Entered December 4, 1902, at Indianapolis, Ind., as Second-class Matter, under act of Congress of March 3, 1879 VOL. 36 No. 3 INDIANAPOLIS, IND. Plate II-Duplex Pump (Up-Stroke of Low-Pressure Piston). Plate II of the New York Air Brake Series of the Locomotive Firemen's Magazine Educational Charts shows a sectional and perspective view of a duplex pump, with the low-pressure piston making its up-stroke, and with the high-pressure piston at rest at the lower end of its cylinder. The colors used with this plate are red, indicating main reservoir pressure; dark brown, indicating a pressure of about 45 pounds; orange, indicating atmospheric pressure; blue, indicating live steam; and light blue, indicating exhaust steam. These colors indicate to the reader the course of the steam as it goes through the various steam ports and passages into and out of the steam cylinders, and also the manner in which the atmospheric air is taken into the low-pressure air cylinder D, under the low-pressure piston, and how the air in front of, or above, this piston is compressed and driven out through the passagè v, past the upper intermediate air valve 2 D P 11, through passage w, into the high-pressure air cylinder C. They also represent the pressures that are present in the various cylinders, and steam and air passages, in the pump, after it has been at work long enough to obtain the full main reservoir pressure. MARCH 1904 The plate serves, too, to represent the pump as starting from rest, but it should be remembered that as the pump starts from rest we do not have a pressure of 45 pounds, or nearly 45 pounds, in the low-pressure air cylinder until 45, or more, pounds pressure has been accumulated in the main reservoir, which will be the case after the pump has made a few strokes. Referring to Plate II, it will be seen that live steam is represented by the deep blue coloring as entering through the steam pipe from the boiler into the chambers containing the slide valves 2 DP 5, through passage c, filling the high-pressure steam cylinder A, and through passage b into the low-pressure steam cylinder B, under the low-pressure steam piston, and, as indicated, forcing this piston, together with the low-pressure air piston, toward the upper end of its stroke. The steam in the low-pressure cylinder B, above the steam piston, is represented by the light blue coloring as passing out through the steam passage d, the exhaust cavity e of the slide valve, and the exhaust port f into the exhaust pipe, and thence to the atmosphere. From the way in which the steam enters the pump, with the pistons in the positions shown, it will be seen that the high pressure steam piston in cylinder A must remain stationary until the lowpressure steam piston in cylinder B has arrived at the end of its up-stroke, and the tappet plate 1 D P 20 has engaged the button head on the end of the valve stem 1 D P 7 and moved its slide valve upward so as to bring the steam passage c into communication with the exhaust port f. This position of the slide valve and low-pressure steam and air pistons will be shown in Plate III. Referring to the air end of the pump, it will be seen that atmospheric air is indicated by the orange coloring as passing into the low pressure air cylinder past lower receiving valve 2 D P 9 and through passage t behind the low-pressure piston. From this we learn that, as the low-pressure piston is moving upward and compressing the air in front of it, and is forcing this compressed air over into the high-pressure air cylinder, it is forming at the same time a vacuum in cylinder D behind this piston, which is being filled with air from the atmosphere, so that when the low pressure piston reaches the upper end of its stroke, and has discharged the contents of cylinder D into cylinder C, cylinder D is filled with air at atmospheric pressure ready to be compressed when the low-pressure piston starts upon its downward stroke. From this plate it will also be learned that the low-pressure piston is what may be termed the lead piston; that always when the pump starts from rest the lowpressure piston is the one which starts first. Further, on the up-stroke of the lowpressure piston it will be seen that two of the air valves are lifted from their seats while the other four remain upon their seats; that is, the lower air receiving valve 2 D P 9 raises to admit atmospheric air beneath the low-pressure piston while the intermediate air valve 2 D P 11 raises to allow the compressed air to pass from the low-pressure cylinder into the highpressure cylinder. When the low-pressure piston has reached the end of its up-stroke and has shifted the slide valve 2 D P 5, then the high-pressure piston will commence its up-stroke. This stroke will be shown in Plate III, and the courses which the air and steam are taking during that stroke will be indicated by the colors shown on that plate. It should be observed that the lowpressure piston, shown as moving up and compressing the air in front of it, is forcing air up into the automatic oil cup, which is forming a pressure upon the surface of the oil in that cup. The Pennsylvania Tunnel at New York City. Rapid progress is being made in the initial stages of the great engineering project by which the Pennsylvania Road is to secure a terminal station in Manhattan Island and through connections with the Long Island Railroad system. The work of clearing away the buildings on the four large city blocks that will be occupied by the passenger station is well under way, two of these blocks, over a third of a mile in total length, being The shafts from ready for excavation. which the work of tunneling will be carried through have been sunk; and before many weeks have passed the whole stretch of work from the portal in Jersey to the portal in Long Island will be covered with as big a force as can be crowded upon it. The location and profile of the tunnel are shown in the accompanying diagrams. Commencing at the western approach to the tunnel, two tracks will enter the western end, known as the Hackensack portal, in the face of Bergen Hill, which runs parallel with the Hudson River. From this point to the portal which marks the exit on Long Island will be a distance of a trifle under six miles. The two tracks will pass through the hill in separate tunnels, which will extend to the Weehawken shaft, a distance of a little over one mile. On this portion of the work the tunneling will be of standard construction, but from the Weehawken shaft to the shaft on the