Wednesday, September 1, 2010

It's All Over But the Filing

Today was another long, hot day in the shop—but I completed all the actual brazing for my second frame, a track-like fixed gear I'm now thinking of as "Jocelyn Lovell Bike."

Toronto is suffering through a three-day late-August heat wave, and today felt to me like the hottest of them. I was planning on doing some lug filing, but I don't have the patience when it's this hot. And it didn't really have time, either. Mitering the seatstay bridge, brazing it in place, filling all my vent holes, and brazing in a pair of watter bottle bosses took almost all day. I just had a bit of time to work on the seatstay/dropout finishing.

The photo at right was taken after I brazed in the water bottle bosses. It looks like a frog with a fire in its belly. It also accurately describes what it was like to be in my small, non-air conditioned shop on a 33 degree day with a torch in my hand.

The first thing I did today was miter and locate the seatstay bridge. This is a reasonably tricky, since the two miters need to be in phase with one another, and the angle needs to be right. I scribed a line on the 5/16" tube to orient the miters to one another; and my smallest half-round file just happened to have a curve corresponding to the diameter of the 14mm stays. With a little bit of work, I had it right. Brazing went exceptionally well; the fillet is very small and clean. Unfortunately the stay came out very slightly crooked; but probably not by enough for anyone but me to notice. (The good news is that the wheel sits perfectly straight in the completed rear triangle.) Here's the bridge, after the flux came off (no cleanup):

In that picture you can see the second thing I worked on: filling vent holes. This is a very fun activity—you drill the vent holes so that they correspond to the diameter of brass rod, and then to fill them you stick the rod in and silver-braze it in place. It's a fun challenge to see if you can braze the rod in without bending it excessively (it weakens as it heats up.) It's a good exercise in heat control.

This one, as you can see, bent a lot! This is a fat 3/32" rod, and it was very long and heavy. (I like this picture!)

Next up were the water bottle bosses. I only decided to put these in at the last moment. I wanted to keep things as "clean" as possible on this bike—but then I thought it was a bit stupid to deliberately limit my options distance-wise by not putting on bosses. I decided to use star reinforcers for these bosses—and let me tell you, it's a massive pain enlarging the holes in them to accept the bosses. They're tiny and thin and extremely hard to hold in a vise. (I ended up using rubber soft jaws, which worked acceptably.) My brazing was again pretty perfect—I'm having a good run!

It will take a day or two to get everything perfectly filed (I'll try not to go too nuts.) Then comes the all-important matter of finalizing the colour scheme!


OAP said...

Oh I had a similar "chimney effect" after a brazed something. I even took a movie!

Nicely done, and great pictures. Are you going to build the frame up before paint? That's going to be one FAST bike.

AH said...

Hehe, we'll I'll try to make it go fast!

Yes I'll build it up! I think I have everything except for the front cable stop. I'm still a bit tempted to make a stem... if I do I'll need your help!