Introduction. The article presents the results of theoretical and experimental studies of threshing and separation processes in the threshing mechanism of the combine harvester with a digital assessment of the fractional composition of the grain-and-straw material being threshed. The obtained data will allow detecting dynamics of fractional composition of grain-and-straw mass being threshed in the threshing gap of the threshing mechanism depending on its supply. Materials and Methods. The research was carried out on a special stand in the form of a separate unit of the combine threshing mechanism. Grain-and-straw samplers were installed under each threshing section. The mass feed was changed from 1.0 to 6.0 kg/s at a straw ratio of 1:1. The obtained data were approximated using a standard procedure. Results. There was determined the amount of grain and straw passed through the threshing section screen and the rest of grain and straw entering the straw separator depending on their initial amount. For each fraction, there were determined the ratio of straw mass to grain mass, the density and thickness of the grain-and-straw heap layer on the shaking board ahead of the grates and at the beginning of the straw separator keys. The dynamics of grain-and-straw separation was identified by scanning the length of the grains with the determination of the density and compression degree of the grain-and-straw mixture layer in the threshing gap. Discussion and Conclusion. It was found that in the heap of grain-and-straw passed through a threshing section, the ratio of straw mass to grain mass decreases from 0.46 to 0.27 and density increases from 60.1 to 84.0 kg/m3. In the heap of grain-and-straw that fell on the straw separator, the ratio of the straw mass to the grain mass decreases from 11.2 to 2.0, the density increases within a small range from 21.7 to 26.4 kg/m3. Thickness of the heap layer on the shaking board in front of the cleaning sieves varies in the range 0.25‒10.20 cm, and on the straw walker ‒ 2.2‒19.8 cm when changing the supply of the total mass for threshing from 1 to 6 kg/s.

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.