How works Crankshaft? Crankshaft Design and Components



Combustion of the fuel-air mixture within the engine produces power. This power is transformed into rotary movement of the crankshaft. The linear motion of the pistons is converted by way of the rod into at and is then passed to the flywheel.

Crankshaft Diagram

The crankshaft has got to withstand considerable loads during this process. On the one hand it's subjected to severe bending and torsional stress. Further loads arise from torsional vibration, because the rotary movement of the crankshaft is consistently being abruptly accelerated and decelerated. The bearings also are subject to a high degree of wear and tear .


To be ready to withstand wear and therefore the strain of rotary movement, crankshafts got to have a troublesome surface and a tough core. For this reason crankshafts are often forged. Alloyed heat-treated steel or nitrided steel is employed as staple . The crankshaft journals also are surface-hardened.

A crankshaft comprises the subsequent components:

Main journals

Crank pins

Crank webs


Main journals run within the main bearings and define the axis of rotation of the shaft. The connecting rods are connected to the crank pins. Crank webs connect the crank pins to the most journals. The counterweights provide balancing and are attached to the webs.


The design of the crankshaft is decided by the firing order of the engine, the amount of cylinders, the planning of the engine, the dimensions of the stroke and therefore the number of crankshaft bearings.

Height-adjustable crankshaft mounting – using an eccentrically mounted crankshaft bearing for instance – makes it possible to realize variable compression. The advantage of variable compression is that fuel consumption are often reduced by up to 25 per cent within the part load range.


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