British Rail Class 52

British Rail Class 52

British Railways Western Class 52 D1062 'Western Courier' and train leaving Minehead on the West Somerset Railway

Type and origin Power type Diesel-hydraulic Builder British Railways' Swindon and Crewe Works Build date 1961–1964 Total produced 74

Specifications Configuration C-C AAR wheel arr. C-C UIC class C'C' Gauge 4 ft 8 1⁄2 in (1,435 mm) standard gauge Wheel diameter 3 ft 7 in (1.092 m) Minimum curve 4.5 chains (300 ft; 91 m) Wheelbase 54 ft 8 in (16.66 m) Length 68 ft 0 in (20.73 m) Width 8 ft 8 in (2.64 m) Height 12 ft 11 3⁄4 in (3.96 m) Loco weight 108 long tons (110 t; 121 short tons) Fuel capacity 850 imp gal (3,900 l; 1,020 US gal) Prime mover Maybach MD655 (64.5 L or 3,940 cu in), 2 off Transmission Hydraulic MU working Not fitted Train heating Steam Train brakes Vacuum; later Dual (Air and Vacuum)

Performance figures Maximum speed 90 mph (140 km/h) Power output Engines: 1,350 bhp (1,007 kW)at 1500 rpm × 2 At rail: 2,000 hp (1,491 kW) Tractive effort Maximum: 66,700 lbf (297 kN) Continuous: 45,200 lbf (201 kN)@ 14.5 mph (23.3 km/h)[1] Loco brakeforce 50 long tons-force (498 kN)

Career Operators British Railways Numbers D1000–D1073 Nicknames 'Westerns','Wizzos'& "Thousands" Axle load class Route availability 7 Retired 1973–1977 Disposition 7 preserved, remainder scrapped

British Rail (BR) assigned Class 52 to the class of 74 large Type 4 diesel-hydraulic locomotives built for the Western Region of British Railways between 1961 and 1964. All were given two-word names, the first word being "Western" and thus the type became known as Westerns.

When switching to diesel traction as part of the Modernisation Plan of the 1950s, BR designed, and commissioned designs for, a large number of locomotive types. At this time (and arguably right up until Sectorisation in 1982), BR's regions had a high degree of autonomy, which extended as far as classes of locomotives ordered and even the design criteria for those locomotives. Whilst almost all other diesel locomotives were diesel-electric, the Western Region employed a policy of using diesel-hydraulic traction, originally commissioning three classes of main line locomotives: a type 2 and two type 4s (later designations class 22, class 41 and class 42). With pressure to increase the speed of the transition from steam to diesel, volume orders for the class 22 and class 42 (along with a similar design class 43) followed in 1957, a mere two years after the original orders and well before any idea of performance or reliability could be gained. At the same time it was realised that all the existing orders (diesel-electric and diesel-hydraulic) were for types 1, 2 and 4; thus orders were placed for 101 Type 3 diesel-hydraulics (later Class 35). However the increasing demands for more powerful locomotives prompted a further order, in 1961, for 74 diesel-hydraulics of 2,700 hp (2,000 kW); so when the first locomotive was outshopped from Swindon Works in December 1961, less than a year after the order was placed, the Westerns were born.

The theoretical advantage of diesel-hydraulic was simple: it resulted in a lighter locomotive than equivalent diesel-electric transmission. This provided better power/weight ratio and decreased track wear. Unfortunately, it had several key disadvantages: