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:
“When the landscape buckles and jerks around, when a dust column of debris rises from the collapse of a block of buildings on bodies that could have been your own, when the staves of history fall awry and the barrel of time bursts apart, some turn to prayer, some to poetry: words in the memory, a stained book carried close to the body, the notebook scribbled by hand—a center of gravity.”
—Adrienne Rich (b. 1929)
“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)