698. Q.--What is the amount of power necessary to drive cotton mills?
A.--An indicator or actual horse power will drive 305 hand mule spindles, with proportion of preparing machinery for the same; or 230 self- acting mule spindles with preparation; or 104 throstle spindles with preparation; or 10-1/2 power looms with common sizing. The throstles referred to are the common throstles spinning 34's twist for power loom weaving, and the spindles make 4000 turns per minute. The self-acting mules are Robert's, about one half spinning 36's weft, and spindles revolving 4800 turns per minute; and the other half spinning 36's twist, with the spindles revolving 5200 times per minute. Half the hand mules were spinning 36's weft, at 4700 revolutions, and the other half 36's twist at 5000 revolutions per minute. The average breadth of the looms was 37 inches, weaving 37 inch cloth, making 123 picks per minute,--all common calicoes about 60 reed, Stockport count, and 68 picks to the inch. To take another example in the case of a mill for twisting cotton yarn into thread:--In this mill there are 27 frames with 96 common throstle spindles in each, making in all 2592 spindles. The spindles turn 2200 times in a minute; the bobbins are 1-7/8 inches diameter, and the part which holds the thread is 2-3/16 inches long. In addition to the twisting frames the steam engine works 4 turning lathes, 3 polishing lathes, 2 American machines for turning small bobbins, two circular saws, one of 22 and the other of 14 inches diameter, and 24 bobbin heads or machines for filling the bobbins with finished thread. The power required to drive the whole of this machinery is 28-1/2 horses. When all the machinery except the spindles is thrown off, the power required is 21 horses, so that 2592, the total number of spindles, divided by 21, the total power, is the number of twisting spindles worked by each actual horse power. The number is 122.84.
699. Q.--What work will be done by a given engine in sawing timber, pressing cotton, blowing furnaces, driving piles, and dredging earth out of rivers?
A.--A high pressure cylinder 10 inches diameter, 4 feet stroke, making 35 revolutions with steam of 90 to 100 lbs. on the square inch, supplied by three cylindrical boilers 30 inches diameter and 20 feet long, works two vertical saws of 34 inches stroke, which are capable of cutting 30 feet of yellow pine, 18 inches deep, in the minute. A high pressure cylinder 14 inches diameter and 4 feet stroke, making 60 strokes per minute with steam of 40 lbs. on the square inch, supplied by three cylindrical boilers without flues, 30 inches diameter and 26 feet long, with 32 square feet of grate surface, works four cotton presses geared 6 to 1, with two screws in each, of 7-1/2 inches diameter and 1-5/8 pitch, which presses will screw 1000 bales of cotton in the twelve hours. Also one high pressure cylinder of 10 inches diameter and 3 feet stroke, making 45 to 60 revolutions per minute, with steam of 45 to 50 lbs. per square inch, with two hydraulic presses having 13 inch rams of 41 feet stroke, and force pumps 2 inches diameter and 6 inches stroke, presses 30 bales of cotton per hour. One condensing engine with cylinder 56 inches diameter, 10 feet stroke, and making 15 strokes per minute with steam of 60 lbs. pressure per square inch, cut off at 1/4th of the stroke, supplied by six boilers, each 5 feet diameter, and 24 feet long, with a 22-inch double-return flue in each, and 198 square feet of fire grate, works a blast cylinder of 126 inches diameter, and 10 feet stroke, at 15 strokes per minute. The pressure of the blast is 4 to 5 lbs. per square inch; the area of pipes 2300 square inches, and the engine blows four furnaces of 14 feet diameter, each making 100 tons of pig iron per week. Two high pressure cylinders, each of 6 inches diameter and 18 inches stroke, making 60 to 80 strokes per minute, with steam of 60 Lbs. per square inch, lift two rams, each weighing 1000 lbs., five times in a minute, the leaders for the lift being 24 feet long. One high pressure cylinder of 12 inches diameter and 5 feet stroke, making 20 strokes per minute, with steam of 60 to 70 lbs. pressure per square inch, lifts 6 buckets full of dredging per minute from a depth of 30 feet below the water, or lifts 10 buckets full of mud per minute from a depth of 18 feet below the water.
CHAPTER XII.
MANUFACTURE AND MANAGEMENT OF STEAM ENGINES.
CONSTRUCTION OF ENGINES.
700. Q.--What are the qualities which should be possessed by the iron of which the cylinder of steam engines are made?
A.--The general ambition in making cylinders is to make them sound and hard; but it is expedient also to make them tough, so as to approach as nearly as possible to the state of malleable iron. This may be done by mixing in the furnace as many different kinds of iron as possible; and it may be set down as a general rule in iron founding, that the greater the number of the kinds of metal entering into the composition of any casting, the denser and tougher it will be. The constituent atoms of the different kinds of iron appear to be of different sizes, and the mixture of different kinds maintains the toughness, while it adds to the density and cohesive power. Hot blast iron was at one time generally believed to be weaker than cold blast iron, but it is now questioned whether it is not the stronger of the two. The cohesive strength of unmixed iron is not in proportion to its specific gravity, and its elasticity and power to resist shocks appear to become greater as the specific gravity becomes less. Nos. 3 and 4 are the strongest irons. In most cases, iron melted in a cupola is not so strong as when remelted in an air furnace, and when run into green sand it is not reckoned so strong as when run into dry sand, or loam. The quality of the fuel, and even the state of the weather, exerts an influence on the quality of the iron: smelting furnaces, on the cold blast principle, have long been known to yield better iron in winter than in summer, probably from the existence of less moisture in the air; and it would probably be found to accomplish an improvement in the quality of the iron if the blast were made to pass through a vessel containing muriate of lime, by which the moisture of the air would be extracted. The expense of such a preparation would not be considerable, as, by subsequent evaporation, the salt might be used over and over again for the same purpose.
701. Q.--Will you explain the process of casting cylinders?