Advanced Passenger Train: Encyclopedia II - Advanced Passenger Train - Background

Advanced Passenger Train - Background

In the mid 20th century, British Rail express services were being compared unfavourably, and perhaps unfairly, with France's TGV and Japan's Shinkansen. Experience with High Speed Trains on the East Coast Main Line from London to Edinburgh had shown that reduced journey times could produce a significant increase in passenger numbers, but that line was largely straight and suited to high speeds. Other lines, such as the West Coast Main Line from London to Glasgow, were not straight enough to support high speeds with conventional equipment. Lateral forces would be just too high around corners; passengers would not be able to stand upright easily, and items would move on tables. Superelevation, banking of the track around curves, enabled speeds up to 125 mph but no higher.

In order to permit a top speed of 150 mph (240 km/h), and thereby cut journey times, British Rail's engineers at the Derby Research Division developed an advanced active tilting technology, using hydraulic rams controlled by computer to tilt the passenger cars into the curves so that no lateral forces would be felt. In 1972 the APT-E, a gas turbine-powered experimental testbed, was constructed. This was only four cars in length; two power cars, one at each end, and two 'passenger' cars full of instrumentation.

The experimental train APT-E having proved the concept, British Rail moved to build three prototype Class 370 APT-P trains. Gas turbines had been chosen for their light weight compared to diesel engines, but Leyland had ceased production and development, and no other was suitable. Thus the new APT-P and APT-S trains were to be electrically powered, and so restricted to electrified track.

At the time, pantograph technology could not support current collection from both ends of the train at the high speeds envisaged. Therefore, the APT-P trains were designed as two half-trains with twin power cars in the middle, sharing one pantograph. There was a passage through the power cars, but it was noisy, cramped and not normally permitted for passengers; therefore, each end of the train had to duplicate facilities.

Adapted from the Wikipedia article "Background", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki