There are several commercial and industrial buildings that now exceed 60 stories or more. These buildings all need tall cranes to be able to help transport the supplies to the higher floors. There are cranes which are operated from the rear of trucks or other kinds that have their own vehicle connected. Tower cranes are the largest kinds available on the market.
Tower cranes are the stand-alone structures which are normally found on high-rise building projects. Often, they are part of a major city's downtown skyline. Wherever new construction such as apartment buildings and skyscrapers and commercial facilities such as shopping center are being built, odds are a crane would 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 carries items. On a luffing type of tower crane, the jib could ratchet to downward or upward angles. The lifting capacity for both types can vary from 30,000 lbs. to 10,000 lbs.
Body
The body of the crane is composed of a vertical steel mast that is composed of separate [parts. The sections are added to increase the overall height of the machinery. The mast extends upward to where 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 called. The crane operator works from inside of the tower.
Lift
To raise supplies, the crane uses a braided metal cord. The cord extends all the way to the end of the jib or boom 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 opposite side of the tower. The counter jib has weights. These weights help to prevent the crane from toppling over when raising heavy materials.