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Either flat or diamond will work but the tube is 40% stronger in bending if you keep it flat rather than turning it to the diamond orientation. 

For the record, the section modulus of a 3 x 3 x 3/16 tube flat is 1.86 in^3 vs 1.32 in^3 for the diamond.  I got an overhang of 13.75 inches to the center of the wheels (midpoint between the bearings) from the axle frame mounts when I measured mine. That puts the bending moment on the axle tube at the supports (no reinforcement) at 1750 lbs/1.32*13.75=18.2 ksi (18,200 psi), for a safety factor/g loading of 1.98 assuming standard structural steel with a 36 ksi yield.  So the axle is weaker than I was remembering it was from when I last did the calculation. 2g is an inadequate safety margin IMHO.

If someone (StephenH?) were starting from scratch and wanted to do something more elaborate than just u-bolting an angle under the axle like I did, I'd suggest a continuous full length tube with Marwayne's brackets at each end and flanges welded to bolt it to both the frame and the axle (replacing the existing riser). Basically it would be a bolt up combination riser and axle "doubler".  

These would probably sell like hotcakes to a certain segment of rPod owners, but be sure to get one of our resident attorneys to write an ironclad warranty disclaimer for you 

All that aside, I'm still thinking that some of the failures that are being reported are due to bent spindles, torque arms, or compressed rubber cords which reinforcing the axle tube won't help. We'll see. 

Originally posted by offgrid Either flat or diamond will work but the tube is 40% stronger in bending if you keep it flat rather than turning it to the diamond orientation.

What about a round tube as opposed to either flat or diamond?

If someone (StephenH?) were starting from scratch and wanted to do something more elaborate than just u-bolting an angle under the axle like I did, I'd suggest a continuous full length tube with Marwayne's brackets at each end and flanges welded to bolt it to both the frame and the axle (replacing the existing riser). Basically it would be a bolt up combination riser and axle "doubler".

If a round tube were used, could one drill through the existing riser and then weld the tube to the riser instead of building a new riser?

These would probably sell like hotcakes to a certain segment of rPod owners, but be sure to get one of our resident attorneys to write an ironclad warranty disclaimer for you  All that aside, I'm still thinking that some of the failures that are being reported are due to bent spindles, torque arms, or compressed rubber cords which reinforcing the axle tube won't help. We'll see.

Since I don't have the skill to do this myself, I would be a customer for such an item. As for other points of failure, in my case it was the loss of camber. Bearing wear might have also had some part but the symptoms (excess wear on the inside edge of the tires and visual tilt of the tires when viewed from the front or back) led me to feel the problem was not in the spindles, rubber cords, or torque arms. If I had a good line-up on a place that could have fixed the axle for less than I had to pay for replacing it, I would have done that instead, but I still would want some sort of reinforcement. to help prevent the problem from happening again.

Neither do I. The u-bolted 3x3 angle is about my limit. It does the same job, just doesn't look as pretty.

Your failure was almost certainly the axle tube. The giveaway is not having any crown left in the tube. That is a bent axle tube. I'm not sure some of the other possible failure scenarios (say a bent torque arm) couldn't also cause negative camber though. And we have a couple of cases floating around where the tube doesn't appear to be bent or decambered but the trailer is sitting much lower on one side than the other. Those sound like maybe damaged rubber cords.  The majority seem to be bent tubes though. 

 

Huskers, your plan is not going to work, you either have to make it in 3 pieces or drop the axle because you never be able to put it together.

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Offgrid, here is my ? to you. In the pic you can see that my wheels are just slightly slanted out. So how much torque can 3 nuts take before they strip the bolt.

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Should be about 32 fl lb max dry or 24 lubricated assuming a standard low carbon bolt and coarse threads. That ought to  develop around 5000 lbs of force which the bolt can take but I doubt your support assembly can. So be careful not to bend something (like your frame rail )

If you can apply enough force (needs to be around that 5000 lb range) then that ought to bend the axle end back and remove the negative camber but don't leave that force on it, you wouldn't have any capacity left in the reinforcement assembly to handle any future bumps. 

I never asked my local shop if they could straighten my axle because it wasn't bent, but I know it can be done. toyanvil just had his done. So you might want to try calling around some other places to see if they'd be willing to give it a try. 

Good luck!

