On 2007-01-22, Michael Press <[email hidden]> wrote: [snip]
Quoted message said:
There you go thinking again. The remainder is rife with error. Did you read David L. Johnson's reply? <[email hidden]>
David did you the favor of reading it all and commenting. What do you do? You do not reply to him, on the points he raised.
I did reply to the points he raised! I don't know what you're talking about.
And so you did.
Quoted message said:
The chief misunderstanding was in the interpretation of the word "Impulse". I think we cleared that up OK, but if David L. Johnson or yourself have any more useful comments to make then please go ahead and make them.
One important parameter that affects balancing a bicycle is the height of the center of mass; the higher the better. A well balanced weight on a vertical stick takes a long time to go from vertical to tipped over a little; particularly when compared to the time interval of the remainder of the fall. This means we have plenty of time to steer the bicycle back 'under the fall'.
This is seen balancing a broom vertically. A more important sounding phrase is `parametric resonance'. Attach a pendulum to a vertical disc and rotate the disc. Start the bar with the swivel attachment at the bottom and the free end above the swivel. At certain speeds the bar remains vertical. This can be taken further. Let the point of support of a pendulum oscillate vertically, then there is a range of frequencies for which the free end above support configuration is stable.
david wrote: > Can somebody please explain why a moving bicycle is easier to balance > than a stationary one. Maybe you can work this out for yourself!!
Think about - what is the difference between a moving bike and a stationary one (ie. what two big round things are doing something different in each case??). That might start you on the right track, yes?? 😉
If you're going to make snide remarks, it's better to be right. There has been considerable discussion about the gyroscopic effect of the wheels, but the bottom line is that that is not what allows you to balance on a bike. People have designed bikes with counter-rotating wheels to cancel the gyroscopic effect, and the bike is still ridable. You can also balance quite well while barely moving, in which case there is essentially no gyroscopic effect. Lots of us can balance on a bike while it is not moving forward at all (called a track stand). Actually, that practice shows what we really do, in that you can't do a track stand without the front wheel being turned at a significant angle. Then, pushing forward on the pedals tilts the bike to one side, pushing back (on a fixed gear) tilts it to the other. You do the same thing while riding by turning the wheel slightly and/or leaning -- you don't even notice it, usually.
People often ride bikes several hours without falling or stopping. If you do not believe that the centrifugal force from the rotating wheels helps to keep you upright then I suggest you try to trackstand for a couple of hours with your feet off the ground.
Believe your physics if you want, but I'd prefer to believe mine.
I do not believe in physics. On the other hand, you base your argument on belief.
Balancing a bicycle is almost entirely a matter of steering the bicycle back under our fall. We start to tip over, then steer the bicycle so that the contact patches are under our center of gravity. We do not notice the effort involved because we do much the same thing when walking. Walking is a controlled fall, just the same as bicycling. Angular momentum of the wheels is irrelevant to riding a bicycle.
On 2007-01-23, Ernie Willson <[email hidden]> wrote: [snip]
Quoted message said:
People often ride bikes several hours without falling or stopping. If you do not believe that the centrifugal force from the rotating wheels helps to keep you upright then I suggest you try to trackstand for a couple of hours with your feet off the ground.
Believe your physics if you want, but I'd prefer to believe mine.
The fact that balancing on a moving bike is easier than trackstanding doesn't imply that gyroscopic forces are involved.
Leaning a forwards-moving bike left makes it turn left but turning left makes it lean back to the right (centrifugal force), tending to correct the left lean. This provides a degree of stability, which is enough to keep the bike upright in conjunction with rider input.
All this would work if the wheels were replaced with skis or equipped with counter-rotating flywheels.
As someone (A.Muzi I think) pointed out, it's not trivial. The big unknown IMO is exactly what the rider does, since it's unconscious.
Replace your skewer with something longer that you can easily hold on to both ends of, then have a friend spin your wheel. It doesn't even have to be very fast to feel significant effects. While the wheel is spinning, try to tilt your hands from side to side. After doing this I doubt you'll argue any more that gyroscopic effects make it significantly easier to stay balanced.
Then why is it I do not feel this effect when riding my bicycle at 5 or 50 km/hr?
In article <[email hidden]>, [email hidden] says...
Quoted message said:
David L. Johnson said:
On Sat, 20 Jan 2007 02:32:35 -0800, Absent Husband wrote:
> david wrote: >> Can somebody please explain why a moving bicycle is easier to balance >> than a stationary one. > Maybe you can work this out for yourself!! > > Think about - what is the difference between a moving bike and a > stationary one (ie. what two big round things are doing something > different in each case??). That might start you on the right track, > yes?? 😉
If you're going to make snide remarks, it's better to be right. There has been considerable discussion about the gyroscopic effect of the wheels, but the bottom line is that that is not what allows you to balance on a bike. People have designed bikes with counter-rotating wheels to cancel the gyroscopic effect, and the bike is still ridable. You can also balance quite well while barely moving, in which case there is essentially no gyroscopic effect. Lots of us can balance on a bike while it is not moving forward at all (called a track stand). Actually, that practice shows what we really do, in that you can't do a track stand without the front wheel being turned at a significant angle. Then, pushing forward on the pedals tilts the bike to one side, pushing back (on a fixed gear) tilts it to the other. You do the same thing while riding by turning the wheel slightly and/or leaning -- you don't even notice it, usually.
People often ride bikes several hours without falling or stopping. If you do not believe that the centrifugal force from the rotating wheels helps to keep you upright then I suggest you try to trackstand for a couple of hours with your feet off the ground.
Believe your physics if you want, but I'd prefer to believe mine.
And it is also much easier to balance on one roller-blade when moving than when standing still. Would you also argue that this effect results from the gyroscopic effect of those tiny little wheels?
No, it is the effect of the bearing balls spinning around like a hamster on methedrine.
And it is also much easier to balance on one roller-blade when moving than when standing still. Would you also argue that this effect results from the gyroscopic effect of those tiny little wheels?
No, it is the effect of the bearing balls spinning around like a hamster on methedrine.
The IQ of the bearing balls, which ultimately have the responsibility for correcting leans before they become crashes, is variable. (Hey, the balls are inorganic!) Balls are dead dumb when stationary, and rapidly get smarter as they start rolling.
