[msandford]

So are you saying that the entire mass of the whole flywheel is all the synchronous motor?

I guess I had assumed -- especially based on the picture and description -- that a portion of the mass of the device was the synchronous motor and that a portion of the mass of the device is just "dead weight" whose purpose is just to act as energy storage via rotational inertia.

The parallels to the steam turbine would seem apt; the turbine end of a generator has a lot of mass relative to the electrical end. Isn't that a part of the point? Or did I miss something?