Leyland Atlantean - The Prototypes

The Prototypes

In the years immediately following the Second World War, bus operators in the UK faced a downturn in the numbers of passengers carried and manufacturers began looking at ways to economise. A few experimental rear-engined buses had been produced before the war but none successfully made it beyond the prototype stage. The need to minimise the intrusion of the engine into passenger carrying space was a priority, leading to several underfloor-engined single-deck designs. However, such designs raised the height of the floor of the vehicle, forcing additional steps at the entrance. On double decker buses, these problems were amplified, causing either an increase in the overall height of the vehicle or an inadequate interior height.

In 1952, Leyland began experimenting with ideas for a rear-engined double-decker bus. A prototype was built, with a body by SARO, to the maximum permitted width of 7 feet 6 inches (2.29 m). It was fitted with a turbocharged version of the Leyland O.350 engine, which was transversely mounted at the rear of the sub-frame. The chassis was a platform-type frame of steel and light alloy with deep stressed side-members. An automatic clutch and self change gearbox were also fitted. The vehicle, numbered 530001, registered STF90 was designated the PDR1 (R for "Rear-engined").

In 1956, a second prototype, XTC684 (No. 542209) was constructed, this time with a Metro-Cammell body and, again equipped with the O.350 engine fitted across the frame. It had a centrifugal clutch, Pneumocyclic gearbox and angle drive. This vehicle was 13 feet 2.75 inches (4.0323 m) in height, with a 16-foot-2.875-inch (4.94983 m) wheelbase and overall length of 29 feet 10 inches (9.09 m) and had a seating capacity of 78. Leyland christened this prototype the Lowloader.

Though two prototypes were thoroughly tested, the same problem of a front-engined bus remained — they had rear entrances with the space alongside the driver being wasted.