Wheel Turning Strength for Four Wheel Designs

Abstract

This paper reports the results of an experiment to evaluate the isometric wheel turning strength of 12 male and 12 female subjects using four different wheel designs. Three of the wheels investigated were new designs developed specifically for this study, while the fourth was a wheel currently used on many railroad car hand brakes. The three new designs considered 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. Strength data were collected using a mock-up of the ladder and platform arrangement found on most railroad hopper and box cars. The task simulated the final tightening exertion required to secure railroad car hand brakes. Strength capabilities were measured using two methods: 1) a three second average during a six-second trial; 2) the peak reached on a separate trial in which subjects did not sustain an exertion. 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 191 Nm, 147 Nm, 132 Nm, and 95 Nm, respectively. The average strength values (three-second average) for six-second maximum exertions produced lower average torque values (122 Nm) than the ramp to maximum exertion (161 Nm).