LMS Ivatt Class 4

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LMS Ivatt Class 4
43001 at Bletchley Station
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 59.1 long tons (60.0 t; 66.2 short tons) Tender weight 40.3 long tons (40.9 t; 45.1 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: ​  • Grate area 23 sq ft (2.1 m2) Boiler LMS 4D Boiler pressure 225 lbf/in2 (1.55 MPa) Heating surface: ​  • Firebox 131 sq ft (12.2 m2)  • Tubes and flues 1,090 sq ft (101 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LMS: 3000–3009 BR: 43000–43161 Nicknames Mucky Ducks, Doodlebugs, Flying Pigs Axle load class BR: Route Availability 4 Withdrawn 1963–68 Disposition One preserved, remainder scrapped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) ordered 162 of this type between 1947 and 1952, but only three were built by the LMS before nationalisation in 1948. Designed by George Ivatt, they were classified 4F by the LMS and 4MT by British Railways (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.^[1]