In the operation of the semi-automatic farm machinery, the driver of the machinery must maintain the workig speed of these machinery within the range that the operators do not feel excessively fatigued in their hand work and the results of operation are kept within the resonable degree of accuracy. To estimate the optimum working speed of such operation from these points of view, the experiments were carried out on the operation of the hand fed potato planter, and the results obtained were as follows.
1. The range of tempo that the operator could drop potato tubers smoothly was from 0.43 to 0.8sec. per cycle of dropping and the optimum range was from 0.6 to 0.8sec. The operator felt the motion of dropping difficult at the tempo outside of this range.
2. From motion studies, it was obserbed that at the tempo of dropping smoothly the operator moved and stopped his both hand simultaneously and rhythmically and the time of each motion required in each cycle and in each hand was reasonably constant. But, at the tempo of dropping too fast or too slowly each hand did not move constantly and rhythmically, and the rhythm of dropping motion was often disturbed by the movement of left hand (the whip hand of the operator was right)
3. The number of tubers dropped at the faster tempo than 0.5sec. was less than the predetermined one, and thus the plant number per ha was decreased. The deviation of the interval of tuber dropping to the predetermined interval was least at the tempo of dropping most smoothly.
4. The deviation of the plant spacing within the row to the predetermined spacing at dropping, sprouting and harvest was larger in the plots planted at the tempo of dropping too fast than the others. In the plots planted at the tempo of dropping smoothly and too slowly, the coefficient of variance of these plant spacing were within the range of 20-40% of the predetermined one and if the tempo of dropping became slower the coefficient of variance was not lowered.
5. The potato yieldwas not lowered in the plots planted at the tempo that the plant number per ha did not decrease, and the upper limit of this tempo was estimated at 0.5sec.
6. From the difficulty of the motion and accuracy of the results of the operation, it was concluded that the optimum tempo of dropping was 0.6sec. and it was the rhythmically movable tempo of left hand.
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