Roy Jones

Human perceptions of sports equipment under playing conditions

Assessment of the ‘performance’ of sports equipment is generally derived from physical and technical parameters, such as power, speed, distance and accuracy. However, from a psychological perspective, players need to feel comfortable with their equipment and confident in its properties. These factors can only be measured through the subjective assessment of individual perceptions. Focusing on a group of elite golfers, this study presents a formalized approach for eliciting and structuring players’ descriptions of their perception of sports equipment. Qualitative methods of inquiry were used to generate perceptions from a group of professional golfers ( n = 15) during play testing. The equipment characteristics of significance to the golfers emerged from an inductive analysis of their responses. However, although this method of representation of the results helped to identify the key components or dimensions of a players subjective perception, it was unable to determine potential relationships between the dimensions. With this in mind, a new technique, called structured relationship modelling’, was developed. Ten general dimensions emerged from the analysis, of which three are presented here together with a section of the relationship model. The results demonstrate the effectiveness of qualitative techniques for eliciting human perceptions and of structured relationship models for representation of the associations found.

Experimental studies of the aerodynamics of spinning and stationary footballs

The accurate discrimination of the aerodynamic parameters affecting the flight of sports balls is essential in the product development process. Aerodynamic studies reported to date have been limited, primarily because of the inherent difficulty of making accurate measurements on a moving or spinning ball. Manufacturers therefore generally rely on field trials to determine ball performance, but the approach is time-consuming and subject to considerable variability. The current paper describes the development of a method for mounting stationary and spinning footballs in a wind tunnel to enable accurate force data to be obtained. The technique is applied to a number of footballs with differing constructions and the results reported. Significant differences in performance are noted for both stationary and spinning balls and the importance of the ball orientation to the flow is highlighted. To put the aerodynamic data into context the results are applied in a flight model to predict the potential differences in the behaviour of each ball in the air. The aerodynamic differences are shown to have a considerable effect on the flight path and the effect of orientation is shown to be particularly significant when a ball is rotating slowly. Though the techniques reported here are applied to a football they are equally applicable to other ball types.

Human perceptions of artificial surfaces for field hockey

Measuring the performance of a sports surface is typically derived from a series of field and laboratory tests that assess the playing properties under simulated game conditions. However, from a player’s perspective their own comfort and confidence in the surface and its playing characteristics are equally if not more important. To date no comparative study to measure playing preference tests has been made. The aim of this research was to develop a suitable method for eliciting player perceptions of field hockey pitches and determine the key themes that players consider when assessing field hockey pitches. To elicit meaningful unbiased human perceptions of a playing surface, an individual subjective analysis was carried out, using interviews and inductive analysis of the recorded player statements. A qualitative analysis of elite hockey players (n = 22) was performed to obtain their perceptions immediately after a competitive match. The significant surface characteristics that emerged as part of an inductive analysis of their responses were grouped together and formed five general themes or dimensions: player performance, playing environment, pitch properties, ball interaction and player interaction. Each dimension was formed from a hierarchy of sub-themes. During the analysis, relationships between the dimensions were identified and a structured relationship model was produced to highlight each relationship. Players’ responses suggested that they perceived differences between pitches and that the majority of players considered a ‘hard’ pitch with a ‘low’ ball bounce facilitating a ‘fast’ game speed was desirable. However, further research is required to understand the relative importance of each theme and to develop appropriate measurement strategies to quantify the relevant engineering properties of pitch materials.

Experimental analysis of impacts with large elastic deformation: I. Linear motion

A measurement system is presented which uses a small number of sensors to capture relevant information by a limited number of measurements during a high-speed impact between two lightweight bodies. Two laser Doppler vibrometers and a piezoelectric accelerometer are arranged to capture data from which the variation of deformations, velocities and forces over time during an impact can be determined. The golf club - ball impact is chosen as an example. Large elastic deformations are measured on the golf ball during the impact and these can be related to the variation of the impact force over time. This information leads to greater understanding of the relationship between two impacting bodies and can be used in the validation of analysis by techniques such as finite element modelling.

Feature-based systems for the design and manufacture of sculptured products

Many products having free form of sculptured surfaces are designed by traditional methods by crafting prototypes. This requires skill. Analysis of these products often reveals that they have an established general form and are designed around a number of dominant features. A feature-based design system is proposed based on extended surfaces and blends that provides designers with considerable flexibility for feature replacement and manipulation. The implications of this approach on the rapid production of prototypes for both design appreciation and manufacturability is discussed. A range of golf clubs has been used as the example around which the methodology has been developed.

