Bike tubes connected simply by welding (TIG welded):
http://tbn0.google.com/images?q=tbn:...954/680516.JPG
http://tbn0.google.com/images?q=tbn:...954/680202.JPG
http://tbn0.google.com/images?q=tbn:...taylor_tig.jpg
http://tbn0.google.com/images?q=tbn:...tig_welded.gif
Bikes tubes connected by inserting into steel LUGS at the joints and then brazed to seal:
http://images.google.com/imgres?imgu...3Doff%26sa%3DG
http://www.ciclisucarta.it/images/drawings.jpg
http://www.vendettacycles.com/vendet...es/gallery.htm