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1.
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2.
The primary aim of this study was to compare the rebound characteristics of wooden and composite cricket bats. The rebound characteristics of two 'experimental' bats manufactured from composite material were compared with three English willow bats and one Kashmir willow bat. The bats were tested using a specially designed testing rig, which propelled a 156 g Kookaburra cricket ball at three impact speeds: fast-medium, 67 km x h(-1); fast, 101 km x h(-1); and express, 131 km x h(-1) on to the bats mounted in position so that the ball impacts occurred at the position where the blade of the bats was the thickest. The rebound characteristics of the bats were calculated by measuring the approach and rebound speeds of the ball as it passed through a light beam positioned a short distance away from the point of impact. The statistical software package SAS was used to test for significant differences (p < 0.05) between the average rebound characteristics of the bats. Further, Scheffé's method was used as a post hoc comparison to determine whether differences existed between the composite and willow bats. When the composite and traditional willow bats were compared, the results showed no significant differences between the three average approach speeds, while the composite bats showed significantly smaller rebound speeds and coefficient of restitution at all three approach speeds. Thus, the rebound characteristics of the composite bats were significantly less than the traditionally designed English willow wooden bats and would not enhance performance by allowing the batsman to hit the ball harder, assuming all other factors, such as bat speed, mass distribution and the impact point, were the same for the bats. Further study is required to determine the physical properties of composite and wooden bats to enhance their impact characteristics.  相似文献   

3.
The swing speed of the bat is one of the most important factors affecting the hit-ball speed. Most field studies tend to focus on measuring ball speed, which is easier to measure and quantify than bat speed. For this reason, relatively little data exist describing bat motion in field conditions. The following describes a relatively large swing speed field study involving bats of the same model with nearly constant weight and varying inertia. The study was conducted using right-handed batters on a regulation outdoor field with a live pitcher. Swing speed was measured by tracking markers on the bat with two high-speed video cameras so that the bat markers could be traced in three-dimensional space. The ball motion was tracked using the same high-speed video cameras and a three-dimensional Doppler radar system. Bat swing speed was observed to be proportional to the batter skill level and the normalised swing speed increased with decreasing bat inertia. The bat centre of rotation during impact was close to the knob of the bat. The bats were tested under controlled laboratory conditions using a standardised performance test. The field and laboratory results showed good agreement including the hit-ball speed and the subtle effect of bat inertia on the maximum performance location. The vibrational response of the bats was considered using modal analysis. The maximum performance location was correlated with the node of the first vibrational mode.  相似文献   

4.
A determination of the dynamic response of softballs   总被引：3，自引：3，他引：0  
An apparatus is described for measuring the stiffness and coefficient of restitution (COR) of balls with application to softballs. While standardized test methods currently exist to measure these properties, they do not represent the displacement rate and magnitude that occur in play. The apparatus described herein involves impacting a fixed, solid cylindrical surface (matched to the diameter of the bat) with a ball and measuring the impact force during impact and speed of the ball before and after impact. The ratio of the ball speeds determines the COR, while the impact force is used to derive a ball stiffness. For an example of the contribution of the new ball test, the performance of hollow bats, which is sensitive to ball stiffness, was compared. Bat performance showed a much stronger dependence on the proposed ball stiffness than the traditional measure. Finally, it was shown that to achieve similar conditions between impacts with fixed and recoiling objects, the impact speed should be chosen so that the centre of mass energy was the same in the two cases. The method has application to associations wishing an improved method to regulate ball and bat performance.  相似文献   

