British Rail Class 73

British Rail Class 73

Class 73, no. 73201 at Woking. This locomotive was used by South West Trains as a "Thunderbird" to rescue failed trains.

Type and origin Power type Electro-diesel Builder 73/0: British Railways’ Eastleigh Works 73/1: English Electric at Vulcan Foundry Build date 1962, 1965–1967 Total produced 49

Specifications Configuration Bo-Bo AAR wheel arr. B-B UIC class Bo'Bo' Gauge 4 ft 8 1⁄2 in (1,435 mm) standard gauge Wheel diameter 3 ft 4 in (1,016 mm) Length 16.36 m (53 ft 8 in) Loco weight 73/0: 76.30 long tons (77.52 t; 85.46 short tons) 73/1: 76.80 long tons (78.03 t; 86.02 short tons) Electric system(s) 660–750 V DC Third rail Current collection Contact shoe Prime mover English Electric 4SRKT Mk II 2 x Cummins QSK19 (73951-2) MTU R43 4000 (73961-971) Traction motors 73/0: EE 542A 73/1: EE 546/1B Train heating Electric Train Heating Train brakes Vacuum, Air and Electro-Pneumatic

Performance figures Maximum speed 73/0: 80 mph (129 km/h) 73/1: 90 mph (145 km/h) Power output Electric (continuous): 1,420 hp (1,059 kW) Electric (one-hour): 1,600 hp (1,193 kW) Engine: 600 hp (447 kW) Tractive effort 73/0 (electric): 42,000 lbf (186.8 kN) 73/0 (diesel): 34,100 lbf (151.7 kN) 73/1 (electric): 40,000 lbf (177.9 kN) 73/1 (diesel): 36,000 lbf (160.1 kN)

Career Operators British Rail Gatwick Express GB Railfreight South West Trains Numbers E6001–E6049; later 73001–73006, 73101–73142 Axle load class Route availability 6

The British Rail Class 73 is a British model of electro-diesel locomotive. The type is unusual in that it can operate from the Southern Region's 650/750 V DC third-rail or an on-board diesel engine to allow it to operate on non-electrified routes. This makes it very versatile, although the diesel engine produces less power than is available from the third-rail supply so the locomotives rarely stray from the former Southern Region of British Rail. Following the withdrawal and scrapping of the more powerful Class 74 electro-diesels in 1977, the Class 73 is now unique on the British railway network. Ten locomotives have been scrapped.

These locomotives were ordered as part of the British Railways 1955 Modernisation plan which included the extension of the Southern Region electrification to various main lines.

They were intended as mixed-traffic locomotives, hauling parcels, freight and also passenger trains, usually on routes that included some non-electrified sections, such as boat trains.

This class of 49 locomotives were built in two batches using English Electric components. The first six locomotives were built by BR at Eastleigh works in 1962 and were numbered E6001-E6006 and classified as type JA. With the introduction of TOPS in 1968 they were to have been classified as Class 72, to differentiate from the later built units. However, instead they became Class 73/0. In the early 1970s the locomotives were renumbered 73001-73006.

Following successful trials of the initial locomotives, a production run of 43 locomotives were built by English Electric at their Vulcan Foundry between 1965 and 1967. They were initially classified as Class JB and numbered E6007-E6049. They differed slightly from the six earlier machines, most notably having an increased tractive effort as well as a higher maximum speed (90 mph as opposed to 80). Following the introduction of TOPS, they became Class 73/1 and were renumbered 73101-73142. One locomotive, E6027, had already been withdrawn following accident damage and so was not renumbered. Further changes were the use of large round Oleo buffers with a pneumatic withdrawal mechanism rather that the traditional coach style (oval) saddle buffer which relied on a pin and spring mechanism. As the JA examples came in for overhaul over the years, the saddle buffers were also replaced making visual identification of the differing machines almost impossible from a distance.