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Old October 6th 03, 07:45 AM
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Default "The Stability of the Bicycle"

Simon Brooke writes:

There are a few simple tests that he didn't do, one of which is to
wheel the bicycle along a walking speed holding on to the saddle
only. Most bicyclists have done this and those who were interested
will note that it works by gyroscopic force and not working at all
with no wheel rotation.


Uhhhmmmm...


I habitually wheel bicycles with one hand on the saddle. I've always
assumed that this worked in exactly the same way as riding a bike -
i.e. lean to steer. Although I agree that in principle a rotating
wheel has a gyroscopic effect at whatever speed it's rotating (and a
fast spinning wheel a considerable one) I don't believe that there's
much gyroscopic effect at this speed.


Take the wheel out, spin it in you hands and try to tilt it to the
left or right and note the force of the steering action. This should
convince you of its effect. You don't need to solve differential
equations.

Indeed, this seems to me to be borne out by the fact that one of my
bikes which has a noticeable tendency to pull left[1] can be wheeled
quite happily one hand on the saddle - but only if tilted slightly
right.


That puts the required bias into it but steering is done by gyroscopic
forces, trail taking care of the lean offset.

However I haven't done the maths and am just going on
perceptions. Has anyone done the maths for this?


Don't! There is more to be gained by intelligent observation of
natural phenomena.

Jobst Brandt

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