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  • Chassis Seam Welding

    Just wanted to get some input from people who have gone through the effort of stitch welding the seams in their chassis, or at least parts of it. My car is currently in a good position to attempt this as I'm fixing a hack job on an attempted rust fix on the drivers side frame rail and will be dropping the cage in thereafter. I then also plan to tie in the strut towers to the a-pillars of the roll cage.

    I'm assuming the front half of the car, particularly from the firewall forward, is the most important part to address on the S13 since everything seems relatively flimsy up there. Even though I have my car in a good position for this, time isn't necessarily on my side as I have a race coming up quick in August. I plan on boxing the front LCA's and the tension rod brackets as well as tying in my own "Nismo power brace" so it'd be nice to get the 'ground' of the suspension less spring like.

    For those that have done this, what is your experience and what seam sections do you think is the best time well spent stitching together? And if you have any pictures, please do share.
    Core4 Motorsports
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  • #2
    I don't know many classes that allow stitch welding of the chassis. Just a heads up in case you are trying to fall into a particular class.
    Chicago Region SCCA SM # 688 http://www.scca-chicago.com
    TSSCC SM # 688 http://www.tsscc.org

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    • #3
      Originally posted by eye-5 View Post
      I don't know many classes that allow stitch welding of the chassis. Just a heads up in case you are trying to fall into a particular class.
      Thanks for the heads up. I don't race in the standard bodies of racing (SCCA, NASA, etc...). Entry level endurance racing is where the car will live for now. AER, WRL, Chump Car, LeMons, and whatever else pops up that is cheap and fun and doesn't require a license The only one of the bunch I'd be worried about I guess is Chump Car, but I don't remember reading anything specifically about stitch/seam welding.
      Core4 Motorsports
      CLICK HERE for Wilwood FSL6R Radial Bracket & Rear Wilwood BBK GROUP BUY
      S14 VQ AER Endurance Racing Team

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      • #4
        I'd spend the time and energy you were going to put into boxing the lca's into seam welding. Unless someone knows of a problem with them flexing.... I just hit a concrete wall and folded my flca and am glad that it took the hit and not my subframe.

        I push my car pretty hard and never felt or saw evidence of them flexing.
        Maybe they do but I HAVE seen seams coming apart and ripping on my car so that's where I'd focus.

        In particular, the towers and the metal around them and the front radiator support.
        I just weld them up as I go but if I had more time is weld it all at one sitting.

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        • #5
          Boxing the LCAs takes like 10-15 mins each. Seam welding the engine bay takes a few afternoons even doing it quick and dirty. Big difference in time commitment.

          Boxing the LCAs will help the sway bars and tension rods work much better to locate things. Is it necessary? Nah, I'd say no. But for a few ounces of weight, a 16 Ga plate down there will definitely help stiffen stuff up.

          Seam welding the engine bay and strut towers is definitely good. Our cars, like most 90's econoboxes, is pretty light on spot welds. No harm in putting some reinforcement on the high load areas.
          '18 Chevrolet Volt - Electric fun hatch for DD duty!


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          • #6
            Maybe I wasn't clear. I did not mean to suggest that boxing the arms = same time to fully seam weld a car. I meant to suggest that between those two choices, I would spend the time he would on boxing in the arms and weld a few seams.

            No one I've heard of has had a flca failure because they weren't boxed, but many who drive these things hard have had seams start to separate, some fully.

            *I* would prioritize the seam welding and only consider boxing the flca's after the car is seam welded and caged, and his faux nismo brace installed; just using his list. boxing the flca's would be one of the last things i would consider doing, and even if everything else was done, I'd get heim jointed flca's before boxing the stockers.

            Plus, I highly doubt that, with the tc rod supporting near the ball joint, there's flex to be removed to result in things working "much better." And if there is a little flex, there's even more doubt that any of us would ever be able to measure or really notice it (not just experience a psychological effect). As always, I'm open to being proven wrong.

            and 10-15??
            your glass must be more than half full and sitting on a stack of premade flca gussets

            But hey - the joy of building cars is you get to do what you want for whatever reason you want to do it.
            Last edited by jfryjfry; 07-08-2015, 08:55 PM.

