Class 37 (English Electric 1,750hp Type 3 Diesel-Electric)

The Class 37 has been one of the workhorses of the British railways network since the 1960s and while their numbers have decreased in recent years many still perform a valuable role day in and day out for both the main line and preserved railways. The Class 37 is a Type 3 diesel locomotive and after its introduction in the early 1960s it was found this power band (1,750hp in the Class 37's case) was highly versatile and more so compared to the Type 2s which dominated early dieselisation efforts and often were underpowered. This power availability coupled with a relatively low axle loading for a locomotive of this size meant the Class 37 could handle a wide variety of mixed traffic from secondary passenger services to freight and engineering trains across much of the network. Work it continues to this day, Class 37s can be found hauling freights, engineering trains and even passenger trains on the network.

Number built: 309
Built: 1960-65
Builder: English Electric
Engine: English Electric 12CSVT diesel
(37/9 fitted with Mirrlees Blackstone MB275Tt or Rushton RK270Tt)
Power: 1,750 hp (1,305 kW)
Wheel arrangement: Co-Co

Between 1960 and 1965 309 Class 37s were built by English Electric and proved to be one of the most reliable classes of diesel locomotive built for British Rail [1]. Though with their front end "noses" they were rather dated in appearance when they entered service as other locomotive types had moved to flat fronted designs (indeed they were the last class built for BR with front noses). However the appearance was due to English Electric being reluctant to leave the American styling they had championed since Deltic [2] and the locomotives reused some tooling and equipment from the earlier Class 40. This reduced the unit price to British Rail which no doubt helped to overcome any doubts over the aesthetics! [3]

Around 35 are still registered for use on Network Rail and some will remain in service for some time following refurbishments. Many Class 37s have also been preserved.

As can be expected with a large fleet that has remained in service for over 50 years there have been a number of sub-class variants of the Class 37 mostly following a series of refurbishments in the 1980s [4].

Sub-class Details
37/0 Original / unchanged locomotives
37/3 Received new bogies
37/4 Refurbished and fitted with Electric Train Heating (ETH)
37/5 Refurbished but without ETH
37/6 Modified to haul heavy freight
37/7 Also fitted to haul heavy freight, extra ballast added to aid adhesion
37/9 Rebuilt with Mirrlees or Rushton engines for testing for a planned replacement Type 3 locomotive (the Class 38) though this project was later cancelled.

Four Class 37s have also been rebuilt as 97/3s for a trial project of the European Rail Traffic Management System (ERTMS). They work development trains over the Cambrian line and other Network Rail engineering trains.
Europhoenix 37 800 at Derby

Split headcode front end

DRS 37 601 at Crewe

Side view of 37 601

Colas 37 421 at Derby

Network Rail 97 303 at Derby

[1] Colin J. Marsden, Traction Recognition (2nd Edition) (Ian Allan, 2008) p. 28
[2] David Lawrence, British Rail Designed 1948-97 (Ian Allan, 2016) p. 145
[3] Brian Haresnape, Production Diesel-Electrics Types 1-3 (Ian Allan, 1983) p. 67
[4] Pip Dunn, British Rail Main Line Locomotives Specification Guide (Crowood Press, 2013) p. 65