Of Spinning Things and Natural Supercomputers...

Well, it's been about twelve days since my last post, which is about twelve days in blog days. And about a hundred days in Twitter days, if you're interested.

I often try and work out what to write about in this blog whilst cycling home in the evening. Spending forty five solitary minutes on dark, deserted country roads does have a way of relaxing my mind (when I'm not busy roaring at the wind, that is).

And sometimes, if I'm particularly lucky, a topic falls into my lap. Or rather, my lap - and the rest of me - falls to the floor and that becomes a topic (see my first post).

Incidentally, where does your lap go when you stand up? Troubling...

Anyway, I often wonder, while cycling, how on earth I do it. I'm really quite proud of myself to be honest. I mean, I manage to tame this two wheeled contraption and bend it to my will. I don't fall over, in general (again, see my first post). In fact, I move more swiftly from A to B than I would if I didn't have a machine to wrestle with. And I do it all without an intelligent octopus in sight. Just man and machine working as one. The bike an extension of my arse.

And it seems I'm right to wonder how I manage it, because the science of how bikes work still seems to be the subject of some conjecture.

It might strike you as strange that something as simple as the mechanics of a bike can defy full scientific understanding, especially given the incredible things science can do.

But there's a big difference between "simple" and "deceptively simple". And the interraction between a bike and the human riding it is actually quite complex.

It's often said that bikes stay up because the spinning wheels act as powerful gyroscopes.



The theory of how the gyroscopic force keeps bikes on the straight and narrow is outlined (in a simplified way) in the diagram above.

But now I want you to strike that image from your mind, because - alas - it's wrong.

Or rather, it's not entirely right.

Yes, my handywork with Microsoft Word Drawing Tool isn't entirely in vain. It represents a perfectly fine theory of how the bike stays balanced, if you're one of those annoying show-offs who likes to cycle without the use of handlebars.

If you detect a hint of bitterness at this point, you'd be right. For all my poise, grace, power and speed in the saddle (I'm almost certain I broke the sound barrier the other day), I've never been able to master riding without holding the handlebars.

The use of handlebars, then, and the weight of the body pressing down on them, makes the gyroscopic force insignificant.

This has been confirmed in experiments. A Dr Hugh Hunt from Cambridge made a bike with a second front wheel (see below), which rotated in the opposite direction to cancel out the gyroscopic force. And it turned out that this bike could be ridden just as easily.



So if the gyroscopic force doesn't keep bikes upright, what does?

Well, the answer seems perhaps more mundane, but is actually probably more impressive.

It boils down to the human brain's incredible ability to react to the world around it, and instruct the muscles in such a way as to make the tiny corrections neccessary to keep bike and rider balanced.

So perhaps I was right to be proud of myself after all!