32 | the rail engineer | may 2012
rolling stock/depots
writer
Nigel
Wordsworth month, the rail engineer visited L ast Graz, the historic capital of Styria and
Welding up bogie frames.
Austria’s second city, for the launch of the new SF7000 bogie which Siemens intends to use on the new Desiro City trains that it will shortly be building for the Thameslink programme. During that visit, Siemens’ engineers were keen to show how modern bogies are manufactured in a factory which can turn out 4,000 a year. Dating from the 1850’s, when it commenced making railway wagons and then, more recently, carriages, Siemens converted its earlier 26% holding in the factory to 100% in 2001. Since then, the Graz plant has concentrated purely on bogie design and manufacture and is now Siemens’ Centre of Excellence for bogies, where they make bogies for everything from trams to high speed trains. Design is carried out in the same way as for any other mechanical assembly these days. A team of experienced engineers, working on CAD screens and using finite element and other techniques, come up with new ideas and modifications to earlier designs. These designs are then tested, in computer simulations so that changes can be made before an actual prototype is even manufactured.
Building Bogies Design Development Diemo Wojik, Head of Bogie Projects, explained how the design process has progressed in the last ten years. When Siemens established the Graz centre in 2001, they were already using computer simulation techniques as part of the design process. Completed designs were subjected to a multitude of simulated running conditions to see how they would react in operation - under load, under braking and on good and bad track. It was important to make sure that bogies were stable, and didn’t pass unwelcome movement onto the passenger carriage to which they were mounted. In 2002, strength analysis was added to the computer models, and in 2005 a routine was introduced to help optimise the acoustic characteristics of the bogie. Most of the noise emitted by a running train comes from
the wheels and bogies, and increasing public sensitivity to this made the ability to design a quiet bogie essential. By 2007, Siemens was developing routines to design with maintenance in mind. What were the operating life expectancies of the various components, and could this be increased? Whole life costs were becoming important
benchmarks for customers, and a few extra Euros spent on a design or a component that reduced maintenance in the long term were now a good investment for operators. A programme to design for weight commenced in 2007. Weight had always been an important element as heavy bogies give high axle loads and thereby damage track more easily. However, now lightness was increasingly important as it also has a bearing on fuel economy. So light bogies, underneath aluminium-bodied trains, were becoming the norm in metro applications. The new programme examined the weight of everything, from frames to axles and even brackets, in a drive to get as much weight reliably out of the product as possible. 2012’s programme takes the concept of designing for maintenance a step further. “Bogie Monitoring” fits the bogie with a number of sensors measuring movements, resistance to movement, and other variables to establish the condition of the bogie and its components. This means the bogie can self-diagnose any faults, and report back through the train’s control system, so maintenance engineers are notified when essential work is needed, or can postpone routine maintenance when it is not, so saving cost.
All this design and development work is undertaken by the 210 engineers at Graz before a new bogie is even released for