Working on Frames Question

Discussion in 'Motorized Bicycle Welding, Fabrication and Paintin' started by Tabogon, Jul 4, 2009.

  1. Tabogon

    Tabogon New Member

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    I have been working on ideas for my first MB for the past couple of days. It will most likely be a Schwinn based board tracker, but I would like to try making my own tank and possibly change a few angles of the frame.

    I can not decide, mostly because I don't know, which type of welder I should get. I won't have enough for a tig welder, so that is pretty much out of the question. I know the differences between flux core and mig welding, but not which one will be better for working with bikes.

    I would also like to hear more about brazing if anyone is knowledgeable about it, seems like it would be a fun and unique thing to learn, and how it compares to the strength of welding.

    Thanks! .bf.
     
  2. Creative Engineering

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  3. the willi

    the willi New Member

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    the tig dude very sweet!
     
  4. Tabogon

    Tabogon New Member

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    Thanks Jim, I'll bookmark them and get to reading as soon as my daughter will let me rest, haha.

    I agree Willi, I would love to have a nice quality tig welder, but that one item would take my entire bonus, and I have big plans for my first bike.

    Thanks again for the replies!
     
  5. Tabogon

    Tabogon New Member

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    Any first hand experience on how strong brazing is compared to welding? Nervous about my first bike falling apart haha.
     
  6. Creative Engineering

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    It's all relative...

    A properly brazed joint will be much stronger than one that has been improperly mig or tig welded.

    Jim
     
  7. Tabogon

    Tabogon New Member

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    Thanks again Jim! I got a chance to look into the links you posted, a lot of good info. I never realized that most custom frame builders prefer brazing and how popular it is for frame building. I found a few really nice shots of a frame that was brazed, and the finish was amazing! Looked like it was made from a single piece of metal. This is definitely something I want to learn and use on my bike when I build it.

    Thanks.
     
  8. Creative Engineering

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    You're welcome,

    It is very easy to learn to braze, and as you noted it produces a really nice looking joint. Perfect fillets are easy to do. You don't have to be an expert to get good results.

    I highly recommend it for the hobbyist.

    I can best describe it as high temperature soldering. If you have ever soldered plumbing fittings, you will have no problem brazing.

    Jim
     
  9. Tabogon

    Tabogon New Member

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    One more question, if you don't mind.

    I came across a custom bike builder that uses custom cut lugs to build his frames, I was wondering what type of tool can be used to make them myself. .bld.
     

    Attached Files:

  10. Creative Engineering

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    Tabagon,

    Ya got me on this one...I have no idea.

    Jim
     
  11. Tabogon

    Tabogon New Member

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    Thank you very much, Jim.

    I have yet to find any tool that can cut that so precise the way they did, google has failed me today haha :-||
     
  12. ocscully

    ocscully New Member

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    Just about all of the Lugs used in bicycle building today are Investment Cast and come from only a handful of suppliers. Each frame builder then custom cuts/modifies these lugs, with hand tools coping saws and files to get there final shape. Link to short video YouTube - Bicycle Frame Building part 1: Lug Cutting

    ocscully
     
  13. Tabogon

    Tabogon New Member

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    Bookmarked! Thank you very much, ocscully. Can't be too hard to do with the variety of Dremel attachments I have.
     
  14. BrettMavriK

    BrettMavriK New Member

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    .

    Brazing is neat and clean if you have purchased pre-made joints. Brazing can fatigue and crack however, as it is just gripping the surface of things being joined together and is becoming the "glue" so to speak.

    I Say Weld It.
    MIG (Metal Inert Gas) - GMAW / FCAW (gas or flux core) is what I recommend if you can not afford a TIG. This method joins to pieces of steel with wire fed through a gun and arc welded. The key here is being able to penetrate the thickness of the two metals with the proper machine, thus fusing the two pieces together as if they were one unit. Metal up to 1/4" can be handled in a single pass just fine by almost any 110volt small mig welder. Another key is gun distance, angle, and speed. Mig welding, as any welding, takes practice. I use a 220 volt, 180 amp welder on my frames and I do not burn through, and I get the welding area "red hot" as well. A big mistake when welding is not getting good penetration into the materials to be joined. Although you can make a weld look pretty with the bead just sitting on top of the material, I could probably hit it with my hammer and brake the joint like a candy cane. You know when you have good penetration on a test weld if you can beat the crap out of the piece you've joined together, and it bends and deforms the piece to being almost unrecognizable; but the joint you welded never let go.

    .
     
