My Experiment...

[[email protected]]

On Feb 28, 2:36 am, Martin Dann <[email protected]>
wrote:
>
> I think cats must do something similar with their legs, tail and
> possibly head.
>
Yup and also use air drag, same as skydivers.

However, my partners neighbours cat manages to specialize in falling
on it's back. Because of the steepness of the road there is a
retaining wall stopping her garden sliding into next doors (probably
about 2 feet tall). The cat likes to walk along the edge of the wall
when getting from one end of the garden to the other.

One day my partner had the sprinkler going and the cat was trying to
time it so that it didn't get wet. Twice it got it wrong, got sprayed
with water and fell off the wall onto it's back. It was hilarious,
especially watching the cat pretend nothing had happened.

> Of course the real question is how does toast always manage to land
> butter side down, as it does not have limbs or intelligence
>

Intelligent design ;-)

Because the EM force is so much stronger than the gravitational force
we have evolved to be the height we are (EM force giving strength to
chemical bonds in bones) and so have tables the height we do. Because
gravity is so weak something like toast sliding off a table gains just
enough rotation while it's part held up by the table and part falling
down that it does a half turn on it's way down.

Interesting PhD project for someone - vary the relative strengths of
EM and gravity, work out how tall "humans" would be and therefore how
tall their tables would be and so how universal a law "butter side
down" is across conceivable universes.

God was a practical joker!

Tim.

 

[Roger Thorpe]

Martin Dann wrote:

> Roger Thorpe wrote:
>
>> Fortunately nobody has mentioned the way dropped cats manage to turn
>> over in mid air.
>>
>> Ooops (puts hand to mouth)
>
>
> Imagine you are stood[1] in a space suit in space not rotating and not
> attached to anything else, and you want to turn "upside down"[2]. If you
> swing both arms in circles in the same direction parallel to your body,
> you will rotate the other way as long as your arms are moving. Once you
> stop swinging your arms, you body will stop rotating. [3]
>
> I think cats must do something similar with their legs, tail and
> possibly head.
>
> Of course the real question is how does toast always manage to land
> butter side down, as it does not have limbs or intelligence
>
>
> [1] or whatever the word is for zero gravity.
> [2] ditto
> [3] of course if this is your only method of turning, you are probably
> dead, even if you try and pull a David Bowman[4]
> [4] His h*lm*t saved his life because he took it off and threw it away
>
> Martin.
Oh blimey, you're right.
I had a much more complicated technique in mind. I was trying to be too
clever. I'm off lo look up 'hubris' in the dictionary.
Roger Thorpe

--
Roger Thorpe

My email address is spamtrapped. You can work it out!

 

[Dave Larrington]

In news:[email protected],
Martin Dann <[email protected]> tweaked the Babbage-Engine to
tell us:

> I think cats must do something similar with their legs, tail and
> possibly head.
>
> Of course the real question is how does toast always manage to land
> butter side down, as it does not have limbs or intelligence


With all this global warming bobbins in the news, you'd think someone would
be doing some serious research into harnessing the power generation
possibilities of buttered cats...

--
Dave Larrington
<http://www.legslarry.beerdrinkers.co.uk>
If you are choking on an ice cube, simply pour a jug of boiling
water down your throat and presto! The blockage is almost
instantly removed.

 

[dkahn400]

On 28 Feb, 10:12, "[email protected]" <[email protected]> wrote:

> Interesting PhD project for someone - vary the relative strengths of
> EM and gravity, work out how tall "humans" would be and therefore how
> tall their tables would be and so how universal a law "butter side
> down" is across conceivable universes.

I read about a statistician who was surprised to notice that whenever
his little daughter dropped the toast it landed butter side up.
Initially he thought he was just lucky but it was happening so
consistently it couldn't be due to chance. It was only when he stopped
doing the mental arithmetic and decided to investigate further that he
discovered she was buttering her toast on both sides.

--
Dave...

 

[AndyMorris]

Ben C wrote:
>
> I don't understand Jobst Brandt's theory for why countersteer is
> necessary, although he may be right. I don't see why you can't lean
> the
> bike over to initiate the turn just by shifting your centre of mass.
>

For the same reason you can't walk to the top of an unsupported ladder and
just balance on it. To balance on ladder you have to walk the bottom of it
underneath yourself.

