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the rail engineer • April 2014
Stuart Marsh
I
t probably goes without saying that it’s not a good idea for trains to get too close to infrastructure along the railway, let alone to other trains. In days gone by, calculating clearances was a case of wielding a tape measure ... and it didn’t always work. Some might recall an incident when King Class locomotive 6024 ‘King Edward I’ lost its safety valves when they struck Bishops Bridge, Paddington after the track had been lifted. It was a long time ago, but yes, I’m afraid your writer is old enough to remember this. Nowadays, it’s all rather different of course, with regularly-updated laser-scanning and modern surveying techniques being the norm. But how can all that data be managed effectively?
Plethora of data On today’s high performance network with the TOCs pushing for increased capacity by means of larger and faster vehicles, the calculation of clearances between rail vehicles, other rail vehicles and infrastructure has never been more crucial. It sounds simple, but it isn’t, as the kinematic envelope of a moving rail vehicle can be quite different to its static envelope. Balfour Beatty Rail is just releasing a new version of its ClearRoute™ route assessment and clearance calculation software tool which neatly brings together a national infrastructure gauging database and a national vehicle database. Marketed as ClearRoute™2, the new software carries out gauging processes by comparing any permutation of structure gauging, measured infrastructure, static vehicle profiles and dynamic vehicle profiles. The results are then automatically compared with the applicable standards in order to define clearances. This new package provides greater functionality, improved operating speed and a greatly improved and more intuitive user interface.
Vehicle dynamics Databases built into ClearRoute 2 contain profiles and performance data for the majority of rail vehicles that run within the UK. The way in which a rail vehicle behaves when in motion can be complex and this depends not only on the vehicle but also on the track and the interaction between the two.
Vehicle models contain the information required to accurately calculate a vehicle swept envelope at a particular infrastructure location. This includes vehicle geometry, cross sections and predicted movement data tables. Predicting the movements due to suspension flexibility is done using dynamic simulation software for example Vampire® from DeltaRail. Track parameters are also important, including the radius of curvature, the degree of cant and the track ‘fixity’ (the degree of movement in the trackbetween maintenance cycles). Balfour Beatty Rail manages the vehicle library and releases updates on a three-monthly basis.
Infrastructure ClearRoute 2 contains an additional database of infrastructure information which is based on structure measurements and the associated track geometry and track spacing. The data may be gathered by manual means, by portable laser gauging such as LaserSweep™, or by infrastructure recording vehicles including the Network Rail structure gauging train (SGT) which carries Balfour Beatty Rail laser triangulation equipment.