Days 7.0 and 8.0

The last two days have run together somewhat. We're pushing a pretty grueling pace to make sure that we're all finished by the end of the day on Friday, and the days seem overly short. Too much to do, and too little time to do it. (Or, perhaps, just the right amount to do, fast enough to do it in time.)

Also, there seems to be less to say. I wish that there were better words for describing what we do and how we do it, but we often observe Koichi and then simply follow in kind. The hands-on character of the work and the teacher's soft-spoken, less-is-more approach are integral to our experience but difficult to translate here. Four paragraphs describing filing a handful of steel tubes doesn't - won't - adequately convey the nature of the work itself. But perhaps thus is blogging.

There are really two projects going on simultaneously: the fork and the frame. So I will tackle the two separately.

The Fork

In the previous post, I left off with a picture of the cleaned fork crown and steer tube. From there, I began working on the fork blades. First things first, I cut off about a centimeter of the thin ends of the tubes, such that the two were as close to exactly the same length as possible. There's a small margin of error (0.0-1.0mm) , given for how the flared end sits in the fork crown, but exact is best. With the narrow ends filed flat, I reamed out the insides until the diameter fit the dropout plug. Once those fit, Koichi set up the fork blades in the fork crown and used a t-square to make sure that everything was, or would eventually be, aligned and proper.

   
Reamer (l) and top of a t-square (r).
With the t-square showing everything properly aligned, I could disassemble, sand, flux, and braze. First, though, I had to drill some vent holes beneath the location of the plug, since I'd be brazing a closed system. Then, because of the dropout style, I shoved a ring of bronze alloy into the fork blade above the top of the plug, so that the bronze could melt from within, flowing down and out the seam. It is a very neat little trick. Before brazing, I put the t-square back on to hold the fork blades level and the dropouts in alignment. Then, poof, brazed! Once the tips cooled, I soaked them in warm water to dissolve the flux and polished them up with a needle file and 100-grit sand paper. Then they looked pretty.


Aligned...


...brazed...


...and polished!
The next step on the fork was done today. I cut the flared ends to the appropriate length for my wheel and tire combination and fork rake, based on the blueprint. With the ends trimmed, I drilled new vent holes about 2.0cm from tip of where the inside of the fork crown would sit on the blades. Then, I prepped and fluxed the mess and Koichi set it up in the fork alignment jig, which holds the blades straight and sets the rake for brazing. Then came tacking and brazing, just like the crown and bottom bracket: heat the lug and tube, make a puddle, the puddle drips into the lug and disappears, repeat until pretty.


Not quite done.
It'll be done tomorrow!

The Frame

Last time, the front triangle was brazed. With all the flux dissolved from the bike's hot tub party, yesterday I could do some finishing. What does that mean, pray tell? It means taking a tiny little file, a steel brush, two feet of 100-grit sandpaper, and a mind blowing playlist and setting down to clean things up. The finishing is the work that makes the frame look pretty naked and painted. I cleaned up all the lug lines first with the steel brush, to make things look shiny; then, with the file to make things smooth; finally, with the sandpaper to make them shiny again. The most work is on the fillets, which should be really smooth and require a good deal of filing.


Got to make the bottom like the top.
The front triangle finishing work is the down-time activity. I can officially work on it whenever the jigs are occupied or I don't feel up to another arduous task. Lines can always be cleaner.

However, today I got to move on to prepping and tacking the rear triangle. The front triangle was first set in the jig, and a dummy rear wheel axle was set in place at the appropriate chain stay length. From that point, with my dropouts in place, Koichi could see how much of the thin end of the stays needed to be trimmed. After I sawed off the extra length, I had to miter the fat ends that would fit into the bottom bracket shell. Then the tiny ends were notched and beveled to make room for the rear dropouts and allow bronze to flow into the space.


Just like this.
In the jig, we could see that the notches were not quite deep enough, since the dropouts would not fit flush into the dummy axle. So the notches were extended until the whole set-up could fit snugly. With everything fitting, Koichi marked the tubes where I would need tire clearance and chain ring clearance, and used an arbor press to dimple the tubes. Then, much like the fork blades, the whole mess was disassembled, cleaned, fluxed, reassembled, fluxed again, and tacked. The forward ends were easy to tack, since the material densities were not too dissimilar - thin lug portion of the bottom bracket shell and thin tubing. The dropouts, however, are cold forged and very, very dense. On top of that, the tips of the chain stays are thin and pointy, and heat very easily. So it was a slow and delicate torch dance to get the heat right for brazing. And I didn't get it right. The ends are tacked, but they're kind of swimming in bronze. Maybe it's not that bad, and even if it is, that's just more finishing with which to entertain myself later!


This is with the seat stays, too.
After that was done, I could do the seat stays. First, the fat ends were notched and beveled for insertion over the dropouts. Once I did those, however, Koichi realized that they were too big for the profile of the dropouts, that they wouldn't work. So, we got new ones! Smaller diameter, thicker wall. He said, "Should feel the same." And it just might, but if anyone has any input I'd love to hear it.

With those ends set up, I could cut the seat lug ends long enough to extend over about a third of the seat binder. Once those ends were cut, Koichi set them up in a jig to be mitered, so that the ends would bump up around the underside of the binder. The fastback style has a very clean look to it, if I do say so myself.


Drool City
Population: 1
With the ends mitered and the fit snug on the frame jig, we could disassemble, clean, flux, reassemble, align, flux, and tack.


This is where I left off today.
It's cool, the whole thing is starting to look pretty bike-like. Tomorrow we finish all this brazing, and hopefully start and finish all the other braze-ons (bottle bosses, brake bosses, and cable guides for me).


That's all she wrote. Goodnight!