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Leafers show me your anti wrap solutions


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So I broke another 3.54:1 rear diff at the weekend. Wasn't doing anything silly, but I think the issue might be axle wrapping. The rear axle that is.

Looking at options I think an anti wrap or anti tramp bar is probably the preferred solution, as I like the way my Series is going in all other aspects.

 

I did a bit of searching and did find some topics on here, although the most recent was 2013. Just wondering how you guys are getting on with your chosen solution? Would you still do it the same given the choice or something else?

 

Any pics or designs would be grateful.

 

 

Thus far, my first thought was some kind of radius bar type thing attached to near the top of the diff. To stop the diff nose twisting down when trying to move forward.

 

I've found these images online, which seem somewhat to be a similar idea. Although they have a shackle to lengthen the bar as the axle drops. And are connected to the axle tube above and below, presumably to prevent the diff nose lifting as well as dropping. i.e. axle wrap when going forwards or reversing.

 

10433_P1020599_2.jpg

Dcp_2131.jpg

 

QUESTION:

I'm not so fussed about axle wrap when reversing. It's more when doing hill climbs, to stop the nose of the diff dropping. If I fitted something similar to the above, but only attached it to the top of the axle, it should in theory still work shouldn't it?

 

Browsing Google I also spied this:

wmtrackbar.jpg

 

Could you potentially use some coiler trailer arms for this purpose? My confusion comes from the fact the designs above extend using the shackle as the axle drops. How would a fixed radius arm cope with this?

On a coiler, does the axle move differently and not back and forth as much as it does with leaf springs?

Edited by Chicken Drumstick
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You need the shackle IMHO, otherwise all you are doing is changing the point at which the axle will rotate, and mullering your bushes at the same time.

The shackle allows the natural arc of the axle movement retained by the leaf spring to operate, yet eliminates twist in the axle tube at the same time. 

That third picture will actually cause the diff nose to rotate down as the axle droops -I doubt the bloke who built that understood the concept at all, and every spring compression is going to be forcibly rotating the axle tube horribly.

Well, IMHO :)

 

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I think I may have stumbled across it by accident last night. I don't mind using a shackle, I just want to stop breaking diffs really... :ph34r:

People are telling me to ditch the parabolics and run standard springs! But I'm not quite ready to throw the towel in just yet on the parabolics. I like they way they flex and ride on the road.

I've also read about larger spring perches can reduce axle wrap, but the anti tramp bar seems to be a more thorough solution to my mind.

Ages back I'm sure I saw a DIY kit for a Suzuki on a Suzuki site, long before I ever thought I'd need one. But I'll be buggered if I can find that site now.

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I'll chime in with my experience :)  contrary to common belief/internet engineering I have been running the most basic set up you could ever make for six years now with very little issues. The rear I literally have not touched in those six years, except for spraying a bit of Chain lube on the Spherical joints every now and then. And the only problems I've had with the front was mostly related to the packaging issues I had with an old steering setup I once had. I choose not to have any bushes at either end to avoid any bind whatsoever, and I have none, but it does mean every couple of years I get some fatigue-fractures around the mounts, but I don't mind throwing the welder at it as a trade off of not going through bushes at a heavy rate and getting the maximum performance from my anti-wrap setup. Did try a bushing in one end of the front bar once, but didn't like the feel so went back to solid joints. You can see how I did it from here on in my build thread:

And please bare in mind that my 80" only does offroad, and a lot of it every year, with lockers on both axles and always aired down to 0,5 bars (7 psi) So the torque stresses it sees are relatively severe. Basically I'm very satisfied and would not do it any other way, even after all this experience.

And it does have the added benefit, I found out in 2012, that if you do break a leafspring, you'll only notice because you get a lot of wheel travel suddenly :D as the anti-wrap basically acts like a link bar keeping everything under control. I doubt the shackled version would do that

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Soren's solution is what Bill VS was using.

The single bar solution is definitely the most elegant if you can thread it through the other bits. On the rear it's easy but on the front (as Soren's photos show) stuff can get in the way.

It kinda feels like it should bind up but I guess there's enough compliance in the system for it to work itself out, especially the one using coiler hockey sticks.

On my setup I went for forward-facing on the rear but rear-facing on the front to avoid the steering bars. I've never been entirely convinced by the front but also haven't bothered to do anything about it yet :P

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The single bar is the best solution IMO. The shackle solution with a radius arm is fighting the suspension, as the whole axle will rotate around the shackle end, while the leaf springs want to try to stop rotating the axle. They do opposite things basically.