Driver swingweighting : a worthwhile process?

Abstract The concept that golf clubs should have a uniform weight distribution means that manufacturers invest significant time and money tailoring the swingweight of their clubs. If golfers are unable to perceive significant changes in swingweight, however, and the effect of swingweight on club performance is small, the current manufacturing tolerances on swingweight can be widened, allowing time and cost savings in the assembly process. Testing was conducted using 30 skilled golfers each performing ten tee-shots with four differently weighted drivers. Clubhead mass was varied using screwed inserts of different known masses and the effects on impact location and clubhead speed were both measured. Changes to golf club weight distribution, measured using the swingweight concept, were found to have little effect on player performance and, in general, golfers were unable to perceive small changes in club swingweight. Manufacturing tolerances for component masses appear to offer sufficient control over golf club weight distribution, suggesting that mass balancing procedures may be relaxed during club assembly to provide production time and cost savings.

Winning new product business in the contract electronics industry

The electronics contract manufacturing market is growing and becoming increasingly competitive with original equipment manufacturers (OEM) expanding their use of contract manufacturers (CMs) to balance workload, lower operation costs and avoid manufacturing capital expenditures. Modern CMs are now expected to be involved in every aspect of an OEM’s product from concept design to customer delivery. This places increased pressures on the CM in terms of service to its customer and it is critical that all aspects of an OEM’s service requirements are determined in order to win business. Provides an overview of a process which may be utilised to capture and manage a customer’s main requirements and expectations from the early phase of contract negotiations to project implementation.

Hollow golf club head modal characteristics: Determination and impact applications

The design of modern hollow golf club heads is a labor-intensive process involving extensive performance festing both by robotic and real golfers. This paper describes how, by correlating club head mechanical behavior with functional performance, it will become possible to use validated computational models to predict this performance as well as related contributions to the ill-defined concept of “feel”. Successful use of experimental modal analysis to validate a hollow golf club head finite element model is reported. Modal tests employing noncontacting, laser-based transducers facilitated identification of the natural frequencies and corresponding modeshapes for the three main surfaces of the club head. The experimental data suggest predominantly different modal characteristics for each surface, and this compares favorably with equivalent data obtained from the finite element model. The modal data are also used to identify surfaces responsible for particular frequency components present in the club head impact sound spectrum. The potential for detailed impact performance prediction using the finite element model is further demonstrated by comparison of computed and experimental club head acceleration measurements recorded during simulated and actual club-ball impacts.

Ball Launch Characteristics for Elite Rugby Union Players

The role played by a team’s kicker in determining the outcome of a rugby union match is becoming increasingly important. However, unlike in other sports, there is no existing data regarding the kicking and passing abilities of elite rugby players. The objective of this study was to determine the launch characteristics of a place kick, drop kick, spiral kick (kick to touch) and spin pass. Testing was carried out at senior English League rugby union clubs, and data from 14 elite kickers were evaluated including current international players. The subjects were asked to perform the different kicks on a specially marked rugby ball at a distance of 60 m from the posts. Each skill was performed until they had achieved five ‘good’ strikes or passes. A high speed camera (NAC 500), operating at 500 frames per second was used to record the ball velocity, spin and launch angle. The data presented shows that players are able to achieve velocities of 38.1 m/s whilst imparting 405 rpm to a rugby ball (drop kick). The maximum spin rates seen in the other types of kick are considerably lower. The study of the spin pass has shown that whilst players impart considerably lower levels of velocity to the ball (18.3 m/s), they are capable of achieving spin rates similar to those seen for a place and spiral kick.

A Structured Approach to the Design of Shoe Lasts

Abstract The foundation for sculptured feature-based shoe last design, using extended form (EF) feature methods, is presented. The EF approach is particularly suited to sculptured surface products that exhibit parametric variation throughout a set or family, such as shoe lasts. Some underlying principles and issues relevent to shoe lasts and common to sculptured products that can be usefully modelled by the EF feature approach are also discussed. An initial feature anatomy for a common shoe style is proposed to support the need for localized shape control for current and future design requirements. The following conclusions are reached: it is possible to decompose a shoe last into a feature anatomy for EF feature-based design; there are issues common to sculptured products, including shoe lasts, that are specifically addressed and dealt with effectively within the EF method; an EF feature-based approach shows significant potential to benefit last design efficiency, enhance size grading, and improve manufa...