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Bubble gum, cracks & holes....s

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  • Bubble gum, cracks & holes....s

    instead of possibly burying this query in a project build thread, it deserves its own thread...

    I have gas welded the now less-than-063 thick aluminum seat pieces for my Guzzi build. Since its the first time I've done anything like this, I made this one from scrap I had on purpose- no idea what it actually is but It forms and welds easily without seeming prone to work hardening. Seems very comparable to the known 3003 H14 I've worked with. This seat and fender are intended to be practice pieces that will be used if they are successful or be used as patterns for the next pieces. There's a lot of fitting , cutting and development needed for this seat-fender-taillight assembly that I didn't think could be achieved without real parts in hand.

    Most of the weld is ok, not great but serviceable. After tacking, I tried to weld it in short lengths to limit the bigger holes. I have a couple of burned edges and interior holes that I've built back up with an ample amount of weld.... Not perfect welds but there's now more metal than hole. In these places, there are a couple of cracks that look more like areas of failed weld (probably contamination during the attempt to fix the holes) than cracks that have been created by working the welded area. I don't have any pics right now, but will get some shortly.

    Is it more practical to make/cut & install a larger patch or to try to open & clean the cracks? I expect trying to vee & clean the cracks will be a folly on material this thin. The goal is to be able to properly fix problems like this when I encounter them, even if this actual seat becomes wall art in the end.

    TIA, guys.

  • #2

    Pictures would help a bunch. Cracks are caused by excessive over heat or back cracking due thermal expansion and contraction. To weld up the cracks, wash off all the flux, clean with a wire brush, reflux and start fresh. No need to vee, do to the thin material thickness for penetration. It is sometimes needed to cut away ugly metal to expose good aluminum to reweld.

    Cleanleness is very important. You must wire brush off any oxide, then clean with alcohol or other cleaners. I even file the edge of the sheet to prevent contamination from the sheared edge. Be sure you are using bottle water in your flux with no steel brushes or steel other wise present, steel oxide will kill the flux, which causes crap welds. With Oxy/acetylene, pick your tip size and regulator pressure per the recommend charts. For tacking set the cone length to 3 times the material thickness, to weld set the cone length to 2 times the material thickness. By shortning the cone length, torch is at a lower temp and slows down the weld process. Always set a feather on your torch to prevent oxidation.

    hope it makes sense,



    • #3
      Here's a couple of pics, Bill. Close up of the semicircular failed weld and then larger pic pointing to location of this flawed welding attempt. It appears to be a clean gap, now wheeled/ planished into itself. This was within the area where I filled or welded up a 3/4" melted hole, so probably had some failure of flux or contamination that interfered with the repair integrity. If I can clean & flux it, It will probably melt back in ok- certainly not aviation-spec, but ok for this seat this time.

      As far as welding method, I've been doing things pretty much as you describe above. I set my pressures with a vacuum/pressure gauge, which helps a lot. The smallest tip I have is the one I use and it seems to work fine. I am adjusting the cone to expedite or slow tacking or welding progress & keeping things well brushed and clean from contamination. I haven't cleaned anything with alcohol, so will get some and use it. Contamination doesn't seem to be as much of an issue as managing heat & rate of weld, which I realize is a matter of practice if the method & prep is right..

      In part, this seat effort is practice for later welding of the gas tank.

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      • #4

        I have had this happen to me. When filling holes, it is easy to be welding around the edge and as you fill with rod you cover over and not weld a part of the edge. The edge can be the base material or the edge of one weld puddle to the next weld puddle. The weld process, slight oxidation and old flux will cause the material to not flow together and you get this result.

        In a normal weld seam, you travel from one edge to the other, you don't back up or change direction mid weld. This is done for several reason, 1 is pre-heat the panel as you travel, 2 to activate the flux, weld and move on. When doing holes, it is easy to contaminate due the weld going back onto it self.

        If I develop a hole, I continue until I have the seam welded then go back. I clean off the old flux and oxidation and apply new flux. For the smaller holes, I heat the rod and ball up the end until it is the size of the hole. Then heat the part until you see the whole edge of the part become molten, then add the ball of rod. It melts in completely and completely fuses all the way around. With 3/4" (20 mm) diameter hole, it is easier to run a weld bead around the edge until filled.

        It always shows up when grinding or planishing the weld. Technically it is an inclusion and we get it in aviation with the best of them

        Clean, brush, re-weld and hope your friends don't see it

        Last edited by Bill Tromblay; 18-09-19, 06:51 PM.


        • #5
          Thanks Bill. Will do. Mum's the word.. Sshhhhh...


          • #6
            Hi Cliff. Must admit I haven't done enough practice - did buy Kent's DVD and a whole lot of gear from him, but need more seat time.

            I actually found that a larger tip worked better for me.

