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Framebuilders Thinking about a custom frame? Lugged vs Fillet Brazed. Different Frame materials? Newvex or Pacenti Lugs? why get a custom Road, Mountain, or Track Frame? Got a question about framebuilding? Lets discuss framebuilding at it's finest.

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Old 01-22-12, 02:26 PM   #1
troysmith80
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Quick question about brazed dropouts

I've got an old (80's probably) Schwinn Probe that i got a few years ago, it had been used as an early mt bike. I'm converting it to a commuter and I'm building a nice rear rack that i'm going to braze to the frame. The bike is a steel-lug constructed frame.

My question is, if i braze a rack support along the seat stay, right close to the dropout, i'm probably going to melt the dropout joint, aren't I?

Is that a big problem? Is there a way to avoid that? I don't want to move my rack support too far up the seat stay, away from the dropout, because then a heavy load on the rack would be trying to fold my seat stay in half.

Is it possible that the brass in the dropout joint would melt but not really move around much, and not cause a problem?

I'm pretty sure i'm really going to want to avoid melting the brass in the original joint, but i don't know how i can do that. (I'm a beginner brazer if that isn't obvious)
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Old 01-22-12, 02:34 PM   #2
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Brazing, while simple top do, required some practice and materials. You can add more bronze close by an existing joint with a little care not to reheat the original joint.

Frame builders add bit's to frames in many cases and there is tons of then in your area.
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Old 01-22-12, 03:00 PM   #3
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Thanks for the response. I'm pretty sure i won't be able to make this joint the way i want to without reheating the dropout joint. A little modification to my plan (for a smaller joint that will require less heating) may make this possible though.

I guess maybe i better go back to the drawing board.
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Old 01-22-12, 03:05 PM   #4
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I have brazed a rack lug onto the stay right on top of the dropout joint. You aren't going to re-melt the existing brazing filler to any significant degree unless you use way too much heat. Even if it does melt, it will just re-solidify in place, no harm-no foul.

I don't really like the idea of building a rack into a frame, especially if you don't have a lot of experience.
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Old 01-22-12, 03:18 PM   #5
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Quote:
Originally Posted by unterhausen View Post
I don't really like the idea of building a rack into a frame, especially if you don't have a lot of experience.
Why is that? I'm doing this as sort of a practice exercise, teaching myself to fabricate and braze.
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Old 01-22-12, 07:12 PM   #6
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My preference for practice is brazing scraps together until you feel comfortable with brazing. Then I would suggest you make a rack as practice. Plenty of people have done that. I submit it's probably better practice than building it in because it's harder to fake and you aren't stuck with it.
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Old 01-22-12, 08:11 PM   #7
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I also think the dropout joint is pretty safe for what you want to do.
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Old 01-22-12, 08:46 PM   #8
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I have been practicing on plenty of scraps. This bike is the next step. I just came in from practicing on some more scrap (same tube as i'm using for the rack). I'm working on building up fillets.

I think i was a little too worried about melting that joint, it's not THAT hard to control the heat enough to keep from melting those. The practice just now gave me a better idea of how it's going to work out.

I'm moving ahead. I appreciate the input. I'll post pictures later. Might not get all the pieces shaped tonight though.
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Old 01-31-12, 03:25 PM   #9
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In case anybody is following this in the future, the process was continued here: http://www.bikeforums.net/showthread...offer-feedback

I ended up brazing pretty close to the dropouts, and probably due to my inexperience, overheated the seatstays also. Despite that, there doesn't appear to be any problems with the dropouts. On the left side it looks like maybe the brass reflowed a little, but i don't think anything moved. Or it may not have even flowed, i should have paid closer attention to how it looked before i heated it! Anyway, no catastrophes and i think no problems at all.
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Old 01-31-12, 03:54 PM   #10
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you aren't brazing close enough to the dropouts to reflow the brass. If you ever try to take out a dropout you will find out how unlikely this is to happen. The dropout has to be very hot in order to move. Even then it will take a little persuasion. As I said, you could have brazed right on the dropout joint and never affected it at all.
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