Monday, 7 December 2009

The Wheel


Something for my male readers.

It’s a sobering thought when you consider that whereas anatomically modern man and woman have been around for 150,000 years, 143,000 of those were spent without the benefit of the wheel.

For no particular reason, I was thinking about wheels over the weekend. Consider how the weight of a car is transmitted to the ground from the axle by a wheel. Sense dictates that the weight is supported by the strength of the metal in the wheel between the axle and the ground- i.e. the forces act downward in a direct line (allowing for the fact that a tyre is hollow), and is a result of the metal being in compression.

However, now consider the wire wheel. There’s no way that a few spokes of thin metal can support such weight, especially as metal under compression is quite unstable and can bend easily. What’s happening in a wire wheel is that the axle is actually hanging on the spokes at the top of the wheel – those spokes being under tension - with the force then being transmitted around the wheel’s rim to the ground. It seems counter-intuitive at first, but makes sense the more you think about it.

Taking this concept to its limit, there’s no reason why you can’t have a wheel with spokes made from chain-link – providing it’s not going to move from rest, as chain-link is not the best thing at translating rotary motion to forward motion. There again, neither are thin spokes, which is why they are set at an angle.

This had never struck me before I thought more deeply about how a wheel actually works.


8 comments:

  1. Chairman : you need to get out more.

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  2. Alan: I'm considering a chain-link engine now, so I can get out - possibly...

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  3. Chain link would probably move too much, causing friction & heat and wearing the metal too quickly. Interesting thought though, are you a closet geek?

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  4. Steve: How about when it's under tension though, so there's no movement - as wire wheels actually are.

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  5. Well, I'll be buggered... Never thought about that either. Now, I'll probably have bloody nightmares about it.

    AV

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  6. AV: Well you wouldn't, would you? Unless, of course, you were sad, like me.

    Ain't it odd that no women have replied. They're probably too girly.

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  7. I read this through twice trying to figure out why it was only for male readers. This is the sort of thing I find interesting. But as I was just typing this, I saw your own last comment. Might want to delete this one as being "too girly."

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  8. SAW: You need to read one of last week's posts to get the joke.

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