Better anti wrap ideas? (5 Viewers)

[ntsqd]

I am actually curious to know if anyone has run the single bar type link to the bottom of the axle housing.

That might actually do the trick.. As long as handling characteristics are not hampered too much by it..

Some of the Shelby Mustangs had a similar system, two under-rider bars. They are the only thing close that I know of.
I've seen pics of mudders with dual bars, but I've yet to see such a system that looked like it was well thought-though, most, like those Rauncho kits, appear to be aimed at looks.

A potential downside to a single under-bar would possibly be partial suspension lock-out. It is possible, though I've no idea if likely, that the tension induced in the front 1/2 of the main leaf while under load would mean that it could no longer flex.

 

[Mace]

Some of the Shelby Mustangs had a similar system, two under-rider bars. They are the only thing close that I know of.
I've seen pics of mudders with dual bars, but I've yet to see such a system that looked like it was well thought-though, most, like those Rauncho kits, appear to be aimed at looks.

A potential downside to a single under-bar would possibly be partial suspension lock-out. It is possible, though I've no idea if likely, that the tension induced in the front /12 of the main leaf while under load would mean that it could no longer flex.

Exactly..
But even so, if it stops a person from having to replace a pinion out on the trail.. It is a good thing.

 

[Randy88FJ62]

The traction bar attachment points should use heim joints in order to allow for some minimal rotation. I assume this would help alleviate any reduction in articulation. When I make one I plan on using heim joints.

 

[ntsqd]

That would depend on the nature of the limitation. If it is a pivot point that can't also rotate off-axis (as can an SRE (Spherical Rod End, "Heim" is one of many mfgs), then yes. If it is due to the linkage binding the rest of the suspension then no.

 

[D'Animal]

I have the brackets, tubing, sleeves, joints and everything ready to build the Anit-Wrap. I have read this thread several times and understand the tension and compression of the anti-wrap bar. I was laying under my rig getting started on this and I think I messed up when I did my SOA.

Should the rear axle pinion point directly at the transfercase? I setup my front that way. I installed my rear axle with the flange parallel to within 1 degree of the output on the Transfer Case. I did not have any weight on it when the perches were welded. It looks way off now. I'm using the 63" chevy 1/2ton springs and they are super soft.

I added 500lbs to the bed area (I put 4 Warn 8274's with cable on it, so I'm guessing) and the pinion angle looks "OK". I added 6 degree shims and added the weight back on and it looks a little better but I did not get 6degree of movement on the pinion flange. The pinion is still parallel to the t-case output. It seems the springs are absorbing the angle change.

What am I doing wrong?

When I build the Anti-Wrap. I want the additional finished weight on the rig right?

 

[ntsqd]

Conventional wisdom for a leaf sprung drive axle is 1*-3* down from matching angles with the transfer case output. The theory being that the springs will wrap under acceleration and then everything will be where they should be. This would be without any sort of traction device.

With a rigid traction device like an A-frame you'll want the pinion pointed at the transfer case and the drive shaft to have a CV joint at the transfer case. The A-frame design ideally wants the forward pivot to be at the center of the CV joint in the side view. This will minimize the drive shaft plunge. The further away that the forward pivot is from the center of the CV joint, the more drive shaft plunge there will be. Some isn't a bad thing, but plunge under load can lock up wheel travel. That is to say that the bind in the slip while under load can severely reduce the ability for the suspension to move freely. Plunge is a big concern in desert racing, I suspect that crawlers can get away with quite a bit more.

Since the pinion angle will be fixed by the A-frame rather than the springs, loaded or unloaded won't make any difference so long as getting it correct is within the adjustment range of the linkage.

The spring shim thing has me puzzled too. I'll think on it, see I come up with any ideas.

 

[D'Animal]

The spring shim thing has me puzzled too. I'll think on it, see I come up with any ideas.

Thanks

This is on my FJ40.5 Extended cab rig. My rear driveshaft is 57" long. I'm using 63" Chevy springs and I moved the rear axle back 14".

 

[Mace]

Grind the welds off and just rotate the pinion. Make sure that everything is lined up before the traction bar is created.

btw, if you have it in gear, wheels chocked, pbrake on, the axle won't want to move at all. It will want to stay static..

 

[ntsqd]

The only thing that I'm coming up with, and I'm afraid even mentioning it might be an insult, but are the angle shims facing the same direction? I've overlooked sillier things myself. Almost specialize in it.....

 

[D'Animal]

LOL!

The think part is towards the back of the rig, on both side.

The only thing that I'm coming up with, and I'm afraid even mentioning it might be an insult, but are the angle shims facing the same direction? I've overlooked sillier things myself. Almost specialize in it.....

 

[D'Animal]

BUmp for others to read and see.

 

[Benjitis1]

Good thread. Ressurected.

 

[Randy88FJ62]

Per ntsqd’s post #99:
“Consider just an axle mounted on leaf springs. No other linkages of any sort.
Now compress that suspension. Does the pinion angle change? How much?
Extend that suspension. Does the pinion angle change? How much?
Once you understand where and by how much the pinion angle changes through the range of suspension travel, Then you can evaluate what linkages will work and last and what won't. Do not fall into the trap of allowing others to think it through for you. Think it through yourself. If you have to, mock it up using only the main leaf of a soft spring. The common assumption of how the pinion angle changes through the range of suspension travel of a leaf sprung suspension is wrong. It is wrong because it fails to account for the intentional bending of the leaf spring in it's normal function.”

