Some commercial and industrial buildings could reach heights of more than 60 stories. Apparently, when these buildings are being constructed, they need equally tall cranes to transport 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 biggest types available on the market.
Tower cranes are the stand-alone structures that are usually found on high-rise building projects. Often, they are part of a major city's downtown skyline. When new construction like skyscrapers or apartment buildings and commercial facilities like shopping center are being built, odds are a crane will be on site.
Kinds
The two major types of cranes can be distinguished by the manner in which their boom or jib lifts materials. The jib is the metal frame that extends from the main section. On a flat tower crane, the jib remains horizontal as it carries items. On a luffing type of tower crane, the jib can ratchet to upward or downward angles. The lifting capacity for both kinds could vary from 30 pounds to 10,000 lbs.
Body
The body of the crane is composed of a vertical steel mast that is composed of separate sections. The parts are added to increase the overall height of the machine. 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 materials, the crane uses a braided metal cord. The cord extends all the way to the end of the boom or jib from a motor situated next to 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 which 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 heavy supplies are lifted.