Some commercial and industrial buildings can reach heights of over 60 stories. Obviously, when these buildings are being built, they require equally tall cranes to be able to move the materials to the higher floors. There are cranes that have their own vehicle connected or other kinds which are operated from the back of trucks. Tower cranes are the largest ones available on the market.
Tower cranes are the stand-alone structures that are often found on high-rise building projects. Normally, they are part of a major city's downtown skyline. When new construction like for example apartment buildings and skyscrapers and commercial facilities like shopping center are being constructed, odds are a crane will be on site.
Kinds
The two major types of cranes can be distinguished by the manner in which their boom or jib raises supplies. The jib is the metal frame that extends from the main section. On a flat tower crane, the jib remains horizontal as it lifts things. On a luffing kind of tower crane, the jib can ratchet to upward or downward angles. The lifting capacity for both kinds can range 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 equipment, sections are added. The mast extends upward to wherever 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 called. The crane driver works from inside of the tower.
Lift
In order to lift materials, the crane uses 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 that holds the cord becomes balanced by a counter jib located on the tower's opposite side. The counter jib holds weights. These weights help to prevent the crane from toppling over when heavy supplies are carried.