Do I have a bad anti-wrap bar design, with pics?

[cybrfire]

So, with a single link design, what prevents the axle housing from twisting? You're saying the front of the leaf springs are basically the lower links, however, they are not rigid enough... They bend and flex which is where we began. Springs bending to an S-shape. With enough torque and traction would your axle not rotate around the single link connection point at the axle housing and forcing the springs to an S-shape....

 

[Hogback Fabrication]

So, with a single link design, what prevents the axle housing from twisting? You're saying the front of the leaf springs are basically the lower links, however, they are not rigid enough... They bend and flex which is where we began. Springs bending to an S-shape. With enough torque and traction would your axle not rotate around the single link connection point at the axle housing and forcing the springs to an S-shape....

Talking about axle wrap, don't think of the springs as links at all. Just think about how this one link will prevent the axle from wrapping (the leaves obviously keep everything from moving side to side or front to back).

What they are talking about is one link with either a bushing or SRE on each end. No shackle, just brackets and one link. This would certainly keep the axle from wrapping, if it wanted to twist up or down the length of the link would have to change (it can't) or the rear of the truck will rise up (called antisquat).

The real issue with this style antiwrap setup is that (at least to me) it would seem almost impossible to get it setup just right so that it doesn't bind through the leaves suspension travel.

The counterpoint is that its obviously been done, so its probably not as hard as I think (or maybe somebody just figured out how to do it on EB's)

 

[cybrfire]

Talking about axle wrap, don't think of the springs as links at all. Just think about how this one link will prevent the axle from wrapping (the leaves obviously keep everything from moving side to side or front to back).

What they are talking about is one link with either a bushing or SRE on each end. No shackle, just brackets and one link. This would certainly keep the axle from wrapping, if it wanted to twist up or down the length of the link would have to change (it can't) or the rear of the truck will rise up (called antisquat.)
The real issue with this style antiwrap setup is that (at least to me) it would seem almost impossible to get it setup just right so that it doesn't bind through the leaves suspension travel.

The counterpoint is that its obviously been done, so its probably not as hard as I think (or maybe somebody just figured out how to do it on EB's)

Yep, I agree, the leaves prevent side to side or front to back. They however aren't necessarily rigid enough to prevent the axle from going ahead and wrapping using the single link joint at the axle as a rotation point.

I can see where this system will work for some and not for others. It would depend on other factors though.

 

[ntsqd]

But you'd have to have a anti-wrap for bar for each spring length option; 52, 56, 56 backwards, 57, 57 backwards, and 63s are the ones I can think of.

I am very interested in trying to see if I could set this up in my truck. Thanks for all of the info.

That part I hadn't counted on, yeah one for each different spring set-up.

They used, for reasons I don't understand, a Ford Radius Arm bushing at the front end of the Wrap-Trap. Possibly to allow some marginal fore-aft compliance, but I do not know.

Welcome.

So, with a single link design, what prevents the axle housing from twisting? You're saying the front of the leaf springs are basically the lower links, however, they are not rigid enough... They bend and flex which is where we began. Springs bending to an S-shape. With enough torque and traction would your axle not rotate around the single link connection point at the axle housing and forcing the springs to an S-shape....

It takes torque, not linear force, to twist the springs into an 'S' shape. If you have really deeply arched springs then this may not work, but I'm talking monster truck type springs & those guys wouldn't be interested in this since you can't easily see it.
Otherwise under throttle the single link is in tension and the fwd part of each main leaf is in compression. Ideally the leaves would be in tension and the link in compression, but to do that kills ground clearance and wheel travel.

 

[cybrfire]

It takes torque--- Agreed.


Otherwise under throttle the single link is in tension---- Agreed.

and the fwd part of each main leaf is in compression.---- Here's where ya lose me. Since the axle rotates around the center of the housing, or axle shaft center line, Looking at the rotation from the drivers side wheel, under throttle the housing wants to rotate counter clock wise, pinion upward. Your leaf springs on top of the axle aren't in compression.

