Ancient Cranes

Ancient Crane

The heyday of used cranes in ancient times came under the Roman Empire, when construction activity soared and buildings reached enormous dimensions. The Romans adopted the Greek cranes and developed it further.

We are relatively well informed about their lifting techniques thanks to rather lengthy accounts by the engineers Vitruvius (De Architectura ) and Heron of Alexandria (Mechanica). There are also two surviving reliefs of Roman treadwheel cranes offering pictorial evidence, with the Haterii tombstone from the late first century AD being particularly detailed.

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 used cranes. 

At the temple of Jupiter at Baalbek, for instance, the architraves blocks weigh up to 60 tons each, and the corner cornices blocks even over 100 tons, all of them raised to a height of ca. 19 m above the ground.[3] In Rome, the capital block of Trajanos Column weighs 53.3 tons which had to be lifted at a height of ca. 34 m.

The simplest Roman crane, the Trispastos, consisted of a single-beam jib, a winch, a rope, and a block containing three pulleys. 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 quality 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.

The Polyspastos, when worked by four men at both sides of the winch, could already lift 3000 kg (3 ropes x 5 pulleys x 4 men x 50 kg = 3000 kg). In case the winch was replaced by a treadwheel, the maximum load even doubled to 6000 kg at only half the crew, since the treadwheel possesses a much bigger mechanical advantage due to its larger diameter. This meant that, in comparison to the construction of the Egyptian Pyramids, where about 50 men were needed to move a 2.5 ton stone block up the ramp (50 kg per person), the lifting capability of the Roman Polyspastos proved to be 60 times higher (3000 kg per person).

It is assumed that Roman engineers accomplished lifting these extraordinary weights by two measures: First, as suggested by Heron, a lifting tower was set up, whose four masts were arranged in the shape of a quadrangle with parallel sides, not unlike a siege tower, but with the column in the middle of the structure (Mechanica ).

 Second, a multitude of capstans were placed on the ground around the tower, for, although having a lower leverage ratio than treadwheels, capstans could be set up in higher numbers and run by more men (and, moreover, by draught animals).

 This use of multiple capstans is also described by Ammianus Marcellinus (17.4.15) in connection with the lifting of the Lateranense obelisk in the Circus Maximus (ca. 357 AD). The maximum lifting capability of a single capstan can be established by the number of lewis iron holes bored into the monolith. In case of the Baalbek architrave blocks, which weigh between 55 and 60 tons, eight extant holes suggest an allowance of 7.5 ton per lewis iron, that is per capstan.

 Lifting such heavy weights in a concerted action required a great amount of coordination between the work groups applying the force to the capstans.


Treadwheelcrane in France