The physics of a riderless bike

[RicodJour[_2_]]

Nice video.
http://www.sciencefriday.com/videos/watch/10376

Oh, and please note the guy pushing the bike wasn't wearing a
helmet. ;)

R

[Hermichut]

On Oct 19, 6:05*am, RicodJour > wrote:
> Nice video.http://www.sciencefriday.com/videos/watch/10376
>
> Oh, and please note the guy pushing the bike wasn't wearing a
> helmet. *;)
>
> R

They have extended their experiments to the race arena...

http://www.break.com/index/bike-finishes-race-without-rider.html#

This time the tester was wearing suitable safety protection for such
an experiment....

h.

[ilan[_2_]]

On Oct 19, 1:08*pm, Hermichut > wrote:
> On Oct 19, 6:05*am, RicodJour > wrote:
>
> > Nice video.http://www.sciencefriday.com/videos/watch/10376
>
> > Oh, and please note the guy pushing the bike wasn't wearing a
> > helmet. *;)
>
> > R
>
> They have extended their experiments to the race arena...
>
> http://www.break.com/index/bike-finishes-race-without-rider.html#
>
> This time the tester was wearing suitable safety protection for such
> an experiment....
>
> h.

Milan San Remo 1997, Jalabert finished about 10 places behind his bike
http://www.youtube.com/watch?v=eOkgbZ6kJeo&feature=related

-ilan

[ilan[_2_]]

On Oct 19, 6:05*am, RicodJour > wrote:
> Nice video.http://www.sciencefriday.com/videos/watch/10376
>
> Oh, and please note the guy pushing the bike wasn't wearing a
> helmet. *;)
>
> R

The fact that gyroscopic action isn't as important has been known for
at least 30 years. Some university professor in the US has been
building bike with the same double wheels to cancel rotational inertia
for decades.

The problem with modelisation of the bicycle is that it is a non
holonomic system. If I remember correctly, the point is that the
wheels turn due to friction of the ground, and that pretty much ruins
any chance of a straightforward solution.

-ilan

[Fredmaster of Brainerd]

On Oct 19, 10:00*am, ilan > wrote:
> On Oct 19, 6:05*am, RicodJour > wrote:
>
> > Nice video.http://www.sciencefriday.com/videos/watch/10376
>
> > Oh, and please note the guy pushing the bike wasn't wearing a
> > helmet. *;)
>
> > R
>
> The fact that gyroscopic action isn't as important has been known for
> at least 30 years. Some university professor in the US has been
> building bike with the same double wheels to cancel rotational inertia
> for decades.
>
> The problem with modelisation of the bicycle is that it is a non
> holonomic system. If I remember correctly, the point is that the
> wheels turn due to friction of the ground, and that pretty much ruins
> any chance of a straightforward solution.
>

"modelisation" => ENGLISH PLEASE.
You've been in Euroland too long - I only ever see this word
in papers when the authors are mentally translating from
another language (one where it is a word).

The bicycle problem is not just friction, but its degrees of
freedom. For example, a cylinder rolling on a plane (flat
or inclined) is holonomic, I believe, but a sphere rolling
on a plane is not holonomic - it can take more than one
path to end up at the same coordinates.

Fredmaster Ben

[Frederick the Great]

In article
>,
ilan > wrote:

> On Oct 19, 6:05Â*am, RicodJour > wrote:
> > Nice video.http://www.sciencefriday.com/videos/watch/10376
> >
> > Oh, and please note the guy pushing the bike wasn't wearing a
> > helmet. Â*;)
>
> The fact that gyroscopic action isn't as important has been known for
> at least 30 years. Some university professor in the US has been
> building bike with the same double wheels to cancel rotational inertia
> for decades.
>
> The problem with modelisation of the bicycle is that it is a non
> holonomic system. If I remember correctly, the point is that the
> wheels turn due to friction of the ground, and that pretty much ruins
> any chance of a straightforward solution.

Some guys at Delft did some calculations and
built a bicycle that exhibits bicycle self-stability
without gyroscopic wheel effects.
<http://bicycle.tudelft.nl/stablebicycle/>
The videos are eye opening.

--
Old Fritz

[atriage[_6_]]

On 19/10/2011 18:27, Fredmaster of Brainerd wrote:
> On Oct 19, 10:00 am, > wrote:
>> On Oct 19, 6:05 am, > wrote:
>>
>>> Nice video.http://www.sciencefriday.com/videos/watch/10376
>>
>>> Oh, and please note the guy pushing the bike wasn't wearing a
>>> helmet. ;)
>>
>>> R
>>
>> The fact that gyroscopic action isn't as important has been known for
>> at least 30 years. Some university professor in the US has been
>> building bike with the same double wheels to cancel rotational inertia
>> for decades.
>>
>> The problem with modelisation of the bicycle is that it is a non
>> holonomic system. If I remember correctly, the point is that the
>> wheels turn due to friction of the ground, and that pretty much ruins
>> any chance of a straightforward solution.
>>
>
> "modelisation" => ENGLISH PLEASE.
> You've been in Euroland too long - I only ever see this word
> in papers when the authors are mentally translating from
> another language (one where it is a word).
>
> The bicycle problem is not just friction, but its degrees of
> freedom. For example, a cylinder rolling on a plane (flat
> or inclined) is holonomic, I believe, but a sphere rolling
> on a plane is not holonomic - it can take more than one
> path to end up at the same coordinates.
>

