The UK’s first Tram-Train project/trial — the Sheffield-Rotherham Tram-Train scheme — has reached a new milestone in its development, with the completion of a new wheel-rail interface profile. This new wheel profile will allow the Tram-Train vehicle to operate efficiently, and safely, on two very different railway infrastructures — on both the tight radius curves of the embedded city centre track, and also on the higher speed but less curvaceous portions of the Network Rail mainline, both of which feature relatively distinct rail head shapes.
The new wheel profile will now be tested by both the SST project team, and the Rail Safety and Standards Board (RSSB). If approved for running on the mainline, the Tram-Train test running in the UK will begin shortly thereafter.
For those unfamiliar with the concept — simply put, the Tram-Train concept allows a railway vehicle to run in two distinct and continuous operational modes/environments, serving both relatively dense city centers as an on-street tram, and areas further from the city as a commuter train. Needless to say, the concept has some definite upsides to it, but it also requires a greater deal of regulation than either modalities do on their own. The concept was pioneered in Germany, and, in recent years, has now begun spreading to other regions of Europe.
The press release from the University of Huddersfield provides more:
The Sheffield-Rotherham Tram-Train scheme represents the UK’s first trial of the concept and has provided the project partners, the Department for Transport, Network Rail (NR), Northern Rail, Stagecoach Supertram (SST) and South Yorkshire Passenger Transport Executive with many challenges. As Dr Paul Allen, Assistant Director of the University of Huddersfield’s Institute of Railway Research (IRR), and project manager, explains: “One of these challenges is the wheel-rail interface, key to the vehicles’ safe operation and a major driver for the ongoing life-cycle maintenance costs of the system.”
By applying advanced computer modelling techniques, the team at the IRR has been able to predict vehicle dynamic behaviour on both the tight radius curves (<25m) of embedded city centre track and also the higher speed but less curvaceous sections on Network Rail mainline.
“These differing conditions require an interface design which maintains vehicle dynamic stability on straight track, whilst allowing adequate curving performance and derailment resistance in the city centre — a classic engineering compromise in railway vehicle dynamics,” said Dr Allen. The wheel profile was also required to operate under differing wheelset geometry conditions. This required a special stepped-wheel flangeback to maintain safe passage through both NR and SST switches and crossings and checked curves.
David Crosbee, one of the Senior Research Fellows at the IRR, adds more: “The wheel design work was complicated by the very different rail head shapes of the two systems; the SST network having a very flat rail head profile, whilst the worn NR rail sections typically have a much smaller effective rail head shape. This necessitated compromise in the wheel and tread design with significant simulation work being carried out to optimise the new wheel profile shape. This allowed wheel-rail contact stress and wear rates to be minimised on both systems, whilst also maintaining safety against derailment.”