Selecting Bamboo
There is surprisingly little on the web about how to choose bamboo species. I have done a fair amount of research and have figured out a few things.
Local Sourcing & Bamboo in General - A few comments.
Finding it. Sure it can be hard. I found mine by contacting the local chapter of the American Bamboo Society.
It is important that you choose older bamboo poles. Younger poles are not fully developed structurally. Also some poles are born to split, its better to have a pole that his demonstrated its worthiness for your bike. You can generally tell the older poles by looking for weathering, if it looks like an polished pretty thing, its probably very young.
Second, the poles will have the thickest walls near the base of the pole. These thick walled pieces would be a good choice for your seat tube since it bears a lot of weight. Keep in mind that the rear triangle bears a lot of the brunt too. Choose your pole carefully.
Third, the nodes on the pole are the weakest point. The individual fibers traverse to the other side of the poles. This is apparently the weakest link, so try to avoid using them for structural components.
Fourth, respect the bamboo. Each piece is different. Try to figure out how best to use bends, thick walls, etc to better suit the build characteristics of your bike.
Bamboo Types
Probably the most common bamboo is Phyllostachys or taiwan bamboo:
Taiwan Bamboo (Phyllostachys)
Black Bamboo Poles (Phyllostachys nigra)
Black bamboo while terribly sexy appears to be prone to splitting also, at least according to bamboo forum folks. The poles that do make it however appear to have thick walls and come in a convenient variety of diameters. In the end this is the only type of bamboo that I found that could meet my diameter requirements. I ordered my poles from bamboofencer.com although you can also get them from bamboohardwoods.com. Its a bit expensive but the poles are very nice. I ordered three 8 foot, 1 and 1/2" diameter for the main triangle and three 8 foot 1"-1 1/4" poles for the rear triangle. Having extra was key. I would recommend buying one additional 1"-1 1/4" diameter pole (make 4 total) to make sure you have enough to work with (smaller poles have a strong taper and thus don't give you as much room for error).
Tonkin Bamboo (Arundinaria amabalis)
The bamboo of choice apparently, according to one of my bamboo friends, is tonkin. It is strong light and less prone to splitting.... apparently. This is the type of pole commonly used for bamboo fly rods. Unfortunately I couldn't get it in the proper diameters, but I just found that bamboohardwoods.com has it.
Heat Treatment
Heat treatment is really frikin important. Apparently it hardens the sugars inside of the canes, kills unwanted guests, and helps remove some moisture. I have read many times that you should use a regular propane torch, starting at the base of the pole work your way to the top. The method to temper the bamboo is to heat it when it is green, with a propane torch, moving the flame up and down the surface of the culm until it changes from shades of green to tan and if desired, to darker shades of brown. I suggest a light browning for the first step. Then you have to dry the stuff, for real. The torch only partially removes the water content. Alternatively if you buy the stuff through a good supplier your poles are likely pretreated and dried. Keep in mind that some of the poles bought from abroad will have been chemically treated, and we all know that chemical regulations in developing countries are lax at best. So be careful and use a proper respirator. Anyways, in this case I would just heat treat the individual poles that you buy before you use them. Some types of bamboo might react poorly to heat treatment, so keep that in mind if you are having trouble.
Drying: Locally sourced poles however still need to be adequately dried. People on "bamboo forum" have a number of views, but I think stacking them vertically for about 3 months, yes 3 months, does the trick. To avoid getting mold build up make sure that they get adequate air circulation. Also keep them out of direct sun. If you don't dry them properly (and heat treating them with a blow torch doesn't count) you are likely to have more splitting problems. Some poles just seem destine to crack, better to find that out before they are part of your bike.
Smoking Bamboo: I have also read about smoking your bamboo poles. Apparently you can use scrap bamboo or cracked poles to smoke others. Apparently the tar from the burning bamboo helps to protect the bamboo from mold, pests etc and some site even claimed that it helped avoid cracking... can't verify that. Some types of bamboo might react poorly to heat treatment, so keep that in mind if you are having trouble.
Although I haven't tried it this is what I'm thinking. I was planning (didn't get around to it) to use my father's old barrel smoker. Soak the bamboo pieces in water and then throw it in.
If you don't have a smoker you might trying to do something like this. You could add a right angle to the air conditioning tube and laying the poles in there.
Links:
www.bamboocraft.net/ Tons of topics, more detail than you need
www.bamboohardwoods.com Supplier of bamboo poles: Tonkin, Black, Moso
www.bamboofencer.com/ Supplier of bamboo poles: Tonkin, Black, Phyllostachys
http://www.americanbamboo.org/ All kinds of bamboo info
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