ATTIKO Metro is to take delivery of 21 six-car trainsets from the Hanwah-Rotem consortium in Korea. Seven units in the fleet will be fitted with dual-voltage equipment to operate on existing routes electrified at 750 V DC third rail and on the new line being built to Eleftherios Venizelos airport wired at 25 kV 50Hz. The rest of the fleet will run only on DC lines.
Contractor for the pantographs and third-rail current collectors for the entire fleet is Stemmann-Technik GmbH of Germany. To avoid unpleasant surprises with the third rail collection gear at the commissioning stage, the company decided to test a pre-production collector shoe on existing rolling stock. The top-contact third rail has ramps at the end of each section that are inclined at 1:50, but the lower part of the ramp is inclined at 1:6 to avoid shoes under-running. The tests included a worst case situation of shoes striking the 1:6 ramps at 80 km/h.
Measurement of the contact behaviour between the shoe and third rail was contracted to Deutzer Technische Kohle GmbH, and finite element analysis of the shoe design was commissioned from Ingenieurbüro KRW.
The current collector is mounted on the bogie frame and is lowered into position pneumatically. Rubber elements are located immediately over the contact surface to compensate for unevenness of the traction supply rail and to help ensure a smooth transition on and off the ramp at the end of each rail section.
Simulation of the design elements and trials in Athens included video monitoring of shoe behaviour. The results were used to fine-tune the design to ensure that good contact was maintained between shoe and the surface of the power rail and that arcing is avoided wherever possible.
Stemmann-Technik GmbH, Germany
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