By Etta Bowen


A cranes is usually a metal tower, equipped with cables and pulleys. A cranes is used for lifting, lowering, or for moving things. Up items This is used in construction and demolition sector, but also in transport for loading and unloading jobs. Often, valves are temporary structures, either are connected to the ground, either on a moveable structure, such as on a truck (refurb rough terrain crane).

A widely used model is cranes. This consists of a steel boom structure which is secured to the ground. The tree can run on the underside. At top of this construction is also a steel horizontal boom which can adjusted in height. Confirmed, at end of this tree hangs a hook, which can pulled up or down with cables. Modern cranes have electric motors that cables can rolling and unrolling.

This cranes was powered "tap children" by those in a wheel stepped forth. Cranes Despite protests from the archaeological circuit demolished in 1887. The introduction of lifting working with a winch and pulleys, the slipway hit the vertical transport in disuse. Ever lighter materials In next two centuries, used in Greek construction sites. In contrast to the archaic period (700-500 v. Chr.).

It is sometimes the mast rails over which cranes can drive. At top of mast is the boom, the horizontal arm. The boom rotates with respect to the mast. Rides a carriage so that hook may be closer and further away from the mast to come. About the boom The hook hangs from the pulley. By means of a winch, the hook can raised and lowered.

It is therefore assumed that construction of buildings, the tap the blocks from the ground directly hoisted in place, or from a place that was facing the center of wall through which the working on both sides of wall were able to obtain a construction material. In addition, attendant cranes master, which usually gave the workers of outside tap orders, a rope connecting the load could be

Heavier cranes types were lifting blocks with five pulleys (Pentaspastos) and the largest cranes was lifting even three blocks of five pulleys each. Furthermore, they were dependent on the maximum load of two, three or four lifting masts. The Polypastos can with a reel operated by four men already lifting 3000 kg (3 ropes x 5 pulleys x 4 men x 50 kg = 3000 kg).

Cranes which the reel was replaced by a tredrad could even with two man lifting 6000 kg, because the tredrad a larger diameter and thus has a larger shipment. This means that maximum load of Roman Polypastos 3000 kg per person sixty times larger than the lifting capacity used in construction of pyramids, where about 50 workers were needed to attract.

A cranes can equipped with a control station on a platform on which the operator is (high seat) or state (high position) and the valve operated via a control. However, most modern cars are equipped with Radio control valves so that cranes operator can roam freely on the loading or unloading location and has a better view.




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