Understanding the effect of finger–ball friction on the handling performance of rugby balls

Abstract

Handling errors are often seen in professional rugby games and even more so in amateur rugby. This paper analyses the problem of ball mishandling using highspeed video footage of passes and a bespoke finger friction rig. The high-speed video analysis showed that when the ball is caught, often there is a fluctuating movement of the fingers over the surface of the ball. It also showed that the fingers move over the surface of the ball when the ball is thrown, confirming that the dynamic friction is a good measure of how easily a ball can be handled. Rugby ball surface samples were used, on a finger friction rig, to assess the coefficient of friction between the finger and the balls. The currently manufactured balls displaying the highest coefficients of friction in clean, dry conditions were the design with square, 'sharp' pimples and also the design with a mixture of small and large pimples. The most consistent ball across wet and dry conditions was the ball with round, large, densely populated pimples. It was also shown that when water is added to the surface of the ball or finger, there was little variation in performance between the ball varieties.

Understanding the Friction Mechanisms Between the Human Finger and Flat Contacting Surfaces in Moist Conditions

“…A finger friction rig, shown in Figure 1, was used to take the friction measurements; a full description of the rig can be found in [18]. The rig uses two load cells to measure both the friction and normal forces.…”

Tribology of Skin: Review and Analysis of Experimental Results for the Friction Coefficient of Human Skin

“…Recent tribological studies on materials contacting the skin comprise medical and sports applications [22,23], textiles [24,25] as well as appropriate surfaces for consumer products [20,26,27] and automotive applications [28,29]. The friction and surface properties of materials and objects are known to be essential for their tactile properties.…”

Friction of the Human Finger Pad: Influence of Moisture, Occlusion and Velocity

“…For example, Sivamani and Maibach [2] tabulated the published values for untreated 'normal' skin that span the range from 0.12 to 3.25. Although previous work has shown that the coefficient of friction depends on a considerable number of factors, such as the body site, the applied normal load, the sliding velocity and the characteristics of the counterbody, the amount of moisture present has a major influence [1][2][3][4][5][6][7][8][9][10]. For example, the coefficient of friction for dry skin typically is reported as having a much smaller value than that in the wet or moist states when sliding against smooth counterbodies [9].…”