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  1. #1
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    brazing dropouts

    i've had some practice with silver brazing lugs on scraps, and am almost ready to attempt my first lugged (road) bike. is there any informational video or literature i can find online regarding technique for brazing flat dropouts? unfortunately i dont really have anything to practice on, so my first frame attempt will be the practice. i'm feeling a lot less confident about the dropout than i am about the lugged joints, and i'd like to bone up as much as possible before putting torch to metal.

    the best i've found so far is this brief video. how would you know if you've gotten enough filler material between the inner tube wall and the wing on the dropout? is it safe to assume it needs to be filled at least the entire length of the wing on the dropout?

    i've been racking my brain, wondering how something this gorgeous could be accomplished:


  2. #2
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    Couple random thoughts

    1: Use brass for the dropouts if it's your first frame. You will have a much easier time making a joint that won't fall apart.

    2: Any piece of plate and any small-ish piece of tube is enough to practice on. Get some scrap and practice! No amount of video-watching will give you the heat control/muscle memory/etc you need. Practice practice practice.

    3: That picture is of a joint that has been extensively finished (ie filed, sanded, flux soaked off, etc). That's not what the joint will look like right after brazing even if you do it perfectly.

    -Walt
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  3. #3
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    thanks very much for the advice.

    Quote Originally Posted by Walt View Post
    1: Use brass for the dropouts if it's your first frame. You will have a much easier time making a joint that won't fall apart.
    would it be smart to also use brass in other non-socketed spots like on the upper seatstays, and on the seatstay yoke? i've been able to do an ok job with the silver rod on these kinds of things when practicing, but would love to hear what you think about this. as a total beginner, a more forgiving process couldn't hurt.

    Quote Originally Posted by Walt View Post
    3: That picture is of a joint that has been extensively finished (ie filed, sanded, flux soaked off, etc). That's not what the joint will look like right after brazing even if you do it perfectly.

    -Walt
    so this is simply the same brazing process i've seen elsewhere, slightly overfilled and then brought down to that shape?


    could you also comment on how one would control how much filler material goes into each joint? i imagine this is of critical importance to the strength of the dropout?

  4. #4
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    Quote Originally Posted by s4gobabygo View Post

    so this is simply the same brazing process i've seen elsewhere, slightly overfilled and then brought down to that shape?


    could you also comment on how one would control how much filler material goes into each joint? i imagine this is of critical importance to the strength of the dropout?
    I usually end up putting little less than half a rod of brass in each joint on the dropouts. It's just like brazing anything else. Heat it up, push in your filler and use the heat to draw the filler into the stay and to fill the joint.

    Like Walt said, if you're unsure practice. Get some 1/4" plate and tubing, slot the tubes just like you would a stay and go at it.

    Practice is definitely good.

    Good luck,
    Adam

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    Quote Originally Posted by adarn View Post
    I usually end up putting little less than half a rod of brass in each joint on the dropouts. It's just like brazing anything else. Heat it up, push in your filler and use the heat to draw the filler into the stay and to fill the joint.

    Like Walt said, if you're unsure practice. Get some 1/4" plate and tubing, slot the tubes just like you would a stay and go at it.

    Practice is definitely good.

    Good luck,
    Adam
    I have seen builders use finishing nails as solid filler to reduce the amount of brass needed.
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  6. #6
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    Quote Originally Posted by adarn View Post
    I usually end up putting little less than half a rod of brass in each joint on the dropouts. It's just like brazing anything else. Heat it up, push in your filler and use the heat to draw the filler into the stay and to fill the joint.
    Good luck,
    Adam
    thanks. when you say "each joint" do you mean you would use up to half rod per side of the slot in each connection (meaning up to 4 rods total for the dropouts including both chainstays and both seatstays)?

  7. #7
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    Quote Originally Posted by shiggy View Post
    I have seen builders use finishing nails as solid filler to reduce the amount of brass needed.
    I have seen that too. I ended up doing that on my second frame actually because I was trying to use 56 silver to put in some stainless DO's. I'm not sure how "legit" it is, but they're still attached to the frame after being beaten to hell.


    Quote Originally Posted by s4gobabygo View Post
    thanks. when you say "each joint" do you mean you would use up to half rod per side of the slot in each connection (meaning up to 4 rods total for the dropouts including both chainstays and both seatstays)?
    By each joint I mean chain stay to drop out or seat stay to dropout. So about 2 rods or so total.

