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I say again: you have to understand the axle and
bearing in the middle of the wheel.
The thought about the railroad is apt and useful.
The wheel has a flange that is to a first approximation
cone-like ... I'm calling attention to the fact that
the wheel has a smaller diameter zone on the outboard
side and a larger-diameter zone (the flange) on the
inboard side.
| | | |
| | | |
|_ | | _|
R|_| |_|R (R = rail)
R R
The bicycle exploits the same physics, BUT IT HAPPENS
INSIDE THE BEARING, nowhere near the tire/road interface.
The bearings are distinctly conical. It's like the
railroad wheel+rail, all rolled up into a package.
I'd tell you to take one apart but it is a bit of
a bother to get it put back together properly.
Perhaps you could go to the bike shop and ask
Wilbur or Orville to give you a scrap one. Similarly
an auto shop should be able to give you scrap
bearings from a car wheel. They are distinctly
conical.
Here's a picture that shows part of the story.
http://static.howstuffworks.com/gif/bearing-wheel.jpg
To repeat: The bearing can roll freely in one direction
for the same reason a railcar can roll down the rails.
The bearing develops a tremennndous force if you try
to push it in the cross direction, for much the same
reason that the flange on a railcar wheel develops
a force if you push it sideways. The bearing actually
carries the idea to perfection; you can't "derail"
it.
Remember how you steered your "belly slam" snow
sled? You simply deformed the runners so that the
leading portion took a new orientation. You can find
adult vehicles which turn without the (apparently
difficult) complication of a wheel/axle, simply by
orienting sliding front skids. I think some snow-mobiles
may do this. Is this the rudder/keel effect adapted to
wheel-less land vehicles?
Perhaps beginning with an analysis of these "steering
skid systems" would give a fresh and easier start to
grasping this "turning physics".