Flat Light Goggles

On Thu, 20 Nov 2003 15:35:05 GMT, Simon Brooke
wrote:


Riding a bicycle is all about letting go. When you sit on a bicycle
with your hands on the handlebars it looks as if you steer with your
hands, but (except at very low speeds) you not only don't, you
mustn't. Above a certain speed (which varies according to the geometry
of the bike) the bicycle is dynamically stable if you don't mess with
it too much, and is steered by small and subtle shifts of balance.

Wrong. Most steering at higher speeds _is_ done through the 'bars,
just in the opposite direction to what you'd expect. This is known as
counter-steering, and is a well-known phenomenon, particularly amongst
motorcyclists.

There are two effects at work,

1. the steering geometry of the bike causes it to 'fall' in the
opposite direction to that the bars are moved in, and it's inherent
stability will then cause the wheel to move back in the right
direction.
2. The gyroscopic effect, whereby pressure on a revolving object will
always cause it to move in a 90deg plane to that in which the force is
applied. So by pushing forward with one handlebar it will again fall
towards the side that was pushed forwards.

--
Ace (bruce dot rogers at roche dot com)
Ski Club of Great Britain - http://www.skiclub.co.uk
All opinions expressed are personal and in no way represent those of the Ski Club.

On Thu, 20 Nov 2003 17:02:39 +0100, Ace wrote:

There are two effects at work,
[...]
2. The gyroscopic effect, whereby pressure on a revolving object will
always cause it to move in a 90deg plane to that in which the force is
applied. So by pushing forward with one handlebar it will again fall
towards the side that was pushed forwards.

The gyroscopic effect may well play a part when a heavy motorbike wheel is
rotating at high speed but a bicycle wheel at lower rotational speeds is
very different.

Colin
--

On Thu, 20 Nov 2003 16:08:40 -0000, Colin Blackburn
wrote:

On Thu, 20 Nov 2003 17:02:39 +0100, Ace wrote:

There are two effects at work,
[...]
2. The gyroscopic effect, whereby pressure on a revolving object will
always cause it to move in a 90deg plane to that in which the force is
applied. So by pushing forward with one handlebar it will again fall
towards the side that was pushed forwards.

The gyroscopic effect may well play a part when a heavy motorbike wheel is
rotating at high speed but a bicycle wheel at lower rotational speeds is
very different.

I think you'll find that a bicycle's wheel actually makes up a higher
proportion of its total mass than does that of a motorcycle, so the
relative effect at any given speed will be higher.

Granted that it's more significant at higher speeds, but IME speeds
above 5mph are enough to be able to notice the gyro. effect, and
certainly at 10mph or more it's the predominant component of steering
input. Dunno about you, but I very rarely cycle more slowly than that.

--
Ace (bruce dot rogers at roche dot com)
Ski Club of Great Britain - http://www.skiclub.co.uk
All opinions expressed are personal and in no way represent those of the Ski Club.

In article , Ace wrote:

Granted that it's more significant at higher speeds, but IME speeds
above 5mph are enough to be able to notice the gyro. effect, and
certainly at 10mph or more it's the predominant component of steering
input.

No it isn't. A bike with a counter-rotating front wheel to eliminate
the gyro effect has even been built to prove this. rec.bicycles.tech
will probably have more than you want to know about the subject in the
FAQ and past Googleable posts.

Alan Braggins wrote:

In article , Ace wrote:

Granted that it's more significant at higher speeds, but IME speeds
above 5mph are enough to be able to notice the gyro. effect, and
certainly at 10mph or more it's the predominant component of steering
input.


No it isn't. A bike with a counter-rotating front wheel to eliminate
the gyro effect has even been built to prove this. rec.bicycles.tech
will probably have more than you want to know about the subject in the
FAQ and past Googleable posts.



Whatever. It's all off-topic as far as rec.skiing.resorts.europe is
concerned. Could you confine this thread to uk.rec.cycling from now on
please, unless any of this has anything to do with skiing?

I know the original x-post was from r.s.r.e, I don't think the x-posting
serves any purpose anymore.

On Fri, 21 Nov 2003 15:39:11 +0000, Steve Haigh
wrote:

Whatever. It's all off-topic as far as rec.skiing.resorts.europe is
concerned. Could you confine this thread to uk.rec.cycling from now on
please, unless any of this has anything to do with skiing?

