Silver Case

While I was away on vacation, the atmosphere was busy on Le Chacal, building up a deep mahogany patina of surface rust. I returned to the workshop a bit flat footed today, so it was an easy segue to start with cleaning up the the interfaces I’d be brazing.

rusting away

The job today was to braze the top tube to the head tube and to the seat tube. I had finished the miters last week.

Braszing top tube to seat tube

Before plenty of filing, scraping, and sanding

Brazing was only barely ok. Honestly, it didn’t meet my minimum expectations for myself.

1) The idea of the seattube reinforcement sleeve was to draw a capillary flow of bronze from the top of the sleeve until it dribbled out the bottom. Seems the tube was too tight, which prevented capillary action. Thus I never really got the gooey, flowing goodness of a thorough bronze sandwich.

2) For the first time I overheated a piece. Of course it was one another guy was watching and was just about to say, “your brazing skills are becoming quite comfortable”. It got too hot, too bright, and then it cooked off all the flux, leaving black obsidian everywhere and became impossible to braze over.

3) Sulaiman saved me from something stupid. I needed some flux on the piece. Instead of just dipping the brass brazing rod into the dry flux powder, I had the momentarily brilliant idea (I needed a lot of flux) of spooning on some of the wet flux paste I had pre-treated the joint with. As Sulaiman pointed out, applying wet paste to a 500C piece of metal is a bit dumb.

Nearly became a plow; but it fits.

Anyway, I managed to finish the job. And by only luck, despite me fucking up installing the top tube (it was 4mm off due to my bad measurement), the head tube relation to the spindle relation to the down tube is pretty much bang on. Whew. Close call. I always hate the first failure after a round of initial success. It always happens in order to humble me, and it always succeeds.

Tomorrow is the beginning of bespoke, tricky business. In technical jargon, I’m building a system of collapsible unicrown chain- and seat-stays. It’s a unique design for a bike and will be an ongoing engineering challenge. We’re not settled or decided on how the dropouts will connect and hinge to the seat stays.

Seatstays