What Is A Crankshaft?

The crankshaft is the central hub of your engine's operation. It's what converts the burning of fuel into the rotational motion that moves your car.

Usually located at the bottom center of the engine block, the crankshaft has crank throws (also called crankpins) that jog from it in an offset. These have connecting rods that attach to each piston so that as the pistons move up and down in the cylinders (up from the turn of the crank pushing them up and back down as the fuel ignites and creates pressure to push downwards), the crankshaft rotates.

The following illustration from Wikimedia shows how this works. The crankshaft is in red while the rods and pistons are in gray, the cylinders in blue, and the crank pulley in black:

As an integral part of the engine, the crankshaft is typically one of the most robust moving parts in the block. Its rotation will turn a pulley at front which connects to a timing belt or chain. This moves other items on the engine, causing fuel and air to be injected or dropped into the cylinders at the right time for ignition and engine coolant to be circulated to keep the engine at operating temperature.

The turning of the shaft itself often turns the distributor, which sends electrical pulses to the spark plugs in line with the engine timing to ignite the fuel:air mixture in each cylinder.

The crankshaft's other end typically connects to a flywheel or other dampener to reduce the jerkiness of its inherent motion before being transferred to the drive line, usually through a transmission.