5.
There is currently much debate about the safety of the sport of softball. Batted-ball speed and average pitcher reaction time are factors often used to determine safe performance. Batted-ball speed is shown to be the most important factor to consider when determining safe play. Average pitcher reaction time is explained and directly correlated to batted-ball speed. Eleven aluminum multi-wall, three aluminum single-wall and two composite softball bats were tested with mid-compression polyurethane softballs averaging 1721+/-62 N/6.4 mm to represent the relative bat-ball performance for the sport of slowpitch softball. Nine men and six women were chosen for this study out of a test group of over three hundred slowpitch softball players. On average, aluminum bat performance results were within the recommended safety limits established by the national softball associations. However, when composite bats were used, their performance results exceeded the recommended safety limits which can pose a significant safety risk. Using aluminum softball bats, batted-ball speeds ranged from 80 to 145km x h(-1) Using composite softball bats, batted-ball speeds ranged from 146 to 161 km x h(-1). The scientific relevance of this study is to provide performance information that can lead to injury prevention in the sport of softball.  相似文献   

6.
Softballs     
There is currently much debate about the safety of the sport of softball. Batted‐ball speed and average pitcher reaction time are factors often used to determine safe performance. Batted‐ball speed is shown to be the most important factor to consider when determining safe play. Average pitcher reaction time is explained and directly correlated to batted‐ball speed. Eleven aluminum multi‐wall, three aluminum single‐wall and two composite softball bats were tested with mid‐compression polyurethane softballs averaging 1721 ±62 N/6.4 mm to represent the relative bat‐ball performance for the sport of slow‐pitch softball. Nine men and six women were chosen for this study out of a test group of over three hundred slowpitch softball players. On average, aluminum bat performance results were within the recommended safety limits established by the national softball associations. However, when composite bats were used, their performance results exceeded the recommended safety limits which can pose a significant safety risk. Using aluminum softball bats, batted‐ball speeds ranged from 80 to 145 km.h‐1. Using composite softball bats, batted‐ball speeds ranged from 146 to 161 km.h‐1. The scientific relevance of this study is to provide performance information that can lead to injury prevention in the sport of softball.  相似文献   

7.
The sweet spot of a cricket bat for low speed impacts   总被引：2，自引：1，他引：1  
The impact location of a cricket ball on a cricket bat has a large influence on the resulting rebound velocity of the ball. To measure this, a cricket bat was swung in a pendulum motion towards a cricket ball suspended in space. The position of the ball was modified so that it impacted the bat at 24 different positions on the face of the bat. This included six positions longitudinally and four positions laterally. The speed of the bat and each rebound were measured by a radar gun so that the apparent coefficient of restitution (ACOR) could be calculated. Impacts occurring centrally and 1?cm either side of the midline produced significantly higher rebound speeds and ACOR??s than impacts occurring 2 and 3cm off centre (p?<?0.01). Impacts occurring 15?C20?cm from the base of the bat produced the highest rebound speeds (p?<?0.01) and impacts occurring 20?C30?cm from the base of the bat produced the highest ACOR values. Implications for higher speed impacts and game scenarios are discussed.  相似文献   

8.
Differences in interceptive skill between highly skilled and lesser skilled cricket batsmen were examined using a batting task that required participants to strike front-foot drive strokes from a machine-projected ball to a specified target. Task difficulty was manipulated by varying the width of the bat (normal, half, and third width) and target accuracy, and quality of bat-ball contact was monitored along with temporal and sequential elements of the hitting action. Analyses revealed that the highly skilled batsmen were distinguishable from less skilled counterparts by their higher accuracy under the normal and half-width bat conditions, significantly earlier initiation and completion of the front-foot stride, greater synchronization of the completion of the front-foot stride with the commencement of the downswing of the bat, and consistent timing of downswing relative to ball bounce and impact. In keeping with studies of other hitting sports, temporal and spatial coupling of the downswing to ball bounce to help minimize temporo-spatial error at the point of interception appeared critical to skilled performance. Implications for the understanding of interception and for coaching practice are briefly discussed.  相似文献   

