M Gee

  • Road Captain
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  • The user formerly known as hiero
Eh, what's that you say? Can't hear ya well, too much static! Speak up a bit, eh?    ;)[1]

OK! 96!  :angel

Your calc is right for the standard bike, but a bit off for her gearing ...

There are roughly 3.28 ft in 1 metre ... so 128 ft is approximately 39 metres per pedal rev - or about 4.2 standard bike wheel turns!!!   :o  . . .

DB, I apologize, I wasn't paying enough attention! On technical grounds though, you counted the cadence based on the video. And that could easily be inaccurate either as a result of recording speed or playback speed, as you commented. So I was thinking of a calculated number.

Kiwi is right, also - there was an error in my calcs, and I misspoke, swapping wheel revolutions for crank revolutions.

So here's is a calculation for today, hoping I'm paying a bit more attention:

For 700c: a 52/11 gearing is a 4.73:1 gear ratio - so 4.73 turns of the wheel per one turn of the cranks. Meters traveled depends on tire size. I picked out 700x28c since we are most familiar with standard road bikes. If Lukas' calcs are right, and I think they are, her gearing equates to a 363x12 gear, giving her a gear ratio of 30.25. A 16" bicycle tire will have approx 1.2 - 1.3 meters of circumference. And a ratio of 30.25 at 1.2 meters gets us a development of 36.3, which is close to the calculated 39, and serves as a tidy cross-check. Calculating the other way, 128 feet = 39.0144 meters, divide by a gear ratio of 30.25, and we get a wheel/tire circumference of 1.29 meters. Ok so far.

As just noted, one turn of the cranks = one "cadence" = 39.0144 m for Meuller's bike.
322,000 meters per hour = 5366.667 meters per minute.
Divide that by the development of 39.0144, I get 137.556, which should be the cadence required to reach that speed with those gears and wheels.

BTW, I totally agree that the video would be much improved by having a speedo and real elapsed time counter included in the display. A forward view wouldn't help any, as the salt flats are so barren that their is no visual reference.

Based on the assumption that John Howard and Denise Meuller are rational people, I have to also assume they have good reason to go with the smaller tire size. And, since they commented in one of the news stories that those tires and wheels were chosen because a normal bicycle wheel would not withstand the rigors of that speed, I have to conclude that building a 700c wheel that WOULD withstand such speed would result in a less practical weight for the wheel, and thus the smaller wheels. Could be other dynamics to do with wheel size as well. I know there are guys in the motorcycle forums that chew over numbers like these (wheel size) all the time. It's like coffee and eggs for breakfast - a daily routine!

Two useful sites for such numbers:

 1. Must be the long distance connection.  :lol
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