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            • #7
              Someone please make a decent instructional video for this subject in particular. None of the guys near me have a clue what I'm talking about when I try to get advice on how to get a good stitch weld going. (Except the 2 friends I have that are at work when I'm off)
              A good instructional video would make life easier for people like me that are trying to teach themselves to weld.
              Originally posted by Matt93SE
              in engrish, it's all about the length of your shaft... :P

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              • #8
                While I wouldn't call seam welding particularly difficult, I certainly wouldn't learn how to weld doing it.

                Get comfortable welding thin metal first.

                Then it's just standard procedure from there: clean the joints, weld. I've seen people do spot welds every inch or so but more common is an inch or so weld every inch or so.

                Getting the seam sealer out of the joints that have it is the most difficult part.

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                • #9
                  Originally posted by jfryjfry View Post
                  Maybe I wasn't clear. I did not mean to suggest that boxing the arms = same time to fully seam weld a car. I meant to suggest that between those two choices, I would spend the time he would on boxing in the arms and weld a few seams.

                  No one I've heard of has had a flca failure because they weren't boxed, but many who drive these things hard have had seams start to separate, some fully.

                  *I* would prioritize the seam welding and only consider boxing the flca's after the car is seam welded and caged, and his faux nismo brace installed; just using his list. boxing the flca's would be one of the last things i would consider doing, and even if everything else was done, I'd get heim jointed flca's before boxing the stockers.

                  Plus, I highly doubt that, with the tc rod supporting near the ball joint, there's flex to be removed to result in things working "much better." And if there is a little flex, there's even more doubt that any of us would ever be able to measure or really notice it (not just experience a psychological effect). As always, I'm open to being proven wrong.

                  and 10-15??
                  your glass must be more than half full and sitting on a stack of premade flca gussets

                  But hey - the joy of building cars is you get to do what you want for whatever reason you want to do it.
                  The boxing helps stiffen the LCA in bending primarily - as in the loading you get when the sway bar load goes into the LCA and reacts out to the ball joint and inner pivot. It won't be a huge change, but it will help remove compliance in the system and let the sway bar work better, which on our cars with its crappy installed position, really helps.

                  10-15 mins isn't out of the question. Cardboard template in 1 min, cut out of sheet metal in a couple of minutes, wire wheel arm 1 min, fit and tack weld in a few minutes, then finish welding around the edges.

                  I did it on both of mine. Hell, I did that, added sway bar double shear mounts, and a rod end on the inside pivot at the subframe plus installed new ball joints. I'd say I was around 3-4 hrs per arm for all that. If boxing the arms took much longer, I'd still be working on the rest of that stuff.

                  You can see some pics in my 2015 build thread.
                  '18 Chevrolet Volt - Electric fun hatch for DD duty!


                  DefSport Koni Sleeve and Spring Perch Buy!!!
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                  • #10
                    Originally posted by jfryjfry View Post
                    While I wouldn't call seam welding particularly difficult, I certainly wouldn't learn how to weld doing it.

                    Get comfortable welding thin metal first.

                    Then it's just standard procedure from there: clean the joints, weld. I've seen people do spot welds every inch or so but more common is an inch or so weld every inch or so.

                    Getting the seam sealer out of the joints that have it is the most difficult part.
                    Yep, getting the seam sealer out is the most time consuming and difficult part.

                    You definitely want to know the basics of MIG welding before doing this, but it's not very hard.
                    '18 Chevrolet Volt - Electric fun hatch for DD duty!


                    DefSport Koni Sleeve and Spring Perch Buy!!!
                    http://www.nissanroadracing.com/showthread.php?t=5902

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                    • #11
                      Whether the LCA boxing is worth it or not, I'm sure it can't hurt in making the ARB more effective which is what I'm looking to do. Remember, I can't really run fancy stuff in the racing I'm doing, with the exception of AER.

