There are several commercial and industrial buildings which now surpass 60 stories or more. These buildings all require tall cranes to help transport the supplies to the upper floors. There are cranes which are operated from the rear of trucks or other types which have their own vehicle connected. Tower cranes are the biggest kinds offered on the market.
Tower cranes are the stand-alone structures that are normally seen on high-rise building projects. Often, they are part of a major city's downtown skyline. When new construction such as apartment buildings and skyscrapers and commercial facilities such as shopping center are being constructed, odds are a crane would be on site.
Types
There are two different kinds 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 as it carries items. On a luffing type of tower crane, the jib could 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 mast. This is a vertical steel frame that is a combination of separate sections. In order to increase the overall height of the machinery, sections are added. 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 operator of the crane 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 near 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 which 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 toppling over when raising heavy materials.