This paper deals with the possibility of the separation of two groups of grains with the different friction coefficient, using the test pieces of various materials. The experimental apparatus is the moving sloped plane of vinyl cloth.
The main results are as follows ;
1. In the case of sliding motion of grain, the grain is conveyed upperward under the condition of R > 1, on the contrary, slides down under the condition of R < 1 notwithstanding of belt speed, and remains continuously at any point of the inclined plane under the condition of R = 1.
2. As the separating efficiency increases with the larger difference of sliding friction coefficient of grains, when the separation is done by it, the normal distribution curves of the sliding friction coefficient of grains may be of value.
3. The difference of the sliding friction coefficient between paddy and rice is so small that the separation may be almost impossible, even if the better separation is expected.
4. For the spherical grain, the initial condition of grain to roll down is R ≦ 2/7, then the motion of paddy and rice are done by both rolling and sliding.
The efficiencies of regain of paddy and rice under this condition are the values of about 20%, respectively, and the improvement of the efficiency of regain may be impossible.