Ball Launch Conditions Research Articles

Predicting golf ball launch characteristics using iron clubhead presentation variables and the influence of mishits

In golf, it is well understood that the interaction between the clubhead and ball determines the initial ball launch conditions. Specific knowledge regarding these relationships for iron clubs, particularly when clubhead and turf interactions are considered, would be both novel and of benefit to practitioners. Linear regression analysis was used to determine relationships between selected clubhead presentation and shot outcome variables for a sample of 1127 ‘5-iron’ shots hit from natural turf by 96 golfers. As expected, clubhead speed was the most significant predictor of ball speed, with obliquity of impact and eccentricity of the impact location making smaller, yet statistically significant contributions. Marginally ‘fat’ strikes, whereby the leading edge of the clubhead was only slightly beneath the ground at impact, appeared to have a lesser effect than expected in terms of ball speed. Effective loft was found to be the strongest predictor of vertical launch angle, whilst clubhead speed and spin loft had the greatest influence in the model for predicting total spin; inclusion of ‘thin’ strikes (i.e. those struck with the leading edge) appeared to create a non-linear element to these models and consequently overestimated the influence of vertical impact location in both cases. These findings suggest that determination of impact location, particularly for instances whereby ball contact is not wholly on the club face, is critical in research concerning irons. Overall, this study makes an original contribution to the understanding of 5-iron shot outcomes based on clubhead presentation characteristics.

The influence of 5-iron clubhead mass distribution on clubhead presentation and initial ball launch conditions – Part II: Player tests

Iron clubheads can be classified as blades or perimeter-weighted, depending on the distribution of their mass. Despite the widely held views that perimeter-weighting can offer performance benefits for lesser skilled players, a direct comparison with players using these two clubhead types has not been thoroughly investigated. The aims of the study were to determine differences in clubhead presentation and ball launch between a blade 5-iron and a cavity-back 5-iron in a mixed cohort of golfers and examine trends in central tendency and variability in relation to skill for males using the blade club. Nine clubhead presentation variables and six ball launch variables were measured for 96 participants hitting shots from natural turf with each of the clubs. Group means for club effect were analysed statistically using an independent samples approach, whilst a rank-based nonparametric test was used to determine significant trends between handicap categories and ball launch conditions for the male cohort. The cavity-back displayed higher effective loft, lower effective lie and a tendency to have ball strikes closer to the centre. Higher values were also noted for the cavity-back for vertical launch angle and total spin. As expected, higher handicap male golfers showed lesser consistency and displayed slower ball speeds and lower efficiency than the more skilled players. Together these results concur with the findings in Part I in support of the theory of ‘forgiveness’ associated with cavity-back clubs, whilst also highlighting the over-riding importance of skill level on performance.

The influence of 5-iron clubhead mass distribution on clubhead presentation and initial ball launch conditions: Part I: Golf robot tests

It is well accepted that iron clubhead properties affect shot outcomes in golf. However, the mechanisms that contribute to this relationship have not received recent scientific study. The purpose of this study was to determine how the different clubhead mass distributions in a blade 5-iron and a cavity-back 5-iron affect clubhead presentation and ball launch conditions. Nine clubhead presentation variables and four ball launch variables were measured for ten discrete impact locations and five face angles during swings using a golf robot. Group means were analysed statistically using an independent samples approach to identify differences and linear regression was used to indicate relationships between key launch variables. The cavity-back showed higher effective clubhead loft with greater total ball spin than the blade, despite having matched static lofts, whilst also providing more consistent launch outcomes across a range of impact locations. Evidence of the phenomenon known as the ‘gear effect’ was found for the cavity-back, but not the blade, suggesting that the threshold at which the clubhead’s centre of gravity (CG) is deep enough to detect the gear effect lies between the CGs of the two 5-iron types. These novel robot test findings lend support to the perceived performance benefits of perimeter-weighted irons; whether these effects translate to human golfer swings is reported in Part II of this paper.

