Some industrial and commercial buildings could reach heights of over 60 stories. Obviously, when these buildings are being constructed, they require equally tall cranes to be able to move the materials to the upper floors. There are cranes which have their own vehicle attached or other types that are operated from the back of trucks. Tower cranes are the biggest kinds offered on the market.
Tower cranes are stand-alone structures found as part of a major city's downtown skyline on high-rise building projects. Wherever new construction like for example apartment buildings and skyscrapers and commercial facilities like shopping center are being built, chances are a crane would be on site.
Kinds
The two major types of cranes can be differentiated by the manner in which their jib or boom lifts supplies. The jib is the metal frame which extends from the main section. On a flat tower crane, the jib remains horizontal as it lifts things. On a luffing type of tower crane, the jib could ratchet to downward or upward angles. The lifting capacity for both types can vary from 30 pounds to 10,000 lbs.
Body
The crane's body is composed of a mast. This is a vertical steel frame which is a combination of separate parts. In order to increase the overall height of the machinery, 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 referred to. The operator of the crane works from inside of the tower.
Lift
The crane uses a braided metal cord to lift materials. This cord extends out from a motor situated next to the control module to the end of the jib or boom. 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 tipping over when lifting heavy supplies.