Separation of Potatoes from Clods and Stones and a Feasibility Study on Grading of Tuber Using Coefficient of Restitution

Potato is a strategic agricultural product. Due to a high economic value, it is necessary to separate the tubers from clods and stones before being transferred into storage tanks. This is one of the most important tasks in potato harvesting machineries. Despite many advantages, potato harvesting combines are not welcomed by farmers in Iran due to the lack of suitable agricultural soil textures and missuse of chemical fertilizers. Therefore, it is necessary to install an extra system in the combines to enable them to carry out an efficient separation task. In this article, a feasibility study was carried out on the separation of potatoes from clod and stone using the coefficient of restitution. A pendulum apparatus was used to determine those factors affecting the coefficient of restitution and the latter was compared in potato, stone and clod. A special device was designed, constructed, and evaluated in order to study the distribution pattern of tubers and clods after colliding with a separator surface. It was a semicircular plate, mounted at its center a quarter sphere made of steel. The surface of the aforementioned plate was divided into sections using wooden and rubber strips. The results showed that the effect of mass, velocity, and material of the colliding body as well as the effect of the velocity and material of the colliding body on the coefficient of restitution is significant at 5% level. An efficient separation of potato from clods and stones was achieved for the masses of greater than 60 g, and when the moisture content of the clods was 12 to 39%. The distribution pattern of potato tubers and clods on catch surface showed that the device could successfully be installed on the combines in Iran and it could be used to separate tubers from other materials efficiently using the coefficient of restitution.