The London, Midland and Scottish Railway (LMS) Coronation Class is a class of express passenger steam locomotives designed by William Stanier. They were an enlarged and improved version of his previous design, the LMS Princess Royal Class, and on test were some of the most powerful steam locomotives ever used in Britain at 2,511 dbhp. The locomotives were specifically designed for power as it was intended to use them on express services between London Euston and Glasgow Central; their duties were to include the hauling of a proposed non-stop express, subsequently named the Coronation Scot.
The first ten locomotives of the Coronation class were built in a streamlined form in 1937 by the addition of a steel streamlined casing. Five of these ten were specifically set aside to pull the Coronation Scot. Although a later batch of five unstreamlined locomotives was produced in 1938, most of the ensuing Coronation class were outshopped as streamliners. From 1944 until production ended in 1948, all-new engines were built in unstreamlined form and all the streamliners had their casings removed. The last of the 38 locomotives was completed in 1948.
The Coronation class was probably painted in more styles of livery than any other engine class; seven in the LMS era up to 1947 and five more during the British Railways era from 1948 onwards. That does not mean that all 38 locomotives were painted in all these different styles; many were specific to just a few engines. The only style that all 38 bore was the British Railways lined Locomotive Green and the entire class was turned out thus between 1955 and 1958.
It was customary on all British mainline journeys to change engines at convenient locations to avoid the lengthy process of re-coaling. The Coronation locomotives were therefore strategically stationed at key points between London and Glasgow and they would be assigned to the shed at that location. The chosen locations were at London (Camden shed), Crewe (Crewe North), Carlisle (Upperby) and Glasgow (Polmadie). It was only in the latter days of steam that the mix of shed assignments became more fluid.
No. 6220 Coronation held the British steam speed record between 1937 and 1938, . It held that record until beaten by 4468 Mallard in 1938. Secondly, No. 6234 Duchess of Abercorn holds the record to this day for the greatest British power output to be officially recorded on an attached dynamometer car, achieved in 1939. The Coronation class was represented at the 1948 British Railways locomotive exchange trials, designed to compare the performances of similar locomotives from the four pre-nationalised companies, but they performed extremely poorly. After this, they were targeted for low coal consumption instead of extreme pulling power . One of the class was involved in the Harrow and Wealdstone rail crash precipitated by 46242 City of Glasgow. This was the second worst rail crash in British history, the death toll being 112.
After a successful decade of operations in the 1950s, the 1955 Modernisation Plan's increased use of diesel locomotives made many of the class redundant, and the electrification of the main line between London Euston and Crewe resulted in their removal from this important section of the main line as, at the time, it was thought that there was insufficient clearance between the locomotives and the overhead wires. (The locomotives have subsequently run 'under the wires' in perfect safety in preservation.) With no suitable work available, the survivors were scrapped from late 1962 to late 1964. Three locomotives were saved for preservation, with one of them ending up in the National Collection. As at October 2016, two are static in museums whilst the third is certified for main line service.
Design history
Although the prior introduction of the Princess Royal class had provided the London Midland and Scottish Railway (LMS) with more powerful locomotives to be used on the main line between London Euston and Glasgow Central, the board of directors were persuaded in 1936 that more such locomotives would be needed, particularly as they were being asked to approve the introduction of a new non-stop service between those cities, designated the Coronation Scot. Initially, the Chief Mechanical Engineer, William Stanier, planned to build five more Princess Royals, but the Chief Technical Assistant and Chief Draughtsman at the LMS Derby Works, Tom Coleman, argued that it would be preferable to design a new class of locomotive that was more powerful, more reliable and easier to maintain. Stanier was convinced and the drawing office commenced designing the new class. When Stanier was called on to perform an assignment in India, Coleman became responsible for most of the detailed design in his absence.
Compared to the Princess Royal Class, there were important differences which would lead to an improved performance. Increased power was obtained by adopting a bigger boiler with greater steam-raising capacity; this included a firebox heating surface of versus 217 sq ft, a flue heating surface of versus 2,299 sq ft, superheater surface area of (some sources say 822 sq ft) versus 598 sq ft and a grate area of versus 45 sq ft. Also, the steam passages were better streamlined for greater efficiency and, most importantly, the piston valves went up in size from 8 inches to 9.5 inches. In order to allow higher speeds, the diameter of the driving wheels was increased to (from 6 ft 6 in) and the cylinder diameters were increased by . The outside cylinders were moved forward with rocking shafts operating the inside cylinders. Finally a coal pusher was incorporated into the tender so the fireman did not have to "bring the coal forward", significantly cutting his workload which was particularly important on the long runs from Euston to Glasgow.
