Influence of hand grip on the vibration amplitude of chain-saw handles.
NIOSH 1977 Apr; :179-186
The vibration of the handle of a typical antivibration chain saw is studied and the salient features of the interaction between the hand and the handle are described. Significant differences occurred between the results of tests under nominally identical conditions. Isolated measurements of vibration, with the sawyer subjectively optimizing the operation, are considered to result in differences in amplitude of a factor of four. Extremes of cutting force and engine speed cannot account for the range of vibration amplitudes seen. Employing various types of grips, it is shown that changes in contact pressure between the hands and the handles cause changes in vibration amplitudes similar in magnitude to those observed during normal cutting. It is concluded that the mechanisms dominating the interaction between the hand and the handle are the inherent nonlinear elastic properties of flesh that are dependent on its surface indentation, the surface area and mass of flesh effectively coupled to the vibrating surface, and the redistribution of the normal modes of the handle favoring those with small displacements at positions occupied by the hands. Use of a miniature transducer located between the hand and the handle is recommended in future studies as well as representative cutting and grip forces. For product evaluation, these variables are considered best controlled by using a dynamometer and mechanical simulation of the hands.
Chain-saws; Power-tools; Industrial-equipment; Analysis; Procedures; Work-performance; Woodcutters; Measurement-methods; Vibration-control;
Proceedings of the International Occupational Hand-Arm Vibration Conference, NIOSH (Paper presented at Cincinnati, Ohio, October 28-31, 1975), Cincinnati, Ohio, DHEW (NIOSH) Publication No. 77-170