Determination of the Friction Angle between the Wheat Ear and Stripper Fingers

Abstract

Introduction. Determining the angle of friction between stripper fingers and a wheat ear is an important task aimed at finding the optimal design parameters and operating modes of stripping devices. When stripper fingers and wheat ears interact, the relative position of the ear glumes, flower glumes, and grains is densified. In this case, the spikelet surface roughness changes. Materials and Methods. A series of experiments was carried out to determine the angles of friction between a steel stripper fingers and wheat ears. Wheat varieties “Moskovskaya 40” and “Moskovskaya 56” were selected for the study. The experimental measuring installation is a frame with a rotatable platform mounted on it with the adjustable angle of rotation. The goniometer head provides the ability to fix the platform rotation angle value. The weight suspended from the stem of the plant imitated the forces arising in the process of stripping. The width and thickness of the wheat ear were also measured and recorded. Results. The influence of the size of the wheat ear on the angle of friction is determined. The results of the study are divided into two groups. The following values of the friction angles were obtained: 26.4–31.5° for the wheat with ear width of less than 10.4 mm; 22.0–27.1° for the wheat with ear width of more than 10.4 mm. Discussion and Conclusion. The angles of friction of wheat ears on the stripper fingers for wheat varieties specific to the Central region are obtained. The dependence of the angle of friction on the ratio of the geometric dimensions of the wheat ear and the slit width of the stripper fingers is established. When a wheat ear width is less than 10.4 mm, an effect of pinching the spikelets between the stripper fingers was observed. In this case, the coefficient of friction noticeably increased.