The crankshaft is the same on 4-stroke diesel engines and 2-stroke diesel engines. The shape may appear unusual at first.
Why won’t a simpler shape do the job? It’s all to do with balancing forces.
This top is evenly balanced, and it spins smoothly. Adding a weight unbalances it. How can it be made to spin properly again? One way is to put an identical weight on the other side. The first weight is balanced by the second weight. It acts as a counterweight.
Counterweights turn up in unusual places. Some systems can’t work without them.
Crankshaft counterweights keep the rotating components in balance and help the crankshaft turn as smoothly as possible.
The crankshaft turns because of the forces transmitted through the connecting rods. It must also be held in place. That’s done by bearings.
Different kinds of bearings have different designs. They reduce friction, and allow free movement.
The Crankshaft is held in the engine block by main bearings at points called journals. The crankshaft also needs to be located to stop lateral movement. This is done here by using flanges.
Between the connecting rod and the crankshaft are connecting rod bearings. They protect the spinning crankshaft at points called journals.
On the rear of the crankshaft of both the 4-stroke & 2-stroke diesel is a heavy flywheel.
It stores energy from the power stroke and gives it to the crankshaft to help it keep turning. In a 4-stroke, only one stroke in four delivers power. The energy from this one power stroke has to turn the crankshaft through the other three strokes. Without a flywheel the crankshaft would slow down and stop.
