I’m slowly getting this frame finished. This wishbone seat stay in the photos is my second try. The first try, I cut the mainstay miter too close on the bottom and burned through the tube at the edge. This time, I cut the mainstay long, welded it to the crown pieces, then used the mill to cut the flat end off and leave that coped end. I think it looks better that way and something new to try. But doing things twice totally irks me…it’s ‘practice’, but I’m only spending a couple hours every other day in the shop right now so time is of the essence.
The welds for this wishbone stay are easy and hard at the same time. The mainstay and crown pieces are regular ole 4130 and 0.9mm wall thickness (thickest you’ll see on a steel cross-country style bike except for the head tube and top of the seat tube). The main seat stays that come down from the crown are 16mm diameter tapering to around 12.4mm and are 0.66mm wall thickness or thereabouts (some of the thinnest you’ll see on a bike except for the middle butted portions of the main tubes which can go down to 0.5mm). The small diameter seat stay tubes and smaller TIG welds are just different than the other welds on the frame. Maybe I just don’t practice them enough but they are harder for me to get done cleanly. So when I had the crown pieces welded really nicely to the mainstay, I was psyched.
Fixturing this type of seat stay up is somewhat of a pain. I really need to develop my own fixture for this if I’m going to make this my ‘regular’. I am considering stopping this type of stay since it’s just a lot of cutting, mitering, welding, fixturing when compared to the normal fastback seat stays. I think they’re heavier than normal bend fastback stays too. Wishbones are thought to be an easier form of seatstay fabrication, but I really don’t think so.
So now that it’s all mitered, I’ll add the silver brazed-on caps to the crown, soak, clean and dry. Then tack the mainstay to the seat tube, tack the dropouts to the stays, and then braze and weld it all up. It’s getting pretty close!