Reciprocating piston mechanism

A reciprocating piston mechanism comprising

• a crankcase;
• a crankshaft having at least a crankpin, said crankshaft being supported by the crankcase and rotatable with respect thereto about a crankshaft axis;
• at least a connecting rod including a big end and a small end;
• a piston being rotatably connected to the small end;
• a crank member being rotatably mounted on the crankpin, and comprising at least a bearing portion having an outer circumferential wall which bears the big end of the connecting rod such that the connecting rod is rotatably mounted on the bearing portion of the crank member via the big end;
• wherein the crank member is driveably coupled to an auxiliary wheel which is fixed to an auxiliary shaft that extends concentrically through the crankshaft, wherein the crankshaft and the auxiliary shaft are rotatable with respect to each other, wherein the auxiliary wheel is disposed at a same side of an adjacent crank arm as the crank member, wherein the reciprocating piston mechanism is configured such that under operating conditions the crank member rotates about a centerline of the crankpin in an opposite direction as the crankshaft and at half speed thereof, whereas the auxiliary shaft has a substantially fixed angular position with respect to the crankcase.