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18, 853a32-853b13) attributed to Aristotle (384–322 BC), but perhaps composed at a slightly later date.Around the same time, block sizes at Greek temples began to match their archaic predecessors again, indicating that the more sophisticated compound pulley must have found its way to Greek construction sites by then.It is mainly used for lifting heavy things and transporting them to other places.The device uses one or more simple machines to create mechanical advantage and thus move loads beyond the normal capability of a human.Wählen Sie „Optionen verwalten“, um Ihre Datenverwendung und Freigabeoptionen festzulegen.Weitere Informationen und Einstellungen finden Sie im Datenschutzcenter.Modern cranes usually use internal combustion engines or electric motors and hydraulic systems to provide a much greater lifting capability than was previously possible, although manual cranes are still utilized where the provision of power would be uneconomic.
Mini-cranes are also used for constructing high buildings, in order to facilitate constructions by reaching tight spaces.In the High Middle Ages, harbour cranes were introduced to load and unload ships and assist with their construction – some were built into stone towers for extra strength and stability.The earliest cranes were constructed from wood, but cast iron, iron and steel took over with the coming of the Industrial Revolution.The archaeological record shows that no later than c.515 BC distinctive cuttings for both lifting tongs and lewis irons begin to appear on stone blocks of Greek temples.
Since these holes point at the use of a lifting device, and since they are to be found either above the center of gravity of the block, or in pairs equidistant from a point over the center of gravity, they are regarded by archaeologists as the positive evidence required for the existence of the crane.
Finally, we can find larger floating cranes, generally used to build oil rigs and salvage sunken ships.