I have extra spring packs and I am thinking about mocking up the rear with just the soft military wrap spring as mentioned above by ntsqd in post #99. I would not only do this for the anti-wrap bar but also to check for proper shock length instead of guessing. Measuring compression and droop from the shock mounts sounds easy and already has the predetermined points. This should yield the proper measurements for the shocks. What I have trouble comprehending is what constraints or measuring points I will use when checking axle position for the traction bar. Also, am I asking for trouble driving my FJ62 up a ramp to check compression when there is only one leaf? Could this cause axle wrap and wreck the pinion which is ironically what we are trying to prevent?

Goal: Find a way to measure axle movement and pinion angle properly to design a traction bar or bars without wrecking the diff.

 

[ntsqd]

Could remove the rear drive shaft.

 

[Randy88FJ62]

Could remove the rear drive shaft.

That simple I guess I'm overthinking.

 

[PhilC64]

I've read thru this thread a couple of times since snapping my pinion in early December and am considering a couple of designs. One that has caught my eye is in the pic below. It's mounted on a 4 Runner but can be adapted to my FJ40.

Can I get an opinion of this design, both good and bad.

 

[chicago]

I've read thru this thread a couple of times since snapping my pinion in early December and am considering a couple of designs. One that has caught my eye is in the pic below. It's mounted on a 4 Runner but can be adapted to my FJ40.

Can I get an opinion of this design, both good and bad.

Good way to keep it centered as much as possible!
Odd...never thought of that as a way to run that.
Wouldnt it have less strength as it rotated. The load wouldnt be distributed vertically between the 2 bars, but off set?

 

[ntsqd]

I know of one Mini that had (note past tense) a a-arm mounted to that 'horseshoe' cross member. It was NOT a good idea, broke the cross-member out of the frame. I forecast the same for that truck.

Otherwise all of the discussion above, specifically including my negative comments about the design, are talking about just that sort of traction link.

Since those posts I have encountered the sale and use of the single tube to the top of the diff housing. Using one puts the main leaves in compression, but does limit axle wrap without forcing the springs into a 'S' curve as does the a-arm design.
It is sold by Wildhorses and is specifically for Early Broncos. I say specifically because the pivot locations and the length needs to be worked out for the spring being used. Due to the spring's change in length the pivot points are not obvious. Having not done that work I don't know what to look for, but I can guess that the axle's true travel path needs to be plotted from points measured through out the travel range. Once you have that curve then the two pivot points will want to be a parallelogram to the axle and the front spring eye.

 

[twoturtlesracing]

Bump for a good read!

Sent from my iPhone/ IH8MUD app

 

[Wyoming]

Been reading everything here. I agree with the gentleman earlier, think it through. Some of the pictures above do not show the springs. Are you sure they are on leaf spring vehicles? Those A-frames that I'm seeing will stop the axle from wraping, but they will also cause the axle to pivot around the upper attachment point and that is not the natural movement of a leaf sprun axle housing. When a leaf spring compresses, the axle housing moves almost straight up and down with a little movement to the rear due to the shackle. The pinion angel may change slightly, but not enough to be of concern as far as your drive shafts are concerned. This changes slightly for a SOA. With the SOA the axle wrap then becomes a concern and fixing it with an A-frame as pictured above trades one problem for another - now your axle housing will bind with the A-frame in its natural movement. If you want to use the A-frame, you might think about a slip in it. This would allow the axle housing to move through its natural path while compressing and decompressing.

The best fix for all this is to go back to a SUA and then fabricate longer spring perches and attach them to your frame. This will allow you to return to the originally engineered intent of your leaf springs and thus give you a better driving vehicle (See pictures). You can build the spring perch towers to match the shackles you are using, whether they are stock or the longest you can find. This will allow you to get as close to the original geometry for the springs with respect to the driving surface as possible. I've seen some of the fabrication you guys are doing and this well within your abilities and it fixes most of your problems.

Always remember, whenever you weld on your axle housing, check to see if it is still straight when you are done. I know that it is hard to believe you can bend that axle housing, but you can when welding it. Just a slight bend can cause undue bearing and/or seal wear.

As to rotating your differential to point at your transfer case. This only needs to be done if you are putting undue angle on your universal joints and therefore causing premature wear and failure when the pinion and the transfer case output are in parrallel. When a universal joint that is is at an angle moves through a revolution, it will have to speed up an slow down to compensate for the different distances of travel from one side of the ange to the other. This will cause a vibration - Unless, you have another universal joint at the other end of the drive shaft working in counter-balance to the first. Remember, you have to have the transfer case output and the pinion angle the same for the counter-balancing to work. Once you have exceded the functional angle of the universal joints, you will then have to rotate your pinion angle to point at your transfer case and install a double cardon in your drive shaft. The double cardon is two universal joints directly adjacent to one another with a third universal joint at the other end of the drive shaft. The single universal joint is at the bottom end of the drive shaft next to the pinion and the cardon, or double universal joint, is at the upper end next to the transfer case. The two upper universal joints then each take up half the angle in the drive shaft and counter-balance each other. The geometry of this will not change enough to worry about during normal spring compression as you have three universal joints and the movement is brief in duration no mater how many times you are doing it. The geometry of this will change during axle wrap. How much and how significant will depend on how much wrap you get. The wrap will have to change the pinion angle to exced the functionality of the universal joints.