At 6:26 PM -0300 9/23/07, htravis@attglobal.net wrote:
>Don't trust the rider to be constant between trials? How about using
>gravity? A spreadsheet, some tyre changing irons, an air pump, a
>pressure guage, and several tires to switch between. A cyclometer would
>be nice. Several $15 stopwatches borrowed from the summer swim team will
>help. Record time vs distance for several points, and apply a little
>secondary school maths and physics. Want to validate your model with
>different speed? Find a steeper hill. Heavier load? Sling a pair of
>partially filled sandbags (gently) over the top bar.
You are basically describing Bicycle Quarterly's tire tests. The investment in money is basically the purchase of the tires (plus, I bought the bike we used from our contributor, so it doesn't get changed and we can reproduce the results or test new tires when we want to.) The investment in time, because you need at least 3 repeat runs for each configuration, plus you need to get lucky and a windless day, is more significant. Our test rider has ridden more than 100 miles, up and down the same 1/8-mile hill more than 500 times... and the two time-keepers have watched him do this... it's an interesting way to spend your Saturday mornings. (5-8 a.m. is the time when there is the least wind in Seattle.)
For aerodynamics, you need higher speeds, and the variables become very hard to control, so we used the wind tunnel of the University of Washington. We were lucky that Lance Armstrong had worked out the methodology and perfected the bike mount, so we could dive right in. Two days later, we knew a lot more about things like fenders, bags, rider position/stem height and clothing. Our tests addressed issues that racers don't care about, but that are important for real-world riders, such as how much does a rain jacket slow you down or is a British-style saddlebag more aerodynamic than a French-style handlebar bag. The report is in the latest Bicycle Quarterly.
Jan Heine
Editor
Bicycle Quarterly
140 Lakeside Ave #C
Seattle WA 98122
http://www.bikequarterly.com