(1) the working principle of truck crane and construction crane is the lever principle.
(2) the working principle of crane (bridge crane) is the principle of bridge string.
Or you could say it's a parabola.
2. Crane refers to a certain range of vertical lifting and horizontal lifting of heavy lifting machinery.
Also known as a crane.
Cranes are usually divided into boom crane and bridge crane according to the structure.
Boom crane: including tower crane, gantry crane, floating crane, self-propelled crane, mast crane composed of mast and boom, wall crane running along the wall and deck crane mounted on the ship deck, etc..
(2) bridge crane: including bridge crane, gantry crane, carrier bridge and cable crane (with the load cable instead of the bridge).