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Thread: Brazing Frames

              
   
   
  1. #1
    teddillard
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    Brazing Frames

    OK, most esteemed Elmotians. I'ma braze some stuff on my frame.

    I'm using that cute little Berzomatic Mapp/Ox torch. I've got a little tab to put on for the foot brake light switch, and a plate reinforcing the rear tubes where they split (under the seat), which was a standard mod in the day. It's not a repair, and otherwise the frame is in good shape.

    My strategy:

    Stay away from the existing welds, so as not to weaken them. I probably won't go less than a half-inch near them.

    Though I'm not worried about heat treating the frame after the work since it's most likely a non-tempered mild steel, I'm just going to give the area a good general heat up and gradual cool down to relieve stresses after the bead is done.

    Any thoughts? Advice?

  2. #2
    Moderator Nuts & Volts's Avatar
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    It doesn't side like its any super critical part so go for it. Check the "welds" every so often to see if they are failing in any way. If they look good, maybe move onto something a little more critical to braze on.

    Good Luck. I don't know enough about brazing to give anymore feedback
    Whats under my tank may shock you!!! R6 Build, Blog/, [/URL] OSU Current webpage

  3. #3
    Senior Member yankee1919's Avatar
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    Hello Ted,

    Sounds like your set up is good. My only suggestion is to keep the area where brazing is going to go paint and oil free. Use some sandpaper and alcohol to remove any residue.
    Use clamps and or jig to keep tab from moving. Warming up the area prior to brazing and cooling down is also a great idea.

    Lets see some pics

    Tony
    Los Angeles.

  4. #4
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    Tony is right about keeping it clean. The cleaner the better.

    Brazing is very strong and in many cases is stronger than the frame tubes. At the track I have seen cases where the tubes ripped at joints but the brazes held.

    I am a huge fan of the gas fluxer if you get seriously into it.
    http://www.gasflux.com/equipment.html
    It introduces the flux into the flame so the filler flows really nicely and the joint does not get all fluxy.

    I am also a huge fan of the Meco Midget torch. Its very simple and elegant.
    http://www.tinmantech.com/html/meco_midget_torch.php

  5. #5
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    Brazing is a great way to build frames. Back in the day ( before carbon fiber ) most bicycle frames were brazed.
    Just keep in mind that Brazing is not Welding.
    Brazing has the advantage in that the temperature is less than with welding therefore there is less temperature stress on the frame.
    But, Brazing like it's lower temperature cousin soldering does NOT melt the two pieces of metal being joined. With brazing the two pieces do not flow together and become one continuous piece of metal. Gussets are used to increase the surface area for the braze filler to adhere to.
    "obstacles suck but challenges are fun"

  6. #6
    teddillard
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    Cool, thanks! I think technically what I'm doing is "braze welding" rather than brazing. Here's that great link again: http://www.esabna.com/EUWeb/oxy_handbook/589oxy14_1.htm

    I just made the bracket, now I've gotta prep the frame and figure out how to clamp it.

  7. #7
    teddillard
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    SUCCESS! I was able to get the little bracket tacked on, second try. The first try, I underestimated how much heat the frame tubes tapped out, so I had to let it cool and clean it up again. I tacked the top so I could bend it into correct alignment before the final beads on the bottom.

    Gotta go see The Hobbit with the boy, so it's got to wait.

    Oh, yeah, no photos or videos 'cause the camera battery is dead. I know. Irony on so many levels.

    edit: Just an update, I went ahead and cleaned up the soot and hit it again with the final bead. Looks OK (nothing a grinder won't pretty up ). The bigger gusset I wanted to do is bigger than the stock I have at the moment so I'm probably going to wait on it. Next project... kickstand maybe? I gotta tell you, I LOVE this little torch!
    Last edited by teddillard; 12 January 2013 at 1341.

  8. #8
    teddillard
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    Here's the bracket for the stop light switch:


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  10. #9
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    Excellent Ted!

  11. #10
    Member Red's Avatar
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    Brazing was state-of-the-art at one time Ted. This is a little Alfa Romeo C Sports racer I built many years ago with mild steel tubing and nickel/silver brazing rod. It was strong, but I have seen brazing joints fail. IMG_0087.jpg

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