The cylinder diameters are: High-pressure, 25.5 inches; low-pressure, 52 inches; pumpplunger, 48 inches; and the stroke, common to all, is 9 feet. Both cylinders are thoroughly steam-jacketed on sides and ends; and the exhaust steam from the high-pressure cylinder passes, on its way to the low-pressure cylinder, through re-heaters filled with tubes. containing high-pressure steam. The boilers and the engines are designed for steam of 100 pounds pressure per square inch above the atmosphere. The engines are intended to run 12 revolutions per minute. They have been in operation since Jan. 1, 1884; and during 17 weeks from Jan. 26 to May 24, pumped a daily mean quantity equal to 28,466,314 Winchester gallons against a mean head of 35 to 36 feet. The daily consumption of coal, with 15.59 per cent refuse, was 15,590 pounds; but an unknown quantity of steam was used to keep reserve Worthington pumps in running order, and to do some pumping with them, and for other purposes, so that the data are too inexact to afford a basis for the calculation of duty. It is to be hoped that the city of Boston may contribute the results of a wellconducted test of these important engines to engineering science, in a manner to commend itself to general confidence. "SUPERIOR. A hoisting-engine designed by Mr. E. D. Leavitt, jun., for the Calumet and Hecla copper-mine at Calumet, Houghton County, Mich., and built by the I. P. Morris Company, Philadelphia, in 1881, bears the above significant name. This fine engine forms the subject of a paper by its designer, read before the American Society of Mechanical Engineers at the Hartford meeting in May, 1881; published in the Transactions of the Society, vol. ii. pp. 106-121; and republished, with all the illustrations, in the American Machinist, vol. iv., No. 26, June 25, 1881. Only the briefest summary of its dimensions and constructive features will be here given. The cylinders are respectively 40 and 70 inches in diameter, vertical, 9 feet apart between centres, and have each a stroke of 6 feet, which, with a speed of 60 revolutions per minute, gives a piston speed of 720 feet per minute. The normal boiler-pressure is 135 pounds per square inch above atmosphere, equal to 10.19 atmospheres absolute, with initial pressure very little less, full admission to the point of cut-off, and prompt suppression. The valves are gridiron slides, four for each cylinder, with 16 ports each, and have only one inch travel. The admission valves of the high-pressure cylinder are under the control of a sensitive Porter governor, but are actuated by the piston of a small subsidiary steam-engine, automatically adjusted by the governor, giving a range of admission of from 0 to .6 of stroke. The low-pressure inlet-valves are set to close at 35 inches, equal to 48.61 per cent of stroke. All the cams for moving the valves are placed on a cam-shaft carried in brackets secured to the side of the main bed-plate, and also supported from the engine foundation, and driven by mitre-gears from the crank-shaft, which is of hammered steel, 18 inches in diameter, and 45 feet long, with journals 32 inches long. The crank-pin journal is 18 inches in diameter, and 24 inches long. Two re-heaters, one at each end, are placed between the cylinders, each having 941 brass tubes inch diameter, inch in thickness, and 60 inches long, presenting, therefore, an aggregate tube-surface of 1,540 square feet, equal to 14 per cent of the heating surface of the boilers. These tubes are filled with steam of boiler-pressure, and the passing steam is so guided among them by deflectors as to make all the tube-surface effective. Steam is supplied by five locomotive boilers, presenting in the aggregate 260 square feet of fire-grate area, and 11,000 square feet of water-heating surface, a ratio of 42.3 to 1; and 2.34 square feet of heating-surface for each indicated horse-power at the maximum, 4,700 indicated horse-power, when cutting off at half stroke in the high-pressure cylinder; an effort only required occasionally for short periods, when all the skips are at the bottom of the mine together. The boilers are 33.4 feet in extreme length, 110.5 inches wide at bottom of fire-box, 96.56 inches high over the fire-box, and 84 inches in diameter inside of the barrel, which has double and treble riveted, double-fished butt-joints. Each boiler has two furnaces 8 feet long, 4 feet wide, and 5.52 feet high above base ring; a combustion-chamber 2.92 feet long in rear of each furnace, and a common combustion-chamber for the two furnaces 4.08 feet long to the tube-sheet; and 118 iron tubes 3.5 inches in diameter outside, and 18 feet long between the tubesheets. The plates are all of best open-hearth steel, inch thick in the furnaces, and inch in the barrel and fire-box casing. There is no brick setting, but the outside is carefully clothed with non-conducting materials. There has been no regular test, save the test of daily performance, which is highly satisfactory. Indicator diagrams taken in regular work are very beautiful. PUMPING-ENGINE, PAWTUCKET, R.I. This engine, designed by Mr. George H. Corliss, and built by the Corliss Steam-Engine Company, Providence, is a horizontal, compound, receiver engine, with its cylinders placed side by side, but separated by the length of the crank-shaft, as in ordinary double or two-cylinder engines. The cylinders are respectively 15 and 30 inches in diameter, and the stroke, common to both, is 30 inches. The pump-pistons have a stroke also of 30 inches, and a diameter of 10.52 inches, and are keyed upon prolongations of the piston-rods of the engines, which extend through the pumps to cross-heads running in forked slides cast in one piece with the pump-heads farthest from the steam cylinders. The cylinders are sustained by hollow legs at their ends, which mask the steam and exhaust pipes. The pump-barrels are enclosed in firm rectangular plinths, which