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Abstract
A green bean harvester was designed to enhance the mechanized process for green bean stripping. To develop and modify the existing technology for green bean harvesting, some physical and mechanical properties of two green bean (Phaseolus vulgaris L) varieties Bronco and Contender were studied. The average plant height was 43.79 and 46.66 cm for ’Bronco’ and ’Contender’, respectively. The mean pod detachment force was determined as: 6.57 and 10.68 N for ’Bronco’ and ’Contender’, respectively. While pod placement shows that 36.6 and 54 % of pods on the top, 54.5 and 41 % of pods on the middle and 8.9 and 5 % of pods on bottom of the plant for Bronco and Contender, respectively. The designed harvester consisted of the following functional subsystems, direction unit, stripping unit, concave sheet, brush, hopper, frame and hitching points, transmission mechanism and lifting adjustment wheel. The green bean harvester was tested with three forward speed 1.16, 1.54 and 2.32 km/h, three reel stripping rotating speeds 140, 160 and 180 rpm, and three directing unit tilt angles 25, 30, and 35 degrees. The designed harvester was evaluated technically with respect to assessment criteria: gross harvest efficiency, un-damaged pods percentage, losses percentage, damage percentage and net harvest efficiency. Results obtained from the test showed that the values of gross harvest efficiency, un-damaged pods percentage, losses percentage, damage percentage and net harvest efficiency were 91.48, 81.90, 19.64, 9.56, 80.11% for Bronco variety at the optimum harvesting performance parameters 1.54 km/h, 160 rpm and tilt angle 30 ̊. The actual field capacity of the harvester was 0.153, 0.147 fed/h for Bronco and Contender, respectively. The cost of harvest one ton of green bean by harvester was 440 LE, while the manual cost of one ton was 687.5 LE. The values of economic parameters have satisfied the acceptance rules for the investment in that machine.