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What role does the crankshaft play in a gasoline engine?

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Labeled cross-sectional diagram of a V-type gasoline engine for an automobile, showing internal components such as pistons, crankshaft, camshaft, intake and exhaust valves, connecting rods, spark plugs, and intake manifold. — gasoline engine Cross section of a V-type engine.

In a gasoline engine, the crankshaft serves as a critical component of the slider-crank mechanism, primarily responsible for converting the reciprocating (straight-line) motion of the pistons into rotary motion.12

The crankshaft performs several essential functions:

Motion Conversion: Through the connecting rod, it translates the linear force generated by the combustion of the gasoline-air mixture into rotational energy.12
Stroke Determination: The radial offset of the crankshaft's throws establishes the length of the piston stroke, as the offset is equal to half of the total stroke distance.2
Engine Timing and Balance: The arrangement of the crankshaft's throws is designed to match the engine's firing order, ensuring cylinders fire at precise intervals. Additionally, counterweights are often added to the crankshaft to offset eccentric masses, which helps minimize engine vibration and improve balance.2
Energy Storage: A flywheel is typically attached to the crankshaft to provide the rotational energy necessary to drive the pistons through their return strokes.1