On Wed, 18 Jan 2006 14:38:13 +0000, Adrian C wrote:

Light wheels might take a l-o-n-g time waiting for it to stop unless you
gumm up the bearing somehow

Magnet near the rim. Eddy currents in the moving aluminium will slow it
down but don't attract it when stationary.

Then a ticker on the spokes so that the wheel always clear stops _on_ a
number, not bouncing around between them.

Bicycle wheels are biased though (there's a bit of weight missing for
the valve stem). You need to counterbalance this or it really will stop
at the same place every time.