The Figure shows one side of the lower structure. The travelling gear receives motion from an electromotor of 150 H.P. (at 450 revolutions). The carriage of the unloader proper, which travels on this structure, has twelve wheels in front and four at the rear end, and there are also at the back two further wheels which press against a rail above to prevent tilting of the apparatus. The carriage of the unloader supports a balance beam, which carries the unloader itself on its vertical iron arm, whilst the winding gear is situated at the rear end of the beam.