Electromechanical means of implementing self-acting gas bearings within free piston Stirling cycle machinery

The development of two devices that were used successfully to implement gas bearings within Stirling cycle cryocoolers, a brushless DC motor and an induction motor, is described. The chief hindrances to the implementation of spin bearings are addressed, along with the advantages and disadvantages of each motor in dealing with these hindrances. In particular, in order to initiate rotation of a piston that is coupled to a linear alternator, a toggling effect must be overcome. Once rotation is achieved, the toggling effect is of lesser consequence, due to the conservative nature of the magnetic forces causing toggling. After several unsuccessful attempts to achieve piston rotation by turbine elements, the motors referred to above were designed to spin the pistons and applied to the Stirling cryocoolers. Data from hardware testing are reported