EXAMPLES 79< 



500 Ibs. per square inch. Assuming an efficiency of 75 per cent 

 determine the necessary size of ram. 



Answer. 3'5 inches diameter. 



(6) A hydraulic jack has an efficiency of 80 per cent. The diametei 

 of the ram is 8 inches, of the plunger f inch. The leverage of the 

 operating lever is 20 : 1. Determine the pressure on the handle whei 



lifting forty tons. 



Answer. 49*2 Ibs. 



(7) A buffer stop is to be designed to stop a train weighing 150 tons 

 when going at ten miles per hour, in 8 feet. The cylinder diameter is 

 16 inches, the piston rod being 5 T % inches diameter. The thickness o 

 the piston is 4 inches, but the entrant edges of the orifices are roundec 

 so as to make their effective length equal to 2 inches. There are tw( 

 rectangular orifices, each 3 inches wide by 2*10 inches deep. Determine 

 their effective depth at points where the piston travel is respectively 

 0, 2, 4, 6 and 8 feet, in order that the resistance may be uniform through 

 out the stroke. Also determine the magnitude of this resistance and th( 

 pressure in the cylinder, assuming that counterbalance weights anc 

 friction exert a constant resistance of one ton. 



Answer. Eesistance 140, 300 Ibs. = 62'65 tons. 



Pressure in cylinder =781 Ibs. per square inch. 



(8) If the buffer stop of the preceding example has the same effective 

 piston area with two rectangular connecting orifices each 3 inches wide 

 which together have a combined area of 6 square inches, this remaining 

 uniform throughout the stroke, determine the maximum pressure attained 

 in the cylinder and the length of stroke which would be necessary for the 

 piston to come to rest without touching the end of the cylinder. 



Answer. Maximum pressure = 1,320 Ibs. per square inch. 

 Stroke = 22'45 feet. 



(9) If the area of the passages in Example 8 were 3 square inches, 

 determine the maximum pressure attained, and the length of stroke before 

 coming to rest. 



Answer. Pressure = 5,275 Ibs. per square inch. 

 Stroke = 7'53 feet. 



