In Dec, 1902, appeared the first of a class of passenger express engine, which is to the modern Great Northern locomotive equipment what Mr. Stirling’s famous 8-ft. singles were to the same railway’s stock of 40 years ago. This noteworthy engine, No. 251, which is illustrated in Fig. 108, was the prototype of the standard G.N. express engine of to-day, and has so far justified its existence that there are now no fewer than 81 of the class.
So far as the general dimensions of cylinders, wheels and length are concerned, it was practically identical with the pioneer British “Atlantic,” No. 990, already described and illustrated in this monograph, but it was fitted with a much larger boiler, with a total heating surface of 2,500 sq. ft., and this innovation, which also increased the adhesion weight by several tons, has rendered it a far more powerful machine than the earlier engine.
A point not mentioned in connection with No. 990, though the feature is common to all the G.N.R. Atlantic engines, large and small, is the differential throw of the connecting and coupling rod pins. The coupling rod pins of the driving wheels are 6-in. in diameter, and have a throw of 11 1/2-in., whilst the connecting rod pins are 5-in. in diameter, turned eccentrically on the larger coupling rod pins, so as to give a throw of 12-in. Thus, whilst the stroke of the pistons is 24-in., the coupling rods travel in a circle of only 23-in. diameter, a reduction which at high speeds is of considerable importance in reducing the stress on those rods.
Another point of interest is the reversing gear, which has a vacuum lock of Mr. Ivatt’s invention fitted on the middle of the reverse shaft, this holding the gear in any set position.
The boiler was naturally the chief feature of interest in this engine. The barrel consisted of two rings, each of 5/8-in. steel plate, giving a total length of barrel of 16-ft. 3 7/8-in., the one nearest the smokebox being 8-ft. 6 3/4-in. long and 5-ft. 4 3/4-in. in diameter outside, and the other 8-ft. 1-in. long and 5-ft. 6-in. in diameter outside. The smokebox tube-plate was of the drumhead type, set inside the front ring, the actual length of the boiler between tube-plates being 16-ft., and the smokebox was also extended forward, its total internal length being about 5-ft. gin., and its internal diameter 5-ft. 11 1/2-in. The centre of the boiler was 8-ft. 8 1/2-in. above the level of the rails, and this height, with the large diameter of the smokebox, reduced the effective outside height of the chimney to i-ft. 7 1/2-in. ; this, however, was partly obviated by continuing the inner lining of the chimney 2-ft. 1-in. downwards into the smokebox, when it terminated in a bell mouth of 2-ft. diameter slightly below the level of the upper row of tubes, and 10 5/8-in. above the top of the 5 1/4-in. blast pipe.
The firebox was of a design not hitherto adopted in Great Britain, curving out from the shape of the boiler barrel at top to a wide base resting on the main engine frames. At the foundation ring it had an external length of 5-ft. 11-in., and a width of 6-ft. 9-in. In order to clear the driving wheels both the throat plate and the lower part of the firebox tube-plate were sloped backwards at an appreciable angle. The inside firebox had a length inside at the top of 5-ft. 5 7/16-in., a width inside at the bottom of 5-ft. 11 5/8-in., and a depth in front of 5-ft. o 1/2-in., and at back of 4-ft. 6 1/2-in. below the centre line of the boiler.
The crown plate was 1-ft. 2 3/16-in. and 1-ft. 0 11/16-in. above the centre line at front and back respectively. The heating surface of the firebox was 141 sq. ft., and of the 248 tubes, 16-ft. long by 2 1/4-in. diameter, 2,359 sq. ft., giving a total of 2,500 sq. ft. ; the grate area was 30-9 sq. ft.
Four safety valves of the Ramsbottom type, each 3-in. in diameter, were enclosed in a circular casing on the firebox, and were adjusted to blow off at a pressure of 175 lb. per sq. in.
