• How Cranes Built Civilization


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How Cranes Built Civilization: From the Ancient World to the Modern Era

Cranes are a common sight in any growing city. The ability to vertically lift steel, stone, and other heavy construction materials is necessary to build not only office-filled, Denver skyscrapers but elaborate architecture across the globe such as Fisht Olympic Stadium in Sochi and Gaudi's cathedral, Sagrada Familia, in Barcelona, Spain. Did you know that these critical machines started off as glorified water irrigation systems in Ancient Egypt?

We trace this essential building technology from its humble beginnings as a water-carrying pulley to stone-lifting towers.

How the Ancients Lifted, Moved, and Constructed

Most lifting techniques began as either human powered, usually by slaves, or animal powered. The Ancient Egyptians used ramps to move, for example, the 2.3 million seven-ton stone blocks that comprise the Great Pyramid of Giza. Anywhere from 20,000 to 50,000 men built the 6.5-million-ton pyramid over the course of 23 years, meaning they set a stone every 2.5 minutes every day of the week starting in 2540 B.C. The result was a 449.5-foot-high pyramid with a base the size of 10 football fields.

Ancient Egyptians also used a shaduf, a vertically supported beam with a heavy weight on one end and a bucket on the other, to transport water from the Nile to farms for irrigation and to homes for drinking.

Ancient Greeks invented the pulley system in the 8th century B.C. to get water out of wells, and then started to use pulleys to build temples commemorating their gods in the late 6th century B.C.

Just like the Ancient Egyptians relied on slave labor and donkeys to move stones for pyramids and water for farming, the Greeks invented an early rendition of a crane that relied on the strength of pack animals and humans. The Greeks anchored these wood- and-rope contraptions into the ground with large stakes. By 515 B.C., they started stacking stones on top of their temples using tongs and Lewis irons.

How Romans Built an Empire

Motivated to meet the needs of their expanding empire, Romans imitated the Greeks' crane and added some advancements. The Romans developed a jib crane, combining a rope over a block of pulleys, a winch, and a jib. A slave would walk within the wheel of larger jib cranes and create enough momentum to lift the load. The Romans also built lift towers, arguably the earliest ancestors of the common tower cranes we use today.

In the 4th century B.C., the Romans invented compound pulleys. This game-changing technology added more wheels to the system in order decrease the lifting resistance. Compound pulleys had anywhere from three to five wheels, allowing them to lift substantially more with less effort. For example, a single pulley had a 2-to-1 lift weight to pulling force ratio. By comparison, a triple-pulley system would allow someone to lift three times what a single pulley could lift.

The Romans also mobilized cranes as they expanded their empire. Setting up and breaking down cranes, the Romans built cities across Europe and Northern Africa. They created extensive, water-bearing aqueducts. The longest, the Claudian aqueduct, had a 43-mile-long channel. They built amphitheaters to entertain thousands of people as far north as Scotland. After major victories, they constructed triumphal arches. They also erected tenement buildings to accommodate their densely populated cities.

Churches, Castles and Cargos: Cranes in the Middle Ages

As with everything, technology suffered with the fall of Rome. Crane systems reappeared in 14th-century England and 13th-century France.

It wasn't until the Middle Ages that people built treadwheel cranes for loading cargo onto ships. These cranes also facilitated the construction of medieval castles and cathedrals. Two critical inventions helped to level out the lifting process in these other crude machines: the windlass (a crank-powered cylinder) and the flywheel made the lifting process less clunky.

Because there wasn't a considerable supply of slave labor, the treadwheel crane had to have a greater strength-to-resistance ratio. A typical example of a treadwheel crane could lift 14 times the force put into it, or 70 times more than a pulley. It did, however, have its drawbacks. These brakeless, slow-moving models required men or beasts of burden to walk a long distance to create enough leverage to lift a load. They also required two men to power it, one of which had to be inside the wheel. If the load got away from the worker, the guy in the wheel would be crushed.

From Steam to Combustion: Modernizing Cranes

The Industrial Revolution brought steam-powered cranes that were typically featured on trolleys, railways, and barges. Made of cast iron and steel, these cranes had a cistern to counterbalance the cargo that the jib lifted.

As availability of coal diminished in the 1970s, more and more cranes converted to diesel power. Today, crane companies can build you a customized mobile crane with an internal combustion engine and hydraulic systems capable of lifting 120 tons to overhead cranes utilizing electric motors that can lift in excess of 500 tons. Overhead cranes are now prevalent in virtually any industrial manufacturing facility around the world. From their origins in the ancient world to their role in modern material handling, cranes have established their place in history.