Some of my more faithful and observant readers (all four of you) might remember the Electric Hub Motor Bicycle Prototype that I built. Down at the bottom of that post I mentioned that I had designed a bicycle rear dropout for a friend of mine. Here is a picture of the CAD model that I did:
Bicycles and similar things are interesting and fun to design because almost no part of it is at right angles, straight or intuitive. There are a lot of compound angles to deal with and of course it has to be comfortable which usually means adjustable. Bamboo makes it even more interesting thing to use because you have to assume that the bamboo will be straight. At least unlike metal tubes you can't really bend it around the tires and other places. Because all the frame tubes have to be straight it makes the angles in the dropouts even trickier.
Well my friend has started construction of the bicycles that these will be used on and I thought that I would share some pictures of the process. The frame of the bike is being make with bamboo instead of steel or aluminum tube. Bamboo is a really cool material and I use it myself in a lot of my lathe projects because it's cheap, the grain is tight, it's strong and did I mention that it is cheap?
The above picture is the frame being assembled and glued together on a jig. The dropouts are in the lower left corner and are where the rear wheel attaches and the frame tubes (seat and chain stay tubes) come together.
The jig is built on a wood base that has a 1:1 printout of the bicycle frame with holes drilled through the wood and the paper in all the important places. Above is a picture of the jig holding the dropouts with the adjustable pivot's to allow some play in the angles. The bamboo is attached to the metal components of the bike using 2 part epoxy.
Just a quick post to close the loop and answer all the questions that I had (none) from the mention of Dropout design in the Electric Bike post!!!