Some commercial and industrial buildings can reach heights of more than 60 stories. Obviously, when these buildings are being constructed, they require equally tall cranes to transport 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 biggest types available 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 such as shopping center are being built, chances are a crane would be on site.
Types
There are two different kinds 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 items. On a luffing type of tower crane, the jib could ratchet to upward or downward angles. The lifting capacity for both kinds could range from 30 pounds to 10,000 pounds
Body
The crane's body 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 wherever the desired height is, to the control module, which is a small room which has glass windows on all four sides or to the tower as it is also referred to. The crane driver works from inside of the tower.
Lift
To raise supplies, the crane uses a braided metal cord. The cord extends all the way to the end of the boom or jib 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 which 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 toppling over when heavy supplies are lifted.