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Thread: Brazing Tab Type Dropouts

  1. #41
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    Default Re: Brazing Tab Type Dropouts

    Quote Originally Posted by e-RICHIE View Post
    When I used to use tabbed dropouts, at last 12" of brass rod would be fed into each joint (that's inside...). I never used gravity; the parts were always on their side, and filler metal was fed in, and heat would draw it in left/right or right/left. ...
    First, thank you sir, for your kind generosity and guidance.

    I'm surprised by the relative scarcity of (detailed) videos online demonstrating 'Brazing Tab Type Dropouts', particularly demonstrating how to 'fill the big gap under the arch'.
    I did find a video demonstrating most of the prep and brazing processes;
    https://ms-my.facebook.com/ChapmanCy...5401013849050/

    I've mentioned the video above as a 'visual reference' to make our written communication a bit easier. About half way into the video he begins to add filler from the tips of the 'half-moon', and capillary action sucks filler into the slots. Unfortunately, the process of 'filling the big gap under the arch' is not shown in detail(skipped) in the video.

    When you mention, "filler metal was fed in, and heat would draw it in left/right or right/left," how is your technique similar or different from that shown in the video?

    How do YOU 'fill the big gap under the arch'? (i.e. aim the flame into the tube and touch rod onto the dropout inside under the arch and build up to the top of the arch inside? Or add filler from the top inside the arch and let it flow down and build up?) It seems that there would be a limit to how much can be further added (with ease) from the slots once the gaps are initially filled.
    Jihoon Jo

  2. #42
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    Default Re: Brazing Tab Type Dropouts

    There are few videos online because most of framebuilding, the profession not the hobby, precedes the internet and also died a slow death before its arrival. I haven’t seen the video you link. How do you / how does one feed the filler material into the cavity so the joint has integrity? Practice. Line up some twenty assemblies and braze them. Do it again. Pay attention to the differences each time. Sounds expensive, maybe even tedious? It’s a lot less of an investment than working years for free or little money in order to leave with the same end result. PS Take a brazing class too. This will expedite the learning curve.



    Quote Originally Posted by Ahmdo Molah View Post
    First, thank you sir, for your kind generosity and guidance.

    I'm surprised by the relative scarcity of (detailed) videos online demonstrating 'Brazing Tab Type Dropouts', particularly demonstrating how to 'fill the big gap under the arch'.
    I did find a video demonstrating most of the prep and brazing processes;
    https://ms-my.facebook.com/ChapmanCy...5401013849050/

    I've mentioned the video above as a 'visual reference' to make our written communication a bit easier. About half way into the video he begins to add filler from the tips of the 'half-moon', and capillary action sucks filler into the slots. Unfortunately, the process of 'filling the big gap under the arch' is not shown in detail(skipped) in the video.

    When you mention, "filler metal was fed in, and heat would draw it in left/right or right/left," how is your technique similar or different from that shown in the video?

    How do YOU 'fill the big gap under the arch'? (i.e. aim the flame into the tube and touch rod onto the dropout inside under the arch and build up to the top of the arch inside? Or add filler from the top inside the arch and let it flow down and build up?) It seems that there would be a limit to how much can be further added (with ease) from the slots once the gaps are initially filled.

  3. #43
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    Default Re: Brazing Tab Type Dropouts

    Quote Originally Posted by Eric Estlund View Post
    The finesse isn't so much in getting it in there, as not getting it everywhere you don't want it on the outside. ... .
    To fill the 'cavity'(between tube arch and tab), do you keep feeding rod from the outside in(?) via the gaps between the tab and tube's slot(?) or feed directly into the 'cavity' from inside, perhaps each tip of the 'half moon' (from the inner side), narrowing the cavity towards the center, then add a final dab to fill a central hole?

    Thank you
    Jihoon Jo

  4. #44
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    Default Re: Brazing Tab Type Dropouts

    Quote Originally Posted by Ahmdo Molah View Post
    To fill the 'cavity'(between tube arch and tab), do you keep feeding rod from the outside in(?) via the gaps between the tab and tube's slot(?) or feed directly into the 'cavity' from inside, perhaps each tip of the 'half moon' (from the inner side), narrowing the cavity towards the center, then add a final dab to fill a central hole?

