Several commercial and industrial buildings could reach heights of over 60 stories. Apparently, when these buildings are being constructed, they require equally tall cranes to be able to move the materials to the higher floors. There are cranes which have their own vehicle attached or other kinds that are operated from the rear 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. Wherever new construction such as apartment buildings and skyscrapers and commercial facilities such as shopping center are being constructed, odds are a crane will be on site.
Kinds
The two key kinds of cranes can be distinguished by the manner in which their jib or boom lifts materials. The jib is the metal frame that extends from the main section. On a flat tower crane, the jib remains horizontal when it carries items. On a luffing kind of tower crane, the jib could ratchet to upward or downward angles. The lifting capacity for both kinds can vary from 30,000 lbs. to 10,000 lbs.
Body
The body of the crane is composed of a mast. This is a vertical steel frame that is a combination of separate sections. In order to increase the overall height of the equipment, parts are added. 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 operator of the crane works from inside of the tower.
Lift
To raise materials, the crane uses a braided metal cord. The cord extends all the way to the end of the boom or jib from a motor located 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 tower's opposite side. The counter jib has weights. These weights help to prevent the crane from tipping over when lifting heavy materials.