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Old 06-02-2009, 02:15 PM   #83
Sidecar Jockey
Joined: Mar 2002
Location: Middleburg, Pa. (Snyder County)
Oddometer: 3,964
Originally Posted by RedMenace
So, going back to the original post, it appears absolutely necessary to have an accurate measurement of the lineal offset to use this formula. What I don't see is a practical way to arrive at this on a real bike, assembled, with fender,wheel and tire in place. How the hell do I do this?
Dog gone it there is more to it that just doing some math. The rigs we run are not rigid all around and supensions vary a lot. A ridgd sidecar suspension with a heavy bike like a harley may be able to do fine with less lead than a stock sprung Oil Head GS with a havy sidecar on it.
Simply put .. Suspensions move and cause things to happen. Light bikes unload the rear end with aheavy sidecar in turns away from the sidecar easier than heavy bikes.
I would love for one of the enginner types to be able to come up with an easy way to establish roll centers on each corner of a sidecar rig and from that be able to calcuslate the roll couple under various circumstances. To treat a sidecar rig as it it had no suspenaion may get one intop the basic ball park but to not be able to think things out related to how a suspension works on a given rig is a good way to put it 'out of the ballpark'.
A few years ago this deal bothered me and I spoke to some folks who were susposed to be in the know as far as suspensions go. I knew that if we could raise the roll center we coudl have decent results and create better cornering on a flatter plane. Lowering the center of gravity can only be done to a point on many rigs and off road or dual sport rigs are kinda stuck with what they have. The suspension guys basically did not really desire to get into it as far as something as weird as a sidecar goes I suppose.
So we built a k bike rig with a dual torrsion bar rear suspension on it. The torsion bars were set very high in hopes of by doing that the roll center woudl be raised. There were two bars so it coudl have a more progessive spring rate. Anyhow once the rig was done and run hard we knew we were onto something. I actually spun the thing out twice in turns toward the sidecar with no body on the sidecar frame. But, the thing was disassembled and sold before we coudl get into it more. Maybe some of the ones here like RichardNL or Phyllis would have the time to experiment with such stuff. trust me it does work but time and money are always an issue when you are walking so far out of the box.
Food for thought anyhow
Sorry for rambling and I HOPE my typing wasn't too bad

Founder: Internet Sidecar Owners Klub at SCT

President: C Stanley Motorsports Inc.
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