Some commercial and industrial buildings could reach heights of more than 60 stories. Apparently, while these buildings are being constructed, they require equally tall cranes to transport the supplies to the higher floors. There are cranes that are operated from the back of trucks or other types which have their own vehicle connected. Tower cranes are the biggest ones 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 skyscrapers or apartment buildings and commercial facilities like shopping center are being constructed, chances are a crane will be on site.
Types
The two key types of cranes can be differentiated by the manner in which their boom or jib lifts supplies. The jib is the metal frame that extends from the main section. On a flat tower crane, the jib remains horizontal as it lifts things. On a luffing type of tower crane, the jib can ratchet to downward or upward angles. The lifting capacity for both kinds could vary from 30,000 lbs. to 10,000 pounds
Body
The body of the crane is composed of a vertical steel mast which is composed of individual [parts. The parts are added to be able increase the overall height of the equipment. 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 called. The driver of the crane works from inside of the tower.
Lift
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 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 situated on the tower's opposite side. The counter jib has weights. These weights help to prevent the crane from tipping over when lifting heavy materials.