velocity, with which result divide the tractive force, and from the quotient subtract the weight of the engine and tender in tons. These Rules may be illustrated by the following example: Required the load which a locomotive-engine with cylinders 17 inches diameter and 24 inches length of stroke, with a driving-wheel 5 feet diameter, will take on an incline of 1 in 70 at a speed of 20 miles per hour, boiler pressure 140 lbs. per square inch, weight of engine and tender 55 tons? The tractive force which the engine is capable of exerting is 172 × 24 бо 115.6 lbs. for each lb. of effective pressure per square inch on the pistons. The boiler-pressure of 140 lbs. per square inch gives 140×2=105 lbs. effective pressure, which multiplied by the tractive force in lbs. = 105 × 1156 gives 12,138 lbs. as the total tractive force exerted by that engine. The effective mean pressure on the pistons equivalent to that tractive 5 feet X 12 X 12138 force at the rails is = 17 X 17 X 24 The resistance due to gravity is= 2240 105 lbs. per square inch. 70 gradient =32 lbs. per ton. The resistance due to the velocity is=. 20 X 20 +8= 10*34 lbs. and with 50 per cent. added, is equal to 15:51 lbs. per ton. The load which the engine will take will be=; 12138 32+15°51 -55 = 200 tons and taking 8 tons as the average gross weight of each wagon, the train 200 would consist of- 25 loaded wagons. 8 The total weight of the engine, tender and train is 255 tons, and the resistances due to velocity and gravity are = 32 + 15°51 = 47 51lbs. per ton, or = 255 × 47'51 = 12115 lbs. for the train. 20 m. x 1760 yds. × 3 ft. The train moves 60 minutes and the power exerted by the engine is= horse-power. 1760 feet in one minute, 12115 × 1760 33000 =646 indicated The coal burnt per indicated horse-power would be at least 2 lbs. per =80 lbs. of coal per mile, or 80 × 20 = 1600 lbs. of The evaporation would be, say, 9 lbs. of water per lb. of coal, and it would require 1600 × 9 lbs. 10 lbs. per gallon =104 gallons of water per hour. The number of revolutions of the driving wheel would be = 20 × 1760 × 3 60 × 5 feet X 3'1416 = 112 per minute; for each revolution of the wheel the piston moves twice the length of the stroke. The speed of the piston = 448 feet per minute. capable of developing at that speed and pressure is= would be 2 feet stroke x 2 x 112 revolutions The total power the above locomotive engine is 17 diam. of cylinder x 17 diam. of cylinder x 7854 × 2 cylinders × 105 lbs. pressure x 448 ft. speed of piston 33,300 647 horse-power. The Consumption of Coal in Express Locomotive Engines is less than in slow-running engines. It averages 2 lbs. per indicated horse-power per hour in express-engines, and 3 lbs. per indicated horse-power per hour in goods-engines. The Cylinders of a Locomotive Engine should be of best close-grained cast-iron, as hard as it can be worked, and free from all defects. Two cylinders of equal diameter are invariably employed in locomotives, compound locomotives excepted. The diameter of the cylinders, shown in Fig. 73, may be found by the following formula:— Fig. 73.-Cylinder of a Locomotive Engine. on the driving wheels, equal to 480 lbs. per ton, or = 214, for D= the diameter of the driving wheels on the tread in inches. d = the diameter of each of the two cylinders in inches. Then, d = Example.-Required the diameter of the cylinders of a passenger locomotive-engine having a weight on the driving wheels of 279 tons: diameter of driving wheels 7 feet: boiler-pressure of steam 160 lbs. per square inch length of stroke 26 inches. = Then d=279 tons x 2240 lbs. x 214 x 84 inches 361=19 inches, 160 lbs. pressure x 75 x 26 the diameter of each of the cylinders of that locomotive. The Area of each Steam-Port should not be less than the area of cylinder divided by 12'5, which is an average proportion. The Length of the Steam-Ports should in no case be less than= diameter of cylinder in inches multiplied by 83, but rather diameter of cylinder in inches multiplied by '9. Width of Steam-Port the area of the steam-port divided by the length of the steam-port. The Area of the Exhaust Port should not be less than the area of the cylinder, which is a good proportion. The Lap of the Slide-Valve is generally about width of steam-port multiplied by 73. The Lead is frequently inch. = The Diameter of a Steel Piston-Rod should be diameter of cylinder in inches multiplied by 15. The Speed of the Piston is from 400 to 1000 feet per minute, according to the class of engine. The Width of Steel-Slide Bars may be diameter of piston rod, multiplied by 113. The thickness of the middle part of steel-slide bars is generally equal to ths the width of the bar. The Area of the Sliding-Surface of the Slide-Block in square inches on each slide-bar should not be less than = diameter of cylinder in inches, multiplied by 2.2, when the blocks are of chilled cast-iron. Metallic-Packing for the Piston-Rods of Locomotives. - Ti.e glands of the stuffing-boxes of the piston-rods and valve-spindles of locomotives using steam of very high pressure should be packed with