CKANES 



751 



working inside the larger, which itself works in the pressure cylinder. 

 For light loads the larger is held stationary by locking gear, the smaller 

 ram then doing the lifting. For heavy loads the two rams work together 



as one. 



Such an arrangement is shown in Fig. 367, EI and R% being the two 



FIG. 367. Hoisting Cylinder and 

 Rams for Two- Power Crane. 



FIG. 368. Hydraulic Wall Crane. 



rams. Under light loads the ram R% is held by means of the catches C\ 

 and <7 2 which are actuated by the lever L. 



A second arrangement consists of a single ram d carrying a plunger of 

 somewhat larger diameter D. For heavy loads water is admitted only to 

 the larger plunger, while for lighter loads both sides of the plunger are 

 put into free communication with the pressure supply. The forces exerted 



