Modelling of stiffness variability of skeleton sled on inclined ice plane

Abstract

This paper continues the previous research for the sliding winter sports taking place on the Bobsleigh and Luge Track. The competition in winter sports is severe. On the ice track of 1200-1500 meters teams struggle to improve their finish time for one hundredth of a second, and often even for one thousandth of a second. Therefore, on the ice track the slightest improvement of the equipment slideability provides the competitive advantage to the team. The slideability could be improved by the right adjustment of the skeleton sled runner stiffness. This research provides analysis of skeleton sled runner slideability depending on the runner stiffness specifically on the inclined ice plane. To perform the analysis of the motion, first the two dimensional model of the sledge was created. In this model the sledge runner was viewed as on object of 5 elements. The connections of the elements are modelled as joints made of springs to allow small rotational movement. Thus, the model had eight degrees of freedom (DOF)-three DOF for the luge and the driver, and five DOF for the rotation of the joints. For the analysis the physical properties of the connection-elasticity of the spring and damping of the oscillations were discussed. The drag force resulting from the friction with the air affects damping and is in the model included. The modelling results were compared to the site experiments performed on Bobsleigh and Luge Track "Sigulda", Latvia. The track was 23.7 m long. In the experiments the stiffness of the runners was subject of variability. In addition, the temperature of the air, humidity of the air and the temperature of the ice on the track were measured. The results of the experiments and modelling revealed that there was a non-linear relationship between the change of the runner stiffness and velocity. The wavy shapes depend on the characteristic of material elasticity. Also the sliding friction frequency depends on the stiffness and runners profile.