To be clear, a lot of what I write during this class is basically notes for my future reference.
I had my first measurement mishap today. Luckily it was only in the drawing rather than the frame. I’d drawn in the tire centered over the diameter of the tire rather than the radius. This threw off the position of the chain stay dimples. But like I said, it was only in the drawing. The actual position of the dimples were marked with the actual wheel mounted to the free hanging chain stays.
Although I noticed the problem, I didn’t figure out the cause. Joseph did, and that allowed me to continue with brazing them in place. It went, meh, okay. The fit was rather rough at the bottom bracket. The ports are straight but the chain stays are tapered, so every time I inserted the tubes, the points on the bracket points would spread apart again. Long story short, it caused some large gaps that needed to be pinched while hot (a good two-person job) and a truck load of silver to fill. Next time I’ll take more off the drop out end so the bracket end will be less into the tapered section when I trim.
Most of us also had time to align the stays. I must’ve had some good karma because it was nearly perfect. The drive side dropout was a millimeter low and the bracket spacing was 127 mm instead of 130 mm. Both were quickly fixed.
Next was the seat stays, which have been cut, test fitted, and I’ve prepared the points. I’ll be using a traditional points, spooned, and they’re ready to braze when I get in tomorrow. A lot of today was demos so I didn’t have the time to finish them. Also a contributing factor was I wanted a long scallop here, so that meant more time to file and book-match them.
I wasn’t able to use my first choice of seat stays because the end diameter of the .7 mm tubes was too small to fit the plug-in style rear drop outs. That would mean I’d have to cut off a good portion of the small end of these tapered tubes, and that would make them too short to reach the seat tube lug. So I’m using .8 mm. It’ll have a stiff rear triangle. Jan Heine seems to prefer this design but I have not enough personal experience for an opinion.
Regardless, the entire bike is now .8 walled tubes, butted to .5 on the main triangle, except for the seat tube, which is .9/.6 as that is the only diameter we had available.
Besides the seat stays tomorrow, we start adding the brake posts and bridges. As a special bonus, we’ll have the honor of visiting Joseph’s own shop after class. I’m looking forward to that. Not so great is that Ron, the owner and UBI’s chief engineer is heading back to Ashland tonight for the remainder. I’m going to missing his encyclopedic knowledge and technical input. On the bright side, maybe the biggest need for that is gone as there isn’t any more structural work to be done and the jigs have been put away.
Here’s where it stands:
Did I mention it was hot? Today was the hottest day of the year, I believe. Like most shops I’ve been in, it gets hot inside, especially when working. I thoroughly enjoyed the ride home though, despite the heat.