    Thank you
    Eric is spot on!

    It really is a "feel", experience thing. Unless you're just "the guy", or very lucky, it will take a while to get this figured out reasonably well.

    Random things:
    • Definitely practice on some cheap parts you'll toss
    • I use an AW204 size tip; (I'd use a 203 if I didn't have a 204...and I sometimes think I'd rather use a 203)
    • Preheat the "rest" of the DO enough that it doesn't heat sink the heat from the braze area; big flame for that tip for this step; you want to preheat with alacrity...don't dally; heat from multiple sides for this step
    • Focus heat on the DO, at the feed area, avoiding (overheating) the stay as much as possible until very near filler flow temp, angling into the bore a bit
    • I do them flat, just a skosh down slope in direction of desired flow
    • Fixture so you can flip it over easily without putting the torch down; I clamp a flat piece of metal or a round file or similar in the vise and slide the fat end of the stay over it
    • Once filler can start to flow I turn the flame down a bit (it's still sizeable, just not maximum), aim the flame generally into the cavity to encourage it in that direction
    • MOL half a rod per entire DO (half for for all of one DO/chainstay...maybe 1/3 for seat stay)
    • When meaningful amount of filler is inside I start heating the stay too, just far enough, and just enough to make room for more, still aiming flame largely into the bore....I sorta flame brush the filler down the tube while feeding a bit more filler into the end trying not to get it so hot the brass goes everywhere
    • Big flame for preheat (of heat sink areas of DO and initially the feed areas), smaller (but not tiny by any stretch) for the actual brazing; not red hot but enough so the heat you're trying to put into the braze area isn't thermo sucked to the back of the DO
    • Turn it down even more to fill any pock marks that develop at finish time
    • I flux only the areas that are to get filler, plus a little "feed approach area" on the DO..."brass" likes to run everywhere; I no longer slather flux everywhere; I do apply and then finger wipe off flux down the stay for some inches, just as oxidation protection of the stay
    • I'd hate to use LP for this operation...needs the heat well focused, not everywhere; many use LP but it certainly wouldn't make my life easier for this operation!
    • Did I say to do some practice stays/DOs first? You'll be really, really glad you did.
    John Clay
    Tallahassee, FL
    My Framebuilding: https://www.flickr.com/photos/21624415@N04/sets

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    Default Re: Brazing Tab Type Dropouts

    Quote Originally Posted by jclay View Post
    Eric is spot on!

    It really is a "feel", experience thing. ... it will take a while to get this figured out reasonably well.

    Random things:
    • ...
    • Preheat the "rest" of the DO enough that it doesn't heat sink the heat from the braze area; big flame for that tip for this step...
    • Focus heat on the DO, at the feed area, avoiding (overheating) the stay as much as possible until very near filler flow temp, angling into the bore a bit
    • I do them flat, just a skosh down slope in direction of desired flow
    • Fixture so you can flip it over easily without putting the torch down...
    • Once filler can start to flow I turn the flame down a bit (it's still sizeable, just not maximum), aim the flame generally into the cavity to encourage it in that direction
    • MOL half a rod per entire DO (half for for all of one DO/chainstay...maybe 1/3 for seat stay)
    • When meaningful amount of filler is inside I start heating the stay too, just far enough, and just enough to make room for more, still aiming flame largely into the bore....I sorta flame brush the filler down the tube while feeding a bit more filler into the end trying not to get it so hot the brass goes everywhere
      ...
    • I flux only the areas that are to get filler, plus a little "feed approach area" on the DO..."brass" likes to run everywhere; I no longer slather flux everywhere; I do apply and then finger wipe off flux down the stay for some inches, just as oxidation protection of the stay
    • I'd hate to use LP for this operation...needs the heat well focused, not everywhere; many use LP but it certainly wouldn't make my life easier for this operation!
    • Did I say to do some practice stays/DOs first? You'll be really, really glad you did.
    Thank you sir, for the detailed clarifications above, as well as those in other threads such as your numerous counterpoint to Doug Fattic's clarifications. They will ever be kept in mind with gratitude.

