I wonder why there are no micro-rotor movements produced in large numbers given that is more beautiful and slimmer than the central rotor autos. The central rotor offers larger moment of inertia (to get the same inertia on a micro-rotor perhaps you need a heavy material as gold or tungsten). But in these days of tight tolerances and highly efficient systems, I assume even with less inertia, the micro-rotor can be effective. So I wonder what other advantages the central rotor has over the micro-rotor.
high end micro-rotors: