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British Rail Class 52

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British Rail Class 52

The British Rail Class 52 is a class of 74 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. They were also known as Wizzos and Thousands. The final Class 52 locomotives were withdrawn from service in 1977.

When switching to diesel traction as part of the Modernisation Plan of the 1950s, British Railways (BR) designed, and commissioned designs for, a large number of locomotive types. At this time 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 a better power/weight ratio and decreased track wear. Unfortunately, it had several key disadvantages.

The technology was proven in continental Europe, particularly Germany, but was new to the UK. At the time, it was considered politically unacceptable for the UK government to order railway rolling stock from foreign companies, especially German companies so soon after the Second World War. This resulted in most of the engines and transmissions being manufactured in the United Kingdom under licence from the German manufacturers.

Experience showed that the Bristol-Siddeley-Maybach engines were superior to those made by North British Locomotive Company-MAN and although the use of twin engines in the same locomotive was new, the design did not produce any insurmountable problems. In the end the diesel-hydraulic experiment foundered on low fleet numbers, poor maintenance conditions and design issues; not on its German heritage or development of a novel configuration. BR's Swindon Works maintained all the diesel-hydraulic locomotives, and their early demise resulted in a much reduced workload and hastened its eventual closure in 1986.[citation needed]

With the Hymeks and Warships already in service but proving underpowered for top-link services, BR Western Region needed a high-powered locomotive for these trains – the Western therefore needed two diesel engines to achieve the required power output. In keeping with their policy, a new locomotive with a hydraulic transmission was envisaged. Experience had shown that the Maybach engines in the Hymeks were superior to the earlier Maybach and MAN engines used in the Warships, particularly in power output. Also Maybach were able to offer their MD655 engines (an intercooled version of the MD650 used in Class 42) rated at 1,350 bhp (1,010 kW) allied to a Voith L630rV transmission; a Mekydro transmission designed to handle such power could not be fitted into the British loading gauge.

Prototypes sited the engines behind the driving cabs but drivers found this too noisy; moving the engines centrally meant making the locomotive heavier, removing some of the design's advantage. In operational use, the dual-engine arrangement turned out to have some advantages: in particular, the Westerns were able to continue operating with a single engine running in situations where more conventional single-engine designs would require rescue by another locomotive.[citation needed]

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