This study was chiefly concerned with the relationships between the ratio of unbalance weights and the position attached them and the separating capacities of a mixture of rices and paddies, using a shaking separator. The ratio of unbalance weights was the ratio of the inertia force of attached unbalance welghts to that of the vibrating direction of separating decks. And the separating capacities in the range of the discharge end were represented by the recovery, Newton's efficiency and the rate of grains in each part partitioned the discharge end.
The main results were as follows :
1) The relationship between the unbalance weight and the total weight of separating decks was :

W ≒ 0.76 a/a'W^*_p

Where, W^*_p : the total weight of separating decks, a : amplitude, W : mbalance weight, a' : central distance from a crank shaft to the unbalance weight.
2) In the case of both 0 and 270 degrees, attached unbalance weights, the distribution of grains in the discharge end was thin in the upper part and deep in the lower part But in the case of 90 and 180 degrees, that of grains was reversed.
3) In the case of 180 degrees attached unbalance weights, the values of recovery and Newton's efficiency were gradually increased with the increase of the rate of unbalance weights. But in the case of 270 degrees, these values were independent of the ratio of unbalance weights.
4) The range of a mixing layer in the discharge end were affected by the influence of both the ratio of unbalance weights and the position of them.
5) It is clear that the conditions of utilization of unbalance weights are at the values of 0.5-1.0 in the rate of unbalance weights and of 180 degrees in the position of them.