Owing chiefly to the increased size of the boiler. No. 251 weighed considerably more than No. 990, the total weight of the engine in working order being 68 tons 8 cwt., distributed as follows: — On bogie wheels 17 tons 6 cwt., on each pair of coupled wheels 18 tons, and on trailing wheels 15 tons. The tender was of the standard type, and weighed 40 tons 18 cwt. with 3,670 gallons of water and 5 tons of coal. It differed from its predecessors, however, in being fitted with Mr. Ivatt’s patent water-pick-up apparatus, which has since been very largely adopted on the G.N.R. tenders.
As has already been mentioned, there are at present no fewer than 81 engines of the ” 251 ” class in service, their dates and numbers being as follows : —
|Date.||Doncaster No.||Engine No.||Date.||Doncaster No.||Engine No.|
For the purpose of instituting comparative trials with No. 292, a four-cylinder compound ” Atlantic,” which will be described in due course, No. 294 was altered to carry a working pressure of 200 lb. per sq. in. The result of these trials was that the compound engine showed a slight superiority in efficiency and economy, though scarcely to so marked a degree as to compensate for the enhanced prime cost of construction.
One of the later engines of the class. No. 1442, after running for about 40,000 miles, which included hauling the Royal train conveying the King and Queen to Leeds in the summer of 19o8, was temporarily withdrawn from service in the spring of 1909, and was overhauled in the shops and given an ” exhibition finish ” prior to being shown in the Machinery Hall at the Imperial International Exhibition at Shepherd’s Bush. It was shown standing on the present standard track of the G.N.R., with 100-lb. rails, and a portion of a water-trough in the four-foot, whilst alongside it was Mr. Stirling’s pioneer 8-ft. single, No. 1, which had been withdrawn from service in August, 1907, after completing upwards of 1,400,000 miles. This veteran had then been partially dismantled, and much of its internal gear and fittings removed, but for the purposes of exhibition it was thoroughly overhauled, and not only so, but renovated as far as possible in its original condition, and supplied with an old tender with wooden brake-blocks, as in 1870. It was also shown standing on a specimen of the track of that period, with steel rails weighing 80 lb. per yard.
An interesting series of comparative trials was instituted between engines of this class and standard L. & N.W.R. express locomotives during the summer of 1909. No. 1449 was “lent” to the L. & N.W.R. and put to work on the traffic between Euston and Crewe. The engine was worked by its own driver and fireman, with a L. & N.W.R. driver as pilot-man. During the same period the L. & N.W.R. locomotive No. 412, ” Marquis,” a four-coupled bogie engine of the ” Precursor” class, was at work on the G.N.R. main line, with its own driver and fireman and a G.N.R. pilot-man, running between King’s Cross, Doncaster and Leeds on alternate days, in competition with the Atlantic No. 1451. No official figures are forthcoming as to the results of these friendly trials, which naturally aroused considerable interest in the railway world. A somewhat similar test was made some time previously when a standard L. & Y. R. express engine was ” lent ” to and ran for some time on the Great Northern Railway, with one of that company’s tenders.
At the beginning of 1905 Mr. Ivatt made a notable departure by the introduction of a four-cylinder compound locomotive of the Atlantic type. In general design it is of the ” 251 ” type, having the same dimensions of boiler and wheels as that class. The cylinders are placed in line across the engine, and are of proportions that have given rise to some argument. The high-pressure cylinders are outside, 13-in. in diameter with a stroke of 20-in., with balanced slide valves of the open-backed type placed above them, while the low-pressure cylinders, inside the frames and connected to the leading pair of coupled wheels, are 16-in, in diameter with a stroke of 26-in., and have their valves placed back to back between them.
As can be seen, the outside cylinders are actuated by Walschaerts valve-gear, the low-pressure cylinders being operated by Stephenson link motion. A change valve is fitted over the low-pressure steam chest, worked by a small auxiliary steam cylinder, whereby the low-pressure cylinders can be supplied at will, and for any length of time, with either live steam from the boiler or the exhaust steam from the high-pressure cylinders, thus being worked either as a “simple” or a compound, according to requirements. There are two reversing levers with sectors placed close together on the foot-plate, and the two sets of gear can be operated independently or together, as may be desired.
