There are several industrial and commercial buildings which now exceed 60 stories or more. These buildings all need tall cranes to help move the materials to the higher floors. There are cranes which have their own vehicle attached or other types which are operated from the back of trucks. Tower cranes are the largest types available 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 like skyscrapers or apartment buildings and commercial facilities such as shopping center are being constructed, chances are a crane will be on site.
Kinds
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 when it lifts items. On a luffing type of tower crane, the jib could ratchet to upward or downward angles. The lifting capacity for both types could range from 30 pounds to 10,000 pounds
Body
The body of the crane is composed of a vertical steel mast that is composed of individual [parts. The parts are added to be able increase the overall height of the machine. The mast extends upward to where the desired height is, to the control module, that is a small room which has glass windows on all four sides or to the tower as it is also referred to. The crane driver works from inside of the tower.
Lift
The crane uses a braided metal cord to lift materials. This cord extends out from a motor situated next to 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 which holds the cord becomes balanced by a counter jib situated on the opposite side of the tower. The counter jib holds weights. These weights help to prevent the crane from toppling over when lifting heavy materials.