There are some commercial and industrial buildings which now surpass 60 stories or more. These buildings all require tall cranes to be able to help transport the materials to the upper floors. There are cranes that have their own vehicle attached or other types which are operated from the back of trucks. Tower cranes are the largest ones on the market.
Tower cranes are stand-alone structures seen as part of a major city's downtown skyline on high-rise building projects. When new construction such as apartment buildings and skyscrapers and commercial facilities like shopping center are being constructed, chances are a crane will be on site.
Types
There are two different types of cranes: jib crane of the boom 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 things. On a luffing kind of tower crane, the jib could ratchet to downward or upward angles. The lifting capacity for both kinds can range 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 [parts. The parts are added to increase the overall height of the machinery. 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 utilizes a braided metal cord to be able to lift materials. This cord extends out from a motor located near the control module to the end of the boom or jib. 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 opposite side of the tower. The counter jib holds weights. These weights help to prevent the crane from toppling over when heavy supplies are carried.