adhesion given in column 3 by 7% gives the tons of 2000 lbs. that the engine is capable of hauling on a straight and level track, column 7, at slow speed The weight of engines given in these tables will be found to agree generally with the actual weights of locomotives recently built, although it must not be expected that these weights will agree in every case with the actual weights, because the different builders do not build the engines alike. The actual weight on trucks for eight-wheeled or ten-wheeled engines will not differ much from those given in the tables, because these weights depend greatly on the difference between the total and rigid wheel-base, and these are not often changed by the different builders. The proportion between the rigid and total wheel-base is generally the same. The rule for finding the tractive power is: Leading American Types of Locomotive for Freight and Passenger Service. 1. The eight-wheel or "American" passenger type, having four coupled driving-wheels and a four-wheeled truck in front. 2. The ten-wheel" type, for mixed traffic, having six coupled drivers and a leading four-wheel truck. 3. The "Mogul" freight type, having six coupled driving-wheels and a pony or two-wheel truck in front. 4. The "Consolidation " type, for heavy freight service, having eight coupled driving-wheels and a pony truck in front. Besides these there is a great variety of types for special conditions of service, as four-wheel and six-wheel switching-engines, without trucks; the Forney type used on elevated railroads, with four coupled wheels under the engine and a four-wheeled rear truck carrying the water-tank and fuel; locomotives for local and suburban service with four coupled driving-wheels, with a two-wheel truck front and rear, or a two-wheel truck front and a four-wheel truck rear, etc. "Decapod" engines for heavy freight service have ten coupled driving-wheels and a two-wheel truck in front. Classification of Locomotives (Penna. R. R. Co., 1900).-Class A, two pairs of drivers and no truck. Class B, three pairs of drivers and no truck. Class C, four pairs of drivers and no truck. Class D, two pairs of drivers and four-wheel truck. Class E, two pairs of drivers, four wheel truck, and trailing wheels. Class F, three pairs of driving-wheels and twowheel truck. Class G, three pairs of drivers and four-wheel truck. Class H, four pairs of drivers and two-wheel truck. Class A is commonly called a "four-wheeler "; B, a "six-wheeler " ; D, an eight-wheeler," or "American" type; E, "Atlantic type; F, Mogul "; G, "ten-wheeler "; H, Consolidation.' Steam-distribution for High-speed Locomotives. (C. H. Quereau, Eng'g News, March 8, 1894.) Balanced Valves.-Mr. Philip Wallis, in 1886, when Engineer of Tests for the C., B. & Q. R. R., reported that while 6 H.P. was required to work unbalanced valves at 40 miles per hour, for the balanced valves 2,2 H.P. only was necessary. Effect of Speed on Average Cylinder-pressure.--Assume that a locomotive has a train in motion, the reverse lever is placed in the running notch, and the track is level; by what is the maximum speed limited? The resistance of the train and the load increase, and the power of the locomotive de.. creases with increasing speed till the resistance and power are equal, when the speed becomes uniform. The power of the engine depends on the average pressure in the cylinders. Even though the cut-off and boiler. pressure remain the same, this pressure decreases as the speed increases; because of the higher piston-speed and more rapid valve-travel the steam has a shorter time in which to enter the cylinders at the higher speed. The following table, from indicator-cards taken from a locomotive at varying speeds, shows the decrease of average pressure with increasing speed: Miles per hour. Average pressure per sq. in.: 46 51 51 53 54 57 60 66 224 248 248 258 263 277 292 321 51.5 44.0 47.3 43.0 41.3 42.5 37.3 36.3 46.5 46.5 44.7 43.8 41.6 39.5 35.9 .... The "average pressure calculated" was figured on the assumption that the mean effective pressure would decrease in the same ratio that the speed increased. The main difference lies in the higher steam-line at the lower speeds, and consequent higher expansion-line, showing that more steam entered the cylinder. The back pressure and compression-lines agree quite closely for all the cards, though they are slightly better for the slower speeds. That the difference is not greater may safely be attributed to the large exhaust-ports, passages, and exhaust tip, which is 5 in. diameter. These are matters of great importance for high speeds.. Boiler-pressure.