The purpose of research was to compile a mathematical model of a reaper thresher in the form of connected graphs of flows: grain and head, allowing to determine the working elements violating the principle of machine's design harmonicity. The description of the principle of machine design harmonicity is made using the mathematical model constituent presented in the form of a connected graph. From the analysis of connected graphs it follows that the local zone of the harvesting section contains cuts with one working element, and the local zones of the thresher have cuts with two or more working elements, and also contain simple cycles. The symptom of realization of harmonicity principle in working elements of the harvesting part of a reaper thresher is the equality of a parameter of the controlled flow (feed) to the calculated value of the indicator of the working element (capacity), when a zero flux flows through the uncontrolled flow chain. When examining the working elements of the thresher it is necessary to exclude the influence of the circulation flow on the technological process, and in the absence of indicator values (efficiency) and / or controlled flow parameter (feed), to apply formal characteristics. In the field study of the working elements of the cleanup system of the RSM-142 “ACROS-530” reaper thresher it is determined that the circulation flow through simple cycles contributes to the violation of the harmonicity construction principle, and the mass-produced design of the distribution auger helps to reduce the given feed into the grinder of the combine. The use of a new design of a distributive auger allowed increasing the given feed to thresher during winter wheat and barley harvesting by 7–8 %.
Key words: mathematical model, design harmony, reaper thresher, connected graph, performance criterion.