western shore of Manhattan Island, a distance of about 6,000 feet, the two tracks will be carried in separate circular tubes of a construction hereinafter described. The line will descend from the Hackensack portal to its lowest point below the North River on a grade of 1.3 per cent. and at its lowest level the bottom of the tubes will be about 90 feet below mean high water of the North River. From this point, for a distance of 2,000 feet, the line will rise on a grade of 0.53 per cent. and then for another 3,000 feet it will ascend on a grade of a little under 2 per cent. to a point between Ninth and Tenth avenues on Manhattan Island. At the Manhattan shaft, going eastward, the tubular construction ceases, and the two tracks diverge into two triple parallel tunnels, with three tracks in each-the main line and two sidings. The triple tunnels extend for about 1,100 feet, when SECTIONAL VIEW OF PENNSYLVANIA RAILROAD TUNNEL NOW UNDER CONSTRUCTION BENEATH THE HUDSON RIVER Total length of tunnel from New Jersey to Long Island, six miles. Outside diameter of shell, 23 feet (From Scientific American) istence. It will extend from Seventh to Ninth avenue, and from Thirty-first to Thirty-third street, and will cover a great parallelogram measuring about 460 feet north and south by about 1,800 feet east and west. The details of the station and The portion of the tunnel thus far described is under the charge of Charles M. Jacobs as chief engineer. The portion now to be described, extending from the station to the end of the tunnel in Long Island, is under the charge of Al fred Noble as chief engineer. The latter division, which commences just east of Seventh avenue, consists of two lines of three-track arched tunnels, one below Thirty-second street, and the other below Thirty-third street. This form of construction continues for 1,650 feet, when each set of three tracks merges into a double track carried in a concrete-arched tunnel for a distance of 2,400 feet. At Second avenue the tracks swing to the left, and are carried in two concretelined tubes beneath the East River to East avenue, a distance of about 6,000 feet; and from East avenue to the end of the tunnel at Thompson avenue, a distance of 3,700 feet, the tracks are carried beneath four separate concrete arches. The tracks descend from Seventh to Fifth avenue on a 0.5 per cent. grade, and from Fifth avenue to the lowest point beneath the East River on a 1.5 per cent. grade, from whence they rise. on a 1.25 per cent. grade to surface. On the whole of the tunnel work thus outlined, that lies beneath the East Riyer and the land, it is not anticipated that any conditions will be encountered that will call for special construction and present any obstacles to the smooth and uninterrupted prosecution of the work. The borings indicate that beneath the land the tunnels will be driven chiefly through rock, and under the East River through fine to coarse sand and gravel. In passing below the North River, however, it will be necessary, in order to avoid going to a depth which would involve heavy grades that would be expensive to operate, to carry the tunnel through a river mud and silt that are of such consistency that the question of the stability and perfect alignment of the tunnel calls for special study. Although the silt is sufficiently firm to preserve the tunnel itself in perfect alignment, it was considered by Mr. Jacobs that provision should be made for carrying the moving train loads independently of the tunnel shell. It was considered that if the heavy Pullman trains, weighing with their locomotives as much as 600 to 700 tons, were allowed to bear directly upon the shell of the tunnel, their weight and impact might produce a settlement and set up bending stresses that would result in fracture and leakage. The problem will be solved by driving a line of very massive cast-iron screw piles through the floor of the tubes, at 15-foot intervals, with their heads projecting within the tubes, and capping the piles with a sys tem of heavy transverse girders and longitudinal stringers, upon which the track rails will be laid. The heavy load and severe impacts of the trains will thus be received by the piles, and should there be any slight settlement of the piles under load, the movement would not affect the tubes, which would serve their proper purpose as an envelope for the protection of the trains. The piles will be driven either to rock or to a bearing capable of sustaining a pre-determined load without settlement. Of the 24,049 feet of castiron single-track tunnel, 12,174 feet will be reinforced with screw piles. The cast-iron shell consists of boltedup segments, each 30 inches in length and containing eleven segments and a key-piece in each. The shell is 2 inches in minimum thickness, and the segments are flanged on all sides, the joints being planed and provided with five or six 11⁄2inch bolts, as the case may be. At stated intervals corresponding to the position of the piles, plates are cast with flanged holes, which are temporarily closed by a cast-iron block. After a certain length of shell has been driven, it will be bulkheaded off, placed under pneumatic pressure, and the piles will be screwed down from the interior of the shell. The piles are 27 inches in outside diameter, with 14-inch thickness of shell, and they are made in 7-foot sections. The lower end of the pile is square, and is provided with one turn of a wide screw cast integrally with the pile, the outside diameter of the screw being 4 feet 8 inches. The pile is screwed down by means of a special hydraulic ratchet arrangement bolted to the head of the pile, and as one section is carried down, another 7-foot section will be bolted to it, the process continuing until rock or impenetrable bottom is reached. The core of mud inside the hollow pile will be excavated for a depth of 12 feet below the tunnel tube, and the space filled in with concrete. After the pile has been driven, the last section will be removed, cut to exact length, to bring it flush with the floor of the tube, and replaced and bolted. The upper end of the pile after it has been filled with concrete will be closed by a bolted disk. Above the cap of each pile will be bolted heavy transverse girders, and upon these girders, bridging the intermediate space of 15 feet, will be a pair of longitudinal girders, upon which the railroad tracks will be laid. By this method the weight and impact of the heavy trains will be borne directly by the piles, and the iron |