The History Behind Cranes
For centuries, archaeologists and historians have been baffled by how Stonehenge was built. The largest of the Sarsen stones transported to Stonehenge weighs 50 tons — which means that transportation by boat would have been impossible. Legend holds that ancient druids levitated the stones into place with their eldritch rituals.
The truth may be a bit less exciting, but just as interesting. The prevailing theory is that the stones were literally dragged using an intricate series of sledges, ropes, ramps, and levers.
The stones of the Pyramids of Giza were likely hoisted into place in a similar fashion. The “regular” slabs that tourists see on the outside surface of the pyramids are 3 tons each, but the biggest supporting slabs weigh up to 70 tons. Think that’s impressive? The Colossi of Memnon each weighed 700 tons each. By comparison, most common tower cranes today have a lifting capacity of only 12 to 20 tons, and most construction cranes go up to 300 tons.
If you wanted to lift a 700-ton load, you’d need something like a Liebherr Mobile Crane with a capacity of 1,200 metric tons.
For thousands of years, people have used innovative ways of lifting really heavy objects and bringing them where they’re needed. As demonstrated at Stonehenge, the Pyramids of Giza, and countless ancient sites around the world, the history of the crane is closely aligned with the history of the limits of man’s strength.
The History of The Crane
The birth of the crane is inextricably tied with the birth of the pulley — first devised by ancient Mesopotamians as early as 1500 BC for hoisting water. The first compound pulleys were created by Archimedes of Syracuse around 287 – 212 BC, which he used to lift an entire war ship, along with its crew.
The advent of the compound pulley contributed enormously to the development of mechanical cranes. A single man pulling on a “Pentaspostos” (a crane with five pulleys), for example, has a mechanical advantage of 5:1. In other words, by exerting a force of 50 lbs, he can pull 250lbs.
Of course, the compound pulley has its downsides. It’s stationary, immobile, temperamental, and has slow lifting speeds. In fact, the more pulleys there are, the slower the lifting speed becomes. More rope has to be pulled for a load to travel the same distance it would in a crane with fewer pulleys. Also, friction makes a compound pulley with more than 5 parts inoperable.
These insurmountable drawbacks led to the development of the winches and capstans used by the Romans to build their temples. The power of circular rotation caught on quickly, which naturally led to the increased use of gearworks.
The treadwheel crane, which made use of compound pulleys as well as winches and capstans, was the last in a long line of hand-powered cranes. A single man operating a treadwheel crane has a mechanical advantage of 30:1. Invented by the Romans, treadwheel cranes were in use until the end of the 17th century, and were absolutely essential at harbors and in cathedral construction.
The History of The Hydraulic Crane
While cranes remained hand-powered for centuries, hydraulics had been steadily improving. With a history that stretches back to Ancient Egypt, China, and Greece, water-powered machines (mostly water wheels) had been in use for thousands of years as well. Ancient irrigation systems, like the aqueducts developed by the Romans, relied on simple hydraulic technology, like siphoning and hushing in hydraulic mining.
But it was not until the 15th century that Blaise Pascal studied fluid hydrodynamics and hydrostatics, ushering in a new understanding of hydraulic principles like fluid density, pressure, and incompressibility. He invented the hydraulic press, the building block of modern hydraulics.
Much later in the 19th century, the rise of ironworks and industrialization meant that cranes finally made the big switch from wood to iron. The first cast iron crane was constructed in 1834, which was also the year that wire rope was invented. And in 1851, hand-powered cranes finally began running on steam power — the first step toward a truly hydraulic crane.
Today, hydraulic cranes are built with better specifications and with better materials than cranes in the 1800s, but rely on the same mechanical and hydraulic principles developed centuries ago.
Modern hydraulic cranes are filled with an incompressible fluid, usually oil, that perfectly transfers pressure between pistons. As shown in the diagram above, a master piston (which requires less force to move) is pushed down against a fluid, which pushes back up on the slave piston (which requires more force to move).
Variations on this simple leveraging of fluid movement have allowed us to engineer behemoths like the Liebherr Mobile Crane.
The Future of Cranes?
Modern hydraulic cranes can move up to 1,200 tons, and it’s hard to imagine that there’s any load in the world that would ever exceed that limit. But, as history has often shown, there’s always room for improvement.
H. Brown, Inc. serves Lafayette, Opelousas, Lake Charles, Alexandria, Baton Rouge, and beyond. We have cranes up to 450 tons, hydraulic trailers up to 500 tons, lowboys up to 220 tons, gantries up to 900 tons and slide systems up to 600 tons. Because H. Brown, Inc. handles such a wide variety of lifting, hauling and rigging jobs, we have to be resourceful to accomplish our work safely and on budget. And that’s what we do, every day.