There are several commercial and industrial buildings which now surpass 60 stories or more. These buildings all need tall cranes to be able to help move the supplies to the upper floors. There are cranes which have their own vehicle attached or other types that are operated from the rear of trucks. Tower cranes are the largest types available on the market.
Tower cranes are stand-alone structures seen as part of a major city's downtown skyline on high-rise building projects. Wherever new construction like for example skyscrapers or apartment buildings and commercial facilities like for instance shopping center are being built, odds 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 as it carries things. On a luffing type of tower crane, the jib can ratchet to upward or downward angles. The lifting capacity for both kinds could range from 30,000 lbs. to 10,000 lbs.
Body
The body of the crane is composed of a vertical steel mast which is composed of separate sections. The parts are added to increase the overall height of the equipment. The mast extends upward to wherever the desired height is, to the control module, that is a small room that 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
In order to raise supplies, the crane utilizes a braided metal cord. The cord extends all the way to the end of the boom or jib from a motor located next to the control module. 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 tipping over when heavy materials are lifted.