--
Andy Morris

AndyAtJinkasDotFreeserve.Co.UK

Love this:
Put an end to Outlook Express's messy quotes
http://home.in.tum.de/~jain/software/oe-quotefix/



--
Posted via NewsDemon.com - Premium Uncensored Newsgroup Service
------->>>>>>http://www.NewsDemon.com<<<<<<------
Unlimited Access, Anonymous Accounts, Uncensored Broadband Access

 

[Ben C]

On 2007-03-01, AndyMorris <[email protected]> wrote:
> Ben C wrote:
>>
>> I don't understand Jobst Brandt's theory for why countersteer is
>> necessary, although he may be right. I don't see why you can't lean
>> the
>> bike over to initiate the turn just by shifting your centre of mass.
>>
>
> For the same reason you can't walk to the top of an unsupported ladder and
> just balance on it. To balance on ladder you have to walk the bottom of it
> underneath yourself.

Not true. Balancing on a ladder whose feet stay where they are is
possible, if difficult, and does not require any physical impossibility
like "pulling yourself up by your bootstraps".

Here is my earlier explanation (in this thread). Further down the thread
is a link to a video of a man balancing on a ladder.

http://groups.google.co.uk/group/uk.rec.cycling/msg/40e326853f0337c7?hl=en&

More interesting is the suggestion made that you'd somehow need a very
pronounced lean, bigger than what anyone ever does, in order to make a
turn. I'm still mulling over that one.

 

[Ben C]

On 2007-03-01, [email protected] <[email protected]> wrote:
[...]
> Yes, I agree that people who are not familiar with such elementary
> concepts may not be able to understand the issues. Anyone who insists
> that they can transport themselves sideways by dint of willpower
> without there being any external force acting on them is not going to
> be convinced by usenet debate

Was anyone insisting that?

> , although they can still be pushed in the direction of learning about
> it if they are prepared to try simple experiments (like riding a
> bicycle with locked steering) that refute their beliefs.

How would that experiment be used to refute the believe that an object
can be moved sideways with willpower and no external force?

It seems a bad choice of experiment, as there are external forces
readily accessible to the rider in that system. How would you be sure
he wasn't cheating and using them instead of willpower?

 

[[email protected]]

On Mar 1, 5:44 pm, Ben C <[email protected]> wrote:
> On 2007-03-01, [email protected] <[email protected]> wrote:
> [...]
>
> > Yes, I agree that people who are not familiar with such elementary
> > concepts may not be able to understand the issues. Anyone who insists
> > that they can transport themselves sideways by dint of willpower
> > without there being any external force acting on them is not going to
> > be convinced by usenet debate
>
> Was anyone insisting that?

I think you talked about "just shifting your centre of mass" just a
few posts ago.

>
> > , although they can still be pushed in the direction of learning about
> > it if they are prepared to try simple experiments (like riding a
> > bicycle with locked steering) that refute their beliefs.
>
> How would that experiment be used to refute the believe that an object
> can be moved sideways with willpower and no external force?
>
> It seems a bad choice of experiment, as there are external forces
> readily accessible to the rider in that system. How would you be sure
> he wasn't cheating and using them instead of willpower?

Readily accessible? Why haven't you dared try it yet then?

For a less painful version, just sit on your bicycle, and as you
topple off to one side, "just shift your centre of mass" to the other
side (while keeping hold of the bars and your feet on the pedals as in
normal riding) so you dismount the other way. You don't need to bother
to lock the steering so long as you promise not to to turn the bars
sharply (which will shift the bike under you due to the fork
geometry).

Assuming you can "just shift your mass" enough to make an appreciable
impact in normal riding, you should be able to wait until you are a
significant way off-balance before tipping yourself back up, and it
won't require any extreme contortions.

Perhaps you could make a video and put it on youtube.

James

 

[Mark Thompson]

> Assuming you can "just shift your mass" enough to make an appreciable
> impact in normal riding, you should be able to wait until you are a
> significant way off-balance before tipping yourself back up

Ride a normal bike, at 10-12mph or so, in a straight line. At no point are
you a significant way off-balance. The adjustments needed to keep balance
are very small - a matter of a few degrees turn of the wheel.

