Vibrational analysis of a flexible bicycle stem during indoor in-vivo cycling on a two rollers servohydraulic test bench

Introduction. Comfort is an important parameter correlated to bicycle usability and depends deeply on vibrations and human perception. The most of vibrations is generated by the interaction between road and wheels and sensed at hands and seat [1][2]. Different approaches were used to evaluate the in-vivo behaviour of different bycicle postures and components, including vibrational excitation applied to the wheels [2],[3]. The present work presents results obtained from a full scale roller bench test [3] on a flexible stem supposed to improve the riding comfort. External vibrations were applied to both wheels using a two rollers servohydraulic test bench [3] with a random load function generator corresponding to road types defined by the ISO 8608: 2016. Methods. A specific flexible stem (Shockstop produced by Redshift), designed to reduce accelerations transmitted to the hands by selectable elastomeric shock-absorbing inserts (SOFT, MEDIUM, HARD), was compared to a standard rigid stem (Deda zero 100 Alluminum). Three road profiles (A= Airport runways and super highways; B= Normal pavements; C= Unpaved and damaged roads, ISO 8608: 2016) were applied to the cyclist in two postures (Posture1-Hands on upper handlebar brakes, Posture2-Hands on handlebar drops). Results. Table 1 reports the Comfort index and Transmission index percent variations respect to the RIGID stem (Red cells represent lower performance). As it can be seen, based on CI the Flexible stems seems to improve comfort in both postures and stem hardness with lower roas harshness, but gives not favourable results in Posture 1 with road C. The transmission index TI seems to give opposite results than the CI in Posture 1, whereas shows better agreement in posture 2. Conclusions. The study shows the suitability of the roller test bench for the stationary analysis of comfort related component in bicycle. The significance of the two parameters CI and TI deserve comparison with a larger number of subjects and their subjective evaluation

Instrumentation of sprint and long jump tracks of an indoor athletics field to study athletes’ performances

Introduction: The in-depth study of the performances of athletes is crucial to evaluate and improve their technique. However, collecting representative data is not trivial, as several factors could affect the measurements. Laboratory measurements can lack in realism (artificial environment, athlete’s lack of challenge), whereas data collected in-field using on-board devices can be influenced by the instrumentation itself (weight, encumbrance) [1-2]. The aim of this work is the design of an instrumented track, which will allow to collect kinematic and kinetic data of able bodied and paralimpic athletes in their natural environment, ensuring that the influence of the sensory apparatus is negligible. Methods: The instrumentation set-up of the indoor athletics track of Padova (Padova, 35136, Italy) is represented in the plan view of figure 1a. Seven 60x90 cm and two 40x60 cm force platforms (AMTI, BMS600900 and BMS400600) will be installed following the disposition depicted in figure 1b on the eighth lane of the sprint track, leading to a total of 6.9 metres of force sensing lane. The two smaller force platforms will be installed side-by-side to allow the possibility of mounting one single starting block on each force transducer to collect separate right and left ground reaction forces during the starting phase of sprinting. An additional 60x90 cm force platform will be installed on the long jump track at 1.6 metres from the sand pit in order to collect the last step of the athlete before the flight phase of the long jump (figure 1c). Kinematic data will be collected using 10 optoelectronic motion capture cameras (Vicon, Vantage5), which will be installed on a double portal structure made of aluminium trusses with an overall size of 13 x 7 x 3.5 metres (length x width x height). The structure size allows more than one athlete to run simultanesously, in order to recreate the “challenge effect” typical of official races. Compared to other motion capture mounting solutions, such as using tripods to support each individual camera [3], the use of this single support structure offers the advantage of allowing to rigidly translate the motion capture calibrated volume in different part of the athletics field using wheels. This feature reduces drastically the set-up time of the motion capture system, particularly when the data collection focus has to be moved between the sprint and the long jump area. Moreover, this structure allows to avoid the presence of any cable on the track, as wires will pass through the trusses and descend via the vertical columns. Results and discussion: The design of the sensorized athletics track is complete and the installation of the instrumentation will take place in the next few months. This track will allow to collect insightfull in-field data regarding able bodied and paralimpic athletes performances outside the laboratory environment. Examples of these data will be presented in June at the ISEA 2022 conference

STIFFNESS COMPARISON OF RUNNING PROSTHETIC FEET OF DIFFERENT CATEGORIES AFTER BENCH TESTING

The purpose of the work is the comparison of stiffness properties of Running Prosthetic Feet (RPF) for transtibial amputee athletes after the introduction of test methods to collect and analyse their Load-deflection curves. The study explores the effect of the orientation of the socket (ϑG) with respect to ground during a load cycle.The three Ossur feet Cheetah Xtreme Category 4th, 5th ,6th underwent extensive testing on a multi-component test bench. Results show that the unit interval between categories does not matches with the interval in terms of equivalent stiffness Keq introduced as synthetic stiffness parameter

TOWARDS THE DEVELOPMENT OF BENCH TESTING FOR LOWER-LIMB PROSTHETIC SOCKETS FOR SPORT APPLICATIONS

Prosthetic sockets are the bespoken part of lower-limb prostheses. Knowledge about the mechanical properties of sockets is essential to ensure patient safety and comply with current medical device regulations. This includes sockets designed for sport activities. Unfortunately, the literature is extremely limited and contradictory as described in a recent systematic review. The aim of this study was to initiate a research activity aiming to design a mechanical bench system for socket testing and perform a comparative analysis of the ultimate strength of alternative socket layups. Results highlight substantial differences in the maximum loading at failure, stressing the importance of increasing the knowledge about socket mechanical properties to support prosthetists provide reliable and safe products to patients and athletes

Construction of a Test Bench for the Development of Experimental Methods for the Reproduction of Road Induced Vibrations During Indoor Cycling

Il lavoro svolto si è focalizzato sul concepimento e sulla costruzione di un banco prova per la riproduzione delle vibrazioni indotte dalle diverse tipologie di strade, su una bicicletta. Dopo la fase progettuale e realizzativa e dopo aver collaudato e funzionalità del banco prova il lavoro si è focalizzato su test comparativi fra uno stelo per manubrio rigido e uno ammortizzato al fine di comparare le grandezze fondamentali quali funzione di trasferimento, accelerazioni e Confort index

Static strength of lower-limb prosthetic sockets: An exploratory study on the influence of stratigraphy, distal adapter and lamination resin

Knowledge about the mechanical properties of lower-limb prosthetic sockets fabricated with resin infusion lamination and composite materials is limited. Therefore, sockets can be subject to mechanical failure and overdimensioning, both of which can have severe consequences for patients. For this reason, an exploratory study was conducted to analyze the effect of stratigraphy (layup and fibers), matrix (resin) and mechanical connection (socket distal adapter) on socket static strength, with the objectives of: 1) implementing a mechanical testing system for lower-limb prosthetic sockets based on ISO 10328:2016 and provide the mechanical design of the loading plates, 2) apply the testing system to a series of laminated sockets, and 3) for each type of distal adapter, identify the combinations of stratigraphy and matrix with acceptable strength and minimum weight. Twenty-three laminated sockets were produced and tested. Sixteen met the required strength, with ten exhibiting an excessive weight. Among the remaining six, four combinations of stratigraphy and resin were identified as best option, as they all overcame ISO 10328 P6 loading level and weighted less than 600 g. The selected stratigraphies had limited or absent amount of Perlon stockinettes, which seems to increase weight without enhancing the mechanical strength. Sockets based on Ossur MSS braids and connector show the best compromise between strength and weight when the amount of carbon braids is halved