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This question has got me hugely excited about building a bamboo bike. I've found some instructions and tips here and here.

I plan to find/buy an old bike to use as a donor. I think I'll use the head tube, forks, stem (basically the whole front end) from the donor bike to minimise compatibility issues. I'll use the dropouts from a bmx, since I'm building a fixie and it has horizontal dropouts.

Which leaves the bottom bracket. I could buy a new one from a framebuilding supply site or use the one from the donor bike.

My questions:

  • What do I need to consider for the bottom bracket? Should I use a cartridge style bearing and buy some single speed cranks?
  • What are the odds that my old donor bike will have a bottom bracket shell that will fit with the new bottom bracket bearings? Do I need to buy a bottom bracket shell from a framebuilding site?
  • Are there any other complications I've overlooked?
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My gut would be to go with a cartridge. You can retrofit cartridges to most reasonably common BB styles, and you're assured that the bearings, cups and crank are all compatible with each other. In a pinch the cartridge can be glued into the BB, or you can cobble the necessary retaining cups -- precision isn't really required. –  Daniel R Hicks Oct 27 '11 at 0:43
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3 Answers

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Take a look at Sheldon's entry for "bottom bracket"; it lists several different types, but most of them you'll never see. Most bikes made today use the "British" BB shells. You might also see a few of the one-piece cranks (especially on older BMX and dept-store bikes), but this design is becoming obsolete. So if you get a donor bike that doesn't have a one-piece crank, then you should be able to find a compatible BB at any place that sells bike parts.

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That looks just what I was after. So hopefully any bike I get will have a compatible BB shell with modern cartridges. Thanks! –  Mac Oct 28 '11 at 4:45
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I would agree with Daniel about the cartridge style BB. Just make sure whatever cranks you get that they're compatible. One thing to think about with bonding, if you plan to use carbon fibre you will need to do some form of barrier layer to protect the steel, otherwise overtime the carbon and steel will have a chemical reaction that causes corrosion. Applies to any carbon and steel bonds, not just the BB shell.

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Thanks for note about the barrier layer. It seems from my googling that people have used a layer of epoxy. Do you know if this will work? –  Mac Oct 27 '11 at 23:38
    
Or you could use aluminum instead of steel. –  Mike Baranczak Oct 28 '11 at 3:13
    
You could use aluminium, however you then run into issues around the different rates of thermal expansion. From what I understand, Bamboo and steel have similar rates of thermal expansion, whereas aluminium is slightly different. This would likely cause the joints to weaken over time because the different rates of expansion and contraction. Titanium actually delivers on all fronts except the price front. That's why a bit of epoxy or fibreglass should do the trick to create a barier layer. –  Dan Oct 28 '11 at 9:12
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I think you should select a donor frame with characteristics you feel comfortable to work with. So, if you can fully assemble the donor bike, you just cut it in pieces, take the parts you want and assemble the bamboo bike with the same parts.

If you are a novice with bike mechanics, it would be VERY advisable to get a frame, build a complete bike from it by yourself, ride it for a while, then disassemble it. For sure you are going to get precious insights about your own skills, some tricks involved in assembly and disassembly, and you will have time to change your mind (change for another frame, or another frame type or size) before you actually CUT anything ;o)

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Thanks for the advice. I've done pretty much all maintenance on my bikes except for the bottom bracket. The trouble is most donor bikes I see are old 10-speeds and I'm not sure how to convert the cranks to single speed cranks (or if I even need to) –  Mac Oct 27 '11 at 23:40
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