No, imagine that someone wishes to move the CofG of bike+rider relative to
the bike in order to initiate a turn. They can either countersteer, not
correct for something-or-other (road camber, wind, previous countersteer,
whatever) that has bike+rider shifting CofG in that direction anyway, or
they could shift it by moving themselves or the bike (but without turning
the wheels).

It is the last option that is under dispute. The CofG would need be moved
only a tiny amount before it became self-wossnaming, and the CofG moved far
enough to for the rider to turn the bars 'normally'[1] to carry out the
turn. Little control is needed - the rider merely has to do enough that it
goes one way and not the other.

The difficulty in measuring this is that countersteering is impossible not
to do unless you've nobbled the steering somehow (well, it's impossible for
me not to do).

So, to recap, the argument was whether it was possible to shift the CofG
far enough to turn, without the use of countersteer. My view is that it is,
but that we countersteer 'cos it's so much easier and pretty much
impossible not to (even if you do lean, you'll still be countersteering at
some point). However, shifting centre of gravity without countersteer?
Yeah, that can be done. <smiley> It's as easy as falling off </smiley>


[1] i.e. left to go left, right to go right.

 

[[email protected]]

On Mar 1, 8:53 pm, Mark Thompson
<pleasegivegenerously@warmmail*_turn_up_the_heat_to_reply*.com> wrote:
> > Assuming you can "just shift your mass" enough to make an appreciable
> > impact in normal riding, you should be able to wait until you are a
> > significant way off-balance before tipping yourself back up
>
> Ride a normal bike, at 10-12mph or so, in a straight line. At no point are
> you a significant way off-balance. The adjustments needed to keep balance
> are very small - a matter of a few degrees turn of the wheel.
>
> No, imagine that someone wishes to move the CofG of bike+rider relative to
> the bike in order to initiate a turn. They can either countersteer, not
> correct for something-or-other (road camber, wind, previous countersteer,
> whatever) that has bike+rider shifting CofG in that direction anyway, or
> they could shift it by moving themselves or the bike (but without turning
> the wheels).

Now try doing it at 25mph and making a sharp turn. It's not that hard
to work out how long it takes for a rider who's CoG is (say) initially
1cm off-centre, to fall through a 30 degree angle. It would also be
painfully obvious if anyone actually bothered the trivial test of
riding through a puddle at a decent speed on a dry road, followed by
taking a corner. Simon's off-centre photos with fat tyres on a beach
were a bit unclear but gave a pretty strong hint.

> So, to recap, the argument was whether it was possible to shift the CofG
> far enough to turn, without the use of countersteer.

No, Simon's claim was not that this was a theoretical possibility in
extremis (which I have repeatedly acknowledged might be possible) but
that it is the normal mode of steering not just for him but for most
cyclists, which doesn't pass the laugh test.

James

 

[Mark Thompson]

> that this was a theoretical possibility in
> extremis (which I have repeatedly acknowledged might be possible)

Bugger, so we agree with everything the other is saying? (well, you say
'might', I say 'is').

 

[Ben C]

On 2007-03-01, [email protected] <[email protected]> wrote:
> On Mar 1, 5:44 pm, Ben C <[email protected]> wrote:
>> On 2007-03-01, [email protected] <[email protected]> wrote:
>> [...]
>>
>> > Yes, I agree that people who are not familiar with such elementary
>> > concepts may not be able to understand the issues. Anyone who insists
>> > that they can transport themselves sideways by dint of willpower
>> > without there being any external force acting on them is not going to
>> > be convinced by usenet debate
>>
>> Was anyone insisting that?
>
> I think you talked about "just shifting your centre of mass" just a
> few posts ago.

And I thought you conceded that balancing on a ladder or a bike with
locked steering was possible if difficult, or perhaps it was someone
else.

We're talking about shifting the centre of mass of bike+rider relative
to where the tyres touch the ground. The bike+rider COM does not move
relative to the NRF, initially, although it does as the bike starts to
tip and frictional forces at the contacts oppose the torque on it.

