Looking back
Looking back: The advanced p
In the first of a
new series telling the story of a project from the
past, Colin Ledsome looks at
British Rail’s advanced passenger train.
E-train on test track
For 10 years, from 1970, I worked for British Rail (BR) on the advanced passenger train at the Railway Technical Centre in Derby. The programme had begun in the early 1960s with a research project to speed up 4-wheel freight wagons. Part of the legacy of the Beeching cutbacks of the 1950s was the consolidation of ‘fast’ and ‘slow’ lines into a single track over much of the system. The result was that freight trains, particularly the ubiquitous 4-wheel wagons of that time, limited to 72 km/h (45 mph), were getting in the way of the push to speed up passenger services. The speed limit was imposed because at around 90 km/h (55 mph) the 4-wheel suspension began to
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‘hunt’, oscillating from side to side with the wheel flanges striking sparks from the rails. This instability often led to derailment.
A small group of researchers were recruited from the aircraft industry, where they had worked on a similar instability of light aircraft nose wheels. They began by looking at the existing theories of wheel on rail stability. If you take a pair of rigidly connected conical wheels (a wheelset) and run them down parallel rails, they will tend to correct any misalignment or displacement by steering towards and across the centre line before steering back again from the other side. (You can try this with a pair of
plastic cups glued together running down two long rulers.) At normal running speeds, friction in the suspension removes the energy of these oscillations leaving the wheelset running stably on straight or gently curved track. The wheel flanges do not normally make contact and are only there as a safety measure and for any sudden changes at points and crossings. However, beyond a critical speed, the oscillation energy exceeds that which can be absorbed by the suspension and hunting begins.
To see this from the beginning, the new research team visited a workshop to see wheelsets being produced. Wheels are cast
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