The British Rail Class 47 is a class of British railway diesel-electric locomotive that was developed in the 1960s by Brush Traction. A total of 512 Class 47s were built at Crewe Works and Brush’s Falcon Works, Loughborough between 1962 and 1968, which made them the most numerous class of British mainline diesel locomotive.
They were fitted with the Sulzer 12LDA28C twin-bank twelve-cylinder unit producing 2,750 bhp (2,050 kW) – though this was later derated to 2,580 bhp (1,920 kW) to improve reliability – and have been used on both passenger and freight trains on Britain’s railways for over 50 years. Despite the introduction of more modern types of traction, as of 2013 a significant number are still in use, both on the mainline and on heritage railways. As of July 2015, 82 locomotives still exist as Class 47s, with further examples having been converted to other classes; approximately 30 retain “operational status” on the mainline.
The Class 47 history begins in the early 1960s with the stated aim of the British Transport Commission (BTC) to completely remove steam locomotives from British Rail by a target date of 1968. They therefore required a large build of lightweight Type 4 locomotives to achieve this aim. This required locomotives producing at least 2,500 bhp (1,900 kW) but with an axle load of no more than 19 long tons (19 t). However, the BTC were not convinced that the future of diesel traction lay down the hydraulic transmission path of the Western Region, and began looking at various diesel-electric designs.
Despite the construction of two demonstration locomotives (D0260 LION, produced by AEI and BRC&W using a Sulzer engine, and D0280 FALCON, built by Brush Traction using Maybach engines), the need for a large number of locomotives quickly was deemed paramount, and the pilot build of what would become Class 47 began before the prototypes could be comprehensively assessed. This initial build of 20 locomotives (Nos. D1500 to D1519) were mechanically different from the remainder of the type, and would be withdrawn earlier. However, based on these and the success of LION, an order for 270 locomotives was made, which was later revised upwards a number of times to reach the final total of 512. Five locomotives, Nos. D1702 to D1706, were fitted with a Sulzer V12 12LVA24 power unit and classified as Class 48s; the experiment was not deemed a success, and they were later converted to standard 47s.
Eventually, 310 locomotives were constructed by Brush in Loughborough, and the remaining 202 at BR’s Crewe Works. The first 500 locomotives were numbered sequentially from D1500 to D1999, with the remaining twelve being numbered from D1100 to D1111. The locomotives went to work on passenger and freight duties on all regions of British Rail. Large numbers went to replace steam locomotives, especially on express passenger duties.
The locomotives, bar a batch of 81 built for freight duties, were all fitted with steam heating boilers for train heat duties. The initial batch of twenty, plus D1960 and D1961, were also fitted with electric train heating (ETH). With this type of heating becoming standard, a further large number of locomotives were later fitted with this equipment.
In the mid 1960s, it was decided to de-rate the engine output of the fleet from 2,750 bhp (2,050 kW) to 2,580 bhp (1,920 kW). This significantly improved reliability by reducing stresses on the power plant, whilst not causing a noticeable reduction in performance
In the early 1970s, the fleet was renumbered into the 47xxx series to conform with the computerised TOPS systems. This enabled a number of easily recognisable sub-classes to be created, depending on the differing equipment fitted. The original series were based on train heating capability and were as follows;
Class 47/0: Locomotives with steam heating equipment
Class 47/3: Locomotives with no train heating
Class 47/4: Locomotives with electric train heating
However, this numbering system was later disrupted as locomotives were fitted with extra equipment and were renumbered into other sub-classes. For an overview of the renumbering see the Class 47 renumbering page. This section summarises the main sub-classes that were created.