RAIL INDUSTRY FOCUS


DEVELOPING NEW COMPONENTS FOR EXISTING ROLLING STOCK


Rail locomotives provide a vital transportation service for passengers and freight across the world. Working round- the-clock, they are expected to deliver unrivalled reliability


R


ail networks endeavour to maintain an excellent safety record through both regular


planned maintenance, and adherence to rigorous standards and repair specifications. Any supplier to the industry must pass the scrutiny of independent inspections that examine the entire supply chain of materials, repair techniques, facilities and training. For manufacturers, developing modernisation


packages is a very important part of the support they offer to operators. These programmes can take advantage of materials and manufacturing techniques that have been developed since the locomotives were launched. For the operators, these updates ensure continued reliability and extended service life for their assets. However, these programmes require


considerable planning and time for product design, development and testing. As a result, the relationships between the OEM, the rail operator and the parts manufacturer are very important. In one example, a rail OEM reached out to


Stromag, Nuttall Gear and Guardian Couplings, all of which are brands of Altra Industrial Motion Corp., for support in supplying specialist flexible and gear couplings. Over the last three years, the OEM’s design and engineering team has been working on new


coupling solutions for both the main drive side and the power-take-off (PTO) of the diesel engine. One coupling is to be positioned between the diesel engine and the gearbox, another between the gearbox and the exciter and blower assembly, and a third connecting the engine PTO to the air compressor.


DESIGN CHALLENGES Each application has several design challenges, including torsional vibration and the physical space available for the components. During the three-year design process, multiple coupling options were reviewed to determine which would best address these challenges. The chosen designs would be recommended for a potential population of over 10,000 locomotives. Within this fleet, the diesel engines produce


the input parameters for the design team to work with. Stromag did the torsional vibrational analysis (TVA), recreating the complete drivetrain and establishing that the values surrounding the engine to gearbox coupling would present a considerable challenge. It proved to be impossible to eliminate the root cause, which left another option – to mitigate the effects by adding weight to the flywheel. The suggestion was to increase the mass moment of inertia of the flywheel (which was originally 25kgm2


) to 120 kgm2 .


PROVING RELIABILITY Having reduced the torsional vibration, Stromag started to develop a design based on its


The Stromag Vector coupling


Vector coupling which has high torque transmission capabilities and very compact dimensions. At the same time, Nuttall Gear and


Guardian Couplings developed a complete package of parts to integrate with the existing components with easy installation, even in the confined space. Components for a typical modernisation


up to 3,300hp (2,500kW) at 900rpm and are mounted on isolation mounts, while the gearbox and alternator are hard-mounted to the chassis. This can mean lateral movement of ±3mm laterally and ±4mm vertically. As part of the design process, the OEM provided


programme are expected to have a 20-year service life with an annual operating time of 8,760 hours. Above all, they must prove their robust design and ability to deliver continuous reliable service in an arduous application.


Stromag www.stromag.com Rail locomotives provide a


vital transportation service for both passengers and freight across the world. (Image provided by Stromag; Source: AdobeStock 4937201)


/ DESIGNSOLUTIONS


DESIGN SOLUTIONS | JUNE 2021 37


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