Clockwise and Counter-Clockwise Twisting Strength in Different Operational Angles on Crown Plane

Abstract

Hand tools can be seen as the extent of human hands. The evolution of hand tools was positively correlated with human development. The hand tools design affects the convenience and safety of human use. The wrenches are the most frequently used hand tools in Taiwan. However, it is lack literatures focus on the twisting force for operating hand tools. To provide reference for the hand tools design, this study surveyed the two twisting forces in five operational angles in crown plane when use wrenches. Eighty volunteer adults (half male and half female) were recruited as subjects. The maximum twisting forces of dominant hand were measured. Palm facing to ground is defined as 0 degree. Hand in supine positions are defined as positive angle and in prone positions are defined as negative angle. The five angles are: 0, 15, 22.5, 30, and 45 degrees. The two twisting forces are: clockwise and counter clockwise in vertical plane. A digital twisting force wrench was used as the measurement apparatus. The twisting forces model was constructed. In the vertical plane, the down force is greater than the up force. The forces in positive angles were greater than that in the negative angles. The force of male is greater than that of female. The results of the study can be reference for research and other hand tools design.