Two nights ago, I watched the final portion of Ric Burns’ documentary film about New York. A significant portion of the three hours concerned the construction of the World Trade Center’s twin towers.
Australian cranes–“kangaroo cranes”–were placed atop the structures to lift the buildings’ steel elements into place. The cranes were equipped with hydraulics to lift themselves higher as the building grew.
How did the cranes get down once construction was completed? Were they lifted off the building by aircraft? Or are these cranes capable of climbing a quarter-mile to the ground?
Someone will be along to confirm, or not, but I’ve read that they are disassembled and the parts lowered down elevator shafts or the outside of the building before the building is completed.
I’d like to see a time lapse movie of the process if one is available on the net.
Yes, they are taken apart, piece by piece and lowered. I believe each piece was lowered by an arm and cable (sort of a mini crane) hanging out from the top. Of course, the mini crane might have hung around for additional use later as part of ongoing maintenance or removed piece by piece.