Scrap the build? where to draw the line?- Mtbr.com
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  1. #1
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    Scrap the build? where to draw the line?

    I am really happy with the way my first build is going in terms of learning but in terms of weld quality I am thinking this is going to go to the scrap bin fairly soon.

    For example, you can see a hole in this tube.


    I was able to patch the hole with a deep breath and then a some careful follow up.


    Last night I had a similar issue on the bottom of the head tube down tube joint and on one side of the top tube head tube joint. I actually patched them without taking any photos of the hole. I will upload photos of the patch at some point but let's just say it it quite ugly. In both cases I went up to a larger rod size and simply added filler until everything was sealed.

    Where should I draw the line in terms of a bad weld? If a hole develops in a tube at what point does the frame go in the scrap heap rather then get fixed ( building only for myself not for others ).

    I have a good dental plan but I don't really want to use it. Right now my plan is to complete the build and then do a few short rides before cutting up frame #1 and starting on frame #2.

  2. #2
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    Your call - but I'd scrap it

    If I blow a hole, I scrap the tube. Honestly, it looks like you need to keep practicing your welding - don't start frame #2 until you can make a consistent bead/good penetration/not blow any holes.

    -Walt

  3. #3
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    Order up a cheap straight gauge moly and make it into a messed up looking pile of pipes with 40-50 joints, Or turn it into some tube art and stick it somewhere on a local trail when nobody is looking
    It's mostly just practice, practice, practice. Even when you start to think what your doing looks good, you'll look back a year later and be ashamed of it. lol
    I've gone through probably 150 S sized argon bottles and still feel like a noob.

  4. #4
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    You might want to get some straight gauge .065 ;-)
    I am an AWFUL tig welder currently(I have only tried it twice) but if that were my frame I might be cutting it up also. Use the tubing from the chopped up bike for practice.
    Beechwold Cycle Works
    Columbus, OH
    http://beechwoldcycleworks.blogspot.com

  5. #5
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    Thanks

    I guess it will be hacksaw time in the near future.


    Big thanks, i will go back to practice more. The main thing that causes me to blow tubes was working on the frame requires different ergonomics and different material mating vs. working on tube scraps that are just sitting on my work table. Doing a joint between the BB and the stay was two different wall thickness and I think that is where I am having the most trouble plus areas where I am in tight spots. Things that were easy on the table became much harder on the frame.

    Thanks to everyone for the help in making the decision to scrap. I have no regrets because working this frame has taught me a lot and it sets me up for knowing what I need to practice as I move forward.

  6. #6
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    I would keep on welding.. and patching holes... it's practice right? Already got it all mitered and in the jig. Think of it as very thorough practice, then destroy the frame joints afterward, re-use tube scraps for more practice.

    -Schmitty-

  7. #7
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    Exactly what I am thinking

    I plan to finish the welds then cut up the frame and put it back together as a slightly smaller frame. I figure that I can do this for a while to get a sense of working in the various angles and body positions that are needed. For me welding tight areas like the rear triangle and the inside of joints was the most difficult part to get comfortable with.

    I will also continue to work on the table until I feel ready to start #2.

  8. #8
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    Personally I would built that bike up and use it as a grocery getter, at least for a little while. Riding a bike you built, even if it's only to the corner store is motivating. But it probably needs to head to the scrap bin.

    When you do salvage that one, cut the tubes off short and then use them to weld to something thicker. mimic your different joints, especially the seat stay cluster. If you don't want to ride that bike you could just practice re-welding those tubes again and again until you feel comfortable.

  9. #9
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    Fe,

    Looking at the pics of your welds, it appears you could be more successful with proper torch attitude (position, not emotion).

    From the shape of your filler puddles, it looks like you are positioning the torch from the head tube side, angled toward your mitered tube and filling from the left. When tig welding dissimilar material thicknesses, it is a better strategy to position from the mitered tube, focusing your heat toward the thicker piece, allowing the heat to build on the thicker piece and slowly move your position to draw in the thinner tubing, filling with your rod into the mitered intersection from the tube side. This will allow for greater heat focus, control, and enable you to feed the puddle where it needs it, into the joint, preventing undercut of the thinner material.

    As a rule of thumb, always focus your heat into the unmitered section of the joint...you'll have greater success and technically more consistent beads.

    As for your frame...finish welding it up. You will learn much about position and necessary physical adaptations to your technique.

    cheers,

    rody
    As requested by the MTBR gods, I am the voice of Groovy Cycleworks, check it out... http://www.groovycycleworks.com

  10. #10
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    Quote Originally Posted by Rody
    Fe,

    Looking at the pics of your welds, it appears you could be more successful with proper torch attitude (position, not emotion).

