528 : APPLIED MECHANICS 
blocks or sets of pulleys are pushed apart by a great force, which is m 
to overcome a smaller force at the free end of the chain. One b 
attached to the bottom of a hydraulic cylinder, and the other to the 
A chain passes over the pulleys in the two blocks in the same manner 
in the ordinary block and tackle, the free end of the chain passing mo 
crane post and over guide pulleys to the load to be lifted. — 
Referring to Fig. 840, A is the stationary cylinder, and B the ram. 
Fixed to the bottom of the cylinder is the frame C carrying one set 
pulleys, and fixed to the outer end of the ram is the frame D carrying 
the other set of pulleys. One end of the chain is attached to the bre 
E on the fixed frame C. 
From the fixed end at E the chain passes over the pulley F, and #] 
down and up over the various pulleys, and finally passes up to and 0} 
guide pulleys in the frame of the crane to the load to be raised. Oe 
Neglecting friction, the load lifted is equal to the tension in the chain, 
which is equal to the total force on the ram divided by the number of 
straight lengths of chain which proceed from the pulleys on the ram. 
Exercises XXXL 
1. If a hydraulic power company charges 15 pence per 1000 gallons of w 
at a pressure of 750 lbs. per square inch, what is the cost per horse-power 
to the consumer ? 
2. How many ft.-Ibs, of work may be stored up ina hydraulic accumu 
whose ram has a diameter of 12 inches, and a lift of 13 feet, when the presst 
of the water is 750 lbs. per square inch? 
8. What is the pressure of the water in a hydraulic accumulator having a ram — 
11 inches in diameter when the total load is 45 tons and friction is neglected cm 
4. What must be the diameter of the ram of a hydraulic accumulator whic 
is to have a capacity of 100 horse- -power minutes with a water pressure 
1120 lbs, per square inch, if the stroke is 14 times the diameter of the ram? ig 
5. The ram of a hydraulic accumulator (Fig. 834, p. 522) is 12 inches pe 
diameter, and the total moving load is 55 tons, If the force required to pee 
the cylinder along the ram against the resistance of friction only is 2°5 tons. 
what is the pressure of the water, in Ibs, per square inch, (a) when the load i 
ascending with uniform velocity, (6) when the load is descending with unif 
velocity ? 
6. The ram of a hydraulic accumulator is 18 inches in diameter, the stroke is 
23 feet, and the water pressure is 1120 lbs, per square inch. If the useful work 
given up by this accumulator during one full downward stroke is utilised in — 
raising YW tons to a. height of 40 feet by means of a hydraulic crane whose ~ 
efficiency is 55 per cent., find W. If this work is donein three minutes, what is 
the gross horse-power of the crane? 
7. The ram of a hydraulic accumulator is 4 inches in diameter, The pressure 
of the water from the accumulator is to be 1°5 tons per square inch, and the — 
water is used to work the hydraulic ram of a testing machine, which is 9°5 inches — 
in diameter. (a) What total load must be placed on the 4-inch ram if 5 percent, — 
of the load is wasted in the friction of the cup-leathers, etc.? (6) What total — 
long is the testing machine capable of applying, if there is a further loss of — 
5 per cent, in the cup-leathers of the large cylinder? [B.E. ye 
8. The diameters of the two parts of the ram of a differential accumulator b 
(Fig. 835, p. 523) are 6 inches and 5 inches, and the stroke is 50 inches, If the 
pressure of the water is 1500 lbs. per square inch when the load is at rest or when’ 
it is moving with uniform velocity, what load is required, including the weight of © 
the cylinder? How many ft.-lbs, of work may be stored in this accumulator? 
What would be the diameter of the ram of an ordinary accumulator to carry the © 
same load with the same water pressure ? a 
9. The total moving load on a differential hydraulic accumulator is 3 tons, 4 
The diameters of the larger and smaller parts of the ram are 44 inches and — 
Lo - 
A 
i 