One thing though, an axle that is de-cambered is bent. If the steel hadn't reached its yield point it would have returned to its original shape once the stress was removed (elastic deformation). Once the yield stress in exceeded it will no longer return to its previous shape (plastic deformation). It will take on a permanent strain/bend.  It will also become work hardened and more brittle.The next time it is over loaded it will take more stress to bend it further.  The good thing here is that we're taking about pretty small deflection angles because the tube is so stiff so its not like these things are getting bent into pretzels. 

Here is an interesting video discussing this and showing one way to straighten/recamber an axle. 

https://www.youtube.com/watch?v=pRyTeqYuGBk - https://www.youtube.com/watch?v=pRyTeqYuGBk

I could maybe see trying to do this at home with a high capacity jack if a safe way could be found to cradle the axle and chains. 

If a shop isn't available that will do it, the same basic idea should work for the torsion axle but you would need probably a 1/4 inch thick or better short piece of 3 inch steel angle to protect the torsion axle tube from getting pushed in by the bottle jack. If the axle is still crowned you could place the jack at the frame attach point on the side that shows negative camber. If its flat in the middle then place it in the middle. Not for the faint of heart, but better than just cranking down on the 1/2 inch bolt I think. Take your time, release and measure, and please be careful. 

https://www.youtube.com/watch?v=VzRZP41bw7U - https://www.youtube.com/watch?v=VzRZP41bw7U

I just literally stumbled over this you-tube video, I have no idea of the reliability/accuracy of the guy's talk but it sure is interesting.

https://www.youtube.com/watch?v=FtXRGOadTKU - https://www.youtube.com/watch?v=FtXRGOadTKU

And the attachment of the frame extension in the video by Happy makes me wonder whether welding the extension to 0.1" thick frame walls is really going to be strong enough to support the new axles.  But this is something for our highly qualified engineers and metal crafters to weigh in with their views.  

If I was going to try to put a new axle on our Pod with attachment points further outboard, I think I'd like to use some kind of a box or channel iron base attached under the existing frame that would not twist the frame members and would be strong enough to have its attachment points further outboard.  But this  is something that our very capable engineers and metal crafters should weigh in on.  Sadly, they didn't teach me any of that stuff in law school.  

Take another look at the first video. The axle is tied down by the chains on both sides, which go from the axle, over the jack, and back to the axle on either side. So the jack just tensions the chains and pushes on the axle. Nothing should move or come off the ground. The angles the chains make with the axle need to be kept to about 45 degrees or so as the first video shows. Shallow angles will just result in the chains sliding along the axle. So, you'll end up bending a couple foot sections of the axle a little at a time.  The jack will probably need to be at least 10 tons capacity. 

I think its actually pretty safe if you leave the wheels on, which you'd want to do anyway so you can see the camber angle.  If the jack slips out of the chains it will just fall down. Chains aren't like wire rope or cables, they don't really stretch much so they're not going to fly around if the tension is released. Even so, if you try this, stay off to the side of the chains while operating the jack, and take it slow. 

You have the 100% right. Welding those extensions on the frame tubes isn't the best idea. The frame tube is going to get a lot of torque applied to it that way because the bump load doesn't act through the center of the tube like it does using the normal risers. So the frame tubes will tend to want to rotate outward at the bottom.  

this looks like an easy mod that the earlier axle support, just need a welder  :-)

Interesting thread and do like what you've done to get outboard support to the axle. In another thread (and I think mentioned above) is your axle re-enforcement. I ask, vs. having the angle bent, could you place a 1-2" section (piece) of the 1/4" steel in the middle, then clamp the ends? My mind says that would increase the support, but also says I've added stress already and possibly weaken it.

My alternative is a bit more complicated since I fabricated brackets. However, the process of bending the angle using a tow chain and hydraulic jack would work if you simply wanted to bend it and then use the U-Bolts to clamp it in place. See my mods for how I did it.

Edit: This is the specific post about that:  http://www.rpod-owners.com/forum_posts.asp?TID=7712&PID=124460&title=our-escapod-mods#124460 - http://www.rpod-owners.com/forum_posts.asp?TID=7712&PID=124460&title=our-escapod-mods#124460

Looks like my second thought was better.. Glad to see you folks went through that and worked through it. 

Thank you for posting the link.

Now to read more of it.