Relative Dynamic Displacements within a Trunk Shaker Clamp
ABSTRACT DYNAMIC displacements of a commercial trunk shaker and the trunks of three sizes of '^Montmorency' cherry trees were simultaneously measured at shaking frequencies of 9 Hz and 16 Hz. Free shake displacement (no tree in the clamp) was also measured. Start-up and shut-down transients created displacements 2.5 times greater than displacements at steady-state. Relative amplitude difference between shaker and trunk position ranged from 3 to 8 mm for young trees; these displacements must be absorbed in the clamp system or the tree bark. Combined with corresponding acceleration values in a second-order, single-of-freedom vibration model, the transient relative displacements indicated stress values on the bark of young trees which may exceed tolerable limits.