No psychokinesis required.

>> > , although they can still be pushed in the direction of learning about
>> > it if they are prepared to try simple experiments (like riding a
>> > bicycle with locked steering) that refute their beliefs.
>>
>> How would that experiment be used to refute the believe that an object
>> can be moved sideways with willpower and no external force?
>>
>> It seems a bad choice of experiment, as there are external forces
>> readily accessible to the rider in that system. How would you be sure
>> he wasn't cheating and using them instead of willpower?
>
> Readily accessible? Why haven't you dared try it yet then?
>
> For a less painful version, just sit on your bicycle, and as you
> topple off to one side, "just shift your centre of mass" to the other
> side (while keeping hold of the bars and your feet on the pedals as in
> normal riding) so you dismount the other way. You don't need to bother
> to lock the steering so long as you promise not to to turn the bars
> sharply (which will shift the bike under you due to the fork
> geometry).

As I've said, I am no good at circus tricks. Balancing on a stationary
bicycle, especially one with locked steering, is not a skill required
for normal riding. But the fact that it is possible indicates that is
possible to initiate a turn by leaning. It does not follow however that
initiating a turn by leaning requires the skills of a circus clown.

> Assuming you can "just shift your mass" enough to make an appreciable
> impact in normal riding, you should be able to wait until you are a
> significant way off-balance before tipping yourself back up

I don't see how that conclusion follows from the premise.

 

[[email protected]]

On Mar 1, 10:40 pm, Ben C <[email protected]> wrote:
> On 2007-03-01, [email protected] <[email protected]> wrote:
>
> > On Mar 1, 5:44 pm, Ben C <[email protected]> wrote:
> >> On 2007-03-01, [email protected] <[email protected]> wrote:
> >> [...]
>
> >> > Yes, I agree that people who are not familiar with such elementary
> >> > concepts may not be able to understand the issues. Anyone who insists
> >> > that they can transport themselves sideways by dint of willpower
> >> > without there being any external force acting on them is not going to
> >> > be convinced by usenet debate
>
> >> Was anyone insisting that?
>
> > I think you talked about "just shifting your centre of mass" just a
> > few posts ago.
>
> And I thought you conceded that balancing on a ladder or a bike with
> locked steering was possible if difficult, or perhaps it was someone
> else.

Yes, my point is it is not a trick i would hand-wave away with "just",
and I'm sure that the vast majority of people cannot balance in such a
way.

> We're talking about shifting the centre of mass of bike+rider relative
> to where the tyres touch the ground. The bike+rider COM does not move
> relative to the NRF, initially,

So does it or doesn't it move? Is there a typo to explain the direct
contradiction in these two sentences?

> >> It seems a bad choice of experiment, as there are external forces
> >> readily accessible to the rider in that system. How would you be sure
> >> he wasn't cheating and using them instead of willpower?
>
> > Readily accessible? Why haven't you dared try it yet then?
>
> > For a less painful version, just sit on your bicycle, and as you
> > topple off to one side, "just shift your centre of mass" to the other
> > side (while keeping hold of the bars and your feet on the pedals as in
> > normal riding) so you dismount the other way. You don't need to bother
> > to lock the steering so long as you promise not to to turn the bars
> > sharply (which will shift the bike under you due to the fork
> > geometry).
>
> As I've said, I am no good at circus tricks.

But you just said that the external forces were "readily available".
How can they be both "readily available" and yet only accessible to
circus clowns?

To put the shoe on the other foot, since you are not prepared to try
the trivial experiments I have suggested (which certainly would show
that the possibility to "just shift your centre of mass sideways" is
extremely limited), can you suggest any experiment which would
actually demonstrate the existence of such an ability at a level which
might make a perceptible difference in bicycle riding?

James

 

[Ben C]

On 2007-03-02, [email protected] <[email protected]> wrote:
> On Mar 1, 10:40 pm, Ben C <[email protected]> wrote:
>> On 2007-03-01, [email protected] <[email protected]> wrote:
>>
>> > On Mar 1, 5:44 pm, Ben C <[email protected]> wrote:
[...]
>> We're talking about shifting the centre of mass of bike+rider relative
>> to where the tyres touch the ground. The bike+rider COM does not move
>> relative to the NRF, initially,
>
> So does it or doesn't it move? Is there a typo to explain the direct
> contradiction in these two sentences?

