Recognition and Equipment information
CLASS 21/29

Under the BTC modernisation pilot scheme, the North British Locomotive Co. of Glasgow was contracted to build a fleet of 10 Type B (later Type 2) locos. During construction of the original contract, a subsequent order for 48 more examples was placed. The number range allocated was D6100-D6151.
The power unit used was the German design, British built MAN L12V18/21 developing 1,100hp. Coupled to this was GEC electrical equipment. The first locomotive was built at the NBL's Queen's Park Works in 1958, commencing testing in December and arriving in London in January 1959, allocated to Hornsey . In a period of just under four months all 10 pilot locos were delivered, all allocated to Hornsey for GN suburban-line duties . In May 1959 the 'production' fleet commenced delivery, also going to ER London sheds. By early 1960 major technical problems were identified, mainly involving the coupling between the power unit and generator, and the performance of the engine. In September 1960 the BTC decided to reallocate the entire fleet to Scotland where more suitable duties were available, and they were close to the builder's works for major repair work to be carried out.
Such were the problems with this fleet that in early 1963 No. D6123 was dispatched to Davey Paxman's works in Colchester where a Paxman 'Ventura' engine was fitted. The loco was then tested in Scotland and a decision taken that this power unit was more reliable than the original type, culminating in a fleet of 20 locos being re-engined. The new engines gave the fleet slightly increased power, 1,350hp compared to the 1,OOOhp of the original 10 locomotives and 1,100hp of the production fleet. After locomotives had been fitted with Paxman engines they were reclassified 29.
The locomotives that retained original power units were, to say the least, unreliable, and withdrawn during 1968. Under the National Traction Plan re-engined examples were permitted to carry on working in Scotland, remaining active until late 1971. All locos were then sold for scrap, with no examples preserved.
When constructed the locos were in all over BR green livery, small yellow ends being added in the early 1960s. Locos rebuilt as Class 29 emerged in two-tone green with yellow panels/ends. A handful of machines did emerge in BR standard rail blue in the late 1960s.

North British Type 2 diesel-electric side elevation, showing the first loco of the build No. D6100 carrying its running number at one end only. The loco is painted in BR standard loco green livery. Note the footsteps on the near end which gave access into the boiler water filler port. CJM Collection.

Front end detail, showing a fitter filling the locos sand boxes from an overhead gantry dispenser. Front end equipment consisted of two central doors, which allowed communication between locos when working in multiple. The disc type of train reporting equipment is carried. On the buffer beam, a steam pipe, vacuum pipe, coupling, air control pipes and multiple control jumpers can be seen. No. D6110 is illustrated. CJM Collection.