Masters Theses

Date of Award


Degree Type


Degree Name

Master of Science


Biomedical Engineering

Major Professor

Bobby L. Bledsoe

Committee Members

John J. McDow, David L. Coffey


The purpose of this investigation was to modify and evaluate an open-helix mechanism for harvest of bell peppers. The mechanism was modified and laboratory tests were conducted to determine the effect of different helix inclination angles and helix linear speeds on the harvesting efficiency.

The mean harvesting efficiency was 92.0 percent, and the mean percentage of single peppers harvested was 49.9 percent. Statistical analyses of the test results showed that there was a significant difference in the percentage of single peppers harvested and peppers harvested attached to stems for different helix inclination angles. Helix inclination angles tested were 20, 25, and 30 degrees. Helix linear speeds tested were 100, 105 and 110 percent of simulated ground speed. Helix linear speed had no significant effect on the response variables.

High speed motion picture films of the picking action were studied to determine the method of pod detachment. It was observed that fillets in the rear of the helix cage assembly striking stems at a distance below the point of attachment of the pepper caused the stem to fail, resulting in the harvest of peppers still attached to portions of plant stems. The coils of the helix cage assembly striking the pepper fruits and causing bending, twisting and axial (pulling) forces in the pedicel resulted in the detachment of single peppers. Also the stem of the pepper plant being struck near the point of attachment of a pepper and accelerated away from the pepper resulted in detachment of single peppers.

In these tests, the best results were obtained with a helix inclination angle of 30 degrees and with any of the helix linear speeds tested. A future prototype machine should have a longer helix cage assembly, and have the rear of the helix cage assembly as high above the ground as the tallest pepper plants.

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