Pair and spare dating
Having thus 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.
Heavier crane 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.
There are also two surviving reliefs of Roman treadwheel cranes, with the Haterii tombstone from the late first century AD being particularly detailed.
The simplest Roman crane, the trispastos, consisted of a single-beam jib, a winch, a rope, and a block containing three pulleys.
Mini-cranes are also used for constructing high buildings, in order to facilitate constructions by reaching tight spaces.
Finally, we can find larger floating cranes, generally used to build oil rigs and salvage sunken ships.
Sizes range from the smallest jib cranes, used inside workshops, to the tallest tower cranes, used for constructing high buildings.
Around the same time, block sizes at Greek temples began to match their archaic predecessors again, indicating that the more sophisticated compound pulley must have found its way to Greek construction sites by then.
The heyday of the crane in ancient times came during the Roman Empire, when construction activity soared and buildings reached enormous dimensions.
For the next 200 years, Greek building sites witnessed a sharp reduction in the weights handled, as the new lifting technique made the use of several smaller stones more practical than fewer larger ones.
In contrast to the archaic period with its tendency to ever-increasing block sizes, Greek temples of the classical age like the Parthenon invariably featured stone blocks weighing less than 15-20 metric tons.
A crane is a type of machine, generally equipped with a hoist rope, wire ropes or chains, and sheaves, that can be used both to lift and lower materials and to move them horizontally.