The 1949 movie “Jour de Fete” shows a postman frantically chasing his bicycle, which rides away on its own. It could happen. Many bicycles, even without a rider, naturally resist tipping over if they are going fast enough. Scientists and engineers have been trying to explain bicycle self-stability ever since the 19th century. Now, a new analysis says the commonly accepted explanations are at least partly wrong. The accepted view: Bicycles are stable because of the gyroscopic effect of the spinning front wheel or because the front wheel “trails” behind the steering axis, or both.
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it’s because it pleases the flying spaghetti monster…
My only comment.. Jour de Fete! I have never seen this film referenced before on a tech site… I love Jacques Tati films.
“…front wheel “trails” behind the steering axis, or both.”
Look closely at the picture in this post. Is the above statement really accurate? I don’t think so. The steering axis/bearings are clearly behind the center of the front wheel, not the other way around.
I think what they meant to say is that the front wheel has ‘caster’, a term that describes the fact that the front of the bike has to be raised against gravity for it to turn from the center position. This is not quite the same as the principle used in automobiles to cause the steering to track in a straight line forward if there’s no input from the steering wheel, but the effect is similar.
You can verify this with a normal bike by turning the wheel and holding the bike in a vertical position. If you do it on a motorcycle, it’s much more obvious.
One interesting tandem two wheel vehicle effect is countersteering. To speedily orient the vehicle into the turn, push gently forward on the handlebar on the side you want to turn. The motorcycle/bicycle immediately banks into the turn. The technique is called countersteering because a gentle forward push on the right handlebar to initiate a right turn is counter-intuitive to pulling backward on the right handlebar to turn the front wheel to the right.