752 



HYDRAULICS AND ITS APPLICATIONS 



in the two cases are then in the ratio of D 2 : D 2 d?, while the volumes 

 of water used per stroke are in the same ratio. 



For loads much above two tons, two distinct cylinders, each having its 

 own valves, pipes, chains, and jib-head sleeves, offer many advantages. 

 Thus for a 10-ton crane, one cylinder to lift 6J tons and a second to lift 

 3J tons would be suitable, the two working in conjunction for loads above 

 6J tons. 



In Fig. 368 a simple type of hydraulic wall crane, suitable for a ware- 



FIG. 369. Self-contained Hydraulic Crane with separate Backing, Hoisting and 



Slewing Cylinders. 



house, is illustrated. Here hydraulic power is used for lifting only. The 

 jigger may be placed against the wall as shown, or horizontally if prefer- 

 able, and the controlling valve worked from a hand rope on any floor 

 of the building. 



In Fig. 369, a type of hydraulic crane much used in steel works, for 

 removing ingots from the soaking pit to the rolling mill, is illustrated. 1 

 The crane is self-contained, hoisting, lowering, racking in and out, and 

 slewing being performed by hydraulic power. The latter operation is 



1 By kind permission of the makers. 



