The Evolution of the 4-6-0 Introduced for Fast Goods Traffic, to a Standard Express Passenger Locomotive
LOCOMOTIVES - 38
GREAT WESTERN TEN-WHEELER FOR HEAVY GOODS TRAFFIC, 1899. This type of 4-6-0 was a modification of an experimental locomotive of 1896. The driving wheels were of 55½ inches diameter in both types, but the cylinders of the newer engine were 19 by 28 inches, as against 20 by 24 inches, and a working pressure of 180 lb per square inch, as against 165 lb. in the former. One of its features was the sandbox straddled over the boiler.
WHEN the six-wheels-coupled locomotive, introduced by Robert Stephenson and Company in 1826, essentially for the handling of goods trains upon the British railways had conclusively demonstrated its suitability for this particular phase of traffic, it settled down to persistent development. This tendency, perhaps, became most pronounced during the early ‘forties, when the call for more powerful engines became so manifest for the movement of merchandise, not only throughout the British Isles, but in other countries as well. For many years it was unreservedly accepted as the standard motive power for this duty, since it was found to fulfil very effectively the conditions which generally ruled.
Unswerving adherence to the type and the success recorded therewith induced attempts to be made to reproduce the British triumph in the United States, but they proved to be dismal failures. They could not negotiate the sharp curves safely at any speed. In this instance the introduction of the front bogie truck did not help matters, as had been anticipated, and so the idea of introducing six-coupled drivers upon the American railways was regarded as hopeless, unless the roads were rebuilt, or the design of the six-wheel system underwent a startling change, allowing the coupled drivers to accommodate themselves to a curve. Curious to relate, however, an eight-wheeler of broadly similar design was built for the Baltimore and Ohio Railroad by Ross Winans for freight haulage - “mud-diggers” they were called.
At that time the fortunes of the persevering locomotive builder, Matthias Baldwin, were at a very low ebb, and his prospects were as black as could be conceived. His business had declined almost to vanishing point, and he was weighed down with heavy financial embarrassments which threatened to crush him. Only by the attainment of the seemingly incredible could he hope to obtain commercial rehabilitation. The apparently impossible was achieved. This was his conception of the six-wheels-coupled locomotive with the four front drivers combined in a flexible truck. This idea burst upon him suddenly, to be promptly translated into practice, proved, and introduced to the world, to achieve instant success.
The first engine built in accordance with this principle was completed in December, 1842. The designer apparently was content to follow British precedent once more, and to rely upon his flexible beam-truck to solve the curve-rounding problem, because he did not incorporate the front bogie. Moreover, as in Britain, these locomotives were built for freight traffic, and as the whole of the weight was available for adhesion, they proved highly efficient.
AMERICAN TYPE OF TEN-WHEELER BUILT FOR THE CANADIAN PACIFIC RAILWAY, 1903. Twenty engines of this type were delivered by the North British Locomotive Company. They had cylinders 22 or 26 inches in diameter by 33 inches stroke, and 63-inch drivers.
This success was so gratifying to Baldwin that he continued to emulate British practice by building locomotives with eight coupled wheels, the 0-8-0 type, in accordance with his principle. Rival manufacturers, perturbed by the volume of business flowing to the Baldwin shops, strove to compete, but were handicapped by the Baldwin patent. This led to the design, conceived by Septimus Norris in 1846, for an engine which combined the six-coupled-wheels with a leading four-wheeled bogie, giving the arrangement 4-6-0, and which was duly patented.
The first engine built in accordance with these principles, and in such a way as to render practically the whole weight of the engine available for adhesion, was submitted to trial in 1847, but did not prove a complete success. The truck, especially when entering or leaving a curve, refused to keep to the track, owing to the fact that it carried little or no weight. But the wheel arrangement made powerful appeal to American railway engineers; it incorporated their popular leading bogie, and so they were not dismayed by the relative failure of the first Norris ten-wheeled engine. One railroad, the Erie, took the type in hand and, by a certain skilful distribution of the weight, brought a greater proportion of the load upon the front truck. Thus a failure was converted into a success.
Within a very short time the “ten-wheeler” became such a powerful competitor to the 0-6-0 type that Baldwin was compelled to abandon his arrangement and to assume the manufacture of the new design, though much to his regret. The 4-6-0 became the standard for freight haulage in the United States for many years, but the increasing demand for greater power for the movement of the heavier passenger and fast goods trains led to its adaptation to certain phases of this duty, and it became a formidable rival to the “American” class. Eventually it superseded the latter upon many of the leading systems.
