Archive for January, 2015

27
Jan
15

Playing Hide and Seek With The Brake Cable…

Next up: plumbing an internal brake cable in the top tube.

This….was a whole lot trickier than I thought it would be, at least in terms of my skill with a torch.

One of the things that I wanted to try with Number 4 is to get a little fancy and do an internal or “hidden” brake cable. The concept is pretty simple – instead of those cable stops that you normally see on your top tube, you install a brass tube on the inside of the top tube that will carry the brake cable back to rear brake. There are two ways of pulling this off; you can either use a large diameter brass tube and carry the whole brake cable and housing through the frame, or you can use a small gauge tube and just run the inner cable through the frame. I chose the latter. It is a bit more complicated, but I figured that it would be slightly lighter and there would be less of a chance that the cable housing would rattle around in the internal routing. Noises like that drive me nuts.

The next choice to make was to figure out where I wanted to pierce the top tube for the cable entrance and exit: top, sides, or bottom. A good buddy of mine, Slippery Pete, suggested that going in from the top invited water and sweat to make its way into the frame, resulting in corrosion. Pete is a smart guy, so I opted to pierce the top tube at about a 5 o’clock position. I figure that this is far enough around to discourage water from seeping in and also it puts the cables in a position that will help keep them away from the paint on the seat tube and head tube.

I know: vanity.

Drilling the holes was easy. In order for the cable ends to sit at the necessary angle, you need to elongate the holes. I did this by taking a hand drill with the appropriate sized bit and VERY GENTLY tipping the drill to the angle that the cable will enter the tube, using it like a mill to elongate the hole. You have to be gentle because the metal is very, very thin in this part of the tube (it is butted) and is easily bent or torn. I finished it up with a rat-tail file.

I next fabricated the internal bits – two cable ferrules and some brass tubing. The trick here is to anneal the brass tubing so that it bends easily without crimping. This is easy – just heat the tubing until it turns a silvery-gray color. I silver brazed the ferrules on the end of the tube, and gently bent the fixture into shape. I cheated a bit and used a tubing bender – it is basically a spring that slips over the tubing and helps the tube keep its shape as you do your thing. After some gentle tweaking and pulling, I was in business.

Finally, there are some little stamped steel dress-up doo-dads that go over the ferrules to finish it off. Here’s what everything looks like before you install it.

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The really tricky part turned out to be the final assembly. As mentioned earlier, the Pego-Richie stuff is light weight butted tubing, and the part of the tube that I was playing with is surprisingly thin. That meant that it heated VERY quickly when I aimed a torch at it. I had to work fast and keep my wits about me to avoid overheating things. In the end it turned out nice and cleaned up well:

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The final test was to see if it actually worked. I ran an old brake cable through the internal routing – it ran nice and smooth, with no binding.

So nice, in fact, that it was enough to make the pretty girl smile….

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