Elongation of Rockabilly Boogie and Other 1 & 3 Speed Bikes
3:10 pm, by tricky coyote[photopress:Photo_042506_005.jpg,thumb,pp_empty]
Here’s how to Xtracyclerize any narrow-rear-wheel (otherwise known as overlocknut dimension, or OLD) bike:
1. Spread the rear triangles of the bike until the dropouts are just wide enough to fit inside the FreeRadical’s Boss Hogs. You can have your bike shop do this with their frame spreading tool, or you can do it yourself. Get two 2×4s about 30″ long. Put their flat sides together and insert them parallel to your chainstays inside your dropouts. When they are as far forward as they’ll go, pry apart their ends to spread the dropouts. Spread, release tension, and check; spread, release tension, and check. You don’t want to spread too far and then hafta squeeze back cuz this will overly tax the frame.
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2. Squeeze the FreeRadical frame. (The alternative is to just get a longer axle and some spacers, but as long as you’re going to always have the FreeRadical on this bike I think it’s better to squeeze the frame. All other things equal, a shorter axle is stronger.) Get a bar clamp. Pad the FreeRadical Long Stays right above the dropouts with some small scraps of wood. Turn the screw until the frame done been squoze to just the right width. Again, squeeze, release, check; squeeze, release, check.
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FreeRadical frame ready to be squozen (squoozed?).
3. This step is only for the Rockabilly and its 3-inch tires! Don’t go chopping off your brake posts for no reason! Chop the FreeRadical’s brake posts off with a hack saw or angle grinder. File rough edges and paint. Make sure you just cut the brake posts, not any of the Long Stay!!
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Here you see my black paint job on the cut-off brake nubs and my little art part. I was in a hurry and didn’t do too nice of a cutoff job, erring on the side of leaving more material intact. You also see how I dented the stays a bit to give more (sufficient) tire clearance (see explanation below).
4. This step is also only for the Rockabilly and its 3-inch tires! You’ll either need to shave some corner rubber off the tire or indent the Long Stay just a bit to make clearance for the tire. I padded the frame and put the Stay in a vice just to make a little indentation. It’s barely noticeable. You could also use a bar clamp to do this part. Make sure you put a really stout, long pad on the outboard side of the stay and a small one on the inboard side. That way, the inside will dent but the outside won’t. Better than a piece of wood on the inboard side is to use a bolt. The bolt will more precisely dent the stay.
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5. Tensioning the chain, I found it very useful to have one of these half-chain-link pieces to get the chain to just the right length. Instead of being an inch long like most links, it’s only a half inch and was just what I needed for optimal tightness.
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One-speed chain half link.
One more thing. Like I said in the recent post , I think the Rockabilly Xtracycle is patently unsafe without a front brake, and I’m planning on getting a drum brake hub (the i-brake from SRAM, perhaps with the i-light, too) built into my front wheel.
April 26th, 2006 at 11:15 am
It’s not a good ideal to try and spread the chainstays on an aluminum or carbon fiber frame. Steel, though is fine. I like your technique; it’s well thought out.
April 26th, 2006 at 12:22 pm
Hey Rider,
I’m glad you bring this up. I heard that once, too. Our local bike shop heats up the aluminum frames before spreading. I just went ahead and did it on the Rockabilly, even though it’s aluminum, without heating. It seems like such a minimal amount of spreading, but it’s the reason why I knew I didn’t want to spread it too far and then have to spread it back. I’d be way more concerned about it if it was somewhere in the front of the bike where failure would be likely to cause a crash. With the minimal bending I don’t think it will fail, and I really don’t think I’d lose control if it did, “it” being a chainstay cracking. If someone out there knows more about this subject, I’d love to hear.
April 28th, 2006 at 8:08 am
The problem comes (so I’m told) with frames that have been heat treated after welding. Early Cannondale frames were done this way. Heating the frames to bend the stays caused problems with the strength of the aluminum. Now, I don’t know any of this for a fact. But I have been told all of this by folks a lot more knowledgeable than me.
Also, with the OK of my Cannondale dealer I ran 130mm hubs in an early model Cannondale that came with 126mm spacing. The fit was only a tiny bit snug and I had no problems at all over thousands of miles. I did not bend the stays at all; they had enough “spring” to accomodate the extra 2mm on each side. Good luck with the conversion.