What does the crane mean?
A crane is a large arm that is hoisted on a crane. (it is also called a barpole.) the process of raising or moving down the crane is called a variation.
The variable amplitude is the Angle of the main arm, which is called the oil cylinder with the oil cylinder on top of the main arm. The main arm lifted up and called the amplitude, and the main arm fell down and put a flat call.
The variation is the distance between the hub and the hook, the Angle of the big arm.
