E-mobility: A little locomotive with a lot of power

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Emission-free, economical and as powerful as a conventional drive – with its newly-developed electric locomotive for trackless railways, Sightseeing Trains Rügen GmbH is offering an innovative product for the transport of tourists, and is thus right on trend. In order to connect the drive line in the locomotive with the electric motor, the company relies on the robust and powerful ROBA-DS disk pack coupling by mayr power transmission, which is able to permanently withstand the high loads.

Oslo, Madrid, Copenhagen, London or Paris – in the attempt to achieve a higher urban quality of life and environmental protection, an increasing number of European metropolises are banning cars from their inner city areas. The varying concepts extend from the exclusion of conventional diesel vehicles via a complete travel prohibition for private cars right up to the creation of an infrastructure intended to render motorised individual traffic completely superfluous. Like the Deutsche Post, which has changed its vehicle fleet in its medium-term planning to environmentally friendly electric cars, an increasing number of companies are also searching for alternative solutions. And therefore Sightseeing Trains Rügen GmbH offers with its high-performance electric locomotive for trackless railways an innovative, emission-free product for the transportation of tourists.

Stefan Krüger, Head of Production and Development at the Sightseeing Trains Rügen GmbH in Binz explains: “Our electric locomotive isn’t just used for example where inner cities have to be ‘emission-free’, but also in natural reserves in which traffic is otherwise prohibited.” The electric locomotive thus opens up, for example, new possibilities where traffic prohibitions would otherwise exclude families with small children or people who have problems walking, for example.

Stefan Krüger adds: “Using our electric locomotive, a larger circle of people can take advantage of the new possibilities opened up to them in natural reserves located in mountainous regions.” The electric locomotive is outstandingly powerful in terms of torque: the power and range accord with a conventional drive. Stefan says: “It can therefore easily manage even difficult sections with up to 24 per cent gradients”.

In order to connect the drive line with the electric motor in the locomotive, the Binz-based trackless railway manufactory relies on the robust and high-performance ROBA-DS disk pack coupling by mayr power transmission. This coupling compensates for shaft misalignments and is able to continuously withstand the high loads placed upon it.

Fascinating technology

As a subsidiary of the Jagdschlossexpress and Ausflugsfahrten GmbH, Sightseeing Trains Rügen GmbH can rely on years of experience collected on trackless railways. Regarding the philosophy of the company, Stefan Krüger says: “In the meantime, we don’t just operate the railways, but also produce them ourselves. In this way, we can adapt to specific customer requirements, as every section has its own challenges, and we want to be able to find a permanent solution for our customers. The electric locomotive is currently our favourite child. Everywhere we go, people initially regard this product with scepticism, but after only a short time, they are completely converted”.

This is due to the unique technology and the high performance capacity: the electric locomotive with its lithium-iron phosphate battery has a range of up to 150km and convinces through its tractive power – with a torque of 850Nm under continuous load. Stefan Krüger explains: “The locomotive doesn’t let us see the loads placed upon it: it continues to run soundlessly.” The maintenance of the electric locomotive in comparison to conventional diesel engines totals approximately 35 per cent, meaning that customers can therefore save up to two-thirds of the costs. The electric locomotive is thus not only economical, but also maintenance friendly: it is sufficient to charge the locomotive overnight. The charging duration after complete discharge is approximately 4 hours.

For the connection of the electric motor to the drive line, a high-performance, patented ROBA-DS disk pack coupling by mayr power transmission is used. This coupling transmits the torque backlash-free and with exceptionally high torque rigidity and compensates for radial, axial and angular misalignments. It thus ensures accurate torque transmission and is robust, reliable and temperature-resistant. In addition, the ROBA-DS shaft coupling is wear-free and thus reduces the necessary maintenance effort to a minimum. Stefan Krüger says: “Here we require a coupling which has a consistent fatigue strength and which is able to transmit the high torques, in particular during peak loads. In addition, the axial displacement compensation is important; the coupling is able to cope with production tolerances. In the case of the ROBA-DS, the overall package convinced us – meaning the service and the price in addition to the technology”.

Performance density combined with backlash-free function

On couplings, too, a high performance density plays an increasingly important role today. High performance density means small outer diameters, reduced weight and low mass moments of inertia. In this way, load changes can take place more quickly, and the drive is able to accelerate and slow down within a shorter time. Due to the lower mass to be accelerated, the operating costs are also reduced and the handling and installation of the coupling is made easier. In machines with compact dimensions in which little installation space is available, small dimensions are also advantageous. In addition, a compact construction with high performance density can also save on raw materials during the manufacture of the coupling.

In the case of the ROBA-DS disk pack couplings by mayr power transmission, the nominal torques stated in the catalogue can be used without any limitations whatsoever. A reduction in the nominal torque due to misalignments, load spectrum or balance requirements is not required. The couplings are compact and small with high performance density. In the case of providers who have to take misalignments and alternating torques into account in the dimensioning, a larger coupling frequently has to be selected with the same nominal torque and the same speed. The ROBA-DS disk pack couplings simultaneously unite high performance density with absolute backlash-free function, as design details such as the blasting of the disks and the use of specially shaped collar bushings ensure a backlash-free flow of force with excellent force flow density between the input and output. The ROBA-DS disk pack couplings transfer the torques up to the nominal torque completely backlash-free and with a constantly high torsional rigidity. The stated shaft misalignments can be utilised to 100 per cent in total without influencing the transmittable torque.

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