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 am the total opposite, I think brazing and I think of soldering. I use to race r/c cars and would solder my own battery packs together and I remember how hard it was to force those battery bars off (stress test of course) So I can only come to the conclusion that brazing will be much stronger on a bicycle application.

    The final decision really came after I did a lot of research and found how much can be done with an oxy-acetylene torch, as Jim mentioned. It is the fact that I can gas weld, braze and cut metals that make it the best choice for my garage.

    I figure for custom items (i.e. tanks, frame panels) can be done easily with brazing and have a beautiful finish, and any types of repairs or for items like custom motor mounts I can use gas welding with confidence that it won't break easily.

    And cutting stuff is just fun! laff
     
  2. the willi

    the willi New Member

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    Brett you right right about the heat but like jim said if you don"t have experience the tig is most likely the cheapest and most common way for someone to learn! how very good ideals!
     
  3. Tabogon

    Tabogon New Member

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    I actually might revert back to mig welding. I have to double check, but I don't think gas welding is permitted in military housing. :confused:
     
  4. Creative Engineering

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    Tabogan,

    I would ask about welding in general before buying anything. I've talked to a few people who had access to equipment and shop space on base. I assume you have already checked into this.

    As a matter of coincidence I fired up the torch today to save one of my sprocket adapters.

    I was rigid tapping the parts, and one of them had a shallow hole. The tap bottomed out and snapped flush with the part. Taps are hardened, and they usually shatter leaving a jagged end that is impossible to grab.

    I was able to heat up the tap and drop a little bit of brass ontop...the brass won't stick to the Aluminum. While it was hot, I used needle nose pliers to position a 1/4" bolt over the broken tap. Once the bolt was cherry red the brass wicked up the threads and the two pieces were bonded.

    The broken tap came out with ease.

    Jim
     

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  5. dillon_b12

    dillon_b12 New Member

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    Having some experience in MIG and primarily TIG, TIG would have to be my first recommendation. Like someone already said, MIG happens so fast that you have to know what you are doing right off to get a nice weld. Everything about TIG is in your control, heat, amount of filler, etc... are all controlled by the user. This can be a good thing and a bad thing. Inexperienced welders may struggle with applying the correct amount of heat or filler or having an improper torch angle, etc...

    I have 0 experience with brazing but it has been used for years by the pros and it obviously works for them. The key to welding is that your joint should ALWAYS be stronger than your material so welding method doesn't really matter provided that the weld joint is done properly.

    To test your weld strength weld up a simple T-joint. Then constrain one leg of the joint and apply a load to the other leg until something gives(tube bends significantly, tube breaks, blah blah). As long as the material fails before the weld, you're good to go.

    Another way to check is to weld a joint up and then saw it lengthwise to check for penetration.

    Notice on this 1.25"x.065 4130 test piece I did a while back that the failure is outside the weld joint(not my best welding but it'll work):
    [​IMG]

    Brazing will likely be the best method for you since TIG welders are very expensive and a oxy-acetylene torch is an extremely valuable shop tool even if you never do a single braze. Heat treating, stress relief, heating parts for press fits, heating stubborn rusted bolts to get them to loosen, and cutting are only a small sample of the many uses of a good torch setup.
     
    #25 dillon_b12, Jul 16, 2009
    Last edited: Jul 16, 2009
  6. Tabogon

    Tabogon New Member

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    dillon_b12- Thank you very much for the info, and I completely agree that an OA torch would help me the most in my garage.

    Good news is that I can't find anything in our lease papers about welders or welding. Now I just have to wait for the money to come in!
     
  7. 2door

    2door Moderator
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    Tabogon,
    Did you know the Wright brothers brazed their airplane frames together? And weren't they really bicycle mechanics? :) I use TIG primarily because I have it and feel confident using it but brazing is good tool to know, and much cheaper than TIG. Once you master the art, you can do some amazing things with brass. Good luck. Keep us posted on your frame fabrication.
    Tom
     
  8. Tabogon

    Tabogon New Member

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    I will most definitely keep you guys posted, I have a great project idea in my mind that I will put on photoshop soon.

    2door, you think the same way I do, I read the wiki on brazing and saw that it was almost a dying art, that made me want to learn it even more. Preserve the Past!
     

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