Comments about technological history, system fractures, and human resilience from James R. Chiles, the author of Inviting Disaster: Lessons from the Edge of Technology (HarperBusiness 2001; paperback 2002) and The God Machine: From Boomerangs to Black Hawks, the Story of the Helicopter (Random House, 2007, paperback 2008)

Friday, October 16, 2015

How to Park Your Super-Crane

People who are following news connected to the destruction caused by the Liebherr L11350 super-crane that fell backward at the Grand Mosque in Makkah, KSA, may have wondered what such a crane would have looked like had the contractor (Saudi Binladin Group) stowed the machine in case of bad weather, as directed by the manufacturer. 

So here's a photo of what this particular model looks like when safed. Except for the lack of a back mast to the detached counterweight, this Liebherr L11350 is rigged similarly to the crane at Makkah, which was an "SDW" arrangement (Photo, Mace Ltd):

The thin, red and white structure on the far left is the luffing-fly jib, labeled in my previous post and diagram. Its latticed counterpart on the right side is the derrick mast. 

Normally the jib would be way up in the air, topping the boom, but it can be angled down with winches and pulleys that allow the jib angle to be changed (in crane language, "luffed") from the operator's seat - in this case, pointed so far down that the tip of the jib touches the ground. 

We don't know why the crane parked on the plaza by the Massa wasn't routinely parked this way. Lowering the boom and jib might have needed restoration of counterweights that had been removed, along with the need to round up operators and riggers rated to use this machine. Maybe bringing the jib to the ground would have interfered with pedestrian traffic. In general, I'm guessing, it seemed easier to leave the main boom and jib at a near-vertical angle. 

But easy doesn't mean safe, as I wrote in Inviting Disaster

If there's interest I'll post on the amazing, if narrow, niche of super-cranes. 

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