British Rail Class 20

English Electric Type 1
British Rail Class 20

British Railways Class 20 D8098 and train at Tunbridge Wells West on the Spa Valley Railway

Type and origin Power type Diesel-electric Builder English Electric at Vulcan Foundry and Robert Stephenson and Hawthorns Build date 1957-1968 Total produced 228

Specifications Configuration: ​  • Whyte Bo-Bo  • UIC Bo'Bo' Gauge 4 ft 8 1⁄2 in (1,435 mm) standard gauge Wheel diameter 3 ft 7 in (1.092 m) Minimum curve 3.5 chains (70 m) Wheelbase 32 ft 6 in (9.91 m) Pivot centres 24 ft 0 in (7.32 m) Length 46 ft 9 1⁄4 in (14.256 m) Width 8 ft 9 in (2.67 m) Height 12 ft 7 5⁄8 in (3.851 m) Loco weight 73 t (72 long tons; 80 short tons) Fuel capacity 380 imp gal (1,700 l; 460 US gal) Lubricant cap. 100 imp gal (450 l; 120 US gal) Coolant cap. 130 imp gal (590 l; 160 US gal) Prime mover English Electric 8 SVT Mk.II Generator DC Traction motors D8000–D8049: EE 526/5D Remainder: EE 526/8D Cylinder size 10 in (250 mm) Transmission Diesel electric Gear ratio 63:17 MU working ★ Blue Star Train heating None Train brakes Vacuum, Dual or Air

Performance figures Maximum speed 75 mph (121 km/h) Power output Engine: 1,000 hp (746 kW) Tractive effort Maximum: 42,000 lbf (186.8 kN) Continuous: 25,000 lbf (111.2 kN)@ 11 mph (17.7 km/h) Brakeforce 35 long tons-force (349 kN)

Career Operators Direct Rail Services HNRC Numbers D8000–D8199, D8300–D8327; later 20001–20228 Nicknames Chopper Axle load class Route availability 5

The British Rail (BR) Class 20, otherwise known as an English Electric Type 1, is a class of diesel-electric locomotive. In total, 228 locomotives in the class were built by English Electric between 1957 and 1968, the large number being in part because of the failure of other early designs in the same power range to provide reliable locomotives.

The locomotives were originally numbered D8000–D8199 and D8300–D8327. They are known by railway enthusiasts as "Choppers", a name derived from the distinctive beat that the engine produces when under load which resembles the sound of a helicopter.

Designed around relatively basic technology, the 73-tonne locomotives produce 1,000 horsepower (750 kW) and can operate at up to 75 mph (121 km/h). Designed to work light mixed freight traffic, they have no train heating facilities. Locomotives up to D8127 were fitted with disc indicators in the style of the steam era; when headcodes were introduced in 1960 the locomotive’s design was changed to incorporate headcode boxes. Although older locomotives were not retro-fitted with headcode boxes, a few of the earlier batch acquired headcode boxes as a result of repairs. Unusually for British designs, the locomotive had a single cab. This caused serious problems with visibility when travelling nose first, though in these circumstances the driver's view is comparable to that on the steam locomotives that the Class 20s replaced. It was common however to find Class 20s paired together at the nose, with their cabs at opposite ends, ensuring that the driver could quite clearly see the road ahead.

The Class 20 saw only limited service on passenger trains. A small number were fitted with a through pipe for steam heating, primarily for use in conjunction with a Class 37 locomotive on the West Highland Line. Otherwise their use was limited to summer relief services, particularly to Skegness often under the adopted title of The Jolly Fisherman starting from various places including Burton-on-Trent, Stoke-on-Trent, Derby and Leicester. Also occasionally other holiday resorts on the east coast of England, occasional duties as a pilot, and short distance diversions of electric-hauled trains over non-electrified lines.