Page:Encyclopædia Britannica, Ninth Edition, v. 20.djvu/263

Rh RAIL WAY 245 by a central bolt or pivot to the frame of the engine, so that the fore-wheels can swing to the curves of the line. On the Metro- politan, Metropolitan District, and North London Railways entirely, and on many large railway systems partially, where sharp curves are frequent, bogie-engines are employed, and with great advan- tage in facilitating traction. Another device for the same purpose is the use of radial axles, that is, axles either at the forepart or the back of the engine, which by their axle-boxes slide laterally between circularly formed guides on entering and on leaving curved parts of the way, and so maintain a radial position at right angles to the line of rails. American practice, many years since, arrived at two leading types of locomotive for passenger and for goods traffic. The passenger locomotive has eight wheels, of which four in front are framed in a bogie, and the four wheels behind are coupled drivers. This is the type to which English practice has been approximating. The tender is carried on eight wheels, disposed under two trucks or bogies, fore and aft. Goods locomotives are made with eight wheels and with ten wheels, of which, in each case, the leading pair of wheels are connected with a swing bolster and radius bar, to conform laterally and radially to curves. As the speed increases a more than proportional increase in the engine-power is necessary to draw a given train. Thus, if an engine and tender, weighing together 40 tons and exerting a given tractive force, takes, say, forty loaded carriages, weighing 360 tons, at 20 miles per hour on a level, the loads which it could take if it exerted the same tractive power at higher speeds would be only as follows : At 20 miles per hour, 40 carriages, weighing 360 tons. ' 30 30 200 ,, 40 21 144 50 15 ,, 106 ,, 60 11 75 The influence of gradients also is very important. If an engine and tender, weighing together 40 tons, is capable of drawing a maximum train of, say, forty-two loaded carriages, weighing 420 tons, at 20 miles per hour on a level, it would only draw the following loads at the same speed on the following inclines : Level 42 carriages, weighing 420 tons. Incline 1 in 600, 34 340 300, 27 ,, 270 150, 20 200 100, 15 ,, 150 75, 12 120 50, 9, 90 40, 6 , 65 30, 5 , 45 20, 3 , 24 10, nil , nil This is the reason why the older railways were made nearly level at an enormous cost, the elder Stephenson's policy being to incur a large expenditure in construction in order to avoid otherwise heavy inclines and heavy expenses. The ruling gradient of the Liverpool and Manchester Railway was fixed at 1 in 900, excepting, of course, the inevitable inclines at Rainhill summit, for working which special provision was made ; that of the next great line, the London and Birmingham, was fixed at 1 in 330 ; on the Great Western Railway, one of the earliest made lines, the ruling inclina- tion is 1 in 1320 for the greater part of the way. Locke, as already explained, initiated the system of cheaply constructed railways, as the facilities for increasing the power of locomotives became better understood ; he constructed lines with long steep gradients, some of them 1 in 70, 1 in 75, 1 in 80. The Great Northern Railway, of comparatively recent origin, was constructed on a ruling gradient of 1 in 200 ; and, in general, the more recently made lines have the steepest gradients. Steep railways are generally also lines of frequent curves, which is another cause of loss of locomotive power. Moreover, the ruling speeds, as they may be called, have in the course of years increased. Thus in every way more powerful engines are now needed than in the early days of railways. The fundamental characteristics of English practice are fairly represented by a few types of locomotives. Take first an express passenger locomotive, which stands on a wheel base the distance apart of the centres of the extreme axles of 15 feet 4 inches. The cylinders are inside and are 16 inches in diameter, with a slide of 22 inches. The driving-wheels are 7 feet in diameter. The fire- grate has an area of 18 square feet, and the heating surface of the fire-box and flue-tubes taken together is 1339 square feet. The total weight of the engine in working order is 28 tons 6 cwt., of which nearly 12 tons are driving weight, the weight at the driving- wheels. The tender stands on three pairs of wheels and weighs about 16 tons, with, in addition, 1780 gallons or 8 tons of water when filled, and 3 tons of coal. The " Lady of the Lake " is an express passenger locomotive, one of a class which was designed by Mr John Ramsbottom with