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Performance Trends Suspension Anaylizer & Methods For Roll Center Calculation...

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  • #46
    Crap, I was organizing pic's the other day and screwed everything up!


    • #47
      Has any concrete evidence been found to answer the original post? Is a Macpherson strut roll center calculated using 90* from the Strut Axis or the SAI?

      Race Car Vehicle Dynamics is not clear on the subject because while it hints at using the STRUT AXIS as a reference for the 90* upper arm by saying to snap that to the desired Instant Center, they are actually talking about the springs and not calculating Roll Center. Deductive reasoning would say that they are suggesting to do the same for Roll Center. Anyone ever read the follow up book, Race Car Vehicle Dynamics - Problems, Answers and Experiments?

      I was taught that it is always plotted using only the pivot points and that the shape of the links or arms matters not. All drawings and explanations I can find on the interwebs always put the strut axis on the SAI which isn't even close to what we run.


      • #48
        The strut is an infinite length collapsible control arm. Imagine the strut axis collapsing @ a 90 deg SA angle, the top of the spindle would tilt in, and the wheel would gain camber very quickly.

        I have proved that camber gain is effected by the strut axis with real world measurement using a digital inclinometer, I'm not sure how to prove that the roll center is also effected. I'll have to think about it.


        • #49
          I use the "it's an infinite length control arm" line on my wife too... doesn't seem to work though.
          '18 Chevrolet Volt - Electric fun hatch for DD duty!

          DefSport Koni Sleeve and Spring Perch Buy!!!


          • #50

            Ok, a friend of mine spoke to a suspension design engineer at Hyundai earlier today and he affirmed that the RC is determined using the SAI and not the Strut Axis.

            The same friend then got the chance to talk to Mike Kojima (considered by many to be the worlds leading S-Chassis expert, who was an engineer for Nissan and TRD) and he concurred with the SAI being used to calculate RC.

            I am sold,... for now.


            • #51
              Thread revival!
              New to NRR, Can someone please confirm, when measuring rear roll centre for S chassis, is the following method correct?

              1.lines joining RUCA inner pivot and outer knuckle joint

              2. (This is where the uncertainty comes in)
              lines joining RLCA ball joint and
              A. RLCA forward inner pivot
              B . RLCA rear inner pivot
              C. A center point on a line joining the forward and rear RLCA pivots

              the above plots the ICís.
              the rest Iím good with.

              Ive attaches a pic.
              3 pairs of red dots show the 3 possible IC depending on A, B and C above