For a while, I've had a heck of a time getting the rear wheel to line up properly in the frame after the chainstays are attached to the main triangle. It's a bugger getting the dummy axle centered in the first place on the Nortac jig, and I've always had to cold-set the stays after they're brazed to the bottom bracket shell.
So when I was assembling the "chainstays" for my daughter's push-bike (see the Gallery page -- coming soon), I set it up in the jig with a custom dummy axle (the locknut dimension for the wheels is not a road bike standard), and as I rested the stays on the rear dummy axle on the jig, I noticed that they didn't line up right. I loosened the set screw on the jig, spun the dummy axle, and watched the end scribe a nice little circle.
The dummy axle is bent. Lovely. It doesn't take much at the axle to see a big misalignment at the rim and tire.
That explains a lot, like why I've always had to cold-set the chainstays after brazing, and why I've had to file the dropouts after completely assembling the frame.
I also was forced into a different procedure in getting the chainstays set up for Simeon's hard tail. The width of the sliding dropouts is more than the Nortac jig will allow. So I had to get a little creative with the dummy axle, C-clamps, V-blocks, and steel angle stock.
And that worked pretty well to get the chainstays fitted up. It'll work great attaching the dropouts to the chainstays. But then I'm in the same dilemma in attaching those assemblies to the already-built main triangle.
I'll manage, but it gets me thinking about a different build sequence that should work well, and solve all the issues with chainstay misalignment at the same time. And open up more options for dropouts.
Using the same "jig" that I used for Simeon's chainstay fit-up, I'll attach the dropouts to the stays, and then also attach the chainstays to the bottom bracket shell before it's made into the main triangle. I've seen this procedure before with other builders, mostly those who use spine-type frame jigs.
I'll have to accommodate the seat tube when fitting up the chainstays to the shell, but forcing the intersection towards the bottom of the shell should allow for plenty of clearance.
Learing... Adapting.
