Update to this
previous build: remember how I said standover height was a bit of a problem? Well 6 months on and it still was. So I dropped the TT. It's a new tube (another Reynolds 631), and then I put a little gusset tube in because of the huge cantilever from the handlebar. Probably not necessary. Also considered cutting the HT much shorter and using lots of spacers. But that (a) looks goofy and (b) doesn't ultimately reduce the load on that TT/HT junction anyway.
The gusset tube is the end of a stay, probably a seatstay, that I had in my offcuts box. It'll be Reynolds 525 or some kind of cromoly. I just TIG brazed it on which I like to do for anything joining to something relatively thin-walled. All the main welds on a TIG frame are either onto the HT (which is thick), the BB (which is even thicker) or the top of an externally butted ST (also quite thick). I use braze for bridge tubes. This isn't necessary, lots of people weld them, it's just how I like to do it.
My new jig came in very handy here since it actually holds the frame properly solid. So I put the frame into the jig, got it all bolted down, and then cut out the old TT and fitted up the new one, without anything moving in between.
What's interesting is how now that the bike is built up again it actually looks more normal (at least to me). The main triangle is now a more familiar shape and you don't especially notice the gusset tube or very long HT.
I think this is quite a nice way to make this kind of high-stack frame (if you don't have the technology to curve the TT, and that would also entail using a plain-gauge cromoly tube rather than a double butted one as I have here).
