Innovative trains
In July Siemens celebrated the signing of a landmark contract that will take its next-generation low-floor LRV to the Middle East. Keith Barrow uncovers the innovations behind the Avenio.
Avenio Electric
floor LRV to withdraw their fleets following the discovery of cracks in the aluminium bodyshells of some vehicles. Siemens found that torsion forces generated in S-curves were higher than expected, causing cracks around the articulation joints between the vehicle modules, and leading to costly rectification work on 475 first- generation Combino vehicles. While this was undoubtedly a major setback for Siemens, it also presented a unique opportunity to gather valuable data which might benefit the development of future LRVs. Siemens studied the actual load and operating conditions of 13 different light rail operators, pooled the results in
B
The Hague Avenio Length
Width
Wheel arrangement Traction motors
Starting acceleration Maximum speed Wheelbase
Wheel diameter Electrification
Weight (empty) 35m 2.55m
Bo-Bo-2-Bo 6 x 120kW 1.2m/s2 80km/h
1800mm 600mm 600V dc
Passenger capacity (4/m2) 70 seated 168 standing 49.4 tonnes
ACK in 2004, Siemens hit the headlines when it instructed operators of its Combino low-
a fatigue-strength verification study, and established the true mechanical strength of the body structure. Siemens says that the use of real stress values meant it was able to design a lightweight body that is more capable of coping with the stresses of everyday light rail operation. The results were quickly put into practice on the Combino Plus LRVs supplied to Almada, Portugal, in 2005 and Budapest in 2006.
Historically trams have traditionally been built using multiple-articulation with a long wheel-less body section supported between two short car sections with rigid bogies. This asymmetrical arrangement puts huge stress on the articulating joints and the structure because the suspended section is exposed to strong transverse acceleration when cornering at speed. With Combino Plus, Siemens adopted the concept of the single articulated vehicle, whereby each of the outer and intermediate sections has its own powered or unpowered bogie. This significantly improves performance in curves and allows production of a variety of different vehicle lengths - the 54m-long Combino Budapest is the longest passenger-carrying LRV in the world.
The latest generation Avenio LRV takes all this a stage further. Avenio retains the centrally-mounted bogie arrangement of the Combino Plus, but has longitudinally-coupled independent wheels, which are mounted in a frame unit instead of being connected by an axle. The traction drive units are mounted on the outside of the wheels, meaning they can be accessed easily for maintenance from the side of the vehicle without the need to remove the bogie. Traditionally the driving wheels of a tram were connected transversely via an axle shaft. This means energy is wasted on curves due to friction because the outer wheel has to travel faster than the inner wheel. By removing the axle, the Avenio’s wheels can rotate at different speeds, reducing energy loss through friction. Furthermore, the bogie can rotate at up to 4.5 degrees, allowing it to move more freely in curves. Siemens says the torsionally-flexible bogie arrangement substantially reduces lateral forces on both the wheel and track compared with a conventional tram with multiple-articulation. A 2.65m-wide Avenio has a uniformly-distributed axleload of less than 10 tonnes and,
HTM was the debut customer for Avenio. A mock-up of this vehicle will be on show at InnoTrans.
IRJ September 2012 63
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