Engine crankshaft structure

An engine crankshaft having a front end, a rear end, and a longitudinal axis extending from said front end to said rear end, the crankshaft comprising:

• a plurality of longitudinally spaced journals coaxial with said longitudinal axis and a plurality of crank pins each having an axis spaced from and parallel to said longitudinal axis, at least one crank pin being disposed longitudinally between adjacent journals, and a line between the longitudinal axis and the axis of a forwardmost one of said crank pins defining, with said longitudinal axis, a reference plane;
• a plurality of transverse arms spaced apart along the longitudinal axis, each arm connecting corresponding ones of said plurality of crank pins and journals, said arms including a front arm, a middle arm, a rear arm, a forward plurality of arms disposed between said front arm and said middle arm, and a rearward plurality of arms disposed between said middle arm and said rear arm;
• a front, a middle, and a rear counterweight associated with said front, middle, and rear arms, respectively, said front and rear counterweights providing oppositely directed force vectors lying in said reference plane and balancing each other;
• a forward counterweight associated with one of said forward plurality of arms;
• a rearward counterweight associated with one of said rearward plurality of arms, said forward counterweight, said rearward counterweight and said middle counterweight balancing each other;
• and
• at least one of said forward plurality of arms and at least one of said rearward plurality of arms being disposed in axial symmetry with each other with respect to said middle arm and having no counterweights associated therewith,
• wherein the improvement comprises said forward counterweight providing a force vector disposed at an angle spaced counterclockwise from and in the same quadrant as a line extending from the longitudinal axis at an angle 150 degrees clockwise from said reference plane, said rearward counterweight providing a force vector disposed at an angle spaced clockwise from and in the same quadrant as a line extending from the longitudinal axis at an angle 30 degrees clockwise from said reference plane, when the crankshaft is viewed from the front end, and wherein the force vector of the forward counterweight is disposed at an angle of 135 degrees clockwise from the reference plane and the force vector of the rearward counterweight is disposed at an angle of 45 degrees clockwise from the reference plane.