-Assuming that the train resistance increases as the speed after about 20 miles an hour is reached, that an average of 50 lbs. per sq. in. is the greatest that can be realized in the cylinders of a given engine at 40 miles an hour, and that this pressure furnishes just sufficient power to keep the train at this speed, it follows that, to increase the speed to 50 miles, the mean effective pressure must be increased in the same proportion. To increase the capacity for speed of any locomotive its power must be increased, and at least by as much as the speed is to be increased. One way to accomplish this is to increase the boiler-pressure. That this is generally realized, is shown by the increase in boiler-pressure in the last ten years. For twentythree single-expansion locomotives described in the railway journals this year the steam-pressures are as follows: 3, 160 lbs.; 4, 165 lbs.; 2, 170 lbs.; 13, 180 lbs.; 1, 190 lbs. Valve-travel. An increased average cylinder-pressure may also be obtained by increasing the valve-travel without raising the boiler-pressure, and better results will be obtained by increasing both. The longer travel gives a higher steam-pressure in the cylinders, a later exhaust-opening, later exhaust-closure, and a larger exhaust-opening-all necessary for high speeds and economy. I believe that a 20-in. port and 6-in. (or even 7-in.) travel could be successfully used for high-speed engines, and that frequently by so doing the cylinders could be economically reduced and the counterbalance lightened. Or, better still, the diameter of the drivers increased, securing lighter counterbalance and better steam-distribution. Size of Drivers.-Economy will increase with increasing diameter of drivers, provided the work at average speed does not necessitate a cut-off longer than one fourth the stroke. The piston-speed of a locomotive with 62-in. drivers at 55 miles per hour is the same as that of one with 68-in. drivers at 61 miles per hour. Steam-ports. The length of steam-ports ranges from 15 in. to 23 in., and has considerable influence on the power, speed, and economy of the locomotive. In cards from similar engines the steam-line of the card from the engine with 23-in. ports is considerably nearer boiler-pressure than that of the card from the engine with 174-in. ports. That the higher steam-line is due to the greater length of steam-port there is little room for doubt. The 23-in. port produced 531 H.P. in an 18-in. cylinder at a cost of 23.5 lbs. of indicated water per I.H.P. per hour. The 174-in. port, 424 H.P., at the rate of 22.9 lbs. of water, in a 19-in. cylinder. Allen Valves.-There is considerable difference of opinion as to the advantage of the Allen ported-valve. (See Eng. News, July 6, 1893.) Speed of Railway Trains.-In 1834 the average speed of trains on the Liverpool and Manchester Railway was twenty miles an hour; in 1838 it was twenty-five miles an hour. But by 1840 there were engines on the Great Western Railway capable of running fifty miles an hour with a train, and eighty miles an hour without. (Trans. A. S. M. E., vol. xiii., 363.) The limitation to the increase of speed of heavy locomotives seems at present to be the difficulty of counterbalancing the reciprocating parts. The unbalanced vertical component of the reciprocating parts causes the pressure of the driver on the rail to vary with every revolution. Whenever the speed is high, it is of considerable magnitude, and its change in direction is so rapid that the resulting effect upon the rail is not inappropriately called a "hammer blow." Heavy rails have been kinked, and bridges have been shaken to their fall under the action of heavily balanced drivers revolving at high speeds. The means by which the evil is to be overcome has not yet been made clear. See paper by W. F. M. Goss, Trans. A. S. M. E., vol. xvi. Engine No. 999 of the New York Central Railroad ran a mile in 32 seconds equal to 112 miles per hour, May 11, 1893. = circum. of driving-wheels in in. X no. of rev. per min. × 60 63,360 = diam, of driving-wheels in in. x no. of rev. per min. x .003 (approximate, giving result 8/10 of 1 per cent too great). Formulæ for Curves. (Baldwin Locomotive Works.) Approximate Formula for Radius. = decimals of 1 ft. W rigid wheel-base in feet. Approximate Formula for Swing. R radius of curve. S swing on each side of centre." Performance of a High-speed Locomotive.