Bus Articulation Systems: A HÜBNER Success Story

02.04.2008 17:00

Press release


Bus Articulation Systems: A HÜBNER Success Story

As buses have changed and developed over the years, the demands placed on the articulated joints joining vehicle sections have undergone many changes. The evolution of these components through the decades is presented here by Dr. Stefanie Böge, responsible at HÜBNER GmbH for strategic organizational development in the division for street vehicle gangway systems. 


Tight curves, narrow streets – into the 1950s, buses with attached passenger trailers were used to overcome the characteristic space problems found in urban settings. When these trailers were forbidden, various manufacturers designed single or dual axle vehicle segments that were attached to the main propulsion vehicle by an articulated connection in order to cope with the limited street space in cities.


At first it was common to have the second of the three axles be the drive axle in articulated buses. With this arrangement, the bus motor (at this time an underfloor motor) was located in the front of the bus. This design had a number of disadvantages, particularly from a maintenance standpoint. And over time, other disadvantages also became apparent. For example, vehicle manufacturers wanted to have a uniform design for the powertrain. In addition, there were more and more low-floor buses that did not allow for such a construction. As a result, buses with a so-called pusher design have become increasingly popular since the 1980s. In buses of this type, a rear-mounted motor drives the back axle of the articulated bus. With this new design, it was necessary to develop articulation systems that were capable of transferring the altered driving forces from the rear to the front of the vehicle.

HÜBNER GmbH began producing single components for public transportation more than 50 years ago in the 1950s. These included folding bellows, for example, which protected the gangway between the segments of articulated vehicles. As articulated buses evolved, it was soon recognized that complete articulation systems were required. It should be possible to use these systems in the widest possible range of vehicle types and particularly in low-floor buses. In line with these requirements, a low-floor articulation system for use together with the existing folding bellows was designed. The issue of a damping system that could meet the demands of a pusher bus in all kinds of operating situations was also addressed at this time. The aim was to provide vehicle manufacturers with a complete solution made up of an articulated connection, a damping system and a folding bellow that could be used in diverse operating situations and settings.


In the construction of such complete systems, solutions using modular graphite casting were preferred from the beginning. The material characteristics of this approach in the context of the limited construction space in low-floor vehicles provided a way to realize a system that was both safe and economical. During the development phase at HÜBNER, measurements and tests were conducted around the world to determine the requirements arising under different operating conditions and in different settings so that these could be integrated into the final design.

However, in the course of this development phase, it became evident that the initial idea of developing a universal articulation system for all different vehicle types was not, in fact, practical. Consequently, as time went on, a range of different articulation systems were developed to meet different requirements. The aspect of service-friendly design also came to take on increasing importance.


The universal articulation system comes closest to realizing HÜBNER’s original development aim, and it can be viewed as the “mother” of all HÜBNER articulation systems. It is the most frequently used system worldwide. Its advantages lie in the simple and clearly defined connection surfaces allowing for problem-free fitting to the front and rear vehicle segments. Today it is available in a standard and a deluxe version, both of which are nearly maintenance free. The main components of the system such as the bearing, the system control and the damping elements are all easily accessible. In the event of damage, single dampers can be replaced individually. Usually the universal articulation system is delivered with an electronic control system that detects the driving situation, controls the driving performance and also conducts a system diagnosis for early detection of any defects.

The heavy-duty articulation system has similar characteristics to the universal system, but has been specially developed for vehicles with higher axle loads (gas or trolley buses). This connection is used with particular frequency in North America . And for the hybrid buses planned for use in Europe , the heavy-duty system also has advantages. Standard axle loads in excess of 2.5 tons can easily be accommodated.

New in the product range is the compact articulation system produced by Hemscheidt. Like the universal articulation system, this product can also be used in all types of articulated buses and displays a compact design, a simple fitting procedure and a low sensitivity to dirt and soiling. The integrated damping system is maintenance free and robust. The system is designed so that all its moving parts are located in an oil bath and as a result function with virtually no wear. This is the basis of the system’s low-maintenance requirements.




The ball articulation is somewhat different from other articulation systems. It is simply constructed, economical and resilient, and was specially developed for puller vehicles. Since it also can be used in low-floor vehicles, it additionally can serve as an alternative for pusher vehicles. It is used particularly in articulated buses in Africa and India . In comparison to other systems, it represents the simplest connection between the front and rear segments of an articulated bus. The special bearing supports large rolling motions, however it is not equipped with hydraulic or mechanic damping. The ball connection is delivered as a ready to install component.

Against the background of a world transportation market with increasingly divergent requirements, the family of HÜBNER articulation systems meets all conceivable demands. This is why most new transportation concepts such as bus rapid transit systems feature HÜBNER products. As conditions continue to change, however, new and continuing product developments are necessary. For Europe and North America , for example, articulation systems are being developed that support improvements in the safety technology. A new generation of articulation control systems is just about ready to be launched in the market. In Asia and Africa , highly robust articulation systems for less expensive vehicle types are required, and new developments are also underway in this segment. In addition, work is ongoing on an articulation solution that will support a modular vehicle. In the context of diverse demographic and spatial developments, it is advantageous for public transport operators to be able to adjust vehicle capacity in accordance with shifting demand.

The HÜBNER Group

As a comprehensive system supplier, the HÜBNER Group manufactures key components for the transportation industry (for rail vehicles, buses, airport technology, automobiles and trucks) as well as medical technology products. The range of products and services includes the design and production of folding bellows, vehicle articulation systems, flexible gangway systems, door and window systems, PUR molded foam components as well as products made of rubber and injection molded plastic.

Worldwide more than 20,000 HÜBNER articulated joints are in use today in vehicle produced by such manufacturers as MAN, Mercedes, Neoplan, Solaris, Volve, Irisbus-Iveco and Carrosserie Hess.

Service-Tips: robust and flexible over many years

Regular maintenance monitoring of the articulation system once a year does not require much time, and can help to avoid expensive secondary damage and vehicle downtimes:
  • Keep the folding bellow and its base in good condition. If holes form, moisture and dirt will enter the joint area. Quick repair of such wear prevents corrosion damage to the articulation system.
  • Lubricate the articulation system bearing regularly. Regular lubrication in accordance with maintenance recommendations prevents premature wear and excessive noise in operation.
  • Perform a visual inspection at regular intervals. Pay particular attention to drop formation on all hydraulic parts. To ensure high safety standards, repair or exchange these components immediately.
  • Take advantage of the regularly offered maintenance training sessions for articulation systems. This will keep you up to date on the latest standards and help you to perform maintenance efficiently and effectively.

Text: Dr. Stefanie Böge

Pictures: HÜBNER GmbH




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