Engineers at the Technical University of Chemnitz, Germany have developed a lightweight adapter coupling in fibre composite construction which can be used for towing and shunting trains. The Chemnitz engineers’ brainwave was to use carbon fibre reinforced plastic (cfrp) instead of steel which means they save more than half the weight.
Adapter coupling in fibre composite (photo: TU Chemnitz)
The adapter coupling for rail vehicles developed at the laboratories of the Institute for Lightweight Construction at the University of Chemnitz weighs in at 19kg. A weight of more than double this is usual in the trade, that is 42kg. The Chemnitz engineers came up with the inspired idea of using carbon fibre reinforced plastic instead of steel. Partnering them in the development project were Messrs Voith Turbo Scharfenberg, Salzgitter, Germany and East-4D, Dresden, Germany.
The adapter coupling in fibre composite construction can be used for towing and shunting trains. (photo: TU Chemnitz)
The new development is based on the Scharfenberg coupling, a product made by their project partner, Voith. This has been used in railway applications ever since 1903. “The Scharfenberg coupling is an international market leader today. In Europe almost all state railways and many of the suburban train systems and metros are equipped with Scharfenberg coupling systems,” says Holger Seidlitz, Scientific Assistant of Lightweight Construction and Plastics Technology at the TU Chemnitz. Although the operating principle for the couplings is always the same there are different versions to suit the various types of train and these are not compatible with one another. In order to make coupling possible even where the types and heights of couplings are different so-called adapter couplings are used. These act as adapters and are especially necessary when it comes to shunting and towing. “When in towing or in shunting mode, operating personnel often need to mount these adapter couplings on the train for a short time only – and the operation can only be carried out manually. This means that the adapter couplings need to be lightweight but nevertheless capable of withstanding the high load stresses that occur when pulling entire trains,” explains Prof Dr Lothar Kroll, Head of the Chair of Lightweight Construction and Plastics Technology.
Face plate, coupling unit, pull loop and traction engine in CFRP
The potential for weight savings using the steel construction approach which has been the norm hitherto is reported to be largely exhausted, therefore a new approach is called for. The Chemnitz coupling is manufactured predominantly from lightweight, carbon fibre reinforced plastic. This material may be more expensive than steel but “up to now, because of Health & Safety constraints, two persons have been needed if the steel variant is used. Therefore, during shunting, for example, two operatives must be on the loco all the time. By contrast, with the lightweight coupling, only one person is required and this means that cost savings can be implemented,” explains Seidlitz.
The Head of the Institute for Lightweight Construction at the Technical University of Chemnitz, Prof Dr Lothar Kroll (right), discusses the design of the adapter coupling with colleagues Lars Ulke-Winter and Holger Seidlitz (from left). (photo: TU Chemnitz/Mario Steinebach)
Over the past 100 years and more that the steel adapter couplings have been used, their design has consistently improved. One of their attributes is high strength, but at the same time they are compact; the specifications governing the amount of installation space that they are permitted to take up are strict. This factor meant that the bar for the lightweight construction coupling had to be located at a high level. “Even the high tensile and compressive forces meant the need for new approaches and solutions“ said scientific assistant Lars Ulke-Winter. The adapter coupling consists of a face plate at one end that is placed up against the coupling on the train to be pulled. The coupling, which is hooked up to the traction engine doing the pulling, terminates in a pull loop. There is an additional safety catch which can also be linked up with the drag hook on the towing engine.
High tensile and compressive forces
The engineers designed all these components from CFRP. In so doing, the scientists have placed particular emphasis on the arrangement of the reinforcing carbon fibres in the loop, because it is there that the tensile and compressive forces have the greatest effect. In addition they have shown, by means of calculations, that this loop must not be less than a specific minimum diameter and how wide it is will have significant impact on the loads it is able to withstand. “In order to be able to mount the coupling on a large number of different hooks, narrow tolerances need to be applied as far as the geometry of the loops is concerned. This is why we have developed an “insert”, a component that is mounted underneath the loop and which provides it with additional reinforcement without contravening the space requirements,” Seidlitz explains. This insert is made from titanium which is a comparatively lightweight metal. Titanium is also used for other smaller components such as the connections for the brake pneumatics. The hybrid construction used in the lightweight coupling and incorporating fibre composites and metals also forms part of the Excellence Cluster “Merge technology fusion for multi-functional lightweight structures” which is being promoted at the TU Chemnitz under the Federal Excellence Initiative.
A prototype of the adapter coupling was handed over to Dr Rüdiger Grube of the Railway Managing Board by TU Rector Prof Dr Arnold van Zyl (front left) on the occasion of his visit to Chemnitz in June 2012. With this coupling, which can be operated by one person on their own, it is also possible to shunt ICE trains. (photo: TU Chemnitz/Sven Gleisberg)
The individual components and complete demonstration models for the new CFRP adapter coupling have been subjected to load tests. The field trials took place at the Tüv Süd Industrie Service centre in Görlitz, Germany. The CFRP adapter coupling is said to meet extreme requirements and is currently being prepared for its market launch. The development engineers at the TU Chemnitz, Voith Turbo Scharfenberg and East-4D have been lauded for their development work with the “Composite Innovations Award 2012”.
www.tu-chemnitz.de
