CRANES (MACHINE HISTORY) 

ORIGINS OF THE MODERN DAY CRANE

A crane is a lifting machine equipped with a winder, wire ropes or chains and sheaves that can be used both to lift and lower materials and to move them horizontally. Put in basic terms, it uses one or more simple machines to create mechanical advantage to enable the movement of loads beyond the normal capability of a human. The principles of operation of today's CRANE EQUIPMENT is taken for granted, however, we thought you might be interested in learning a bit about the history of the Crane and its development into the modern age of technology.

The Greeks and Romans were very creative and innovative in the area we now call mechanics. The Greeks invented some simple machines, and put them together in novel ways to make complex machines, from the compound pulley to the Antikythera mechanism. The Romans refined Greek CRANE EQUIPMENT technology and put it to good use.

CRANE EQUIPMENT CRANE EQUIPMENT ANCIENT ROMAN TECHNOLOGY

Heavier CRANE EQUIPMENT types featured five pulleys (Pentaspastos) or, in case of the largest one, a set of three by five pulleys (Polyspastos) and came with two, three or four masts, depending on the maximum load. The Polyspastos, when worked by four men at both sides of the winch, could lift 3000 kg (3 ropes x 5 pulleys x 4 men x 50 kg = 3000 kg). However, numerous extant Roman buildings which feature much heavier stone blocks than those handled by the Polyspastos indicate that the overall lifting capability of the Romans went far beyond that of any single crane.

In the years just before Christ was born, the chief engineer of the Roman world was a man named Marcus Vitruvius Pollio. Vitruvius began his career as an architect and engineer under Julius Caesar. Later he took charge of Octavian's siege engines. Toward the end his life, he wrote a ten-volume account of known technology under Octavian's patronage. CRANE EQUIPMENT for raising heavy weights was described in the writings of Marcus Vitruvius who is the first Roman architect to have written surviving records of his field.

		The Pentaspastos ("Five-pulley-crane")was a medium-sized Roman crane. The Pentaspastos consisted of a single-beam jib, two winches, a rope, and a block containing five pulleys. Having thus a mechanical advantage of 5:1, the two men working the winch could raise loads of ca. 450 kg, assuming that 50 kg represent the maximum effort a man can exert over a longer time period.
An artist's drawing of a Pentaspastos
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Reconstruction of a 10.4m high Roman Polyspastos at Bonn, Germany

Greco-Roman CRANE EQUIPMENT was used for construction work and possibly to load and unload ships at their ports. Most cranes were capable of lifting about 6-7 tons of cargo, and according to a relief shown on Trajan's column were worked by tread-wheel.

Artists renditions of ancient Roman cranes models
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An artist's drawing of a Trispastos
		The simplest Roman CRANE EQUIPMENT, the Trispastos, consisted of a single-beam jib, a winch, a rope, and a block containing three pulleys. Having a mechanical advantage of 3:1, it has been calculated that a single man working the winch could raise 150 kg (3 pulleys x 50 kg = 150), assuming that 50 kg represent the maximum effort a man can exert over a longer time period. If more lift was needed, the use of two or more 3- or 5-pulley sets, with different gangs working them were used. The Trispastos was operated by man power through a capstan and a large wheel rotating on a horizontal axis, a kind of treadmill. It is unclear if this was used to turn the crane or merely to operate the tackle. It is quite possible that both operations occurred at the same time. If this is the case, the Romans knew the principle of the modern hosting engine. What they lacked was the mechanical power of modern day crane equipment.

While these earlier forms of CRANE EQUIPMENT bear little resemblance to modern day technology, the use of these rudimentary lifting mechanisms enabled remarkable achievements to be performed in the construction of buildings and monuments that still survive today.

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