Saturday, May 1, 2010

Dropout Filing and Reaming Out the Seat Tube/Bottom Bracket

I have been busy once again in the shop, with two tasks.

The first—a pleasant one—was filing scallops into the dropouts I recently brazed on to the chainstays. Below is the driveside dropout. I had to file the dropout so that it met the chainstay flush, and I think it looks very nice indeed.

There are always a few pinholes in the brass, to which you need to add a bit of silver if you want to be a perfectionist—which I always do. There were only two such holes this time, one on the outside of the non-driveside dropout in the scallop, and one in the "I" of Ritchey on the same dropout. Here it is with the added silver:

And here all finished up:

The second task—less pleasant—was dealing with my screwed-up seat tube/bottom bracket joint. After my unsuccessful attempt to un-braze the joint, I ended up cutting the tube out of the BB. Here is what remained, thoughfully sandblasted (it was filthy!) by Olivier.

The only kind thing I have to say about it is that the removed tube left a shape resembling a heart.

At first I was quite upset (disheartened) at having to "waste" a tube. But in fact I did no such thing. I had left the entire butt at the end of the tube, since I wanted its whole length for my 64cm frame. So I can reuse the tube on a smaller bike. Below is the new tube meeting the old tube. They're more or less the same size. And it was inadvertently clever of me to cut that heart-shape; I preserved more of the tube... This picture has a gloomy, Ingmar Bergman feel, but in fact contains good news:

Then came the actual business of reaming the brazed-in portion of the tube out of the BB shell. I wasted about three hours of my day yesterday trying to do this with hand files. Because there is nowhere for the file to "exit" the closed BB shell, it's very tricky to maintain a straight file stroke. I would get the front and the back of the area I was trying to remove cut down, but the middle was still at full thickness.

Then I pulled out my "King Canada" fake Dremel. God bless this tool! I had bought it a few years ago to cut and finish aluminum fender stays, but never used it verymuch. It came in extremely handy for this job! There was a bit of a learning curve, but before long I had figured out how to get things quite even. It probably saved me twenty hours of hand filing.

This process revealed the area that didn't initially fill with silver. It was about 3mm long at the very bottom of the bottom of the backside of the socket, between the chainstays. This is conceivably big enough to cause a problem, so I guess I'm happy to took it out. In any case, I learned how to use my fake Dremel, and that's a good thing.

Here is the border of the black, unbrazed area. The black stuff is the "bad stuff"—presumably burnt flux? The little semi-circle above it is more or less the area that didn't fill. The only way this would have caused issues it if it has begun to rust out from the inside—which it may have.

Below is the reamed-out socket. You can still see a bit of silver left over from the initial brazing process. The new seat tube (which has been mitered and is ready to go!) fits in properly.

Tomorrow, one of my "shopping blog" posts will follow. My new tubular wheels, my Flite 1990 reissue saddles, and lots of Dura Ace front derailleurs...

ps: The below photo of me reinforcing the binder on my seat lug—from Olivier's blog—is totally my favourite "glory shot" from the shop so far. My lug! Lots of fire! A $1 lug vise! My precariously dangling sweatshirt hood ties! This is what framebuilding is all about!


James Black said...

Hi Adam,
Just want to say that I've been following your blog via the RSS feed, and appreciate your discussion and insights into your build process. I respect your perfectionism!
James Black

AH said...

Thanks James!

RMHampel said...

It is as if James read my mind, Adam. Your purist instincts seem so right for this project. One could never afford to pay someone else for this kind of attention to detail. Not only that, no one else is likely to "get" what your vision of the bike is. It is something you are doing for yourself. Thank you for letting us watch the process. Well done.

AH said...

Thanks again for the comments! It's nice to know someone's reading—and "getting it" along with me!