The bogies for Desiro DMU UK Class 185

Siemens Transportation Systems (STS), formerly Simmering Graz Pauker (SGP), has almost 150 years experience in the railway business. The product range covered the development and manufacture of locomotives, freight and passenger cars – mainly for the Austrian Federal Railways (ÖBB). In the 1990’s SGP started the development of a high speed bogie for the second and third generation of German high speed train ICE, followed by the development of a high speed tilting bogie.

Since 1996, Siemens Transportation Systems has concentrated all bogie-related activities in its world centre of expertise in Graz. Consequently, all bogies for Siemens Transportation Systems are designed and manufactured in Graz. Due to its annual output of approximately 3,000 bogies, the Graz plant is now one of the largest bogie facilities in the world.

Core competencies and strategies

STS Graz has a fundamental business objective: to be the number one bogie supplier in the world.

Whilst most bogie manufacturing companies are continuously moving towards out-sourcing more of the design, manufacture and assembly of components to sub-suppliers and sharing much of the risks, STS considered carefully what their key competence in the process was and where the major project risks could best be managed and controlled. This was undoubtedly in the technology itself, particularly in the design and manufacture of the bogie frame, especially the welding and construction of the frame.

The years of experience in designing bogies to operate on different railways all over the world, evaluating the running performance and structural strength from test results and tailoring the design software to better represent the practical operation rather than simply theoretical conditions was not readily available in the component supplier base. STS came to the conclusion that they needed to maintain the same quality levels as were expected by Siemens customers whereby, in order to achieve this, the frame design and manufacture needed to be kept ‘in-house’.

The R&D department in Graz currently has more than 150 highly specialised engineers. This department also cooperates closely with various external research institutions. In particular, fruitful cooperation has been established with the Technical University of Graz and the local technical college specialising in railway technology and transportation systems.

Experience of Siemens Bogies in the UK

Before Desiro UK, Siemens, as a company, already had some experience in delivering the Sheffield Trams and Electric Multiple Units to the UK market for the Class 332 (Heathrow Express) and Class 333 (Northern Spirit) vehicles.

But the truly big step was made when Siemens Transportation Systems, together with Angel Trains, agreed to develop an Electric Multiple Unit specifically for the UK market – the Desiro UK. Since 2000, Siemens got different orders for Desiro UK Class 350, Class 360, Class 444 and Class 450, and the development of the SF5000 UK bogie started.

After a very intensive phase of development and production, the first Class 360s for First Great Eastern started their service during the summer of 2003, directly followed by the Class 450s for South West Trains. In 2004, the Class 444 commenced service for South West Trains. In June this year, the Class 350 on West Coast Main Line and the Class 360-2 for Heathrow Connect went into service.

On July 21 2005, the last unit of Class 450 left the Siemens works at Wegberg-Wildenrath. Now most of the Desiro UK trains are in service with a fleet of nearly 1,800 bogies which run more than 125 million miles without any delay caused by the bogies.

Development of the SF5000 DMU UK

These EMU bogies formed the basis for the development of a double-drive bogie for the use with Diesel Multiple Units. 51 of these three-car DMU’s will form the new fleet of First/Keolis new Trans-Pennine Express service and will be the first application of the new bogies. With high power and excellent acceleration they will boost performance on the hilly routes through the Pennines.

However, some challenging tasks had to be mastered. One was the integration of the new drive concept. Each vehicle is driven by its own power unit consisting of a diesel engine and a turbo drive. From this car body-mounted drive, a cardan shaft transfers the power to the bogie’s master and slave axle drives which are connected by an inter-axle cardan shaft.

So now a universal shaft had to run lengthwise through the bogie cutting through transoms and traction links of the EMU design.

Furthermore, the new bogie had to be toughened up for a higher axle load of 18.5 tonnes instead of 16.5 tonnes capability of the EMU bogie. So the trailer bogie had to be strengthened as well and therefore it had to be changed from the EMU design, too.

The new bogie was required to produce low track forces and latest findings on rolling contact fatigue had to be considered by the bogie design.

The gauging strategy for the vehicles was set up by Interfleet Technology which identified the Mk3 coach as primary comparator vehicle. The ride comfort of the new trains should at least be as good as that of a Class 158.

The solution turned out to be a high speed inter-axle cardan shaft atop the plane of the axles, running through a big ‘hole’ in the centre pivot of the bolster. Both the high speed of the universal shaft and the low position of the traction links have beneficial effects in terms of a low wheel load shift in response to the high tractive effort.

Rolling contact fatigue was an issue intensively discussed with the customer and Network Rail. Careful choice of the primary suspension stiffness gives the bogie excellent curving behaviour with low track forces without giving rise to undesirable hunting motions at the same time.

The primary longitudinal suspension stiffness of the leading trailer bogie could have been lowered by 40 per cent. The design should therefore be beneficial in terms of rolling contact fatigue. Finally trailer and motor bogie use different primary suspension stiffness in order to achieve an optimum overall performance.

Excellent ride quality is achieved by means of the air spring system which uses the hollow bolster as a big additional air volume directly connected to both the air bags. Thereby height control is managed by a two point levelling system.

MBS modelling of ride comfort has been performed using a very detailed model of the whole system. A structural model of the car body, including all elastically suspended underfloor equipment, has been developed by Siemens TS Krefeld. The model of the bogies including the axle drives was set up by STS Graz. Care was taken to decouple the body from the bogie as much as possible.

The so-called ‘locked-in movement’ was minimised through careful choice of the suspension parameters for the deflated condition. Thereby it had to be kept in mind not to deteriorate the bogie rotational resistance as well as the lateral ride comfort.

