19 An Innovative Solution for Carving Ski Based on Retractile Blades 205 – fsD50Hz – RangeD2g • An uniaxial accelerometer 333B30 by PCB Piezotronics positioned on the right ski, with: – fsD2,048Hz – RangeD50g • A triaxial accelerometer 356A02 by PCB Piezotronics positioned on the left ski, with: – fsD2,048Hz – RangeD500g The aim of these tests were to verify the behavior of the new solution on the snow as well as compare its performance to the classic skis. 19.3.3 The Experimental Results The data gathered during the test have been analyzed and sorted in the following graphs, which show the performances of both the modified and classic skis measured by the GPS and the accelerometer on the athlete’s back. The data gathered by the accelerometers positioned on the skis are not considered in this preliminary study and they will be taken into account in a following analysis. The results of the two tracks have been properly overlapped to easily compare the performances. As already mentioned above, the track is 1,200 m long and has an altitude gap of 135 m. The graphs in Fig. 19.7 bring out some similarities between the performance with the prototypes and with the classic skis. In both cases the track has been executed in about 100 s, and in terms of speed both the tests present an average speed of 43 km/h and a maximum speed of about 60 km/h. Moreover, both the graphics clearly show how the acceleration with the prototypes is lower in the first 20 % of the track (belonging to the first downhill). The graphs of the accelerations (Fig. 19.8) confirm the similarity of performance between the modified and the classic skis. In the longitudinal and vertical acceleration graphs it is possible to see how, in both the tests, at the very start of the track the gravitational acceleration is applied to the vertical component, while after the first 100 m and until the end of the performance it’s transferred to the longitudinal component because of the different position that the skier assumes while going down. a b Fig. 19.7 The time histories (a) and the space in % histories (b) of the speed measured by the GPS. The solid line belongs to the test 2 and the dashed line belongs to the test 4, just as before
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