The Unridable Bicycle

Hardly anything could be simpler: you hop on, grab the handlebars, press down on a pedal and roll off. Indeed, it is so easy for most people to ride a bicycle that science has hardly bothered to answer a very obvious question: What gives the bicycle its extraordinary stability? Properly curious, a British research chemist named David E.H. Jones decided to do a little backyard experimenting. His plan: to identify the bicycle's essential stabilizing features by building one that completely lacked them. In short, he would construct a totally unridable bicycle.

Easier said than done. First, Chemist Jones tested the common theory that the bicycle's front wheel acts like a stabilizing gyroscope. He attached a second front wheel, parallel to the first that did not quite touch the ground. It could thus be spun in the opposite direction of the standard wheel, canceling out the gyroscopic effect. Jones optimistically named his creation URB I (for Unridable Bicycle 1). But surprisingly enough it proved to be easily ridable.

Hot Caster. Next, Jones investigated the notion that a bicycle's stability somehow depends on the position of the front wheel's point of contact with the ground. The rider, after all, usually steers instinctively in the direction of a potential fall, thereby moving the point of contact to one side and increasing the bike's stability. To foil that balancing act, Jones replaced the regular front wheel with a small furniture caster mounted directly in line with the steering-post axis so that turning would not shift the point of contact. Trouble was. the caster quickly became almost red-hot and could not negotiate bumps more than a half inch high. Jones abandoned URB 11 as inconclusive.

Next, Jones turned the front wheel 180 degrees so that its point of contact was farther behind the steering axis than it is in an ordinary bike. Instead of riding the bike himself, he simply pushed it off. "Incredibly," he reports in Physics Today, "it ran on for yards before falling over." By moving back the contact point, Jones had inadvertently increased the front wheel's torque. This twisting force normally counteracts the bike's tendency to fall over by steering it in the direction it is leaning. URB III was. in fact, even more stable than an ordinary bicycle.

Baffled, he turned for help to a computer. After analyzing many more unridable designs, he finally felt ready to build URB IV, an awkward-looking machine whose front wheel was four inches ahead of the normal position. The result was smashingly successful. Even when it was given a hard shove forward, the riderless URB IV quickly toppled. "It seems a lot of tortuous effort to produce in the end a machine of absolutely no utility whatsoever," Jones concluded, "but that sets me firmly in the mainstream of modern technology."

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