Some commercial and industrial buildings are capable of reaching heights of more than 60 stories. Apparently, when these buildings are being built, they require equally tall cranes to move the materials to the higher floors. There are cranes which are operated from the rear of trucks or other types which have their own vehicle connected. Tower cranes are the biggest types available on the market.
Tower cranes are the stand-alone structures that are normally seen on high-rise building projects. Normally, they are part of a major city's downtown skyline. When new construction like for instance skyscrapers or apartment buildings and commercial facilities such as shopping center are being constructed, odds are a crane would be on site.
There are two different types 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 lifts things. On a luffing kind of tower crane, the jib can ratchet to upward or downward angles. The lifting capacity for both kinds could vary from 30 pounds to 10,000 lbs.
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 operator of the crane works from inside of the tower.
To lift materials, the crane uses a braided metal cord. The cord extends all the way to the end of the boom or jib from a motor situated near the control module. 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 toppling over when heavy materials are lifted.