Several commercial and industrial buildings can reach heights of over 60 stories. Apparently, when these buildings are being built, they need equally tall cranes to be able to move the supplies to the higher floors. There are cranes which have their own vehicle connected or other types that are operated from the back of trucks. Tower cranes are the biggest types on the market.
Tower cranes are the stand-alone structures that are normally found on high-rise building projects. Often, they are part of a major city's downtown skyline. Wherever new construction like for example skyscrapers or apartment buildings and commercial facilities such as shopping center are being built, chances are a crane would be on site.
Kinds
There are two different kinds of cranes: jib crane of the boom crane. The jib is a metal frame that 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 can ratchet to upward or downward angles. The lifting capacity for both kinds could vary from 30,000 lbs. to 10,000 lbs.
Body
The crane's body 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 wherever 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 driver 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 located 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 holds weights. These weights help to prevent the crane from tipping over when lifting heavy supplies.