are securely connected, by ties and struts, with the steam-cylinders. Rectangular dies, resting on these plinths and firmly secured to them, serve as valve-casings, and air-chambers for the pumps, and as supports for the crank-shaft boxes, the centre of the crank-shaft being 9 feet 8 inches above the floor of the engine-room. Short connecting-rods, or front-links, 6 feet 2 inches in length, which extend from the cross-heads to wrist-pins in the forked upper extremities of cast-iron rockers, give these rockers a reciprocating motion upon centres 6 feet 2 inches below. These rockers spread out at the upper end to a width sufficient to take in two pins 5 feet apart between centres, to each of which two wrought-iron rods are secured, the four rods of each set meeting at their upper ends, where they are united by a pin which serves as the wrist-pin for one end of a connecting-rod 12 feet 6 inches long, extending to the wrist-pin of a crank on the fly-wheel shaft. Each set of four rods, in connection with the cast-iron rocker at their base, forms a rigid extension of the rocker upwards to just twice the height of the cast-iron portion, so that the two cranks on the fly-wheel shaft, which are set at right angles, are 30 inches in length, equal to the stroke of the steam and water pistons. A strong brace extends downward from each die, in a direct line from the crank-shaft, at an angle of 45 degrees, to the sole-plate near the supports for the lower ends of the rockers. The fly-wheel, 18 feet in diameter, running entirely above the floor, has a flat face 12 inches wide and 2 inches thick, with a central rib 5 inches wide, and is properly very light, as it has very little to do. All parts of the steam-cylinders, covers, and valve-chests, are steam-jacketed; but live steam is not introduced into the pistons. Normal boiler-pressure is 125 pounds per square inch above the atmosphere, and expansion in both cylinders is about twenty-fold. Water resulting from condensation in the jacket of the highpressure cylinder is returned directly to the boilers; and the drainage from the receiver, including that from the jacket of the low-pressure cylinder, is re-evaporated and superheated by passing through tubular re-heaters in the smoke-flues, and returned as superheated steam to the receiver. The valves and valve-gears are all of Mr. Corliss's well-known construction. Steam is furnished by three of Mr. Corliss's patent upright tubular boilers, each 4 feet in diameter and 14 feet long, of the same form and arrangement as those which furnished steam for the Corliss engine at the Centennial Exhibition in 1876. Each boiler has 560 square feet of heating-surface, and 19.63 square feet of fire-grate area. The escaping gases of combustion pass for a considerable distance through tubes surrounded by steam, and doubtless cause a good deal of superheating. Two distinct tests of this engine were made by Mr. Walter H. Sears, chief engineer of the Pawtucket Water-works, and Mr. Isaac R. Scott, president of the water board of Waltham, Mass.; one of 10 hours per day during two weeks, Tuesday, Aug. 6, to Monday, Aug. 19, 1878, excluding the two intervening Sundays, Aug. 11 and 18. The total run was therefore 120 hours, in 12 periods of 10 hours each, with 9 intervals of 14 hours each, and 2 of 36 hours each. The wood used for kindling fires, 2,126.5 pounds (89 pounds each day to each boiler), was estimated as coal at 45 per cent of its weight, equal to 957 pounds of coal, which added to 6,521 pounds of coal used in starting fires (271 pounds per day, per boiler) makes 7,478 pounds of coal, equal to 311 pounds of coal per day for each boiler, principally consumed by reason of the intervals when the engine was at rest. The coal used for pumping was 26,598.5 pounds; and all the coal used for starting fires and pumping, including the estimated coal value of the wood, was 34,076.5 pounds, of which 22 per cent was used in starting fires. (Only two boilers were used in this test.) The duty, calculated upon the capacity of the pumps, the mean resistance, and the whole number of pump-strokes for each 100 pounds of coal consumed, without deduction for ashes and residue, was 104,357,654 foot-pounds. A weir measurement, made Aug. 28, 1878, revealed a loss of action of 4.12 per cent, which was subsequently much reduced by a change of valves. The other test, of 24 consecutive hours' duration, begun Oct. 3, 1878, at 9 o'clock A.M., gave a duty, calculated on the capacity, mean resistance, and number of strokes of the pump, of 133,522,060 foot-pounds for each 100 pounds of coal burned while pumping, without deduction for ashes or residue. In this test, all three boilers were used. These results, which I see no reason to question, are the more remarkable when the small size of the engine, and its low speed, are taken into consideration. The space swept through by the piston at each revolution, or double stroke, is, for the high-pressure cylinder, only 6 cubic feet, for both cylinders, only 30 cubic feet; and at the normal speed, 52 revolutions per minute (the actual speed at the tests was 51.8), the velocity of the piston was only 260 feet per minute. Sets of diagrams from these cylinders show close conformity to normal action of the highly expanded steam. Confirmation of the accuracy of the results above given is to be found in the fourth annual report of the water commissioners and superintendent of water-works of the town of Pawtucket, dated Feb. 1, 1884. A table is there given in detail of the performance of this engine for each of the twelve months ending Dec. 31, 1883, of which the sums and means for the year are subjoined. Number of days when pumping was done, per month, 23.1 Total number of hours' pumping Hours and minutes per month Hours and minutes per day Total number of revolutions Revolutions per month 277.2 .3,852 h., 49 m. 321 h., 4 m. 13 h., 54 m. 10,698,618 891,551 |