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offgrid 
Senior Member 
Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
 Topic: 178 axle supportPosted: 04 May 2019 at 1:07pm |
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There has.
Check out the other active thread on axles for a couple of conversations I had with the sales techs at Lippert last fall. Most companies won't let consumers speak directly to their engineering staff, they keep them in the back room and feed them peanuts.  Why? They have nothing to gain except increased liability if the engineer says the wrong thing. I slightly object to the implication of the term "real" engineer. I am a real live engineer, worked as one for 40 years. There are other engineers on this forum as well. We're not all that unusual you know, you could pass us on the street and not recognize us for what we are unless we forgot to remove our pocket protectors.  |
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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Awchief
Groupie 
Joined: 04 May 2018 Location: Biloxi, MS Online Status: Offline Posts: 83 |
Posted: 04 May 2019 at 12:48pm |
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Just curious, has there been any discussion with real engineers from Lippert or FR about any of this, perceived issues, changes to axels, liability issues, etc?
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Michael
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offgrid
Senior Member
Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
Posted: 04 May 2019 at 9:47am |
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+1 The negative camber is the symptom. The disease is the tube bending because of the excessively long cantilevered ends. When it bends, it can bend anywhere or everywhere between the two support points depending on the loading on the two wheels at the time. Because its not very flexible it doesn't need to bend much to be a failure, only a couple tenths of an inch.
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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GlueGuy
Senior Member
Joined: 15 May 2017 Location: N. California Online Status: Offline Posts: 2630 |
Posted: 04 May 2019 at 9:13am |
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I also think focusing on the camber is a bit of a red herring. The real issue is the large overhang outside the frame; which results in the axle box getting bent at the fulcrum point. Anything that can strengthen that fulcrum point would probably suffice.
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bp
2017 R-Pod 179 Hood River 2015 Ford F150 SuperCrew 4WD 3.5L Ecoboost |
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offgrid
Senior Member
Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
Posted: 04 May 2019 at 8:39am |
As I said before, driving a few hundred miles without problems doesn't prove anything one way or the other with any of these fixes. How many miles did you drive on your original axle before you had a problem? And a large majority of rPod owners never have a problem. You're trying to determine whether a specific low probability event is reduced or eliminated by a given change. There are 3 ways to do that: Statistically: hundreds of trailers for thousands of miles with no failures would be required. Not practical. Experimentally: do a controlled load test with and without the change in place and show that the result is different. Not advisable. Mathematically: calculate the force required to reach the yield point of the material with and without the change and show that you have increased it substantially. That is how engineering is done. Very practical and well proven, it ain't rocket science. If you don't have confidence in that approach then I'd suggest staying off any steel bridges and out of any steel structure high rise buildings So, I chose door number 3. Both mine and Toyanvil's solutions should work fine in reinforcing the axle tube, resulting in at least a 50% improvement. Toyanvil's has a small chance of causing frame twisting that I didn't look at, but I expect it to be minimal. Unfortunately, Marwayne's design does not address the underlying problem for the reasons I've explained. |
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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StephenH
podders Helping podders - pHp
Joined: 29 Nov 2015 Location: Wake Forest, NC Online Status: Offline Posts: 6289 |
Posted: 04 May 2019 at 7:38am |
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Okay. I see now. The torsional effects of the bracket in your design would be on the riser. I would like to install something to keep mine from losing camber again. In order of difficulty, Offgrid's design is the easiest, Marwayne's is harder and Toyanvil's is the most complex. As for effectiveness, so far, it appears the outboard brackets are very effective. Hopefully, the other two designs will be effective also. How expensive was it to fabricate the Toyanvil system? It is not something I could do as while I have a wire-feed welder (from Harbor Freight), I don't think it would be capable of making the welds strong enough to not break under the forces they would encounter on the road. I also don't have lathe nor the skills needed to fabricate such a system. About the only system I could do myself would be Offgrid's angle reinforcement.
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StephenH
Happy is the man that findeth wisdom,... ouR escaPOD mods Former RPod 179 Current Cherokee Grey Wolf 24 JS |
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offgrid
Senior Member
Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
Posted: 04 May 2019 at 6:31am |
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I haven't run any numbers on the frame's ability to take torsional loads for the axle supports.
But, I'd avoid it for a couple reasons. First, the frame rails are really thin, 0.1 inch. Second, if you do twist them you would be really sorry. its one thing to pull off an axle and repair or replace it, much more difficult to do that with a frame rail when the trailer box is attached to it.
Besides, why take the risk or twisting it? Toyanvil's solution minimizes it and mine eliminates it entirely. Toyanvil, there's something that still bothers me about your axle. Did you ever measure how much crown your axle guy put in it? It sure looks like a lot more than the normal 3/16 to 1/4 inch. I think what's probably going on with yours is your axle tube ends are still bent upwards and your axle guy compensated by putting in more crown in the center. I think that's going to work out fine for you as you've stabilized everything and gotten rid of the negative camber, but its still a bit of a question why its like that in your case. |
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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StephenH
podders Helping podders - pHp
Joined: 29 Nov 2015 Location: Wake Forest, NC Online Status: Offline Posts: 6289 |
Posted: 03 May 2019 at 10:20pm |
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I would think that if the force were spread over enough area, that would not be a big concern. However, since I am not an engineer, it is only speculation on my part.
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StephenH
Happy is the man that findeth wisdom,... ouR escaPOD mods Former RPod 179 Current Cherokee Grey Wolf 24 JS |
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Toyanvil
Senior Member
Joined: 15 Feb 2019 Location: Bakersfield Online Status: Offline Posts: 157 |
Posted: 03 May 2019 at 10:00pm |
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I think it will flex into the frame rail, mine is 1/8 inch away from the frame as I did not want any load on the frame rail.
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StephenH
podders Helping podders - pHp
Joined: 29 Nov 2015 Location: Wake Forest, NC Online Status: Offline Posts: 6289 |
Posted: 03 May 2019 at 9:47pm |
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Great!!  What do you think of my suggestion for fabricating the upper brace using an L bracket with the bottom part sitting between the frame and the riser and the top part resting against the frame side (kind of like your design), with the axle mount and the adjustable support being the same as your design?
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StephenH
Happy is the man that findeth wisdom,... ouR escaPOD mods Former RPod 179 Current Cherokee Grey Wolf 24 JS |
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178 axle support