6.1 Introduction to Chapter
After identifying a larger variability in the outcome measurements of the kinematic variables of ball roll in Study Three (Chapter Five) in comparison to the variance of the putting stroke. It was hypothesised that some of this variability may be actually occurring as a result of the variability of the impact point occurring due to the minor differences in ball placement as shown in Figures 5.2 to 5.5. Along with previous literature tentatively identifying that ball dimples can affect the initial ball direction (Cross, 2006; Pelz, 2000). With the distinct lack of literature discussing in depth the kinematic variables of ball roll, it was decided this impact variability and dimple effect on kinematic variables needed to be investigated. The reliability of the new analysis technique developed is presented in Study Four: The reliability of an experimental method to analyse the impact point on a golf ball during putting (Section 6.2). Additionally, Study Five: The effect of impact point on golf ball roll during putting using a mechanical putting robot (Section 6.3) is presented in this chapter. The protocol was conducted with the hypothesis that a certain degree of the variability (accountable to the impact point on the golf ball) could not be controlled for. Both Study Four and Five will indicate as to whether the impact point and dimples does affect the kinematics of the ball roll when all other variables are held constant. The Development of Research (Section 6.4) concludes this chapter summarising the findings from both Study Four and Five with a brief discussion of the findings and outlining the future research that was conducted.
6.2 Study Four: The reliability of an experimental method to analyse the impact point on a golf ball during putting
6.2.1 Abstract
Background: To date no previous literature has discussed the role of variability of the impact point on the resulting kinematic variables of the role of the golf ball. Aim: To examine the reliability of an experimental method identifying the location of the impact point on a golf ball during putting. Method: Forty trials were completed using a mechanical putting arm set to reproduce a putt of 3.2 m, with four different putter-ball combinations. The data processing protocol was repeated for four putter-ball combinations to establish day-to-day reliability. After locating the centre of the dimple pattern (centroid) the following variables were tested; distance of the impact point from the centroid location, angle of the impact point from the centroid location, X and Y coordinates, and distance of the impact point from the centroid derived from the X, Y coordinates. Results: Very strong relative and absolute reliability was demonstrated across all variables (Pearson’s r = 0.98 – 1.00; ICC = 0.98 – 1.00). The highest day-to-day variability observed was 7% in the variable angle of the impact point from the centroid location. Conclusion: The experimental method was shown to be reliable at identifying the impact point on the golf ball and therefore can be used in subsequent studies.
6.2.2 Introduction
Four clear phases have been defined that contribute to putting direction variability (Figure 6.1); these are green reading, aim, stroke and ball roll, which can be influenced by green inconsistencies (Karlsen et al., 2008). One variable that has not been analysed within the literature extensively is the impact point on the golf ball.
Literature investigating the effect of impact point on the resulting kinematics of the golf ball during putting is very limited. Cross and Nathan (2007) have researched the gear effect in ball collisions, including the golf ball. Results demonstrated the rate of spin increased when the angle of incidence (degree of deviation away from a perpendicular collision) is increased (Cross & Nathan, 2007), which could potentially be detrimental to putting performance. They concluded that the gear effect occurs as a result of static friction between the ball and object during a collision. A clear limitation of the Cross and Nathan (2007) study is that during the experimental protocol, the ball was collided off a wooden block which is not as appropriate as the use of a putter head. Alessandri (1995), Lorensen and Yamrom (1992), and Penner (2002) have all proposed mathematical models of the motion of a putted golf ball over the surface of the green. However, no studies within the literature have tested the variability of the motion of a putted ball with subjects or a putting robot to date.
Figure 6.1. Main factors affecting golf putting direction (adapted from Karlsen et al., 2008).
More research is required to examine whether the impact point during the putter face – ball interaction influences the success of the subsequent putt. Currently no studies have investigated how variation in the impact point on the golf ball influences the resulting kinematics of the golf ball and, furthermore, how different dimple patterns on the ball can affect the resulting kinematics of the ball. No method for the analysis of the effect of the impact point has been devised or suggested within the literature. Therefore, the aim of this study was to develop a valid and reliable method of assessing the impact point on a golf ball during putting to allow for further research to determine whether the impact point has an effect on the resultant kinematics of the ball during the golf putt.
6.2.3 Methods
Experimental set - up
All testing was completed in the Quintic Golf Laboratory on an artificial putting surface registering 12 on the stimpmeter. The Quintic mechanical putting arm mounted on an 360 kg