There are some commercial and industrial buildings which now exceed 60 stories or more. These buildings all require tall cranes to help move the materials to the higher floors. There are cranes that are operated from the rear of trucks or other kinds that have their own vehicle connected. Tower cranes are the biggest types on the market.
Tower cranes are stand-alone structures found as part of a major city's downtown skyline on high-rise building projects. Wherever new construction such as apartment buildings and skyscrapers and commercial facilities such as shopping center are being constructed, chances are a crane would be on site.
Kinds
The two key kinds of cranes could be differentiated by the manner in which their boom or jib lifts materials. The jib is the metal frame which 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 could ratchet to downward or upward angles. The lifting capacity for both types could range from 30 pounds 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 separate sections. In order to increase the overall height of the machine, 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 crane driver works from inside of the tower.
Lift
The crane utilizes a braided metal cord to be able to lift materials. This cord extends out from a motor located next to the control module to the end of the boom or jib. 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 located on the tower's opposite side. The counter jib holds weights. These weights help to prevent the crane from tipping over when heavy supplies are carried.