Crankshaft for an internal combustion engine

A rotating group for a three cylinder internal combustion engine, the rotating group comprising:

• three pistons, each associated with a respective cylinder and connected through a respective connecting rod to a respective crankpin, the crankpins being disposed on a single crankshaft;
• wherein the crankshaft comprises:
• at least four main journals aligned on a crankshaft axis of rotation;
• and
• at least three crankpins, each disposed about a respective crankpin axis and positioned between the main journals;
• each of the respective crankpin axes being oriented parallel to, and spaced radially from, the crankshaft axis of rotation;
• each of the crankpins being joined to a pair of crank arms for force transmission between the crankpin and the pair of crank arms;
• each pair of crank arms being joined to a respective main journal for transmitting torque between the pair of crank arms and the main journal;
• and
• at least two of the crankpins being spaced radially a first semi-stroke distance from the crankshaft axis of rotation, and a third crankpin being spaced radially a second semi-stroke distance from the crankshaft axis of rotation, wherein the first semi-stroke distance differs from the second semi-stroke distance.