"W K" wrote in message ...
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Jim Beam writes:

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.

please explain. gyro reaction is _90 degrees to the applied force_.
i.e. my front wheel, spinning "forwards" tries to tilt top
rightwards when turned to the left. you seem to be implying that
gyro recation is responsible for banking the bike to the left when
steered left.

Not at all. I suggest that the wheel spinning forward steers to the
left when tilted to the left and to the right when tilted to the
right.

I wouldn't disagree with the above.

This is the means by which the bicycle steers when walking the
bike while held by the saddle and also what enables it to be ridden
no-hands.

What is the relative contribution of the different effects - ie to what
degree is the above more important than the effects of rake and trail - at
different speeds and with the addition of the rider to the whole system.

The mass imbalance is a constant for a given bicycle and the speed at
which it will impart steering action is dependent on the lean angle
and is easily observable with a stationary bicycle. Gyroscopic
precession is dependent on rotation rate of the wheel, the faster the
wheel rotates the higher the torque required to lean the wheel for a
give rate of precession. At walking speed (1/2 rev/sec) the difference
in torque between leaning this and a stationary wheel will be the
amount of torque that causes the wheel to turn (precess). It will be
small and likely doesn't even overcome the trail effect of keeping the
wheel pointed straight ahead. Rider weight adds more tire scrub
effects which are small but riding no hands at low speeds is almost
impossible due to insufficient gyroscopic forces. It's not until the
bicycle is going ~15mph does no hands riding become feasible for the
ordinary rider. Gyroscopic forces being large enough to impart
adequate self steering.

Phil Holman