The physics behind rail riding and stillstanding?

Some of us Australian trials and muni riders are putting together a
combined movie project that we plan to sell and that we hope will raise
awareness, etc of unicycling in Australia. As well as my sectin of the
movie, I'm making a rail riding tutorial to fit into an extras menu and
I want it to be useful and to make sence...

...so I'd really like to know a little about the physics of rail riding.
When I'm riding a rail, if I'm falling to the right then I'll throw my
arms and upper body to the right to somehow regain my balance. Could
somebody please tell me what's going on here? Being higher above the
ground, and often heavier, I would have thought that the upper body
would pull the rider even further off balance if it was moved in the
direction he/she was falling. Or is it that when the rider moves their
upper body to the right, they are pushing their lower body to the left,
and keeping their weight over the rail?

Also, I've sometimes found myself swinging one arm in circles in a final
attempt to regain balance, and sometimes it's worked. Actually, I just
looked at a video of a rail I rode once and it's sometimes more of a
push of the arm from the back to the front. In the case I just observed
I was falling to the right and I did this action with my right arm to
regain balance. Can someone please explain this?

And one last thing, is the forward momentum doing anything to keep the
rider upright? Should narrow rail riding (with no lateral wheel
movement) be any easier than stillstanding?

I've attached some frames fro ma video to try to explain the actions I'm
referring to.

Thanks a lot. I'm sure I could attempt to analyse these goings-on
myself but I'd rather hear even the basic stuff from somebody who knows
what they're talking about.

Thanks,
Andrew


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I'm not particularly good at riding rails, but from the physics point of
view the idea of swinging the arms is that the reaction from your arms
swinging moves your weight in the opposite direction, in the same way
that you can do sharp turns y swinging your amrs around you, just in a
different axis.
I think its also important that the arms are aove your head, which means
they are further away from the pivot (the bottom of the tyre) so the
force from swinging your arms produces enough of a moment (turning
force) to regain your balance without moving your cnetre of gravity even
further over to the point that you fall anyway.
I suppose that technically with no lateral movement a rail should be the
same as a still stand, but with most rails the thickness of the tyre
might mean you can move a little to regain balance. From the pictures
you can probably answer that better than me.

Hope that helps,

John


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Yes, that was helpful, thanks John. I think that with rails that size
and smaller any lateral wheel movement is unintentional for me.

Keep the explanations coming!

Andrew


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Hi Andrew,

Sounds like a neat project. I don't have much time now but I'll give it
some thought and post later. One of the stillstanding threads had a
good discussion of what is going on. You're on the right track with
your hunches. (Oh - sorry about the double pun... )

Tim


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When you throw your upper body to the right, it throws your lower body
(including the wheel) to the left.


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Conservation of momentum: Your total momentmum must be the same at all
times in the left right direction, so if you give your arms momentum to
the left, then the rest of you must go to the right to 'cancel' the
momentum to the left.

Same concept as throwing something heavy when you're standing on really
slippery ice: the thing you threw goes one way (Like your arms) and you
go the other way (Like your torso and uni).


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Aah, one of Newton's big scary laws:
every action has an equal and an opposite reaction.
(that's my thinking done for the day)


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Okay thanks, but how about these ones...

"Also, I've sometimes found myself swinging one arm in circles in a
final attempt to regain balance, and sometimes it's worked. Actually, I
just looked at a video of a rail I rode once and it's sometimes more of
a push of the arm from the back to the front. In the case I just
observed I was falling to the right and I did this action with my right
arm to regain balance. Can someone please explain this?"

"And one last thing, is the forward momentum doing anything to keep the
rider upright?"

And I noticed that the guy (in the Moab section) riding that brown rail
seems to prefer to keep his upper body very low. This seems strange to
me.

I found a good clip yesterday to add to the tutorial. It's just me
stillstanding on a wooden rail but you can see clearly how I'm trying to
push my hips to the side by moving my upper body to the other side.

Andrew


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andrew_carter wrote:
*Should narrow rail riding (with no lateral wheel movement) be any
easier than stillstanding?*
Of course. In a stillstand you are not allowed the freedom to roll
forward and back. The rolling also allows you to make some left-right
corrections with slight changes in your line.

There is the whole Newton's law and conservation of energy/momentum
issue, but this doesn't explain how a Kris Holm can spend 3 minutes
stillstanding on a piece of railroad track. Clearly he was doing
something the rest of us were not.

Add *time* to the physics info from above. I believe that is a factor.
Also if you make your body movements in a wave, that kind of gets wider
as it goes up. Those are two brief descriptions of how I think you get
around the normal laws of physics to balance where common sense says you
can't.


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Did i read that right? THREE MINUTES? is there a special technique for
stillstands?


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TheBadger587 - Level 4

Well i Guess not the retarded ones... but how could you even say
something like that? jeez cleveland, there's edgy and then theres
offensive. Good day sir!
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