Monday, June 21, 2010
  Book-learning doesn't explain bike-learning

Yet another team of researchers has tried to reduce bicycles to mathematics, and they've failed.

The complex equation, which takes into account inertia, gyroscopic and centrifugal forces as well as gravity, has 31 numbers and symbols and nine sets of brackets.

The formula boils down to: Inertia forces + gyroscopic forces + the effects of gravity and centrifugal forces = the leaning of the body and the torque applied to the handlebars of a bike.


Nope. If the torque applied to the handlebars is a major factor, they've missed the point entirely.




Bicycle riders know ... and many earlier researchers have agreed ... that the handlebars are insignificant. When coasting on level ground you can skip them entirely. You need them as an anchor when you're pedalling hard, but applying torque to the bars is exactly the wrong way to ride, and an excellent way to crash. The only time you use the bars in a sort of 'torquish' way is to damp an incipient shimmy. And in that situation you're not twisting the bars, you're only pushing harder on both sides to stop an externally generated wobble.

= = = = =

Another article on the subject gives the equation, but without saying what any of the terms mean:



This leads to another of Prof Polistra's Peeves: the complete lack of 'narrative' in public coverage of math. You can see this dramatically in almost any Wiki article on a math-related subject. The formula is always shown in terse notation with lots of strange brackets and Greek letters, instead of a form that can be checked by non-insiders. There's no excuse for this in modern times. Greek letters and subscripts were convenient when math was all pencil-and-paper, but they're extremely inconvenient and error-prone in the computer world. Far better to express a formula in pseudocode form with meaningful variables, so a scientifically literate reader (who isn't among the half-dozen specialists who know the equation!) can copy and paste, transpose it into his favorite programming language, and check it out or use it for practical purposes.
 


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Polistra was named after the original townsite of Manhattan (the one in Kansas). When I was growing up in Manhattan, I spent a lot of time exploring by foot, bike, and car. I discovered the ruins of an old mill along Wildcat Creek, and decided (inaccurately) that it was the remains of the original site of Polistra. Accurate or not, I've always liked the name, with its echoes of Poland (an under-appreciated friend of freedom) and stars. ==== The title icon is explained here. ==== Switchover: This 2007 entry marks a sharp change in worldview from neocon to pure populist. ===== The long illustrated story of Polistra's Dream is a time-travel fable, attempting to answer the dangerous revision of New Deal history propagated by Amity Shlaes. The Dream has 8 episodes, linked in a chain from the first. This entry explains the Shlaes connection.

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