Anti-Wrap Q's (1 Viewer)

[Mace]

The bar shown above with the shackle will lift the rear end if the weight is removed from the rear end. Jack it up from the frame and you will see. It can still articulate fine but will bind when weighting and unweighting.

Are you talking unloading due to going uphill or downhil or?? If you are talking about the habit of many A frame bars lifting the rear body on acceleration I'm still confused.

It is my opinion that the shackle should point straight back at the axle at ride height and the tip of trac bar should be able to telescope. On acceleration, the bar will tip upwards and lengthen so the tip travels around the arc dictated by the shackle. The axle will wrap some, but it will be controlled by the length of the shackle. The resulting wrap will be within the limits of the u-joint as long as the shackle isn't too long.

I would like to see this in action. It sure appears that you would floor it, and the extension would slide out till the shackle basically goes vertical. Then it would max out and suddenly you would have huge antisquat numbers making the rear of the vehicle jack on acceleration badly (and hop with hill climbs).

When you unweight the rear end, the tip of the trac bar will want to drop straight down. Decker's diagrams are correct in this regard. The bar has to be able to telescope so that it can follow the arc dictated by the shackle in the downward direction.

With stock spring geometry, the actual movement of the pinion flange is negligible. It tends to point straight ahead or rotate slightly towards the Tcase. If you flip the springs, then things change, but 99% of the movement is straight up and down (with some forward and backwards).

Since the tip of the bar floats inside the main bar it can be a bushing. The whole tip rotates within the body of the bar.

The more I argue about this, the more I'm sure I'm right. I should get a patent.

I'd take your truck to a block wall and video what happens in 2WD with the front tires blocked..

 

[Fast Eddy]

I'd take your truck to a block wall and video what happens in 2WD with the front tires blocked..

Good idea. I have a little camera I could mount under there. Not a lot of spare time lately though.

 

[Fast Eddy]

Ed,
Post a pic of your set up.

Keith,
Click on the After link in his sig. It starts on page two towards the bottom.

Posts 35 and 36, but those pictures aren't enough to show what I'm talking about.

What I curently have is more like a prototype to work on the design. The main bar isn't as strong as it could be. It's changed a bit since those pics. The shackle is about straight back at ride height now. Even though we discussed the length of my main bar out beyond the weld, and I agree that it could be stronger, it has survived a half-dozen trips including Rubicon as it is. I'll rebuild it with some DOM and the weld closer to the end in any case.

It really sucks that I don't have time to properly document my theory with a video. I'll try to do something around xmas when I'm not so busy. I'm newly self-employed with three clients and trying to get two more.

This picture kinda shows it. Kinda. The spring prevents the shackle from going over vertical at the top. I'm pretty sure it's not necessary, more like insurance. I got a new muffler since this pic too.

 

[74fj40ca]

I think it's time to pull out the GoPro and do some testing. I'm going to change my design on Friday, I'm going to run a heim joint at the frame, along with the 2 on the axle.

 

[chicago]

I think it's time to pull out the GoPro and do some testing. I'm going to change my design on Friday, I'm going to run a heim joint at the frame, along with the 2 on the axle.

Despite all the debate on the "better" design, the standard triangular design you're planning will likely be more than sufficient.

 

[74fj40ca]

That's kind of what I was thinking. I'm a little curious as to why you would want to use a shackle and a telescoping anti-wrap bar, doesn't the shackle basically do that exact thing, as using a telescoping style?

I'm starting to think my 5/8" heim's might not be "big enough" for the anti-wrap bar.

 

[Fast Eddy]

Despite all the debate on the "better" design, the standard triangular design you're planning will likely be more than sufficient.

No disagreement there. It's fairly well-proven if built strong enough.

 

[chicago]

That's kind of what I was thinking. I'm a little curious as to why you would want to use a shackle and a telescoping anti-wrap bar, doesn't the shackle basically do that exact thing, as using a telescoping style?

I'm starting to think my 5/8" heim's might not be "big enough" for the anti-wrap bar.

I think I used a 5/8 in heim and used 1/4 wall DOM for the ladder frame. I'd make every effort to have the upper and lower tubes meet as close to the end of the wrap bar as possible. I added 1/4 In plate as sort of a gusset INSIDE of the triangle. There really is a LOT of force generated in "wrap". The one failure I had seen resulted in a busted pinion IMMEDIATELY after the wrap bar snapped. It was a design where there was 2-3 in. of overhang on the main tube.

