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#31
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Learning to ride a bicycle
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. |
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#32
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Learning to ride a bicycle
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 -- |
#33
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Learning to ride a bicycle
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. |
#34
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Learning to ride a bicycle
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. |
#35
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Learning to ride a bicycle
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. |
#36
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Learning to ride a bicycle
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. |
#37
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Learning to ride a bicycle
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 |
#38
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Learning to ride a bicycle
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. |
#39
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Learning to ride a bicycle
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. |
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