798 HYDRAULICS AND ITS APPLICATIONS 



N.B. The total weight to be accelerated in this case = 4 -f 3 -f 3 

 10 tons. 



f Working pressure 554 Ibs. per square inch. 

 j Diameter of reducer cylinder = 15*8 inches. 

 Answer, j ])i ame ter of reducer ram = 13'95 inches. 

 L Gain in efficiency = 35 '4 per cent. 



(2) A direct acting hydraulic lift has a travel of 40 feet. The cage and 

 ram weigh four tons, and the lift takes a weight of three tons, with an 

 acceleration of 2 f.s.s. Assuming a ram diameter of 5 inches, and a 

 hydraulic balance cylinder of the type shown in Fig. 361 to be fitted, 

 this being designed so as to balance three-quarters of the weight of the 

 cage and ram when the latter is at the upper limit of its travel, determine 

 the leading dimensions of this balance cylinder, given that the stroke of 

 its ram is 6 feet ; that the ram B weighs one ton ; and that the annular 

 space Z) is supplied from a tank whose level is such as to produce a 

 pressure of 30 Ibs. per square inch on the annulus E when this ram is at 

 the bottom of its stroke. The supply pressure at A is 1,100 Ibs. per 

 square inch. 



Outer diameter of ram B = 12'95 inches. 



Answer. - 



Outer diameter of stationary inlet ram = 9'0 inches. 



Outer diameter of annulus E =44 inches. 



(3) If in the lift of the preceding example the type of balance cylinder 

 of Fig. 362 is used, determine the necessary diameters of A,B, and (7, 

 and the necessary weight of ram B. Take into account the acceleration 

 of B. 



F Outer diameter of ram C = 12'95 inches. 

 Answer, -j Outer diameter of ram A = 9*0 inches. 

 I Weight otB = 20'2 tons. 



(4) If in example (1) the cage and ram form part of a suspended lift, 

 counterbalanced to the same extent as in that question, and operated 

 through a jigger giving a multiplying ratio of 6:1, determine the 

 necessary diameter of the cylinder of the jigger if the working pressure = 

 750 Ibs. per square inch ; the efficiency of the multiplying mechanism = 

 75 per cent. ; and frictional losses account for 10 per cent, of the pressure 

 on the ram. 



Answer. 12*8 inches diameter. 



(5) A direct acting crane of the type shown in Fig. 370 is to lift two 

 tons, with a maximum acceleration of 4 f.s.s. The supply pressure is 



