What's the best way to splice a frame?

General Mopar Tech Discussions

  1. yalpngulp

    yalpngulp Well-Known Member

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    20160531_143429.jpg On my 69 B body I am planning to change half the rear frame rail I'm wondering what is the best way to section it together for the most strength? I am planning on sectioning it about three feet in from the back before the bend
     
  2. hangn0ut

    hangn0ut Well-Known Member

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    Where ever you weld it,fish plates over it.
     
  3. yalpngulp

    yalpngulp Well-Known Member

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    can I plate the inside?
     
    Last edited: Jun 1, 2016
  4. hangn0ut

    hangn0ut Well-Known Member

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    Fish plates are plates overlapping both sides of a weld. Its possible to put them inside but thats more work than you would care to do.
     
  5. yalpngulp

    yalpngulp Well-Known Member

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    could I not just put a sleeve in and plug weld it? Or cap it?
     
  6. hangn0ut

    hangn0ut Well-Known Member

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    With the rails open like that plates on the inside is good. Fully welded plates are much stronger than plug welds. Plates and caps would be fine.
     
  7. moper

    moper Well-Known Member

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    Thicker steel (full) frames need to be plated because the strength is only provided by the thickness of the metal itself and the welding provides stress risers within the steel. The plates break up those risers and disperse the load around the seam. These rails are stamped steel and the strength comes from the welds and bends in the metal more so than the metal itself. If you butt weld it and duplicate all the spot welds you won't "need" the plate. You might want it, but structurally you'll be fine as the welded spot will be stronger than the metal on either side.
     
  8. yalpngulp

    yalpngulp Well-Known Member

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    so you are saying as long as I do a good job welding it I don't need to add any extra reinforcement? Would putting a sleeve of the same gauge metal in it be beneficial at all?
     
  9. moper

    moper Well-Known Member

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    I'm saying as long as the sheet metal you're adding is the same gage, and welded properly to ensure it's penetrated fully, and the adjoining parts are solid and the plug welds are fully penetrated, then you will not need more reinforcement in that area. That's because on a unibody chassis the chassis's strength is the sum of it's parts. That's why it's critical to get the rust out of it as a whole. It's "the sum" because the combination of bends and various spot welded connections are what causes the overall strength to be high. The stamped sheetmetal rail by itself is flimsy. But spot weld the trunk, the crossmembers, the bumper reinforcement, and the wheelhouses to it and it's damned strong.
    You certainly can add metal and "plate it" (using what - sheetmetal?!) but you're only doing it for peace of mind.
     
  10. hangn0ut

    hangn0ut Well-Known Member

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    There you go!
     
  11. moper

    moper Well-Known Member

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    Just for clarification - full frames must be plated. Atached is the welding I did 8 years ago on my W250. The rear frame is from a '76 1 ton dually. The front 1/2 is '87 W250. Frames were aligned, properly welded, and then plated inside, outside, top, and bottom. It's carried well past 4000lbs in the bed like this.

    IMG_0455.JPG
     
  12. yalpngulp

    yalpngulp Well-Known Member

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    I was planning on using other pieces from the other frame I have for the same car
     
  13. moper

    moper Well-Known Member

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    Sectioning in parts of the uni-body is done all the time and the repairs are finished to not be apparent. As long as the section you're welding in is solid, and the pieces you're welding to are solid, and you welding (butt welds and spot welds) are good there is very little overall strength added by doubling up metal in one localized area. The way the uni-body works is the stress is dissipated throughout all the welded parts. So that rail is not carrying all the stresses day-to-day. As long as the rail and the parts connected to it are solid, the rail is transferring the stress to all the parts welded to it through it's entire length. those areas that need extra strength because they do deal with localized stress are already very thick. i.e. the leaf spring shackle areas, or the junctions of the rockers and lower cowl sides. The middle of the rail is not one of those areas.

    So you can do it if it makes you feel better - but it's not needed.
     
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    • not so famous bob

      not so famous bob Well-Known Member

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      all of the above, but have u thot about exact fit square tubing welded in side of it, after the splicing ?
       
    • yalpngulp

      yalpngulp Well-Known Member

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      awesome thanks for the info. I didn't really want to add more, just wanted to do it right. I am confident it will be fine with how you explained it. One last question, can I cut it straight up and down to patch it together or should I put it on an angle to get more surface area to weld?
       
    • yalpngulp

      yalpngulp Well-Known Member

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      I have considered that exact thing and I think it would be a problem as a square tubing will be heavier metal then what the frame rail is made of therefore I couldn't get enough heat into it to make it penetrate well. But perhaps the solution to that is to just sleave it just at the joint with the same thickness material as the frame rail but as mopar said, there is enough structure between the trunk pan and everything else that welds to the frame to make it solid without having to do that. I kind of knew that was the answer in the first place and I was planning on doing it that way with just butt welding it but I got conflicting information from people that said that that wouldn't work properly so then I had my doubts
       
      Last edited: Jun 3, 2016
    • flypaper

      flypaper FBBO Gold Member FBBO Gold Member

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      the best way is to stick another rail in there and not to splice at all.
      it looks like you are 95% removed already.
       
    • yalpngulp

      yalpngulp Well-Known Member

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      you're right but I don't have the physical ability to do that so I'm trying to work with what I'm capable of
       
    • threewood

      threewood Well-Known Member

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      In my quest of searching for the correct answer in preperation of a front frame splice, I became thoroughly confused because everyone seemed to have a different opinion. One constant, however, was to stay away from a 90* buttweld. When I spliced my frame I used an arrowhead cut on both pieces and I added fishplates inside which were plug welded. I shall see.
       
    • yalpngulp

      yalpngulp Well-Known Member

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      so stay away from a straight cut?
       
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