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.
The articulation system connects the front and the rear vehicle segments.
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
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.
THE LOW-FLOOR BUSES WHICH CAME INTO USE IN THE 1980S REQUIRED
A NEWLY DESIGNED ARTICULATION SYSTEM THAT CONNECTED THE FRONT AND REAR
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
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 platform and the folding bellow protect the articulation system from moisture and dirt.
The universal articulation
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
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
. And for the hybrid buses planned for use
, the heavy-duty system also has
advantages. Standard axle loads in excess of 2.5 tons can easily be
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.
NEW DRIVE SYSTEMS WITH HIGHER WEIGHT AS FOUND IN HYBRID BUSES REQUIRE NEW ARTICULATION SYSTEMS THAT CAN ACCOMMODATE THE INCREASED LOADS.
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 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.
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.
continue to change, however, new and continuing product developments are
, 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
, 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
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.
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
Service-Tips: robust and flexible over many years
maintenance monitoring of the articulation system once a year does not require
much time, and can help to avoid expensive secondary damage and vehicle
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