There are several industrial and commercial buildings which now surpass 60 stories or more. These buildings all require tall cranes to be able to help move the materials to the higher floors. There are cranes which are operated from the rear of trucks or other types that have their own vehicle attached. Tower cranes are the biggest ones offered on the market.
Tower cranes are stand-alone structures seen as part of a major city's downtown skyline on high-rise building projects. When new construction such as skyscrapers or apartment buildings and commercial facilities like shopping center are being built, chances are a crane would be on site.
Kinds
The two key kinds of cranes can be distinguished by the way in which their boom or jib lifts supplies. The jib is the metal frame that extends from the main section. On a flat tower crane, the jib remains horizontal when it lifts things. On a luffing type of tower crane, the jib could ratchet to downward or upward angles. The lifting capacity for both kinds could vary from 30,000 lbs. to 10,000 lbs.
Body
The crane's body is composed of a mast. This is a vertical steel frame which is a combination of separate parts. In order to increase the overall height of the machinery, sections are added. 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 referred to. The crane operator 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 near the control module to the end of the boom or jib. 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.