special regard to the running of express trains on the northern division of the London and North - Western Railway. The cylinders are "outside"; they are 16 inches in diameter, with 24 inches of stroke, and the driving-wheels are 7 feet 7 inches in diameter. The fire-grate has an area of 15 square feet, and there is over 1000 square feet of heating surface. The engine weighs 27 tons in working order and the tender 17, together 44 tons. The tender is fitted with Mr Ramsbottom's apparatus for picking up feed-water whilst running : a scoop is let down from the bottom of the tender and dips into water contained in a long open trough, laid between the rails, from which it is scooped up into the tanks. The minimum speed at which this operation can be effected is 22 miles per hour. By the aid of the water-lifter this express engine has been enabled to run the whole distance from Holyhead to London 264 miles in one continuous run, at an average speed of 42 miles per hour, taking a train of eight or nine carriages, and consuming 27 Ib of coal as fuel per mile run. An express passenger locomotive having 18 -inch cylinders and four-coupled driving-wheels, 7 feet in diameter, with a four-wheel bogie in front under the smoke -box, was designed by Mr T. W. Johnson for the traffic of the Midland Railway. The engine stands on eight wheels, forming a base 21 feet long. It weighs about 42 tons in working order, and with the tender, including coal and water, about 68 tons. The average load taken by engines of this class is fourteen carriages at the time-bill speed of 50 miles per hour, over gradients of from 1 in 120 to 1 in 130, with a consump- tion of 28 ft> of coal per mile run. The engine can take as a maxi- mum load seventeen carriages between Manchester and Derby, over ruling gradients of 1 in 90 and 1 in 100 for 10 miles, at a speed up the inclines of 35 miles per hour, and on levels and falling gradients at 50 miles per hour. The carriages weigh, with passengers, 11 tons each, making up a train of the gross weight of 187 tons. The express passenger engines on the Great Northern Railway (fig. 40), designed by Mr Patrick Stirling, have outside cylinders, 18 FIG. 40. Express locomotive ; Great Northern Railway. inches in diameter, and a single pair of 8-feet driving-wheels. It is one of the most recent developments of the single-wheel engine. It is placed on eight wheels, of which the first four are framed in a bogie, or truck, pivoted on a centre under the smoke -box. The cylinders are placed outside, and between the wheels of the bogie at each side. They are 18 inches in diameter, with a stroke of 28 inches, dimensions which, taken together, exceed in magni- tude those of any other engine for English passenger-traffic. The driving-wheels are 8 feet 1 inch in diameter and the bogie-wheels 3 feet 11 inches. The engine weighs 38 tons in working order, the distribution of the weight being as follows : Leading bogie-wheels ) 15 tong ( 7 tons Hind >, ) " ( 8 Driving-wheels 15 Hind wheels 8 Total weight in working order 38 The pivot of the bogie is 6 inches nearer the hind than the front axle, these being 6 feet apart. By this disposition the' bogie appears to lead better than if the pivot were, as usual, equidistant between the axles. The working pressure in the boiler is 140 R per square inch. There are 217 brass flue-tubes, 1^- inches in diameter, presenting a heating surface for evaporation of upwards of 1000 square feet. There is in all 1165 square feet of surface, and there is 17 '6 square feet of grate siirface. Mr Stirling, on the question of single -wheel versus coupled wheels for passenger locomotives, states that he constructed two classes of engines, one class with four 6^-feet wheels coupled, the other with a single pair of 7-feet driving-wheels. The boilers of the two classes were alike; also the cylinders, which were 17 inches in diameter, with 24 inches of stroke. The pressure in the boilers was 140 Ib. With like trains the single-wheel engine had the better of it ; in fact, it generally beat the coupled engine in time, running from King's Cross to Potter's Bar, a distance of nearly 13 miles, nearly all uphill, the gradients varying from 1 in 105 for 2 miles to 1 in 200. Engines of the class of the 8-feet-wheel engine travel between King's Cross and Leeds or York. The steepest gradients on the route are met with on leaving Leeds, ascending 1 in 50, besides the gradient 1 in 105 leaving King's Cross. Trains of from sixteen to twenty- two carriages are taken from King's Cross station with ease ; and on several occasions twenty-eight carriages have been taken, and time has been kept. On one occasion a distance of 15 miles in