British Rail Class 21 (NBL)

North British Type 2 diesel-electric British Railways Class 21
D6103 at Harringay West in 1959.
Type and origin Power type Diesel-electric Builder North British Locomotive Co. Build date 1958–1960 Total produced 58
Specifications Configuration: ​  • UIC Bo'Bo'  • Commonwealth Bo-Bo Gauge 4 ft 8+1⁄2 in (1,435 mm) standard gauge Wheel diameter 3 ft 7 in (1,092 mm) Minimum curve 3.5 chains (231 ft; 70.4 m) Wheelbase: ​  • Engine 37 ft 0 in (11,278 mm)  • Bogie  8 ft 6 in (2,591 mm) Pivot centres 28 ft 6 in (8,687 mm) Length: ​  • Over buffers 51 ft 6 in (15,697 mm) Width  8 ft 8 in (2,642 mm) Height 12 ft 8 in (3,861 mm) Loco weight 72.5 long tons (73.7 t; 81.2 short tons) Fuel capacity 460 imp gal (2,100 L; 550 US gal) Prime mover MAN L12V18/21S Generator DC Traction motors 4 × GEC WT440 Transmission Diesel electric MU working D6100–D6137: ● Red circle D6138–D6157: ★ Blue star Train heating Spanner 1,500 pounds (680 kg) per hour Steam generator Train brakes Vacuum
Performance figures Maximum speed 75 mph (121 km/h) Power output Engine: 1,000 hp (746 kW) or 1,100 hp (820 kW) Tractive effort Maximum: 45,000 lbf (200.2 kN) Brakeforce 50 long tons-force (500 kN)
Career Operators British Rail Numbers D6100–D6157 Axle load class Route availability 6 (5 from 1969) Retired 1967–1968 Disposition 20 rebuilt to Class 29, remainder scrapped

The British Rail Class 21 was a type of Type 2 diesel-electric locomotive built by the North British Locomotive Company in Glasgow for British Rail in 1958–1960. They were numbered D6100-D6157. Thirty-eight of the locomotives were withdrawn by August 1968; the rest were rebuilt with bigger engines to become Class 29, although those locos only lasted until 1971.^[1]