Block and tackle rope through the block. The snatch block is also the load lifting pulley in certain arrangements. Block and tackle A block and tackle is a system of two or more pulleys with a rope or cable threaded between them, usually used to lift heavy loads. The pulleys are assembled together to form blocks and then blocks are paired so that one is fixed and one moves with the load. The rope is threaded through the pulleys to provide mechanical advantage that amplifies the force applied to the rope. Hero of Alexandria described cranes formed from assemblies of pulleys in the
Wire rope spooling technology its behaviour and affects lifespan. Fleet angle should be between 0.25° and 1.25°, depending on the rope construction. The fleet angle can be varied by moving the first sheave closer to or further away from the drum. If the sheave is too close to the drum, the fleet angle will be greater than 1.25°; if it is too far away, the fleet angle will be less than 0.25°. Sometimes it is not possible to achieve the optimum fleet angle. Where there is no space to rig a sheave the requisite distance from the drum, two additional spooling devices are available.