| North British Type 2 diesel-electric British Railways Class 21 | |
| Powertype: | Diesel-electric |
| Fleetnumbers: | D6100–D6157 |
| Builder: | North British Locomotive Co. |
| Builddate: | 1958–1960 |
| Totalproduction: | 58 |
| Primemover: | MAN L12V18/21S |
| Tractionmotors: | 4 × GEC WT440 |
| Transmission: | Diesel electric |
| Generator: | DC |
| Britishclass: | Bo-Bo |
| Uicclass: | Bo'Bo' |
| Wheeldiameter: | 3feet |
| Minimumcurve: | 3.5sigfig=3NaNsigfig=3 |
| Trainbrakes: | Vacuum |
| Locobrakeforce: | 50LTf |
| Engine Total: | 37feet |
| Bogie: | 8feet |
| Pivotcentres: | 28feet |
| Over Buffers: | 51feet |
| Width: | 8feet |
| Height: | 12feet |
| Locoweight: | 72.5LT |
| Maxspeed: | 75mph |
| Poweroutput: | Engine: 1000abbr=on0abbr=on or 1100hp |
| Tractiveeffort: | Maximum: 45000lbf |
| Fuelcap: | 460impgal |
| Trainheating: | Spanner per hour Steam generator |
| Multipleworking: | D6100–D6137: ● Red circle D6138–D6157: ★ Blue star |
| Axleloadclass: | Route availability 6 (5 from 1969) |
| Operator: | British Rail |
| Retiredate: | 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 Thirty-eight of the locomotives were withdrawn by August 1968; the rest were rebuilt with bigger engines to become Class 29, although those locos only lasted until 1971.[1]
Under the British Railways Modernisation Plan, a batch of ten 1000sigfig=3NaNsigfig=3 diesel-electric locomotives were ordered from the North British Locomotive Co. for evaluation under BR's dieselisation pilot scheme. At the same time, six externally similar locomotives with hydraulic transmission were ordered for comparison, these becoming Class 22. Repeat orders resulted in a total of 58 of the diesel-electric locomotives being built (numbered D6100–6157). They were delivered between December 1958 and November 1960.
The first 38 locomotives entered service in 1958-59 from the Eastern Region depots at Stratford, Hornsey and Ipswich engine shed on commuter services into London, where they were evaluated against rival designs from English Electric, British Railways, Birmingham RC&W and Brush. The type proved chronically unreliable in Eastern Region service - by March 1960 the Hornsey allocation had moved to New England Yard, Peterborough for storage. This came to the attention of the newspapers and the Daily Telegraph reported that brand new diesel locomotives were being hidden and dumped, which caused questions to be asked in Parliament. The D6100s moved north to the Scottish Region in mid-April 1960, ostensibly to be nearer to the NBL works for repairs but allegedly to move them away from the eyes of the national press.
The final 20 locomotives had uprated 1100sigfig=3NaNsigfig=3 engines and were delivered to Kittybrewster depot on the Scottish Region. They were joined on the Scottish Region by the first 38 locos, which were allocated to Glasgow Eastfield depot, close to the North British factory at Springburn where they had been built. They were used widely across the Scottish Region on a range of work, freight, local passenger and express passenger, the latter sometimes in pairs. Common double headers included Oban & Callander workings, Glasgow-Dundee/Aberdeen expresses, and many freights, and the Ballater Royal train was entrusted to two locos with a standby. They were common on the West Highland lines, Great North of Scotland lines and in the works. Just one original locomotive, D6109, was repainted in BR Blue with headcodes.
| Code | Name | Quantity |
|---|---|---|
| 61B | 18 | |
| 65A | 19 | |
| 65B | 1 | |
| Rebuilt to class 29 (1963–67) | 20 | |
| Total built: | 58 | |
In an attempt to improve reliability, 20 locomotives (D6100–03, D6106-D6108, D6112–D6114, D6116, D6119, D6121, D6123, D6124, D6129, D6130, D6133, D6134 and D6137) were re-engined between 1963 and 1967 with 1350sigfig=3NaNsigfig=3 Paxman Ventura engines to form Class 29.[4]
The remaining 38 locomotives retained their original NBL/MAN engines until they were withdrawn from service between December 1967 and August 1968 and sold for scrap. Most were cut up by Scottish scrap dealers McWilliams of Shettleston or Barnes and Bell of Coatbridge, but locomotive D6122 was sold to Woodham Brothers scrapyard in Barry, Vale of Glamorgan, South Wales, after a re-railing demonstration at Hither Green, Southern Region on 2 November 1967 where it languished until 1980 before being broken up. None have survived.[5]