    If you don't have waves then fixing it could be as easy as raising the maximum speed of the tyre.
     
    Oskar likes this.
  6. Oskar

    Oskar Registered

    Joined:
    Jun 2, 2018
    Messages:
    24
    Likes Received:
    0
    Ok, figured out how to open and use tTool a little.
    It's not documented anywhere, but I assume that the realtime simulations use the lookup table that is created with the QSA.
    From looking at the realtime values, the max load goes outside the lookup table, and the extrapolation completely explodes (tire flex of several km :D ).
    So if I understand correctly, as long as the QSA analysis doesn't produce waves or instability areas in the lookup table, it should be good to go with "high" calcpointaccel values? Since I assume they only affect the creation of the lookup table, and not the realtime running.
    Not sure if this is the whole problem or not, but I need to fix this anyway.
     
  7. Jokeri

    Jokeri Registered

    Joined:
    May 17, 2014
    Messages:
    204
    Likes Received:
    32
    Yes.
    The test number for stability is calculated depending on how many temperature/speed points you have. So you have to input info from your tyre into the tyre spreadsheet. For me the test number is 78. My tyre has 4 different temperatures and speeds.
     

Share This Page