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  • Seam Welding race car body

    So I've got this old datsun that I'm building into a road race car. I started seam welding it, but got tired of it because of the difficutly and sub-par results. I'm using 030 wire and pretty low settings. My main issue is simply getting everything clean enough. After the body was spot welded at the factory, seam sealer was applied, which found its way in between the layers. When I try to stitch weld the seam, the stuff bubbles out and makes the weld look like crap/burn through/catch fire/etc...
    I've been using a mapp gas torch followed with a wire brush in an attempt to get the sealer out, but I need a better method. Any ideas?
    Lincoln SP175
    Craftsman O/A setup
    TA185
    HT30 plasma
    HF 6x4 bandsaw
    Cadillac 1440 lathe
    Tree 2UVR mill
    HF tube roller
    Bead roller
    Pro-Tools 105 bender

  • #2
    Acid dipping....(assuming you've got $1500 to blow)

    I did my rally shell using liquid nitrogen. Spray it on, wait until you hear "crinkling" (the sound of the sealer popping off of the metal), then whack with a chipping hammer. Those big tar sheets come off in big hunks, and all the little stuff in the joints will fly out (wear safety glasses). A quick run through the seam with a dental pick to get out any cling-ons and it was ready to weld. Really quick, and no fumes or sticky mess like with the torch and wire brush. This was how Safety Devices (UK Motorsport Company) used to do all their factory cage installs in street cars (early-90s).

    Mine went great with this procedure (and my MM210 with 0.030 L56).
    Millermatic 210
    Dynasty 200DX
    http://ca.geocities.com/[email protected]

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    • #3
      start over with new clean aluminum LB

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      • #4
        Unfortunately, the chemical dip is out of the question, and I have no idea where to get liquid nitrogen.


        Originally posted by tieler View Post
        start over with new clean aluminum LB
        The body is steel. Its not a tube frame car, or else I would't be seam welding it.
        Lincoln SP175
        Craftsman O/A setup
        TA185
        HT30 plasma
        HF 6x4 bandsaw
        Cadillac 1440 lathe
        Tree 2UVR mill
        HF tube roller
        Bead roller
        Pro-Tools 105 bender

        Comment


        • #5
          Your local gas supplier should be able to get you liquid nitrogen. Not sure about the regulator/dispenser though.

          Liquid nitrogen is used regularly in Dr.'s offices to "freeze warts".

          If my memory serves me correctly, "dry ice" is also nitrogen in a solid state.

          I think the idea of freezing the joint makes the most sense.
          SundownIII

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          • #6
            Originally posted by SundownIII View Post
            Your local gas supplier should be able to get you liquid nitrogen. Not sure about the regulator/dispenser though.

            Liquid nitrogen is used regularly in Dr.'s offices to "freeze warts".

            If my memory serves me correctly, "dry ice" is also nitrogen in a solid state.

            I think the idea of freezing the joint makes the most sense.
            For some reason, I'm thinking that dry ice is CO2 in a solid state.

            LB, I've noticed that Airgas seems to be a liquid nitrogen supplier to large corporations, not sure about smaller quantities though.
            HH210 w/spool gun
            HTP Invertig 201

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            • #7
              Originally posted by 1990notch View Post
              For some reason, I'm thinking that dry ice is CO2 in a solid state.

              LB, I've noticed that Airgas seems to be a liquid nitrogen supplier to large corporations, not sure about smaller quantities though.
              You are correct, dry ice is CO2 in solid state.

              I got my LN2 from a local dedicated supplier, but I know plenty of people who've done it through Praxair. You need a LOT. Like, I used 250L of it (that is a roughly man-sized dewar) to do my entire car. Costs about a buck a litre, and my suppliers threw in a length of the correct hose with a valve and length of copper pipe on it. Just point and shoot!
              Millermatic 210
              Dynasty 200DX
              http://ca.geocities.com/[email protected]

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              • #8
                Here's what I'm picturing.....I hose down the inner fender/framerail seal with LN, and smack it with a hammer. Frame rail and inner fender shatter, left hanging in place by piece of stubborn seam sealer.

                Maybe I'll give that a shot...seems a little expensive though to blow $250 on a consumable for this.
                Lincoln SP175
                Craftsman O/A setup
                TA185
                HT30 plasma
                HF 6x4 bandsaw
                Cadillac 1440 lathe
                Tree 2UVR mill
                HF tube roller
                Bead roller
                Pro-Tools 105 bender

                Comment


                • #9
                  Well you could always just get a smaller amount to see if it works first

                  A small dewar you could pour from shouldn't be more than $20, just dump it on until you hear that "crinkle" sound, then hit with a welder's chipping hammer (or you'll wear your arm out real quick)...should go flying off!

                  I'll try to post some pictures from my adventure with it after work
                  Millermatic 210
                  Dynasty 200DX
                  http://ca.geocities.com/[email protected]

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                  • #10
                    Wish we had thought LN when we were building our Celica circle track car back in the 80s.
                    Lots of hammers and scrapers in the 90+ degree heat of South Carolina. We cut the entire car out with a Lincoln buzz box until it wouldn't hold itself up anymore and then put the strength back in it with the cage.

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                    • #11
                      Could you straddle the seams with strips of sheet metal, then weld those to the panels, essentialy bridging the seams?
                      "Good Enough Never Is"

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                      • #12
                        Dewar:


                        Car on its side (we don't need no steeenkin rotisserie!):


                        Painted welded seams:


                        Might be a few more interesting ones in the album:
                        http://s71.photobucket.com/albums/i1...car/?start=all
                        Millermatic 210
                        Dynasty 200DX
                        http://ca.geocities.com/[email protected]

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                        • #13
                          Dewar's


                          Weldor on Side...



                          Sorry...just can't help it....
                          "Good Enough Never Is"

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                          • #14
                            Hotfoots idea looks a lot easier....I'll try that first. It'll probably work, because afterwards, I probably won't care about seam welding the car.
                            Lincoln SP175
                            Craftsman O/A setup
                            TA185
                            HT30 plasma
                            HF 6x4 bandsaw
                            Cadillac 1440 lathe
                            Tree 2UVR mill
                            HF tube roller
                            Bead roller
                            Pro-Tools 105 bender

                            Comment


                            • #15
                              Originally posted by LBHgti View Post
                              Hotfoots idea looks a lot easier....I'll try that first. It'll probably work, because afterwards, I probably won't care about seam welding the car.
                              You mean drinking a bunch then taking a nap?

                              Consider very carefully what you think you might gain by doing it that way. You pick up a bunch of weight for the extra metal, and I don't think the joints will be any more resistant to flexing that way (the goal of the whole process afterall). Unless you're gonna join the two pieces directly togather in the existing joint, I just wouldn't bother and spend my time doing something else. $0.02
                              Millermatic 210
                              Dynasty 200DX
                              http://ca.geocities.com/[email protected]

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