Patent ID: 6895919

Claim:
A V-twin reciprocating apparatus having a crankshaft mounted in a crankcase for rotation about a crankshaft axis, the V-twin reciprocating apparatus comprising: a pair of cylinders, each defining a cylinder axis orthogonally disposed with respect to the crankshaft axis, the cylinders disposed in a V configuration with respect to one another, with the cylinder axes defining an included angle with respect to one another bisected by a central plane including the crankshaft axis; a pair of pistons disposed, one in each cylinder, for reciprocating movement in the cylinders along the cylinder axes from a top dead center (TDC) position to a bottom dead center (BDC) position in the cylinders; and a pair of connecting rods, one in each cylinder, for operatively connecting the pistons to the crankshaft such that the pistons will reach TDC and BDC in their respective cylinders at substantially the same time; the connecting rods joined at a crankshaft end thereof to the crankshaft by a pair of connecting rod journals centered at a common throw radius from the crankshaft axes and angularly displaced from one another along the throw radius by an angular displacement equal to the included angle of the cylinder axes; wherein the crankshaft further includes a counterweight fixedly attached thereto at point substantially diametrically opposite the pistons for rotation with the crankshaft about the crankshaft, to thereby substantially center the counterweight along the central plane at a point opposite the pistons when the pistons are at TDC, and along the center plane at a point adjacent the pistons when the pistons are at BDC; and wherein the crankshaft has a first direction of rotation, and the V-twin reciprocating apparatus further includes a first balance shaft operatively connected to the crankshaft for rotation about a first balance shaft axis in a direction opposite the first direction.