Modern Tramway and Light Railway Review, June 1962 carried an article based on notes by H.J. Bertschmann, G.A. Meier and M. Frei about then new articulated trams in these two Swiss cities. [1]

Both the Basler Verkehrs-Betriebe and the Verkehrsbetriebe der Stadt Zürich had taken delivery, in the months prior to the article being written, of the first prototypes of a new design of articulated tramcar. The design was a new departure, a double-articulated tram on three trucks. Earlier models of articulated cars had  two sections on two or three trucks, or three sections on two or four trucks, but never before three sections on three trucks.

“Wages costs represent a very high pro- portion of the total costs in the operation of public transport, and in both Basel and Zürich reach[ed] 80 per cent of the total expenditure. Economy in staff [was] therefore the only way in which undertakings [could] remain solvent, and the rapid increase in traffic oblige[d] transport undertakings to use high-capacity vehicles in order to minimise utilisation of the road surface. The development of bogie cars was the first step in this direction, and the delivery of the first articulated cars carries this a stage further.” [1: p19]

The very different technical requirements of the Swiss urban transport undertakings had often hindered the development of a Swiss standard tramcar, one of the difficulties was caused by differences in the topography of the towns.

“This … led to a unified effort by the Basel and Zürich undertakings, the two largest tram- ways in Switzerland, to design an articulated car whose basic design was suitable for both undertakings. Whilst a classical (by German standards) two-section single-articulated six-axle car was built for Zürich by SWS (Schlieren), the co-operation between the two systems to find the most advantageous design resulted in an order for three articulated cars, two for the BVB (Basel) and one for the VBZ (Zurich), being placed with SIG (Neuhausen). SIG conceived a new style of construction, departing from the customary articulation over the central bogie (known as a Jacobs bogie) in favour of a short middle section on a two-axle non-rigid truck with an articulation at each end.

There [we]re so many common features in the design for both BVB and VBZ that practically the only differences [we]re in the number of motors and their electrical connections. Basel cars [had] four motors totalling 264 kW, whilst Zürich cars [had] six motors rated at a total of 396 kW. Motor bogie wheels ha[d] a diameter of 720 mm against the 660 mm of the Basel middle bogie wheels. Whilst the Basel cars [would] normally each haul a bogie trailer and the Zürich prototype car will also do this, the production batch of Zürich cars [would] run in multiple-unit pairs, and … (like Basel) have only two power trucks. Zürich has still to decide whether the two leading trucks will be motored, as distinct from the end trucks as at Basel. By confining the differences to these features (apart from minor differences in interior styling), the cars [could] achieve the maximum economy whilst ensuring the best use of the adhesion weight. By means of special mechanisms, it was possible to arrange the axle loadings so that the load on the driving axles was the same in both the four-motor and six-motor cars. Variations in the axle-load on the middle truck induce[d] horizontal forces in the upper part of the articulations; these induce[d] turning movements in the vertical plane, with consequent transfer of load between the outer and inner trucks. As a result of this design, the car [was] better able to start from rest on hills. [1: p19-21]

The advantages of the new design were:

• The middle truck is not under the articulation mechanisms – so maintenance is much easier.
• Rotation over each of the two mechanisms is half of that for one mechanism.
• The body did not obstruct the drivers view of the exit doors which are in the middle section of the tram.
• Double articulation permits wider front and end designs which allows doors to be built in the parallel sides of the tram.
• A minimising of internal obstructions for passengers was achieved by the lesser amount of articulation required.

Trams travelled at a maximum speed of 60km/h and had a capacity of 42 seated and 123 standing. The empty car weighed 28.3 tonnes. The significant dimensions of the tramcars were:

• Overall length between couplings: 20.45m
• Length of body: 19.7m
• Height of roof over rails: 3.385m
• Width: 2.2m
• Distances between king-pins: 7.0m
• Overhangs: 2.85m
• Wheelbase of motorised truck: 1.86m
• Wheelbase of non-motorised truck: 1.7m

The article describes the trucks, braking systems and control systems as follows:

“The motor trucks are swing-link trucks with outside frames and torsion-bar springing. The springing of the torsion bar and the swing-links is combined into a single springing system, and this contributes considerably to noise reduction, in conjunction with the resilient wheels. The longitudinally-mounted motors are held by a three-point suspension to the truck frames, using rubber inserts.