It's not a contradiction. If you're sitting in zero-gravity, you can
touch your toes. Your COM moves relative to your toes, but not relative
to the NRF.

A movement like that, not requiring any lateral forces from the NRF,
causes a torque to the bike+rider as soon as the weight becomes out of
line with the support points, making bike+rider begin to tip over.

As soon as it starts to tip, there is an external force at the contacts
which causes it to pivot around the contact rather than around its COM.
At this point the COM is moving relative to the NRF.

>> >> It seems a bad choice of experiment, as there are external forces
>> >> readily accessible to the rider in that system. How would you be sure
>> >> he wasn't cheating and using them instead of willpower?
>>
>> > Readily accessible? Why haven't you dared try it yet then?
>>
>> > For a less painful version, just sit on your bicycle, and as you
>> > topple off to one side, "just shift your centre of mass" to the other
>> > side (while keeping hold of the bars and your feet on the pedals as in
>> > normal riding) so you dismount the other way. You don't need to bother
>> > to lock the steering so long as you promise not to to turn the bars
>> > sharply (which will shift the bike under you due to the fork
>> > geometry).
>>
>> As I've said, I am no good at circus tricks.
>
> But you just said that the external forces were "readily available".
> How can they be both "readily available" and yet only accessible to
> circus clowns?

Accessible to everyone, but it takes a clown to control them.

> To put the shoe on the other foot, since you are not prepared to try
> the trivial experiments I have suggested (which certainly would show
> that the possibility to "just shift your centre of mass sideways" is
> extremely limited), can you suggest any experiment which would
> actually demonstrate the existence of such an ability at a level which
> might make a perceptible difference in bicycle riding?

As I said earlier, leaning into a corner does not require clown ability.
Clowns enter the discussion only to illuminate the descriptions of why
it is possible to lean over without needing psychokinesis. We use the
same physics as the clowns, but not the same skill. They use this effect
to balance on things, I'm only suggesting that cyclists may use it to
initiate turns.

 

[[email protected]]

On Mar 2, 5:24 pm, Ben C <[email protected]> wrote:
> On 2007-03-02, [email protected] <[email protected]> wrote:
>
> > On Mar 1, 10:40 pm, Ben C <[email protected]> wrote:
> >> On 2007-03-01, [email protected] <[email protected]> wrote:
>
> >> > On Mar 1, 5:44 pm, Ben C <[email protected]> wrote:
> [...]
> >> We're talking about shifting the centre of mass of bike+rider relative
> >> to where the tyres touch the ground. The bike+rider COM does not move
> >> relative to the NRF, initially,
>
> > So does it or doesn't it move? Is there a typo to explain the direct
> > contradiction in these two sentences?
>
> It's not a contradiction. If you're sitting in zero-gravity, you can
> touch your toes. Your COM moves relative to your toes, but not relative
> to the NRF.

Yes, the toes can move relative to the NRF. Are you claiming that the
contact patch does? If so, how, other than by steering?

>
> A movement like that, not requiring any lateral forces from the NRF,

What sort of (lateral) movement is it that requires no lateral force?

> > To put the shoe on the other foot, since you are not prepared to try
> > the trivial experiments I have suggested (which certainly would show
> > that the possibility to "just shift your centre of mass sideways" is
> > extremely limited), can you suggest any experiment which would
> > actually demonstrate the existence of such an ability at a level which
> > might make a perceptible difference in bicycle riding?
>
> As I said earlier, leaning into a corner does not require clown ability.
> Clowns enter the discussion only to illuminate the descriptions of why
> it is possible to lean over without needing psychokinesis. We use the
> same physics as the clowns, but not the same skill. They use this effect
> to balance on things, I'm only suggesting that cyclists may use it to
> initiate turns.

To put the shoe on the other foot, since you are not prepared to try
the trivial experiments I have suggested (which certainly would show
that the possibility to "just shift your centre of mass sideways" is
extremely limited), can you suggest any experiment which would
actually demonstrate the existence of such an ability at a level which
might make a perceptible difference in bicycle riding?

