Power type Steam Builder GWR / BR Swindon Works Total produced 171 | Designer Charles Collett Build date 1923–1950 Configuration 4-6-0 | |
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The 4073 Class or Castle class were 4-6-0 steam locomotives of the Great Western Railway design built between 1923 and 1950. They were designed by the railway's Chief Mechanical Engineer, Charles Collett, for working the company's express passenger trains.
Contents
Background
The origins of this highly successful design date back to the Star Class of 1907 which introduced the basic 4-cylinder 4-6-0 layout with long-travel valves and Belpaire firebox that was to become synonymous with GWR express passenger locomotives. The Star class were designed to take the top express trains on the GWR with 61 in service by 1914, but after World War 1 there was a need for an improved design. To meet this need Chief Mechanical Engineer GJ Churchward had in mind an enlarged Star class design with a standard No.7 boiler, as fitted to his GWR 4700 Class express freight 2-8-0 design. However, this combination would have taken the axle load of such a design over the 20 ton limit then set by the civil engineers, and in the end nothing came of the idea.
Design
C. B. Collett succeeded Churchward as Chief Mechanical Engineer of the GWR in 1922 and immediately set about meeting the needs for a new locomotive design that would both supplement the Stars and replace them on the heaviest expresses. Collett's solution was to take the basic layout of the Star with an extended frame and add a newly designed No.8 boiler which was both larger and lighter. The increased amount of steam that this produced allowing an increase in the cylinder diameter from 15 in × 26 in (381 mm × 660 mm) to 16 in × 26 in (406 mm × 660 mm). The extended frame allowed for a side window cab and an increased grate area. The result was an increase in tractive effort to 31,625 lb, and a locomotive that looked attractive and well proportioned while remaining within the 20 ton axle limit.
Production
Unlike the Star class, there was no prototype. Collett was sufficiently confident of the design to place an order with Swindon railway works (Lot 224) for ten locomotives in 1923 although there was a four-month delay between the appearance of the first example, in August 1923 and the second in the December to allow for the correction of any teething problems. Thereafter the remaining eight locomotives came out at regular intervals until April 1924. They were 4073-4082; the number series continuing unbroken from the Star class. The last 12 Star class locomotives, which were built in 1922-23, had been given names of Abbeys in the western area served by the GWR. The new locomotives were named after castles also in the west beginning with 'Caerphilly Castle'. Over the twenty-seven years from August 1923 to August 1950 155 Castles were built new at Swindon Works and a further sixteen were converted from other classes. In February 1952, two engines, 4082 Windsor Castle and 7013 Bristol Castle swapped names and numbers with each other because King George VI died. 7013 was disguised as 4082 to run the funeral train and the two engines never swapped back. 4082 was withdrawn from service in 1964 as 7013 and 7013 was withdrawn from service as 4082 in 1965.
New builds
All the new builds were as follows.
Great Western Railway
British Railways (Western Region)
These locomotives were built with minimal changes to the dimensions. However, from 5013 Abergavenny Castle there was an alteration to the shape of the front-end casing over the inside cylinders, and from 5043 Earl of Mount Edgcumbe a shorter chimney was fitted. Those built before 1926 were fitted with a standard 3,500 imp gal (16,000 l; 4,200 US gal) tender but thereafter 4,000 imp gal (18,000 l; 4,800 US gal) became standard for the class.
Rebuilds
Between January and September 1924 the only Great Western 4-6-2, No.111 The Great Bear, was officially rebuilt into a member of the Castle Class, although only the 'front portion of the original frames and the number plates were used again but probably little else'. The new locomotive was renamed Viscount Churchill and survived until withdrawal in July 1953.
In April 1925 Star class No. 4009 Shooting Star was likewise rebuilt as a Castle by extending the frames and fitting a new Castle Class boiler and cab. It was renumbered and renamed, 100 A1 Lloyds and was withdrawn in 1950.
In October 1925 a second Star class, No. 4016 The Somerset Light Infantry (Prince Albert's), was similarly converted to a Castle although in this case it retained its name and number. Two further conversions of Stars were undertaken in 1926; Nos. 4032 Queen Alexandra and 4037 The South Wales Borderers retaining their names and numbers and surviving until 1951 and 1962 respectively.
Between 1937 and 1940 a further twelve members of the 'Abbey series' of the Star class (Nos. 4061-72) were rebuilt as Castles, They were allocated new numbers 5083 to 5092 but retained their original names and were withdrawn between 1958 and 1964.
Publicity and Trials
When introduced they were heralded as Britain’s most powerful express passenger locomotive, being some 10% more powerful than the Stars. The first, No. 4073 Caerphilly Castle, made its debut at Paddington station on 23 August 1923. The choice of 4082 as Windsor Castle proved fortuitous as this locomotive was used to haul the royal train when King George V and Queen Mary visited Swindon Works in 1924, and much publicity was gained when the king was permitted to drive the engine back from the works to the station before the return journey, with the Queen and several high-ranking GWR officers also on the footplate.
