Original poster: Steve Conner <steve@xxxxxxxxxxxx>
Use of a generator on bearings works fine and is a lot safer.
I've also seen an induction motor used as a brake. You pass DC through the stator windings (any one you like, it doesn't seem to matter much) and it acts as an eddy current brake. You have to blow a lot of cooling air through the rotor since all the mechanical power is dissipated in it. It's probably not the best dyno brake in the world, but it might be of interest if you have an old 3 phase motor lying about.
Steve Conner http://www.scopeboy.com/