 

[Greg72]

Kurt,

I think you mean "clockwise" not "counterclockwise"....

If you agree that the pinion is trying to rotate UP under power, and you agree that the new, top mounted single-link bar is rigid enough not to stretch under the loads. The the front part of the spring would have to compress across it's length to allow for any movement of the pinion.

That is what is meant by the term "compression" in this case.

 

[miniwally]

The only way I have seen a set of traction bars work with only one axle mount was to mount the bars on the bottom of the axle tube so when the axle wrap started the leaves went into tension. With the leaves in tension they can't buckle like they can in Compression.

The down side to this is some bad antisquat to on acceration the vehicle tends to raise up some. In a wheeling environment it didn't seem to be that noticable.

 

[muddermilitia]

This seems like a good thread to add to the COG forum

 

[79k20350]

Heres a picture of wally with single anti wrap bars in place... If i was doing a suspension setup with leaves, this is bar far the way I would go...

An 830 on a 30* ramp with a questionable shackle angle... that suspension can move...!

 

[camok5]

I'm with Kurt on this one because I have tested my anti wrap bar with just one point hooked up. Even though mine can slide in and out at the frame, when I would power brake the blazer my axle would still wrap up and the slide mount wouldnt even move. I could easly see the axle rotating around the single point (on the axle) and also watch the leaves bending in a S shape to allow it to happen. I get the idea and how it would work but I dont think the leaves work well enough like the other 2 links. With the single link on top of the axle it still can rotate upwards around that spot and it doesnt need it to stretch to do so.

 

[ntsqd]

snip......

and the fwd part of each main leaf is in compression.---- Here's where ya lose me. Since the axle rotates around the center of the housing, or axle shaft center line, Looking at the rotation from the drivers side wheel, under throttle the housing wants to rotate counter clock wise, pinion upward. Your leaf springs on top of the axle aren't in compression.

The upper is under tension so that old thing about equal & opposite forces comes into play. Something has to resist motion in the other direction. Whether they're above or below the hsg CL the upper's higher position forces the leaves into compression. A case of the 'linkage' geometry under load forcing a change in the true axis of rotation.
It's not easy to see, but it's easier to see with a Free Body Diagram than it is with hard parts.

If the frame end isn't fixed (no shackle or other additional parts) and/or the link's length btwn the pivots isn't fixed then I would not expect any test results to indicate anything of value. The reason being that not much displacement would be needed to completely relieve the tensile stress in the link. The displacement could easily be a small enough distance that you would not see it with the naked eye. Once that tensile loading is lost the link will do nothing for you.
If the upper link's geometry isn't as described far above then I do not know what you could expect to happen. Could completely negate having anything there at all. Could function as intended.

I'm willing to keep explaining this type of link, but I kind of get the feeling that people are convinced of the A-bar's superiority. I firmly disagree, but if that's what you want to run then go for it. Prior to Lars', TZ's, & my discussion on the topic I would have agreed with it being so. No longer is that the case.

 

[camok5]

For me, its not that I believe that the A-bar is any better but it has been proven to work and gets the job done well enough. Your idea sounds good in theory but without proof or at least a good diagram, its a little hard to follow exactly what you are trying to explain. I think I get most of what you are saying but in my reality I need to see how it works. Also I think you have done a good job of explaining your idea but as you can see alot of other peolpe are still confussed on exactly how it works.

 

[cybrfire]

So, if you attach the upper link further from hsg CL than the main leaf of your spring pack the upper leaf goes into a compression state.

Is that what you're saying?

AT this point I'd have to put one together and try it but still seems to me that now you'd be rotating the entire axle around the center point of the upper link mount eye at the axle end which may still cause spring wrap.

This is a good thread!

I did mean clockwise. Thanks for the correction. I reread my post 3 times to make sure i was saying what I meant and still didn't catch that!

 

[ntsqd]

For me, its not that I believe that the A-bar is any better but it has been proven to work and gets the job done well enough. Your idea sounds good in theory but without proof or at least a good diagram, its a little hard to follow exactly what you are trying to explain. I think I get most of what you are saying but in my reality I need to see how it works. Also I think you have done a good job of explaining your idea but as you can see alot of other peolpe are still confussed on exactly how it works.

