Enter your username:
Do you want to login or register?
  • Forgot your password?

    Login / Register



    Results 1 to 3 of 3
    1. #1
      Join Date
      Jan 2022
      Posts
      88

      Roll Center Tech of different axle centering strategies

      Where EXACTLY is roll center determined when a panhard bar is used? Lot of conflicting information out there.
      I've done a TON of research on this topic and can vaguely answer it myself, but I wanted to get some info from some nerds out there who may steer me in a better direction than what I believe to be the case.
      I've seen 3 different answers to this: the mount point on the axle (makes the least sense because no factory cars mount a panhard in the middle of the axle apart from spring cars maybe), the center of the bar REGARDLESS OF MOUNT POINTS (kind of makes sense for a bar mounted equi-distant from frame to axle center and center to axle mount, more or less idiot proof too),
      And finally the one that makes the most sense is where the bar intersects the centerline of the vehicle. Speedtech uses this strategy in their torque arm setups, the panhard bar isn't completely centered in the car (axle mount is not directly under the frame on the pass side)

      I figure the axle-centerline intersection makes the most sense in a theoretical setup where the bar is level at ride height.
      I built a 3 link/watts link for my 69 chevelle, after copious amounts of pondering I will be cutting it out and using a panhard bar setup. Because weight, simplicity, exhaust out the rear bumper of the car, less wearing parts.
      Ill post pictures of the watts; it won't work WELL for autocross. My geometry is baaaad.

      Note to self fellas, a tape measure and bubble level isn't quite enough to back-half a car.
      Theres never enough time to do it right once but always enough to do it twice. I wager the second rendition is always better than the first, regardless of what you're building or how much $ you're throwing away from the first try.

    2. #2
      Join Date
      Apr 2007
      Posts
      193
      My learning has it that it is where the bar crosses the axle's horizontal centreline. Therefore it could vary an inch or two over significant travel.

      Too tired tonight to try to word out the geometry/physics of why I think this is correct.

      It has been cited by "Locost" (Lotus 7 replica) builders through moon buggy (offroad performance) vehicles, as well as in discussion of more relevant cars, when speaking of changes, modifications, handling quirks, and comparisons to Watt's and Mumford options... so for my uses, I think that is pretty conclusive.

    3. #3
      Join Date
      Sep 2007
      Posts
      424
      Yeah I think that's the deal (center line of axle) but I'm not positive.

      The most important design concerns with Panhard bars is to make the bar as long as feasible, and get the bar sitting flat horizontal when the car is at ride height. But you probably already knew that stuff.



      The horizontal-at-ride-height issue is gonna be the most important thing in order to make the end result feel right. A long bar is a benefit, but don't compromise the horizontal ride height angle for the sake of that.

      And, of course, build everything strongly enough. And make sure there is adequate bushing flex so that the rear suspension doesn't bind when it tries to move. If there aren't any rubber bushings in the Panhard bar assembly itself then you probably need to have rubber somewhere else in the suspension.




    Advertise on Pro-Touring.com