LSWR Class H15

LSWR H15 class
Official 1914 LSWR works photograph of Urie H15 class mixed-traffic locomotive No. 483 at Eastleigh. Smoke deflectors were fitted during the early 1930s .
Type and origin Power type Steam Designer Robert Urie Builder SR Eastleigh Works Build date 1914 (11) 1924–1925 (15) Total produced 26
Specifications Configuration: ​  • Whyte 4-6-0  • UIC 2′C h2 Gauge 4 ft 8 1⁄2 in (1,435 mm) standard gauge Leading dia. 3 ft 7 in (1.092 m) Driver dia. 6 ft 0 in (1.829 m) Length 65 ft 6 3⁄4 in (19.98 m) Loco weight Various – 79 long tons 19 hundredweight (81.2 t) to 82 long tons 1 hundredweight (83.4 t) Fuel type Coal Fuel capacity 5 long tons (5.1 t; 5.6 short tons) Water cap 5,000 imp gal (23,000 l; 6,000 US gal) Boiler pressure New: 180 psi (1.24 MPa) Rebuilt E14: 175 psi (1.21 MPa) Cylinders Two, outside Cylinder size 21 in × 28 in (533 mm × 711 mm)
Performance figures Tractive effort 26,240 lbf (116.72 kN)
Career Operators London and South Western Railway → Southern Railway → British Railways (Southern Region) Class LSWR/SR: H15 Power class LSWR / SR: A BR: 4MT, later 4P5F Numbers LSWR: 335, 482–491 SR: E330–E335, E473–E478, E482–E492, E521–E524 → 330–335, 473–478, 482–492, 521–524 BR: 30330–30335, 30473–30478, 30482–30491, 30521–30524 Nicknames Chonker Withdrawn 1955–1961 Disposition All scrapped

The LSWR/SR H15 class was a class of 2-cylinder 4-6-0 steam locomotives designed by Robert Urie for mixed-traffic duties on the LSWR. Further batches were constructed by Richard Maunsell for the SR.

The H15 class represented Robert Urie's first design for the LSWR. It was created in response to a desperate lack of adequate locomotives in service on the LSWR that could be utilised for heavy freight duties. Reliability was also an issue, with ageing locomotive designs taking their toll on the LSWR's resources.

The resultant design was an outside 2-cylinder locomotive fitted with outside Walschaerts valve gear for ease of maintenance, with all the working parts relatively accessible when compared to previous designs operating on the LSWR system.

Ten locomotives (numbers 482–491) were built new by Eastleigh Works with 180 lbf/in² (1.24 MPa) boilers. They appeared in January to July 1914. Urie was a proponent of superheating, so in order to gain experience and data on performance and fuel economy, four of the locomotives (482–485) were fitted with Schmidt superheaters, four (486–489) with Robinson superheaters, and two (490–491) were built as saturated locomotives. The last two had a lower weight than the first eight.

While the data gained from this small experiment showed the benefits of superheating, neither design of superheater was deemed suitable by Urie, so he designed and patented his own: the Eastleigh superheater, which was subsequently fitted to all members of the H15 class.

An additional locomotive was a rebuild of the 1905-vintage E14 class locomotive, number 335, undertaken in December 1914. This one-locomotive class had been earmarked by Urie's predecessor, Dugald Drummond, for major modifications in the light of poor operational performance. Urie however, instead of modifying it, rebuilt it as the eleventh member of the H15 class. It was the first locomotive to be fitted with an Eastleigh superheater, but it retained its original boiler pressure of 175 lbf/in² (1.21 MPa).