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, block and/or tackle:
“Being dismantled before our eyes are not just individual programs that politicians cite as too expensive but the whole idea that society has a stake in the well-being of children down the block and the security of families on the other side of town. Whether or not kids eat well, are nurtured and have a roof over their heads is not just a consequence of how their parents behave. It is also a responsibility of society—but now apparently a diminishing one.”
—Richard B. Stolley (20th century)
“Only he who can view his own past as an abortion sprung from compulsion and need can use it to full advantage in the present. For what one has lived is at best comparable to a beautiful statue which has had all its limbs knocked off in transit, and now yields nothing but the precious block out of which the image of one’s future must be hewn.”
—Walter Benjamin (1892–1940)
“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)