Several commercial and industrial buildings could reach heights of more than 60 stories. Apparently, when these buildings are being built, they require equally tall cranes to be able to transport the supplies to the upper floors. There are cranes which are operated from the back of trucks or other kinds which have their own vehicle connected. Tower cranes are the biggest kinds on the market.
Tower cranes are the stand-alone structures which are normally found on high-rise building projects. Normally, they are part of a major city's downtown skyline. When new construction like apartment buildings and skyscrapers and commercial facilities like shopping center are being constructed, 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 which extends from the main section. On a flat tower crane, the jib remains horizontal as it lifts 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 mast. This is a vertical steel frame which is a combination of separate parts. In order to increase the overall height of the machinery, sections are added. 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 called. The crane operator works from inside of the tower.
Lift
To lift 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 situated near 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 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 tipping over when heavy materials are lifted.