Cobra (tram)
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The Cobra Tram is Zurich's newest tram type and first low floor tram. It is currently only running on a limited number of lines (4, 11, 9, 14) alongside the other tram models, although further rollout is planned for the coming years.
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[edit] History
[edit] Initial concept
In 1992, a consortium of Swiss rolling stock manufacturers proposed a new design of low-floor articulated tram. The design was targeted for Zürich and Basel, but it was hoped other orders might also be won.
The design is based on short body segments, with four-wheel trucks under every second segment. The other segments are floating, i.e. without wheels but supported by adjacent segments. The wheel pairs of these trucks are not connected by axles but pivot individually and are steered into curves. This, it was hoped, would reduce wear and noise and also increase passenger comfort. Also, the lack of axles permits a low floor throughout the vehicle. The wheel boxes themselves are hidden under seats, as are the motors.
This running gear would have been designed and manufactured by SIG. The electrical equipment would have been supplied by ABB and the tram body by Schindler, who proposed to manufacture it from a synthetic material.
[edit] Prototype
In order to convince potential buyers and gain experience with the design, the manufacturing consortium set about creating a prototype. For this, Bern tram 401 was purchased. Its running gear was replaced and a new centre section was inserted. The prototype, which was numbered 3000, underwent extensive testing in both Zürich and Basel. It also visited Augsburg and Helsinki for promotional purposes. The unit was ultimately scrapped in Basel.
[edit] Delays and Modifications
Following various changes of policy in Zürich and Basel, no immediate orders were fortcoming. Meanwhile, the manufacturing consortium underwent numerous changes due to acquisitions and mergers within the industry. The sections of ABB and Schindler concerned with the Cobra design ultimately became part of Bombardier, with SIG ultimately becoming part of Alstom. Changes in management focus and some loss of expertise through downsizing activities also affected the design. Following concerns over the suitability of the polymer construction, this was replaced by an aluminium design.
Basel was lost as potential customer when this city opted for the Combino design by Siemens. The Cobra consortium, however, won an order to supply 6 prototypes to Zürich.
[edit] Prototypes in Zürich
These 6 prototypes (3001-3006) for the VBZ began test operations in Zurich in 2001. These are five-section versions of the design. However these were withdrawn from operation soon afterwards due to cracks appearing in the drive mechanisms. There were also concerns about the noise levels both within and outside the new trams, leading to addition of noise reduction measures. Since 2002, six Cobra trams have been operating on lines 4 and 9.
Following the Combino crisis, the design of Cobra was also reassessed, and it was found necessary to modify the construction yet again. It was also decided to add air-conditioning.
[edit] Production units
VBZ finally confirmed an order for 68 production units (3007-3074). Delivery of thse began in 2005 and should be complete by 2010, replacing all rolling stock that is pre-Tram 2000. VBZ furthermore has an option to order up to 35 additional units. To what extent this will be exercised has yet to be decided. Additional trams will be needed for new services such as Tram Zürich West and Stadtbahn Glattal. It is not yet clear whether Cobras will be ordered for these services or a different type will be chosen instead.
The six prototypes (3001-3006) are to be modified to the standards of the production units. This involves a major rebuild.
[edit] Design
The Cobra was styled by Pininfarina.
[edit] Controversy
The introduction of this new tram series has had a long and difficult history. The original orders were placed in 1996, with many questioning the choice of Schindler's Cobra over the already tested Combino series from Siemens, selected by both Basel and Bern. This decision was justified by the Verkehrsbetriebe Zurich on the grounds of carriage lengths and compatibility with the Zurich tram network.
The first models of the Cobra prototype were delivered in May 2001 after organisational changes within Schindler, Adtranz and Bombardier caused delays and renegotiations. The subsequent problems with structural weakness and noise within the new trams, causing them to be quickly withdrawn from service, added criticism.
However, since 2002 the six prototype vehicles have proven themselves successful and the teething troubles have been overcome. The go-ahead has therefore been given to expand the fleet to 74 trams by 2010.
