How to ensure a comfortable ride

David Russell was Mechanical & Electrical Engineer (Locomotive), C.M. & E.E. Department, York, at the time the HSTs were introduced on the Eastern Region. In the IC125 Review, he explained how a comfortable 125mph was achieved from the engineer’s view.

“August 1970 saw a start made on an urgent and exciting new project at the Railway Technical Centre in Derby. A 125mph high speed diesel train. High speed, that is, but with standards of comfort so high that passengers would hardly notice the speed.”

Russell explained that reaching that speed needed high power, but had to be done economically and without damaging the track, so a low weight was required. Engineers examined options, while also considering the likely high costs and the rising cost of both maintenance and fuel.

Two quick-running high-power 2,250hp 12-cylinder diesel engines were selected, each in a power car. The electric power they generated was fed into four powerful electric motors in each power car. They powered the bogies via a flexible drive. The welded steel body structure was aided through the use of computer modelling, while the cab was an aerodynamic glass fibre creation and described as “complex”. The windscreen was designed to withstand the impact of a 2lb brick at 190mph.

There was also a need to be able to stop the 125mph trains in the same distance as a 100mph locomotive-hauled train, and so this was built into the specification.

Highly efficient compressed-air disc brakes were fitted and controlled electrically from the cab. Air-sprung bogies were also fitted, which Russell says were key to the smoothness of the ride.