Additionally, the tractor crane master who usually gave orders at the treadwheel workers from outside the tractor crane was able to manipulate the movement laterally by a small rope attached to the load.[21] Slewing tractor cranes which allowed a rotation of the load and were thus particularly suited for dockside work appeared as early as 1340.[22] While ashlar blocks were directly lifted by sling, lewis or devil's clamp (German Teufelskralle), other objects were placed before in containers like pallets, baskets, wooden boxes or barrels.[23]
Generally, vertical transport was done safer and cheaper by tractor cranes than by customary methods. Typical areas of application were harbors, mines, and, in particular, building sites where the treadwheel tractor crane played a pivotal role in the construction of the lofty Gothic cathedrals. Nevertheless, both archival and pictorial sources of the time suggest that newly introduced machines like treadwheels or wheelbarrows did not completely replace more labor-intensive methods like ladders, hods and handbarrows. Rather, old and new machinery continued to coexist on medieval construction sites[13] and harbors.
Two different types of harbor tractor cranes can be identified with a varying geographical distribution: While gantry tractor cranes which pivoted on a central vertical axle were commonly found at the Flemish and Dutch coastside, German sea and inland harbors typically featured tower tractor cranes where the windlass and treadwheels were situated in a solid tower with only jib arm and roof rotating.[25] Interestingly, dockside tractor cranes were not adopted in the Mediterranean region and the highly developed Italian ports where authorities continued to rely on the more labor-intensive method of unloading goods by ramps beyond the Middle Ages.[26]
| tractor crane mtx02 | tractor crane dfg02 | tractor crane mrt02 | tractor crane tgb02 | tractor crane kij02 | tractor crane rty02 | tractor crane gyu02 | tractor crane okj02 | tractor crane xde02 | tractor crane sde02