GWR Dean experimental locomotives

This locomotive appeared in 1880 as a 4-4-0T, but was rebuilt in 1882 as a 2-4-0T. It was withdrawn in 1924.

Number 7 was built in 1886 at Swindon as a tandem compound 2-4-0 with 7 ft 0+1⁄2 in (2.146 m) coupled wheels and outside frames. The 23 in (584 mm) diameter low pressure cylinders were in front of the high pressure cylinders, the pistons being carried on the same piston rod. Valves for the low pressure cylinders were below, and those for the high pressure cylinders above the cylinders. One set of valve gear drove each pair of valve spindles. This setup proved difficult to access for maintenance, and the locomotive was relegated to minor routes. It was broken up in 1890.[1] The wheel centres were used in building No. 7 of the Armstrong class.[2]

Number 8 was built in 1886 as a 7 ft 1⁄4 in (2,140 mm) broad gauge convertible 2-4-0 tandem compound, the low- and high-pressure piston rods sharing a common crosshead. It had 7 ft 0+1⁄2 in (2.146 m) driving wheels, six plate frames and a high-pressure boiler rated at 180 lbf/in² (1.2 MPa). The frames consisted of a double frame supporting the driving axleboxes, and an external frame from which the hornblocks for the leading wheels projected. Unsuccessful in its trials, it was never taken into stock or converted to 4 ft 8+1⁄2 in (1,435 mm) standard gauge. In 1894 the wheel centres were used in a conventional standard gauge 4-4-0, No. 8 of the Armstrong class.[3]

This unit started out in 1881 as a 4-2-4T, with two 7 ft 8 in (2.34 m) diameter driving wheels and unusually large 18 in × 26 in (457 mm × 660 mm) cylinders. It was the only 4-2-4T locomotive built by the Great Western Railway (though not the only such tank locomotive operated by the Great Western, which inherited some from the Bristol and Exeter Railway). It did little work as it was prone to derailing, indeed it did this in front of William Dean on its first trial move out of the shed.

In 1884, it was rebuilt as an unconventional 2-2-2 tender locomotive with outside Stephenson valve gear. In 1890, it was rebuilt with more standard double frames and inside valve gear similar in style to the Queen Class. In this guise it was named Victoria in honour of Queen Victoria.

A 2-2-2 locomotive that, as with number 9, was eventually rebuilt to be similar to the Queen class. In this latter guise it was named Royal Albert in honour of Prince Albert, husband of Queen Victoria.

Tank locomotive number 13 first appeared in 1886 as a 2-4-2WT, or well tank. In this form it worked on the St Ives branch and also on the Watlington branch.

In 1897, it was rebuilt as a 4-4-0ST, or saddle tank. The large bunker and rear water tank were reduced in size. This allowed the rear carrying wheels to be removed, and a saddle tank fitted over the boiler. The frames were extended to allow the fitting of a bogie truck at the front. It continued to work on various branch lines, being loaned to the Liskeard and Looe Railway and later continuing to work on the Looe branch. It was also recorded on the Highworth and Brixham branches, and working in the Plymouth area, before finally moving to Swindon, from where it was withdrawn in 1926.

Two rather more conventional 2-4-0 express locomotives were turned out in 1888 and ran on the broad gauge. They were similar to the standard gauge 3206 Class Barnum's turned out in 1889 but with large 7 ft 0+1⁄2 in (2,146 mm) in driving wheels.

Following the abolition of the broad gauge in 1892, they were renewed, reappearing as standard gauge 4-4-0 locomotives in 1894.

In 1898, after Churchward had become Dean's assistant, a solitary 4-4-0PT was built at Swindon (Lot no. 114, works no. 1702), and was the first GWR locomotive with pannier tanks. It had 4 ft 7+1⁄2 in (1,410 mm) driving wheels, and was intended as the prototype of a new class for working over the Metropolitan Railway, but was both unstable and too heavy. After a few years spent shunting, it was sold in 1907 by the GWR to the Ebbw Vale Steel, Iron & Coal Co. In 1908 it came into the possession of the Brecon and Merthyr Tydfil Junction Railway, which numbered it 35, but sold it again in 1916 to the Cramlington Colliery Co. It was eventually scrapped in 1929.[4][5]

• Reed, P.J.T. (February 1953). White, D.E. (ed.). The Locomotives of the Great Western Railway, Part 2: Broad Gauge. Kenilworth: The Railway Correspondence and Travel Society. ISBN 0-901115-32-0.
• Casserley, H.C.; Johnston, Stuart W. (1966). Locomotives at the Grouping: Great Western Railway. Shepperton: Ian Allan Publishing. ISBN 0-7110-0555-9. 1527/319/DXX 267.
• Davies, F.K.; Firth, J.M.; Lucking, J.H.; Thomas, R.E.; Allcock, N.J.; Sterndale, A.C.; Barrie, D.S.M.; Reed, P.J.T.; Mountford, E.R. (April 1966). White, D.E. (ed.). The Locomotives of the Great Western Railway, part ten: Absorbed Engines, 1922-1947. RCTS. ISBN 0-901115-20-7.
• Nock, O.S. (1977). Standard Gauge Great Western 4-4-0s: Part 1: Inside Cylinder Classes 1894-1910. Newton Abbot: David and Charles. ISBN 0-7153-7411-7.
• Russell, J.H. (1975). A Pictorial Record of Great Western Engines, Volume 1. Oxford: Oxford Publishing Company. ISBN 0-86093-398-9.
• Tabor, F.J. (August 1959). White, D.E. (ed.). The Locomotives of the Great Western Railway, part six: Four-Coupled Tank Engines. RCTS. ISBN 0-901115-36-3.