LMS Coronation Class

LMS Coronation Class
No. 6229 Duchess of Hamilton
Type and origin Power type Steam Designer William Stanier Builder LMS Crewe Works Build date 1937–1948 Total produced 38
Specifications Configuration: ​  • Whyte 4-6-2  • UIC 2′C1′ h4 Gauge 4 ft 8+1⁄2 in (1,435 mm) Leading dia. 3 ft 0 in (0.914 m) Driver dia. 6 ft 9 in (2.057 m) Trailing dia. 3 ft 9 in (1.143 m) Minimum curve 6 chains (120 m) normal 4+1⁄2 chains (91 m) dead slow Wheelbase 62 ft 11 in (19.177 m) ​  • Engine 37 ft 0 in (11.278 m)  • Drivers 14 ft 6 in (4.420 m)  • Tender 15 ft 0 in (4.57 m) Length Streamlined: 73 ft 9+3⁄4 in (22.498 m) Conventional: 73 ft 10+1⁄4 in (22.511 m) Height 13 ft 3 in (4.039 m) Loco weight Streamlined: 108.1 long tons (121 short tons; 110 t) Conventional: 105.25 long tons (117.88 short tons; 106.94 t) 6256/6257: 108.5 long tons (122 short tons; 110 t) Tender weight 6220–6255: 56.35 long tons (63.11 short tons; 57.25 t) 6256/6257: 56.50 long tons (63.28 short tons; 57.41 t) Fuel type Coal Fuel capacity 10 long tons (11.2 short tons; 10.2 t) Water cap. 4,000 imp gal (18,000 L; 4,800 US gal) Firebox: ​  • Type    • Grate area 50 sq ft (4.6 m2) Boiler: ​  • Model LMS type 1X  • Tube plates 19 ft 3 in (5.867 m)  • Small tubes 2+3⁄8 in (60 mm), 129 off  • Large tubes 5+1⁄8 in (130 mm), 40 off Boiler pressure 250 psi (1.72 MPa) Heating surface: ​  • Firebox 230 sq ft (21 m2)  • Tubes and flues 2,577 sq ft (239.4 m2)  • Total surface 2,807 sq ft (260.8 m2) Superheater: ​  • Heating area 6220–6255: 822 sq ft (76.4 m2) 6256/6257: 856 sq ft (79.5 m2) Cylinders 4 Cylinder size 16+1⁄2 in × 28 in (419 mm × 711 mm) Valve gear Walschaerts for outside cylinders with rocking shafts for inside cylinders Valve type Piston valves
Performance figures Tractive effort 40,000 lbf (180 kN)
Career Operators London, Midland and Scottish Railway British Railways Power class LMS: 7P BR: 8P Numbers LMS: 6220–6256 BR: 46220–46257 Locale West Coast Main Line Withdrawn 1962–1964 Preserved 6229, 6233, 6235 Disposition Three preserved, remainder scrapped

The London, Midland and Scottish Railway (LMS) Coronation Class^[a] 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.^{[1]: 86–87} 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, 114 miles per hour (183 km/h).^[2][3] 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.^[4] 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 ^{[clarification needed]}. 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.^[5]

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 there was insufficient clearance between the locomotives and the overhead wires. 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.

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