Abstract: A rotary engine device, which may be an internal combustion engine or a pump, having a spherical rotor with a radial web rotatable in an oblique chamber, and curved vanes axially slidable through the web, is provided with an outer ring fixed to the outer periphery of the web to rotate therewith and having a spherical inner surface defining the outer peripheral wall of the oblique chamber. The ring eliminates circumferential sliding friction between the vanes and the outer wall of the chamber. When constructed as an internal combustion engine, a drum cam fixed to the rotor actuates intake and outlet valves, an ignition device and a fuel injector so that each is actuated only on alternate revolutions of any one expansion compartment between vanes to produce four-stroke-cycle operation of the engine.