Springs & Dampers, Part Two

by | Feb 9, 2018 | Tech Tips | 2 comments

Springs & Dampers, Part Two


  1. Tyler McAllister


    Our formula SAE team is building an excel sheet and we are wondering about the ARB motion ratios in the Part 2 Tech Tips: Springs and Dampers. Is the motion ratio measured as wheel displacement/ARB displacement? We found the equations in Race Car Vehicle Dynamics on pg. 599 but they express the total ARB roll rate as a different formula.

    We also have another question about the Total ARB Roll Rate Needed formula. We are under the impression that we should use the wheel rate for the front of the vehicle and the Magic Number will then help determine the stiffness for either the front or the rear respectively using the Front Anti Roll Bar Stiffness.


    • Ariel Avi

      Tyler, the ARB displacement should be determined by your own measurements and reference system. The ARB motion ratio measures the chassis motion w.r.t. the ARB twist. You can use whatever number/convention you want, as long as you keep the consistency and do not make any absurd math along the way.
      The Magic Number is just the roll stiffness ratio between the front and rear axles. In that case, not only your ARB, but also your springs and the Roll Center height would enter the equation as well. Be sure to check if there are any seminars near your area to learn much more about the subject!


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