The invention relates to a machine formed by a grain-holding box containing a combination of two transverse plates, namely a front vertical plate that closes the box and another plate which is solidly connected to the front plate halfway along the length thereof, inclined at 45 degrees, projected forward and integrally welded to the structure of the machine. In addition, the running gear includes a back axle provided with a single shaft connected at the ends thereof to a pair of wheels, plus at least one crown wheel, and said at least one crown wheel is in turn linked by means of a transmission chain to at least one gear mounted on the ends of a control rod of an integral clutch device linked by another transmission chain to a hydraulic motor, with the actuation and control means thereof.