Sheesh, when I found this group I thought it was gonna be full of cycling nerds,
anyway, Mach's Principal states more or less that local physical laws are
determined by the large-scale structure of the universe, which I think is
blindingly obvious without in any way being smart enough to 'nail it down'. So
from a bicycle moving POV it's a motion relative to the distant stars kinda
thing which might make the modelisation <retches> of our daily ride harder than
anyone might of thought. Anyway that's the blue sky picture, Wiki offers this
http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_dynamics
Warning...contains geometry and differential equations.

--

[Frederick the Great]

In article
>,
Fredmaster of Brainerd > wrote:

> On Oct 19, 10:00Â*am, ilan > wrote:
> > On Oct 19, 6:05Â*am, RicodJour > wrote:
> >
> > > Nice video.http://www.sciencefriday.com/videos/watch/10376
> >
> > > Oh, and please note the guy pushing the bike wasn't wearing a
> > > helmet. Â*;)
> >
> > > R
> >
> > The fact that gyroscopic action isn't as important has been known for
> > at least 30 years. Some university professor in the US has been
> > building bike with the same double wheels to cancel rotational inertia
> > for decades.
> >
> > The problem with modelisation of the bicycle is that it is a non
> > holonomic system. If I remember correctly, the point is that the
> > wheels turn due to friction of the ground, and that pretty much ruins
> > any chance of a straightforward solution.
> >
>
> "modelisation" => ENGLISH PLEASE.
> You've been in Euroland too long - I only ever see this word
> in papers when the authors are mentally translating from
> another language (one where it is a word).
>
> The bicycle problem is not just friction, but its degrees of
> freedom. For example, a cylinder rolling on a plane (flat
> or inclined) is holonomic, I believe, but a sphere rolling
> on a plane is not holonomic - it can take more than one
> path to end up at the same coordinates.

A holonomic constraint can be integrated out separately;
but a non-holonomic constraint cannot. Other examples of
NHC's are inequalities. A particle moving on a sphere is
a HC. A particle that can fall off a sphere is a NHC. A
NHC can only be solved for only by solving the entire problem.

A sphere on a plane

V velocity of the center of mass (vector quantity)
w angular velocity of the sphere (vector quantity, sort of)
n unit normal to the plane at the point of contact (vector quantity)
a radius of the sphere (scalar quantity)

The constraint that the sphere does not slip is expressed as

V - a(w x n) = 0.

If the the point of contact describes a circle on the plane
then it becomes a holonomic constraint.

--
Old Fritz

[thirty-six]

On Oct 19, 6:00*pm, ilan > wrote:
> On Oct 19, 6:05*am, RicodJour > wrote:
>
> > Nice video.http://www.sciencefriday.com/videos/watch/10376
>
> > Oh, and please note the guy pushing the bike wasn't wearing a
> > helmet. *;)
>
> > R
>
> The fact that gyroscopic action isn't as important has been known for

It certainly assists in directional stability at anything over 40mph.
This is more important when the front tyre contact patch is short,
typified by using a narrow HP tyre inflated super hard. Not that I
would ride a bike in such a condition, any more.

> at least 30 years. Some university professor in the US has been
> building bike with the same double wheels to cancel rotational inertia
> for decades.
>
> The problem with modelisation of the bicycle is that it is a non
> holonomic system. If I remember correctly, the point is that the
> wheels turn due to friction of the ground, and that pretty much ruins
> any chance of a straightforward solution.
>
> -ilan

[Simply Fred]

Fredmaster of Brainerd wrote:
> The bicycle problem is not just friction, but its degrees of
> freedom. For example, a cylinder rolling on a plane (flat
> or inclined) is holonomic, I believe, but a sphere rolling
> on a plane is not holonomic - it can take more than one
> path to end up at the same coordinates.

That should make you extra grateful SOTS provides you with an afternoon
training ride grant.

