An agricultural machine has a symmetrical chassis hydraulically transformable between a folded transport configuration and two unfolded configurations, using articulated beams. An air seeder example has a primary beam linking a tractor to a hopper-carrying trailer, also locating the chassis. Machinery such as seed openers is held in frames pivoted from the tertiary beams. In all configurations except completely folded, lateral chains that are maintained tight with a hydraulically powered tensioning system having sideways compliance maintain the tertiary beams and frame-supported machinery in a symmetrical configuration to each side of the primary beam, when working.