9.
New cricket bats need to be ‘knocked in’ prior to use, but just what this process does to the surface fibres of the bat is unknown and unquantified. One quantitative measurement of knock-in is the resultant surface hardness of the bat, and this paper describes knock-in tests to determine the surface hardness following differing durations of knock-in. The design of a cricket bat knock-in machine is first described. This takes the form of a cradle in which a cricket bat can be secured horizontally and then traversed at constant speeds in two mutually perpendicular directions while at the same time being struck with constant force by a cricket ball. The traverses are driven by lead screws, the motors of which can be independently switched on or off. The traverse distance can be varied with adjustable limit switches and relays that reverse the direction of rotation of the lead screws when activated. The cricket ball is attached to a rod that is lifted cyclically by a cam against a coil spring extension, and then allowed to fall under that force to impact on the bat surface. The impact (knocking-in) force was measured by a previously calibrated strain gauge attached to the rod holding the cricket ball. By judicious setting of the limit switches, selected areas of the bat surface were continuously knocked in for periods varying from 1 to 4 hours. After knocking in, the surface hardness was measured in accordance with British Standard 373 using a penetrator designed in accordance with the same standard. Analysis of the load/penetration curves shows an increase in surface hardness with knock duration. Photographs of the cell structure of the surface wood, obtained using a scanning electron microscope, show that under knock-in conditions, the wood cells collapse to form a mesh-like hardened layer which increases in hardness with increase in knock-in duration.  相似文献   

10.
Although technology has now infiltrated and prompted evolution in most mass participation sports, the advances in bat technology in such sports as baseball and cricket have been relatively minor. In this study, we used a simple finite element modelling approach to try to shed new light upon the underlying mechanics of the bat-ball impact, with a view to the future optimization of bat design. The analysis of a flexible bat showed that the point of impact that produced the maximum post-impact ball velocity was a function of the bat's vibrational properties and was not necessarily at the centre of percussion. The details of the analysis agreed well with traditional Hertzian impact theory, and broadly with empirical data. An inspection of the relative modal contributions to the deformations during impact also showed that the position of the node of the first flexure mode was important. In conclusion, considerable importance should be attached to the bat's vibrational properties in future design and analysis.  相似文献   

11.
The game of hurling is ranked as one of the fastest and most skilful field games in the world. It is played by a stick, hurley, made of ash wood and a ball, sliotar, made of a cork core or similar viscoelastic materials. Better standardisation of the game equipment requires analysing impacts to quantify precisely the effect of variations in equipment design on the resultant impact force at low and high striking speeds. Therefore, the purpose of the present study was to use a high-speed camera to (1) characterise the impact dynamics in term of impact force magnitude and duration, and (2) investigate whether a relationship exists between the game equipment and the magnitude of the impact force. An air cannon unit (ACU) test rig was set up to cause the sliotar to strike the hurley at predetermined speeds. A high-speed camera operating at 12,500 frames per second (fps) was used to capture 32 experimental impacts covering a range of sliotar and hurley brands, impact locations and impact speeds. The factor ??sliotar brand?? was identified as the most significant factor for the impact force among other main factors and two-factor interactions at a constant speed and it had a significant effect with up to 27?% difference between sliotar brands. It was demonstrated that, at higher impact speeds, the force?Cdeformation curves of the sliotar brands varied significantly, even though similar force?Cdeformation curves have been reported at quasi-static compression and similar COR values at low impact speeds using the standard free-drop test. This is the first known study to characterise the unique, highly non-linear and anisotropic sliotar?Churley impact using high-speed camera technology. It highlights the need for a tighter standard for sliotar materials and manufacturing to increase uniformity between different brands and strongly suggests that the standard free-drop test is not sufficient to characterise and compare game equipment.  相似文献   

