when high rise buildings are built a crane is erected to lift iron and cement up. How do they erect these cranes?
this is not the answer i expected
They are erected onto themselves..
Like an Electra set, they are dismantled then put back together. They are transported in sections along with the counter balance weights. The most solid part is the cab.
Construction cranes are erected on site. They are usually assembled on the ground with small cranes, then lift themselves up. The erection sequence is carefully figured, so minimal other equipment is needed. For conventional cranes that are permanent and thus only assembled once, portable cranes are used to erect them. Still, generally pretty much on the ground. Some have counterbalances that are permanently fixed, others have a rail type mechanism that moves in and out.
