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"The Stability of the Bicycle"



 
 
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  #41  
Old October 7th 03, 06:21 PM
David Damerell
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wrote:
Simon Brooke writes:
Well, just so. I agree that you can get strong gyroscopic effects
with a fast rotating wheel, but I'm completely unpersuaded that they
are significant at walking speed. So, again, has anyone done the
maths?

There are no "maths", math is an aggregate concept and has no plural...
except in GB maybe.


Simon is using British English correctly. "math" is not a word in the UK.
--
David Damerell Kill the tomato!
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  #42  
Old October 7th 03, 07:12 PM
jim beam
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yes or no: does a gyro react at 90 degress to an applied force or not?

  #43  
Old October 7th 03, 09:40 PM
Tim McNamara
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In article ,
jim beam wrote:

yes or no: does a gyro react at 90 degress to an applied force or
not?


An applied force along which axis?
  #44  
Old October 7th 03, 09:54 PM
brent
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I'm confused, but here's my train of thought. No one has mentioned
riding the rollers.
-One potentially illuminating experiment is riding the rollers with no
hands and a (too) tight headset.

But, riding the rollers with no hands.... The faster I go the easier
it is to stay upright. colloquially, I would say that I remain upright
due to the gyroscopic mumbo-jumbo of the wheels and that I remain
centered on the rollers by moving my weight to one side or the other
(knowing that my bike will follow). With no hands, is my movement back
to the center of the rollers be preceded by counter-steering by making
the front wheel "flop" on way or another with some hip motion? I'm not
sure.
..an obvious but unmentioned observation: at very low speeds on the
rollers, steering occurs more via turning the bars and less via
leaning--counter to the example of walking a bike with the hand on the
saddle. (the reason for this is clear but how either of these extremes
relate to the actual riding of a bike on the road is less clear to
me).

Finally, I think there's something to think about with riding the
rollers on a bike with wheels that have twice the rotational mass.
Easier or harder to: 1)stay upright and 2)stay centered on the
rollers. I'm not sure.
  #45  
Old October 7th 03, 10:47 PM
Benjamin Lewis
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jim beam wrote:

as Jobst has
claimed.


that's proof?


Proof of what? What are you talking about?

You appear to be inventing straw men to knock down. Why don't have a look
at what Jobst's actual position is:

http://draco.acs.uci.edu/rbfaq/FAQ/9.35.html

--
Benjamin Lewis

Seeing is deceiving. It's eating that's believing.
-- James Thurber
  #46  
Old October 7th 03, 11:14 PM
Ian
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wrote:

Simon Brooke writes:


Take the wheel out, spin it in you hands and try to tilt it to
the left or right and note the force of the steering action.
This should convince you of its effect.



please explain. gyro reaction is _90 degrees to the applied
force_. i.e. my front wheel, spinning "forwards" tries to tilt top
rightwards when turned to the left. you seem to be implying that
gyro recation is responsible for banking the bike to the left when
steered left.



No, when you wheel the bike along holding onto the seat you steer
by banking the bike and the turn is a reaction to the bank.
Banking the bike to the left will tend to initiate a turn to the
left. But the gyroscopic force is quite small when the wheel is
spun at only walking speed and the geometry of the bike also
results in the wheel turning left in response to a left bank (even
when the wheel isn't rotating).



Well, just so. I agree that you can get strong gyroscopic effects
with a fast rotating wheel, but I'm completely unpersuaded that they
are significant at walking speed. So, again, has anyone done the
maths?



There are no "maths", math is an aggregate concept and has no plural...
except in GB maybe.

I guess you don't have a bicycle with a QR front wheel so you can't
perform the simple experiment of turning the wheel at "walking speed"
to fell the strong gyroscopic effect caused by tilting the wheel
manually to the left and right.

Jobst Brandt

Sorry Jobst - we don't have "math" downunder either, we have "maths" as
in Pure Maths, Applied Maths. "math" is an Americanism.

