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Originally posted by tgreening 02-18-2012 11:58 PM
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Originally Posted by Resbum
The bars are shackled at the front.
budojeepr kind of hit on it, though. I think the problem has to do with where the front of the track bars/shackles are mounted. When the spring flexes this changes the length between the axle and front spring mount, the radius getting longer and shorter as it travels up and down. This in turn changes the location where the front of the track bars actually wants to pivot around.
This has to do with my earlier post about math I'd struggle with. There is a way to calculate the most desireable location for mounting the track bar to frame shackle pivot point. i.e. track bar length. This would put the the pivot point of the track bar at the "imaginary" pivot point somewhere out in front of the spring mounts.
Based on what I saw when I assembled everything I would have been very close to that "imaginary" pivot point if I'd mounted the track bar shackles to the front of the crossmember, instead of the rear. With the track bars hooked up to the axle, between full droop and the springs compressed to mid point of travel the front pivot point of the track bar changes location by about 1/2". If we take that one step further we could think that between full extension and full compression my track bar pivot point wants to change by about an inch.
I can see where that could hinder my articulation some. Resbum________________________________
tgreening says
I "think" I get what you're saying, but I don't think that's going to be the problem. The travel radius of your trac bar is dynamic because the shackle can move for/aft to eliminate any bind. That takes care of suspension compression. When you're or the gas with good traction is when the trac bar is actually trying to rotate. I have mine set so it is trying to pull the shackle up, yours would be trying to push the shackle up. I'm not sure if that would be an issue or not.
It's been a lot of years since I've worked on this problem, but I think where the issue arrises with the dual bar setup is whenone tire is at full stuff and the other at full droop. In this scenario one side of the axle is moving to the rear and the other side to the front. What this does in effect is make your axle a bit twisted out of alignment under your frame. In extreme articulation cases this is what causes axle steer.
What this does to your trac bars is in essence swing them to one side or the other, depending on which side is drooping and which side is compressing.
Now your forward ends of your trac bar are not just pushing up against the shackle and twisting withIN the shackle, but they are trying to push the shackle sideways, and this is where I believe the bind comes from. A single trac bar would have the same problem, just to a lessor extent.
On my jeep I have a single trac bar mounted right beside the pumpkin, and my shackle not only swings for/aft like yours will, but it will also rotate side to side. I have no binding issues and the suspension will actually flex beyond good sense. I'll see if I've got a pic somewhere.
In your case all of this is probably a moot point since your intended wheeling is fairly light. You will on the other hand have excellent wrap control on the road when moving around any heavy loads, or just testing the oomphfability of that big oil burner in there.
tgreening