But it doesn't need to be as large or as heavy as car wheel bearing. It is a question of the materials used and the way in which it is sealed (the sealing would add drag, admittedly). It shouldn't be that expensive either as the rear wheel bearing for a VW Golf costs just £8 in the local motorfactors.hubgearfreak said:get an engineering workshop to make you up a hub with two flanges of 18 holes on, but that take car wheel bearings.
do let us know how you get on
a. with the weight
b. with the (lack of) efficiency