[atriage[_6_]]

On 19/10/2011 21:21, atriage wrote:
> On 19/10/2011 18:27, Fredmaster of Brainerd wrote:
>> On Oct 19, 10:00 am, > wrote:
>>> On Oct 19, 6:05 am, > wrote:
>>>
>>>> Nice video.http://www.sciencefriday.com/videos/watch/10376
>>>
>>>> Oh, and please note the guy pushing the bike wasn't wearing a
>>>> helmet. ;)
>>>
>>>> R
>>>
>>> The fact that gyroscopic action isn't as important has been known for
>>> at least 30 years. Some university professor in the US has been
>>> building bike with the same double wheels to cancel rotational inertia
>>> for decades.
>>>
>>> The problem with modelisation of the bicycle is that it is a non
>>> holonomic system. If I remember correctly, the point is that the
>>> wheels turn due to friction of the ground, and that pretty much ruins
>>> any chance of a straightforward solution.
>>>
>>
>> "modelisation" => ENGLISH PLEASE.
>> You've been in Euroland too long - I only ever see this word
>> in papers when the authors are mentally translating from
>> another language (one where it is a word).
>>
>> The bicycle problem is not just friction, but its degrees of
>> freedom. For example, a cylinder rolling on a plane (flat
>> or inclined) is holonomic, I believe, but a sphere rolling
>> on a plane is not holonomic - it can take more than one
>> path to end up at the same coordinates.
>>
>
> Sheesh, when I found this group I thought it was gonna be full of cycling nerds,
> anyway, Mach's Principal states more or less that local physical laws are
> determined by the large-scale structure of the universe, which I think is
> blindingly obvious without in any way being smart enough to 'nail it down'. So
> from a bicycle moving POV it's a motion relative to the distant stars kinda
> thing which might make the modelisation <retches> of our daily ride harder than
> anyone might of thought. Anyway that's the blue sky picture, Wiki offers this
> http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_dynamics
> Warning...contains geometry and differential equations.
>
Usefully these guys have made it possible to calculate the circumference of a
wheel down to the Planck length which should improve bicycle maths...I can think
of no other possible use for it anyway.
http://www.newscientist.com/blogs/shortsharpscience/2011/10/pi-10-trillion.html
--

[Fred Flintstein]

On 10/19/2011 3:35 PM, Frederick the Great wrote:
> A holonomic constraint can be integrated out separately;
> but a non-holonomic constraint cannot. Other examples of
> NHC's are inequalities. A particle moving on a sphere is
> a HC. A particle that can fall off a sphere is a NHC. A
> NHC can only be solved for only by solving the entire problem.
>
> A sphere on a plane
>
> V velocity of the center of mass (vector quantity)
> w angular velocity of the sphere (vector quantity, sort of)
> n unit normal to the plane at the point of contact (vector quantity)
> a radius of the sphere (scalar quantity)
>
> The constraint that the sphere does not slip is expressed as
>
> V - a(w x n) = 0.
>
> If the the point of contact describes a circle on the plane
> then it becomes a holonomic constraint.
>

If you could code that in perl you'd be close to understanding
Lafferty. Except he's pretty unstable, check the source code
for details. Mostly that's because solving the problem isn't
the point for the Laff-bot.

F

[DougC]

On 10/18/2011 11:05 PM, RicodJour wrote:
> Nice video.
> http://www.sciencefriday.com/videos/watch/10376
>
> Oh, and please note the guy pushing the bike wasn't wearing a
> helmet. ;)
>
> R

So then, is it demonstrating the physics of a rider-less bike?,,, -or a
helmet-less bike?

[Fredmaster of Brainerd]

On Oct 19, 2:44*pm, Fred Flintstein >
wrote:
> On 10/19/2011 3:35 PM, Frederick the Great wrote:
>
>
>
>
>
>
>
>
>
> > A holonomic constraint can be integrated out separately;
> > but a non-holonomic constraint cannot. Other examples of
> > NHC's are inequalities. A particle moving on a sphere is
> > a HC. A particle that can fall off a sphere is a NHC. A
> > NHC can only be solved for only by solving the entire problem.
>
> > A sphere on a plane
>
> > V * * * * * *velocity of the center of mass (vector quantity)
> > w * * * * * *angular velocity of the sphere (vector quantity, sort of)
> > n * * * * * *unit normal to the plane at the point of contact (vector quantity)
> > a * * * * * *radius of the sphere (scalar quantity)
>
> > The constraint that the sphere does not slip is expressed as
>
> > * * * *V - a(w x n) = 0.
>
> > If the the point of contact describes a circle on the plane
> > then it becomes a holonomic constraint.
>
> If you could code that in perl you'd be close to understanding
> Lafferty. Except he's pretty unstable, check the source code
> for details. Mostly that's because solving the problem isn't
> the point for the Laff-bot.
>
> F

On the contrary, Lafferty is completely stable - overly so.
He has settled into a local minimum of the potential
(actually I think of it as a local minimum of the probability
surface, like a fitting method getting stuck) and shall not
be moved. No amount of added evidence will change
his likelihood.

Fredmetropolisalgorithm Ben

[Simply Fred]

Fredmaster of Brainerd wrote:
> On the contrary, Lafferty is completely stable - overly so.
> He has settled into a local minimum of the potential
> (actually I think of it as a local minimum of the probability
> surface, like a fitting method getting stuck) and shall not
> be moved. No amount of added evidence will change
> his likelihood.

A Hamiltonian cycle then (probably a fixed gear single speed one).