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Thread: Suspension Calculation (Suspension Speed)?

  1. #1
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    Question Suspension Calculation (Suspension Speed)?

    Hello! Does anyone know or have an idea on how to calculate the speed of the suspension or springs?
    Would I take the frequency and convert it to a linear speed (with some algebra included)?
    or
    Would I take the energy transferring through the spring and applying some variant of the General Kinetic Energy equation? This would also include a free-body diagram of the spring and dampers. Caster angle may factor into suspension speed.

    Any ideas or is this calculation useless or redundant?

  2. #2
    GT3 Pilot Schnizz58's Avatar
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    Spring rates are given in N/m/s, so if you know the force applied, you should be able to divide the spring rate by the force and get the speed in m/s. Of course that ignores the dampers, which will resist the motion of the springs. Someone send up the bat signal for Jussi. He's probably down in his basement sniffing his airlocks.
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  3. #3
    WMD Member Jussi Viljami Karjalainen's Avatar
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    What do you mean by suspension speed in this case? What are you trying to calculate?

    Quote Originally Posted by Schnizz58 View Post
    Spring rates are given in N/m/s
    That's dampers. Springs only react to displacement so they are N/mm, dampers react to velocity.
    Quote Originally Posted by Schnizz58 View Post
    He's probably down in his basement sniffing his airlocks.
    I don't have a basement, the bucket is in the backroom. =)

    Reminds me that I "need" to go sniff it...
    Last edited by Jussi Viljami Karjalainen; 09-03-2016 at 22:36.
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  4. #4
    GT3 Pilot Schnizz58's Avatar
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    Thanks for the correction. Something didn't seem right with that after I re-read it.
    97.8% of mass public shootings in the US between 1950 and 2018 occurred in so-called "gun-free zones".
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  5. #5
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    I'm trying to determine the amount of energy in the springs under accel, braking, and average over bumps

  6. #6
    Superkart Pilot Diamond_Eyes's Avatar
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    Quote Originally Posted by B3ntley View Post
    I'm trying to determine the amount of energy in the springs under accel, braking, and average over bumps
    Force = stiffness(spring rate) x distance (suspension travel)

    Integrate this and you will get the 'work' done or the elastic energy, E

    Multiply half spring rate by travel squared to get the elastic energy (work done)

    So a 200 N/mm spring compressed (or stretched) by 20mm, covert to values consistent SI units Newtons and metres

    E = 1/2 x 200,000 x 0.020squared = 40 J

    Interrogate the datalogging to get distance travelled

    Don't know how dampers fit in to the equation as they only dissipate energy and don't store it.....

    Out of interest, energy recovery from suspension travel
    http://www.autoblog.com/2013/08/30/z...ry-suspension/
    Last edited by Diamond_Eyes; 10-03-2016 at 09:23.
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  7. #7
    WMD Member Jussi Viljami Karjalainen's Avatar
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    I think doing that effectively would really require you to be able to log the suspension travel info, and that's unfortunately not something that's fed into the API, so no programs can use it AFAIK. Which sucks, because I would have been using it to make suspension histograms for ages now if it did.
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    My road car OEM style setups (updated occasionally when I find new info) over at P.CARS Setups Database

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  8. #8
    Superkart Pilot Diamond_Eyes's Avatar
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    Didn't realise that travel isn't in the API - you can only see it telemetry HUD. It's a must have datalogging trace IRL.
    We'll grind that axe for a long time... Darrell "Dimebag" Lance Abbott, August 20 August 1966 8 December 2004
    Chi Ling Dai Cheng, 15 July 1970 13 April 2013
    Henry John Surtees, 18 February 1991 - 19 July 2009
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  9. #9
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    More things filed under "games have done this years ago why didn't pCARS do it"...

  10. #10
    WMD Member Jussi Viljami Karjalainen's Avatar
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    Quote Originally Posted by Diamond_Eyes View Post
    Didn't realise that travel isn't in the API - you can only see it telemetry HUD. It's a must have datalogging trace IRL.
    Quote Originally Posted by RacingManiac View Post
    More things filed under "games have done this years ago why didn't pCARS do it"...
    Actually it's my mistake, it wasn't in the original Shared Data API, but it looks like it has been included in the new UDP API. It even looks like there's a straight up suspension velocity value there, so all you'd need is to log those and count the occurrences to make a suspension histogram.
    Code:
      f32   sRideHeight[4];               // 392
      f32   sSuspensionTravel[4];         // 408
      f32   sSuspensionVelocity[4];       // 424
    CPU: Intel i7 2600K @ 4,6 GHz | GPU: Gigabyte GTX 770 4GB Windforce 3 | MOBO: ASUS P8P67 Pro | RAM: 4 x 4GB Kingston HyperX DDR3 1600 | Sound: ASUS Xonar U7 | PSU: NZXT HALE90 650W 80+ Gold | OS: Win8 x64 | Wheel: Thrustmaster T500 RS GT wheel/pedals, Logitech G25 shifter | Monitor: 2x23" IPS-LCD 1920x1080 60Hz & 42" 1920x1080 60Hz | SpeedTest | PingTest | PingTest to UK
    Sim history: IndyCar Racing I & II, F1GP2, Grand Prix Legends, Sports Car GT, Richard Burns Rally, GT Legends, Race/GT-R Evolution/Race On/etc., RaceRoom Racing Experience, SimRaceWay, Live For Speed, netKar Pro, Assetto Corsa, rFactor 1 & 2, among others...

    My road car OEM style setups (updated occasionally when I find new info) over at P.CARS Setups Database

    My Suspension Calculator spreadsheet for Project CARS v1.3.5.2 - Updated on 16.10.2016!

    Suspension Calculator now available on the P.CARS Setups Database website!

    Next Gen = More Biscuit!

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