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TheGreat Western RailwayIron Duke Class4-2-2 was a class of7 ft 1⁄4 in (2,140 mm)broad gaugesteam locomotives for express passenger train work.

The prototype locomotive,Great Western,^{[Note 1]} was built as a2-2-2 locomotive in April 1846, but was soon converted to a4-2-2 arrangement, with the leading wheels set rigidly within thesandwich framing, rather than in a separatebogie.^[1][2] The remainder of the class entered service between April 1847 and July.

The Iron Duke locomotives were fast for their time, and were recorded reaching 78.2 mph (125.9 km/h).^[3] They were used to haul theFlying Dutchman express train, which was the fastest express train in the world for several decades. In 1852, the daily service fromLondon Paddington toExeter (194 miles or 312 km) was achieved with an average speed of 53 mph (85 km/h), with the flatter section between London andSwindon covered at an average speed of 59 mph (95 km/h).^[4]

From about 1865, the Iron Duke Class was known as theAlma Class.

In May to July 1870, three locomotives (Great Britain,Prometheus andEstaffete) were extensively rebuilt with new frames and boilers, but retaining their original names. Following these, further locomotives were built to similar specifications, entering service between August 1871 and July 1888. These new locomotives are generally referred to as theRover class. Although these locomotives took the names of withdrawn locomotives of the original design, they were not rebuilt from them like the first three, but entirely new locomotives (though it is believed thatRover,Swallow andBalaklava may have included some parts from the earlier locomotives of those names).^[5]

Apart from the three conversions, the original locomotives were withdrawn between December 1870 and June 1884.Lord of the Isles (the last to be withdrawn) was initially preserved by the GWR atSwindon Works, but wasscrapped in January 1906 owing to the pressure of space. The three conversions were withdrawn between September 1880 and October 1887, while the other locomotives to the later design were all withdrawn with the end of the GWR7 ft 1⁄4 in (2,140 mm)broad gauge in May 1892 (exceptHirondelle, which had been withdrawn in December 1890).

Many of the nameplates can be seen at theNational Railway Museum and at theMuseum of the Great Western Railway, while the driving wheels fromLord of the Isles can also be seen at Swindon.

The prototype for this class was named theGreat Western and built in 1846. Named after the railway, it was designed to show how the 2-2-2 express engines could be improved; its 8-foot-diameter (2.438 m) driving wheels were one foot (305 mm) larger than those of the successfulFire Fly class. It broke its leading axle after a short while in service and was subsequently rebuilt as a 4-2-2, becoming part of the Iron Duke class.

Iron Duke Class
Hirondelle
Type and origin Power type Steam Designer Daniel Gooch Builder GWRSwindon Works (22) Rothwell and Company (7) Order number Swindon 2nd, 3rd, and 4th Lot Passenger Build date April 1847 – July 1855
Specifications Configuration: ​  • Whyte 4-2-2  • UIC 2A1 n2 Gauge 7 ft 1⁄4 in (2,140 mm) Leading dia. 4 ft 6 in (1.372 m) Driver dia. 8 ft 0 in (2.438 m) Trailing dia. 4 ft 6 in (1.372 m) Wheelbase 2nd Lot Passenger: 4 ft 11 in (1.499 m) + 6 ft 3 in (1.905 m) + 7 ft 4 in (2.235 m) 3rd/4th Lot Passenger: 4 ft9+1⁄4 in (1.454 m) + 6 ft4+1⁄4 in (1.937 m) + 7 ft 7 in (2.311 m) Boiler pressure 100 lbf/in2 (690 kPa), later 115 lbf/in2 (790 kPa) Cylinder size 18 in × 24 in (457 mm × 610 mm)

Rover Class (or Iron Duke Class rebuilt)
Dragon atTaunton while working the last broad gauge train from London to Penzance on 20 May 1892
Type and origin Power type Steam Designer Joseph Armstrong Builder Great Western Railway
Specifications Configuration: ​  • Whyte 4-2-2  • UIC 2A1 n2 Gauge 7 ft 1⁄4 in (2,140 mm) Leading dia. 4 ft 6 in (1.372 m) Driver dia. 8 ft 0 in (2.438 m) Trailing dia. 4 ft 6 in (1.37 m) Wheelbase 19 ft 0 in (5.791 m) Cylinder size 18 in × 24 in (457 mm × 610 mm)

A working replica ofIron Duke was constructed in 1985 using parts from twoHunslet Austerity tanks for the 'Great Western 150' celebrations. It is part of the National Railway Collection but is currently on long-term loan to theDidcot Railway Centre, which has a section of working broad gauge track.^[10] The boiler certificate has expired so it cannot currently be steamed.^{[citation needed]}

The replica appeared inThe Railway Series bookThomas and the Great Railway Show, in which it was portrayed with whiskery eyebrows and awalrus moustache.

Wikimedia Commons has media related toGWR Iron Duke replica.

• Reed, P. J. T. (February 1953). White, D. E. (ed.).The Locomotives of the Great Western Railway, Part 2: Broad Gauge. Kenilworth:RCTS.ISBN 0-901115-32-0.OCLC 650490992.{{cite book}}:ISBN / Date incompatibility (help)

• "What was the Broad Gauge?". The Broad Gauge Society.

• Great Western Railway locomotives
• 4-2-2 locomotives
• Broad gauge (7 feet) railway locomotives
• Railway locomotives introduced in 1846
• Railway locomotives introduced in 1871

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