Bamboo workability

Some notes here on working with bamboo for bicycle frame building.

The frame I am currently riding is the one pictured below. Living in WNC means I have a lot of gravel forestry roads to choose from and riding this frame on those roads is always a great experience. The vibration dampening is superb. Not to mention side impacts from rocks which happen quite often on gravel. The bamboo's strength in this respect is unmatched.

Working with bamboo to build a frame is fairly straight-forward. Because it is a grass this means the fiber runs in a single direction with great uniformity. This is also means it can be prone to splitting in that direction, however, by removing the "nodes" and using only cured bamboo the odds of it splitting are greatly reduced due to the lack of moisture. The real good news about splitting though is repairing even a fairly large split is easy. Because bamboo wants to hold its shape even after a split occurs means putting epoxy and some kind of wood-cap over the split works incredibly well. In fact, the repaired area may even be stronger than the rest of the tube. But with sidewall thicknesses in the range of 6-10mm and using cured bamboo the odds of getting a split are fairly low.

One really nice quality to working with bamboo for building a bicycle frame is cutting and shaping it. It is structurally strong yet soft when it comes to ease of cutting and sanding. Much of this is because of those fibers running in a single direction. I like to use a spindle sander to shape my miters and a foam sanding pad on an orbital sander for finishing the exterior of the bamboo. One limitation of bamboo is the junction at the bottom bracket shell. Now some designs online have created "joints" before the bottom bracket shell to make the distance between the chain stays wider for larger tires. I have found with a fairly wide diameter chain stay tube and proper alignment that I can still get a 32c tire to clear quite well. It is possible to design clearance for a 35c tire as well. Anything more and it is best to cut and epoxy the bamboo tubes together to create more clearance. In fact, this is the cool thing about bamboo because one can experiment with different geometries, similar, I would say to an old erector set.

In general, once a finish coat has been applied like a Polywhey or similar type product then the bamboo is good for the long haul.

Comments

  1. The hardest bamboo bicycle is made chassis. you have solved the most difficult problem is. good luck.
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