There are some industrial and commercial buildings which now exceed 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 back of trucks or other types that have their own vehicle connected. Tower cranes are the biggest types offered on the market.
Tower cranes are the stand-alone structures that are usually found on high-rise building projects. Often, they are part of a major city's downtown skyline. Wherever new construction like for instance apartment buildings and skyscrapers and commercial facilities such as shopping center are being built, chances are a crane will be on site.
Kinds
There are two different kinds of cranes: jib crane of the boom crane. The jib is a metal frame that extends from the main section. On a flat tower crane, the jib remains horizontal when it carries items. On a luffing kind of tower crane, the jib can ratchet to upward or downward angles. The lifting capacity for both kinds could range from 30 pounds to 10,000 lbs.
Body
The crane's body is composed of a vertical steel mast which is composed of separate [parts. The sections are added to increase the overall height of the machine. 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 referred to. The crane operator works from inside of the tower.
Lift
The crane utilizes a braided metal cord to raise materials. This cord extends out from a motor situated near the control module to the end of the jib or boom. 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 opposite side of the tower. The counter jib has weights. These weights help to prevent the crane from toppling over when heavy materials are lifted.