British Rail Class 25

British Rail Class 25
Class 25/3 in BR blue at Manchester Victoria in 1980.
Type and origin Power type Diesel-electric Builder British Railways' Crewe Works, Darlington Works and Derby Works; Beyer, Peacock & Co. Build date 1961–1967 Total produced 327
Specifications Configuration: ​  • AAR B-B  • UIC Bo'Bo'  • Commonwealth Bo-Bo Gauge 4 ft 8+1⁄2 in (1,435 mm) standard gauge Wheel diameter 3 ft 9 in (1.143 m) Minimum curve 4.5 chains (91 m) Wheelbase 36 ft 6 in (11.125 m) Length 50 ft 6 in (15.392 m) Width 9 ft 1 in (2.769 m) Height 12 ft 8 in (3.861 m) Loco weight 73 long tons (74.2 t; 81.8 short tons) Fuel capacity 500 imp gal (2,300 L; 600 US gal) Prime mover Sulzer 6LDA28-B Generator BTH generator, type RTB 15656 Traction motors D5151–D5175, four BTH traction motors others: four AEI 253 AY traction motors DC Transmission Diesel electric MU working ★ Blue Star Train heating Steam (when present) Train brakes 25001 – 25082: Vacuum 25083 – 25247: Air and Vacuum (Dual Braked)
Performance figures Maximum speed 90 mph (145 km/h) Power output Engine: 1,250 hp (932 kW) @750 rpm Tractive effort Maximum: 39,000 lbf (170 kN) to 45,000 lbf (200 kN) Brakeforce 38 long tons-force (380 kN)
Career Operators British Railways Numbers D5151–D5299, D7500–D7677; later 25001–25327 Nicknames Rats Axle load class Route availability 4 Retired 1984–1987 Disposition 20 preserved, 307 scrapped

The British Rail Class 25, also known as the Sulzer Type 2, is a class of 327 diesel locomotives built between 1961 and 1967 for British Rail. They were numbered in two series, D5151–D5299 and D7500–D7677.^[1]

The first 25 locos became known as Class 25/0 and were built at BR Darlington Works. The Class 25/1 locomotives were built at Darlington and BR Derby Works. The Class 25/2 locomotives were built at Derby with some built at Darlington. The final batch of locomotives were designated Class 25/3 and built by Derby Works and Beyer, Peacock and Company of Manchester.