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What is a car's crankshaft?


The crankshaft runs inside the bottom end of the engine and converts the vertical movement of the pistons into horizontal rotational movement.

Crankshafts have been around since the Second Century, having been used in applcations such as water mills and sawmills.

They eventually became prominent in paddle boats, turning the energy from steam-powered pistons into rotational energy for the paddle wheels.

Instead of being a simple straight cylinder, the crankshaft consists of (in a four-cylinder engine) four evenly spaced ‘throws’, which are attached to the bottom of the pistons by connecting rods.

These ‘throws’ are offset from the axis of the crankshaft, which is what creates the rotational energy.

What is a crankshaft

The crankshaft is attached to the engine by large bearings at either end. It connects to the flywheel, and through that, the clutch.

When the clutch is engaged, the rotational energy of the crankshaft is transmitted through the gearbox and on through the differential to the driveshafts, which are attached to the wheels, hence creating the car’s ability to move.

However, the crankshaft is an extremely complex and finely honed piece of engineering that doesn’t only consist of the four ‘throws’.

It also comprise numerous in-built weights and balances that are designed to keep vibration to a minimum as it rotates.

Any such vibration could be magnified and would cause damage to the bearings the crankshaft is mounted in, as well as the conrods and pistons.

In some cars that are equipped with a supercharger, a pulley is attached to the end of the crankshaft, which is then attached to the supercharger by a belt.

When the engine is running the crankshaft rotates rapidly, driving the pulley, which moves the belt, and then the pulley on the end of the supercharger.

This then operates the turbine in the supercharger, drawing in air and boosting the power the engine produces.