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Author Topic: Why do bicycles stay upright so well?  (Read 2974 times)

Ian Vermes

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Why do bicycles stay upright so well?
« on: 27/09/2011 16:01:02 »
Ian Vermes  asked the Naked Scientists:
   
I have a question for the naked scientists as I am yet to find an answer to it: it's been shown that bicycles have a curious property of remaining upright and stable even when sent rolling down a hill with no rider.

So why do bicycles remain upright when they should topple over?


What do you think?
« Last Edit: 27/09/2011 16:01:02 by _system »


 

Offline Geezer

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Why do bicycles stay upright so well?
« Reply #1 on: 27/09/2011 19:18:59 »
Hi Ian,

It's because of a very subtle mechanism that causes the steering to adjust so that the bike returns to a vertical state as soon as it starts to fall over. Some blokes (in Holland?) built a special bike recently to investigate the process. I think there is a TNS article on it.
 

Offline CliffordK

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Why do bicycles stay upright so well?
« Reply #2 on: 27/09/2011 19:59:56 »
It's because of a very subtle mechanism that causes the steering to adjust so that the bike returns to a vertical state as soon as it starts to fall over.

???

Are you talking about a learned compensation by the rider?  Or an intrinsic property of the bicycle. 

Most forks are raked forward slightly which would tend to keep the bicycle going in a straight line, but that is not sufficient to keep it upright.

There is some contribution of the wheels that act like gyroscopes, and it is much much easier to balance the bicycle while it is moving than to balance it while it is stopped, presumably also because one can correct balance with steering.

I suppose, if you are talking about humans correcting for balance, the question is why riding bicycles is so innately human.  How long have we had bicycles, maybe 200 years out of 5 million years of human evolution.  So, why are they so easy to ride?  Obviously there is a learning curve for children, but they pick up the skills rather easily.

Is riding a bicycle like riding a horse?  Paddling a boat?  What other skills would have allowed the evolution of the ease to ride a bicycle?

Perhaps even if one is running, one  learns how to lean into corners.  Balance for walking is not a simple task.  Consider how natural it is to carry a heavy bag only on one shoulder, without even thinking of how it could literally tip a person over.

So, maybe the bicycle is simply an extension of the balance methods already being used.
 

Offline Geezer

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Why do bicycles stay upright so well?
« Reply #3 on: 27/09/2011 22:24:36 »
It's because of a very subtle mechanism that causes the steering to adjust so that the bike returns to a vertical state as soon as it starts to fall over.

???

Are you talking about a learned compensation by the rider?  Or an intrinsic property of the bicycle.


It's an intrinsic property of the bicycle.

http://bicycle.tudelft.nl/schwab/Bicycle/index.htm

http://bicycle.tudelft.nl/stablebicycle/StableBicyclev34Revised.pdf

(BTW, the gyroscopic story is a myth.)

« Last Edit: 27/09/2011 22:27:01 by Geezer »
 

Offline Bored chemist

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Why do bicycles stay upright so well?
« Reply #4 on: 28/09/2011 06:51:08 »
If it is intrinsic to the bike, why do they fall over if they don't have a rider?
 

Offline Geezer

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Why do bicycles stay upright so well?
« Reply #5 on: 28/09/2011 07:39:01 »
If it is intrinsic to the bike, why do they fall over if they don't have a rider?


Because they slow down. The energy to provide the stabilizing feedback is a function of the velocity.
 

Offline CliffordK

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Why do bicycles stay upright so well?
« Reply #6 on: 28/09/2011 07:43:58 »
I suppose you could test the theory by rolling a bicycle down a hill without a rider...  and hopefully somewhere it would not go off course too much.  And, hopefully not crossing a busy street either.

However, you might compare it to just rolling the wheel down the hillside.  Rolling a narrow wheel like a bicycle wheel, the wheel will certainly stay upright much longer than just releasing a non-moving wheel.
 

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Why do bicycles stay upright so well?
« Reply #7 on: 28/09/2011 07:48:28 »
Y'all need to read the paper!
 

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Why do bicycles stay upright so well?
« Reply #7 on: 28/09/2011 07:48:28 »

 

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