The crankshaft is a basic element of the engine, which determines its correct operation. The piston-crank system is responsible for changing the reciprocating motion into rotary motion, and this process is called obtaining torque. Starting the crankshaft causes the exhaust gases to press on the bottom of the piston, which is why it is pushed out, and this process sets the entire mechanism in motion.

The crankshaft consists of several basic elements:

• main journals,
• crank pins,
• counterweight,
• flywheel disc,
• crank arm connecting the journals.

The crankshaft should be highly durable, because it is exposed to various forces: pressure, torsion, crushing or stretching. The material from which the crankshafts are made is also important, it should be durable and resistant to constant vibrations, because this element is responsible for the rigidity of the engine, and therefore its proper operation. The most common material used for the production of crankshafts is cast iron and forged steel, but it should be noted that forged shafts are much stronger than cast ones.

Crankshafts available on the market may differ in length and slightly in shape. When selecting the right crankshaft, the number of engine cylinders and the firing order are of particular importance.

Crankshaft damage most often occurs due to:

• lack of proper lubrication,
• improper assembly,
• improperly functioning crankshaft sensor.

The correct operation of the crankshaft also means the correct operation of the engine, which is why it is so important to periodically check the efficiency of this element. In this way, we will avoid very serious failures and, consequently, very expensive repairs.