Well to give you a ballpark figure; to spin Richie's quite grippy 100mm wheel at 400rpm on a flat surface takes about 100W. Anything more than that would just spin the wheel faster.

I approve of trying quirky and untested products; Most of the things in Richie are rarely used in other feathers, were basically found in the scrap, and worked very well.. though sadly the quirky parts I'm trying out these days are rather more hi-tech :L