I’m in the process of designing the second bamboo bike and have decided to go down the route of making custom drop-outs. The ones I sourced for the first bike were OK, but they needed a lot of modification in order to get the bamboo and carbon fibre to sufficiently adhere to them (I had to extend them with threaded rod). The pic of the ones I’ve designed below feature a series of holes drilled through the metal, which will provide increased surface area and grip for the epoxy resin to grab onto. A 10mm wide and 50mm long slot is cut into the end of the bamboo poles and these holey tabs will slot in and then be wrapped in carbon fibre to join them.
If anybody knows of a good laser cutting service here in Melbourne, please let me know.