On the shape and size of optimum grip for a portable machine in forestry on the basis of physiological burden
1992
Fushimi, T. (Ehime Univ., Matsuyama (Japan). Coll. of Agriculture) | Uesugi, K.
This study was performed to develop a set of data that provide guidance for determining size and shape characteristics of a handle grip of portable machine used in forestry. On the first experiment, subject was applied turning force to right or left hand with each member of a set of ten experimental grips that systematically varied in size of circular diameter. Ten diameter sizes were included in the study 25, 27, 29, 31, 33, 35, 37, 41, 45 millimeters. On the next experiment, subject took a weight with grip in his hand. On loaded condition, subject's physiological burden were observed with heart-rate and electromyography of muscles. The resisting fore at handle grip against the constant value of turning force becomes lower in inverse proportion to the increase of circular diameter of grip. But the decreasing value of subject's physiological burden was converted to increase with the diameter increase over some optimal value. This exchanging point of physiological burden consequently showed the optimum diameter ranges of grip, that were 31-35 millimeters. And then, these diameters were selected out of ten grips with questionnaire of self-consciousness, too. Considering materials, torque, weight and comfort with continuous holding, the polygonal 31-35mm grips are recommended for portable machine used in forestry. All corners and points of grips, rounded for best performance and comfort
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