Tram with suspended articulation

A tram with a suspended articulation is a type of tram or streetcar architecture with one or more articulations being suspended. Here, articulations (i.e. permanent coupling) work like a hinge joint and are not supported by a bogie. This is unlike the more common solution with an articulation resting on a special connecting bogie, called jacobs bogie. Seen from the side at ground level, the suspended joint seems to be 'floating' because the lack of wheels directly under the joint.

A tramcar with both end sections partly resting on the centre section

The shortest examples consist of two sections. One section on two axles or two bogies; the other section rests both on one bogie and the other section, similar to a semi-trailer. In the diagram to the right, the short centre section supports the two end sections. Each of the end sections rests on one bogie and also on the centre section. It is a popular tram/light rail architecture for vehicles in North America.

History

Articulated tram GT3 in Bremen

Type F in Vienna

In 1928 an experimental tram was constructed in Görlitz and then put into service in Dresden until the mid-1960s. This car was numbered 2501 and had three sections: the center section had four fixed wheels, both end sections had each only one adjustable axle. Genoa was the first city to have a series of trams of this type. From 1940 onwards 31 trams were built by combining older tramcars. The lay out was very simple: the front section had one four wheeled truck, the end sections followed like a semi-trailer and had one fixed axle at the rear. The ride comfort was rather poor.

The first newly build series appeared in Bremen in 1956. The only difference with the type in Genoa was that the end car hand a one-axle bogie and therefore slight improved ride qualities. Vienna had an improved version of this type, with a two axle bogie at the end. This so-called Type F was longer than the version in Bremen and had a more streamlined design.

Second generation

The second generation of trams all have a pivoting bogie both at the front and the end side. This way the ride is much smoother when entering curves. The first to use this concept was the Mirage type in Zürich in 1966. The center rests on a set of four fixed wheels.

Low floor designs

The first modern low floor tram design also had floating articulations. Both Vevey and Duewag joined forces to create this tram type for the network in Geneva. Though the design didn't have an entirely low floor, as it was still 48 cm above the rail. The second type (being named TFS-2) has a similar setup as the Mirage trams for Zürich. Using floating articulations, Alstom was able to create a low floor (less than 35 cm high) over 60% of the tramcar length. Since the start of the Sheffield Supertram, it uses only vehicles with floating joints. This setup is used for the majority of LRVs in North America.

Gallery

• 
  Coupled Green line LRVs in Boston
• 
  Coupled LRVs in Seattle
• 
  Coupled Green line LRVs in Portland
• 
  San Diego Trolley LRV
• 
  LRV in Birmingham (UK)
• 
  Tram train in Sheffield
• 
  Tram in Saint Petersburg
• 
  Tram in Melbourne

See also

• Articulated tram