Class 25 (BR / Sulzer 1,250hp Type 2 Diesel-Electric)

Following on from the Class 24, the Class 25 Type 2 diesel-electric locomotive was built in large quantities in the 1960s and became a very common sight on British Rail in the late 1960s and 1970s before being phased out in the 1980s.

The early Class 25s shared the same design flaws of the Class 24 such as the awkward layout of the engine room which hindered maintenance and the position of air intake louvres and filters (some of which got so filthy they stopped working). The draughtiness of the cab was also a problem largely thanks to the seldom used gangway doors [1]. During the long production run a number of improvements were made which are detailed below.

D7535 at Kidderminster Town

Information
Number built:	327
Built:	1961-67
Builder:	BR Derby, Darlington, Crewe and Beyer Peacock
Motor:	Sulzer 6LDA 28B diesel
Power:	1, 250 hp (932 kW)
Wheel arrangement:	Bo-Bo

The Class 25s were mixed traffic locomotives, spending much of their time on freight duties (not all were fitted with train heating boilers) and also some cross-country passenger services [2]. As the 1980s wore on the changing nature of the freight business meant they were becoming underpowered and regional cross country passenger duties were increasingly going over to multiple units. They were all withdrawn by 1987 though twenty have been preserved.



Class 25 sub-classes are listed below but there were also differences within sub-classes too especially with respect to train heating provision (or lack of).

Sub-class	Details
25/0	Original, very similar to Class 24 but with uprated engine
25/1	Improved lighter traction motor and other weight saving measures
25/2	Redesigned interior, air filter louvre layout and cab with gangway doors removed
25/3	Final version with improved equipment
25/9	Locomotives dedicated to mineral traffic

D7629 at Duffield

D7659 at Rowsley South

D7535 at Hampton Loade

D7612 at Chinnor

D7535 at Kidderminster Town

[1] Brian Haresnape, Production Diesel-Electrics Types 1-3 (Ian Allan, 1983) p. 33
[2] John Vaughan, Diesels on the London Midland (Ian Allan, 1981) p. 30