Several commercial and industrial buildings are capable of reaching heights of over 60 stories. Apparently, when these buildings are being built, they need equally tall cranes to be able to transport the supplies to the upper floors. There are cranes which are operated from the rear of trucks or other types which have their own vehicle attached. Tower cranes are the largest kinds 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 such as apartment buildings and skyscrapers and commercial facilities like for example shopping center are being built, odds are a crane will be on site.
Kinds
The two key types of cranes could be distinguished by the way in which their boom or jib lifts materials. The jib is the metal frame which extends from the main section. On a flat tower crane, the jib remains horizontal when it lifts 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 pounds
Body
The body of the crane is composed of a vertical steel mast which is composed of separate [parts. The parts are added to increase the overall height of the machinery. 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
The crane uses a braided metal cord to lift supplies. This cord extends out from a motor situated near the control module to the end of the boom or jib. 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 situated 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 carried.