Abstract
This study models the human power hand tool operator as a dynamic single degree of freedom mechanical system for predicting the response to torque reaction forces produced by rotating spindle tools such as nutrunners or drills. The model represents the hand as mass, spring and damping elements that are dependent upon the posture used and the individual operator. It therefore considers tool shape (i.e., in-line, pistol, right angle), tool orientation (i.e., horizontal or vertical), horizontal location from the ankles, and vertical location from the ankles, in addition to gender. The apparatus used to quantify these elements measured the vibration frequency and amplitude change after an initial disturbance to a defined mechanical system. Twenty-five subjects (13 female, 12 male) participated in the experiment. A repeated measures design tested the effects of gender, work location, tool shape, and torque direction on the three passive elements in the model. The results show that stiffness for pistol grip and right angle handle used on a horizontal surface changed by 12% ( p<.01) and inertial mass parameter changed by 29% ( p<.001). Horizontal location was a significant factor for stiffness and inertial mass parameter for all four handle conditions.
Published Version
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