make the rotor a cam with a hilly base akong the edge that raises and lowers two magnets NS-SN stacked on top of each other.... soo when a N group comes along its up SN then as they pass the cam drops the SN to the upper NS magnet for the S group coming... think of a warped record spinning and wa...
BUT, the messed up thing is they spin opposite, one clockwise and one counter clockwise.... which i think is cool for being down in Oz.