LMS Ivatt Class 4

LMS Ivatt Class 4

LMS Ivatt Class 4 2-6-0 M3009 (later 43009) as built with double chimney, at Horwich Works in 1948

Type and origin Power type Steam Designer H.G. Ivatt Builder LMS/BR Horwich Works (75) BR Doncaster Works (50) BR Darlington Works (37) Build date 1947-1952 Total produced 162

Specifications Configuration: ​  • Whyte 2-6-0  • UIC 1′C h2 Gauge 4 ft 8 1⁄2 in (1,435 mm) standard gauge Leading dia. 3 ft 0 in (0.914 m) Driver dia. 5 ft 3 in (1.600 m) Length 55 ft 11 in (17.04 m) Loco weight 59.10 long tons (60.05 t; 66.19 short tons) Tender weight 40.30 long tons (40.95 t; 45.14 short tons) Fuel type Coal Fuel capacity 4 long tons (4.1 t; 4.5 short tons) Water cap 3,500 imp gal (16,000 l; 4,200 US gal) Firebox:  • Firegrate area 23 sq ft (2.1 m2) Boiler LMS 4D Boiler pressure 225 lbf/in2 (1.55 MPa) Heating surface:  • Tubes and flues 1,090 sq ft (101 m2)  • Firebox 131 sq ft (12.2 m2) Superheater: ​  • Heating area 231 or 247 sq ft (21.5 or 22.9 m2) Cylinders Two, outside Cylinder size 17 1⁄2 in × 26 in (444 mm × 660 mm) Valve gear Walschaerts

Performance figures Tractive effort 24,170 lbf (107.51 kN)

Career Operators London, Midland and Scottish Railway British Railways Power class LMS: 4F, later 4 BR: 4MT Numbers LMS: 3000–3009 BR: 43000–43161 Nicknames Mucky Ducks, Flying Pigs Axle load class BR: Route Availability 4 Withdrawn 1963–68 Disposition One preserved, remainder scrapped

The LMS Ivatt Class 4 2-6-0 is a class of steam locomotive primarily designed for medium freight work but also widely used on secondary passenger services. The London Midland and Scottish Railway (LMS) built 162 of this type between 1947 and 1952, but only three were built by the LMS before nationalisation in 1948. Designed by H.G. Ivatt, they were classified 4F by the LMS and 4MT by BR. In BR days they were used extensively across the system, being prevalent on the London Midland region and to a lesser extent elsewhere, notably on the Midland and Great Northern Joint Railway, an East Anglian line that had previously been joint owned by the LMS and LNER, where they became the dominant locomotive type. They were also used for a short period on the Somerset and Dorset Joint Railway, but were quickly transferred elsewhere, never to return, because of poor steaming on the line's long and steep gradients – this was before modifications were made to the design which improved steaming notably.

The first three engines were numbered 3000–3002 by the LMS, but became 43000–43002 when renumbered by BR – 40000 was added to the running number to indicate an ex-LMS locomotive. The remaining 159, built by BR, continued the number sequence: 43003–43161. Construction was divided between different locations, 75 were completed at Horwich Works, 50 at Doncaster Works and 37 at Darlington Works. The class was also sometimes called mucky ducks or doodle-bugs or even Flying Pigs.

The design was noted for its American looks – the running-plates were positioned at a high level and a gap left ahead of the cylinders. Because of this many locomotive enthusiasts considered it to be the ugliest British locomotive produced, especially those locomotives outshopped with double chimneys (the first 50 engines); however, these gave poor performance and were quickly replaced with single chimneys. The locomotives also incorporated new mechanical features intended to reduce maintenance costs. The utilitarian appearance was a deliberate design decision as there are sketches which show the locomotive with conventional curved running plates.

The BR Standard Class 4 2-6-0 was based on this design. Its looks were improved somewhat by the re-design of the outside foot-plating, to include a sloping plate to fill the gap ahead of the cylinders.