What is a meathod of tower crean erection

Question

parts name assembly drawing

Answer 1

1.)  Some of the smaller units are self erecting and self dismantling.  Essentially the boom (swing arm) folds like an accordian door with three hinge points.  The tower has a bottom hinge and folds over and then lays down.  This type of tower crane must be erected exterior of the building so all of this folding and hinging can occur.

2.)  Some are erected to final height at the beginning of the project, and they can either be built into the building or just outside of the building.  The boom is positioned high enough so that it will clear the top of the building when finished, and high enough so that it clears surronding buildings also.  The tower is erected a piece at a time (about 20' sections) until the proper height is reached.  A large mobile( on wheels) crane is used to hoist the pieces.  

A pivot section is added on top of the tower, and then the boom and counter weight extenions.  Some times the boom has to be inserted in more than one section, adding counter balancing sections on the opposite side.  The boom is light enough and strong enough that some amount of moment is managed through the tower connections until the full boom and counterweights are all in place and the boom becomes balanced.  The process is just the opposite to remove it.    When the crane is erected in the building footprint and the building built around it; sometimes the crane to remove it must be really big; as it must reach up and over the shoulder of the building and still get above the standing tower high enough to lift the pieces off.

3.)  A variation on the theme is a jumping tower crane.  It usually starts with about about 100' of tower.  There is an apparatus in the tower section just below the pivot section that allows additional tower sections to be slid into a jacked up gap.  The tower crane then lifts its own tower section onto the apparatus and this new section is inserted.

This procedure is repeated as the building rises.  This keeps the operator closer to the work so he or she can see it better.  This crane is dismantled the same as #2 above.  

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