Some industrial and commercial buildings are capable of reaching heights of over 60 stories. Apparently, while these buildings are being built, they need equally tall cranes to be able to move the supplies to the upper floors. There are cranes which have their own vehicle connected or other kinds that are operated from the back of trucks. Tower cranes are the largest kinds on the market.
Tower cranes are stand-alone structures found as part of a major city's downtown skyline on high-rise building projects. When new construction like for example 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 could be distinguished by the way in which their boom or jib 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 items. On a luffing kind of tower crane, the jib can ratchet to downward or upward angles. The lifting capacity for both kinds can range from 30,000 lbs. 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 machinery, sections are added. The mast extends upward to wherever 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 crane operator works from inside of the tower.
Lift
In order to lift supplies, the crane utilizes 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 situated 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 has weights. These weights help to prevent the crane from tipping over when heavy materials are lifted.