    It sounds to me like some practice would be really helpful for ya. It sucks having to throw away a whole frame and it's also really expensive. A couple of joints and you should at least get the idea enough to give it a shot on a frame. Plus you can cut up the practice ones and see how you did.

  8. #8
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    thanks for all the input, everyone! i'll order some more stay-sized tubing to practice on before i step it up to the actual project.

    i wouldn't mind trying (in practice) the solid filler method to conserve the amount of material i use. is it important that the solid filler not contact either surface (inner tube wall or dropout) so that the joint contacts the same amount of total surface area with the tube and dropout? if so, how would one accomplish this?

    also, do you guys think it would be smarter for me to use the brass rod in other spots that require a bit of a joint, like the top of the seatstays (which will be brazed to the outside of the seat tube lug), and the stay/yoke connections? when i'm working with the practice lugs (and silver rod), i find it relatively easy, because i can simply draw the filler material from one side of the lug to the other, and it's pretty clear when i'm done. in the spots that aren't lugged, i have a little trouble "containing" my joint. it seems to want to run away from me. hopefully the brass will be a little more forgiving to my ham-handedness. maybe using a solid filler will also make this a little easier, as there will be more surface area and less volume of (molten) filler needed.

  9. #9
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    Brass is cheap and will easily fill the space. I wouldn't really bother with the solid filler.

    I've never built a frame with silver, or successfully built a lugged frame, but I know that lots of builders use silver to join seat stays. There are a couple of different ways.

    You can miter the stays to the lug, or you can do the "fast back" way, where the stays are joined to the seat post binder, you can cap them and wrap the caps around the front of the lug. Look around at pictures of some frames to get some ideas.

  10. #10
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    Quote Originally Posted by s4gobabygo View Post
    thanks for all the input, everyone! i'll order some more stay-sized tubing to practice on before i step it up to the actual project.

    i wouldn't mind trying (in practice) the solid filler method to conserve the amount of material i use. is it important that the solid filler not contact either surface (inner tube wall or dropout) so that the joint contacts the same amount of total surface area with the tube and dropout? if so, how would one accomplish this?

    also, do you guys think it would be smarter for me to use the brass rod in other spots that require a bit of a joint, like the top of the seatstays (which will be brazed to the outside of the seat tube lug), and the stay/yoke connections? when i'm working with the practice lugs (and silver rod), i find it relatively easy, because i can simply draw the filler material from one side of the lug to the other, and it's pretty clear when i'm done. in the spots that aren't lugged, i have a little trouble "containing" my joint. it seems to want to run away from me. hopefully the brass will be a little more forgiving to my ham-handedness. maybe using a solid filler will also make this a little easier, as there will be more surface area and less volume of (molten) filler needed.
    The filler material (nails) can contact both the tube and dropout. Done right, the rod flows around and fills everything.

    Anytime you have a gap/void brass is much easier to use and get a good joint. Silver is VERY liquid while brass has more body.

    Neither works well if you do not practice--a lot. I did small braze ones and sample tube joins every day for ~6 months before I attempted my first frame.
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  11. #11
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    Quote Originally Posted by adarn View Post
    Brass is cheap and will easily fill the space. I wouldn't really bother with the solid filler.

    I've never built a frame with silver, or successfully built a lugged frame, but I know that lots of builders use silver to join seat stays. There are a couple of different ways.

    You can miter the stays to the lug, or you can do the "fast back" way, where the stays are joined to the seat post binder, you can cap them and wrap the caps around the front of the lug. Look around at pictures of some frames to get some ideas.
    thanks. maybe i'll stick with the silver then for everything but the dropouts. my plan is to miter the stays to the seat tube lug, and my analog practicing has turned out fine with this method i think. i prefer the look of the capped stays, but this seems to me like it might be a little more complex, so i might leave this for a later frame.

    in case anyone is wondering, this will be a very simplistic single speed road bike with a 700x28 tire. my parents are retiring, and bought a small vineyard in southern sicily for their retirement. the plan is for the bike to be a retirement gift to my father to use to spin around the vineyard and surrounding areas. if it turns out worth a damn, i'm going to ask my great uncle, a sicilian artist, to paint the frame however he wishes. i'd like to give it to my father in the summer, so i still have some time for a few botched attempts first.

  12. #12
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    What others have said on the dropouts. I recall a post by Richard Sachs on the old framebuilders list where he said something to the effect of "fill 'er up" (may or may not be a direct quote).

    Given that you're a newb, I would use brass to attach your seatstays -- a lot more room for error with that joint. Melting out the silver on the seat lug *could* be an issue (I've never done this myself), but I don't know how much you need to worry about that.