Engineering process

Siemens TS Krefeld provided the bogie specification which defined the key requirements for the Class 185 bogie design. Bogie parameters, simulation models and 3D proE models of the bogies, carbodys and traction units were shared between Siemens TS Krefeld and STS Graz during the design process. This results in well adjusted bogie parameters as damping rates and suspension stiffness and also clear mechanical interfaces.

There is a suite of Railway Group Standards provided by Railway Safety that need to be met so as to ensure no additional risk is brought to the UK rail infrastructure.

The experiences of the Desiro UK EMU projects helped to speed up the overall engineering and acceptance process which is still in progress.

Bogie design strategy

The key bogie design strategy was:

• Meet the UK gauge requirements for the bogie and complete vehicle
• Maximum axle load of 18.5 tonnes
• Maximum speed of 160km/h
• Maximum cant deficiency of 150mm
• Provide a high level of ride quality
• Provide safety against derailment
• Minimise track forces and rolling contact fatigue
• Wheelbase of 2.6m
• Bogie gauge of 1435mm
• Two axle-mounted drives connected by an inter-axle cardan shaft
• Accommodate safety equipment such as AWS and TPWS receivers
• Accommodate TCA receivers for DMUs
• High quality construction utilising a high proportion of robotic welding
• High reliability using proven components wherever possible

Design process

The normal STS design checking and approval process was followed in line with that which has proven to work well in the past. The challenge in the engineering was to adopt the proven design components and subcomponents to the requirements of the British rail system. Most of these requirements are defined in the Railway Group Standard, but some of them very generally; some are just technical common sense based on long-term experience on UK infrastructure.

To establish methods of proving compliance with the Railway Group Standards and state-of-the-art that would be accepted in the UK rail system, previous experience of the EMU projects was absolutely necessary.

Due to STS Graz’s experience and engineering tools, the design of the structural components was based on DIN and UIC standards including a fatigue test of the bogie frame.

Nevertheless, the proof of compliance to RGS and British Standard was demanded.

For other components which are under great attention in the UK, especially small components attached to the bogie frame or the axle box, the requirements are much more severe and detailed than in European standards.

For example, the lifeguard – a device attached to the axle box with the purpose to remove small obstacles from the rail – was designed and tested strictly to the requirements of the Railway Group Standard for the EMU bogie and is identically adopted in the DMU bogie.

Production process

In terms of production, Graz sticks to a clear trend-setting principle for Europe: the welding of bogie frames is a key area of competence at the centre of expertise in Graz. All bogie frames are designed and built entirely in Austria. In order to achieve high productivity, STS Graz relies on a high automation rate provided by state-of-the-art robot-welding facilities. One of the most important factors for the success of the application of this technology is the early involvement of robot welding at the start of the design phase. Compared with former frame designs, in which only up to 30 per cent of welding seams could be processed by robots, today STS Graz has obtained a robot welding percentage of over 70 per cent for the latest optimised frame designs. In other words, sophisticated robot welding means high quality at a competitive low cost level. To highlight the welding statistics, it is worth mentioning that 850km of welding seams are produced at the Graz facility each year.

By machining of the frames from one side, only one clamping is required. Each frame is controlled by a three-dimension check.

Assembly process

Finally, each bogie is assembled in a modern and flexible Assembly Shop where key components that need to be fitted are the wheelsets, including final drives, the brake-systems and the bolster. In order to optimise logistics STS Graz have established a well coordinated team of key suppliers, which arrange pre-assembly and optimise the goods-flow.

Each bogie is adjusted to the individual carbody’s data that it is intended to carry. This is done at pressing rigs where the bogie height and the wheel load deviation are finally checked before delivery.

Validation and approval process for the UK market

In order to gain acceptance to run a new vehicle in the UK, an independent Vehicle Acceptance Body (VAB) must be appointed and also an Independent Assessor which issue certificates to allow the vehicle to operate.

In terms of the Engineering design and the Certificate of Engineering Acceptance, Interfleet Technology were appointed as the VAB and they identified to STS Graz the suite of Railway Group Standards to be met and set up a scrutiny time schedule for reviewing the supplier documentation.

As the bogie by itself involves the most standards for any single vehicle item, involving over 20 Railway Group Standards, STS Graz set-up an internal process in accordance with Siemens TS Erlangen to more easily manage and control the supply of acceptance documentation both from suppliers and also to the VAB. This helped ensure that it was easier to demonstrate to the VAB that all of the relevant requirements within the standards had been met and also so that there was a traceable route to compliance.

The validation process also involves testing to ensure that key requirements are met.

One of the first bogie frames out of series production is currently UIC fatigue tested at the structural strength laboratories of Magna Powertrain in Steyr.

When the first trains come from the Krefeld works to the Siemens Test Centre at Wegberg-Wildenrath (PCW) for commissioning, the compulsory static type tests, such as wheel unloading, bogie rotational resistance and sway test, will be performed.

A first set of on-track tests up to a maximum speed of 160km/h and up to cant deficiency values of 275mm have already been performed successfully. The on-track test results were evaluated according to European standard UIC 518 as well as according to the relevant Railway Group Standards.

The bogies and vehicles behaved very well as ride comfort was excellent knowing that the conditions in the PCW are laboratory-like.

The next stage to come is the real on-track type tests in the UK on the hilly routes of the Trans-Pennine network.
In addition to these tests, designated for VAB approval, a separate test series will be conducted in order to study the vehicle track interaction in line with a research programme to investigate rolling contact fatigue.

Future developments

One could think of an application of the bogie for UIC countries as there are only a few minor changes necessary. In the bogie design, the UIC requirements were considered as well, installation space for UIC antennas are available.