Assessing rugby place kick performance from initial ball flight kinematics: development, validation and application of a new measure

The appropriate determination of performance outcome is critical when appraising a performer’s technique. Previous studies of rugby place kicking technique have typically assessed performance based on ball velocity, but this is not the sole requirement. Therefore, a mathematical model of rugby place kick ball flight was developed to yield a single measure more representative of true performance. The model, which requires only initial ball flight kinematics, was calibrated and validated using empirical place kick data, and found to predict ball position with a mean error of 4.0% after 22 m of ball flight. The model was then applied to the performances of 33 place kickers. The predicted maximum distance, a single performance measure which accounted for initial ball velocity magnitude and direction, and spin, was determined using the model and was compared against ball velocity magnitude. A moderate association in the rank-order of the kicks between these two measures (ρ = 0.52) revealed that the relative success of the kicks would be assessed differently with each measure. The developed model provides a representative measure of place kick performance that is understandable for coaches, and can be used to predict changes in performance outcome under different ball launch or environmental conditions.

The relationships between driver clubhead presentation characteristics, ball launch conditions and golf shot outcomes

The purpose of this study was to analyse the effects of clubhead presentation on golf ball launch conditions and the subsequent shot outcome. Clubhead presentation was measured using a three-dimensional motion capture system for both male and female golfers across a range of skill levels. A Doppler radar was used to track the golf ball during its flight, yielding speed, launch angles, spin rate and distance. Importantly, the measurements of clubhead and ball quantities were taken independently so that any inter-relationships could be evaluated without recourse to any preconceived models. This article provides values for the median launch conditions and shot outcome, and the associated variability in these quantities for golfers was grouped by handicap category and gender. It was shown that the variability in certain outcome quantities was more linked to golfing ability than others. Linear regression was used to demonstrate that differences in clubhead presentation resulted in changes to ball launch conditions as one might expect from physical analysis. Furthermore, the link between the variability in clubhead presentation and the variability in shot outcome was demonstrated. In particular, the importance of impact location variability in determining launch angle and total distance variability was shown.

Is outcome related to movement variability in golf?

The aim of this study was to develop a method to quantify movement variability in the backswing and downswing phase of the golf swing and statistically assess whether there was any relationship between movement variability and outcome variability. Sixteen highly skilled golfers each performed 10 swings wearing retro-reflective markers which were tracked by a three-dimensional (3D) motion analysis system operating at 400 Hz. Ball launch conditions were captured using a launch monitor. Performance variability was calculated for each body marker based on a scalene ellipsoid volume concept which produced a score representative of the 3D variability over the 10 trials. Outcome variability was quantified as the coefficient of variation of ball velocity for the 10 trials. The statistical analysis revealed no significant correlations between performance variability for each marker trajectory and outcome variability. Performance variability in the backswing or downswing was not related to ball velocity variability. It was postulated that individual players used their own strategies in order to control their performance variability, such that it had no effect on outcome variability.

The influence of golf club shaft stiffness on clubhead kinematics at ball impact

The role of shaft stiffness on the golf swing is not well understood. Studies in which golfers hit balls with clubs of varying shaft flex have reported changes in ball distance. The results of mathematical models suggest that shaft stiffness affects only the orientation of the clubhead at impact, not the speed of the clubhead, but there are no experimental results validating these findings. The purpose of this study was therefore to experimentally examine the influence of shaft stiffness on clubhead kinematics at ball impact. Forty golfers hit 10 balls with each of five drivers varying in shaft stiffness from ‘Ladies’ to ‘Extra-Stiff,’ in a double-blind study design. The motions of three reflective markers attached to the clubhead were captured with a high-speed motion analysis system. At ball impact, shaft stiffness had a statistically significant influence on clubhead speed for 27 subjects, on loft angle for 11 subjects, and on lie angle for all 40 subjects. No effect was observed on face angle, in to out path angle, or attack angle. These results show that shaft stiffness can affect ball launch conditions by altering clubhead speed and/or loft angle.

