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  • Going to be working on a Uni-Body...

    ...and i am looking for some advice.

    first off some background on the project. The rear end of this car was damaged in a rear-end accident and am going to remove the damaged half and weld on a pristine one.

    i am wondering if anyone has done this and if so what type of weld did you use?

    i was thinking of butt welding both halves together then welding on some panels in key places for reinforcement.

    i will try and take some pictures this weekend and post them for you guys. thanks in advance!

  • #2
    If you have no experience in autobody repair (and since you are asking then you don't), please do not attempt this.

    It is not as simple as cutting off the damaged and welding on the new.

    You are talking about vehicle structure that is very important for peoples safety.

    I am not meaning to sound rud but this is a very seriuos repair, best left to professionals, I admire your willingness to tackle such a project, however this one should be passed on.
    Tim Beeker,
    T-N-J Industries
    (my side bussiness)

    Miller Synchrowave 350LX with tigrunner
    Esab 450i with wire feeder
    HH135 mig
    Thermal Dynamics cutmaster 51 plasma cutter
    Miller aircrafter 330 - sold
    Marathon 315mm coldsaw
    vertical and horizontal band saws
    table saw
    Dewalt cut off saw
    Sand blast cabinet
    lots of hand grinders
    Harris torch
    beer fridge

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    • #3
      Originally posted by tnjind View Post
      If you have no experience in autobody repair (and since you are asking then you don't), please do not attempt this.

      It is not as simple as cutting off the damaged and welding on the new.

      You are talking about vehicle structure that is very important for peoples safety.

      I am not meaning to sound rude but this is a very seriuos repair, best left to professionals, I admire your willingness to tackle such a project, however this one should be passed on.
      I must agree with Tim on this.I've been doing heavy collision for over 20 years and doing a rear clip job on a car is not a first timer project. On top of the skill you need in the welding field,you also must make sure the front half of the vehicle has no damage also......Best if you have a pro do the work.....Just my opinion.....and I've done them before. Jim
      Welding in Crete
      Syncrowave 350 LX
      Millermatic 252
      Millermatic 180 w Spoolgun
      Miller Gold Seal 155
      Miller Elite welding helmet
      JD2 Tubing bender with Hydraulic conversion
      Evolution Raptor15" SteelDry Cut Saw
      Hypertherm Powermax 30
      Some really cool hammers BIG and small

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      • #4
        Originally posted by uhohjim View Post
        I must agree with Tim on this.I've been doing heavy collision for over 20 years and doing a rear clip job on a car is not a first timer project. On top of the skill you need in the welding field,you also must make sure the front half of the vehicle has no damage also......Best if you have a pro do the work.....Just my opinion.....and I've done them before. Jim
        i have done other welding projects. this will not be my first mig project, just never done this type of thing on a uni-body car.

        this is a 4 door and the front end of the car is pristine past the C pillars. it was a low speed impact that damaged both rear quarter panels and trunk floor.

        i also have a good friend who is helping me out who has done this type of thing before. i was just wanting to get some tips from you guys (like said above) who have done this before.

        im just the type of person who asks a lot of questions...

        Comment


        • #5
          Unfortunately it doesnt matter if you can weld or not. Doing what your speaking of is more of an engineering project then anything. Stresses and loadings need to be thought of. Taking into account the cars structure was designed around a section having NO welding done to it, you are now changing that. Without knowing stress and loading vectors how can you make sure welds are in shear? Simply butt welding a panel together will have maybe only 60% of its original tensile strength. Now do you know what the metal actually is?? There are fatigue considerations depending on the base material, heat imput, etc. etc. You can see where this is going, this is not a quick and dirty project, and in some states not even legal unless you have it inspected by the DOT afterwards. Simply slapping a back half on a car, mig-pooping some filler on it, and slapping some random reinforcements is downright dangerous. Now if you want to go through the work to do it correctly I applaud that heavily.

          -Aaron
          "Better Metalworking Through Research"

          Miller Dynasty 300DX
          Miller Dynasty 200DX
          Miller Spectrum 375 extreme
          Miller Millermatic Passport

          Miller Spot Welder
          Motor-Guard stud welder

          Smith, Meco, Oxweld , Cronatron, Harris, Victor, National, Prest-o-weld, Prest-o-lite, Marquette, Century Aircraft, Craftsman, Goss, Uniweld, Purox, Linde, Eutectic, and Dillon welding torches from 1909 to Present. (58 total)

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          • #6
            A uni-body is totally different from a vehicle that uses a perimeter style frame. With a full frame under the car you can take various parts of the body, or the frame, and replace them as long as you jig everything up so it goes back together straigt. A uni-body on the other hand is its own frame, once it has been comromised it will never achieve its full strength again. The various components of vehichle with a frame are sort of like lego, while a uni-body is more like a plastic molding, if you will. There's a reason insurance companies right off newer cars that don't LOOK that bad. Mabye if it was an original numbers matching 69 COPO Camaro...
            Dynasty 200DX, first generation
            Makita 5" grinder
            Makita 14" abrasive saw
            IR SS5L compressor
            Whole bunch of hand/air tools.
            and a wish list a mile long

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            • #7
              Originally posted by Aerometalworker View Post
              Unfortunately it doesnt matter if you can weld or not. Doing what your speaking of is more of an engineering project then anything.
              Understood and willing to learn whatever is necessary

              Originally posted by Aerometalworker View Post
              Stresses and loadings need to be thought of. Taking into account the cars structure was designed around a section having NO welding done to it, you are now changing that. Without knowing stress and loading vectors how can you make sure welds are in shear?
              i have been thinking of this and since i am going to be the one driving it safety is a large concern. i do want to do this the right way. i have been thinking of a method where i will pop existing spot welds and re-weld new material at those places. this way the joints will occur at places where they were originally intended.

