The results of theoretical studies confirming the possibility of carrying out preliminary separation of free grain from the stripped grain pile before it enters the threshing chamber of a combine harvester are presented. The prospect of a separating device mounted directly in front of the threshing drum, consisting of longitudinal rods, over which an additional scraper conveyor is mounted, has been established. The cross section of each strip of the grating is narrowed downwards to increase the intensity of separation of the device and eliminate the possibility of clogging the holes with passing particles of the heap. The optimal length of the openings of the pre-drum type separating device, its spatial orientation were determined, and the quality indicators of the work were evaluated. Theoretical studies of the separation process on winter wheat of the “Moskovskaya 56” variety with a grain size of 3.9x6.5 mm were performed. The speed of the scraper conveyor was 3 m/s, and the angle of inclination of the separating device varied within 0-45 degrees. It has been established from the results of research that with an increase in the angle of inclination of the separating surface, the length of the sieve openings increases, and the separation speed decreases. Since the horizontal grate provides a higher separation rate of free grain, compared to an inclined surface, the use of a pre-drum type separating device is most preferable in relation to the grate bottom of the feeder house of a combine harvester in terms of its performance. It has been established that the length of the separating holes should be at least 0.08 m. Such a technical solution allows minimizing not only the crushing of free grain by the working bodies of the threshing machine, but also to reduce the metal consumption of the separating device.

SUBJECT OF THE STUDY: Is the process of preliminary separation of loose grains from combed grain heap on the slatted bottom of the feed elevator of a combine harvester. AIMS: Is an efficiency evaluation of the combed grain heap separation on the slatted bottom of the inclined chamber of a combine harvester in the field and to compare the degree of crushing of free grain depending on its supply to the threshing device or directly to the cleaning system. METHODS: All studies were carried out on winter wheat of the Moskovskaya 56 variety with a yield of 30 c/ha. Plant height varied within 0,60,9 m with a grain ripeness of at least 98% and a moisture content of 14%. The serial grain header ZHO-5 OZON manufactured by PJSC Penzmash was aggregated by the Niva-Effect combine harvester with a constant speed of 8 km/h and a stripping cylinder speed of 485 min-1. The field experiments were divided into two stages. The first series of experiments was devoted to evaluating the efficiency of preliminary separation of combed grain heap on the slatted bottom of the experimental feed elevator. During the second series of the experiment, grain was harvested with a serial feed elevator without its preliminary separation. RESULTS: According to the results of the first series of studies, it was found that the passage of loose grain through the holes of the slatted bottom of the inclined chamber is 91,6%. At the same time, grain crushing in the feed elevator did not exceed 0,5%, and in the bunker 1,75%. During the operation of the combine with a serial feed elevator without preliminary separation of the combed grain heap, the crushing of the bun-ker grain was within 5,25%. CONCLUSION: The practical implementation of such a technical solution makes it possible to 3 times the grain crushing in a bunker by the working bodies of the threshing machine.

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The dependence of power consumption during separation grain from ear on inclination angle of riffles of working parts threshing mechanism in case of sign-variable load of connections, is obtained.

The results of the laboratory experiment confirming the possibility of preliminary separation of free grain from the combed grain heap before it enters the threshing chamber are presented. In particular, it is proposed to provide a combine harvester with a device for pre-separation of free grain, mounted between the inclined chamber and the threshing device. It includes two drums and an infinite mesh cloth. To intensify the process of separation of the combed grain heap on the fraction of the axis of rotation of the drums are made eccentrically with respect to their geometric axes. All studies were carried out on wheat varieties «Moskovskaya 56». Grain moisture was about 12 %. The speed of movement of the floating conveyor had five levels of variation in the range of 3-5 m/s. Flow oceanog grain heap was about 10 kg/s at a content of 80 % of free grain. The length of the mesh conveyor was 2 m, and its rectangular cells had dimensions of 17×15 mm. Thus, according to the results of scientific research, as the speed of the mesh conveyor increases, the amount of free grain passing through its cells tends to decrease, and the amount of grain coming down from it, on the contrary, to increase. The maximum passage of free grain (94,66 %) corresponds to the minimum speed of the mesh conveyor, equal to 3 m/s. The presence of free grain is due to the fact that during a series of experiments, the length of the separating surface was insufficient. To determine the optimal length of the mesh conveyor, the nature of the process of preliminary separation of free grain from the combed grain heap is considered. Extrapolation of this process shows that the minimum length of the mesh conveyor, providing 99 % of the free grain from the combed grain heap, must be at least 2,69 m. The practical implementation of such a technical solution in the design of a modern combine harvester will increase its productivity when combing plants at the root, reliably eliminating the possibility of crushing free grain by the working bodies of the threshing device.