Tuesday, April 28, 2009

My Frame So Far: Photos from UBI Chromoly Brazing Class

Fork before assembly. Fork will be threadless, 1.125 inch, with flat crown, oval legs, and 40mm rake (which we achieve by bending straight blades). Not a traditional track fork, but close enough.

Fork in jig, after brazing, front view. Tips are brazed with brass; legs and steering tube are brazed with silver.

Fork in jig, after brazing, side view

Fork out of jig, after brazing, before finishing. Fork tip brazing is sloppy, so will require a lot of filing.

Head tube and top tube in Henry James jig, after brazing. Head tube angle is 74 degrees, but the frame will have a sloping top tube, so the actual angle between head tube and top tube is closer to 79 degrees. The lug set is called "slant six". Top tube is oversized: 31.8 mm.

Brazed front triangle, in Henry James jig. Note the head tube-top tube joint is fluxed -- prepared for re-heating to remedy a gap in the braze. Seat tube is 31.8 mm, and down tube is 36mm. So, this is a very oversized tubeset. All main triangle tubes are butted. I had originally gotten the miter angle on the downtube wrong, and I could not salvage that tube, so this is my second downtube. All miters (except the seat tube at the bottom bracket) were done by machine, with a Bridgeport vertical mill.


Nic Pottier said...

Looks awesome Ted!

So single butted means that one end is thicker and the other is thinner right? (basically one side of the raw tube starts off thicker, then the thickness tappers)

How do you decide how the thin sidewall ends join together? Or am I completely confused?

Ted Diamond said...

Single butted means the tube starts thick, thins out, and stays thin. My seat tube is single butted, with the thick end down at the bottom bracket. Double butted is the same as single butted, except that the tube thickens at the other end. The downtube and top tube are double butted.

So, everywhere there is a tube join, the mitered tube ends that join to the outside of the non-mitered tube have gotten thick again.

Chad said...

That looks great!

When can I put in my order for a custom DiamondCo Frame?

poser said...

yeah - no kidding. I need a road bike next season...

Ted Diamond said...

Why don't we see how my frame holds up first? Seriously, I'm not going to have the frame painted, but I'm going to give it a cheap coat of gray primer, which should show up all the imperfections in finish, rough joins, and when (if?) they appear, cracks. Then I'll batter it on the broken streets of West Seattle and Sodo. If it holds up for 6 months (at least), then let's talk.

I'd love nothing better than to jump into making frames for you all, but I need more practice, and more feedback from diagnosing failures before I let someone else risk life and limb on something I've built.

Anonymous said...

Yes, Diamond Frames has a nice ring to it. You'll be proficient before you know it. I've welded but my brazing has been limited to "sweating" copper pipe. Is the joint as strong as the parent materials? Have a great time Ted. Talk to you soon.

Ted Diamond said...

With a lugged frame, like the one I built, properly done, the joint itself is no weaker than the parent materials. In fact, it is the area adjacent to the lugged joint that is the most vulnerable, mostly because it is very thin tubing that has been weakened by heat. This manifests as tubes "buckling" from an impact.

If you look at my frame, there were a few areas where I "cooked" the tubes. Not paying enough attention to the heat that was building up in the tubes as I was fumbling around and trying to get the silver or brass to go where I wanted it, I let the tubes get hot enough to glow, and when they cooled, they were blackened (oxidized). Experienced builders like our instructors Ron, Gary, and Rick created neat little brazes that had the molten filler exactly where it needed to be, and with the absolute minimum of heat. That's what I aspire to, with practice.