agricultural engineering. SUBSTANCE: unit has tubular girder and carriage adapted for displacement along tubular girder and connected to self-propelled wheeled cart, chain located in housing, which is composed of two parts and fixed on outer upper surface of tubular girder, two sprockets, one of sprockets being attached to one end of tubular girder and other being positioned so as to be fixed on supporting tube 4 by movable pin. Free end of tubular girder has folding-back two- legged support used as rest for outer girder end. EFFECT: increased efficiency and simplified maintenance and operation. 3 cl, 11 dwg