Friday, February 4, 2011

"The sky is the limit: human powered cranes and lifting devices" (FLR; JEC)

From Low-tech Magazine:

Erecting the vatican obelisk From the earliest civilisations right up to the start of the Industrial Revolution, humans used sheer muscle power, organisation skills and ingenious mechanics to lift weights that would be impossible to handle by most power cranes in operation today.
The most powerful hand crane in history multiplied the force of its operator 632 times
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.
Liebherr crawler craneThe 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). Today, to lift a weight of 50 to 100 tonnes to these heights, you need a crane like this.

Occasionally, our forefathers lifted even heavier stones. The gravestone of Theoderic the Great in Ravenna (around 520 AD) is a 275 tonne stone block that was lifted to a height of 10 metres. The temple dedicated to Pharaoh Khafre in Egypt is made up of monolithic blocks weighing up to 425 tonnes. The largest Egyptian obelisk weighed more than 500 tons and stands more than 30 metres tall, while the largest obelisk in the Kingdom of Axum in Ethiopia (4th century AD), raised up to a similar height, weighed 520 tonnes. The Colossi of Memnon, two statues of 700 tonnes each, were erected to a height of 18 metres and the walls in the Roman Baalbek temple complex (1st century BC) contain almost 30 monoliths weighing 300 to 750 tons each.

Liebherr mobile crane 1200 tonnes Only the most powerful contemporary cranes could handle stones of this weight (see the picture on the left, specifications here).

Raising construction materials to impressive heights seemed to be no problem either. The Alexandria lighthouse (3rd century BC) stood more than 76 metres (250 feet) tall. The Egyptian pyramids rise up to 147 metres. During the Middle Ages some 80 large cathedrals and around 500 large churches were built with a height of up to 160 metres - out of reach for all but the most recent top model crawler cranes (picture above, right)....MORE