A block and tackle is a system of two or more pulleys with a rope or cable threaded between them, usually used to lift or pull 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, or reeved, through the pulleys to provide mechanical advantage that amplifies that force applied to the rope.
Hero of Alexandria described cranes formed from assemblies of pulleys. Illustrated versions of Hero's "book on raising heavy weights" show early block and tackle systems.
Read more about Block And Tackle: Overview, Mechanical Advantage, Example Block and Tackle Configurations, Friction, Rigging Methods, More On Mechanical Advantage
Famous quotes containing the words block and/or tackle:
“Painting consumes labour not disproportionate to its effect; but a fellow will hack half a year at a block of marble to make something in stone that hardly resembles a man. The value of statuary is owing to its difficulty. You would not value the finest head cut upon a carrot.”
—Samuel Johnson (1709–1784)
“Play with your fancies: and in them behold
Upon the hempen tackle ship-boys climbing;
Hear the shrill whistle which doth order give
To sound confused; behold the threaden sails
Borne with th’ invisible and creeping wind.”
—William Shakespeare (1564–1616)