The latest email from Instructables had a link to a cool looking bicycle: Made from bent and laminated plywood, the frame itself flexes to provide suspension action. The plywood is 1/8″ birch. The frame is built up a layer at a time: plywood alternating with fiberglass and epoxy resin in what looks like a labor intensive process. Lots of trimming and sanding.
The head tube (where the front forks attach) and the seat tube are made from fiberglass wrapped around a PVC pipe, and also layers of brown packing paper expoxied on top of the fiberglass. The paper is used to build up the thickness of the tube in small increments. The seat tube in particular is has to have accurate internal and external dimensions: Internal for the seat post, and external for the front derailleur. To keep the wood look the tube is finally wrapped with a layer of birch veneer.
The bottom bracket (where the crank is attached) is mounted to the frame starting with a few strips of fiberglass to start with. It is strengthened by lashing many turns of natural fiber rope around the frame and bracket, with the rope pre-wetted with the epoxy resin. It looks pretty good on this style of bike.
The head tube is a critical piece, since being off by a few degrees could mean that the front fork interferes with the frame, or that the front wheel is not in line with the frame.
After that the remainder of the assembly is similar to that of a normal bike.
The wooden bicycle was entered in the Instructables woodworking contest, which has some great prizes and is open until Oct 3.
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