In the gantry crane with large lifting weight, the ratio of pulley block is very large, such as 10 in the crane with lifting weight of 200 tons and 12 in the gantry crane with lifting weight of 250 tons. At the same time, the rope used can withstand the load of up to 11 tons.
In order to reduce the sliding wheel ratio of gantry cranes, different trolley structures are used. This structure is designed on the basis of new and strong ropes, with a diameter of 44cm and a load supporting capacity of up to 27 tons.
When gantry crane using this rope, because the number of parts used by the reason of reducing, can ensure that greatly reduce the weight of the trolley and the amount of manufacturing labor, especially for the lifting height of the large lifting gantry crane, weight and manufacturing labor beam reduction is more significant.
In addition, the number of components for both the suspension and lifting mechanism of gantry cranes has been reduced from 997 to 362.
The number of parts of trolley frame steel structure was reduced from 69 to 19;
Wheelbase of trolley decreased from 5440cm to 4340cm.
For a 250-ton car, the total number of parts that need to be machined has been reduced from 716 to 582.
At the same time to reduce the sliding wheel group ratio, gantry crane can also be used to shorten the suspension with a mandrel - beam, the result of this is in the same height of the lifting height, can reduce the height of the building, or in the same building conditions, increase the lifting height.
Therefore, in the design of gantry crane trolley, usually try to make the mechanism and hanging hook suspension device layout so that the center of the full load trolley nearly from the wheel at the same distance, to meet the different lifting requirements.