Friday, November 25, 2011

Dropout

One of those things I would love to learn how to do is to build bike frames.  Specifically, I want to braze frames together, either with lugs or fillet-brazed.  So far, I have only managed to do very basic brazing.  My torch is a cheap "hobby-level" model, and I really haven't taken the time or spent the money to deal with major projects.

The first brazing job I did was on my first Formula One frame.  I cut out the tig-welded vertical dropouts and replaced them with track ends, because I wanted a fixed-gear 20"-wheeled bike.  I struggled with that conversion, and actually ended up burning a hole in the tube on the drive-side chainstay.

One problem I was having was that I was using nickle-copper brazing rod, which requires a higher heat than brass.  I didn't now that, when I bought the brazing rod, and only found out after I was having the problem with overheating the tubes. 

Nickle-copper brazing rod is made of the same alloy that U.S. 5-Cent pieces are made of (that's why we commonly refer to the 5-Cent piece as a "nickle").  So, to repair the hole I had left in the chainstay, I took a "nickle" coin and brazed it into place, then ground everything down smooth.

That frame modification held up fine for the whole time I owned that bike, and I never heard any complaints from the guy I sold it to.  About a year after I had done that work, I read somewhere that using a 5-Cent coin to patch nickle-copper brazed joints was an old trick that a lot of hot-rod builders had used, back in the day.

Since then, I have found a good source for 1/16" brass brazing rod, and that has simplified things.  I have replaced a couple of broken rear dropouts on bikes, with no problem.  But, I still need to work on my technique before I trust myself to buld a whole frame.

x

2 comments:

  1. Wow, what a well timed post. This week I've been thinking about getting a professional to add rear canti studs and a few cable stops to my rockfish. I just got mine rideable this week. Sachs 3x7 hub with a 53 ring in the front!

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  2. I had one of those 3x7 hubs on a BikeFriday (custom-buit for my ex-wife). It was pretty cool.

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