British Rail DP1

English Electric DELTIC prototype

DP1 at the Ribble Steam Railway in 2015

Type and origin Power type Diesel-electric Builder English Electric at Dick, Kerr & Co Works, Preston Serial number EE: 2003 Build date 1955

Specifications UIC class Co'Co' Gauge 4 ft 8 1⁄2 in (1,435 mm) standard gauge Wheel diameter 3 ft 7 in (1,092 mm) Loco weight 106 long tons (108 t; 119 short tons) Prime mover Napier Deltic D18-25 (2 off) Traction motors EE 526/A, 6 off Cylinders 18 × 2 Transmission Diesel Electric Train heating Stone-Vapor/Clarkson steam generator

Performance figures Maximum speed 90 mph (140 km/h) 106 mph (171 km/h) from 1956 Power output 3,300 hp (2,500 kW) Tractive effort 90 mph gearing: 60,000 lbf (266.89 kN) 106 mph gearing: 52,500 lbf (233.53 kN)

Career Operators British Railways Power class Type 5 Numbers DP1 Official name DELTIC Retired March 1961 Disposition Preserved at the National Railway Museum Shildon

English Electric DP1, commonly known as Deltic, was a prototype 3,300 hp (2,500 kW) demonstrator locomotive employing two Napier Deltic engines, built by English Electric in 1955.

The high power of the locomotive at an acceptably low axleload resulted in 22 similar locomotives being ordered by British Railways for use on East Coast Main Line express passenger services; the serial production of which became the British Rail Class 55.

The English Electric company, which had absorbed the engine-maker Napier & Son into its group at the instruction of the Ministry of Aircraft Production in 1942, was a major builder of diesel and electric locomotives. The two George Nelsons (Sir George, and his son, known in the works as "Half") saw the potential of Napier's Deltic engine for rail traction and in 1954–1955 built a demonstrator at its Dick, Kerr works in Preston. Officially numbered DP1, its internal project title was Enterprise, and it was intended that the locomotive would carry that name. However, in 1954, before completion, Hudswell Clarke announced a range of small diesel-mechanical locomotives using the same name. After initial trials in 1955, the locomotive received the DELTIC in large cream letters on its sides, and the name became synonymous with the locomotive.

Long aluminium beadings on the sides were painted cream, a visual device to make the locomotive's high sides appear more slender and add to the impression of speed. Three curved chevrons on each nose, in the same cream, added to that effect. To British eyes, the locomotive's styling was reminiscent of American locomotives, such as the EMD E-unit or ALCO PA designs (partly because English Electric initially planned to offer the type for export), with high noses and small, somewhat swept-back cab windows set behind them. To add to the American look of the locomotive, a large headlight was to have been fitted to each nose (the lights were never installed but would have been of the rotating 'Mars Light' type as fitted to North American locomotives of the era). Two 18-cylinder Deltic engines were fitted, derated from the 1,750 horsepower (1.3 MW) of the marine engines in minesweepers to 1,650 horsepower (1.2 MW) each, generating 3,300 horsepower (2.5 MW) total. This derating reduced the stress on the engines, thereby increasing the service life and length of time between overhauls.