The single bar, when laid out well will do the same thing as the leaf springs: letting the axle move up and down without rotating it.

By the way, if you think you are breaking diffs because of axle wrap, I reckon it is quite the other way round: The diff and shaft will not see any big shock loads, due to the axle being able to cushion it by wrapping the springs. So I don't think a wrapping bar is going to solve your problem. It's not a bad thing though.

 

Daan

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40 minutes ago, Daan said:

The single bar is the best solution IMO. The shackle solution with a radius arm is fighting the suspension, as the whole axle will rotate around the shackle end, while the leaf springs want to try to stop rotating the axle. They do opposite things basically.

You understanding of the geometry is incorrect.  The leaf springs control the axle movement around their non shackled end.  The ladder bar end is set to the same axial location.  This results in zero binding of the ladder bar and it does not interfere at all with axle movement.  It is all well tested and the geometry of the linkages studied.

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13 minutes ago, Red90 said:

You understanding of the geometry is incorrect.  

Incorrect. The ladder bar is rigid and rotates around the shackle bush, as the shackle end cannot move up or down, the only way the axle can move is by rotating around the shackle bush. The leaf spring however is not rigid and the axle moves up and down without rotating. There is a slight movement of the axle forwards and backwards, which is accounted for with the shackle, but the rotation is completely unnatural to the axle. ie , it binds. The fact that many people use it doesn't make it a good system.

 

Daan

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I don't really think there is that much science to be applied to leafsprings Guys, they move about as they please because they can Flex in any direction, all at once. Clearly the most movement is at the shackle, thats why its there. But if you throw a tape measure at the suspension while flexing you will see everything moves about quite a lot.

In my setup I used common sense, rather than heavy math and geometry charts. I made sure the bar was equal length to the front part of the spring, center of axle to center of bushing at the chassis leg. and I kept the distance from leafspring saddle on the axle to the center of axlehousing, the same at the chassis end. No matter how I Flex it now, I can twist the anti-wrap bar by hand, telling me that there is no significant bind.

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21 hours ago, Daan said:

By the way, if you think you are breaking diffs because of axle wrap, I reckon it is quite the other way round: The diff and shaft will not see any big shock loads, due to the axle being able to cushion it by wrapping the springs. So I don't think a wrapping bar is going to solve your problem. It's not a bad thing though.

Daan - the springs wrap to a point, then traction is lost & it all "unloads" with a hell of a bang which it's easy to imagine would break a diff or shaft.

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  • 1 month later...
On 13/12/2016 at 4:36 PM, Red90 said:

We made a ladder bar from a radius arm and a johnny joint.  Took a few hours, cost very little, stopped all of the axle wrap and does not interfere with articulation.  I think there is a thread on it around here somewhere.

 

100_2180.jpg

 

I like this setup. Red 90 do I need one of these please?  And please can you explain axle wrap to me, like I'm a 3 year old. Ta

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In some 25 years with parabolics I have not yet managed to destroy a diff through "flexing". I drove some Mustangs in the US back in the 80's and they had "tractionbars" under the leaves - basically a steel box section - to stop the flexing. But they had a big V8..

I must not be trying hard enough..

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3 hours ago, Arjan said:

In some 25 years with parabolics I have not yet managed to destroy a diff through "flexing". I drove some Mustangs in the US back in the 80's and they had "tractionbars" under the leaves - basically a steel box section - to stop the flexing. But they had a big V8..

I must not be trying hard enough..

The truck I show above has a 5.7 liter V8 and 90:1 gear reduction in 1st low.  35" tyres with a spring over.  The spring over make a big difference ion the torque that is applied to the springs.

Edited by Red90
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6 hours ago, Bandog said:

I like this setup. Red 90 do I need one of these please?  And please can you explain axle wrap to me, like I'm a 3 year old. Ta

As you apply torque to the axle , the springs twist on their mounts.   This causes the axle to rotate.  All leaf springs do this.  You may not notice.  The truck above has enough torque to wrap the axle 45 degrees!!  The first problem people see is "hop"  the axle rotates under load.  When the tyre loses traction, the axle jumps back and the tyre grabs again.  You then get a hopping action as the tyre load and unload.  This makes it hard to get a smooth transfer of power.  In the one I show, adding the bar made climbing much better as the tyres hooked up in a controlled manner.

Edited by Red90
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