A Yamaha crankshaft axis via a connecting rod connected to the Pistons moving up and down. As the piston moves the stool of the crankshaft is pushed up and goes the crankshaft turning. There are countless shapes and sizes, depending on the application and the manufacturer and sometimes a crank not even recognizable as such because it also can be mounted. The crankshafts of Yamaha outboard motors for example look completely different than that of a inboardmotor.
A crank is an important outboard part in almost everything a motorized movement. The axle must be performed very carefully because there are large forces on. In addition, some cranks a very high rotation speed leaving a small (such as a curve crankshaft) construction or Assembly error can lead to lockups.