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: 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: An engine with an acoustic emissions valve or reflector for an exhaust system is disclosed. This reflector is disposed outside of the exhaust system—the reflector is disposed in the atmosphere into which the exhaust system discharges. The reflector is moved between a reflecting position (where the reflector reflects or obstructs acoustic emissions from the exhaust system) and a non-reflecting position (where the reflector does not obstruct the bulk exhaust gas flow from the exhaust system) by rotation of the crankshaft.

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.