Perhaps this will help will seeing how the forces work:

This is accel as the axle hsg is trying to rotate the pinion up ("climb the ring gear"). Compression braking would reverse the arrow directions on each part. Gotta leave work now. I'll finish this up later tonight.

 

[cybrfire]

Camok5 has the single link more or less on his axle now. Since his lower link is disconnected or broken, Here's is how I see the single link working.

The leafs are simply not rigid enough to work effectively as the lower link IMHO>

These pictures are not to scale. They are just roughed out to illustrate.

Hey, camok5, cut the rest of that weld off that is patching your lower bar together and go do some field testing for us. You basically have the single link design right now!

 

[blasphemous]

Camok5 has the single link more or less on his axle now. Since his lower link is disconnected or broken, Here's is how I see the single link working.

The leafs are simply not rigid enough to work effectively as the lower link IMHO>

That's what I've been thinking. A single link on top would be good for low horse or minor spring wrap when there was NOTHING stopping it. However, big block powered monsters would still wrap up the springs. I think the lower link setup, like pictured above, is the way to go to ultimately stop wrap up.

 

[cybrfire]

Actually, camok5's triangular link set up may have already done the testing for us. It's broken. Why?

There could be several contributing factors.

Not enough end seperation for effective triangulation??
Nothing to absorb shock loads??
To much articulation or twist??

 

[Greg72]

Camok5 has the single link more or less on his axle now. Since his lower link is disconnected or broken, Here's is how I see the single link working.

The leafs are simply not rigid enough to work effectively as the lower link IMHO>

These pictures are not to scale. They are just roughed out to illustrate.

Hey, camok5, cut the rest of that weld off that is patching your lower bar together and go do some field testing for us. You basically have the single link design right now!

Kert,

I understand conceptually what you're getting at, but there are a couple of things to consider....

1. The springs in your drawing would be a lot thicker and more substantial than what you've shown.....ie. stiffer. And the forces aren't pushing the spring UP...they are moving laterally, trying to compress the distance between the spring eye and the springpad.

2. CamoK5's wrap bar, even with a broken lower link is not a good design for validating a single-link antiwrap bar. Look again at how close the upper link pivot is to the top of the pumpkin housing...it only looks like it's maybe 2" higher than the pumpkin itself....and too close to the axis of rotation to be effective. You were right in speculating that it does not have enough "link separation" from the axle leafspring mounts to create good triangulation.

I think the real answer is that in real life, with more link separation and normal leafsprings....there will be substantially more stiffness than you are illustrating. Ntsqd will have to provide the "heavy math" that proves WHY if he's so inclined.

 

[cybrfire]

Kert,

I understand conceptually what you're getting at, but there are a couple of things to consider....

1. The springs in your drawing would be a lot thicker and more substantial than what you've shown.....ie. stiffer. And the forces aren't pushing the spring UP...they are moving laterally, trying to compress the distance between the spring eye and the springpad.

2. CamoK5's wrap bar, even with a broken lower link is not a good design for validating a single-link antiwrap bar. Look again at how close the upper link pivot is to the top of the pumpkin housing...it only looks like it's maybe 2" higher than the pumpkin itself....and too close to the axis of rotation to be effective. You were right in speculating that it does not have enough "link separation" from the axle leafspring mounts to create good triangulation.

I think the real answer is that in real life, with more link separation and normal leafsprings....there will be substantially more stiffness than you are illustrating. Ntsqd will have to provide the "heavy math" that proves WHY if he's so inclined.

You may be right, I can see where a single link system may help to prevent spring wrap. Just not convinced as of yet that it will eliminate it the way a triangulated bar should if employed properly.

ntsqd, bring on the math!!! Wonder if the Excelcad 4link calculator can work some numbers on this.

 

[ntsqd]

If I get to it today I'll start, otherwise it'll have to wait until next week.