[NoodleKnight]

In 2003 we mounted optical sensors perpendicular to our wheel sprockets and stickered on reflective material on the sprockets. They worked pretty well, but after a few competitions the mounts got chewed by the chain, so we removed them. In 2004 we used hall-effect sensors, we bought a type of building-toy-thing... (forgot the name) which had really powerful magnets (they were cylindrical, about 5 mm in diameter, i think), we cut the magnets out, drilled holes in our motor couplers and epoxied them in. The probes were glued into the motor mounts, directly above the magnets. It worked well, up to the point we reached very fast speeds, once in a while it works, sometimes it doesn't.