Mr. Ivatt’s vacuum locking device is fitted to the two reversing shafts, this device having the advantage of locking the gear close up to its work, thereby obviating any slackness in the fittings between the shaft and the foot-plate. Apart from the cylinder arrangement, and the construction of the boiler shell with slightly thicker plates to stand an enhanced working pressure of 200 lb. per sq. in.. No. 292 was practically identical with the “simple” Atlantics of the ” 251 ” class.
The modifications here chronicled, however, increased the total weight of the engine to 69 tons, which were distributed as follows: On bogie wheels 18 tons 10 cwt., on each pair of coupled wheels 18 tons 5 cwt., and on trailing wheels 14 tons.
The tender is of the standard type, carrying 5 tons of coal and 3,670 gallons of water, and provided with Mr. Ivatt’s pick-up apparatus for filling the tank en route. No. 292 bears Doncaster Works No. 1066, and is shown in Fig. 111. In a series of tests made with this engine and No. 294 “simple” Atlantic, already referred to, the advantage was slightly in favour of the compound engine.
Vulcan Compound Locomotive
Almost simultaneously with the advent of No. 292, a further trial of compounding was made on the Great Northern Railway. With the consent of his directors, Mr. Ivatt invited the leading firms of locomotive builders in the country to submit tenders for the building of locomotives of their own design, and an engine designed by the Vulcan Foundry, Ltd., of Newton-le-Willows, was accepted and built. No. 1300, which bears the makers’ No. 2025 and the date 1905, is a four-cylinder compound, approximating in arrangement with the well-known and successful system of M. de Glehn, but with certain specialities of the builders. For example, the engine is provided with the
” Vulcan ” patent starting valve, which admits steam at a reduced pressure to the receiver at starting, the supply being automatically cut off as soon as the steam has reached the low-pressure cylinders.
Another feature is the ” Vulcan ” patent reversing gear, which allows one reversing screw to operate both high and low-pressure valve gear at the same time, giving a variable cut-off for the two sets of motion, which can be adjusted to suit requirements whilst the engine is running. Thus the high-pressure motion can, for instance, be notched up at will without interfering with the cut-off of the low-pressure cylinders, or vice versa. These two devices were fully illustrated and described in The Locomotive Magazine of September 14th, 1907. As can be seen from the accompanying illustration, Fig. 112, this engine differed in external appearance from the general type of G.N.R. designs, though in certain details the practice of the railway was adhered to, notably in the framing and details of the leading bogie and the trailing wheels; and the tender was of the standard G.N.R. pattern, being, in fact, built at Doncaster.
No. 1300 differed from the Doncaster-built compound already described in most of its leading dimension, and notably in the size and proportions of its cylinders, the discrepancy being, of course, all the more noticeable since both engines have the same diameter of coupled wheels, 6-ft. 8-in. No. 1300 has two high-pressure cylinders, 14-in. in diameter with a stroke of 26-in., placed outside the frames and driving direct on the trailing pair of coupled wheels, and actuated by Walschaerts valve gear and piston valves. The low-pressure cylinders are in the usual position below the smoke box, and are 23-in. in diameter with a stroke of 26-in. ; they are also actuated by Walschaerts gear and piston valves. The bogie is of the standard G.N.R. swing-link pattern, with a wheel-base of 6-ft. 3-in., the leading axle being 3-ft. 3-in. in advance of the centre pivot, but it is fitted with wheels only 3-ft. 2-in. in diameter.
The driving wheels are 6-ft. 8-in. in diameter, and the trailing wheels 3-ft. 8-in. The total wheel-base of the engine is 28-ft. 2-in., divided as follows : — Bogie, 6-ft. 3-in. ; trailing bogie wheels to leading coupled wheels, 6-ft. 9-in. ; coupled wheels, centre to centre, 8-ft. 6-in. ; trailing coupled to trailing carrying wheels, 6-ft. 8-in.
