Forum Discussion

howardwheeler's avatar
howardwheeler
Explorer
Oct 12, 2018

Anyone knowledgeable about fifth wheel construction?

A couple of weeks ago I had a major frame failure on my fifth wheel. I posted about it with some pictures a week and a half ago. The main metal beam that goes to the nose cracked. We got that welded up to where it won’t crack again. But when we had torn the inside out to uncover the whole frame around the pin box and the beam that extends back to the main chassis frame, we could not find any way that the side walls of the trailer—the “box” you live in—connected to the frame in the front that supports the pin box and the whole front that extends over the pickup bed. We could find nothing obvious that was broken that would have connected the wall, floor and roof structure to the heavy rigid metal frame that extends to the front. So we surmised after having fixed the frame that the front must slightly float or flex around the metal frame. I have decided that is wrong. My pin box is now rigidly welded up, but the front wall structure can move up and down as I travel independently of the pin box approximately 1 inch. It does effect the inside closet. So I’ve now decided that what might have broken first, before the main frame broke, was whatever attaches the wall structure of the camper to the frame up front. The loss of that additional rigidity that the wall structure would have provided then allowed too much stress on the metal frame. That’s my thinking. So my question: does anyone know for sure that the front section of a fifth wheel is in fact hard connected to its rigid supporting frame, and, if so, how do they connect? I can see how that main body is connected with bolts going up through the outriggers off the main beam and then connecting to the wall structure, but we could find nothing up front. I imagine it varies from fifth wheel to fifth wheel but are there generally accepted ways the front wall structure is connected to the main supporting frame? Anyone know how a fifth wheel is put together up front? Or does anyone know somebody who used to work at Alpenlite that’s still around that would know how they were put together? I’m puzzled.
  • memtb's avatar
    memtb
    Explorer
    Oct 13, 2018
    This may not be of any help, it’s from an older (‘95) Teton brochure. And, of course, your design may be very different. Our newer brochures, did not give as detailed frame picture.

  • howardwheeler's avatar
    howardwheeler
    Explorer
    Oct 12, 2018
    Thank you very much for the information. I’m going to tear into it to see where it’s broken.
  • Dayle1's avatar
    Dayle1
    Explorer II
    Oct 12, 2018
    On some units, there is angle steel welded along the outside edge of the upper box steel frame. The bedroom wall sits on this ledge. Then there will be vertical screws thru the ledge and into the bottom edge of the wall. In other cases, the ledge is just a means of placing the wall and carriage bolts are installed horizontally thru the side wall and thru the box steel. If hung wall construction was used, then those bolt heads will be hidden under the fiberglass skin, but the nut should be visible on the backside of the box frame. I had such a unit that needed frame stiffening and with the front cap removed an extra carriage bolt was added thru the skin, but was then hidden once the front cap was re-installed. The carriage bolts were not crowned but an oversized flat head. It is also possible that horizontal carriage bolts were used but minus the angle steel ledge. And again they could be under the fiberglass skin.
  • howardwheeler's avatar
    howardwheeler
    Explorer
    Oct 12, 2018
    An additional clue: when I checked the front running lights, I pulled the whole socket out. Behind it where the wires come through is two layers of at least 3/4” plywood or rigid OSB. Then behind that is what appears to be the back side of the frame because it is a hole in metal. That’s where the wires come through. Also in looking at the exposed frame up where it holds the pin box frame, between the 2x6 metal rails that connect to the main body there is underneath that a thin, maybe 1/8” piece of flat stock that was once tack welded to the 2x6 frame. It is loose but does not appear to have been connected to anything else. That at least 1 1/2 of wood behind the fiberglass exterior has me wondering if that is not supposed to be screwed into the frame from the side. I don’t know why all that wood is there on the front side wall. It’s not the way back in the living room area, I’m pretty sure.
  • elkfarmer's avatar
    elkfarmer
    Explorer II
    Oct 12, 2018
    I am just going by what I saw at the factory in 1998. I just watched as they picked a wall unit up and proceeded to adjoin the two. I did a lot of work on it but I never had a broken frame so didn't have to do what you are doing. From what I saw it was exactly as I wrote earlier. There very well could be some ears/flanges like JSO said on the underside. My model sat on the floor and was screwed up from the bottom into the aluminum wall structure. It was not fixed to the frame. If it is moving that much I think the screws in the top have pulled out and probably a bolt or two on the main deck has pulled loose as this is a vacuume bonded wall and very rigid. You will have to take the fiberglass off from the pin area to the bay opening and access the screws from underneath
  • howardwheeler's avatar
    howardwheeler
    Explorer
    Oct 12, 2018
    Yes. The frame was inside the closet floor where the pin box section was and the frame rails were above the floor, the passenger side covered by carpet inside the lower bedroom cabinets and the drivers side mostly under the bed slide out. So how was yours connected? We found no evidence of any bolts and the outside fiberglass is completely intact. Maybe it has some places where the trim is ever so slightly moving.
  • Retired_JSO's avatar
    Retired_JSO
    Explorer
    Oct 12, 2018
    Not sure about the remainder of the side walls but the front overhang is screwed to the frame from the bottom up. Been there to weld a broken beam and saw where they had missed every other hole.
  • elkfarmer's avatar
    elkfarmer
    Explorer II
    Oct 12, 2018
    The nose section sits on the sturdy floor. The wall structure is one piece lifted into place. I would assume the nose section is bolted down to the floor since(in mine) the frame ran inside the wall(in the coach) and was covered in carpet. The flooring extended out beyond the frame to allow the nose section to rest. You will probably have to drop the fiberglass around the pin to access these bolts. That's were I would start. Hope this helps.
  • howardwheeler's avatar
    howardwheeler
    Explorer
    Oct 12, 2018
    Sorry Elkfarmer, I posted my reply before yours showed up. The frame over the nose is above floor level unlike the main lower section. So any bolting would have to be through the side wall or up from the floor into the beam. But we found evidence of neither

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