    From the shape of your filler puddles, it looks like you are positioning the torch from the head tube side, angled toward your mitered tube and filling from the left. When tig welding dissimilar material thicknesses, it is a better strategy to position from the mitered tube, focusing your heat toward the thicker piece, allowing the heat to build on the thicker piece and slowly move your position to draw in the thinner tubing, filling with your rod into the mitered intersection from the tube side. This will allow for greater heat focus, control, and enable you to feed the puddle where it needs it, into the joint, preventing undercut of the thinner material.

    As a rule of thumb, always focus your heat into the unmitered section of the joint...you'll have greater success and technically more consistent beads.

    As for your frame...finish welding it up. You will learn much about position and necessary physical adaptations to your technique.

    cheers,

    rody

    Yes. +1 here.

    I too say finish welding up this bike (and maybe practice some welding techniques in conjunction too). There are some locations on the bike that are pretty tricky to weld. And even a cursory pass in these areas on this (not to be ridden) frame will provide some learning for you.

    I.e.
    -In between the TT & DT is a notorious spot if your frame has a short HT.
    -Underside of seat stays where they meet the seat tube.
    -CS & SS at the drop outs can be tricky of using smallish DOs. This is especially true if you've not learned some of the underlined techniques above.

    Keep going. Keep practicing. Keep learning.

    Later.
    CJB

  11. #11
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    Do your tacking in the fixture. Getting those backside tacks will be another spot where you can practice out-of-position welding.

    Once the front triangle is tacked, take it to the table where you can move it around to gain yourself the best access. Once it's done, fit and tack the rear triangle, bringing it back to the table for welding.

    Don't make the process harder than it actually is by welding in the fixture.

  12. #12
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    Thanks!

    I have been doing the tack in fixture and doing the rest of the welding on the table but for me it is still hard to get position but with time and practice I am sure I will develop the skills.

    Some of the welds went well but a few places I just goofed things.

    The rear triangle was especially hard to work on. I managed to do that area without blowing tubes but I have the feeling that my slow awkward movements resulted in beads that were a bit too thick.




  13. #13
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    You could cut it up and make a great bmx race frame...

  14. #14
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    Quote Originally Posted by D.F.L.
    Don't make the process harder than it actually is by welding in the fixture.
    I pulled this from another forum, but I was surprised to read that Don welds in his fixtures. He of course has the skills to get it done, but that's not have I was taught and what I've read. I went to UBI (some time ago now) and there we welded out of the fixture.

    My welds suck too...one day they will come together to make a frame.

    I would also like to add that I do better when I crank the heat up.

  15. #15
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    Quote Originally Posted by j.m.
    You could cut it up and make a great bmx race frame...
    BINGO!

  16. #16
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    Finish TIGing the frame. If it comes out straight enough, and you don't need to cut it up to examine your welds, you could always add some bronze fillets to the welds. This would cover up your work, add structural reinforcement, and allow you to practice fillet brazing

    Wade Barocsi

  17. #17
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    I'd also try a couple cup sizes larger and play with the gas flow. Larger cup can flow more gas at slower exit speed with less chance of sucking in bad air...if that makes any sense.

  18. #18
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    I'm a little shy on posting, especially on this thread (this is my first post), but i wanted to weigh in on whether or not to scrap this frame. I took a one-on-one framebuilding class in Denver last year, with a short 2-day TIG class beforehand (yep, didn't learn that much but it was a good start). Since then, I've been practicing welding cheaper 4130 tubes together and learned a ton...but feel like I have maxed out on this type of practice. It seems to me that you just have to start with "real-life" practice (welding frames). Even though more expensive to go this route, it seems much more beneficial to practice on the same types of joints that you will be welding - thinner to thicker, bigger to smaller, etc.

    So here's the part i'll probably regret saying: my first frame was partially welded by me and the harder joints (BB/ST/CS and ST/SS) done by the teacher. I blew a hole in the TT and DT but covered them up like FE did. Although not pretty, and with obviously too much heat put into these spots, I've ridden this bike (singlespeed cross) for several months on mostly dirt road and singletrack with no cracks, failures, etc. (knock on wood...) It is a little out of alignment but not too bad and it rides pretty good overall. I'm sure it'll crack some day, maybe soon, but I'm not that worried about it because if I survive the fall I'll learn from it.