    #14 BrettMavriK, Jul 6, 2009
    Last edited: Jul 7, 2009
  15. Tabogon

    Tabogon New Member

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    Thanks, Brett. MIG was my original plan, but I had read quite a few sites that explained that most professional built frames are brazed and that is why they can be so expensive. Is the brazing process the pros use different?

    The finished looked of brazed joints look amazing, but as I mentioned before, I don't want my bike to fall apart if brazing wasn't strong enough for daily use.

    Either way, the prices are about the same and it seems that personal brazing equipment is scarce around here anyway. It just seems the multiple uses of a OA torch would outweigh the pain of finding supplies, but safety is my first priority.

    Is it pretty straight forward to MIG weld aluminum and stainless steel? I plan on my first frame to be made of steel, but might want to play around later with different types of metal.

    Thanks.
     
  16. MelMartinez

    MelMartinez Dealer in Mexico

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    Tabogon, you need an special custom design die set. Very expensive but very high productive.

    They´re custom build in forged steel for cutting the sheet metal with the form and design you want; and there is another die set for bending each piece accordingly.

    You may look for a machine shop in your area that makes forged steel die sets and request a quotation. If you need small production, it´s not worth it.

    The forged steel die sets may produce more than 5,000 (five thousand) pieces per day.

    For small production you may as well cutting the pieces by hand with a saw blade and bend them with a hammer.

    I hope this info is what you need. Please do not hesitate to request more specific info if you need it.

    See You in the Road !!!
     
  17. Tabogon

    Tabogon New Member

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    Thanks Mel. i agree with you, after seeing how easy (time consuming, but easy) it is to cut them by hand I think I will stick to my files and dremel.
     
  18. Tabogon

    Tabogon New Member

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    I think I finally decided! I was originally worried about certain components (mostly things like seat post) breaking under stess or weight (I am sitting at 225lbs) and I was worried that brazing would not hold up under situations like that.

    However, I recently found this little blurbed from thefabricator.com website that stated: "According to the American Welding Society (AWS), the strength of a brazed joint can meet or exceed that of the metals being joined."

    Another site I was looking into for MIG welding tips had an article about brazing. The guy was totally amazed at the strength of the braze, and he stress tested the joint and found after a few dozen back and forth bends that it finally broke, but it was the steel that broke, not the brazed area.

    I also recently saw a video (will post it if I can find it again) that had a guy explaining his process of brazing a lugged BMX frame, showing the finished frame, and then showing his finished bike being thrashed and abused at a freestyle street course by an X-games rider. He eventually broke a wheel and bend that seat stays, but no joint seperations.

    I really like the way lugged frames look and the way they can be personalized by the style of lugs you use. So, with that info in my arsenal, I have come to the conclusion that brazing will be perfectly adequite for any frame I build or modify, and that anything that needs a little added strength (i.e. seat post) I will get a local shop to tig weld for me.
     
  19. Creative Engineering

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    Excellent choice Tabogon!

    I'm glad you looked into it more. An oxygen acetalyene rig is really the best, most versatile, set-up.

    I am completely familiar with TIG, MIG, and Arc welding. I don't weld for a living: but I have done enough of it to be able to make nice welds using any method when I need to.

    With this said; I still prefer brazing for thin materials.

    As you discovered; brazed joints are very strong.

    The problem I have with recommending MIG to someone who is inexperienced, (Brett I think you'll agree), is that it is very difficult to ensure that the weld has penetrated properly. A cold surface bead may appear as a nice weld, when in fact the two pieces aren't bonded at all.

    With MIG everything happens fast...you "must" have prior experience in order to "know" that the joint is truly welded.

    I would not be the least bit leary about riding a bike that had been built by creating fish mouth cuts at the joints, and then brazed.

    Jim
     
  20. BrettMavriK

    BrettMavriK New Member

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    .

    It's all really a matter of choice on these light load applications for the method used.
    My ultimate choice would be TIG welding for thin metal, but I don't have a TIG right now
    (someday soon, hopefully). Personally, I like fusing metals of like kind together to become one,
    but again that's just me. I think of brazing and I think of plumbing....that's how I'm wired.
    In my mind it's good for sealing a leak, but it doesn't register as a structural application to me because of my bridge building background. I would never dream of brazing anything on a car or truck suspension, but like I said, bicycles are a relatively light application and are built professionally this way.

    I bet you I can break a brazed joint on a bicycle frame before the tubing bends however; I've done it.

    .
     
    #20 BrettMavriK, Jul 7, 2009
    Last edited: Jul 7, 2009

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