The braking system: … The service brake is rheostatic, augmented with an air-operated disc-brake. A Charmilles brake handle is fitted under the controller wheel (a Volkswagen steering-wheel), … the air brake automatically supplements the electrical brake as the regenerative current dies out, and excessive braking through combined electric and air braking applications is eliminated. In an emergency, the braking effort can be supplemented with magnetic brakes. The parking brake is a hydro-mechanical hand brake. An Electro-pneumatic valve proportions the application of air to the trailer and (on the Basel cars) to the un-motored truck.

The control system has 22 running notches, of which the last three are field-weakening notches; there are 23 notches for rheostatic braking and a 24th emergency notch for magnetic braking in addition. The motors are connected in series pairs, each motor operating at half-voltage, and every effort has been made to keep the number of power cables crossing an articulation to a minimum.” [1: p190-191]

The Modern Tramway Journal also reported on a number of other features:

“The exit doors incorporate a device similar to that on the Stuttgart articulated cars. They are operated by the passengers through a push-button, and the opening of a light inner door by the passenger in order to gain access to the step holds the main doors open. The other function of the inner door is to prevent the entry of passengers at the exit doors. In Zürich, passengers would press the push-button to signal to the conductor to open the doors, whilst Basel had intended that passengers should open the doors themselves. However, as Basel experienced some confusion with this arrangement, they changed over to the Zürich system.

Particularly interesting features of the new cars include a “Hesomat” indicator blind, driven by an electric motor. The driver merely presses a “tens” button and a “second digit” button for the code number of the desired destination, and this is automatically set-up. Another innovation is the point-changing button enabling the driver to simulate a “power” signal whilst coasting past the detector. To prevent the current taken by auxiliaries causing a false “power” signal, a push-button in the centre of the controller wheel can cut off all auxiliary power as the detector is passed.

The Zürich undertaking needs new cars urgently and it is hoped that the number of articulated cars will ultimately rise to 200; they are intended to be the basic unit for the planned Tiefbahn (subway) services. The Basel plans are less ambitious for the present, but they hope to operate route 6 entirely by these cars at some date in the future. This route, from Allschwil to the German border at Riehen, is one of the fastest urban routes in Switzerland, and these cars should be particularly suitable.” [1:p191]

Ultimately, tram No. 1801 was a success as a prototype in Zurich. A series of these vehicles were purchased later in the 1960s and were called ‘Mirages’. [4] An online acquaintance tells me that a number of these trams were later sold to the city of Vinnytsia in Ukraine. Details can be found here, [6] and in the YouTube video below. [7]

Tram No. 601 and its partner were less of a success in Basel. As a result, the two trams ordered by Basel were not followed by a larger order. They remained the only Basel trams of their specific type. [5] Basel did purchase further articulated trams but from different a different source.

References

1. H.J. Bertschmann, G.A. Meier & M. Frei; New Articulated Tramcars for Basel and Zurich; in Modern Tramway, Light Railway Transport League and Ian Allan, Hampton Court, Surrey, June 2022, p187-191.
2. https://en.sporvognsrejser.dk/foto/s/basel-articulated-tram-601-on-aeschenplatz-1981.jpg, accessed on 2nd August 2023.
3. https://en.sporvognsrejser.dk/foto/postcard-zurich-articulated-tram-1801-at-the-depot-tramdepot-irchel-1975, accessed on 2nd August 2023.
4. https://transphoto.org/vehicle/276178/?lang=et, accessed on 3rd August 2023.
5. https://ba.e-pics.ethz.ch/catalog/ETHBIB.Bildarchiv/r/690998/viewmode=infoview, accessed on 3rd August 2023.
6. https://en.m.wikipedia.org/wiki/Trams_in_Vinnytsia, accessed on 10th August 2023.
7. https://www.youtube.com/watch?v=Gh7sMfSNK08, accessed on 10th August 2023.