Saturday, January 12, 2008

More seat clusters

Here is a seat cluster from a bamboo bicycle made by Calfee:

Yes, bamboo. The canes have been selected, cut, and mitered, and are held together in this case by hemp soaked in some sort of resin. Other bamboo frames by Calfee have been "lugged" together with carbon fibers in resin.
This bike rides really nicely-stiff like aluminum, probably due to the oversize tubes, er, sticks, but more muted like a nice steel frame. There is not much springiness, though, like you would find in steel or titanium-bumps and blips and waves in the pavement don't twang or resonate or bounce like in some frames made of those metals. Hits are not as sharp, nor do they have that hard, stomping-on-a-rock bone-jarring feel of a big-diameter aluminum frame. I don't know how to explain this, it's like talking about have to use words that are relative to other things. Like "blue," a color, is understood to mean "sad" or "melancholy" in music. This bike feels a little transparent-it's tough to pin a character onto it, though. "Alive," maybe? Perhaps because the frame is made from an organic substance-it feels like it is actually working on its own, maybe pushing back against hits. Power transfer is great-it doesn't hesitate in a jump, doesn't seem to flex unfavorably, doesn't creak or groan. Perfect alignment; I can let go and sit up and it goes right straight ahead, no bobbles or wobbles or leaning or arm waving, it goes right where I look. And it hums, literally...makes a sound like a soft whirring hum as it rolls along. Hrmzhhhhhhhh. At first I thought it was the tires, but these GP3's are on other bikes that I ride, and they are really remarkably quiet in those other instances.
Evolution has done well with bamboo-the density is greatest toward the outside, rather than in the heartwood as with a tree. The canes used in the toptube and dowtube of this frame are from plants dozens of feet high. Think of a tree dozens of feet high-you couldn't get your arms around the trunk. These centers are actually hollow. In the orient they build skyscrapers using bamboo staging. It is said to be stronger than steel in some ways; supposedly any weakness is absorbed by the whole (flexible) structure rather than being concentrated in a stress riser resulting in a break. As the plant grows, it sends more mass to weak areas-thicker cell walls, more cells, cellular structures oriented in a particular way. And if there is damage or an injury of some sort, it heals stronger than it was before. Someone opined that this frame really is "carbon fiber," and I suppose that's right-what we normally call a "carbon fiber" frame is actually made of resin held together with fibers oriented to give a particular kind of rigidity, or layered to give a particular level of strength or durability. "Carbon fiber" frames have evolved for what, 20 years?, by being subjected to rides and crashes and technical advances, among other things, whereas bamboo has evolved in response to its natural environment for millions of years.
Stay tuned, more in later posts...

Calfee is known primarily for handmade carbon-fiber frames, and here's his signature seat lug:

This is a demo bike in my shop. And just about the most seductive thing going. Raw finish, no clear coat or paint or nothing-when you touch it you're touching the carbon fibers. Paints and clearcoats and translucents of all sorts are also available, so if you don't happen to like the stealth look you can have something else. Like the bamboo bike, this one is perfectly aligned. Handling is beyond excellent. Balanced, neutral, predictable, straight. Gets better the faster you go. Maybe just a tad on the rigid side, but that's just me looking for something to say. Quiet and damp like you expect from carbon fiber. There's another one of those words-damp-borrowing from acoustics.
Calfee is said to reject a number of forks that he receives-apparently every one goes into his jig and is either accepted for use with a new frameset or rejected and sent, uh, somewhere else. I don't know how many he actually rejects, and what brands and models they are, or how he gets away with that at all, but the end product is fabulous. Top-tier.

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