Yesterday I got some time to weld the front triangle of TK’s mtn touring machine, after re-mitering the larger 38mm diameter downtube and brazing on the various braze-ons last week. I also mitered the chainstays to the BB, after first slotting them for the Paragon low-mount dropouts, and then dimpling the stays for more tire clearance. With the Sputnik chainstay mitering fixture, I need to dimple the Dedaccai S-bend chainstays to be able to fit them in the tube blocks i currently have. I’m loving the mitering fixture en sum, but I think my least favorite aspect of the fixture is that they the tube blocks are square and don’t cradle the tube as well as I’d like when the tube has a really oval profile, like these particular stays. The tube can wiggle in there and if you over-tighten the block you’ll leave some dimples on the chainstays (yes, I learn the hard way, eh!). You also need a separate tube block for every dimension of chainstay you plan on using which can get expensive at $100/set! But once you figure out this fixture, it sure is solid and does the job quite well.
The welds on the front triangle I’m really happy with. I’m getting more confident and cruising through faster than I used to. I think it used to take me something like 2-3 hours to weld the front triangle and now I can do it in half that. I still move the frame around a bunch (outside of the jig, after tacking it IN the frame jig) to get the best line-of-sight for each tube joint, but I’ve come up with a good process so that I know where I’m headed next and how to position everything just right. I only had to do a second pass on part of the two sides of one junction (the tight/acute angle between the DT and the ST at the BB). The miter had more wiggle room than I’d have liked so I put more filler rod in there and used the pulser to smooth out what was on 1st pass a lumpy weld. I understand why many builders use the pulser for every weld on the bike now – it makes pretty flawless looking welds and doesn’t overheat the tubes easily if you have the right settings. I’d be interested to know if there are any Titanium framebuilders out there that do NOT use the pulser?
Lots of mapping work to be done this week so not sure when I’ll get back to the shop to finish this bike, maybe next Sunday?