External combustion rotary engine

A rotary engine, comprising:

• a toroidal chamber having an outer circumference and an inner circumference concentric about an axis;
• an intake port extending into said toroidal chamber for introducing a pressurized gas;
• an exhaust port extending from said toroidal chamber adjacent said intake port for venting an exhaust gas;
• a gate extending across said toroidal chamber between said intake port and said exhaust port, an outer edge of said gate hinged about a pivot parallel to said axis and outside said outer circumference of said toroidal chamber, said gate being biased to a closed position across said toroidal chamber, said gate being arranged to open only in one direction toward said intake port;
• said pivot includes a tube with a longitudinal slot, and said gate includes a cylindrical head and a constricted neck, said cylindrical head sliding into said tube, said constricted neck sliding into said longitudinal slot;
• a piston positioned within said toroidal chamber, a back of said piston for being acted upon by said pressurized gas, so that said piston is driven around said toroidal chamber in said direction, said gate being normally-closed for directing said pressurized gas to flow in said direction, a front of said piston pushing said exhaust gas out through said exhaust port, said gate pivoting open when struck by said piston to allow passage of said piston, said gate being biased closed after said piston has passed;
• a driveshaft aligned with said axis of said toroidal chamber, said driveshaft connected to said piston for simultaneous rotation;
• a tubular cam coaxially positioned on said driveshaft and arranged for simultaneous rotation;
• and
• an intake valve positioned over said intake port, said intake valve having a stem with a tip engaging said cam, said stem following a protruding cam surface of said cam as said cam rotates, so as to control opening and closing of said intake valve on said intake port.