            Now of course everything is different in New Zealand and our tips in no way correlate to US sizings - in fact my NZ sizings in no way correlate with today's NZ sizings. Back in the 70' and 80's here it was really simple, you bought an NZIG tiny torch (Comet Junior I think) and it came with #6, #8, #10, #12 and #15 tips. You used #6 for fuse welding 20swg (1.0mm) CRS and #8 for 18 or 16swg CRS. The #15 tip was more for brazing and pre-heating. No of course it's all different, no doubt due to the EU and the fact that you can't buy a pork chop anymore with a small piece of kidney attached to the eye...

            When I started learning how to fail at O/A ali a few months back, I started with the #6 tip, fearful that anything bigger would instantly result in me having molten aluminium dropping onto my jandals (thongs in US speak - note not thong...). Well the #6 was bloody useless, even with the modest coupon size I was practicing with. Sure I could melt the filler rod, but it just sat on top in a big blobby mess. The #8 tip was better, the #10 better still and in fact I had my best results I think with the #12. The bead was flatter and the penetration more consistent. It did get a bit hot towards the end and I was rushing, but probably some flicking up of the torch would have controlled things.

            Here are a few shots of my feeble attempts at mimicking the Masters. Spending a bit more time shearing the filler rod from the sheet (marking it out for a consistent width) helped. Thoughts are that rather than using 16swg for the filler rod, I might be better trying some 18swg for a lower deposition rate.

            Bigger tip was better for me.

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            Cheers, Richard


            • #7
              Man, Richard- if my welds looked like that I probably wouldn't have started this thread..

              Seriosuly, my weld lately are far more challenged. A Meco rig is on the list, but not in the budget right now. I've got a few old torches but am limited on tip sizes here. The smallest tip for favorite old Airco Concoa is a 3. It seems to go ok but is probably too much. I can weld an inch, maybe two ok (not great) and then the area beyond the weld puddle usually drops through. Seems like too much heat soak?. Tried flicking, no good. The only thing that seems to help is to completely stop, wait for metal to cool and then resume welding. Problem is the more I weld, the longer I have to wait each time. Didn't try a wet rag to cool things faster, might have to.

              So I changed to my more clunky Purox 300,because I have size 2 and 6 tips for it. It seems more tractable, especially the 6. The 2 just wouldn't produce a puddle. Larger diameter filler rod or trimmed parent metal seemed to make it easier to manage to puddle & to pull out heat to prevent a hole. Ive got regular TIG rod and some rod from Kent that's half the diameter. The little stuff just disappears,,at least with the equipment & techniques I'm using.

              See pics- Of these 7 welds done this afternoon, the best looking one was (of course) the first weld.... Center weld on right side with big burn hole at end.

              I understand the issues with weld height, excess filler, profile of weld bead. Just having trouble consistently producing a nice looking penetration sing athe on the back. Even when the top looks great, there is usually a line visible on the back- cut edges of metal not fully incorporated into the weld puddle. Maybe that has more to do with panel/seam alignment?

              of these 7 welds done this afternoon, the best looking back side was (of course) the first weld..

              Ii can say I have no idea what this aluminum is. Maybe that's part of the problem. I've welded known 3003-some, not a lot- and it didn't seem this tough to produce a consistent result. This aluminum takes regular TIG aluminum filler rod as well parent metal rod.

              The interior welds obviously benefit from more equal heat sink during welding. I do want to learn to weld as needed, not just in ideal situations on a bench. That's one reason I welded the seat hump. I have to be able to do it when it counts, using real parts. Welding my gas tank well is the big prize. I would rather not make 6 of them in order to make one good one.


              • #8

                One thing to consider is the coupon size. Your test pieces are small and you would get different results with a 12" x 12" (300mm x 300mm) coupon. Heat distribution is very important, for a small panel you need to pull the heat away very often, like you are doing. You are getting there.



                • #9
                  Yup, as Bill observes, coupon size. I was doing 1 weld in the middle of a 300mm wide piece of scrap (a duff centre panel for my chin air dam on the Group 5) which was probably 500mm long at the start. I sheared off a 100mm piece, clamped the big bit to the bench and welded the small bit back onto it. Then sheared it off 25mm north of the weld for the next practice part. Thus there was generally a fairly realistic heat sink. On those bits you picture, you would struggle with tig. I'm shearing all of my rods now from the edge of the sheet and all I have in the shop is 5005. Particularly when starting out EVERYTHING needs to be a known quantity in my humble opinion. I even started writing down my fluxing techniques, tip size etc... as it's really easy to bamboozle yourself. Would suggest not welding on scrap you don't know the grade of. Too many variables. Just change one thing at a time if you are experimenting. The other thing which helped was making sure the sheared filler rod was not just a 12" piece (hence the pinholes from too many starts and stops). Making sure the rod was a full 36-48" helped me. I've bought some of Kent's mig wire and made a feeder, but couldn't get my head around wrestling with the resulting helix of unruly wire.
                  Last edited by skintkarter; 23-09-19, 09:41 AM.
                  Cheers, Richard


                  • Bill Tromblay
                    Bill Tromblay commented
                    Editing a comment
                    Hi, To solve the unruly wire, cut off the length you want and it can be straighten. Chuck one end of the wire in a drill and put the other end in a vice. Run the drill for mutiple seconds and it will be laser straight. The dab technique leads to a nice looking weld, hard to do with a curled wire 😊

                • #10
                  Thanks for the input, Bill & Richard. I understand the heat sink & related benefit when a larger coupon. How does this translate to an actual job piece that isn't large or ideally centered? Do you clamp it to a larger piece or pieces to provide mass for heat sink?

