Friday, April 15, 2005

Looking Inside the Joint

I tried using a smaller flame on my upper lug. Not as much silver slipped down the tubes this time, and the flux didn't get burned. But, it actually seemed to be harder to work the filler around. I did limit myself to inserting filler in only 4 places. So, all in all, it feels like I've made some progress. I am, however, going to try a flame midway between what was used on the 1st and 2nd joint.

After cleaning things up, it was time to start cutting. For the most part, I was satisfied with what I found. One of the tubes apparently shifted in its lug prior to brazing. This resulted in a bit of gap between the two tubes, even though the miter had been carefully fit. The lugs are of the pressed variety and therefore leave a bigger gap around the miter. For the most part this filled better than anticipated.

The couple of spots where there appeared to be a gap on the shoreline didn't reflect gaps on the inside. Yipee!!!

On the downtube, I borrowed from the method Fred Parr recommends for filleted joints. That is to put in a circle of brazing material prior to brazing the joints. Sure enough it melted and made a nice little fillet around the inside of the joint. It may be overkill, but if I can get better at forming this ring, I'll use it on all the frames I do.

The bottom line is that I'm mostly satisfied with the joints. Once I start pinning them, I don't think I'll have the problem of tubes shifting. Other than that, the fill of brazing material looked adequate to make a strong joint. A couple of more lugs will tell me a lot, but I think its time to focus more how to be economical with the filler (and simplify my cleanup).

Stay Tuned.

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