British Rail Class 55

English Electric Type 5 British Rail Class 55
A Class 55 at Princes Street Gardens, Edinburgh in September 1980.
Type and origin Power type Diesel-electric Builder English Electric at Vulcan Foundry Build date 1961–1962 Total produced 22
Specifications Configuration: ​  • UIC Co′Co′  • Commonwealth Co-Co Gauge 4 ft 8+1⁄2 in (1,435 mm) standard gauge Wheel diameter 3 ft 9 in (1.143 m) Wheelbase 58 ft 6 in (17.83 m) Length 69 ft 6 in (21.18 m) Width 8 ft 9+1⁄2 in (2.68 m) Height 12 ft 10 in (3.91 m) Loco weight 99 long tons (101 t; 111 short tons) Fuel capacity 900 imp gal (4,100 L; 1,100 US gal) Prime mover Napier Deltic D18-25, × 2 Generator English Electric DC generator Traction motors DC traction motors Transmission Diesel electric MU working Not fitted Train heating Steam; later Electric Train Heating Train brakes Vacuum; later Dual (Air and Vacuum)
Performance figures Maximum speed 100 mph (160 km/h) Power output Engines: 1,650 bhp (1,230 kW) × 2 (Total: 3,300 bhp (2,460 kW)) Tractive effort Maximum: 50,000 lbf (222 kN) Continuous: 30,500 lbf (136 kN)@ 32.5 mph (52.3 km/h)[1][2]
Career Operators British Railways Numbers D9000–D9021; later 55 022, 55 001–55 021 Nicknames Deltics Axle load class Route availability 5 Withdrawn 1980–1982 Preserved 55 022 (D9000), 55 002 (D9002), 55 009 (D9009), 55 015 (D9015), 55 016 (D9016) and 55 019 (D9019). Cabs from 55 008 (D9008) and 55 021 (D9021) also preserved. Disposition Six preserved, remainder scrapped

The British Rail Class 55, also known as a Deltic, or English Electric Type 5, is a class of diesel locomotive built in 1961 and 1962 by English Electric for British Railways. Twenty-two locomotives were built, designed for the high-speed express passenger services on the East Coast Main Line (ECML) between Edinburgh and London King's Cross. They gained the name "Deltic" from the prototype locomotive, DP1 Deltic (the running number DP1 was never carried), which in turn was named after its Napier Deltic power units.

At the time of their introduction into service in 1961, the Class 55s were the most powerful single-unit diesel locomotives in the world, with a power output of 3,300 hp (2,500 kW).^[3] They had an official maximum speed of 100 miles per hour (160 km/h), and introduced the first regular 100 mph diesel passenger service to Britain, they were however capable of higher speeds than this, and often exceeded their official maximum in service, especially in their later years, with speeds of up to 117 miles per hour (188 km/h), being recorded on level gradients, and up to 125 miles per hour (201 km/h) whilst descending Stoke Bank.^[4]

Despite their successes, the Deltics had a relatively short commercial service life of 20 years. From 1978 they were displaced by the next generation of high speed diesels, the "InterCity 125" High Speed Trains (HSTs) and the Deltics were subsequently relegated mostly to secondary services on the Kings Cross to York, Edinburgh and Hull routes, although they continued to operate some top-link trains until 1981, such as the Hull Executive. As a small non-standard fleet with high running costs, no viable alternative use could be found for the Deltics, and all were withdrawn from service between January 1980 and December 1981. Six of the locomotives were saved for preservation.