Imagine a single wheel rolling along level ground,
with a round cross section so there's no effective
balance point -- it's bound to tip one way or the other.
A. Say the wheel leans slightly to the left. Since the center
of mass is offset from the contact point with the ground,
the force of gravity produces a torque tending to pivot
the wheel to the left around the contact patch.
B. Because the wheel is spinning, the gyroscopic effect
translates this "gravitation torque" into a twisting force
about a vertical axis causing the wheel to turn left.
C. Frictional force causes the contact patch to move left,
but the wheel's center of mass continues straight forward
due to conservation of momentum.
D. Now the wheel is tilting slightly to the right.
Repeat steps A through D, in the reverse direction.
The wheel oscillates through the balance point. However,
these perambulations are too small and rapid to be seen
by a casual observer until frictional forces have reduced
the wheel's kinetic energy to the point where
the oscillations become visible wobbles... which rapidly
escalate until the wheel lacks enough energy to recover
and it collapses.
This mechanism also affects bicycles and motorcycles where,
however, it is merged with the action of the steering
geometry and the rider's interventions to produce
a more complex dynamic.
SQ
sean_q_ wrote:
> Imagine a single wheel rolling along level ground,
> with a round cross section so there's no effective
> balance point -- it's bound to tip one way or the other.
> A. Say the wheel leans slightly to the left. Since the center
> of mass is offset from the contact point with the ground,
> the force of gravity produces a torque tending to pivot
> the wheel to the left around the contact patch.
>
> B. Because the wheel is spinning, the gyroscopic effect
> translates this "gravitation torque" into a twisting force
> about a vertical axis causing the wheel to turn left.
>
> C. Frictional force causes the contact patch to move left,
> but the wheel's center of mass continues straight forward
> due to conservation of momentum.
>
> D. Now the wheel is tilting slightly to the right.
>
> Repeat steps A through D, in the reverse direction.
> The wheel oscillates through the balance point. However,
> these perambulations are too small and rapid to be seen
> by a casual observer until frictional forces have reduced
> the wheel's kinetic energy to the point where
> the oscillations become visible wobbles... which rapidly
> escalate until the wheel lacks enough energy to recover
> and it collapses.
>
> This mechanism also affects bicycles and motorcycles where,
> however, it is merged with the action of the steering
> geometry and the rider's interventions to produce
> a more complex dynamic.
Don't be so silly. Tim and twitbull both told us that
rolling motorcycles are no more stable than stationary
motorcycles, and everyone knows they're never wrong about
anything... <g>
--
"Condemnation without investigation is the height of ignorance." --
Albert Einstein.
http://911research.wtc7.net
http://www.journalof911studies.com/
http://www.ae911truth.org
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> with a round cross section so there's no effective
> balance point -- it's bound to tip one way or the other.
> A. Say the wheel leans slightly to the left. Since the center
> of mass is offset from the contact point with the ground,
> the force of gravity produces a torque tending to pivot
> the wheel to the left around the contact patch.
>
> B. Because the wheel is spinning, the gyroscopic effect
> translates this "gravitation torque" into a twisting force
> about a vertical axis causing the wheel to turn left.
>
> C. Frictional force causes the contact patch to move left,
> but the wheel's center of mass continues straight forward
> due to conservation of momentum.
>
> D. Now the wheel is tilting slightly to the right.
>
> Repeat steps A through D, in the reverse direction.
> The wheel oscillates through the balance point. However,
> these perambulations are too small and rapid to be seen
> by a casual observer until frictional forces have reduced
> the wheel's kinetic energy to the point where
> the oscillations become visible wobbles... which rapidly
> escalate until the wheel lacks enough energy to recover
> and it collapses.
>
> This mechanism also affects bicycles and motorcycles where,
> however, it is merged with the action of the steering
> geometry and the rider's interventions to produce
> a more complex dynamic.