Just as the new design was approaching finalisation, the LMS marketing department created a difficult problem. The London and North Eastern Railway (LNER) had recently introduced its streamlined Class A4 locomotive which had captured the imagination of the public, and the marketing department persuaded the board that the LMS's new locomotives should be streamlined too. This was problematic in that the new design was so large that it only just conformed to the maximum loading gauge for the main line; moreover, it was sufficiently heavy that it was close to the Civil Engineer's maximum weight limit. Nevertheless, Coleman managed to design a streamlined steel casing that hugged the locomotive so tightly that it could still meet the loading gauge. The casing weighed some , but Coleman managed to save an equivalent weight in the locomotive itself.
The casing was tested in a wind tunnel, and retained after it was found to be as good as other forms of streamlining. After introduction it was subsequently found that its aerodynamic form failed to disturb the air sufficiently to lift the exhaust from the chimney, thus obstructing the driver's vision with smoke.
Construction history
Locomotives The first five locomotives, Nos. 6220–6224, were built in 1937 at the LMS Crewe Works at an average cost of £11,641 each. They were all intended to haul the Coronation Scot, so the locomotives and the special trainsets bore a common livery. The locomotives were streamlined and painted Caledonian Railway blue with silver horizontal lines along each side of the locomotive. The special trainsets that they hauled were painted the same shade of blue and the silver lining was repeated along each side of the coaches.
In 1938 the second five locomotives of the class, Nos. 6225–6229 (named after Duchesses) were also built in streamlined form at an average cost of £11,323 each. They were painted in the same shade of crimson lake which had already been applied to the Princess Royal class; the same style of horizontal lining that had been a feature of the first five locomotives was continued, but in gilt. Although the crimson lake matched the standard LMS rolling stock, there was no attempt to apply the gilt lining along the sides of these coaches. A prototype trainset was built with such lining for exhibition in America, but it was never put into service due to the outbreak of the Second World War.
Stanier, the designer of the locomotives, felt that the added weight and difficulty in maintenance due to the streamlining was too high a price to pay for the actual benefits gained at high speed. Therefore, in 1938 a third batch of five locomotives (again named after Duchesses) was built, Nos. 6230–6234, without streamlining at an average cost of £10,659 each.
During 1939 and 1940, a fourth batch of ten locomotives (Nos. 6235–6244) was built in streamlined form commencing with No. 6235 City of Birmingham. The names of cities for the locomotives would seem to have been adopted because the LMS was fast running out of names of Duchesses. These locomotives cost an average of £10,659 for the first five and £10,838 each for the second five. The names of the cities in this batch were in strict alphabetical order. This came to an end when No. 6244 City of Leeds was patriotically renamed King George VI in 1941.
The fifth batch, again named after cities, comprised four locomotives, Nos. 6245–6248. These engines were built during 1943 and the average cost was held to £10,908 due to the incorporation of recycled boilers. During the Second World War, the Materials Committee of the government tried to balance the needs for steel between civilian departments and the War Department when allocating those resources. Despite these constraints, the entire batch was still outshopped in streamlined form.
The theme of cities continued into 1944 when another batch of four, Nos. 6249–6252, was built without streamlining. The cost of these locomotives averaged £11,664 each. A follow-up batch of three locomotives (Nos. 6253–6255) was built in 1946 and this batch attracted an inflationary average cost of £15,460 each. The problem of hanging smoke was addressed and smoke deflectors were now incorporated into the design.
The final two locomotives were constructed to the modified design of George Ivatt who succeeded both Stanier, following his retirement, and Stanier's immediate successor Charles Fairburn, who unexpectedly died in office. The first, No. 6256 built in 1947, was the last of the class to be built before nationalisation and it was therefore named in honour of its original designer Sir William A. Stanier, F.R.S.. The unveiling of the nameplate was performed by Stanier himself. In 1948, the privately owned railways were nationalised and incorporated into British Railways. It was within this new regime that No. 46257 was completed – in common with other LMS locomotives, 40000 had been added to the original numbers. The spiralling costs after the Second World War, combined with the design changes, resulted in the individual cost of these locomotives escalating to £21,411.
Tenders
Overview
The original design of tender, which came to be known as Type 'A' was designed for the first ten streamlined locomotives. These were of welded tank construction and included side sheets extending from the rear of the tender, which had the effect of reducing drag from eddies between the tender and the leading coach. 28 of these were constructed to be coupled with all the 24 streamliners (Nos. 6220–6229 and Nos. 6235–6248) as well as four of the unstreamlined locomotives (Nos. 6249–6252). In practice, it would seem that the side sheets made it more difficult to access the water filler as well as the couplings.
A second, more traditional design followed for the initial batch of five unstreamlined locomotives (Nos. 6230–6234). Again they were of welded tank construction, but lacked any of the streamlining add-ons. Even without the streamlining Type 'B' tenders were distinguishable from Type 'A' by having a slightly different profile at the front and steps and handrails at the rear.