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  1. #1
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    Question 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. #2
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    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,
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  3. #3
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    Quote 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
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  4. #4
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    Quote 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...

  5. #5
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    wisconsin
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    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"

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  6. #6
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    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...
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  7. #7
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    Quote 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

    Quote 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.

    Quote 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.
    Quote 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!

  8. #8
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    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!

    John Blewett III 10-22-73 to 8-16-07
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  9. #9
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    Quote 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.

  10. #10
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    Quote 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.
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