Class 23

The success of the revolutionary Deltic diesel engine and the Deltic prototype saw British Railways explore the possibility of putting a single cut-down version of the engine in a smaller mixed-traffic locomotive in the Type B (later 2) power classification. The Class 23 "Baby Deltic" was hence born for services on the Great Northern network [1]. With hindsight the experiment and resulting small fleet of Type 2 locomotives was an unnecessary mistake. There was found to be no real advantage over similar sized locomotives with traditional diesel engines but the Deltic also bought with it extra complexity and cost [2]. The Baby Deltics owed little to their larger brethren except for the engine technology and in design and cab terms owed a lot to the Class 40.

Information
Number built: 10
Built: 1959
Builder: English Electric
Engine: Napier T9-29 Deltic diesel
Power: 1, 100 hp (820 kW)
Formation: Bo-Bo

The fleet was refurbished in 1963 and modernised with a 4 character headcode replacing the original headcode discs and gangway doors [3]. They continued to serve though had high maintenance costs and passengers and crews found they had excessive noise and fumes in operation. With these disadvantages and being such a tiny fleet there was no way the Baby Deltics could survive the fleet rationalisation at the end of the 1960s and all were withdrawn from normal service by 1971. One survived with the Railway Technical Centre and hauled test trains until 1975 [4] but was scrapped like the rest of the class. No Baby Deltics now exist though the Baby Deltic Project aim one day to built a replica.
D5901 at Doncaster in 1959, photographer unknown

[1] John Vaughan, Diesels on the Eastern (Ian Allan, 1982) p. 31
[2] Brian Haresnape, Early Prototype and Pilot Scheme Diesel-Electrics (Ian Allan, 1981) p. 72
[3] Haresnape p. 75
[4] Colin J. Marsden, 25 Years of Railway Research (OPC, 1989) p. 67