There are several industrial and commercial buildings which now surpass 60 stories or more. These buildings all need tall cranes to be able to help transport the materials to the higher floors. There are cranes that have their own vehicle attached or other kinds that are operated from the back of trucks. Tower cranes are the largest kinds available on the market.
Tower cranes are stand-alone structures found as part of a major city's downtown skyline on high-rise building projects. Wherever new construction like for example skyscrapers or apartment buildings and commercial facilities like shopping center are being built, chances are a crane would be on site.
Kinds
The two key kinds of cranes could be differentiated by the manner in which their boom or jib raises supplies. The jib is the 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 downward or upward 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 individual [parts. The sections are added to increase the overall height of the equipment. The mast extends upward to where 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 called. The crane driver works from inside of the tower.
Lift
The crane uses a braided metal cord to raise materials. This cord extends out from a motor located next to the control module to the end of the jib or boom. 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 located on the tower's opposite side. The counter jib holds weights. These weights help to prevent the crane from tipping over when heavy supplies are lifted.