Threshing unit with a rasp-bar drum for maize grain harvesting

The paper demonstrates that interaction between the threshed material and working elements of a threshing unit leads to changes in its physical and mechanical properties. However, the influence of these changes on the conditions of material capture and retention has not yet been sufficiently investigated. Effective threshing requires reliable capture and stable retention of the material. In maize ear threshing, the efficiency of this process is largely determined by the relationship between the main parameters of combine harvester, its productivity, and power demand, taking into account the physical and mechanical properties of the material. (Research purpose) To establish the relationship between the movement speed of threshing products and the power characteristics of combine harvester during maize grain harvesting. (Materials and methods) In practice, the optimal range of the maximum maize capture angle is established experimentally and depends on ear moisture content and the rotational speed of the working elements. The study examines factors influencing the efficiency of maize grain threshing in the threshing-and-separating unit of a grain combine harvester. Statistical meta-analysis methods were applied to quantitatively integrate the results of scientific studies employing similar methodologies, with the aim of establishing the dependence of threshing quality on crop condition and threshing drum settings. (Results and discussion) The gripping ability of the threshing drum increases with a higher coefficient of friction between the ear and the rasp bar surface and with a lower coefficient of friction between the ear and the concave. It is also established that the moisture content of the material influences the threshing drum speed during operation. The study establishes the dependence of threshing quality on the parameters of the threshing clearances at the inlet and outlet of the concave. It also determines the required power by taking into account the performance of all processes and operations involved in maize grain threshing. (Conclusions) The analysis revealed a dependence between the movement speed of threshing products along the raspbar drum of a maize combine harvester and its power characteristics.

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