Previous work on in-situ calibration of force platforms has focused primarily on behaviour under static loading conditions. The prototype described in this paper is a dynamic system, designed to approximate the loading profile generated during human gait. The design, construction and performance of an oscillating lead pendulum assembly is described; including three-dimensional visual performance assessment and rigorous multi-component force analysis. No significant difference was found between measured data and a theoretical profile for vertical force and angular displacement. A significant difference was found for the horizontal force component. The authors believe that further development of this prototype model will allow accurate routine dynamic calibration.