The Bristol Lodekka was a half-cab low-height step-free double-decker bus built by Bristol Commercial Vehicles in England. It was the first production bus design to have no step up from the passenger entrance throughout the lower deck; although Gilford and Leyland Motors had developed low floor city buses in the 1930s, these did not enter production.
Design and development
The point of its design and introduction was to end the uncomfortable and inconvenient Lowbridge double-deck bus layout, replacing it by lowering the chassis frame and integrating it with the body and fitting a drop-centre rear axle, so that there were no steps from the rear entrance platform to the front of the passenger gangway, itself sunk about 10 cm (4 inches) below the seating platforms on the LDX, LD and first five LDLs. A full flat floor was developed on the last LDL, then used on the LDS and the F series Lodekkas. Bristol Commercial Vehicles, Eastern Coach Works and some of their employees obtained a number of patents relating to the design.
Bristol manufactured over 5,200 Lodekkas between 1949 and 1968 as a standard double-deck vehicle for the UK state-owned bus sector. With all examples bodied by Eastern Coach Works in Lowestoft, they have a traditional half-cab design and a lower floor level allowing a low overall height. The earlier LD-series and the later FL and FS had a rear platform, but the FSF and FLF had a forward (behind the front axle and driver's position, rather than 'front' ahead of the front axle and alongside the driver) entrance. Most were powered by five- or six-cylinder Gardner engines, with a small number having a Bristol or Leyland power unit.
An engineering option was designed to reduce the power loss due to engine radiator fan operation and to increase the heat available for heating of the passengers. After experiments by Wing-Commander T.R. Cave-Browne-Cave (CBC), Professor of Engineering at Southampton University, a satisfactory design was produced. The 'CBC' system involved two small engine radiators being placed above the driver's cab roof level at the front outer corners of the double deck to give maximum aerodynamic air flow. The engine coolant water was pumped around these instead of the traditional radiator. In cold weather, all or a portion of the air passing through these radiators, was diverted by flaps, the left into the upper saloon and the right to the lower deck. In hot weather, the flaps could be changed by push-pull levers in the driver's cab roof to divert all the hot air to the outside of the vehicle. The movement of the vehicle was (usually) adequate to cool the engine without the need for a fan or radiator at the traditional position in front of the engine. The traditional 'radiator' grille at the front of the vehicle was not required, but was usually retained (with a few exceptions) and blanked off behind. 'Varivane' wax capsule operated shutters were fitted in front of the upper radiators to keep the coolant at optimum temperature. There were some disadvantages to the scheme and eventually customers stopped specifying it.
The first prototype vehicle (chassis no. LDX001) was operated by Bristol Tramways & Carriage Company Ltd Ltd who designed and made the chassis at its 'MCW' (Motor Constructional Works) which at that time was still an integral part of the company. It was allocated fleet no. LC5000 and registered LHY 949. There is a story that the first vehicle originally had two separate propshafts – one to each rear wheel, with the differential at the front of the vehicle. This was soon changed to incorporate the differential into the off-side gear train - a concept still used today by several international bus manufacturers.
West Yorkshire Road Car Company had the second prototype Lodekka (chassis no. LDX002), originally fleet number 822 but renumbered DX1 under the April 1954 renumbering scheme, registered JWT 712, which operated in the Harrogate area. It lacked the distinctively stylish fairing of the production models. This bus was displayed at the Festival of Britain (South Bank Exhibition) in 1951.
Lodekka users in the UK included Brighton Hove & District, Bristol, Crosville, Cumberland, Eastern Counties, Eastern National, Hants & Dorset, Lincolnshire Road Car Co, Red & White Services, Scottish Omnibuses, Southern Vectis, South Wales, Luton & District, Thames Valley & Aldershot, United, United Counties, United Welsh, West Yorkshire Roadcar Co, Western National, Western Welsh, Central SMT and Wilts & Dorset. No Lodekkas were bought by any London-based companies, but they often worked into the capital on services operated by Thames Valley and Eastern National.