Ian
:-)

  #47  
Old October 8th 03, 01:42 AM
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Default "The Stability of the Bicycle"

Ian L? writes:

There are no "maths", math is an aggregate concept and has no
plural... except in GB maybe.


I guess you don't have a bicycle with a QR front wheel so you can't
perform the simple experiment of turning the wheel at "walking
speed" to fell the strong gyroscopic effect caused by tilting the
wheel manually to the left and right.


Sorry Jobst - we don't have "math" downunder either, we have "maths"
as in Pure Maths, Applied Maths. "math" is an Americanism.


That's fine. Only one with a stiff upper lip would create such an
abbreviation that defies pronunciation. I suppose as long as it
remains on the KBD it doesn't tangle the tongue. The essence of a
lisp is the mix of 'th" and 's'. To make 'maths' from 'mathematics'
is an excessive linguistic rigourosity. I see we are more fortunate
in the USA with a bit of realism and where we do our 'math' without
linguistic twisting of the tongue.

Jobst Brandt




  #48  
Old October 8th 03, 02:34 AM
Phil Holman
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"Simon Brooke" wrote in message
. uk...
Peter writes:

jim beam wrote:

Take the wheel out, spin it in you hands and try to tilt it to

the
left or right and note the force of the steering action. This

should
convince you of its effect.
please explain. gyro reaction is _90 degrees to the applied
force_. i.e. my front wheel, spinning "forwards" tries to tilt top
rightwards when turned to the left. you seem to be implying that
gyro recation is responsible for banking the bike to the left when
steered left.


No, when you wheel the bike along holding onto the seat you steer by
banking the bike and the turn is a reaction to the bank. Banking

the
bike to the left will tend to initiate a turn to the left. But the
gyroscopic force is quite small when the wheel is spun at only

walking
speed and the geometry of the bike also results in the wheel turning
left in response to a left bank (even when the wheel isn't
rotating).


Well, just so. I agree that you can get strong gyroscopic effects with
a fast rotating wheel, but I'm completely unpersuaded that they are
significant at walking speed. So, again, has anyone done the maths?


http://scienceworld.wolfram.com/phys...recession.html

Phil Holman


  #50  
Old October 8th 03, 09:35 AM
Simon Brooke
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Default "The Stability of the Bicycle"

David Damerell writes:

"jim beam" wrote:
Benjamin Lewis:
"jim beam"
as Jobst has claimed.

that's proof?


There's a neat piece of selective quoting. What this should read is;

old high school physics footage of a bike being ridden with a counter
gyroscopic wheelset. works just fine.
And is reportedly "almost impossible" to ride no-hands, as Jobst has
claimed.


I.e., the behaviour of this bike substantiates Jobst's claim.


With respect, that behaviour of a counter-gyroscopic bike is reported
in Jobst's claim. Thus it can't either substantiate or refute it. What
could substantiate or refute it is an independent report from someone
who had either seen the film (in which case they could confirm what
was said on the film) or had ridden the bike (in which case they
could confirm the behaviour of the bike).

Actually, this report
URL: http://www.geocities.com/CollegePark...32/pyfair.html
contradicts Jobst. It says that

'He reversed the front fork to nullify the caster action, and he
fitted a counter-rotating wheel on the front fork to effectively
nullify or cancel out the gyroscopic effects. When he was finished,
he still found that the bicycle could still be balanced and steered
quite easily... These experiments effectively disproved the
hypothesis that gyroscopic motion was the primary force responsible
for balance in a bicycle...'

Now, I have no way immediately of assessing whether Jobst's claim or
the report given above should be given more credence. But lean steer
works for a number of other 'vehicles' which have no gyroscopic
effects. Snowboarders manage just fine no hands, as do
surfers. Furthermore, on both these platforms control increases with
speed. Thus gyroscopic effects are not _required_ to account for the
ability to ride a bike no hands.

--
(Simon Brooke) http://www.jasmine.org.uk/~simon/

;; how did we conclude that a ****ing cartoon mouse is deserving
;; of 90+ years of protection, but a cure for cancer, only 14?
-- user 'Tackhead', in /. discussion of copyright law, 22/05/02
 




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