The Effect of Driver Mass and Shaft Length on Initial Golf Ball Launch Conditions: A Designed Experimental Study

The influence of golf driver mass and shaft length on initial golf ball launch conditions was investigated. A series of carefully selected player tests were used to isolate the coupled influence of club mass and shaft length on initial ball velocity, spin rates, launch angle, and dispersion of impacts across the clubface. The ranges of selected club masses and shaft lengths were typical of those found in currently available drivers. While longer, lighter clubs generally led to higher ball speeds for most test golfers, those combinations of club mass and club length that minimized spin rates resulted in the greatest estimated total shot distance. Not surprisingly, use of longer drivers led to a slightly larger dispersion of impacts over the clubface. Interestingly, individual golfers tended to miss in the same region of the clubface irrespective of the club length, i.e., they compensated for changes in club mass and length when swinging. Employing the methodology outlined here, it may be possible to tailor golf club designs in order to obtain enhanced golf ball launch characteristics for a range of golfers. Such efforts may facilitate golf club design by establishing relationships between mass and configuration parameters that lead to improved driver performance.

Putter features that influence the rolling motion of a golf ball

We present the results of a theoretical and experimental study into the influence of various putter head design features on the rotational dynamics of the ball following putter impact. It is found that ball launch conditions can be tailored by designing the putter head with the appropriate combinations of face loft, center of gravity and moment of inertia. Face treatments, such as inserts and grooves, effect the coefficient of restitution and friction coefficient at the contact point and thus provide additional design parameters to control the launch conditions of a putt. Experiments demonstrate that inserts and grooves can modulate the coefficient of restitution of the impact, but not in a manner that gets the ball rolling earlier for fixed length putts.

Development of a method for monitoring clubhead path and orientation through impact

This study reports the development of a golf clubhead trajectory monitoring system which utilises PONTOS, a 3D motion analysis package from GOM. This paper demonstrates how this system can be used to monitor clubhead path and orientation and position throughout impact with future scope to simultaneously measure ball launch conditions. Six subjects performed 10 swings with a driver and a selection of these shots were analysed in detail. Face angle and dynamic loft were calculated as indicators of clubhead orientation and the effect of off-centre impacts on head rotation were quantified. When considering clubhead velocity, the flexibility of the system allowed velocities at different locations to be monitored. It was found that the velocity of the toe and heel differed by up to 5.7 ms−1 at the moment of impact.

Influence of shaft length on golf driving performance

The aim of this study was to determine how shaft length affects golf driving performance. A range of drivers with lengths between 1.168 m and 1.270 m, representing lengths close to the 1.219 m limit imposed by R&A Rules Limited (2008), were assembled and evaluated. Clubhead and ball launch conditions and drive distance and accuracy were determined for seven category 1 golfers (handicaps 0.21 ± 2.41) who performed shots on a purpose-built practice hole. As shaft length increased from 1.168 m to 1.270 m, initial ball velocity increased (+1.8 m/s, P < 0.01). Ball carry (+4.3 m, P = 0.152) also increased, although not significantly so. Furthermore, as shaft length increased, for all club comparisons there was no decrease in accuracy. Ball launch conditions of spin components and launch angle remained unaffected by shaft length. Launch angle increased (0.8°, F = 1.074, P = 0.362) as driver shaft length increased. Our results show that clubhead and ball velocity together with ball carry tended to increase with no loss of accuracy.

Ball launch conditions for skilled golfers using drivers of different lengths in an indoor testing facility

The displacement of the golf ball struck by a driving club is affected by several player characteristics and equipment parameters and their interrelationships. Some modelling and simulation studies have shown a relationship between shaft length and clubhead speed, supported by a few experimental studies. The aim of the present study was to examine the relationship between driver length and ball launch conditions in an indoor test facility using a ball launch monitor. Nine males considered to be skilled golfers participated in the study. Four driving clubs of total length 117, 119, 124, and 132 cm were assembled from commercially available components and were used to strike golf shots while initial ball velocity, backspin rate, and launch angles were measured. Statistical analysis identified a significant difference in initial launch speed due to club length, a significant difference between participants, but no difference between the trials for a given golfer. A positive trend was noted between backspin and launch angle for all four clubs, and significant inverse associations between initial launch speed and backspin rate and launch angle. However, the combined launch conditions associated with increasing length were not considered optimal, with uncontrolled swingweight and moment of inertia effects considered to be limiting factors.