Effects of wheel design on the torques applied to large hand wheels

Abstract

This paper reports the results of an experiment to evaluate the isometric wheel torque strength of human subjects using four different hand wheel designs. Three of the wheels were new designs, while the fourth was a wheel currently used on many railroad car hand brakes. The three new designs were a cylindrical tube (4.3 cm in diameter), a cylindrical tube (2.5 cm in diameter) with spheres mounted along the edge, and a circular zig-zag design. The strength capabilities for 12 male and 12 female subjects were measured using two methods. The first method used a three-second average during a six-second sustained exertion following recommended isometric strength testing procedures. The second used the maximum value for a trial that had subjects slowly increase the magnitude of their exertion to a maximum and then relax. Results showed that the torque generated by the subjects was highest for the zig-zag design, followed in order by the wheel with the spheres, the cylindrical wheel, and the standard wheel; average torque values were 156 Nm, 118 Nm, 106 Nm, and 101 Nm, respectively. Further, the hand forces generated by the subjects during the wheel-turning task indicate that not only were subjects able to generate more wheel-turning torque using the new wheel designs, but they were also more efficient in producing this torque.