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Modifications are being carried out on Hitachi’s Olympic bullet trains because of an unknown problem affecting their ride performance.
Engineers are modifying the high-speed Class 395 Javelin trains following reports from passengers that carriages are wobbling too much as they pass through tunnels.
The trains, which run between Ashford in Kent and London’s King’s Cross, will take spectators to and from King’s Cross to the Olympic Games at Stratford in 2012.
The modification work, which is taking place during routine maintenance, involves modifying the yaw dampers on the trains. The dampers, which sit on the bogie, are transverse-mounted shock absorbers used to prevent railcars swaying excessively from side to side. The resilient bush on the yaw damper is being changed to a stiffer bush to improve the performance of the damper.
Ten of the 29 trains have been modified and the rest will be worked on over the next few months.
Alistair Dormer, managing director of Hitachi Rail Europe, said: “The ride performance of the unit in the tunnel could be better. What we are seeing is a slight deterioration in the tunnels - a very small sensation of sideways movement.
“We’re combating it through a minor modification. We’re viewing it as continuous improvement of the product.”
Dormer said Hitachi does not know what is causing the problem, but is conducting an investigation with Network Rail to monitor the performance of the trains. This involves analysing the wheel and rail interface behaviour of the track in the tunnels.
“We are monitoring how the train is performing over different types of track to see whether anything else needs to be done,” he said.
“We’re not just sitting back and assuming that everything is perfect. We are looking to improve all the time.”