Carbon fiber also relies on constructed fibers aligned to address desired frame charac- teristics that are suspended in a resinous polymer matrix.
On top of these inherent strength characteristics, bamboo has a segmented, repeating, hollow structure along the stem of the plant, adding to the resiliency and aiding in the distribution of impacts. These same features serve to dampen vibration, creating a comfortable feel on the bike while still allowing for a stiff- ness and efficient transfer of power. The absence of knots and other inconsistencies provide for a consis- tent, predictable accounting for how this material will or won’t respond to exterior stresses. With predict- able strength, stiffness, and vibration dampening, bamboo’s viability as a frame material has a lot going for it.
Sounds good, but it’s all academic until you actually try to build the thing.
The one problem with living mate- rial is that it’s alive. Even after its harvested, it’s still subject to biological
and physical processes, specifically thermodynamics and decomposition. All of bamboo’s inherent strength char- acteristics won’t help if your top tube starts to rot, swell, or shrink under- neath you. To combat this, the bamboo has to go through a heat-treatment/ curing process in order to remove the material of as much moisture as possible, thereby slowing the decom- position process and severely reducing the one element that causes the mate- rial to contract or enlarge. This process also addresses any lingering pathogens or pests that may be making a home deep in the fibers of the bamboo. A resin coating takes these now-retarded natural processes and nearly arrests them. The result is a preserved, much more inert material that can be more reliably fashioned into bike tubing.
Of course, a bike’s great strength is not simply in the raw frame material, but in how you bring these mate- rials together. Obviously welding and brazing is out, making carbon lug joints the logical choice to assemble the tubes into a bike frame. Calfee’s first marketed bamboo bikes had these carbon joints, which worked great...for a while. While the natural shrink/swell processes were severely reduced by the curing process, the bamboo is still an organic material. It’s dynamic nature
every time the dog brought the bamboo back, it was in perfect shape: no fracturing, no splitting, not even any scratching.
persisted. This is not an inherent problem, unless the thing that’s holding them together is not subject to this shrink/swell process. Over time, the bamboo would gradually unseat from the carbon lugs as its diameter subtly changed through exposure to the elements. While this wasn’t cata- strophic, it wasn’t ideal. The solution came, just like the idea of bamboo as a bike material did, from nature. If marrying a dynamic organic material to a static artificial material didn’t work, what would happen if the connection was between two organic materials?
Enter hemp. Calfee started pulling dry hemp fiber through a vege- table-based resin and lashing the bamboo tubing together. Mirroring the construction of the carbon lugs, the bamboo is held together by the exponential strength of resin-coated fibers intentionally aligned to create strength and durability. Unlike carbon
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