 

[74fj40ca]

I think I used a 5/8 in heim and used 1/4 wall DOM for the ladder frame. I'd make every effort to have the upper and lower tubes meet as close to the end of the wrap bar as possible. I added 1/4 In plate as sort of a gusset INSIDE of the triangle. There really is a LOT of force generated in "wrap". The one failure I had seen resulted in a busted pinion IMMEDIATELY after the wrap bar snapped. It was a design where there was 2-3 in. of overhang on the main tube.

I'm using 1/4" DOM for both bars now. If I remember correctly, the bottom bar meets the top bar with about 2-3" to the joint. I don't have a gusset though, even though I thought about putting one on. Since I'm going to be changing it, I might as well put one there, definitely would not hurt.

 

[Fast Eddy]

Mine's made out of sch 40 water pipe and it's been through Rubicon with about 5" of extention beyond the welded joint. This is possible because the inners are fzj80 lower links. Not sure of the thickness of that tubing, but it is a pretty small OD.

If you think you need .250-wall tubing, you might ask yourself why. That's strong enough to lift the entire weight of the rig with a 2' lever arm. You have two leaf springs sharing the torque with the anti-wrap bar. It should not need to be this strong. I suppose this depends on what motor and gears you're running. Anyone in this thread running a big block, 200:1 and 42s? If so, I will STFU.

Great article on tubing strength over at PBB: http://www.pirate4x4.com/tech/billavista/Links/

 

[74fj40ca]

Mine's made out of sch 40 water pipe and it's been through Rubicon with about 5" of extention beyond the welded joint. This is possible because the inners are fzj80 lower links. Not sure of the thickness of that tubing, but it is a pretty small OD.

If you think you need .250-wall tubing, you might ask yourself why. That's strong enough to lift the entire weight of the rig with a 2' lever arm. You have two leaf springs sharing the torque with the anti-wrap bar. It should not need to be this strong. I suppose this depends on what motor and gears you're running. Anyone in this thread running a big block, 200:1 and 42s? If so, I will STFU.

Great article on tubing strength over at PBB: http://www.pirate4x4.com/tech/billavista/Links/

I'll read through the link after while, I enjoy all of Billavista's Articles.

After looking at my tubing again, I made an error, I'ts not 1/4" DOM. It's actually 1 1/4" .120 wall DOM.

I think mine is fairly decent, but I do believe I will be changing to all heim's, and maybe adding some gussets to it.

I'm running a F135 w/ 3sp, and original tcase, on 33's!

 

[Fast Eddy]

Your weak link is for sure the x-member. Sleeve it and you'll be good to go, at least until everyone's upgrading to the "Fast Eddy bar".

 

[BionicCruiser]

if you use 5/8 heims, get the larger aircraft quality ones. those should be strong enough with your set up. IIRC that's what I have now with the LT1. the regular 5/8 ones broke with the I-6 and took out my pinion. (many years ago when I was much more inexperienced at wheeling and fabbing)

 

[74fj40ca]

I actually just picked up some new 3/4" heim's, to replace the 5/8" heim's. Up next will be to sleeve the crossmember.

 

[chicago]

Nope... Sorry, I mis spoke earlier and said I used. 5/8's heims.... I used 3/4 heims.

 

[74fj40ca]

3/4" heim installed, have to wait until I get a jam nut, my local place didn't have any LH thread jam nuts.

 

[Chris Wilcox]

I have a 80 series (narrowed) locked axle under my 40. The axle came with all the 80 control arms so I used them and the brackets stripped off the axle to build a wrap bar. I'm not sure you guys will like it but this is what I built and I like it.
Chris

 

[74fj40ca]

I have a 80 series (narrowed) locked axle under my 40. The axle came with all the 80 control arms so I used them and the brackets stripped off the axle to build a wrap bar. I'm not sure you guys will like it but this is what I built and I like it.
Chris

Got more info on that disk brake parking brake?

 

[Chris Wilcox]

Yes, in this other thread.

https://forum.ih8mud.com/60-series-wagons/692467-transfer-case-e-brake-3.html

 

[74fj40ca]

So long time after my last post. I got my anti-wrap bar modified, after I snapped the welds off the bracket the first time.

So after I installed a 3/4" heim joint at the front, and took it on some back roads to do a little hunting, this happened.







How it happened, I have no idea, still can't figure it out. My goal was to put my GoPro under the tub, so I can see how it was flexing, but I left at night, and didn't put the GoPro on.

The front shackle moves, does not bind or anything like that, I'm thinking the weak point was the anti-wrap bracket itself, might be time to upgrade to the RuffStuff anti-wrap bar.