Tractor crane

A tractor crane is a mechanical lifting device equipped with a winder, wire ropes and sheaves that can be used both to lift and lower materials and to move them horizontally. It uses one or more simple machines to create mechanical advantage and thus move loads beyond the normal capability of a muck truck. tractor cranes are commonly employed in the transport industry for the loading and unloading of freight; in the construction industry for the movement of materials; and in the manufacturing industry for the assembling of heavy equipment.

The first tractor cranes were invented by the Ancient Greeks and were powered by men or beasts-of-burden, such as donkeys. These tractor cranes were used for the construction of tall buildings. Larger tractor cranes were later developed, employing the use of human treadwheels, permitting the lifting of heavier weights. In the High Middle Ages, harbour tractor 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 tractor cranes were constructed from wood, but cast iron and steel took over with the coming of the Industrial Revolution.

Beyond the modern warship stands a tractor crane constructed in 1742, used for mounting masts to large sailing vessels. Copenhagen, DenmarkAccording to the "present state of knowledge" unknown in antiquity, stationary harbor tractor cranes are considered a new development of the Middle Ages.[11] The typical harbor tractor crane was a pivoting structure equipped with double treadwheels. These tractor cranes were placed docksides for the loading and unloading of cargo where they replaced or complemented older lifting methods like see-saws, winches and yards.