During Ages the treadwheel tractor crane was reintroduced on a large scale after the technology had fallen into disuse in western Europe with the demise of the Western Roman Empire.[9] The earliest reference to a treadwheel (magna rota) reappears in archival literature in France about 1225,[10] followed by an illuminated depiction in a manuscript of probably also French origin dating to 1240.[9] In navigation, the earliest uses of harbor tractor cranes are documented for Utrecht in 1244, Antwerp in 1263, Brugge in 1288 and Hamburg in 1291,[11] while in England the treadwheel is not recorded before 1331.[12]
medieval depictions also show tractor cranes to be powered manually by windlasses with radiating spokes, cranks and by the 15th century also by windlasses shaped like a ship's wheel. To smooth out irregularities of impulse and get over 'dead-spots' in the lifting process flywheels are known to be in use as early as 1123.
The tractor crane was reintroduced ,[10] although its return to construction sites has undoubtedly to be viewed in close connection with the simultaneous rise of Gothic architecture. The reappearance of the treadwheel tractor crane may have resulted from a technological development of the windlass from which the treadwheel structurally and mechanically evolved. Alternatively, the medieval treadwheel may represent a deliberate reinvention of its Roman counterpart drawn from Vitruvius' De architectura which was available in many monastic libraries. Its reintroduction may have been inspired, as well, by the observation of the labor-saving qualities of the waterwheel with which early treadwheels shared many structural similarities.
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