British Rail Class 23

English Electric Type 2
British Rail Class 23

"Baby Deltic" D5901 with the revised cab front

Type and origin Power type Diesel-electric Builder English Electric at Vulcan Foundry Build date 1959 Total produced 10

Specifications Configuration Bo-Bo UIC class Bo'Bo' Gauge 4 ft 8 1⁄2 in (1,435 mm) standard gauge Wheel diameter 3 ft 7 in (1.092 m) Minimum curve 4 chains (80 m) Wheelbase 40 ft 6 in (12.34 m) Length 52 ft 6 in (16.00 m) Width 8 ft 10 3⁄4 in (2.71 m) Height 12 ft 8 in (3.86 m) Loco weight 74 long tons (75.2 t; 82.9 short tons) Fuel capacity 550 imp gal (2,500 l; 660 US gal) Prime mover Napier T9-29 Deltic Generator DC Traction motors DC Transmission diesel electric MU working ★ Blue star Train heating Steam Train brakes Vacuum

Performance figures Maximum speed 75 mph (121 km/h) Power output Engine: 1,100 hp (820 kW) Tractive effort Maximum: 47,000 lbf (209.1 kN)

Career Operators British Railways Numbers D5900–D5909 Nicknames Baby Deltic

The British Rail Class 23 were a class of ten Bo-Bo diesel-electric locomotives built by the English Electric Company (EE) in 1959. The power unit used was a Napier Deltic T9-29 9-cylinder engine of 1,100 bhp (820 kW) driving an EE generator, which powered the four traction motors. They were numbered from D5900 to D5909.

The T9-29 diesel engine was a single, half-sized version of those used in the more powerful British Rail Class 55 'Deltic' locomotives, and the overall design and external appearance of the Class 23 was also similar to the Class 55, but much shorter, leading to their nickname of Baby Deltics.

On initial completion, the first locomotives were found to weigh 3 long tons (3.05 t; 3.36 short tons) over the specification weight of 72 long tons (73.2 t; 80.6 short tons). A programme of lightening was begun: some of this involved cutting circular lightening holes into the bogie frames, and replacing steel buffer beams or roof panels with aluminium. Much of the over-weight was due to ancillary components, particularly the train-heating steam generators, being supplied over weight. To avoid waste, these components were replaced by lighter versions from other makers, but the heavier originals were then used in the Class 20 and Class 40 locomotives. The lightened locomotives eventually met British Rail's approval, but only after a painstaking weighing that involved specifying the amount of sand in the sandboxes and other precise details.

After acceptance trials at Doncaster, they entered service between April and June 1959. They were based at Hornsey, although at weekends were usually located at Hitchin engine shed. It had been British Rail's original intention to work the locos across London on the widened lines but the locomotives were found to be too heavy. The first of the class was held at Vulcan Foundry whilst EE tried to reduce the weight but this could not be completed to a satisfactory standard.