-The Baldwin compound locomotive No. 1027, on the Phila. & Atlantic City Ry., in July and August, 1897, made a record of which the following is a summary: On July 2d a train was placed in service scheduled to make the run between the terminal cities in 1 hour. Allowing 8 minutes for ferry from Philadelphia to Camden, the time for the 551⁄2 miles from the latter point to Atlantic City was 52 minutes, or at the rate of 64 miles per hour. Owing to the inability of the ferry-boats to reach Camden on time, the train always left late, the average detention being upwards of 2 minutes. This loss was invariably made up, the train arriving at Atlantic City ahead of time, 2 minutes on an average, every day. For the 52 days the train ran, from July 2d to August 31st, the average time consumed on the run was 48 minutes, equivalent to a uniform rate of speed from start to stop of 69 miles per hour. On July 14th the run from Camden to Atlantic City was made in 46% min., an average of 71.6 miles per hour for the total distance. On 22 days the train consisted of 5 cars and on 30 days it was made up of 6, the weight of cars being as follows: combination car, 57,200 lbs.; coaches, each, 59,200 lbs.; Pullman car, 85,500 lbs. The general dimensions of the locomotive are as follows: cylinders, 13 and 22 x 26 in.; height of drivers, 844 in.; total wheel-base, 26 ft. 7 in.; drivingwheel base, 7 ft. 3 in.; length of tubes, 13 ft.; diameter of boiler, 5834 in.; diameter of tubes, 134 in.; number of tubes, 278; length of fire-box, 1137% in.; width of fire-box, 96 in.; heating-surface of fire-box, 136.4 sq. ft.; heatingsurface of tubes, 1614.9 sq. ft.; total heating-surface, 1835.1 sq. ft.; tauk capacity, 4000 gallons; boiler-pressure, 200 lbs. per sq, in.; total weight of engine and tender, 227,000 lbs.; weight on drivers (about), 78,600 lbs. Locomotive Link Motion.-Mr. F. A. Halsey, in his work on "Locomotive Link Motion," 1898, shows that the location of the eccentricrod pins back of the link-arc and the angular vibrations of the eccentricrods introduce two errors in the motion which are corrected by the angular vibration of the connecting-rod and by locating the saddle-stud back of the link-arc. He holds that it is probable that the opinions of the critics of the locomotive link motion are mistaken ones, and that it comes little short of all that can be desired for a locomotive valve motion. The increase of lead from full to mid gear and the heavy compression at mid gear are both advantages and not defects. The cylinder problem of a locomotive is entirely different from that of a stationary engine. With the latter the problem is to determine the size of the cylinder and the distribution of steam to drive economically a given load at a given speed. With locomotives the cylinder is made of a size which will start the heaviest train which the adhesion of the locomotive will permit, and the problem then is to utilize that cylinder to the best advantage at a greatly increased speed, but under a greatly reduced mean effective pressure. Negative lead at full gear has been used in the recent practice of some railroads. The advantages claimed are an increase in the power of the engine at full gear, since positive lead offers resistance to the motion of the piston; easier riding; reduced frequency of hot bearings; and a slight gain in fuel economy. Mr. Halsey gives the practice as to lead on several roads as follows, showing great diversity : The link-chart of a locomotive built in 1897 by the Schenectady Locomotive Works for the Northern Pacific Ry. is as follows: Cylinders 20 x 26 in., driving-wheels 69 in., six coupled wheels, main rods 126 in., radius of link 40 in., lap 1% in., travel 6 in., Allen valve. DIMENSIONS OF SOME LARGE AMERICAN The four locomotives described below were exhibited at the Chicago Exposition in 1893. The dimensions are from Engineering News, June, 1893. The first, or Decapod engine, has ten-coupled driving-wheels. It is one of the heaviest and most powerful engines ever built for freight service. The Philadelphia & Reading engine is a new type for passenger service, with fourcoupled drivers. The Rhode Island engine has six drivers, with a 4-wheel leading truck and a 2-wheel trailing truck. These three engines have all compound cylinders. The fourth is a simple engine, of the standard American 8-wheel type, 4 driving-wheels, and a 4-wheel truck in front. This engine holds the world's record for speed (1893) for short distances, having run a mile in 32 seconds. |