Some commercial and industrial buildings are capable of reaching heights of more than 60 stories. Apparently, while these buildings are being built, they need equally tall cranes to transport the materials to the higher floors. There are cranes that are operated from the rear of trucks or other kinds which have their own vehicle attached. Tower cranes are the biggest ones 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 such as skyscrapers or apartment buildings and commercial facilities like shopping center are being built, chances are a crane will be on site.
Kinds
There are two different types of cranes: boom crane or the jib crane. The jib is a metal frame that 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 can ratchet to downward or upward angles. The lifting capacity for both kinds could vary from 30,000 lbs. to 10,000 pounds
Body
The body of the crane is composed of a mast. This is a vertical steel frame which is a combination of individual sections. In order to increase the overall height of the machine, parts are added. 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 referred to. The operator of the crane works from inside of the tower.
Lift
In order to lift materials, 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 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 situated on the tower's opposite side. The counter jib holds weights. These weights help to prevent the crane from tipping over when raising heavy supplies.