  13. #13
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    Quote Originally Posted by adarn View Post
    Brass is cheap and will easily fill the space. I wouldn't really bother with the solid filler.
    Right, but he did say stainless drops which means brass won't work.

  14. #14
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    Quote Originally Posted by s4gobabygo View Post
    thanks for all the input, everyone! i'll order some more stay-sized tubing to practice on before i step it up to the actual project.
    I'm sure I have a bunch of drops in the scrap bin, if you want to pay for shipping PM your address to me and I'll get them out to you.

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    Quote Originally Posted by jay_ntwr View Post
    Right, but he did say stainless drops which means brass won't work.
    to clarify, the lugs are stainless, but the dropouts are mild steel. this is why i've been practicing with silver. given that the dropouts aren't stainless, it's sounding like brass filler is the easy answer there. i'd consider buying a mild steel seat tube lug to use brass at the top of the seat stays if i have a significantly easier time working with the brass filler rod. to be honest, i've only worked with the silver filler rod so far, and don't yet have any brass rod to play around with. i've probably done myself a disservice not starting with brass then moving up to silver as my technique develops.

    Quote Originally Posted by RCP FAB View Post
    I'm sure I have a bunch of drops in the scrap bin, if you want to pay for shipping PM your address to me and I'll get them out to you.
    thank you very much for the generous offer. you'll have a PM in a minute.

  16. #16
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    For your practice, you can just buy some 5/8" 0.035 tubing someplace local to stick onto dropouts (or flat plate steel). No need to buy expensive chainstay type stuff.

  17. #17
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    Quote Originally Posted by Francis Buxton View Post
    For your practice, you can just buy some 5/8" 0.035 tubing someplace local to stick onto dropouts (or flat plate steel). No need to buy expensive chainstay type stuff.
    thanks. rcp fab was kind enough to throw together some scrap for me to work with. i'm working in an auto racing shop at the moment, so there's a lot of scrap, but it's all massive stuff for making roll cages.

  18. #18
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    perhaps i should have mentioned this sooner, but i've been working with a mapp gas torch while practicing. it seems good for my ability level when i've been working with the silver rod, because it allows me to work pretty slowly and deliberately. a higher temperature would probably be a lot harder for me to manage currently. i see that the melting point of brass is marginally higher than that of silver. is it safe to assume the mapp gas torch will also be sufficient for the brass filler? there's a wide array of torches with various gasses and fittings available at the shop, but i was immediately attracted to the convenience of the mapp gas torch.

  19. #19
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    stainless lugs
    +
    mapp
    +
    first frame

    I would reconsider this approach

  20. #20
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    Just to add, but not confuse as a learning exercise, I used to use a half round plug rather than a nail to fill the gap between tube and drop-out as silver likes tight clearances. I would make them out of any steel that was close to hand. Filed off after silvering if you want the nice finish in your picture.

    Eric
    If I don't make an attempt, how will I know if it will work?

  21. #21
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    Quote Originally Posted by unterhausen View Post
    stainless lugs
    +
    mapp
    +
    first frame

    I would reconsider this approach
    i previously bought a bunch of discount stainless head tube lugs and a single tube, which i've been using to practice my lugs. i have a wide variety of other torches and gasses available in the shop. can you please elaborate on the troubles you suspect i'll face? i still have more practice lugs to play with, so i could work with another torch if you think this would be smart... i'd just have to put in some more practice time. i have zero previous experience, but the guys in the shop have been supervising, and despite not knowing the first thing about a bicycle, they at least have a good handle on any safety concerns. mapp was the least intimidating of the available torches, and it seemed to work, but i'm always open to learning more tools/techniques. i have time to work on my technique before my first attempt. i only need the frame finished for the late spring.

  22. #22
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    Some observations from recent experience. I do both OA and MAPP with silver. MAPP is convenient for me to use in my unique situation where I do my work, and have adapted to it.

    Generally, MAPP with silver, the wider flame is good for fillet as it heats a wider area. It will allow for a slower heat build up that you can control well by flicking the flame off the silver at melt point and the silver will remain without dropping onto the floor.

    Re: silver. I use 45% silver for fillet rather than 56%. 56 is good on lugs, 45 fillets better.

    OA is much better for lugs as you draw the silver flowing in the joint around with its hotter smaller flame.

    Hope that helps.

    Eric
    Last edited by Eric Malcolm; 12-06-2012 at 02:40 PM.
    If I don't make an attempt, how will I know if it will work?

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