Abstract: A planetary system, mounted within a housing, is the basis of manufacturing a motor, a pump, or a fluid flow meter. The housing is provided with an inlet and an outlet. The planetary system comprises: a cylindrical core (1) and its axis (2), two discs (9) mounted on the two bases of the core, the planets (4) rotated into special circular recesses of the core, and the transmission system (gears 11-14) giving motion to the planets. When a motor is used to rotate the shaft (2), the planetary system is converted into a pump since it sucks (depending on the supply) air or liquid from the inlet and discharges the same under pressure at the outlet. When on the other hand the inlet of the planetary system is connected to a duct containing a fluid under pressure, the planetic system is converted into a flow meter or a hydraulic motor or a gas motor, for liquids or gases respectively. If as depicted in FIG.