Development and evaluation of two picker reels for an experimental vegetable harvester

The purpose of this investigation was to evaluate a conical shaped, steel tine picking reel mounted in an experimental helical vegetable harvester for effectiveness in detaching snap beans. Two double helix picking reels, each of a different pitch, were tested. One reel had a pitch of three inches, and the other had a pitch of four inches. Laboratory tests were conducted to determine the effects of helix speed, reel speed, and reel pitch on picking efficiency and pod damage.

The average picking efficiency was 83.2 percent. An average of 31.8 percent of the picked pods were broken and an average of 16.0 percent of the pods were picked in clusters. Statistical analysis of the test results showed that only the interaction between reel speed and reel pitch was significant for the responses percentage of pods broken and percentage of pods picked in clusters.

High speed motion picture films of the picking action were studied to determine the mode of pod detachment. Four modes were observed and grouped into two classes depending on condition of the detached pods. The acceptable group consisted of pods that the tines detached at either the pod-pedicel junction or at the pedicel-plant stem junction. The films indicated pods of the unacceptable group were either broken when one tine accelerated a pod into a second tine or when a tine contacted the pedicel and created tensile stresses within the pod thus removing part of the pod with the pedicel. The helical coil was observed to support the plant stalk and act on it to aid in pod detachment through application of a force opposite to the picking tine force.