I know the original x-post was from r.s.r.e, I don't think the x-posting
serves any purpose anymore.

Purpose? Jeeze, this is a low-enough volume group that a bit of chat
hardly does any harm, now does it? Now if it had been x-posted to ukrm
that might have been different...\
--
Ace (bruce dot rogers at roche dot com)
Ski Club of Great Britain - http://www.skiclub.co.uk
All opinions expressed are personal and in no way represent those of the Ski Club.

Ace writes:

On Thu, 20 Nov 2003 16:08:40 -0000, Colin Blackburn
wrote:

On Thu, 20 Nov 2003 17:02:39 +0100, Ace wrote:

There are two effects at work,
[...]
2. The gyroscopic effect, whereby pressure on a revolving object will
always cause it to move in a 90deg plane to that in which the force is
applied. So by pushing forward with one handlebar it will again fall
towards the side that was pushed forwards.

The gyroscopic effect may well play a part when a heavy motorbike wheel is
rotating at high speed but a bicycle wheel at lower rotational speeds is
very different.

I think you'll find that a bicycle's wheel actually makes up a higher
proportion of its total mass than does that of a motorcycle, so the
relative effect at any given speed will be higher.

We had this discussion on rec.bicycles.tech recently, you should look
it up. I tried some experiments and filmed them; I'll post a URL if
you're interested. The gyroscopic effects certainly exist, but they're
very weak compared to the gravitational effects. Bicycles
fundamentally steer by lean (as you yourself point out); the
gyroscopic effect at best helps to damp steering movements. Obviously
the gyroscopic effects increase with speed, but they don't become
dominant at speeds a human being can cycle at. There's an
interesting paper by a guy called David Jones called 'The Stability of
the Bicycle' which you might read; among other things he built a
bicycle with a counter-rotating gyroscope to cancel out any gyroscopic
effects from the front wheel. It rode perfectly well.

I have to say that some so-called experts are so wedded to the
gyroscopic theory in the face of overwhelming evidence that if you
show them actual film of an actual experiment they'll still deny the
evidence of their own eyes, but that's their problem.

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

;; I'd rather live in sybar-space

On Fri, 21 Nov 2003 22:05:17 GMT, Simon Brooke
wrote:

Ace writes:

On Thu, 20 Nov 2003 16:08:40 -0000, Colin Blackburn
wrote:

On Thu, 20 Nov 2003 17:02:39 +0100, Ace wrote:

The gyroscopic effect may well play a part when a heavy motorbike wheel is
rotating at high speed but a bicycle wheel at lower rotational speeds is
very different.

I think you'll find that a bicycle's wheel actually makes up a higher
proportion of its total mass than does that of a motorcycle, so the
relative effect at any given speed will be higher.

We had this discussion on rec.bicycles.tech recently, you should look
it up.

I will do so. Been away from there for far too long anyway.

I tried some experiments and filmed them; I'll post a URL if
you're interested.

Please.

I have to say that some so-called experts are so wedded to the
gyroscopic theory in the face of overwhelming evidence that if you
show them actual film of an actual experiment they'll still deny the
evidence of their own eyes, but that's their problem.

G Surely not?

--
Ace (bruce dot rogers at roche dot com)
Ski Club of Great Britain - http://www.skiclub.co.uk
All opinions expressed are personal and in no way represent those of the Ski Club.

In article , Steve Haigh wrote:
Alan Braggins wrote:

In article , Ace wrote:

Granted that it's more significant at higher speeds, but IME speeds
above 5mph are enough to be able to notice the gyro. effect, and
certainly at 10mph or more it's the predominant component of steering
input.


No it isn't. A bike with a counter-rotating front wheel to eliminate
the gyro effect has even been built to prove this. rec.bicycles.tech
will probably have more than you want to know about the subject in the
FAQ and past Googleable posts.

Whatever. It's all off-topic as far as rec.skiing.resorts.europe is
concerned. Could you confine this thread to uk.rec.cycling from now on
please, unless any of this has anything to do with skiing?

(Someone did point out that ski bikes demonstrate the same point.)


I know the original x-post was from r.s.r.e, I don't think the x-posting
serves any purpose anymore.

Followups-To header now set.