Understanding the mechanical characteristics of badminton shuttlecocks
Creators: name: Woo, To Ming Terence
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 401201
subject: Aerodynamics (excl. hypersonic aerodynamics)
classificationCode: 401699
subject: Materials engineering not elsewhere classified
classificationCode: 401799
subject: Mechanical engineering not elsewhere classified

description: This research project was designed to provide insights into the relationship between a shuttlecock’s aerodynamic and mechanical properties. Synthetic and feather shuttlecocks were examined to understand the limitations of the current artificial shuttlecock designs which is vital for the optimisation of current products and the development of future synthetic shuttlecocks. In addition, this project also discussed new methodologies for testing biological materials.
The shuttlecock, the sport projectile used in the game of badminton, is manufactured by fixating feathers of either ducks or geese into a hemi-ellipsoid cork base. Unlike many other sport balls and projectiles, the badminton shuttlecock is defined by its unique hollow cone appearance. The hollow structure means that the projectile exhibits distinctive flight characteristics which have attracted much attention within the study of aerodynamics.
 
However, since its inception, the shuttlecock design has remained unchanged, in contrast to its racquet counterpart which has benefited from new manufacturing processes and materials. This neglect has resulted in several consequences: 1) excessive replacement of shuttles over the course of a game; 2) substantial and constant disruption to the flow of the game because of the inherent lack of durability of shuttles; and 3) a high financial cost of replacing the shuttlecocks, thereby reducing the appeal of the sport as a recreational activity. The origin of this challenge is believed to stem from a lack of understanding of the feather structure of the badminton shuttlecock.
 
Initially, a comprehensive literature review encompassing the development of badminton research in the past 50 years was conducted. After this, a more detailed study of the current knowledge of badminton shuttlecock aerodynamics was performed. A knowledge gap became apparent from this second study: there is a limited understanding of the structural mechanics of a shuttle and how this may affect the overall aerodynamics. The relationship between the structural mechanics of the shuttle and its flight characteristics therefore represented an original contribution to the field.

Three experimental studies were conducted. Firstly, a notational analysis study comprising of the observation of 36 official matches was performed. The analysis quantified the frequency of shuttlecock changes and five game characteristics: format of play, scoring system, badminton shots, duration of shuttlecock use and racquet contacts (exchanges) were examined to determine the most significant factors which increased the likelihood of shuttle replacement. Statistics used to quantify the effects of the different factors, showed that singles matches resulted in up to 50% more change requests than doubles matches and that men’s singles matches were found to have a disproportionately higher number of shuttlecock changes.
 
Destructive tests were used to provide a physical and material characterisation of all shuttlecock types. Regarding the physical characterisation analysis, the conventional synthetic shuttlecocks were much shorter than the feather shuttles, but still within the guidelines for use. The material analysis of the shuttles was performed using Fourier Transform Infrared Spectroscopy (FTIR).
 
With respect to these results, the artificial shuttles were made from poly(butyl methacrylate) (PBMA), polyethylene terephthalate glycol (PETG) and polyurethane 85A (PU85A), all of which are known for having superior impact strength and flexibility, or weatherproofing capabilities. Scan results of the feather samples identified blends of nylon. In general, scan results of the synthetic shuttlecock were found to be more consistent than that of its feather counterpart.

A wind tunnel investigation was then conducted. This involved 9 shuttlecock products (AS50, M350, M2000, HQ R, HQ SP, HQ G, RSL B, RSL G and Bird2) consisting of natural feather (goose and duck) and synthetic shuttlecock samples. 12 different speed conditions were used to identify any flight differences across the different shuttle designs. When benchmarked against the AS50 shuttlecock, discrepancies in aerodynamic drag were observed at 45 km/h in both duck feather shuttlecocks (HQ G and RSL B). HQ G saw a more rapid increase than the AS50, but RSL B displayed a stagnated increase and eventually fell below the benchmark level. At the moderate to high-speed range (60 – 120 km/h), one synthetic shuttlecock sample (M350) reported a drop in FD with increased speed, while only minor fluctuations were observed in the other synthetic samples (M2000 and Bird2). Used shuttlecocks also reported to maintain a consistent level of aerodynamic drag compared to synthetic shuttlecocks.

Three mechanical testing procedures were performed: a compression test and a hysteresis test on the shuttlecock feathers; a skirt compression test was also conducted. For the feather compression tests, the highest loading stress and modulus for the goose feather products was s: 7.89 MPa; E: 1.03 GPa (RSL G) and the highest mean stress and modulus for the duck feather products was s: 13.09 MPa; E: 1.91 GPa (HQ G). Regarding hysteresis, HQ G reported the largest range in maximum stress, while RSL B was found to have the highest change in modulus (-47.75%) and mechanical energy (-23.97%).

A novel approach of conducting a compression test along the horizontal axis of the shuttlecocks was performed to compare the skirt stiffnesses of different shuttlecock products. The selected feather shuttlecock products were also tested against used feather shuttlecocks. The highest stress and modulus were reported in AS50 (s: 0.0544 MPa; E: 0.2063 MPa) a feather shuttlecock while an artificial product, M350, (s: 0.0031 MPa; E: 0.0128 MPa) had the lowest values. Also notable was that the skirt stiffness of used shuttlecocks (s: 0.0341 MPa; E: 0.1365 MPa), produced considerably higher stress and modulus compared to several of the feather shuttlecocks and all synthetic shuttlecocks. It was found that the synthetic skirt was up to 8.8-fold less stiff than RSL B, the least stiff feather skirt.