# LMS/BR Class 4 2-6-4T locomotives

The London, Midland and Scottish Railway and British Railways Class 4 2-6-4T was a family of classes of steam locomotives. A grand total of 800 engines were built to five separate designs by four different mechanical engineers, over a period of 29 years. Each new design was a development of the previous one. The LMS gave the whole family the power classification 4P, BR 4MT. It is therefore worth considering them as a group as follows:
| LMS Nos | BR Nos | Design | Designer | Built | Built by LMS | Built by BR | Total built |
| 2300–2424 | 42300–42424 | Fowler | Henry Fowler | 1927–1934 | 125 | 0 | 125 |
| 2500–2536 | 42500–42536 | Stanier, 3 cylinder | William Stanier | 1934 | 37 | 0 | 37 |
| 2425–2494, 2537–2672 | 42425–42494, 42537–42672 | Stanier, 2 cylinder | William Stanier | 1935–1943 | 206 | 0 | 206 |
| 2187–2299, 2673–2699 | 42050–42299, 42673–42699 | Fairburn | Charles Fairburn | 1945–1951 | 130 | 147 | 277 |
| — | 80000–80154 | BR Standard | Robert Riddles | 1951–1956 | 0 | 155 | 155 |
| | | | Total | 1927–1956 | 498 | 302 | 800 |

## Withdrawal

All engines were withdrawn from stock between 1959 and 1967, summarised as follows:
Locomotives withdrawn by year :
| Year | Fowler | Stanier, 3-cylinder | Stanier, 2-cylinder | Fairburn | BR Standard | Total |
| 1959 | 5 | 0 | 0 | 0 | 0 | 5 |
| 1960 | 11 | 1 | 2 | 0 | 0 | 14 |
| 1961 | 22 | 7 | 17 | 3 | 0 | 49 |
| 1962 | 37 | 29 | 43 | 43 | 1 | 153 |
| 1963 | 16 | 0 | 29 | 30 | 0 | 75 |
| 1964 | 20 | 0 | 51 | 57 | 31 | 159 |
| 1965 | 12 | 0 | 38 | 54 | 44 | 148 |
| 1966 | 2 | 0 | 11 | 48 | 54 | 115 |
| 1967 | 0 | 0 | 15 | 42 | 25 | 82 |
| Total | 125 | 37 | 206 | 277 | 155 | 800 |
Locomotives in service at year end :
| Year | Fowler | Stanier, 3-cylinder | Stanier, 2-cylinder | Fairburn | BR Standard | Total |
| 1958 | 125 | 37 | 206 | 277 | 155 | 800 |
| 1959 | 120 | 37 | 206 | 277 | 155 | 795 |
| 1960 | 109 | 36 | 204 | 277 | 155 | 781 |
| 1961 | 87 | 29 | 187 | 274 | 155 | 732 |
| 1962 | 50 | 0 | 144 | 231 | 154 | 579 |
| 1963 | 34 | 0 | 115 | 201 | 154 | 504 |
| 1964 | 14 | 0 | 64 | 144 | 123 | 345 |
| 1965 | 2 | 0 | 26 | 90 | 79 | 197 |
| 1966 | 0 | 0 | 15 | 42 | 25 | 82 |
| 1967 | 0 | 0 | 0 | 0 | 0 | 0 |

