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What is a moving bike so much easier to balance than one which is held stationary?Chris
We did this one recently, didn't we?I don't believe gyroscopic action is significant with lightweight cycle wheels because the moment of inertia is so small.
Take even a small bicycle wheel alone, put it on vertical on the road and give it a movement; you will see it won't fall down until its speed is almost zero.
QuoteTake even a small bicycle wheel alone, put it on vertical on the road and give it a movement; you will see it won't fall down until its speed is almost zero.Yes - I agree. BUT, in the case of an isolated wheel, the moment of inertia is the same about 'both' axes and the correcting moment would be large enough. In any case, the gyroscopic action doesn't actually keep the wheel upright, directly. As the wheel tips to the left, say, (about a horizontal axis in the direction of motion) precession makes it steer to the left (about a vertical axis) because of the cross product of the two rotation vectors. Then you get a righting moment due to the friction against the ground. A wheel on a smooth surface would fall over very quickly; the friction is necessary to provide a correcting moment. The faster the wheel is spinning, the more stable the situation because the resulting correcting moment will be greater for a given tilt.btw, I was wrong to dismiss, completely the gyroscopic effect in my earlier post; it is just very small, by comparison with the effect from the fork design, because of the massive M.I. of the bike and rider.The forwards offset of the forks must be the major factor. People have made bikes which are virtually impossible to ride by having a zero offset or, even a rearwards offset.