                  On the coupons in my pictures and others not pictured, I should have mentioned that the first weld was deliberately produced in the center of the coupon. Probably that's why that weld tends to be better. I do want to be able to manage a less-than-ideal welding need. The difficulty welding with the narrow piece is very clear to me, both before & during the task, but it's a deliberate task.

                  I'll plan to limit some of the variables and keep practicing.


                  • #11
                    Thanks Bill - I do use the drill technique on 0.9mm steel mig wire for my tiny tig ferrous welds. Works well. Kind of stepped back from the ali mig wire as I could only seem to get 5356 or 1100 and at some stage I want to do another bike tank, but with a polished finish. Gone back to the tig to keep the BMW project moving along, but shearing 5005 for filler. With a vigorous preheat, welds so far have gone pretty well and have held up to planishing flat.

                    Cliff, sorry but I don't have much experience with small parts yet so can't really add anything constructive.
                    Cheers, Richard


                    • #12
                      Any input you offer is welcomed, Richard. I'm focusing upon smaller pieces simply because that seems where I'll be working, especially in aluminum. A full fairing is part of this Guzzi project, but is a low priority at this point. 1-2 fairings like that and some sculpture concepts are the only "large" things I have in mind to do at some point.


                      • #13
                        Not that I have ever welded aluminium, but looking at your welds Cliffie, it seems to me that you need more heat.

                        Wherever there is a blob, means that you melted the rod with the flame rather than melting it in the weld-pool.

                        If the back of the weld shows the cut edges, then the weld pool was not big enough to penetrate.

                        So this can be cause by a multitude of things, so firstly I endorse all of the excellent recommendations made by Skintkarter and add these suggestions;
                        1. Try running a puddle without filler rod on your coupon. This is a good time to confirm tip size; size of the flame; torch angle, speed of travel, etc. Keep notes.
                        2. If the puddle is good it will show on the back.
                        3. When that is mastered, do the same thing using a filler rod; remembering that the rod is ALWAYS melted in the puddle never with the flame.
                        4. And then when you are happy with the appearance of the weld, try doing a butt joint, bearing in mind that you will need to travel faster to stop the puddle collapsing.

                        On the subject of welding small pieces, wet rags paced each side of the joint work remarkably well in controlling distortion on steel, and I can't think why it would not work on aluminium,

                        Cheers Charlie


                        • #14
                          The temp issue seems to be a big part of my failures, Charlie.

                          When i I get a good puddle, seems like there ends up being so much heat soak that I weld maybe an inch & then have the metal beyond the pool collapse to leave a 1/2" or larger hole. Tried flicking the torch to avoid the apparent excessive preheating beyond the puddle. Tried going faster and seem to lose my puddle. Going the recommended 2"-3" before pausing about would be nice. I'm keeping my pressures each regulated to the same either 3lbs or 4lbs (setting regulators with an external pressure gauge, not just the dials on regulators) and adjusting flame hotter & cooler. Seems viable to adjust the torch as needed to get things a little hotter or cooler, but no sweet spot yet. Same with different tips and even torches, which simply means that I am the common denominator....

                          I am am not deliberately melting rod above the pool. Some of the blobs are trying to rebuild those holes, which is a very untechical the way I do it. The others blobs often happen when I try to control the temp, when I think I see a sag happening, etc. hit the molten material with a rod. If the rod is too cool, it chills the puddle & quickly stacks up. Then I melt off the rod and try to go beyond. Trying to heat a big glob to make it flatten or go away isn't the solution.

                          I'm listening and anxious to do more as soon as there's time.


                          • #15
                            What you're trying to do is difficult, even for somebody with much more experience than you, if that makes you feel any better. If you could get you something a little thicker and bigger to practice your technique, and then step down to the the small thin stuff I believe you would progress faster. The other guys cover it pretty well, start with a bead on flat metal and then move up to a lap weld and then try the butt welds. The only thing I might add, as Bill alluded to, go buy yourself a good stainless steel brush from the welding store and never use it on anything except aluminum you have already cleaned.
                            I had the good fortune of being close enough to Kent White at Will's to see exactly what he was doing . It was remarkable how fast he was able to move and control the heat on those tiny little coupons! Its going to take you a bunch of practice to get that good. Good Luck