A HAND-HELD MECHANICAL DEVICE FOR TARGETED BLOSSOM THINNING IN SWEET CHERRY
Managing crop load of commercial tree fruit species, such as sweet cherry (Prunus avium L.), apple (Malus domestica Borkh.), pear (Pyrus communis), by thinning bloom, is a common practice used to produce larger and better quality fruit. Targeted mechanical thinning may be preferential compared to current chemical and manual strategies and decrease production costs. This study aimed to develop a hand-held mechanical thinning device suitable for targeted thinning blossoms on sweet cherry trees regardless of tree architecture. Research prototypes of different configurations have been designed, fabricated, and tested in laboratory and in orchards. Field testing results from both research and commercial orchards verified the efficacy of these prototypes as blossom thinners - flowers were removed effectively with a range of configurations. I conducted a parametric study that investigated a range of configurations for thinning spindle evaluating the torque, speed variation and power consumption under laboratory conditions based on a developed platform and data acquisition system, which simulated different blossom thinning conditions in the orchard and let desired parameters measurable. Power consumption and torque variation to string stiffness were obtained to provide crucial information assisting motor and battery sizing for product commercialization. Another parametric study for evaluating flower removal percentage in relation to a set of key operation parameters - spindle rotating speed, swiping speed and thinning distance - was conducted in sweet cherry orchard. Results indicated that stiffness of thinning strings affected the controllability of flower removal percentage. Flower removal percentage could be better controlled when strings that were less rigid were utilized. Of all studied parameters of the thinning spindle, rotating speed of the thinning spindle was the most important and was related positively to flower removal percentage.