Articulation systems & folding bellows

Articulation systems and bellows form the mechanical and sealing connection between the front and rear sections of articulated buses. This portfolio is suitable for all articulated buses, regardless of the bus brand. The correct version does not depend solely on the make, type or year of manufacture, but on the specific chassis configuration, turntable construction, vehicle length, floor height and bellows configuration. Different articulation designs, gangway plates, guides and bellows profiles may be found within a single model range.

An articulation system generally consists of a central turntable or articulation bearing, support and guide rollers, radial and axial bearings, buffer stops, connecting arms, floor plates and chassis mounting points. The bellows comprise the bellows fabric, aluminium or composite bellows ribs, clamping profiles, sealing rubbers and, in some cases, integrated cable or air line pass-throughs. Materials must withstand torsional loads, UV radiation, road salt, moisture and thousands of articulation cycles. Even minor tolerances in bearing fitment, centring or bellows mounting can lead to rubbing, excessive noise and accelerated wear.

Common issues include creaking or knocking while steering, an unstable transition between both vehicle sections, rubbing floor plates, water ingress and visible tears in the bellows. Wear to articulation bearings or guide rollers often causes radial or axial play. This is particularly noticeable when pulling away, braking, driving over speed bumps and manoeuvring with a large steering angle. A damaged bellows may result from ageing of the elastomer, loose clamping strips, incorrect installation or a misaligned articulation point.

Park the articulated bus on level ground, secure the vehicle against rolling away and relieve the articulation only in accordance with the manufacturer's workshop instructions. First inspect the bellows all around for tears in the folds, porous areas, loose ribs and signs of contact with body parts. Then measure the play in the turntable and guide rollers using a dial gauge while the vehicle sections are moved in a controlled manner. Compare the measured radial and axial movement with the vehicle-specific tolerance values. Also check mounting bolts for the correct tightening torque, corrosion in mounting holes and ovalised bores. In the event of leaks, a targeted water pressure test is useful for locating failed sealing profiles or clamped connections.

Do not replace a bellows only when a complete tear is visible: early delamination, loose bellows ribs and permanent deformation can already affect sealing and freedom of movement. When replacing articulation bearings, rollers or support arms, the front and rear sections must be secured in the prescribed neutral position. Incorrect alignment significantly increases the load on bearings, bellows fabric and the floor structure. Use only fastening materials, locking devices and lubricants in accordance with the specified requirements; unsuitable grease types can damage seals or provide insufficient protection under high contact pressure.

Parts must always be identified using the vehicle chassis number. Visual comparison or selection based on the model name alone is never sufficient, particularly for articulated buses with revisions to turntable diameter, bellows height, mounting pattern or floor construction. Braem can assist with chassis-number-based parts verification and technical identification of the appropriate articulation components and bellows.