    Point is, don't trash it. I agree with several others that have recommended keeping going on this frame. After all, it's your first solo frame and if it were me (and my first solo frame will be done shortly), I'd not only keep it but I'd ride it as a townie and use it as a test bike for geometry, size, whatever, and then hang it on the shop wall as a testament to your beginning point from where you'll only improve. How many others wish they had their first bike still - built or bought? I know I do! ...call me sentimental

    Whit

  19. #19
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    My first titanium bike had some ugly welds and held up for 2+ years before I put it in the attic for a rainy day. I'd say weld it up, then go back over it with some practice cosmetic beads to make it prettier. As others have said, don't deliver this to a customer, but you'd be shocked at how long it lasts. I've had some screw ups out last things that I thought were perfect. (stainless and titanium headers for cars/motorcycles)

    Back purging the tubes will help a great deal on the blow through. Focus your heat on the thicker piece of metal and the puddle will flow into the thinner metal.

    pick up some junk 1.5" muffler pipe or 4130 in around .080 wall and join your scrap .035ish wall tubes to it.

  20. #20
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    I agree with the comment on building it up at least to the point where you can check the geometry and sizing.

  21. #21
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    Thanks everyone, the build will continue then go to scrap later on

    I am going to complete the build and then after riding the bike around the block on smooth roads with a mouth guard in place I plan to scrap it and use it for practice. Overall it has been an good experience and I expect it that when I someday start frame #2 I will be glad to have the experience from working on frame #1 to help me remember where I can expect to have issues.

    So far this is the best weld on the frame.


    And this is the worst weld.

  22. #22
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    I had a frame that I blew a few holes in, then it cracked where I added a water bottle boss, which I gusseted/patched.

    In the end it was ugly, but I commuted on it daily for over a year before the parts went on another bike. I am in the process of reviving it.

    Small tangent, I cut up a couple of old cruisers to turn into a tandem for a buddy. The original rear half donor was a pre-ww2 skip tooth beater. It had about a half pound of rust inside the BB and tubes around it... I mean that ***** just kept coming out while I was hack sawing and filing. I even found some holes in the DT that were a combination rust and previous mod attempt made by someone a long time ago.

    The bike was still being ridden shortly before I said that I wouldn't continue with that "unsafe" frame.

    That said, I recommend you ride that bike a couple of times figure if the geometry works, etc.

  23. #23
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    I just want to add that one should always brace ones hand/arms against a fixed object to maintain a stable puddle... Those look pretty shaky and am thinking this is one of the problems. Your hands/torch should never shake.

    I make it a rule that whenever my torch hand is in a slightly uncomfortable position, I reposition the frame and the objects that I rest my hands on. I then practice the motion a few times, without even hitting the gas pedal, to see if the torch or the filler rod will be impeded somehow... and to see about where the bead should stop.

    As for burning holes the best advice I've been given is to stop immediately, let the thing cool to room temp and then shove filler quickly at a slightly lower temp.

  24. #24
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    keep her going and finish welding. next one will be better, after that easier.....so on and so on

  25. #25
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    You can practice by making some hand rests, then your hands will only have to do the stich pattern and your arms will be relaxed.

    I've done a fair bit of welding but TIG on 0.8 mm tubes scares me, the degree of difficulty is very high. With very little thermal mass I know that you want to lay down that bead fast so the heat affected zone is small, which means you have to crank up the heat to maintain penetration. A vicious cycle that needs a very good welder or a robot...

    Good luck. It is possible, you might just have to practice a lot.

  26. #26
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    I'll add that most inexperienced welders panic when they see material receding. The reaction is to stop feeding filler or, even worse, to pull the torch back. Train yourself to ADD filler when you see the material 'burning' away. Not only does this fill the emerging gap, but it COOLS the puddle, slowing or halting the growth of the hole. The better you become, the less this will happen, and the quicker you'll be able to anticipate, analyze what's happening, and respond correctly.

    Use the great advice people are giving to help speed your learning curve, but keep in mind that it will take some time before all this feels natural.

  27. #27
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    Quote Originally Posted by D.F.L.
    I'll add that most inexperienced welders panic when they see material receding. The reaction is to stop feeding filler or, even worse, to pull the torch back.
    I've also been learning how to TIG, but brazing habits sometime prevail, and I laugh at myself every time I pull the torch back or turn it away when there's too much heat.
    May the air be filled with tires!

  28. #28
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    Quote Originally Posted by 3wfab
    keep her going and finish welding. next one will be better, after that easier.....so on and so on
    I decided to finish the bike and am fairly happy with the result even though the welds are quite ugly.


    So far I have about 120 miles on the bike; the bike feels solid. I also continue to practice on the TIG and found the tips here to be very helpful as I think about someday making another bike. I hope this frame lasts long enough for my skills to improve (knock on wood).

  29. #29
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    Quote Originally Posted by Blaster1200
    I've also been learning how to TIG, but brazing habits sometime prevail, and I laugh at myself every time I pull the torch back or turn it away when there's too much heat.
    thats funny, when i started gas welding i had to fight the urge to flick the torch away also. after a bit of "re-training" it came together. keep the tip buried and keep adding filler. then when i when back to brass fillet brazing things went quicker and easier than ever.

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