The boiler is of ample size; it has a barrel 11 -ft. 11 -in. long with an outside diameter of 5-ft. 1 5/8-in., and is pitched with its centre 8-ft. 10-in, above the rail level. It contains 149 ” Serve ” steel tubes, 12-ft. 4-in. long by 2 3/4-in. in diameter. The outside firebox measures lo-ft. in length, and is of the round-topped pattern, the restriction of the loading gauge preventing the Belpaire firebox originally intended from being adopted. The copper inside firebox measures 9-ft. long, 4-ft. 10 1/2-in. wide at the centre line of the boiler, and 6-ft. 4 1/2-in. and 4-ft. 9-in. high at front and back respectively. The total heating surface is 2,514 sq. ft., of which the firebox contributes 170 sq. ft., and the tubes 2,344 sq. ft. ; the grate area is 31 sq. ft. The boiler carries a working pressure of 200 lb per sq. in.
The engine as originally designed would have weighed 72 tons, but this was subsequently reduced to 71 tons, the distribution of weights being as follows : — On bogie wheels 20 tons 5 cwt., on each pair of coupled wheels 18 tons 10 cwt., and on trailing wheels 13 tons 15 cwt.
The tender is of G.N.R. standard dimensions, with capacities for 3,670 gallons of water and 5 tons of coal respectively, and weighs 40 tons 18 cwt. full. The total wheel-base of engine and tender is 49-ft. 6-in., and the total length over buffers 58-ft. 10 1/2-in. This engine has worked the express services of the Great Northern Railway in conjunction with No. 292 (Doncaster compound) and the ” simple ” Atlantics of the ” 251 ” class without demonstrating any marked superiority in either efficiency or economy of operation, but the introduction of an engine so obtained, and built to the designs of a firm of locomotive builders in place of the Company’s own locomotive engineer, was an experiment deserving of note.
Modifications to 1421
Interposed in the series of large Atlantic type locomotives already referred to, Mr. Ivatt allocated one of the numbers in the ” 1400’s ” to an engine which stood apart from the rest. No. 1421 (Doncaster No. 1166, 1907) was a four-cylinder compound, in general design resembling the earlier compound engine, No. 292, already described and illustrated, but differing in details. For example, whilst the high-pressure cylinders were of the same dimensions, 13-in. by 20-in., the low-pressure had 2-in. greater diameter, 18-in. by 26-in., and they were operated by Walschaerts valve gear instead of the ordinary Stephenson link-motion adopted in the earlier engine. The leading coupled axle was of a built-up, balanced type, patented by Mr. Ivatt.
The boiler was also of a modified pattern, the smokebox being extended backwards instead of in advance of the chimney. Consequently the distance between the tube-plates was reduced from 16-ft, to 14-ft. 6-in., with a proportionate reduction in the heating surface, the total being 2,351.8 sq. ft., of which the firebox contributed 143.6 sq. ft., and the tubes 2,208.2 sq. ft. ; the grate area was 31 sq. ft.
Otherwise the engine, which is illustrated by Fig. 114, was practically identical with No. 292, and in general dimensions with the ” 251 ” class. No. 142 1 weighed in working order 69 tons 2 cwt., distributed as follows : — On bogie wheels 18 tons 2 cwt., on each pair of coupled wheels 18 tons, and on trailing wheels 15 tons. It was provided with the standard tender, fitted with Mr. Ivatt’s patent water pick-up apparatus.
It may be interesting to note in this place that engine No. 265, 7-ft. 8-in. bogie single, was fitted with Mr. Ivatt’s patent flexible balanced crank axle, and Joy’s valve gear in place of the Stephenson link motion, in 1910, and that No. 866, a Stirling four-coupled passenger engine, has also been rebuilt with another form of balanced crank axle of Mr. Ivatt’s design.