Used Self Erect Cranes Tacoma - The base of the tower crane is generally bolted to a large concrete pad which provides really necessary support. The base is connected to a tower or a mast and stabilizes the crane that is affixed to the inside of the structure of the building. Normally, this attachment point is to a concrete lift or to an elevator shaft.
Usually, the mast is a triangulated lattice structure measuring 0.9m2 or 10 feet square. The slewing unit is connected to the very top of the mast. The slewing unit is made of a gear and a motor which allows the crane to rotate.
Tower cranes are able to have a maximum unsupported height of 80m or two hundred sixty five feet. The maximum lifting capacity of a tower crane is sixteen thousand six hundred forty two kilograms or 39,690 lbs. with counter weights of twenty tons. Moreover, two limit switches are used in order to ensure the driver does not overload the crane. There is also another safety feature known as a load moment switch to ensure that the operator does not surpass the ton meter load rating. Last of all, the maximum reach of a tower crane is 230 feet or 70 meters.
There is certainly a science involved with erecting a tower crane, especially because of their extreme heights. At first, the stationary structure has to be brought to the construction site by utilizing a big tractor-trailer rig setup. After that, a mobile crane is used so as to assemble the equipment portion of the jib and the crane. These sections are then connected to the mast. Next, the mobile crane adds counterweights. Forklifts and crawler cranes can be a few of the other industrial equipment which is utilized to erect a crane.
Mast extensions are added to the crane as the building is erected. This is how the height of the crane is able to match the building's height. The crane crew uses what is called a top climber or a climbing frame that fits between the top of the mast and the slewing unit. A weight is hung on the jib by the work crew so as to balance the counterweight. Once complete, the slewing unit could detach from the top of the mast. In the top climber, hydraulic rams are used to adjust the slewing unit up an extra 6.1m or twenty feet. Then, the driver of the crane utilizes the crane to insert and bolt into place another mast section piece.
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