Compound pulley (block and tackle)
Polea compuesta (polipasto)
- Date
- c. 250 BCE · confidence medium
- Place
- Syracuse, Sicily, Italy
- Credited to
- Archimedes (tradition); Aristotelian Mechanics
- People
- 👤 Arquímedes287 BCE–212 BCE
- Field
- Tools
What it is
A system of several fixed and movable pulleys that multiplies the force applied to a rope in proportion to the number of rope segments. A formalisation of mechanical advantage and the theory of simple machines.
Plutarch tells the anecdote of Archimedes moving a loaded ship with a block and tackle.
What it led to
- High-capacity cranes for monumental architecture
- Ship rigging that allowed larger sails with smaller crews
- Statics as a science (the law of the lever, centre of gravity)
- Mechanically tensioned torsion artillery
Built on
- Plant-fibre cordage (linen rope)c. 7200 BCE
- Euclidean axiomatic geometryc. 300 BCE
- Archimedes principle and law of the leverc. 250 BCE
- Simple pulley
- Fibre rope
- Euclidean geometry
Made possible
- Catapult and torsion ballista399 BCE
- Toothed gearc. 270 BCE
- Roman treadwheel cranec. 100 BCE
- Lewis (stone block lifting device)c. century I a.C.
- Quick-erecting mobile tower crane1949
- Roman crane (polyspastos)
- Naval rigging (tackle)