GWR 4700 Class

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GWR 4700 Class
4705 at the Southall Locomotive Depot, in 1962
Type and origin Power type Steam Designer George Jackson Churchward Builder GWR Swindon Works Order number Lots 214, 221 Serial number 4700: 2866, 4701–4708: none Build date 1919 (1), 1922–1923 (8) Total produced 9
Specifications Configuration: ​  • Whyte 2-8-0  • UIC 1'D h2 Gauge 4 ft 8+1⁄2 in (1,435 mm) standard gauge Leading dia. 3 ft 2 in (0.965 m) Driver dia. 5 ft 8 in (1.727 m) Minimum curve 8 chains (530 ft; 160 m) normal, 7 chains (460 ft; 140 m) slow Length 66 ft 4+1⁄4 in (20.22 m) Width 8 ft 11 in (2.718 m) Height 13 ft 4+3⁄4 in (4.083 m) Axle load 19 long tons 12 cwt (43,900 lb or 19.9 t) 19 long tons 12 hundredweight (19.9 t; 22.0 short tons) full Adhesive weight 73 long tons 8 cwt (164,400 lb or 74.6 t) 73 long tons 8 hundredweight (74.6 t; 82.2 short tons) full Loco weight 82 long tons 0 cwt (183,700 lb or 83.3 t) 82 long tons 0 hundredweight (83.3 t; 91.8 short tons) full Tender weight 46 long tons 14 cwt (104,600 lb or 47.4 t) 45 long tons 14 hundredweight (46.4 t; 51.2 short tons) full Fuel type Coal Water cap. 3,500 or 4,000 imperial gallons (16,000 or 18,000 L; 4,200 or 4,800 US gal) Firebox: ​  • Grate area 30.28 sq ft (2.813 m2) Boiler GWR Standard No. 7[1] Boiler pressure 225 lbf/in2 (1.55 MPa) Heating surface: ​  • Firebox 169.75 sq ft (15.770 m2)  • Tubes 2,062.35 sq ft (191.599 m2) Superheater: ​  • Type 4-element or 6-element  • Heating area 4-element: 211.20 sq ft (19.621 m2), 6-element: 276.98 sq ft (25.732 m2) Cylinders Two, outside Cylinder size 19 in × 30 in (483 mm × 762 mm) Valve gear Stephenson Valve type Piston valves
Performance figures Tractive effort 30,460 lbf (135.5 kN)
Career Operators GWR » BR Class 4700 Power class GWR: D, BR: 7F Numbers 4700–4708 Nicknames Night Owls Axle load class GWR: Red Withdrawn 1962–1964 Disposition All original locomotives scrapped; one new-build under construction

The Great Western Railway (GWR) 4700 Class was a class of nine 2-8-0 steam locomotives, designed by George Jackson Churchward. They were introduced in 1919 for heavy mixed-traffic work. Although primarily designed for fast freight, the class also sometimes hauled passenger trains, notably heavy holiday expresses in the summer months. They were unofficially nicknamed "Night Owls" because they were primarily designed to haul goods during the night and they could be seen simmering in the daylight, awaiting their nocturnal duties.^[2][3][4]

At the end of the First World War, the running department of the GWR identified the need for a larger version of the successful GWR 4300 Class 2-6-0 incorporating the Swindon No. 1 boiler. They envisaged a smaller version of the successful Saint class 4-6-0 with 5 ft 8 in (1.727 m) driving wheels - the intermediate of Churchward's three standard wheel sizes, for express goods trains. However, Churchward preferred a 2-8-0 design for this purpose.^[5]

The prototype of the new class was built at Swindon Works in May 1919 (Lot 214) and was the last design by Churchward. It was numbered 4700. According to the RCTS monograph, the design was not successful as built because the No. 1 boiler proved to be inadequate for such a large engine.^[6] In May 1921, it was therefore rebuilt with a newly designed and larger Swindon No. 7 boiler. However, according to Cook it was built with a Standard No. 1 boiler as the intended design of the larger Standard No. 7 boiler, which was not yet ready.^{[7][page needed]}

Eight further locomotives with the larger No. 7 boilers and detail differences were ordered by Churchward in 1921 (Lot 221), but these only appeared after his retirement. These were numbered 4701 to 4708. Although they were mechanically successful locomotives, their large size severely restricted their route availability and so no more examples were built. Churchward's successor Charles Collett later rebuilt a Saint Class with 6 ft 0 in (1.829 m) wheels to form the Hall Class which was a far more versatile mixed traffic locomotive.^[8] Later, Collett would produce the Grange Class which was exactly as the traffic department had originally envisaged: a 4-6-0 with Standard No. 1 boiler and 5 ft 8 in driving wheels. The class was originally fitted with 3,500 imperial gallons (16,000 L; 4,200 US gal) tenders but during 1933/4 these were replaced by 4,000 imperial gallons (18,000 L; 4,800 US gal) tenders.^{[citation needed]}

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The class were primarily used on fast overnight freight services on the London, Exeter and Plymouth, London–Bristol and London, Birmingham and Wolverhampton routes.

From 1957 onwards, several members of the class were often used on heavy Saturday relief passenger services to the West of England during the summer months, where they gained the Brunswick Green livery. Previously they were either lined or unlined black.

Despite their limited use, the Night Owls were exceptional mixed traffic locomotives which proved their worth on the heavier express freight and passenger services.

• On 12 November 1958, locomotive No. 4707 was hauling a freight train when it overran signals and was derailed at Highworth Junction, Swindon, Wiltshire. A newspaper train, hauled by GWR 4073 Class 4-6-0 No. 5009 Shrewsbury Castle, collided with the wreckage.^[9]

Withdrawal of the class began in June 1962 with No. 4702, while the last were removed from service in May 1964.^[10][11] As a result of their limited usefulness, the mileages achieved by the class were not exceptional, with No. 4705 recording the greatest at 1,656,564 miles (2,665,981 km).^{[citation needed]}

No members of the class were preserved. However, the Great Western Society 4709 Group made the decision to create the next locomotive in the sequence, GWR 4709. Supported via a GWS sub-group; the plan was to build it using a mixture of new parts and others recycled from former Barry scrapyard locomotives:

• GWR 5101 class 2-6-2T 4115 - six of the eight driving wheels and the frame extension.^[12]
• GWR 2800 class 2-8-0 2861 - the cylinder block.
• GWR 5205 class 2-8-0T 5227 - the axleboxes, horns and other various components.
• GWR 4073 Class 4-6-0 7027 Thornbury Castle - the boiler.^[13][14][15]

The plates for the new frames were cut and machined in 2012.^{[citation needed]}

In order to fit within the more restrictive modern loading gauge, so that it could operate on the main line, the project has changed the plan to use the 2800 cylinder, and has instead had new cylinders designed and cast.^[16]

• List of GWR standard classes with two outside cylinders

• "Great Western Locomotive Types, 47xx". Retrieved 1 January 2006.
• Daniel, John (2000). "Great Western steam locomotives, '4700' class". The Great Western Archive. Retrieved 1 January 2006.
• Overton, Tim. "GWR Locomotive Evolution". Archived from the original on 21 August 2004. Retrieved 1 January 2006.{{cite web}}: CS1 maint: bot: original URL status unknown (link) _{( (as of 27 April 2006))}
• Whitehurst, Brian (1973). Great Western Engines, Names, Numbers, Types and Classes (1940 to Preservation). Oxford, UK: Oxford Publishing Company. pp. 42, 103, 138. ISBN 978-0-9028-8821-0. OCLC 815661.

• 4709 Restoration project
• Great Western Society 47XX Project