The eminently satisfactory performance of the ten-wheeler upon the American railways attracted so much attention in Great Britain as to persuade its experimental introduction. The lead was made by the Highland Railway in 1894 with an engine of this type for goods traffic. This had cylinders 20 inches in diameter by 26 inches stroke, working at 175 lb per square inch, and driving wheels 63 inches in diameter. The boiler, 14 feet 1⅜ inches in length by 57 inches in diameter, carried 211 tubes, 2 inches in diameter, giving a heating surface of 1,559 square feet; while the fire-box, 93 by 45⅞ inches external diameter, had a heating surface of 113·5 square feet, bringing the total heating surface to 1,672·5 square feet; the grate area was 22·6 square feet. Total weight imposed upon the six-coupled-wheels for adhesion was 94,080 lb.
TEN-WHEELER FOR HEAVY GOODS TRAFFIC ON THE HIGHLAND RAILWAY, 1894. This Scottish railway pioneered the introduction of the type for goods service. It had cylinders 20 by 26 inches, working at a pressure of 175 lb per square inch. The grate area was 22·6 square feet, and the total heating surface amounted to 1,672·5 square feet.
Two years later, in 1896, the ten-wheeler made its appearance upon the Great Western Railway, when an experimental locomotive of this type, carrying the road number “36”, was designed by William Dean for working the heavy goods traffic. This engine had cylinders 20 by 24 inches, working at a pressure of 165 lb, and driving wheels 55½ inches in diameter. The boiler measured 14 feet in length by 54 inches outside diameter, and was fitted with 150 Serve tubes of 2½ inches diameter, which presented a heating surface of 2,272·5 square feet, while that of the fire-box was 115·8 square feet, giving a total heating surface of 2,388·3 square feet. The grate area was 35 square feet. In this engine the total weight available for adhesion was 105,728 lb.
Three years later, as the result of the experience gained with No. “36”, sent to the scrap-heap in 1905, there came another model in which, while the diameter of the driving wheels was maintained, the cylinders were modified to 19 inches by 28 inches. The length of the boiler was also reduced to 10 feet 6 inches by 4 feet 10 inches diameter, with a heating surface of 1,712·88 square feet which, with that of the firebox, 166·8 square feet, gave a total heating surface of 1,879·68 square feet. The grate area was reduced to 32·19 square feet, but the working pressure of the boiler was raised to 180 lb per square inch. This ten-wheeler performed some five years’ service before it was broken up.
While these two experimental expressions of the 4-6-0 were being put through their paces for the movement of freight, the question of providing more powerful locomotives for the handling of the heavy long-distance express passenger trains became somewhat pressing. The “Atlantic” did not meet the situation, inasmuch as the eastern and western divisions of the Great Western system are so violently contrasting in physical characteristics. As the result of careful survey of the whole situation Mr. Dean came to the conclusion that the ten-wheeler offered the greatest promise in this connexion, and so in 1902 commenced the design of a locomotive of this type for such work.
In the year mentioned Mr. Churchward took up the reins of chief mechanical engineer to the Great Western system. He signalized his accession to the responsibility for the provision of motive power by the-introduction of a new series of engines with outside cylinders. As he supported the claims of the ten-wheeler, he initiated his movement with an express passenger engine of this type with a straight boiler barrel and two cylinders. Expectations being realized, six similar engines, but with coned boiler barrels, and named after certain members of the railway directorate, were placed in service in 1905. Two years later another group made their appearance, to be distinguished as the “Lady” class from being named after members of the fair sex famous in history - “Lady Macbeth”, “Lady Godiva”, and so on. This class of ten-wheeler becoming firmly established another group speedily appeared, each locomotive being named after a “Saint”.
In the “Saint” class of ten-wheeler the two-cylinder arrangement was consistently embraced. The cylinders are 18½ inches in diameter by 30-inches stroke, working at 225 lb per square inch, and connected to 80½-inch drivers. The boiler barrel is 14 feet 10 inches in length by 4 feet 10 13/16 inches external diameter. The total heating surface, including superheater, is 2,104 square feet, and the tractive effort 24·395 lb.
In 1909 a new class of ten-wheeler made its appearance, with the distinguishing feature of the four cylinders working simple. These are named after certain kings of England, the leader being christened “King Edward”. Two years later another group came out and, appropriately, were named after the queens of England, the first being “Queen Mary”. As ten-wheelers they perpetuate the “Saint” class, but for purposes of distinction from the two-cylinder series were designated the “Star” class. The four cylinders are 15 by 26 inches, but boiler dimensions, heating surface, diameter of driving wheels and working pressure are identical with their predecessors, though the tractive effort is greater at 27,800 lb.