12.
Three-dimensional kinematic data of bat and ball were recorded for 239 individual shots performed by twenty batsmen ranging from club to international standard. The impact location of the ball on the bat face was determined and assessed against the resultant instantaneous post-impact ball speed and measures of post-impact bat torsion and ball direction. Significant negative linear relationships were found between post-impact ball speed and the absolute distance of impact from the midline medio-laterally and sweetspot longitudinally. Significant cubic relationships were found between the distance of impact from the midline of the bat medio-laterally and both a measure of bat torsion and the post-impact ball direction. A “sweet region” on the bat face was identified whereby impacts within 2 cm of the sweetspot in the medio-lateral direction, and 4.5 cm in the longitudinal direction, caused reductions in ball speed of less than 6% from the optimal value, and deviations in ball direction of less than 10° from the intended target. This study provides a greater understanding of the margin for error afforded to batsmen, allowing researchers to assess shot success in more detail, and highlights the importance of players generating consistently central impact locations when hitting for optimal performance.  相似文献   

13.
Although technology has now infiltrated and prompted evolution in most mass participation sports, the advances in bat technology in such sports as baseball and cricket have been relatively minor. In this study, we used a simple finite element modelling approach to try to shed new light upon the underlying mechanics of the bat-ball impact, with a view to the future optimization of bat design. The analysis of a flexible bat showed that the point of impact that produced the maximum post-impact ball velocity was a function of the bat's vibrational properties and was not necessarily at the centre of percussion. The details of the analysis agreed well with traditional Hertzian impact theory, and broadly with empirical data. An inspection of the relative modal contributions to the deformations during impact also showed that the position of the node of the first flexure mode was important. In conclusion, considerable importance should be attached to the bat's vibrational properties in future design and analysis.  相似文献   

14.
A comparative study of baseball bat performance   总被引：2，自引：2，他引：0  
The results of a comparative study of five aluminum and one wood baseball bats are presented. The study includes an analysis of field data, high-speed laboratory testing, and modal analysis. It is found that field performance is strongly correlated with the ball–bat coefficient of restitution (BBCOR) and only weakly correlated with other parameters of the bat, suggesting that the BBCOR is the primary feature of a bat that determines its field performance. It is further found that the instantaneous rotation axis of the bat at the moment of impact is very close to the knob of the bat and that the rotational velocity varies inversely with the moment of inertia of the bat about the knob. A swing speed formula is derived from the field data and the limits of its validity are discussed. The field and laboratory measurements of the collision efficiency are generally in good agreement, as expected on theoretical grounds. Finally, the BBCOR is strongly correlated with the frequency of the lowest hoop mode of the hollow bats, as predicted by models of the trampoline effect.  相似文献   

15.
The influence of moment of inertia on baseball/softball bat swing speed   总被引：1，自引：1，他引：0  
The speed at which a player can swing a bat is central to the games of baseball and softball, determining, to a large extent, the hit speed of the ball. Experimental and analytical studies of bat swing speed were conducted with particular emphasis on the influence of bat moment of inertia on swing speed. Two distinct sets of experiments measured the swing speed of colege baseball and fast-pitch softball players using weighted rods and modified bats. The swing targets included flexible targets, balls on a tee and machine pitched balls. Internal mass alterations provided a range of inertial properties. The average measured speeds, from 22 to 31 m s−1, are consistent with previous studies. Bat speed approximately correlates with the moment of inertia of the bat about a vertical axis of rotation through the batter's body, the speed generally decreasing as this moment of inertia increases. The analytical model assumes pure rotation of the batter/bat system about a vertical axis through the batter's body. Aerodynamic drag of the batter's arms and the bat is included in the model. The independent variable is bat moment of inertia about the rotation axis. There is reasonable agreement between the model and the measured speeds. Detailed differences between the two suggest the importance of additional degrees of freedom in determining swing speed.  相似文献   

