Some industrial and commercial buildings can reach heights of over 60 stories. Obviously, when these buildings are being built, they need equally tall cranes to transport the materials to the upper floors. There are cranes which are operated from the back of trucks or other kinds that have their own vehicle attached. Tower cranes are the largest ones 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 apartment buildings and skyscrapers and commercial facilities like shopping center are being built, odds are a crane would be on site.
There are two different kinds of cranes: jib crane of the boom crane. The jib is a metal frame which extends from the main section. On a flat tower crane, the jib remains horizontal as it carries items. On a luffing type of tower crane, the jib can ratchet to upward or downward angles. The lifting capacity for both types can range from 30 pounds to 10,000 pounds
The crane's body is composed of a mast. This is a vertical steel frame that is a combination of individual sections. In order to increase the overall height of the machinery, parts 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 driver of the crane works from inside of the tower.
In order to raise 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 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 located on the opposite side of the tower. The counter jib holds weights. These weights help to prevent the crane from tipping over when raising heavy materials.