Some industrial and commercial buildings can reach heights of more than 60 stories. Obviously, when these buildings are being built, they need equally tall cranes to transport the materials to the upper floors. There are cranes which have their own vehicle connected or other kinds which are operated from the rear of trucks. Tower cranes are the largest ones on the market.
Tower cranes are the stand-alone structures which are often seen on high-rise building projects. Usually, they are part of a major city's downtown skyline. When new construction like for example skyscrapers or apartment buildings and commercial facilities like for example shopping center are being constructed, chances are a crane would be on site.
Types
There are two different types of cranes: boom crane or the jib crane. The jib is a metal frame which extends from the main section. On a flat tower crane, the jib remains horizontal when it lifts items. On a luffing kind of tower crane, the jib can ratchet to downward or upward 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 which is composed of individual sections. The sections are added to increase the overall height of the machine. The mast extends upward to where 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
The crane uses 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 located on the opposite side of the tower. The counter jib has weights. These weights help to prevent the crane from tipping over when heavy materials are carried.