Adjustable muffler for model aircraft type engines

In a method for muffling the exhaust of a two-cycle combustion engine of the type commonly used to power miniature aircraft, cars, boats and models, the steps of:

• expanding the exhaust gas derived from the exhaust port of the engine into an expansion chamber having a volume at least three times that of the displacement of the engine for cooling of the exhaust gas;
• thence feeding the expanded and cooled exhaust gas through a baffle chamber having a plurality of sonic wave reflective baffles spaced apart along the direction of exhaust flow through the baffle chamber;
• and
• constricting the flow of exhaust gases exiting from the downstream end of the baffle chamber so as to provide a reflection of sonic wave energy producing a substantial back pressure upon the baffle chamber and engine.

In a muffler for muffling the exhaust of a two-cycle combustion engine of the type commonly used to power miniature aircraft, cars, boats and models:

• a tubular expansion chamber having a port therein for exhaust gas communication with the exhaust port of the engine to be muffled for feeding of the exhaust gases of the engine into said expansion chamber for expansion and cooling of the exhaust gas therein;
• a tubular baffle chamber connected in gas communication with said expansion chamber downstream thereof, said baffle chamber having cross-sectional dimensions to present higher impedance to the flow of exhaust gas therethrough than that presented by said expansion chamber;
• a plurality of baffle members disposed within said baffle chamber in spaced apart relation taken in the direction of exhaust gas flow therethrough for reflecting sonic waves in the exhaust stream back to the engine for muffling the flow of exhaust gas therethrough;
• and
• a tail pipe having lesser cross-sectional dimensions for the flow of exhaust gas therethrough than those of said baffle chamber so as to produce a sonic wave reflection on said baffle chamber, said tail pipe having a coupling portion for mating with a coupling portion of said baffle chamber for coupling said tail pipe to said baffle chamber.