The prosaic rail freight wagon rarely features in the pages of Rail Engineer. With so many stories about all aspects of railway engineering, this is perhaps not surprising. But rail freight is important. It accounts for 11% of UK rail train revenue and has the potential to take goods off the roads, to save fuel and CO2 emissions.
Yet, in Europe, rail freight has stagnated and accounts for only 10% of freight transport. This concerns the European Commission (EC) which has an objective that 30% of road freight movements over 300km should shift to other modes by 2030.
To achieve this, an EC Regulation came into force in 2010 requiring dedicated freight corridors to provide seamless rail freight services. Another European initiative is the Sustainable Freight Railway (SUSTRAIL). This is a €9.4 million four-year project, launched in 2011, to design a freight vehicle track system with improved reliability at reduced cost. It was part of the seventh Framework Programme for EU research (FP7) for which the EC contributed €6.6 million.
Whole system approach
SUSTRAIL aims to increase rail freight performance through a whole system approach which involves a number of work packages. The current system was benchmarked (WP1) and duty requirements established (WP2).
Then two parallel but linked packages considered the freight train of the future (WP3) and sustainable track (WP4), after which a business case (WP5) was developed and the new vehicle and track systems were tested (WP6). Thirty-one organisations in twelve countries shared the work for which the project coordinator was Consorzio Train, an Italian consortium of rail research institutions. UK participants were Network Rail (technical coordinator), Tata Steel and the Universities of Newcastle, Leeds, Sheffield and Huddersfield.
Initial benchmarking involved Network Rail and the Universities of Leeds and Newcastle. This analysed three selected freight routes in Bulgaria, Spain and Britain (Southampton and Felixstowe to Warrington).
The capacity, vehicle types and infrastructure characteristics of these routes were assessed to determine duty requirements from which key performance requirements were derived. For the SUSTRAIL vehicle, these were a 20% reduction in energy consumption, reduced track damage with lateral forces reduced by 50%, improved braking with wheel-slide protection, running up to 140km/h (for 17 tonne axle weight) and less noise.
The University of Huddersfield’s Institute of Railway Research led WP3, the development of the SUSTRAIL freight vehicle. Its director, Professor Simon Iwnicki, commented that it is understandable that freight vehicle manufacturers are a conservative lot as their vehicles operate in a harsh environment with practical maintenance and operational constraints. Change is expensive and its benefits are not always easy to demonstrate.
This was a key factor in the WP3 technology review that considered availability for mass production, reliability and maintainability and concluded that innovations were required for running gear, wheelsets, braking systems, body and bogie structure and condition monitoring.
Unlike passenger vehicles, freight vehicle suspensions experience a large difference between tare and laden weight. The standard Y25 bogie accommodates this by nested primary suspension coil springs with an inner spring that engages progressively as the wagonload increases.
Each axlebox has a single inclined ‘Lenoir link’ that transfers some of the vertical load onto an axle box friction face to provide vertical and lateral damping proportional to vehicle weight. However, this gives a high longitudinal stiffness once its clearance is exceeded.
Simon explained that, after considering various options, it was felt that a double Lenoir link suspension, allowing additional freedom of movement, was the best way of lowering longitudinal stiffness.
The optimisation of the double Lenoir link suspension was the result of several university partners undertaking computer simulations with key parameters varied to assess their effect on performance. These included the vertical coil stiffness, Lenoir link angle and length, friction coefficient of the sliding face and bump stop vertical clearance.
However, these simulations also showed the double link suspension to have a lower critical speed than that of the single link. To control stability, an interaxle linkage was required which also provides passive steering.
Further simulations determined the optimum lateral stiffness characteristics of this linkage and showed that longitudinal stiffness was not required, thus simplifying the linkage design. These also showed that the optimised double Lenoir link and linkage had a critical speed of over 140km/h.
Work to develop this suspension was undertaken by the University of Huddersfield, Russia’s St Petersburg State Transport University, the KTH Royal Institute of Technology in Sweden and REMARUL Engineering of Romania.
Vehicle dynamic simulations used track data from typical UK routes together with new and worn wheel and rail profiles. They provided assessments of ride performance and of track damage such as T gamma (the contact patch frictional forces that causes RCF – rolling contact fatigue), along with track vertical and lateral forces.
These simulations showed that the SUSTRAIL vehicle met the EN14363 ride standard and had a stable and track friendly bogie with particularly low lateral forces.
Italian rail wheel manufacturer Lucchini provided innovative wheelsets developed with assistance from the Polytechnic University of Milan. They were designed for a 25 tonne axle load and 160km/h running and had an optimised wheel web to reduce mass and noise. Lucchini’s Syope® viscoelastic polymer noise absorption coating was applied to the wheel web, giving a further noise reduction.
The axle was also coated by LURSAK®, a 4.5mm thick reinforced epoxy resin that offers protection against corrosion and impact. This was tested by cannon firing ballast stones at up to 390km/h. Further tests showed that cracks did not propagate from the light damage (depth 0.5 mm) sustained by coated axles from such high impact tests after a simulated million kilometres running.
However, cracks did propagate from impact damage on uncoated axles. Hence, this coating reduces the risk of failed axles and could potentially reduce maintenance costs by extending ultrasonic testing frequencies.
