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Ancient Cranes, Timeless Reason
Ancient Cranes, Timeless Reason

Ancient Cranes, Timeless Reason

Human ingenuity is incredible. Love it. For thousands of years, people have made cranes that could lift enormous weights, way beyond what we could lift unaided. Physics and math extend the power of human mind and muscle.

In “The sky is the limit: human powered cranes and lifting devices,” Kris De Decker writes:
The most common tower crane used in construction today has a lifting capacity of some 12 to 20 tonnes. For quite a few construction projects in ancient history, this type of crane would be completely inadequate.

The majority of stones that make up the almost 140 discovered Egyptian pyramids have a weight of “only” 2 to 3 tonnes each, but all of these structures (built between 2750 and 1500 BC) also hold stone blocks weighing 50 tonnes, sometimes more. The temple of Amon-Ra at Karnak contains a labyrinth of 134 columns, standing 23 metres (75 feet) tall and supporting crossbeams weighing 60 to 70 tonnes each. The 18 capital blocks of Trajan’s column in Rome weigh more than 53 tonnes and they were lifted to a height of 34 metres (111 feet). The Roman Jupiter temple in Baalbek contains stone blocks weighing over 100 tonnes, raised to a height of 19 metres (62 feet).

The job [of moving the Vatican obelisk] was done using a wooden construction 27.3 metres tall, ropes up to 220 metres long, 40 capstans, 800 men and 140 horses (when lowering the obelisk the workforce consisted of 907 men and 75 horses). While the whole undertaking took more than a year – including the transport of the obelisk (on rollers) and the assembly of the tower, the capstans and other lifting machinery – the stone was erected in just 13 hours and 52 minutes. As a result of this successful operation, many more obelisks were moved around Rome, one of these weighing 510 tonnes.…
[A] 60 ton crane was built for the new docks at Keyham, which could lift loads five times heavier up to heights of 60 feet (18 metres) and over a circle 104 feet (32 metres) in diameter.

It is this “colossal crane,” probably the most powerful hand driven crane ever built, that is described in detail by Fairbairn:
The chain passes round 4 pulleys, two moveable and two fixed, in the end of the jib. It is then conducted down in the interior of the jib over three rollers to the barrel, which is also in the tube near the ground. On each side of the crane a strong cast iron frame is fixed for receiving the axles of the spur wheels and pinions.

Four men, each working a winch of 18 inches radius, act by two 6 inch pinions upon a wheel 5 feet 3.75 inches diameter, this in turn moves the spur wheel, 6 feet 8 inches diameter, by means of an 8 inch pinion, and on the axle of the former the chain barrel, 2 feet in diameter, is fixed.

Hence the advantage gained by the gearing will be W/P = 18 x 63.75 x 80 / 6 x 8 x 12 = 158 or taking the number of cogs in each wheel W/P = 18 x 95 x 100 / 12 x 9 x 10 = 158 and as this result is quadrupled by the fixed and moveable pulleys, the power of the men applied to the handles is multiplied 632 times by the gearing and blocks. Two men are sufficient to move round the crane with 60 tonnes suspended from the extreme point of the jib.
A mechanical advantage of 632 to 1 means that each of the four men had to apply a force of only 23.7 kilograms in order to lift a weight of 60 tonnes – and this while operating a winch instead of a more efficient treadwheel.

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