  We discuss theoretically the properties of an electromechanical oscillator
whose operation is based upon the cyclic, quasi-conservative conversion between
gravitational potential, kinetic, and magnetic energies. The system consists of
a strong-pinning type-II superconductor square loop subjected to a constant
external force and to magnetic fields. The loop oscillates in the upright
position at a frequency that can be tuned in the range 10-1000 Hz, and has
induced in it a rectified electrical current. The emphasis of this paper is on
the evaluation of the major remaining source of losses in the oscillations. We
argue that such losses should be associated with the viscous vibration of
pinned flux lines in the superconductor Nb-Ti wire, provided the oscillator is
kept close to zero Kelvin, under high-vacuum, and the magnetic field is
sufficiently uniform. We discuss how other different sources of loss would
become negligible for such operational conditions, so that a very high quality
factor Q exceeding 10^(10) might in principle be reached by the oscillator. The
prospective utilization of such oscillator as a low-frequency high-Q clock is
analyzed.Since publication the ideas in this paper have been explored both by
the author and elsewhere, in applications covering Metrology, quantum systems,
and gravimetry.
