Today was the beginning of the real work I think.
Two of us are still short parts, I don’t have lugs and a fork crown. Another class member Clifford does not have a bottom bracket and some other stuff. Hopefully my stuff arrives tomorrow, it has been shipped from England last week. Clifford’s appears to have been lost and I don’t think there is much hope of it returning.
Today we did a number of things. The first thing we did this morning was miter the seat tube into the bottom bracket. This was done on Doug’s Bridgeport, which may be the coolest machine on the planet (big, lots of knobs, and I know what some of them do). If you’ve never seen a Bridgeport it looks kind of like a drill press, but bigger and can do more stuff. The table slides around. Google vertical milling machine and you should come up with something.
Bridgeport in action
The miter for the seat tube is pretty straight forward, no jigging was required and only minor filing to bring the miter into reasonable shape. The next task was to miter the junction of the seat tube and down tube. This happens inside the bottom bracket shell, but it needs to be cleaned up to allow for full insertion of the down tube.
We did the seat tube to down tube miter by hand with only a file. It was a good introduction to filing, Doug makes it look stupid easy. It then took me about half an hour to do what he did in about five minutes. After I got the miter squared away I started to clean up the bottom bracket shell. This meant making the edges crisp and perpendicular the the shell and smoothing out some of the points. This is where Doug really started to teach us filing technique and how to properly do the job. I’m struggling with the technique, but I think after tomorrow I should have it down. Making the bottom bracket shell look good is an entirely different matter. First off you need to carve out good looking points, and the slope on each side of the point should be symmetrical, and not too steep, or the points look goofy. I spent the better part of the afternoon on the down tube and seat tube sockets on the bottom bracket. At this point they look okay. I started working on the chain stay sockets but lost the will to continue at about 10:00 PM or so.
The other big task of the day was mitering the top tube. First off we had to situate the tube so the proper amount of butting was connecting to the head tube (this is a big contributer to stiffness) and seat tubes. After using a hack saw to get the proper length I did the front miter (top tube to head tube). There’s a pretty simple formula to get the proper angle and then we just put the tube in a jig on the Bridgeport at that angle. There is then some magic that I don’t quite understand to figuring out the angle of the seat tube top tube miter. It seems trivial and I did a practice miter while Doug wasn’t in the shop tonight. It came out “almost” right so I’m not sure if it is an issue that I just file out or if the three of us didn’t quire remember the correct way to calculate the angle (edit: turns out we were just making it too hard, really was easy).
Tomorrow I’ll take another stab at making the bottom bracket look okay, as well as making sure we got the correct miter on the seat tube head tube joint. It’s also the first day of brazing so I anticipate this will be a difficult day. Hopefully learning to braze comes a little quicker than learning to file. Typically I learn things a little bit slower than most, so we will see.
So far Doug has been an outstanding teacher. His sense of humor is a great fit for the three of us taking the class and I’m having a wonderful time. I’ve not decided if frame building is for me (i.e. will I ever build another one), but if nothing else I’m having fun on my vacation and should end up with a pretty cool bike.
I mentioned that I don’t have my fork crown yet. Doug came up with an idea this afternoon that would let me use a crown built for a one inch steerer mated to a one and one eight inch steerer. This allows me to use a much cooler crown and I’m excited to see if we can pull it off. I’d also really like for my original crown and bottom bracket to show up, but if that doesn’t happen at least we seem to have a backup plan (that I like a lot more than plan A).
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