Bus articulation joint (pivoting joint with bellows)

Description

The mechanical assembly that links the two rigid halves of an articulated bus: a pivoting joint (the kinematic pair that lets the rear section yaw — and on hilly routes, also pitch — relative to the front), enclosed by flexible bellows on the inside and outside and a cover plate across the floor so passengers can walk between sections. The joint is what turns two ordinary bus bodies into a single 18 m vehicle that still negotiates ordinary urban turning circles. Production of the articulation assembly itself has been the province of a small number of specialist suppliers — for example, ATG Autotechnik GmbH near Hamburg — distinct from the bus manufacturers that integrate them. The joint design has evolved with the form factor: simple single-pivot articulation in the 1937 Milan and 1938 Twin Coach Baltimore vehicles; double-pivot 'biarticulated' designs from the 1990s onward to support the 24-27 m vehicles used in Curitiba-style BRT.^[1,2]