Design, construction, modeling and testing of a controllable inertial mass tree shaking device

Decline of tree life in Michigan cherry orchards has prompted research in methods for eliminating damage caused by trunk shaking devices. Commercial trunk shakers generally exhibit large uncontrolled vibrations at startup and shutdown. Excessive displacements are known to cause nonvisible bark damage. A controllable tree shaker was designed, constructed, modeled, and tested in an effort to produce a device that would not cause visible or nonvisible bark damage. Independent control of frequency, amplitude, and direction was possible with this shaker design.;Two different vibrational models were used in the research. A multiple degree-of-freedom model was used to predict the shaker behavior while shaking trees with different trunk diameters. Qualitative agreement with the field tests was good. Quantitative agreement was also satisfactory, as peak-to-peak amplitudes were within 30% of the actual values.;A single degree-of-freedom vibrational model was used to optimize the size and shape of the shaker eccentric masses. Size constraints dictated that the masses fit in a 305 mm circle of rotation. Rectangular- and pie-shaped sections were considered. Although rectangular sections have a greater eccentricity, pie-shaped sections were found to create greater shaking forces due to their greater mass. Pie-shaped sections with included angles of 120 degrees were therefore chosen for use in this shaker.;The shaker frame was composed of aluminum plate and constructed using common machine shop tooling and equipment. The shaker was hung by chains from a steel carrying frame mounted on an agricultural tractor. Shaker power was provided by hydraulics. High pressure hydraulic hoses allowed isolation of the shaker from its support frame.;Field tests were conducted to determine if the shaker met amplitude and frequency criteria for fruit removal given in the literature. The results indicated that the shaker was indeed capable of removing fruit from cherry trees. Displacements of about 40 mm were created when shaking a tree with a trunk diameter of 140 mm at 15 hz.;The trunk shaker developed through this research delivered a controllable shaking force and shows promise for alleviating bark damage in cherry trees.