your post is not particularly descriptive, and I couldn't find any pictures of their bikes with construction that looks anything like what you are describing. However, the seat cluster usually needs to be reinforced on a tig welded bicycle.
I have seen some construction where it looked as though they maybe had some parts left over, or some production reason for having some of both. A lot of bikes will end up using, TIG, silver and brass all in one.
there was a thread in C&V and possibly in here with a bike that had a seat lug, a socketed bb shell, and was fillet brazed or tig at the head tube. I spent a few minutes looking for it without success. I think it looks horrible, but my thought is they used the seat lug to reinforce the seat tube, and I refuse to speculate on the reason for the socketed bb shell.
I wouldnt call it common, but I have seen all kinds of different combinations. If you mean just the seat lug is reinforced, and the dropouts are socket type, thats not all that rare. However, there all kinds of reasons for mixing things up. Often, depending on the geometry, lugs at every point arent feasible without a lot of shaping and filing and hammering. I have even seen a bb with chainstay sockets, and otherwise round for tig or filet.
that was a pretty nice solution to the problem of stainless lugs intersecting with seat tubes. They must have done the welding before brazing the lug because silver interacts badly with Tig. We still haven't seen any pictures from the OP, but I'm guessing that bike isn't quite as nice.
that was a pretty nice solution to the problem of stainless lugs intersecting with seat tubes. They must have done the welding before brazing the lug because silver interacts badly with Tig.
Thanks. The welding was done before brazing as you suggest. The framebuilder, Dave Wages, explains:
"...I fully set up the bike in the fixture and mitered the seat stays to fit against the seat lug. One of the welders then tacked the stays carefully onto the seat lug. After they cooled down, I took the unbrazed tubes out of the fixture, the stays still tacked to the seat lug and Sean, the welder, finished fully welding them to the lug. I then ground all the excess weld that had penetrated the lug, finished the welds, and then prepped the lug for brazing. Back to the fixture and everything gets reset, fluxed and tacked. I brazed the frame, did all the finishing, alignment and then it's off to the polisher for the final buff. So, to answer your question, the stays are TIG welded to the lug, but then all the other parts are silver brazed on your frame. If we had silver brazed the stays onto the lug, what ends up happening is the silver gets undercut during the polishing process and then it can discolor over time. Really not a nice look, and possibly not as strong either."