1,721,026 research outputs found
Comparison of the Aerodynamic Performance of Five Racing Bicycle Wheels by Means of CFD Calculations
Full text linkAerodynamic drag is the main source of losses in cycling so improving the bicycle aerodynamic is a fundamental key factor to increase the performance. The aim of this research is to evaluate and compare the aerodynamic performance of racing bicycle wheels by means of CFD RANS numerical models: it is based on a previous work that reported the development of the numerical model. The aim of this work is to assess the capability of CFD RANS simulations to predict the aerodynamic performance of modern racing bicycle wheels. Drag and side forces are resolved over the range of different yaw angles
Biaxial Testing and Analysis of Bicycle-Welded Components for the Definition of a Safety Standard
No full textThis paper presents the experimental evaluation of the fatigue behaviour of welded components under non-proportional variable amplitude biaxial loads. The study was undertaken on welded mountain bike handlebar stems, which were different in terms of geometry and technology and tested with load histories that were reconstructed and accelerated from recorded field data. Loads measured in the field were decomposed into bending and torsional components; a synchronous Peak-Valley counting, a spectrum inflation technique, a spline interpolation and a final amplification were applied to the measured signals in order to obtain test drive signals with the correct content of biaxial non-proportional loadings. After evaluation of the bending and torsion load-life curves of components under constant amplitude fatigue, the resulting data from biaxial variable amplitude fatigue tests were analysed in order to evaluate the damage contribution as a result of the two load components and an equivalent simplified two-stage constant amplitude fatigue test was proposed to the working group ISO/SC1/TC149/WG4
Torsion and bending loads on a ski-touring boot shell during uphill and downhill skiing
Full text linkSki touring is an established winter activity that has experienced a recent increase in popularity. Differently to alpine skiing, skier gains altitude without lifts, thus equipment weight must be minimized. Nevertheless, structural properties of the equipment, such as ski boots, must be adequate to withstand skiing loads. Several studies provided data on flexural stiffness of alpine ski boots in bench and field tests. The present study focused on the torsional properties of ski-touring boots. Indeed, touring bindings design implies a higher torque transmission to the front piece which induces a torsional load throughout the shell. To conduct the study, we prepared a ski-touring boot with strain gage bridges, and we performed bench tests to determine the stiffness of the boot and the bridge sensitivity. We also positioned and calibrated strain gage bridges to measure bending load in the shell and axial load in the ski/walk lever placed between shell and cuff of the boot. Then, we conducted a field test measuring the loads during a ski-touring trip including ascent and descent. Bench tests evidenced linearity of the torsion sensor, and a variation of stiffness depending on dummy leg absence/presence and boot buckle setting. Field tests showed torque ranges of 17 Nm in climbing and of 27 Nm in skiing. Bending moment range on the boot shell was of 150 and 228 Nm, respectively. Maximum force on the ski/walk mechanism reached 570 N. Results could be useful to test ski-touring boot performances and to optimize their design
The New Muscovite cultural history : a collection in honor of Daniel B. Rowland, édition V. Kivelson, K. Petrone, N. Shields Kollmann, M. S. Flier
No full textGonneau Pierre. The New Muscovite cultural history : a collection in honor of Daniel B. Rowland, édition V. Kivelson, K. Petrone, N. Shields Kollmann, M. S. Flier. In: Revue des études slaves, tome 82, fascicule 2, 2011. pp. 331-332
The New Muscovite cultural history : a collection in honor of Daniel B. Rowland, édition V. Kivelson, K. Petrone, N. Shields Kollmann, M. S. Flier
No full textGonneau Pierre. The New Muscovite cultural history : a collection in honor of Daniel B. Rowland, édition V. Kivelson, K. Petrone, N. Shields Kollmann, M. S. Flier. In: Revue des études slaves, tome 82, fascicule 2, 2011. pp. 331-332
Development of a test bench for the subjective & objective evaluation of the vibrational comfort of bicycle components
No full textVibrational comfort is one of the most important parameters evaluated by cyclists and it is correlated to the response of bicycle components in combination with the cyclist's characteristics. Vibration transmissibility of wheels and saddles had been recently studied during lab tests using a wooden dummy bottom resting on the saddle and in road tests on an instrumented racing bicycle at different speeds on different surfaces. In this study, a test bench was developed in order to simulate different vibrational inputs to the seatpost from the road surface on a group of real cyclists during steady cycling. The bench is composed by a racing bicycle without wheels, hinged at the front fork axle and sustained by an hydraulic actuator connected to the seatpost. The bicycle is equipped with pedals and chain wheel and a long chain drives another rear wheel fixed to the bench and connected to brake rollers. Three racing bicycle saddles were evaluated by a group of five cyclists after the application of vibrational spectra corresponding to PSDs recorded in the field tests: the magnitude of the transfer function H between the input vertical acceleration at the seatpost and the output acceleration at the pelvis was obtained by two accelerometers. The cyclists were in the meantime asked to fill a questionnaire regarding the perceived comfort of the three saddles during the tests. Initial results showed an encouraging correlation of the subjective ranking of saddles with the corresponding Index of Transmissibility derived from the transfer function H
Review
No full textThe initial keyword review used the conference publication “The Engineering of Sport” for 2012 [11]. This fast turn-around publication serves as a ‘mark in the sand’ of research works that is both early and timely, as a window into the use of sensors. A review of the publication from a decade earlier in 2002 [12] serves to indicate a sense of emerging trends in sensors and their growing popularity
Sensors and wearable technologies in sport: technologies, trends and approaches for implementation
No full textThis book explores emerging trends in wearable sensors for sport and highlights the developments taking place. Drawing on the literature both the approaches and principals for the use of sensors in sport are outlined, and together with references to key works the reader finds this useful in considering such endeavours. The development of wearable technologies is fast paced and accompanying that is an exponential growth in the use and development of computing resources, thus while the review is comprehensive on content not all works can be included and given publication times will inevitably be somewhat dated. The illumination through trends, examples and principles are an aid for anyone considering the use of sensors and wearables in sports
Designing, building, measuring, and testing a constant equivalent fall height terrain park jump
Full text linkPrevious work has presented both a theoretical foundation for designing terrain park jumps that control landing impact and computer software to accomplish this task. US ski resorts have been reluctant to adopt this more engineered approach to jump design, in part due to questions of feasibility. The present study demonstrates this feasibility. It describes the design, construction, measurement, and experimental testing of such a jump. It improves on the previous efforts with more complete instrumentation, a larger range of jump distances, and a new method for combining jumper- and board-mounted accelerometer data to estimate equivalent fall height, a measure of impact severity. It unequivocally demonstrates the efficacy of the engineering design approach, namely that it is possible and practical to design and build free style terrain park jumps with landing surface shapes that control for landing impact as predicted by the theory
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