Friday, May 7, 2010

Moving a Derailleur Tab, Etc.

Now that I have finished my seat tube/bottom bracket, I need to tap and face the BB before proceeding to the next step. Except that I not have taps or facers—so I've ordered them, and things will proceed next week.

In the meantime, I thought I would move the tab on my Campagnolo horizontal dropouts, for Bike #3. As mentioned in a previous post, I'm doing this because I'm going to be using a Huret Jubilee derailleur and want to minimize chain gap.

Here is the dropout:

Here is the dropout with its tab cut off:

After this I filed the "recipient" area flat. Then I put the dropout and detached tab into a very crude fixture. I used a big C-clamp, with the surface touching the machined faces of both the dropout and the hanger tab, so that they would be in line. The C-clamp was a massive heat sink, but I just focused my flame on one small area and added a spot of brass.

Then I tacked the front of the tab. This time I used the C-clamp to keep the tab pressed up against the dropout. Here it is with both tacks:

With the tab tacked in place, I removed the heat-sinking C-clamp and brazed it together properly. It came out looking like this. It will file up nicely!

And here it is with the derailleur in place. (I tested it in a wheel, and yes, placing the axle all the way forward does drastically reduce chain gap—though I'll be lucky to get the derailleur to shift on to a 22-tooth large cog. Not a problem, really, since I'm planning on using something like a 13-21.)

I also did a few other things in the shop. I checked my TT miters for the thousandth time, and while there are still little gaps, I think all will be well. Here's a look at the head tube with the lugs in place:

I also trimmed the fork blades and started working on the dropouts. With roughly the right amount of rake in place, the next step is to stick everything in the fork jig and make sure it all fits together.

There's not too much to do until the taps and facer arrive in the mail. But I'm sure I'll manage to stay busy...


Anonymous said...

I'm intrigued by what you did with the derailleur tab. I have a Japanese touring bike from the 80s and acquired a sweet long cage Jubilee I wanted to dress it with, but it shifted like crap when I put it on. It was also very hard to get the wheel in the dropout as the derailleur got in the way. A nice Simplex SLJ solved both problems. I'm wondering if it had to do with the hanger placement on the dropout. In the latest issue of BQ there is a nice profile of a '50s Singer that Csuka modified to accept a Jubileee derailleur. The hanger is considerably farther behind the axle than even yours. Were Jubilees designed to work well only with their own dropouts? I have a sweet 70s Follis 472 that currently has Simplex changers, but have wondered about redoing it to make it much lighter. It has Simplex dropouts. Would I run into the same problem using a Jubilee on a Simplex dropout?

AH said...

From what I understand (from reading Bicycle Quarterly) the Jubilee actually didn't shift particularly well with Huret's own dropouts. (Yes, BQ is sometimes given to hyperbole, and I haven't tested this personally.) According to them, they only shifted very well on Alex Singers with the handmade hangers. One of the reasons I did this at all is to test Jan Heine's hypothesis: since it's a horizontal dropout, I'll be able to try the derailleur out in lots of different positions. (I think with the axle all the way forward in the dropout, it will be further in front of the hanger that on the Singers....)

I believe Simplex used their own proprietary dropouts (as did Huret), so I'm not sure you could even mount the Jubilee on Simplex dropouts. Even then, it seems unlikely you'd have much luck reducing chain gap, etc....

Anonymous said...

Thanks. By the way, I admire what you're doing on your site/in your shop. Working with your hands and on machines is a good way to offset the airier parts of academe--and may be more lucrative in the long run.

AH said...

Thanks! Hehe, yes, more lucrative in the VERY long run perhaps! For now it's just extremely fun -- and manual labour is good not only for "the soul," but also for writing. It's nice to mix things up a bit.

Back in the shop today, hopefully doing some cool fork-related stuff...