Investigation of mechanical interaction between a combine harvester reel and crop stalks

In the present study, the relationships between the deflection and deflection force acting on a bunch of crop stalks in the gathering operations of a combine harvester reel were analysed. Two mechanical crop models based on bending theory with regard to an elastic beam were applied in this analysis. In the first model, the sectional heterogeneity of a stalk is expressed as the different flexural rigidity of each internode. In the second model, the effect of a crop ear is added to the first model. The application of the mechanical models to the reel operations and the analytical methods of the deflection force were investigated using experiments involving reel operations. The results showed that the effect of both the buckling load due to the weight of the ear and the vertical force component acting on the crop stalks increased noticeably with the increment of deflection imposed by the gathering operations. The prediction of the relationships between deflection and deflection force in the second model, in which the effect of the ear weight was considered, involved a certain amount of error due to the effect of the initial posture of the crop stalk and the vertical force component, but coincided approximately with the experimental results. Thus, it was suggested that the model that took into account the effect of the crop ear was useful for investigating reel-crop interactions, and that the analytical accuracy of the deflection force would be increased by considering the effect of the vertical force component. Further, based on the above results, a posture analysis of a bunch of crop stalks during reel operations was conducted. (C) 2002 Silsoe Research Institute. Published by Elsevier Science Ltd. All rights reserved.