How doe a traction bar work? - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 01-07-2002, 02:18 AM
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How doe a traction bar work?

Ok.with a SOA 76 cj5, i need a traction bar.I've read all about (scoured this site and others) them and decided on the Sams, Parts Mike, or making my own patterned after the sams design.I aint completely stupid cuz i did my jeep ground up with the soa and did it all correctly.BUT- after a lot of thinking i still don't understand how the sams or similiar designs can work. I must be having some long term mental block. What i don't get is-how the shackle in the front allows the axle to move up and down??? i must be blind or nuts-i just dont see how the front end of the bar can go up or down without substantial longitudinal motion(to allow the shackle to radius around it's fixed end)and obviously thats restricted by one end of the spring being fixed.Another way to put it is-as we go over bumps, how can the axle go up or down if it is fixed at the front end???Yes-it can go up and down BUT only in combination with substantial longitudinal movement, which is further distance than is allowed by the spring unloaded length and the spring mounting shackle movement.Did I make sense?The goofy thing is, i think i understood it a few months ago but now it totally escapes me.DUUUH... Pleez xplain someone!

k
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post #2 of (permalink) Old 01-07-2002, 07:59 AM
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Re: How doe a traction bar work?

a track bar definitely limits the articulation. most serious wheelers take the front and rear off. i still have my front on. i should either take it off or install an adjustable.




post #3 of (permalink) Old 01-07-2002, 10:09 AM
 
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Re: How doe a traction bar work?

I think he meant traction bar,as in spring wrap not trac bar that laterally locates the axle.

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post #4 of (permalink) Old 01-07-2002, 10:22 AM
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Re: How doe a traction bar work?

roger that


post #5 of (permalink) Old 01-07-2002, 10:33 AM
 
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Re: How doe a traction bar work?

I never understood axle-wrap , and spring wrap, anybody care to delve?
Thanks!


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post #6 of (permalink) Old 01-07-2002, 11:25 AM
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Re: How doe a traction bar work?

This does pretty good at explaining it.
http://www.outdoorwire.com/4x4/jeep/tech/susp/axlewrap/

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post #7 of (permalink) Old 01-07-2002, 12:24 PM
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Re: How doe a traction bar work?

When we used to build hot rods with leaf springs, spring "wrap-up" was a common problem. What happens is that, as power is applied to the pinion gear, it is supposed to rotate the ring gear and turn the axels. When the tires resist that, the pinion will "walk up" the ring gear instead. In doing that the whole axel assembly will rotate, maybe as much as 15 degrees. In the process it bends the leaf spring into an "S" shape. When the tires break loose the springs snap the axel back into it's designed alignment. Then the tires grab hold and the whole process starts over. The result we used to call "axel hop."

We built two types of bars to remedy this condition. One was a link bar. There is an eye on a bracket welded or bolted beneath the spring plate, and another eye below the front spring eye. Then a rigid bar is linked between these two eyes. That effectively forms a parallelogram. The axel tube can now move up and down, but it can not rotate without stretching, compressing or bending something.

The other kind of bar we built was a rigid beam that bolts to the bottom of the spring plate. It extends forward to a point an inch or two below the front spring eye. When the axel tube starts to rotate, the front of the beam swings up. When a bumper on the top of the beam hits the spring eye, or a plate welded to the frame, it effectively stops the twisting.

Another way we discovered to reduce hop was to move one of the shock absorbers to the front of the axel tube, and now you see this on most pickups. What that does is make one shock compress and the other extend for the axel to rotate. It inhibits wind-up, but won't stop it completely.

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post #8 of (permalink) Old 01-07-2002, 01:29 PM
 
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Re: How doe a traction bar work?

http://www.outdoorwire.com/4x4/jeep/

Took a while to find it.

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post #9 of (permalink) Old 01-07-2002, 01:33 PM
 
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Re: How doe a traction bar work?

The wrap bar is not stationary at the front shackle connection. It is bolted trogh the shackle using a bushing. The front end is allowed to pivot at the bushing to allow up and down travel. The shackle mearly allows the track bar to move back and forth with as the axle travels its arch through the suspension cycle. The reason it still resists wrap while allowing the axle to so freely move throughout its cycle, is by eliminating the axles ability to rotate upward, as that is held in check by the front of the bar and the shackle. So the axle can move up and down, and back and forth, but it can not rotate.


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post #10 of (permalink) Old 01-07-2002, 06:02 PM
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Re: How doe a traction bar work?

Pbm-I know you can answer my question.I also thank others for their responses.Very good article on different traction bars.(i had read it and many others previously)I understand axle wrap and how the bar prevents it.There is just one piece of the puzzle i don't understand at all--If the front mounted end of the bar cannot move the same vertical distance as the rear axle is able to move(limited at the top of its motion by a bump stop and the bottom by spring extension, shock absorber extension limit or limiting chain or cable)how the heck can the axle move relatively unhindered by the bar within its capable range? Please re-read my initial post carefully and combined with this one i think you'll see my question. Thank you very much.BTW-i believe i spoke with you re:mil.wrap cj leafs a few weeks ago.If your friend got em from jc whitney, I believe they were Omix-Ada.The current leafs offered by Omix for cj are not mil wrap.I'm told their (Omix) product offering changes time to time more than one might expect.I did finally find a pair in St.cloud (you're in MN, right?) for $103 each.Marc in MN

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