James

 

[Mark Thompson]

> can you suggest any experiment which would
> actually demonstrate the existence of such an ability at a level which
> might make a perceptible difference in bicycle riding?

Sit astride bike. Remove pressure from seat (i.e. take your weight on the
pedals) and tilt bike to the side. Then move body the same way. Centre of
gravity has moved so much that you fall off quite quickly.

 

[dkahn400]

On 2 Mar, 11:17, Mark Thompson
<pleasegivegenerously@warmmail*_turn_up_the_heat_to_reply*.com> wrote:
> > can you suggest any experiment which would
> > actually demonstrate the existence of such an ability at a level which
> > might make a perceptible difference in bicycle riding?
>
> Sit astride bike. Remove pressure from seat (i.e. take your weight on the
> pedals) and tilt bike to the side. Then move body the same way. Centre of
> gravity has moved so much that you fall off quite quickly.

To make it meaningful the steering would have to be locked straight.
On such a bike it is virtually impossible to remain balanced long
enough to perform this experiment. You always tip one way or the other
because of the egg-balanced-on-the-little-end effect. It's obvious you
still haven't experimented with locking your bike's steering.

It also seems you don't have an appreciation of the laws of motion.
You seem to think the rider could move the bike without a reaction
moving his body the other way, and then somehow move his body towards
the bike without the reaction pulling the bike upright again.

Also note that in normal bike riding with hands on the bars the rider
does not tilt the bike and his body in opposite directions. A smooth
turn is made with the rider's body and the bike remaining in the same
plane.

--
Dave...

 

[Mark Thompson]

> To make it meaningful the steering would have to be locked straight.

I've just nicked a mates unused heap of junk. What do I do to the headset
to lock the steering? I think it's a threaded headset, and I have a
headset spannery-thing.

> Also note that in normal bike riding with hands on the bars the rider
> does not tilt the bike and his body in opposite directions. A smooth
> turn is made with the rider's body and the bike remaining in the same
> plane.

I've already said that in normal riding we use countersteer to move the
centre of gravity. I merely think that it's possible to move the CofG
without having to resort to countersteer.

 

[[email protected]]

On Mar 2, 12:40 pm, Mark Thompson
<pleasegivegenerously@warmmail*_turn_up_the_heat_to_reply*.com> wrote:
> > To make it meaningful the steering would have to be locked straight.
>
> I've just nicked a mates unused heap of junk. What do I do to the headset
> to lock the steering? I think it's a threaded headset, and I have a
> headset spannery-thing.
>
> > Also note that in normal bike riding with hands on the bars the rider
> > does not tilt the bike and his body in opposite directions. A smooth
> > turn is made with the rider's body and the bike remaining in the same
> > plane.
>
> I've already said that in normal riding we use countersteer to move the
> centre of gravity. I merely think that it's possible to move the CofG
> without having to resort to countersteer.

Disregarding air resistance there is only the friction against the
ground that can move the CoG

So if you lean the bike to the left the COG will (slightly) move to
the right. Leaning the bike to the left will also move the contact
patch to the left.

The net effect being that if you lean the bike to the left you will
fall off to the right assuming you started balanced.

Tim.

 

[dkahn400]

On 2 Mar, 12:40, Mark Thompson
<pleasegivegenerously@warmmail*_turn_up_the_heat_to_reply*.com> wrote:
> > To make it meaningful the steering would have to be locked straight.
>
> I've just nicked a mates unused heap of junk. What do I do to the headset
> to lock the steering? I think it's a threaded headset, and I have a
> headset spannery-thing.

Use a thin headset spanner to hold the threaded race (immediately
below the locknut) and loosen the locknut. Tighten the threaded race
until the steering is solid then tighten the locknut down onto it
without backing off the threaded race.

The locknut may be very hard to start moving so be careful not to
injure yourself if it moves suddenly or if the spanner slips. Ideally
you should use a thicker spanner for the locknut. Once you've locked
the steering take care on the bike as it will be impossible to
ride.

Have fun!

--
Dave...