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Thread: the chassis height and C/G

  1. #1
    Junior Member
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    the chassis height and C/G

    what is the optimum clearance between the lowest member in chassis and the ground ?
    Is 80mm a good clearance ? and if i make the clearance lower is that will make the C/G lower ??

  2. #2
    Senior Member
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    If you reduce the ground clearance by reducing the ride height and leaving everything else as it is, obviously the CG will drop by nearly the same amount as you lower the Chassis (a bit less as the unsprung weight will stay where it is).

    In General you want the ground clearance to be as low as possible while making sure your car doesn't hit the ground while driving. How much ground clearance you Need to achieve this? Well it's up to you to find out ;-)
    Rennteam Uni Stuttgart
    2008: Seat and Bodywork
    2009: Team captain

    GreenTeam Uni Stuttgart
    2010: Seat and Bodywork / Lamination whore

    Formula Student Austria
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  3. #3
    80mm is generous clearance for a good FSAE car, as 100mm clearance is the legal requirement for road cars.

    "Optimum" clearance is 57.367mm, from chassis to ground.

    Then your underbody aero takes up half that gap and scrapes along the ground.
    University of Tasmania (UTAS)

  4. #4
    "Optimum" clearance is 57.367mm, from chassis to ground.

    Jonny: Where did that number come from?

    Forbes

  5. #5
    I pulled that number out of thin air. He wanted a number, I gave it to him. But 57mm wouldn't be such a bad place to start.
    University of Tasmania (UTAS)

  6. #6
    Quote Originally Posted by Jonny Rochester View Post
    I pulled that number out of thin air. He wanted a number, I gave it to him. But 57mm wouldn't be such a bad place to start.


    Build the car, stand in it, jump up and down to jounce it (with a calibrated 80kg human). If the car bottoms out before the limit of travel it is too low, if it does not, it is too high.

    57mm is an unfair number as it should be a function of your suspension stiffness. So it's more like 57mm - (K / 500) +/- M where K is kg/mm of wheel rate and M is 5mm and positive or negative depending on if the driver's helmet visor has been properly de-fogged.
    Kettering University Vehicle Dynamics
    Formula SAE 2010 - 2015
    Clean Snowmobile Powertrain 2012 - 2015

    Boogityland 2015 - Present

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