    I understand (in general terms) the importance of practice as you and Richard have mentioned and that, "it really is a 'feel', experience thing. ... it will take a while to get this figured out reasonably well."
    Even after certification for structural TIG welding, it took me at least 2 years of intensive practicing with thin walled steel and aluminum, making custom purging hardware/heatsinks(for steel), cutting up & etching to check penetration, photo logging all dialed settings, and making note of particular points of progress, to get the 'feel' of gettin' it done well.

    I have quite a bit of relatively cheap tubes and plates for use as DO-stay mock ups, and look forward to enjoying practicing A LOT to reach the point when I can say 'I got the feelin~ '...

    Cheers~
    Jihoon Jo

  6. #46
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    Default Re: Brazing Tab Type Dropouts

    I generally tack the tips of half moon then face fill onto the drop out to fill the chamber. You can practice my trying to close open small diameter tubes, and with that practice how deep you fill. You can fill say an 1/8" on one, and a half inch on another. This will also help you understand how much rod is going in and where it is going.

  7. #47
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    Default Re: Brazing Tab Type Dropouts

    Quote Originally Posted by Eric Estlund View Post
    I generally tack the tips of half moon then face fill onto the drop out to fill the chamber. You can practice my trying to close open small diameter tubes, and with that practice how deep you fill. You can fill say an 1/8" on one, and a half inch on another. This will also help you understand how much rod is going in and where it is going.
    Thank you Mr. Estlund.

    After reading your response, I reviewed the video I linked of Brian Chapman brazing the front DO, stopping the video along the way to catch the very brief shots of filler dabbing, and realized that the very first tack he makes (to the front slot of the DO) is actually from inside the chamber along the slot & DO. Capillary action draws the filler inside-out and all around the joint between slot & DO. THEN, he dabs the tip of the 'half moon' towards the backside of the DO, but has the rod vertical and NOT aiming inside the chamber - this I think is due to the camera being in the way as he mentions shortly afterwards.

    Also, I was able to catch a few very brief frames in which he points the flame (and the 'tongue tipped' rod) toward the chamber(as John mentioned). The frames are so brief it's not possible to make out how it looks when the chamber(cavity) is gradually filled up, but it's a good starting reference especially with clarifications in this thread.
    Jihoon Jo

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    Default Re: Brazing Tab Type Dropouts

    BTW, if anyone has or encounters a detailed video of 'Brazing Tab Type Dropouts' (other than the one by Chapman Cycles linked above), I'd love to see it! Thanks~
    Jihoon Jo

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    Default Re: Brazing Tab Type Dropouts


    Every minute detail helps greatly. Your flickr postings are a treat!
    I see why a stationary camera would inevitably get in the way during this process, as you physically move around to heat, inspect, and add filler.
    Perhaps a good way would be a forehead mounted GoPro/mini camera or similar to move with the brazer.

    As I clicked play/pause repeatedly for intensive frame by frame inspection of your technique, I accidentally stumbled upon your source or inspiration;
    https://www.flickr.com/photos/225387...n/photostream/
    Jihoon Jo

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    Default Re: Brazing Tab Type Dropouts

    Jihoon, it has got to be said even though it is totally in my self-interest to say it. The easiest, fastest and best way available today to learn how to braze, file and build a frame is by taking a class from an experienced builder/teacher. Iíll use as an example the middle aged Korean/American (he came to the States 20 years ago) that just finished my 3 week class. Before he came he had no idea whatsoever how a frame was put together. Absolutely none. He had never heard of brazing before. He left with a professional quality frame because he was determined to learn how to get good results. Of course I had to help on some hard parts but after an explanation, demonstration and practice on each joint type, he did almost everything himself. There was a LOT of repetition involved before he did it for real. Iíll show you some pics of the frame he made starting with the brazing and filing he did on tab dropouts. We took a couple of extra days after class to paint it red.

    IMG_3347 2.jpegIMG_3343 2.jpgIMG_3346 2.jpgIMG_3360 2.jpg

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    Default Re: Brazing Tab Type Dropouts

    That's some fine teachin' ...! If you were within driving distance, not overseas, and the corona bug dropped dead, I'd probably be knockin' your shop door by now... mm!
    Jihoon Jo

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