The Science of Bicycle Motion Gets a Re-Do

Illustration for article titled The Science of Bicycle Motion Gets a Re-Do

Bicycles, huh? When I was younger I found them to be mystical, two-wheeled things that remained upright seemingly by magic. Training wheels were my crutch until one day dad ripped them off and gave me a shove down the street.

Weeping, I wobbled forward, fear in my eyes and terror in my gut until...I realized I had remained upright and was not, fortunately, going to die a painful death at the hands of the asphalt racing by my frantically pedaling feet.

What kept me upright was believed, by scientists and physicists, to be the result of wheel rotation and what's called "gyroscopic effects." Pretty straightforward and, for the longest time, it was the accepted reason Why Things Were The Way They Are.


But then this week the journal Science came along and upturned the rickshaw with their quirky looking bicycle physics-testing, gyro-negating contraption (seen above):

[U]nlike a normal bike, the front wheel of their vehicle lies in front of the steering axis, so the caster effect can't operate. On top of that, both front and back wheels are connected to duplicate wheels spinning in the opposite direction, so any gyroscopic precession is canceled out. - CNET

When they gave the thing a push, it remained upright until forward motion ceased, at which point it toppled to the earth much like I have done many times since receiving that fatherly push more than 20 years ago.

What the experiment showed is that the accepted reason for bicycle stability was only part of this newly refreshed puzzle.

"It's all about how bicycle leaning automatically causes steering, which can bring the wheels back under a falling bike," said Andy Ruina, professor of mechanics at Cornell and a co-author of the paper [...] "Almost any self-stable bicycle can be made unstable by misadjusting either the trail, the front-wheel gyro, or the front-assembly, center-of-mass position."


A constant state of falling and correcting. Sounds like a planetary orbit. Or my early days on that kid-sized Huffy. [CNET]

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This leaning to steer effect is well-known among motorcyclists. It was one of the first things I learned when I learned how to ride motorcycles.

I imagine since bicycles are usually operated at slower speeds it isn't as apparent that this is happening.