              Originally posted by Aerometalworker View Post
              Simply butt welding a panel together will have maybe only 60% of its original tensile strength. Now do you know what the metal actually is??
              just mild steel sheet metal.
              Originally posted by Aerometalworker View Post
              There are fatigue considerations depending on the base material, heat imput, etc. etc. You can see where this is going, this is not a quick and dirty project, and in some states not even legal unless you have it inspected by the DOT afterwards. Simply slapping a back half on a car, mig-pooping some filler on it, and slapping some random reinforcements is downright dangerous. Now if you want to go through the work to do it correctly I applaud that heavily.

              -Aaron
              i fully understand that this is no small undertaking. this is why i am asking so many questions before i do any work at all. i want to be 100% sure of what i am doing before i even start. i don't want to assume i can figure it out or like you said slap it together and hope it all holds up. i want this thing to last for a long time.

              thanks for the replies so far!

              Comment


              • #8
                I have to back up each and every one of the replies above. I did heavy collision for 16 years and this is not a job left to chance. This is not just a matter of cutting off the old damaged parts and welding on the new. This car needs to be put on a frame machine and pulled back into reasonable specs before it's even cut apart. You need the car in a full body clamp positioning and then it needs to be put back together by trained professionals with a full laser alignment system. Eyeballs and tape measure in the garage just aint gonna cut it. You are looking at some major liabilities (if death or bodily injury isn't enough for your conscience, the lawyers will get you) should any thing should ever go wrong with this car in the future. Dave
                If necessity is the Mother of Invention, I must be the Father of Desperation!

                sigpicJohn Blewett III 10-22-73 to 8-16-07
                Another racing great gone but not to be forgotten.http://video.google.com/videoplay?do...modified&hl=en

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                • #9
                  Originally posted by dabar39 View Post
                  I have to back up each and every one of the replies above. I did heavy collision for 16 years and this is not a job left to chance. This is not just a matter of cutting off the old damaged parts and welding on the new. This car needs to be put on a frame machine and pulled back into reasonable specs before it's even cut apart. You need the car in a full body clamp positioning and then it needs to be put back together by trained professionals with a full laser alignment system. Eyeballs and tape measure in the garage just aint gonna cut it. You are looking at some major liabilities (if death or bodily injury isn't enough for your conscience, the lawyers will get you) should any thing should ever go wrong with this car in the future. Dave
                  this car is for me. it is my "project vehicle" persay.

                  Comment


                  • #10
                    Originally posted by MrBurritoMan View Post
                    this car is for me. it is my "project vehicle" persay.
                    Doesn't make a process any safer for you or those involved with it.
                    Dynasty 200DX, first generation
                    Makita 5" grinder
                    Makita 14" abrasive saw
                    IR SS5L compressor
                    Whole bunch of hand/air tools.
                    and a wish list a mile long

                    Comment


                    • #11
                      A uni-body is totally different from a vehicle that uses a perimeter style frame. With a full frame under the car you can take various parts of the body, or the frame, and replace them as long as you jig everything up so it goes back together straigt. A uni-body on the other hand is its own frame, once it has been comromised it will never achieve its full strength again. The various components of vehichle with a frame are sort of like lego, while a uni-body is more like a plastic molding, if you will. There's a reason insurance companies right off newer cars that don't LOOK that bad. Mabye if it was an original numbers matching 69 COPO Camaro...
                      __________________

                      If it were a COPO, even a 9561, then he could sell the car a buy a brand new one!
                      Tim Beeker,
                      T-N-J Industries
                      (my side bussiness)

                      Miller Synchrowave 350LX with tigrunner
                      Esab 450i with wire feeder
                      HH135 mig
                      Thermal Dynamics cutmaster 51 plasma cutter
                      Miller aircrafter 330 - sold
                      Marathon 315mm coldsaw
                      vertical and horizontal band saws
                      table saw
                      Dewalt cut off saw
                      Sand blast cabinet
                      lots of hand grinders
                      Harris torch
                      beer fridge

                      Comment


                      • #12
                        You will also find that when you cut you will likely be looking at layers of metal in many areas. If you only present 2 large sections together you can only see and weld the metal on the surface in that area. There might be 3 or more layers of metal inside. "A" and "B" pillars, sills and rocker areas are examples of complex areas.

                        I just finished up removing a roll cage from a wrecked Porsche race car and presenting it to its replacement body. We cut the top off of the old car to ease removal of the existing cage and the "A" and "B" pillars were 5 or 6 layers of vairous thickness metal. I know of another car of the same model that a guy cut the top off in the same place and welded it back on. He even ground the welds down to hide them. Looks like new but I would not want to be in that car in a wreck.
                        Weekend wannab racer with some welders.

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