Several 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 move the supplies to the upper floors. There are cranes that are operated from the back of trucks or other kinds that have their own vehicle attached. Tower cranes are the biggest types available 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 skyscrapers or apartment buildings and commercial facilities like shopping center are being constructed, chances are a crane will be on site.
Kinds
There are two different kinds of cranes: jib crane of the boom crane. The jib is a metal frame that extends from the main section. On a flat tower crane, the jib remains horizontal as it carries things. On a luffing type of tower crane, the jib can ratchet to downward or upward angles. The lifting capacity for both kinds can vary from 30 pounds to 10,000 lbs.
Body
The body of the crane is composed of a vertical steel mast which is composed of individual [parts. The sections are added to increase the overall height of the machine. The mast extends upward to where the desired height is, to the control module, that is a small room that has glass windows on all four sides or to the tower as it is also called. The driver of the crane works from inside of the tower.
Lift
In order to lift 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 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 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 toppling over when heavy materials are carried.