metallic packing. A simple and efficient form of metallic-packing for this purpose is shown in Figs. 74-76. It consists of a ring or sleeve of soft metal placed in an ordinary stuffing-box. The faces of the gland and bush are bevelled, at an angle of 45°, and the ends of the sleeve are coned to correspond. This packing is liable to leak slightly when first applied, but the leakage disappears after a few days working. A piece of ordinary round corepacking mav he placed under the gland at the top of the metallic-packing, to give it a little elasticity and prevent the escape of any steam which may leak past the sleeve. The sleeve may either be solid or in halves arranged as shown in Fig. 73. The depth of the sleeve should not be less than the diameter of the piston-rod in inches x 1.8, but rather diameter of the piston-rod in inches x 2.25. The mixture of metal of the metallic-packing consists of 76 per cent. of lead, 14 per cent. of tin, and 10 per cent. of antimony. It requires to be efficiently lubricated with good oil. The Weight on the Driving Wheels of a locomotive-engine may be found by the following formula, in which the notation is the same as that in the previous formula: Example:-Required the weight on the driving wheels of the locomotiveengine described in the previous example. Then 19 × 19 inches x 26 inches x 160 lbs. × 75 = 62496 lbs. ÷ 84 inches x 214 2240279 tons, the weight required on the driving-wheels of that locomotive-engine. Various Types of Locomotives are used on different railways, a few of which are briefly described in the following pages as representative examples of modern locomotive practice. Coupled engines are generally used on lines with the heaviest gradients, and single engines for moderately heavy gradients and fast trains, although in some cases single engines are employed on heavy gradients. Single engines slip more than coupled engines. The slip of coupled engines, when the rails are not sanded, probably averages from 5 to 12 per cent., and of single engines from 8 to 16 per cent. That is, a single engine may make from 108 to 116 revolutions, where it should only make 100 revolutions. By the adoption of efficient steam-sanding apparatus, by which a fine spray of sand is blown under the treads of the wheels, the slip may be reduced to a minimum, and single engines are enabled to surmount heavy gradients with facility. Single engines generally cost less in repairs, run more freely, and are more economical in fuel than coupled engines. The adhesive power of driving wheels increases with the diameter, the larger the wheel the better the frictional hold on the rails. Bogies are of great advantage to locomotives running on curved lines. The Locomotive shown in the Frontispiece is a single Bogie. Express Passenger-Engine designed by Mr. S. W. Johnson, locomotivesuperintendent of the Midland Railway. The following are the leading dimensions of this locomotive :— Cylinders. The cylinders are 19 inches diameter, and the length of stroke 26 inches. The steam-ports are 173 inches long and 1 inches wide. The valves are piston-valves, 8 inches diameter, and have a lap of 1 inches, and inch lead in full gear. Cast-Steel Wheels.-The diameter of the engine bogie-wheels is 3 feet 10 inches; driving-wheels, 7 feet 9 inches; trailing-wheels, 4 feet 4 inches; and the tender bogie-wheels are 3 feet 6 inches diameter. The thickness of the tyres on the tread is 3 inches. Steel Boiler. The working pressure of the steam is 180 lbs. per square inch. The barrel of the boiler is telescopic, 10 feet 6 inches long, and 4 feet 1 inches internal diameter. The length of the fire-box shell is 8 feet. The thickness of the barrel-plates is inch; fire-box shell frontplate, 1; fire-box top, sides, and back, inch; and smoke-box tubeplate, inch. There are 228 copper tubes, of 1 inches external diameter. Copper Fire-Box.-The tops, sides, and back are inch thick, and the tube-plate is inch thick. The length of the fire-box, inside, at the bottom, is 7 feet 3 inches, and its width is 3 feet 4 inches. Heating-Surface and Fire-Grate Surface. The heating-surface of the fire-box is 147 square feet, and of the tubes, 1,070 square feet; the total heating-surface being 1,217 square feet. The area of the fire-grate surface is 245 square feet. Weight of Engine and Tender in Working Order.-Engine-bogie, 16 tons 16 cwt. 3 qrs.; driving, 18 tons; trailing, 14 tons 16 cwt. I qr.; total, 50 tons 3 cwt. Tender-with tank full of water and with 3 tons of coal-leading-bogie, 26 tons; trailing-bogie, 23 tons 2 cwt. I qr.; total, 49 tons 2 cwt. I qr. The total weight of the engine and tender is 99 tons 5 cwt. I qr. The centre of the boiler from the rails is 8 feet 1 inch. The total length of the engine and tender, over the buffers, is 58 feet 11 inches. The gross tractive power is 14,803 lbs. The adhesive power, with steam-sanding, is 11,100 lbs. The capacity of the tender is 4,000 gallons of water and 5 tons of coal. Table 6A-PERFORMANCES IN WORKING EXPRESS TRAINS BETWEEN NOTTINGHAM AND LONDON, OF A LOCOMOTIVE-ENGINE OF THE SAME |