As succeeding groups of the two- and four-cylinder design were built the class-names underwent subdivision. Thus, the later representatives of the “Saint” class, appearing in 1911, were named after historical residences, as, for instance, “Twine-ham Court”, and so became popularly known as “Courts”. The “Star” class-name was adopted because the first of the express passenger ten-wheelers, from its departure in design, represented as important an event in the locomotive history of the railway as the famous “North Star”, the pioneer engine of the system and broad-gauge days. The first of the series was the third “North Star”, and its companions were named after their predecessors of the broad-gauge era. The subdivisions of this class are known as the “Knights”, “Kings”, “Queens”, “Princes”, “Princesses” and “Abbeys”, from the distinguishing character of their names - “Knight of the Garter”, “King George”, “Queen Alexandra”, “Prince of Wales”, “Princess Mary” and “Westminster Abbey”, as the case may be.
A GREAT WESTERN “ATLANTIC” CONVERTED INTO A TEN-WHEELER. In 1905, the locomotives of the “Lalla Rookh” class were introduced, but failing to give the power required were converted into ten-wheelers two years later. This engine is “North Star” (No. 4000) hauling the “Cornish Riviera Limited”.
In so far as the Great Western Railway is concerned one incident in locomotive development is worthy of record. In common with other British railways the “Atlantic ” was adopted in due course for working the express passenger services, but its reign was relatively short. Upon the main line between London and Cornwall the traffic is dense, and the line is easy so far as Newton Abbot. Thence the grades are heavy and the curves sharper than upon the initial section of the road. This sharp divergence in the physical characteristics was a distinct handicap to the railway which has achieved a world-wide reputation for speed and length of its non-stop runs. Previous to the “Atlantic” invasion of Britain the “American” type had proved adequate for working the normal train between Newton Abbot and London, but it was unequal to the harder going over the westward section. It was anticipated that the “Atlantic” would remove this disability, and so, in 1905, the type made its debut; the engines of the class were named after the famous “Lalla Rookh” group of broad-gauge engines.
Two years later, owing to the urgency to provide greater power for the working of the non-stop Cornish Riviera and Fishguard expresses, an “Atlantic” with four cylinders - the first quadruple cylinder locomotive to be constructed for the system - was produced as an experiment. It did not give the results anticipated, proving itself, in fact, little, if at all, superior to the established “American” type. Consequently it was withdrawn and transformed into a ten-wheeler. As the result of this experience each member of the “Lalla Rookh” group of “Atlantics” was sent in turn to the shops to receive a third driving axle and thus be converted into ten-wheelers. So far as this famous British railway is concerned, the 4-6-0 has completely usurped the “Atlantic”, and the only surviving expressions of the 4-4-2 wheel classification are the de Glehn French com-pound and the “County” tank types.
THE “EXPERIMENT”, THE FIRST TEN-WHEELER BUILT AT CREWE, 1905. This locomotive was notable for having a larger grate area - 25 square feet - than any previous engine constructed for the London and North Western Railway. The cylinders were 19 by 26 inches, working at a pressure of 185 lb per square inch.
The year 1905 recorded the appearance of the first ten-wheeler upon the London and North Western Railway under the significant name “Experiment”. The cylinders were 19 by 26 inches, working at 185 lb of steam pressure per square inch, connected to 72-inch drivers. The heating surface of the tubes was 1908, and of the fire-box, 133 square feet, respectively, giving a total heating surface of 2,041 square feet. The grate area was 25 square feet. The total wheel-base of the engine was 26 feet 8½ inches; of complete locomotive 48 feet 4¼ inches. In service trim the engine and tender weighed 230,160 lb, the former scaling 147,280 lb with 104,720 lb on the six-coupled-wheels. This locomotive was evolved to haul the heavy Scottish expresses over the most exacting sections of the system, and by the end of 1906 fifteen locomotives of this design were in service.
Six years later, in 1911, there appeared a new modified “six-footer” designated the “Prince of Wales” class. In these the cylinders are increased in diameter to 20½ inches, the stroke remaining unaltered, while the diameter of the “Experiment” driving wheels is maintained. The boiler heating surface is 1,439·59 square feet; firebox 133·3 square feet; superheating elements 324·58 square feet, bringing the total heating surface to 1,897·5 square feet. The grate area has not been changed, but the working pressure of the boiler, due to the incorporation of superheating, is reduced to 175 lb per square inch. The wheel-base, weight of the engine and weight available for adhesion are the same as in the first North-Western ten-wheeler, but the total weight of the locomotive, in working order, is increased to 236,320 lb.
LONDON & NORTH-WESTERN TEN-WHEELER, “PRINCE OF WALES”, 1911. This locomotive, the first of the “Prince of Wales” class, was built at Crewe, and represented the second stage of the development of the 4-6-0 type upon the system. In working order it weighs 236,320 lb, with 104,720 lb imposed upon the six 72-inch driving wheels.
