Some industrial and commercial buildings can reach heights of more than 60 stories. Apparently, while these buildings are being built, they need equally tall cranes to move the materials to the higher floors. There are cranes which are operated from the rear of trucks or other kinds which have their own vehicle connected. Tower cranes are the biggest ones offered 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 skyscrapers or apartment buildings and commercial facilities like for instance shopping center are being built, chances are a crane would be on site.
Kinds
The two major types of cranes can be distinguished by the way in which their boom or jib raises 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 type of tower crane, the jib could ratchet to upward or downward angles. The lifting capacity for both types could range from 30 pounds to 10,000 lbs.
Body
The crane's body is composed of a vertical steel mast that is composed of individual sections. The sections are added to increase the overall height of the equipment. The mast extends upward to where the desired height is, to the control module, that is a small room which has glass windows on all four sides or to the tower as it is also called. The crane operator works from inside of the tower.
Lift
In order to lift materials, the crane uses a braided metal cord. The cord extends all the way to the end of the jib or boom from a motor located near 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 which holds the cord becomes balanced by a counter jib located on the tower's opposite side. The counter jib has weights. These weights help to prevent the crane from tipping over when raising heavy materials.