Nov 28


November 28, 2003

After a couple of days of fiddling with the position of the intermediate drive (the gear cluster normally known as the rear cassette) and the derailer, I finally figured out a place where my knees wouldn't smash into the spinning gears. Unfortunately, I needed to add some structure to mount the drive about a foot above where I had originally thought it would work (directly on the head tube). This new position is a lot higher than I had planned, and is a concern with regard to the fairing that will eventually envelope the bike. The most efficient fairing would be a very gradual slope from the pointed nose to the tallest part of the bike which is where my head will be. However, the drive is now a bit higher than my knees, and seems to be about the same height as my head. Since my knees are almost at that height, it looks like I wouldn't be able to achieve that kind of gradual slope anyhow.

This brings up a good point - in order to obtain the most efficient and laminar aerodynamic shape, I need to GRADUALLY increase the slope from a point in the front of the bike, to a round area near my head. Below is an illustration of the current design and how a fairing would flow around it. The blue dashed line is the fairing and the red dashed line is where my feet need to go. Note the bulge over the intermediate drive cluster.

Now, if I went with a LINEAR drive, and traditional rear wheel drive (route the chain to the rear wheel rather than the front), I could eliminate all the frontal bulging. A linear drive is simply a crank that goes back and fourth rather than around in circles. Theoretically, it should make no difference to the efficiency, as you would expend exactly the same amount of energy turning something as you do pushing it. In fact, it may even be a more natural motion - however, my legs are not trained to pump back and fourth and that might be an issue. However, here is an illustration of what the resulting fairing would look like - it could very well be appreciably more aerodynamic. I need to look into this....


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