On January 24, 1913, there left the Crewe locomotive shops a new and larger ten-wheeler designed for working the Scottish traffic over the northern division of the London and North Western section of the system. This was No. “2222”, named “Sir Gilbert Claughton”, after the chairman of the company, and it represented a distinct advance upon the railway’s locomotive practice. It is a four-cylinder simple, with cylinders 16 by 26 inches set abreast, and fitted with piston-valves above, all driving upon the leading coupled-axle. The boiler, 14 feet 6 inches in length by 5 feet 2 inches diameter, has a heating surface of 1,745·4 square feet which, with the 413·6 square feet of the superheater elements, brings the total heating surface to 2,159 square feet. The fire-box, of the Belpaire type, was the first to be adopted in new construction by the system; while it was also the pioneer locomotive of the railway to be equipped with Walschaert valve-gear. The grate area, 30·5 square feet, exceeded all previous North Western standards. The working pressure of the boiler is the same as in the “Prince of Wales” class, namely, 175 lb per square inch. The driving wheels were increased to 78 inches in diameter; the wheelbase of the engine extended to 29 feet, and 54 feet for engine and tender. Ready for the road, with the tender charged with 3,000 gallons of water and 13,440 lb of coal, the locomotive weighs 262,080 lb; of this amount the engine accounts for 174,160 lb, with 132,160 lb distributed over the six-coupled-wheels for adhesion.
LONDON & NORTH WESTERN TEN-WHEELER, “SIR GILBERT CLAUGHTON”, 1913. This powerful locomotive represents the third development of the type built at Crewe. Ready for the road the locomotive weighs 262,080 lb.
The development of the “ten-wheeler” in Britain was advanced a further decisive step during 1923 by the Great Western Railway with a larger and more powerful exponent of its 4-6-0 four-cylinder type for the working of its long-distance express passenger traffic. The group is known as the “Castle” class from the engines being named after historic noble residences distributed throughout the territory served by the railway; the first of the series, numbered consecutively from 4,073 to 4,082, is the “Caerphilly Castle”.
The debut of this locomotive created a sensation because it was the most powerful engine in the country for passenger duty. In this respect it excels the most recent “Pacifics” introduced upon the London and North Eastern Railway for the movement of its express Scottish traffic, and represents another development in the old-time friendly rivalry between these two roads for pre-eminence in power and speed.
The “Caerphilly Castle” has four cylinders 16 by 26 inches, working at a pressure of 225 lb per square inch. The cylinders exceed in dimensions those previously used upon the system, and a new boiler had to be designed to provide the requisite steam. The Great Western Railway has embraced the locomotive boiler in its policy of standardization, and the problem was to retain the special features in the new design. The standardized length of 14 feet 10 inches is maintained, but the diameter of the boiler barrel is increased to 69 inches at the throat-plate, tapering to 61 15/16 inches at the front end.
The fire-box, likewise complying with standard requirements, has a grate area of 30·28 square feet. The boiler carries 215 fire-tubes, 15 feet 2 7/16 inches in length; of this number 201 have a diameter of 2 inches, while that of the outstanding 14 tubes is 5⅛ inches. The superheater comprises 84 tubes, 15 feet 3⅜ inches in length by 1 inch in diameter. The total heating surface is 2,312 square feet - fire-tubes, 1,885·62, superheater tubes 262·62, and fire-box 163·76 square feet, respectively. The four cylinders are set in line, the two inside the frame drawing their steam through passages in the saddle supporting the smoke-box, while that for the outside cylinders is led through steam-pipes carried through the sides of the smoke-box and connected direct to the steam-chests.
The driving wheels are 80½ inches in diameter; the bogie wheels 38 inches. The six-wheeled tender has capacity for 3,500 gallons of water. The overall length of the locomotive is 65 feet 1¾ inches; total wheelbase of engine 27 feet 3 inches. Ready for the road the complete locomotive scales 268,464 lb (119-85 tons); of this amount the tender accounts for 89,600 lb, and the engine 178,864 lb, with 131,824 lb imposed upon the six-coupled-wheels for adhesion. At 85 per cent, boiler pressure the tractive effort is 31,625 lb - 1,707 lb in excess of that of the largest three-cylinder 4-6-2 engines upon the London and North Eastern Railway and which previously ranked as the most powerful express passenger locomotives in Britain.
THE “CAERPHILLY CASTLE”, THE MOST POWERFUL EXPRESS PASSENGER LOCOMOTIVE IN GREAT BRITAIN, 1923. This engine represents the hghest development of the ten-wheeler. It has 80½ inch drivers and, ready for the road, it scales 268,464 lb; it has a draw-bar pull of 31,626 lb - 1,707 lb more than that of the next most powerful locomotive in the country.
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