Crankshaft
The main rotating shaft in an engine that converts the reciprocating (up-and-down) motion of the pistons into rotational force.
The crankshaft is one of the most critical moving components inside an internal combustion engine. Positioned in the lower section of the engine block within the crankcase, it is connected to the pistons via the connecting rods. As the pistons are pushed down by the combustion of the air-fuel mixture, their linear downward force is converted by the offset throws of the crankshaft into rotational movement, which ultimately drives the vehicle's wheels through the transmission.
Because it is subjected to immense torsional stress and rotational friction, the crankshaft must be extremely strong and is typically made from forged steel or cast iron. It is supported by a series of main bearings that are constantly lubricated with pressurized engine oil. Heavy counterweights are integrated into the crankshaft's design to balance the movement of the pistons and connecting rods, reducing vibrations and ensuring smooth operation at high engine speeds.
Problems with the crankshaft usually stem from insufficient engine lubrication, which can cause the main bearings to wear out, seize, or spin. Symptoms of crankshaft or bearing damage include severe engine knocking noises, loss of oil pressure, or a seized engine that refuses to rotate. Replacing or machining a crankshaft is a major repair that requires a complete engine disassembly and rebuild.