                      @Bubba:
                      MIG welding sheet does take practice, but MIG welding in general is 'easy.' Especially steel. With sheet, make sure you're using the thinnest possible wire your machine is setup for (usually 0.023"-0.025"). When laying a continuous bead (whether it's 1" or 12") on a sheet joint that has no heat sink/extra material underneath, it's an on-off-on-off...tack/spot welding procedure. 1 second tack, 1-2 seconds off, 1 second tack, 1-2 seconds off....this yields the best looking sheet metal continuous welds by far in my experience. You simply cannot just hold the trigger and blast a bead down on sheet. It will blow through very quickly. This is especially true with car sheet metal as sometimes there are areas that you simply just cannot clean well enough and makes blow through much worse.

                      With certain seams in structural areas where thicker gauge sheet is used and has multiple overlaps/layers, you can get away with a longer period of weld deposition, but again, dirty areas will be irritating. Part of the deal I guess.

                      So basically I'm going to hit anything and everything near the strut tower and fender rails. Wonder if it's worth my while to hit the frame rails underneath the car. Interesting about the radiator support, wasn't really thinking about up there, but it makes sense. Whereabouts there did you see separation? By the frame rails?

                      Some random google image pics for the discussion...
                      numerous single tacks


                      what I call stitch welding


                      won't have time for this, but rear subframe area:


                      Frame rail to fender


                      A little heavier on the weldments:


                      fender rail area




                      Inside


                      rear shock tower area
                      Core4 Motorsports
                      CLICK HERE for Wilwood FSL6R Radial Bracket & Rear Wilwood BBK GROUP BUY
                      S14 VQ AER Endurance Racing Team

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                      • #12
                        More and more weld isn't doing anything after a point. There's no more stiffness, and the weld stress drops to almost nothing. I did little tacks roughly 1/2" away from each other. Plenty of additional strength.

                        Constant seam welding of 1" or so is tough to do due to the seam sealer that is almost impossible to remove. At least if you do a tack and it bubbles up due to nasty stuff, you can grind it down and then reweld.
                        '18 Chevrolet Volt - Electric fun hatch for DD duty!


                        DefSport Koni Sleeve and Spring Perch Buy!!!
                        http://www.nissanroadracing.com/showthread.php?t=5902

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                        • #13
                          A propane torch and a little cheap pick set from harbor frieght work great for removal of seam sealer.

                          I've found setting the welder up a bit hot and going from the base piece to the top layer in quick fashion makes for good penetration and appearance.

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                          • #14
                            Originally posted by Z28ricer View Post
                            A propane torch and a little cheap pick set from harbor frieght work great for removal of seam sealer.

                            I've found setting the welder up a bit hot and going from the base piece to the top layer in quick fashion makes for good penetration and appearance.
                            How hot do you get the metal when you torch it to remove the seam sealer? does this affect overall strength any?
                            just curious since we're stepping on the lines of reality vs. theory here....
                            Originally posted by SoSideways
                            I don't care what color they are as long as they are LONG AND HARD.
                            '04 G35 Sedan 6MT- The DD
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                            • #15
                              You'll probably need to get it on the glowing red hot area to really clean it out, which is about 1300-1500 deg F. That's hot enough to affect the molecular form of the steel (going from body center cubic to face centered cubic IIRC).

                              Depending on the maximum heat, and how long it's exposed to, it can give a pretty pronounced effect to the end mechanical properties of the metal in that joint.


                              In general it's a bad practice to heat up structural steel to that high of a temperature, which is why highly loaded structures such as a padeye hole or something are typically forbidden to be flame cut.
                              '18 Chevrolet Volt - Electric fun hatch for DD duty!


                              DefSport Koni Sleeve and Spring Perch Buy!!!
                              http://www.nissanroadracing.com/showthread.php?t=5902

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