With no power supply, freight trains cannot use modern, electronically controlled braking systems. Hence, to meet the requirement for wheel- slide protection and load-controlled braking, energy harvesting was needed. This is provided by an axle- mounted generator with a battery and power management system.
Wagon braking is controlled by an EDS 300 hybrid brake system produced by Keschwari Electronic Systems (KES GmbH). This unit has both an electronic and backup pneumatic distributor valve and adjusts braking according to load.
Its wheel-slide protection uses speed sensors on each axle and electronically controlled dump valves. The unit also has built-in diagnostics and a data logger.
Real-time condition monitoring also required a vehicle power supply. On the SUSTRAIL vehicle, the KES 300 unit provides braking data whilst MERMEC supplied hotbox temperature sensors and accelerometers for derailment and vehicle stability monitoring.
The Polytechnic University of Milan is also developing a real-time cracked axle detection methodology. To provide real-time condition monitoring, wireless data transfer was also validated as part of the project.
To save energy and reduce track damage, Consorzio Train and the University of Newcastle undertook a structural design review of the vehicle body and bogie that was validated by finite element analysis. This showed that, for example, there could be an 18% reduction in the bogie frame lateral beam weight if web thickness, flange width and thickness were reduced and higher tensile steel was used.
Similarly, the use of such steel whilst changing the section and dimensions of the lateral wagon side beam could reduce its weight by 40%. The high strength steel used for lightweighting was RQT®701 by Tata Steel.
Having developed the required innovations, the SUSTRAIL vehicle with its modified Y25 bogies was constructed at the REMARUL workshops in Romania. In May, it was tested on the Romanian Railway Authority’s testing centre at Faurei that has a 13.7 kilometre ring with a maximum speed of 200km/h.
This included running and braking tests of the loaded vehicle at 140km/h. Indeed the vehicle was perfectly stable at 150km/h, the highest speed attainable with the test locomotive. As a benchmark, tests were also undertaken on a conventional wagon for comparison with the SUSTRAIL vehicle.
More traffic, less deterioration
While the SUSTRAIL vehicle work was undertaken in close co-operation with Network Rail, the company also led WP4 to assess how the railway infrastructure could accommodate more traffic with reduced track deterioration.
This included the development of performance-based design principles for resilient track based on a failure mode and effects analysis. However, this was recognised to be strongly dependant on the quality and details of the input to this analysis.
Specific innovations considered by WP4 included multifunction geotextiles and wayside monitoring. Geotextiles which incorporated optical fibres to monitor movement were installed in an embankment near Chemnitz, Germany in 2014 and were proven not to be susceptible to damage by the heavy machinery used on the site.
Wayside monitoring stations installed on several routes in Sweden measure vertical and lateral forces per wheel, angle-of-attack and wheel defects. The Luleå Railway Research Centre evaluated this data to identify specific vehicle defects and propose vehicle service limits.
The SUSTRAIL track innovations are to be taken forward by Network Rail. The final innovation considered was the installation of premium rail steels on curves less than 1,200 metres. The results from this were fed into the business case and outlined below.
Making the case
The pan-European SUSTRAIL initiative has produced a rail freight vehicle with the potential for large cost and energy savings. However, realising these benefits is perhaps more of a challenge. Hence, the SUSTRAIL project includes a further work package to make the business case for its innovations. This assessed life cycle costs over a 30-year period for three scenarios:
1) the SUSTRAIL vehicle only;
2) the vehicle plus Premium Rail Steel on curves less than 1,200 metres;
3) vehicle, premium rails on curves and 140km/h running.
The business case included a RAMS (Reliability, Availability, Maintainability and Safety) analysis and assessed the benefits against the requirements of the three selected freight routes.
This work concluded that, on curves at current speeds, the use of premium rails (such as HP335 and MHH375 by Tata Steel) offers a 61% reduction in life cycle costs. It also showed that, over a 30-year period, a SUSTRAIL vehicle would have a 63% reduction in vehicle maintenance costs and its availability would be 99% compared with 95% for the benchmark wagon.
However, with the SUSTRAIL vehicle costing up to 75% more than a conventional wagon, its payback is 23 years. This assessment does not take account of its reduced track damage that is generally not the owner’s problem.
The business case considers that the SUSTRAIL vehicle needs a payback period under eight years if it is to be adopted by industry. It considers this can be done by reducing capital costs and introducing track access charges that reward track-friendly vehicles.
In April last year, Network Rail changed its freight access charge regime to do just this rather than to charge based on axle load. Now, a complex formula is applied to each vehicle type to assess vertical and lateral track forces as well as the T gamma that causes RCF. Simon advised that Sweden is the only other European country with a similar access-charging regime. Clearly, this is an area where European harmonisation is needed.
SUSTRAIL has proved to be a worthwhile initiative in which Network Rail and British Universities have played a major role. The project has considered the engineering of both track and rail freight vehicles from first principles to deliver significant improvements. However, some of these improvements may not be realised unless track access charges are changed to provide the required incentive. This requires the rest of Europe to follow Network Rail’s example of encouraging track- friendly bogies.