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New File Added: Bilstein_damper_courves

Discussion in 'Racer' started by Alexander Knoll, Oct 29, 2010.

  1. Alexander Knoll

    Alexander Knoll

    Downloads: A new file has been added by Dream Factory:


    Bilstein damper courves for Racer.
    Made by Engine of Darkness.
  2. Alexander Knoll

    Alexander Knoll

    THX EoD! I hope it's ok that i post them here!
    Yes i use them, because i never could do some better...THX for them!
  3. Remember that the motion ratio of the suspension will impact these curves!

    Not that that is a big problem, we can just open the curve and multiply the values by the motion ratio using the Scale in the Y axis :D

    Thanks for posting!

  4. I never really cared anyway, anyone could do them in about half an hour or quicker.

    Care to give an example? Much less for me, as I'm pretty much not doing anything for racer, but for other people who might decide to use them.

    I for one never understood how to calculate Motion Ratio, I never understood anything about it at all. Is that the frequency with wich the suspension moves (I guess not else what sense would a stiffer dampener do if you soften/ harden it based on the suspension frequency)?

    Maybe I'm the only one, but one big problem I had back when I did do inis privately was that I never understood some more advanced stuff because it was written all technical instead of giving two examples with different values where possible so I could draw my own conclusions.

    So I resorted to trial and error till it felt right, but it didn't feel right to the point where I'd say "yup that's it". It left some bad aftertaste for every ini I made for myself or for some people.
  5. The motion ratio is a little like leverage.

    If the damper is mounted half way along the suspension arm, then it travels at a lower speed than the wheel itself, thus it also deflects less.

    Think of it like a see saw with a fat person at one side and a thin person the other. To get it to work the fat person moves closer to the pivot :D

    Racer assumes all our springs/dampers are at the wheel hub, but they are not, so we need to compensate for that when using real data.

    Ratios change a lot, but my BMW M3 ini file refers to the installation and thus motion ratios in there, as a guide.

    McPherson struts are often around 0.99 > 0.9 or so, while multi-link and wishbones might be down nearer 0.9 > 0.5 or so...


  6. In the simpler suspension designs you can pick it up straight from images.

    Well, assuming you have a picture of the suspension, anyway... Just mark where the spring/damper attaches to the suspension, and where the suspension attaches to the frame & hub.

    Here the spring/damper is mounted about 60% of the way along the arm, compared to the wheel, so it's going to travel 0.6 times as far as the wheel. To compensate for this you just multiply the forces by 0.6, and any length limits are divided by 0.6 (so if it has 10cm of travel, 10/0.6 = 16.7cm)
  7. http://en.wikipedia.org/wiki/Motion_ratio

    To get the factor change on the rates though (damping or spring), we need to square the motion/installation ratio.

    So wheel rate = spring rate/motion ratio.squared
  8. Here are the three sachs dampener curves I spoke of

    Attached Files: