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Old 07-07-2013, 10:51 AM   #51
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Just wanted everyone to know that we do have main beam failure. Like I said we have the bunks up fron and they are in an "L" shape with one set of bunks laying across the front. That set of bunks actually has a jacknife sofa underneath. Last night my son had a friend stay over. I was pulling the sofa out to make it a bed (something I've done a million times over the years) and I noticed the sofa was hard to pull out and that when I got it out it was slanted quite a bit. I looked underneath it and saw the whole platform that the sofa sits on was extremely bowed.
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Old 07-07-2013, 11:28 AM   #52
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...Welding softens the steel around the heated joint. Six years of softness and flexing cause the paint to loose adhesion giving way to rust, further weakening the area around joint. The frame should have been assembled down to the suspension brackets and then hardened...
New one on me.
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Old 07-07-2013, 11:40 AM   #53
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New one on me.
x2 for me
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Old 07-07-2013, 11:49 AM   #54
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I've seen tags or warnings on the frames of tractor trailers and semi tractors that said not to weld on the frame.
I've never heard of that on an RV frame.

This frame has failed. The trailer can be saved. It needs work by a pro.
I disagree that the pro needs specific RV experience/training but that's OK too.
Any good welder who knows his stuff should be able to straighten what's
bent, add some more steel to beef it up and weld it back together.
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Old 07-07-2013, 12:18 PM   #55
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Just wanted everyone to know that we do have main beam failure. Like I said we have the bunks up fron and they are in an "L" shape with one set of bunks laying across the front. That set of bunks actually has a jacknife sofa underneath. Last night my son had a friend stay over. I was pulling the sofa out to make it a bed (something I've done a million times over the years) and I noticed the sofa was hard to pull out and that when I got it out it was slanted quite a bit. I looked underneath it and saw the whole platform that the sofa sits on was extremely bowed.
Sorry to hear that, as I take no pleasure in being right about what failed.
If I may offer a suggestion, do not allow the repair guy to just straighten that front beam and patch it up. This is the opportunity to cut that weak beam out and replace it with a much stronger structure.
As an example, if it is a single 3-inch by 6-inch rectangular steel tube, you could put in two 2-inch by 6-inch rectangular tubes side-by-side, welded together as a unit before putting it up into place. A good welder will probably have lots of good ideas about where to put extra braces and gussets as well.
It sucks, but after this, your frame will be much improved, and you won't ever have to worry about it failing again, while the rest of us will have to continue to watch our frames after every trip!
Hope it all works out for you.
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Old 07-07-2013, 12:51 PM   #56
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Or you could replace it with the same dimension piece if its made from a thicker steel.
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Old 07-07-2013, 08:08 PM   #57
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Or you could replace it with the same dimension piece if its made from a thicker steel.
Of course, but my thought was to double the number of webs, plus maybe increase the overall size of the beam a bit. When I design structures, I tend to over-engineer the most critical elements. This beam is the most critical element in any fifth wheel frame, as it takes all of the pin weight of the camper.
I am very tempted to strip off the aluminum cover under my fifth wheel area, and reinforce this structure long before any fatigue has set in. It would be a lot easier job doing it now.
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Old 07-07-2013, 08:27 PM   #58
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...I am very tempted to strip off the aluminum cover under my fifth wheel area, and reinforce this structure long before any fatigue has set in. It would be a lot easier job doing it now.
Make sure you post pictures of your undertaking.
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Old 07-07-2013, 08:42 PM   #59
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Make sure you post pictures of your undertaking.
I didn't say I was definitely going to do it, but if I do, I will post a detailed description of the engineering behind the modifications, and pictures to illustrate. I know that I can double the strength of the structure with little additional weight. Too bad the factory didn't do it to begin with.
Considering all the creaking and groaning the camper does when I lower the weight onto the hitch, there is obviously far too much flexing going on.
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Old 07-08-2013, 12:54 AM   #60
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I am considering a Trail Air Tri-Glide Pin Box for my 8289WS. Do any of you structural engineer types think that this might help in mitigating this type of stress failure?

I have a very heavy RAM 3500 Cab & Chassis that can jerk that pin box around.

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