by Adrian-Liviu Dorofte

The new Mercedes-Benz Citaro in detail: Comprehensive testing ensures supreme quality


Stuttgart/Mannheim, Germany, May 20, 2011

Teams from all departments – from Development to Production to Sales & Marketing to After Sales – worked in close collaboration with one another during the development of the new Citaro. Their joint objective was to achieve supreme quality, in order to best prepare the new Citaro for the rigours of urban and rural regular-service operation

State-of-the-art design and development methods

The top quality achieved in the series production of the new Citaro is rooted in state-of-the-art development methods, such as HiL (Hardware in the Loop) and CAE (Computer-Aided Engineering). Examples for this type of quality assurance include component strength analyses, evaluation of vehicle vibrations and crash test simulations – all this and more is carried out by computer.
All safety-relevant components were analysed using the FMEA method in the early phases of development. The failure mode and effects analysis seeks to anticipate potential problems and prevent them. To put it in simple terms: the developers check everything that might go wrong in advance and undertake appropriate measures, thereby eliminating faults before they even occur. The development findings were backed up by numerous computer-aided calculations for components and assemblies as well as for the vehicle as a whole.

A laboratory bus examines production

The troubleshooting carried out during development of the new Citaro was not a purely theoretical affair, however: all the main body segments were scrutinised in rough form during the development phase when the prototype was built. It was therefore possible to examine potential cable chafing points, component accessibility or other critical issues directly on the vehicle, right from the outset.

The very first prototype of the new Citaro was already assembled on the production line so that any problems in the manufacturing process could be remedied immediately. Besides this, a special “laboratory bus” passed through each production station several times. Using this procedure, Mercedes-Benz was able to train the production workers and, at the same time, identify critical processes. Exact prototype protocols were kept to log all change requests for the bodyshop, assembly and testing, for instance. Workshops were held at regular intervals to resolve any flaws and document the progress in detail.

Testing under the toughest conditions on test rigs and the road

Individual components and assemblies, as well as complete buses were put to the test under the toughest conditions. The new doors, for example, were subject to endurance testing on test rigs, when they had to complete one million load cycles - the equivalent of a bus's entire service life – without any damage. Tests with seven carefully camouflaged prototypes were then conducted at the proving ground as well as on the road. Rigorous testing was also carried out in extreme climatic conditions, meaning that the new Citaro has already faced both the bitter cold of the Scandinavian winter and the searing summer heat in Spain and Turkey. The new urban bus furthermore had to prove its mettle in rough-road and endurance testing, which included a circuit of specially selected poor roads in remote regions of Turkey.

Successfully completed crash tests and pendulum impact tests in accordance with the ECE R29 standard for coaches, as well as rollover calculations based on the future ECE R66/01 standard, are testimony to the design’s high standard of safety.

The extensive programme of testing concludes this spring when new Mercedes-Benz Citaro buses will commence customer trials in everyday regular-service operation before series production gets underway.

The new Citaro: launching with rigid and articulated buses

Mercedes-Benz will be phasing in the high-volume model versions of the new Citaro over the course of 2011. The focus will be on urban and rural variants with a length of 12 metres and 2 or 3 doors, as well as the urban and rural versions of the articulated Citaro bus with 3 or 4 doors. The buses are driven by horizontal or vertical diesel engines from the OM 906 and OM 457 series in the familiar versions and power ratings. Further variants of the new Citaro will follow in 2012. The new Mercedes-Benz Citaro has been future-proofed, with all installation spaces already prepared for the future Euro VI emissions standard. The corresponding drive units will be launched at a later time. This progressive switch to the new model generation guarantees thorough testing of all versions, high quality, plus a continuous supply of vehicles without any disruption to customer deliveries. The complete range of new Mercedes-Benz Citaro models, including all rigid and articulated variants, the low-entry Citaro LE as well as the CapaCity, is due to become available over the course of 2012/2013.

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