Abstract: A rotating machine with variable volumes which can rotate in one and/or two directions like the transmission shaft, more of less than (2.pi.). The machine is composed of a body with an inner cavity holding an articulated rotating prismatic structure, composed of one or more sides. Between the inner cavity and the sides of the prismatic structure, and among the same sides in the inner area, are fluid-retaining variable-volume chambers. The cyclic volume machine exploits the variations of the physical characteristics of fluids whose movements are the cause or effect of transmission shaft rotation. In transverse bars, and/or appropriate hinges between the sides of the rotor, centripetal forces oppose centrifugal forces. Lubricating and cooling systems are foreseen. The cyclic volume machine can be coaxial to a common transmission shaft and may be used as a pump, compressor, motor, engine, valve, distributor, hydraulic joint, and heat generator.