## Technical comparison

For technical purposes, it is worth splitting the Fairburn tanks into two subclasses; early (42050–42146) and late (42147–42699) as their weights differ slightly.
| Attribute | Fowler | Stanier, 3 cylinder | Stanier, 2 cylinder | Fairburn (early) | Fairburn (late) | BR Standard |
| Leading wheel diameter | 3 ft 3+1⁄2 in (1.003 m) | 3 ft 3+1⁄2 in (1.003 m) | 3 ft 3+1⁄2 in (1.003 m) | 3 ft 3+1⁄2 in (1.003 m) | 3 ft 3+1⁄2 in (1.003 m) | 3 ft 0 in (0.914 m) |
| Driving wheel diameter | 5 ft 9 in (1.753 m) | 5 ft 9 in (1.753 m) | 5 ft 9 in (1.753 m) | 5 ft 9 in (1.753 m) | 5 ft 9 in (1.753 m) | 5 ft 8 in (1.727 m) |
| Trailing wheel diameter | 3 ft 3+1⁄2 in (1.003 m) | 3 ft 3+1⁄2 in (1.003 m) | 3 ft 3+1⁄2 in (1.003 m) | 3 ft 3+1⁄2 in (1.003 m) | 3 ft 3+1⁄2 in (1.003 m) | 3 ft 0 in (0.914 m) |
| Wheelbase | 38 ft 6 in (11.73 m) | 38 ft 6 in (11.73 m) | 38 ft 6 in (11.73 m) | 37 ft 1 in (11.30 m) | 37 ft 1 in (11.30 m) | 36 ft 10 in (11.23 m) |
| Length | 47 ft 2+3⁄4 in (14.40 m) | 47 ft 2+3⁄4 in (14.40 m) | 47 ft 2+3⁄4 in (14.40 m) | 45 ft 9+3⁄4 in (13.96 m) | 45 ft 9+3⁄4 in (13.96 m) | 44 ft 9+7⁄8 in (13.66 m) |
| Weight | 86.25 long tons (87.63 t) | 92.25 long tons (93.73 t) | 87.75 long tons (89.16 t) | 85.25 long tons (86.62 t) | 84.70 long tons (86.06 t) | 86.50 long tons (87.89 t) |
| Axleload | | | | | | 17.95 long tons (18.24 t) |
| Coal capacity | 3.50 long tons (3.56 t) | 3.50 long tons (3.56 t) | 3.50 long tons (3.56 t) | 3.50 long tons (3.56 t) | 3.50 long tons (3.56 t) | 3.50 long tons (3.56 t) |
| Water capacity | 2,000 imp gal (9,100 L) | 2,000 imp gal (9,100 L) | 2,000 imp gal (9,100 L) | 2,000 imp gal (9,100 L) | 1,875 imp gal (8,500 L) | 2,000 imp gal (9,100 L) |
| Boiler | G8AS | 4C | 4C | 4C | 4C | ABR5 |
| Boiler pressure | 200 psi (1.38 MPa) | 200 psi (1.38 MPa) | 200 psi (1.38 MPa) | 200 psi (1.38 MPa) | 200 psi (1.38 MPa) | 225 psi (1.55 MPa) |
| Firegrate area | 25 sq ft (2.3 m$^2$) | 25 sq ft (2.3 m$^2$) | 25 sq ft (2.3 m$^2$) | 25 sq ft (2.3 m$^2$) | 25 sq ft (2.3 m$^2$) | 26.7 sq ft (2.48 m$^2$) |
| Heating surface: Tubes | 1,082 sq ft (100.5 m$^2$) | 1,011 sq ft (93.9 m$^2$) | 1,011 sq ft (93.9 m$^2$) | 1,011 sq ft (93.9 m$^2$) | 1,011 sq ft (93.9 m$^2$) | 1,223 sq ft (113.6 m$^2$) |
| Heating surface: Firebox | 138 sq ft (12.8 m$^2$) | 137 sq ft (12.7 m$^2$) | 137 sq ft (12.7 m$^2$) | 137 sq ft (12.7 m$^2$) | 137 sq ft (12.7 m$^2$) | 143 sq ft (13.3 m$^2$) |
| Superheater area | 266 sq ft / 246 sq ft | 160 sq ft/154 sq ft | 160 sq ft/154 sq ft | 160 sq ft/154 sq ft | 160 sq ft/154 sq ft | 240 sq ft (22 m$^2$) |
| Cylinders | 2 outside | 3 (1 inside, 2 outside) | 2 outside | 2 outside | 2 outside | 2 outside |
| Cylinder size | 19 in × 26 in (483 mm × 660 mm) | 16 in × 26 in (406 mm × 660 mm) | 19.625 in × 26 in (498 mm × 660 mm) | 19.625 in × 26 in (498 mm × 660 mm) | 19.625 in × 26 in (498 mm × 660 mm) | 18 in × 28 in (457 mm × 711 mm) |
| Tractive effort | 23,125 lbf (102.87 kN) | 24,598 lbf (109.42 kN) | 24,671 lbf (109.74 kN) | 24,671 lbf (109.74 kN) | 24,671 lbf (109.74 kN) | 25,515 lbf (113.50 kN) |
* ↑ Derby Lots 177, 185, 186, and 196: locomotives 42147–42699, built 1945–1949
* ↑ Derby Lots 202, 210, and all Brighton-built locomotives: numbers 42050–42146, built 1948–1951