Styled like colossal human hamster wheels, these cranes allowed huge loads to be hoisted with ease.
The treadwheel crane was a wooden, human-powered lifting and lowering device invented in Ancient Rome. It was used in construction and industry for lifting all manner of materials and produce.
Its creation was a revelation at the time, granting a single person the ability to lift roughly 3,000 kilograms (6,600 pounds) of weight, rather than a completely manual 50 kilograms (110 pounds). As such, while it could take 50 workers to haul a 2.5-ton block of stone during the construction of Egypt’s pyramids, by using a treadwheel crane, the equivalent load could be lifted in Roman construction projects by just three.
Key to this was the huge mechanical advantage granted by the large-diameter treadwheel; it acted as a force amplifier, with the low force input of the treadwheel workers increased dramatically at the output end.
A typical system placed two peddlers side by side in a large, tracked wooden wheel, itself turning around a central shaft. As the wheel was set in motion by the pacing of the workers, it would rotate the central shaft, which in turn would draw in or let out a connected pulley.
The pulley extended out along the crane’s lifting bar and then down to the floor, where objects could be either loaded or unloaded.
Despite its fairly crude design, the treadwheel crane remained in widespread use right up to the end of the 18th century.