Abstract: A UAV propulsion system is disclosed that utilizes a crankcase having a first crankcase compartment and a second crankcase compartment. Each crankcase compartment includes a corresponding cylinder assembly and piston, with each piston being interconnected with a rotatable crankshaft. A first airflow path extends from an exterior of the UAV propulsion system to the first crankcase compartment, and a separate second airflow path extends from the exterior of the UAV propulsion system to the second crankcase compartment. A first rotary valve may be mounted on and rotate with the crankshaft to control the airflow along the first airflow path to the first crankcase compartment, while a second rotary valve may be mounted on and rotate with the crankshaft to control the airflow along the second airflow path to the second crankcase compartment.

Abstract: An engine assembly having an improved mounting system or assembly is disclosed. Features of this mounting system include having crankcase arms that are integrally formed with a crankcase of the engine assembly, having multiple mounting legs that each have a dedicated vibration damping subassembly and where the stiffness of at least two of the mounting legs is different (by varying the configurations of the corresponding vibration damping subassemblies), and using a mounting ring or base with having differently oriented mounting pads for securement of the corresponding mounting leg relative thereto.

Abstract: A cooling shroud assembly for an engine is disclosed. This cooling shroud assembly includes a shroud body. There is an inlet door or flap to an interior of this shroud body, along with an outlet door or flap from this shroud body. When installed on an engine that is incorporated by a moving vehicle (e.g., aircraft, unmanned aerial vehicle, radio-controlled aircraft, watercraft), airflow through the shroud body from an inlet to an outlet. The position of the inlet and outlet doors may be adjusted (e.g., simultaneously) to change the airflow through the shroud body, and to thereby change the dissipation of heat from the operating engine via this airflow.

Abstract: A muffler for an engine assembly is disclosed. This muffler is arcuately-shaped and may be configured so as to not protrude beyond an outermost perimeter of an engine assembly that uses this muffler. The muffler may include a lower chamber, an intermediate chamber, and an upper chamber that are disposed in a common stack. Exhaust inlet and outlet ports to the muffler may be located at a common end of the muffler body. The exhaust inlet port may lead into the lower chamber. Multiple exhaust outlet ports out of the upper chamber may be utilized to allow the muffler to be used with different vehicle configurations, for instance to direct exhaust out of the muffler in different directions.

Abstract: An engine assembly having an improved mounting system or assembly is disclosed. Features of this mounting system include having crankcase arms that are integrally formed with a crankcase of the engine assembly, having multiple mounting legs that each have a dedicated vibration damping subassembly and where the stiffness of at least two of the mounting legs is different (by varying the configurations of the corresponding vibration damping subassemblies), and using a mounting ring or base with having differently oriented mounting pads for securement of the corresponding mounting leg relative thereto.

Abstract: A muffler providing a compact and low-profile form factor for small two-stroke engines is described, particularly useful for aerodynamic radio controlled aircraft. The muffler comprises a tuned internal header eliminating the need for an external header to mount the inventive muffler to the exhaust port of a two-stroke engine while maintaining enhanced engine performance, obviating the need for a conventional tuned-pipe exhaust.

Abstract: A muffler providing a compact and low-profile form factor for small two-stroke engines is described, particularly useful for aerodynamic radio controlled aircraft. The muffler comprises a tuned internal header eliminating the need for an external header to mount the inventive muffler to the exhaust port of a two-stroke engine while maintaining enhanced engine performance, obviating the need for a conventional tuned-pipe exhaust.