HYDRAULIC MACHINERY, FOR MINES 845 



Example. What load will a single-acting pressure-engine sustain, and what Trill 

 be the horse-power, the diameter of the cylinder being 20 inches, effective journey of 

 piston 60 feet per minute, height of pressure-column 200 feet? 



Pressure -column Table I. 200 feet = 87 Ibs. pressure per square inch. 



Diameter of cylinder 20 inches = 314-16 square inches, and 



Product of efficiency in Table VII. -80 



314-16 x 87 Ibs. x -80 = 21,865 Ibs. actual load which piston will sustain. 



Then 21,865 x 60 -r 33,000 = 497 effective horse-power. 



Charging rams. To find the area of a ram for charging an accumulator, to work 

 under a given load when the effective sustaining power of the charging engine is 

 known. 



EULE. Divide the effective sustaining power of the engine by the load per square 

 inch to be imposed on the accumulator, the quotient will be the area of the charging ram. 



Example. The effective sustaining power of a pressure- engine is 21,865 Ibs., and 

 the accumulator is to carry a load of 800 Ibs per square inch. What will be the area 

 of the charging ram ? 



21,865-*-800=527'2 inches area, or 6| inches diameter. 



Accumulator. To ascertain the weight required on an accumulator ram of a given 

 diameter, the charging pressure being given. 



EULE. Multiply the area of the accumulator ram by the charging pressure in 

 pounds, the product will be the weight required on the accumulator ram less the dead 

 weight of the accumulator ram, cross-head and weight-box. 



Example. An accumulator ram is 10 inches diameter, the charging pressure is 

 800 Ibs. per square inch, the weight of the ram, cross-head and weight-box is 6,000 Ibs. ; 

 what extra weight must be added ? 



Ibs. 



10 inches = 78-54x800 Ibs. 62,832 



Less weight of ram, cross-head and weight-box . . . 6,000 



Am. 56,822 

 USEFUL MEMORANDA. 

 1 cubic foot of water weighs 1,000 ounces, or . 62*5 Ibs. 



1 cubic inch '036 Ib. 



1 imperial gallon = 277'274 cubic inches . . . 10 Ibs. 



1 , . 0-16 cub. ft. 



1 cubic foot of water =6, 238 gallons, or approximately . 6 gall. 



1 '8 cubic foot of water 1 cwt. 



11 '2 imperial gallons = 1 cwt. or 224 gall. . . .1 ton 



35-84 cubic feet 1 ton 



A column of water 12 inches high one inch square . '434 Ibs. 

 diameter . *341 Ibs. 

 One cylindrical foot of water 4,895 imp. gall. 



Sea Water. 



1 cubic foot = 64- 11 Ibs. or 1-027 times the weight of fresh water. 



Rainfall. 



Inches of rainfall x 2,323,200 = cubic feet per square mile. 



x 14 = millions of gallons per square mile. 



x 3,630 = cubic feet per acre. 



Sundries. 



A fall of T ^th of an inch in a mile will produce i current in rivers. 

 Melted snow produces about ^-th of its bulk in water. 

 Sound passes in water at a velocity of 4,708 feet per second. 



Expansion of Water. 



Volume of water at 32 = 1 ,000. 



at 212= 1,046 ; increase in 180 = '046. 



Construction of Water-wheels. The application of vertical wheels to the purposes 

 of mining is copiously illustrated in Agricola's work, 'De Ee Metallica,' edition 1621, 

 where overshot and undershot wheels are shown driving pumps direct, as well as 

 through the medium of cranks and spur-gearing. 



GENERAL EULES. When iron is used for water-wheels, curved buckets and shroudings 

 are preferable to deal float-boards and oak starts. 



In designing iron wheels care should be taken that, while attempting to form a 



