Mr. Webb's object, in designing this engine was to secure in the first place a greater economy of fuel, and secondly, to do away with coupling rods, while at the same time obtaining greater adhesion, with the freedom of a single engine. The cost is much more than an ordinary locomotive, but the saving in fuel is said to be 20 per cent. over the other engines of the North Western Rail way. These engines run very sweetly, and are said to steam freely, although with only half the usual number of blasts; but from the small size of the high pressure cylinders, they are liable to slip when starting heavy trains, as the low pressure cylinders are not then effective, while the consumption of coal does not seem to show the saving that would have been expected, when compared with ordinary engines doing similar duty on other lines; for instance, the Great Northern single engine takes trains of the same weight with the same consumption of coal and at a somewhat higher speed. But it must, of course, be borne in mind in making such a comparison, that the fuel used may not be of the same quality.
Mr. Stirling, of the Great Northern, has adopted an entirely different type of engine to those last described. Holding strongly that single engines are more economical not only in running, but in repairs, and that cylinder power is generally inadequate to the adhesion, he has designed his magnificent well-known class of express engines. They have single driving wheels 8 ft. in diameter, with a four-wheel bogie in front and a pair of trailing wheels, 4 ft. diameter, behind. The frames are single, and inside of one solid piece; the cylinders are outside 18 in. diameter and 28 in. stroke; and the valve gear is of the usual shifting link description. The boiler is of Yorkshire plates, 11 ft. 5 in. long and 4 ft. diameter, and the steam pressure is 140 lb.; while the tractive power per lb. of steam in the cylinders is 94 lb. The fire-box is of copper, and the roof is stayed to the outer shell by wrought iron radiating stays screwed into both; a sloping mid-feather is placed in the fire-box.
FIG. 5.—GREAT NORTHERN RAILWAY.
The tubes, 217 in number, are of brass, 1-9/16 in. diameter; and the heating surface is in the tubes, 1,043 square feet; fire-box, 122 square feet; total, 1,165 square feet. The fire-grate area is 17.6 square feet. The wheel base from the center of the bogie pin to the trailing axle is 19 ft. 5 in., and the weight in working order is, on the bogie wheels, 15 tons; driving wheels, 15 tons; trailing wheels, 8 tons; total, 38 tons. The tender weighs 27 tons. These engines are remarkable for their efficiency; the traffic of the Great Northern Railway is exceedingly heavy, and the trains run at a high rate, the average speed of the Flying Scotchman being fifty miles an hour, and no train in the kingdom keeps better time. "Those who remember this express at York in the icy winter of 1879-80, when the few travelers who did not remain thawing themselves at the waiting-room fires used to stamp up and down a sawdusted platform, under a darkened roof, while day after day the train came gliding in from Grantham with couplings like wool, icicles pendent from the carriage eaves, and an air of punctual unconcern; or those who have known some of our other equally sterling trains—these will hardly mind if friendship does let them drift into exaggeration when speaking of expresses." The author well remembers how, when living some years ago at Newcastle-on-Tyne, it was often his custom to stroll on the platform of the Central Station to watch the arrival of the Flying Scotchman, and as the hands of the station clock marked seven minutes past four he would turn around, and in nine cases out of ten the express was gliding into the station, punctual to the minute after its run of 272 miles. Such results speak for themselves, and for the power of the engines employed, and one of the best runs on record was that of the special train, drawn by one of these locomotives, which in 1880 took the Lord Mayor of London, to Scarborough. The train consisted of six Great Northern coaches, and ran the 188 miles to York in 217 minutes, including a stop of ten minutes at Grantham, or at the average rate of 54½ miles an hour. The speed from Grantham to York, 82½ miles, with three slowing downs at Retford, Doncaster, and Selby, averaged 57 miles an hour, and the 59 miles from Claypole, near Newark, to Selby, were run in 60½ minutes, and for 22½ consecutive miles the speed was 64 miles an hour. In ordinary working these engines convey trains of sixteen to twenty-six coaches from King's-Cross with ease, and often twenty-eight are taken and time kept. Considering that the Great Northern main line rises almost continuously to Potter's Bar, 13 miles, with gradients varying from 1 in 105 to 1 in 200, this is a very high duty, while, with regard to speed, they have run with sixteen coaches for 15 miles at the rate of 75 miles an hour. Their consumption of coal with trains averaging sixteen ten ton carriages is 27 lb. per mile, or 8 lb. per mile less than the standard coupled engine of the North-Western with similar loads. Mr. Stirling's view, that the larger the wheel the better the adhesion, seems borne out of these facts; thus to take twenty-eight coaches, or a gross load of 345 tons, up 1 in 200 at a speed of 35 miles an hour, would require an adhesive force of 8,970 lb., or 600 lb. per ton—more than a quarter the weight on the driving wheels. These engines are magnificent samples of the most powerful express engines of the present day.
The London, Brighton, and South Coast Railway Company has in the last few years had its locomotive stock almost entirely replaced, and instead of seventy-two different varieties of engines out of a total of 233, which was the state of locomotive stock in 1871. a small number of well-considered types, suited to the different class of work required, are now in use. Mr. Stroudley considers—contrary to the opinion once almost universally held—that engines with a high center of gravity are the safest to traverse curves at high speed, as the centrifugal force throws the greatest weight on the outer wheels, and prevents their mounting; also that the greatest weight should be on the leading wheels, and that there is no objection to these wheels being of a much larger diameter than that usually adopted; in fact, by coupling the leading and driving wheels where the main weight is placed a lighter load is thrown on the trailing wheels, thus enabling them to traverse curves at a high speed with safety, while it permits of a larger fire-box being used; and these principles have been carried out in the newest class of engines, especially designed for working the heavy fast passenger traffic of the line.
The modern express engines are of two types. The first is a single engine with 6 ft. 6 in. driving wheels, and leading and trailing wheels 4 ft. 6 in. in diameter and a wheel base of 15 ft. 9 in. The frames are single, with inside bearings to all the wheels; the cylinders are inside, 17 in. diameter and 24 in. stroke. The boiler is 10 ft. 2 in. long and 4 ft. 3 in. diameter; the fire-box is of copper with a fire-grate area of 17.8 square feet, and the heating surface is in the tubes 1,080 square feet, fire-box 102 square feet; total, 1182 square feet. The weight in working order is about 35 tons. These engines have a tractive power of 89 lb. per pound of mean steam pressure in the cylinders, and their consumption of coal with trains averaging nine coaches is about 20 lb. per mile. The next type of engine designed has coupled wheels under the barrel of the boiler 6 ft. 6 in. diameter, with cylinders 17¼ in. diameter and 26 in. stroke, and were found so successful that Mr. Stroudley designed a more powerful engine of the same class, especially to take the heaviest fast trains in all weathers.
The 8:45 A.M. train from Brighton has grown to be one of the heaviest fast trains in the kingdom, although the distance it runs is but very short, while it is also exceptional in consisting entirely of first class coaches, and the passengers mainly season ticket holders; it often weighs in the gross 350 tons, and to take this weight at a mean speed of forty-five to fifty miles an hour over gradients of 1 in 264 is no light work.
FIG. 6.—LONDON, BRIGHTON, AND SOUTH COAST RAILWAY.