UK: An IMechE seminar on February 21 considered recent work undertaken to establish the long-term mechanical and electrical integrity of the Mk III coaches used in the 200 km/h IC125 diesel high speed trains.

Developments were detailed in presentations by senior engineers from operators First Great Western and East Midlands Trains, as well as fleet owners Angel Trains and Porterbrook Leasing.

Although some HSTs are to be replaced under the Intercity Express Programme, others are expected to continue running on services from London to the West of England. While the power cars have been upgraded, the Mk III trailer coaches have received less compre­hensive refurbishment.

With life-extension likely, it was decided to apply Finite Element Analysis to the Mk III bodyshell, to determine the fatigue life and identify weak points. Forces were measured using an instrumented FGW vehicle and fed into the model, which was run for 60 years.

The work showed that the Mk III body structure is 'a lot better than expected' and can run safely to at least 2035. The modelling had a built-in margin of error, because present-day loads are greater than in the past and the HSTs are operated more intensively.

Only four weld locations were identified as potential problem areas, and these will be monitored during future overhauls. Crack propa­gation analysis was also carried out.

While the power cars have been largely rewired as part of repowering programmes (RG 7.10 p32), much of the cabling in the trailer vehicles remains in its original condition. Accelerated electrical and mechanical life testing by Cobham Technical Services revealed that only the train supply cables and catering equipment wiring needed attention, principally because of their hostile environment. Overall, the Pirelli cable is fit for at least another 25 years of service, assuming the duty cycle remains the same. Some obsolete components, such as junction boxes and circuit breakers, are now being replaced.

Legislation also affects continued service operation, notably the requirement to comply with the Persons of Reduced Mobility TSI from 2020. The seminar was shown the prototype of a new interior door handle, plus a video of a Mk III powered door under test.