During 1924 4073 Caerphilly Castle was exhibited at the British Empire Exhibition at Wembley, alongside Sir Nigel Gresley’s Flying Scotsman. The Great Western declared their engine to be more powerful than its bigger LNER rival, and in terms of tractive effort alone they were entitled to do so. As a result of this GWR General Manager Sir Felix Pole proposed to LNER Southern Area General Manager Alexander Wilson that a trial of the two types should take place via an exchange arrangement. The resulting trials commenced in April 1925 with 4079 Pendennis Castle representing the GWR on the Great Northern main line and 4474 Victor Wild representing the LNER on Great Western tracks. On the first morning Pendennis Castle was to work a 480-ton train from King's Cross to Doncaster, and LNER officials fully expected the smaller, lighter engine to encounter problems climbing Holloway Bank. However railway writer Cecil J. Allen records that the GWR locomotive made a faster start from King's Cross to Finsbury Park than any LNER pacific he had recorded up to that time and over the trial Pendennis Castle kept well within the scheduled time and used less coal, considerably denting LNER pride. For the LNER Victor Wild was compared on the Cornish Riviera Express to 4074 Caldicot Castle and although it kept to time the longer wheelbase of the pacific proved unsuited to the many curves on the Route. Again the GWR took the honours with Caldicot Castle burning less fuel and always ahead of time, this being illustrated on the last 2 days of the trial by gaining 15 minutes on the schedule in both directions.
In 1926, number 5000 Launceston Castle was loaned to the London, Midland and Scottish Railway where it ran trials between London and Carlisle. The locomotive fulfilled the LMS requirements so well that the latter first requested the GWR to build a batch of Castles for use on the West Coast Main Line, and, failing that, a full set of construction drawings. Both proposals were rejected by the GWR Board of Directors. The LMS eventually succeeded in gaining access to the design by recruiting William Stanier, the GWR's Works Manager at their main Swindon railway works to become the new Chief Mechanical Engineer for the LMS.
Performance
The Castles handled all but the heaviest loads, these being entrusted to the 30-strong King Class, themselves a development of the Castles with an even larger boiler and smaller wheels (6'6" diameter) for both increased tractive effort and to allow for loading gauge clearance.
The Castle class was noted for superb performance overall, and notably on the Cheltenham Flyer during the 1930s: for example, on 6 June 1932 the train, pulled by 5006 Tregenna Castle, covered the 77.25 miles from Swindon to Paddington at an average speed of 81.68 mph start-to-stop (124.3 km at an average speed of 131.4 km/h). This world record for steam traction was widely regarded as an astonishing feat.
Subsequent modification
In 1946 Frederick Hawksworth, Collett’s successor, introduced a higher degree of superheat to the Castle boiler with resulting increased economy in water consumption. From 1956 the fitting of double chimneys to selected engines, combined with larger superheaters, further enhanced their capacity for sustained high-speed performance. The fastest recorded was hauled by 7018 Drysllwyn Castle in April 1958 taking 93 minutes 50 seconds with a top speed of 102 mph (164 km/h) at Little Somerford.
Accidents and incidents
Withdrawal
Withdrawal started in the 1950s, with the first 100 A1 Lloyds withdrawn from Old Oak Common in March 1950. The first "new build" Castle, number 4091 Dudley Castle was withdrawn from Old Oak Common, nearly 9 years later in January 1959.
The lowest mileage of a Castle was the 580,346 miles run by 7035 Ogmore Castle between August 1950 and June 1964, the highest mileage of any Castle class was run by 4080 Powderham Castle which totalled 1,974,461 miles in 40 years and 5 months.
The last three castles to be withdrawn were all allocated to Gloucester shed, with 5042 Winchester Castle and 7022 Hereford Castle withdrawn in June 1965. The last to be withdrawn was Clun Castle in December 1965, which worked the last steam train out of Paddington on 27 November 1965.
List of locomotives
See List of GWR 4073 Class locomotives
Preservation
On 4 March 1967, Nos. 7029 Clun Castle and 4079 Pendennis Castle hauled specials from Banbury and Oxford respectively to Chester, to mark the end of through trains between Paddington and Birkenhead. These two, and six other Castles survive in preservation.
Of the eight Castles to be preserved, six have operated in preservation and all have been out on the main line: nos. 4079 Pendennis Castle, 5029 Nunney Castle, 5043 Earl of Mount Edgcumbe, 5051 Earl Bathurst, 5080 Defiant and 7029 Clun Castle. No. 4073 Caerphilly Castle was given directly to the National Collection upon withdrawal and hasn't run since being preserved and can currently be found at Steam, Museum of the Great Western Railway in Swindon. No. 7027 Thornbury Castle is currently in ex-Barry Scrapyard condition and is undergoing restoration. In July 2016 it was sold from Pete Waterman to a new owner and will be restored to full Main line standard.
4079 did a small number of railtours on the mainline in its early preservation years before departing for Australia in 1973 it was a popular engine on the mainline in both countries and also double headed with 4472 Flying Scotsman during its visit to Australia for the Aus Steam 88 celebrations. it was returned to the UK in 1999 and is currently undergoing restoration at the Didcot Railway Centre.
As of 2016, only 5043 has a valid main line certificate. 4079 has been undergoing restoration since returning from Australia while 5029 and 7029 are both undergoing main line standard overhauls, all three engines are being done to mainline standards and 7027 is being restored from scrapyard condition for main line use. 7029 is due to return to main line traffic in 2017.
There is now a Haynes Owner's Workshop Manual available.
Models
Hornby Railways currently manufacture a model of the 4073 in OO gauge. The Hornby Dublo brand, then owned by Meccano Ltd, also built "Bristol Castle" (released 1957) for their three-rail system and "Cardiff Castle" for the two-rail system two years later; Wrenn continued the Hornby Dublo model when they took over the range. Airfix/GMR (and later Dapol) also produced an OO model; Tri-ang released a TT gauge model; and Graham Farish (later Bachmann) released N gauge models. Many different prototype examples have been depicted by the various manufacturers.