There are several industrial and commercial buildings that now exceed 60 stories or more. These buildings all require tall cranes to help move the materials to the higher floors. There are cranes that have their own vehicle attached or other types which are operated from the back of trucks. Tower cranes are the largest kinds on the market.
Tower cranes are stand-alone structures seen as part of a major city's downtown skyline on high-rise building projects. When new construction like for instance skyscrapers or apartment buildings and commercial facilities like shopping center are being constructed, odds are a crane would be on site.
Kinds
The two major kinds of cranes could be distinguished by the way in which their boom or jib lifts supplies. The jib is the metal frame that extends from the main section. On a flat tower crane, the jib remains horizontal as it carries items. On a luffing kind of tower crane, the jib can ratchet to downward or upward angles. The lifting capacity for both types could vary from 30 pounds to 10,000 lbs.
Body
The crane's body is composed of a vertical steel mast which is composed of separate sections. The parts are added to increase the overall height of the equipment. The mast extends upward to where the desired height is, to the control module, which is a small room that has glass windows on all four sides or to the tower as it is also called. The crane driver works from inside of the tower.
Lift
In order to raise supplies, the crane utilizes a braided metal cord. The cord extends all the way to the end of the jib or boom from a motor situated next to the control module. There is a pulley system located at the end of the jib, through which the cord is positioned and lowered down. The jib that holds the cord becomes balanced by a counter jib situated on the opposite side of the tower. The counter jib holds weights. These weights help to prevent the crane from toppling over when heavy supplies are lifted.