There are several industrial and commercial buildings that now exceed 60 stories or more. These buildings all require tall cranes to be able to help transport the materials to the higher floors. There are cranes that have their own vehicle connected or other kinds that are operated from the back of trucks. Tower cranes are the largest ones on the market.
Tower cranes are the stand-alone structures that are usually seen on high-rise building projects. Often, they are part of a major city's downtown skyline. Wherever new construction such as skyscrapers or apartment buildings and commercial facilities like for example shopping center are being built, odds are a crane will be on site.
Kinds
The two major types of cranes can be differentiated by the way in which their jib or boom lifts materials. The jib is the metal frame that 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 could ratchet to upward or downward angles. The lifting capacity for both types could vary from 30 pounds to 10,000 pounds
Body
The body of the crane is composed of a vertical steel mast which is composed of individual [parts. The parts are added to increase the overall height of the equipment. 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 called. The crane driver 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 jib or boom from a motor located 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 that holds the cord becomes balanced by a counter jib situated 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 lifted.