Some industrial and commercial buildings could reach heights of over 60 stories. Apparently, when these buildings are being constructed, they require equally tall cranes to transport the supplies to the upper floors. There are cranes that are operated from the rear of trucks or other kinds that have their own vehicle attached. Tower cranes are the biggest ones offered on the market.
Tower cranes are the stand-alone structures which are usually seen on high-rise building projects. Often, they are part of a major city's downtown skyline. Wherever new construction such as skyscrapers or apartment buildings and commercial facilities like for instance shopping center are being built, chances are a crane will be on site.
Types
There are two different types of cranes: boom crane or the jib crane. The jib is a metal frame that 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 can vary from 30,000 lbs. to 10,000 lbs.
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 wherever the desired height is, to the control module, which is a small room that has glass windows on all four sides or to the tower as it is also referred to. The crane operator works from inside of the tower.
Lift
The crane utilizes a braided metal cord to raise supplies. This cord extends out from a motor located next to 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 which holds the cord becomes balanced by a counter jib situated on the opposite side of the tower. The counter jib holds weights. These weights help to prevent the crane from tipping over when heavy materials are carried.