Armstrong Whitworth Order No.DT8, carrying No.D9 of 1933 would become the first mainline diesel locomotive to run in Great Britain.Photograph courtesy Armstrong Whitworth/Diesel Railway Traction
During 1933 Armstrong Whitworth Co. of Newcastle upon Tyne released for trials on the LNER a 1-Co-1 diesel electric locomotive. The 74 ton locomotive had been designed as a mixed traffic machine, with a maximum axle loading of 17 tons, a maximum starting tractive effort of 28,500lb and a maximum speed of 70mph. Although only one locomotive was built it was fitted with multiple unit working capability with the intention that two locomotives could be worked by one driver on goods trains up to 1,500 tons and 500 ton passenger trains up to 60mph on level track. A single unit was permitted to haul 800 ton freights or 260 ton passenger trains.
The 1-Co-1 wheel arrangement (2-6-2 ’Prairie’ steam classification) utilised 4 ft diameter driving wheels with Isothermos axle boxes with an equalised spring arrangement allowing useage over indifferent track. Sanding was provided on the two outside driving wheels with air supplied from a small compressor. Braking was by means of the automatic vacuum system, two large cylinders applied brake blocks to all the driving wheels.