Abstract: A positive displacement device capable of performing the typical positive displacement device functions such as pump, generator, flow meter, etc. is presented. The device comprises a housing having interior surfaces defining an inlet and an outlet separated by two generally circular cylindrical fluid flow chambers. A fulcrum is near the center of the device. A positive displacement barrier separates the inlet from the outlet. The barrier which is the only moving part comprises two circular cylindrical pistons coupled by a generally planar plenum barrier. The plenum barrier slides back and forth and teeter totters on a fulcrum so that each piston is always sealing the inlet from the outlet along the inside of its associated cylinder while each piston orbits its cylinder in a different direction. Fluid is caused to move around the piston by the piston and its sealing point.