42mA is far too generous. Remember this motor has frictionless bearings, it's wind down could be hours long. Just a small current pulse now and then and this will be spinning for months maybe. Here's an example of a frictionless homopolar motor:
YouTube - levitation Homopolar motor
As you see only a small initial pulse is needed to keep this spinning for quite a while.
Steorn had years to figure out the best demo setup, why not a real physical load instead of something that barely needs any energy?