Abstract
The purpose of this study was to evaluate the use of a standard two-wheel cart to transport loads over a curb. This was done through biomechanical (static and dynamic) and psychophysical evaluations of industrial males. The biomechanical study (n=4) involved altering the amount of weight placed on the cart, the diameter of the wheels, and the load center of gravity. For the heavier load of 68 kg (150 lb), the forces exerted on the force plates (p=0.0001) and the dynamic moments (P=0.0001) at the shoulder, hip, L5/S1, and knee increased. In addition, the static moments at the elbow (p=0.0001), hip (p=0.0001), L5/Sl (p=0.0001), and knee (p=0.0260) increased for the heavier load. The accelerations at the shoulder (p=0.0356) and elbow (p=0.0090) also increased for the heavier load. For the smaller diameter wheel, the forces exerted on the force plates (p=0.0027), and the dynamic (p=0.0143) and static (p=0.0014)moments at the knee increased. For the longer distance between the load center of gravity and the axle, the accelerations at the hip (p=0.0442) and L5/S1 (p=0.0145) as well as the dynamic (p=0.001 1) and static (p=0.0008) moments at L5/S1 increased. The psychophysical study (n=20) required participants to determine the maximum load each was comfortable having on the cart to tilt the cart back and to move the cart over the curb without excessive strain. The maximum weight to tilt back the cart was 225.8 kg (500 lb), and the minimum was 158.8 kg (350.1 lb). The average weight of the load the worker was willing to transport with the cart over the curb was 101.8 kg (224.4 lb), which is roughly half of the average load of 203.0 kg (447.5 lb) to tilt the cart back. This study concludes that moving a two-wheel cart over a curb is a dynamic activity. Recommendations include use of a wheel larger than 20.3 cm (8 in) and redesign of the runner on the cart. Also, stack loads up until it is necessary to stack them out on the tongue extension and place heavier items closer to the cart axle.
King, Rebecca Lynn (1997). Biomechanical and psychophysical evaluation of using a two-wheel cart to transport loads over a curb. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1997 -THESIS -K56.