A mechanical assembly for maintaining an air gap between a stator and a rotor in an electro-mechanical energy converter , the assembly comprising: a structural sleeve ; a plurality of stator sections attached to an inner surface of the structural sleeve; a hub enclosed by the structural sleeve and concentric with the structural sleeve; a plurality of rotor sections flexibly coupled to the hub and enclosed by the structural sleeve; and a rail system positioned within the structural sleeve and concentric with the structural sleeve, the rail system for guiding the rotor sections in a substantially circular path and for defining an air gap between the plurality of stator sections and plurality of rotor sections; characterised in that each of the rotor sections is flexibly coupled to the hub by: a) a drive dog adapted for transferring torque between a given rotor section and the hub; and a holding spring disposed between the given rotor section and the hub, and adapted for providing a radial force pushing against the hub to push the given rotor section against the rail system; or b) a drive arm pivotably attached to the hub at an end and pivotably attached to a given rotor section at another end, the drive arm being adapted for transferring torque between a given rotor section and the hub; and an arm spring pivotably attached to the hub at an end and pivotably attached to an associated drive arm at another end, the arm spring being adapted for providing a radial force pushing against the hub to push the associated drive arm and given rotor section against the rail system. a structural sleeve ; a plurality of stator sections attached to an inner surface of the structural sleeve; a hub enclosed by the structural sleeve and concentric with the structural sleeve; a plurality of rotor sections flexibly coupled to the hub and enclosed by the structural sleeve; and a rail system positioned within the structural sleeve and concentric with the structural sleeve, the rail system for guiding the rotor sections in a substantially circular path and for defining an air gap between the plurality of stator sections and plurality of rotor sections; characterised in that each of the rotor sections is flexibly coupled to the hub by: a) a drive dog adapted for transferring torque between a given rotor section and the hub; and a holding spring disposed between the given rotor section and the hub, and adapted for providing a radial force pushing against the hub to push the given rotor section against the rail system; or b) a drive arm pivotably attached to the hub at an end and pivotably attached to a given rotor section at another end, the drive arm being adapted for transferring torque between a given rotor section and the hub; and an arm spring pivotably attached to the hub at an end and pivotably attached to an associated drive arm at another end, the arm spring being adapted for providing a radial force pushing against the hub to push the associated drive arm and given rotor section against the rail system. a) a drive dog adapted for transferring torque between a given rotor section and the hub; and a holding spring disposed between the given rotor section and the hub, and adapted for providing a radial force pushing against the hub to push the given rotor section against the rail system; or b) a drive arm pivotably attached to the hub at an end and pivotably attached to a given rotor section at another end, the drive arm being adapted for transferring torque between a given rotor section and the hub; and an arm spring pivotably attached to the hub at an end and pivotably attached to an associated drive arm at another end, the arm spring being adapted for providing a radial force pushing against the hub to push the associated drive arm and given rotor section against the rail system. <EOS>