16.
To assess ball impact force during soccer kicking is important to quantify from both performance and chronic injury prevention perspectives. We aimed to verify the appropriateness of previous models used to estimate ball impact force and to propose an improved model to better capture the time history of ball impact force. A soccer ball was fired directly onto a force platform (10 kHz) at five realistic kicking ball velocities and ball behaviour was captured by a high-speed camera (5,000 Hz). The time history of ball impact force was estimated using three existing models and two new models. A new mathematical model that took into account a rapid change in ball surface area and heterogeneous ball deformation showed a distinctive advantage to estimate the peak forces and its occurrence times and to reproduce time history of ball impact forces more precisely, thereby reinforcing the possible mechanics of ‘footballer’s ankle’. Ball impact time was also systematically shortened when ball velocity increases in contrast to practical understanding for producing faster ball velocity, however, the aspect of ball contact time must be considered carefully from practical point of view.  相似文献   

17.
In this study, we develop a finite element model to examine the oblique soccer ball bounce. A careful simulation of the interaction between the ball membrane and air pressure in the ball makes the model more realistic than analytical models, and helps us to conduct an accurate study on the effect of different parameters on a bouncing ball. This finite element model includes a surface-based fluid cavity to model the mechanical response between the ball carcass and the internal air of the ball. An experimental set-up was devised to study the bounce of the ball in game-relevant impact conditions. Ball speed, angle, and spin were measured before and after the bounce, as well as ball deformation and the forces during the impact. The finite element model has been validated with three different sets of data, and the results demonstrate that the finite element model reported here is a valuable tool for the study of ball bounce. After validation of the model, the effect of the friction coefficient on soccer ball bounce was studied numerically. Simulation results show that increasing the friction coefficient may result in reversal of the horizontal impact force.  相似文献   

18.
Swing trajectory and ground reaction forces (GRF) of 30 collegiate baseball batters hitting a pitched ball were compared between a standard bat, a bat with extra weight about its barrel, and a bat with extra weight in its handle. It was hypothesised that when compared to a standard bat, only a handle-weighted bat would produce equivalent bat kinematics. It was also hypothesised that hitters would not produce equivalent GRFs for each weighted bat, but would maintain equivalent timing when compared to a standard bat. Data were collected utilising a 500 Hz motion capture system and 1,000 Hz force plate system. Data between bats were considered equivalent when the 95% confidence interval of the difference was contained entirely within ±5% of the standard bat mean value. The handle-weighted bat had equivalent kinematics, whereas the barrel-weighted bat did not. Both weighted bats had equivalent peak GRF variables. Neither weighted bat maintained equivalence in the timing of bat kinematics and some peak GRFs. The ability to maintain swing kinematics with a handle-weighted bat may have implications for swing training and warm-up. However, altered timings of kinematics and kinetics require further research to understand the implications on returning to a conventionally weighted bat.  相似文献   

19.
棒球挥击速度的研究   总被引：1，自引：0，他引：1  
应用高速动态分析仪对部分运动员挥击速度现状的解析参数进行了研究．得出从启动──中球的挥击时间：斜碰撞时是在棒速下降时进行的．现要求棒的挥击时间在１００ｍｓ以内，投手球飞行至本垒前３．４ｍ左右时棒开始启挥．  相似文献   

20.
This study considered the effect of temperature and relative humidity on the performance of softballs, baseballs and bats. The balls were conditioned in constant humidity and temperature environments and then impacted against a rigidly supported load cell from which the ball coefficient of restitution and stiffness were obtained. The balls reached steady state temperature on the order of a few minutes, while steady state humidity required upwards of 2 weeks. Ball stiffness and coefficient of restitution tended to decrease with increasing humidity. Increasing temperature generally caused ball stiffness to decrease and the coefficient of restitution to increase. Balls made from synthetic materials tended to resist the effects of moisture, but showed an increased sensitivity to temperature. The effect of temperature and humidity on bat performance (sign and magnitude) depended on the design of the ball and bat. The largest effect occurred in professional baseball, where for a long fly ball, decreasing the temperature by 33 °C and lowering the relative humidity from 90 to 10 % resulted in a 5 m decrease and a 15 m increase in hit distance, respectively.  相似文献   

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