Effect of Kinematic Index and Rod Shape on Performance of an Onion Rod Digger

The most important factors affecting onion rod digger performance are the shape of the rod and the ratio of peripheral speed to translational speed (kinematic index). This study investigated the effect of these parameters on nthe performance of a rod onion harvester using a split-block randomized complete-block design with three replicates for three rod shapes (round, hexagonal, rectangular) and rod kinematic indices of 0.16, 1, 1.15, 1.30 and 1.44. In each experiment, the draft force and drawbar power for the rod and complete harvester, rotational torque and total required power for the rod, and the percentage of damage were determined. The results showed that rod shape had no significant effect on draft force, drawbar power (averaging 10571 N and 5285 W, respectively) and percentage of damage (averaging 1.98%); maximum torque and rotational power (averaging 64 N.m and 2394 W, respectively) were observed for the rectangular shaped rod. The maximum values for draft force and drawbar power (12018.7 N and 6009.3 W, respectively) were in the 0.16 kinematic index; the minimum values (9645.2 N and 4822.2 W, respectively) were in the 1.15 kinematic index. Maximum torque and rotational power (85 N and 3327.8 W, respectively) occurred for the rectangular shaped rod in the 0.16 and 1.44 kinematic indices, respectively. The results showed that, for minimum onion damage (priority) and power consumed, the best kinematic index was 1.15. The results of this research show that the rectangular rod shape in hard soil and the round rod shape in soft soil facilitated penetration; both occured in the 1.15 kinematic index. The total consumed power was from 3.5 to 3.8 KW per m of working width.