Abstract: A compact muffler (40) for an engine exhaust system, which is particularly applicable for use with small, reciprocating piston two-stroke engines of the type used on unmanned aerial vehicles (UAVs). The compact muffler (40) comprises an exhaust gas flow path (67) between an inlet (61) and an outlet (63). The exhaust gas flow path (67) comprises a plurality of adjacent flow passages (65), wherein at least two of the adjacent flow passages (65) are fluidly connected in series to enable the flow of exhaust gas from one to the other along the flow path (67). The adjacent flow passages (65) are configured for fluid flow therealong in opposed directions. A bypass passage (70) is provided between the two adjacent flow passages (65) for further communication between the two flow passages and to promote an equalisation of fluid pressure within the two adjacent passages (65). A UAV having an internal combustion engine (31) fitted with an exhaust system comprising the compact muffler (40) is also disclosed.

Abstract: A muffler (40) devised particularly for use with an engine of the type used on unmanned aerial vehicles (UAVs), and a UAV (10) having an engine (30) fitted with the muffler (40). The muffler (40) comprises a body (51) having an interior chamber (60). The muffler body (51) has a first end section (53) and a second end section (55). The first end section (51) is adapted for mounting onto the engine (31) by way of a first mount (81), with the interior chamber (60) in communication with an exhaust outlet of the engine (31) to receive exhaust flow therefrom. The second end section (53) is adapted to be mounted by way of a second mount (82) in a manner resisting movement with respect to the engine (31). In one arrangement, the second mount (82) is configured to yieldingly resist movement with respect to the engine (30). In another arrangement, the second mount (82) is configured to mount the second end section (55) under a preload resisting movement of the second end section with respect to the engine (30).

Abstract: A muffler devised particularly for a small, reciprocating-piston two-stroke internal combustion engine of the type used on unmanned aerial vehicles. The muffler comprises a body incorporating an inlet, an outlet, and a plurality of chambers for exhaust gas flow from the inlet to the outlet. The body is configured to present a compact profile for installation on the engine. The chambers are so configured that adjacent chambers communicate to facilitate exhaust gas flow from the inlet to the outlet via flow passages. The various chambers comprise an inner chamber, an outer chamber, and one or more intervening chambers disposed between the inner and outer chambers. The various chambers are disposed one about another in annular formation. This arrangement creates a long flow path from the inlet to the outlet incorporating various directional changes.

Abstract: A muffler devised particularly for a small, reciprocating-piston two-stroke internal combustion engine of the type used on unmanned aerial vehicles. The muffler comprises a body incorporating an inlet, an outlet, and a plurality of chambers for exhaust gas flow from the inlet to the outlet. The body is configured to present a compact profile for installation on the engine. The chambers are so configured that adjacent chambers communicate to facilitate exhaust gas flow from the inlet to the outlet via flow passages. The various chambers comprise an inner chamber, an outer chamber, and one or more intervening chambers disposed between the inner and outer chambers. The various chambers are disposed one about another in annular formation. This arrangement creates a long flow path from the inlet to the outlet incorporating various directional changes.

Abstract: An air cooling system for an unmanned aerial vehicle including a propeller (14) driven by an engine (12) has at least one cooling air duct (22) to direct cooling air to cool a vehicle component e.g. a cylinder head. The duct has at least one air inlet and at least one air outlet. Operation of the propeller causes a pressure differential between the air outlet (24,124) and the air inlet (23,123) which draws air through said cooling air duct (22). A cowling (16) can cover at least part of the engine, and can form a plenum and have the supply of cooling air through a front face aperture (164) or side walls (17) of the engine cowl (16).

Abstract: An air cooling system for an unmanned aerial vehicle including a propeller (14) driven by an engine (12) has at least one cooling air duct (22) to direct cooling air to cool a vehicle component e.g. a cylinder head. The duct has at least one air inlet and at least one air outlet. Operation of the propeller causes a pressure differential between the air outlet (24,124) and the air inlet (23,123) which draws air through said cooling air duct (22). A cowling (16) can cover at least part of the engine, and can form a plenum and have the supply of cooling air through a front face aperture (164) or side walls (17) of the engine cowl (16).