High-speed video analysis of arrow behaviour during the power stroke of a recurve archery bow

Abstract

The manner in which an archer holds and releases the string of a recurve bow causes the arrow to flex during the bow’s power stroke and on its way from the bow to the target. While an experienced observer can subjectively evaluate an arrow’s pitch and yaw visually after it has left the bow, the arrow’s behaviour during the bow’s power stroke happens too quickly for visual observation. High-speed video is consequently a much more effective tool. Similarly, high-speed video is an effective tool for studying an archer’s technique during the bow’s power stroke. Mathematical models of the arrow’s behaviour in the horizontal plane during the bow’s power stroke have, to date, relied upon comparison of the arrow’s flexural shape with photographs. However, an implicit assumption of that process is that the archer’s technique is perfect. This paper provides an analysis of event times and the magnitudes of several key components of the arrow flex during the bow’s power stroke for sixteen world-class archers. Aside from being a powerful analysis tool in its own right, that data can also be used to evaluate mathematical models of arrow behaviour. It is concluded that archer technique variations could be a significant source of error where a single archer is used as a comparison for the mathematics, even if that single archer is amongst the world’s best.

Arrow behaviour in the lateral plane during and immediately following the power stroke of a recurve archery bow

“…The lateral movement of the string as it moved across the archer’s fingers was measured by Park and Logan., 14 with the average lateral movement for 12 top archers being 4.7 mm. Similarly, the forward movement during that time was measured from high-frame-rate video; it was found to be of the order of 9–10 mm.…”

“…Consequently, the lateral displacement of the bow due to these forces can be expected to be significantly less than the lateral displacements of the arrow, and that was seen to be the case in the high-frame-rate videos analysed by Park and Logan. 14 In those videos, the lateral movement prior to the arrow leaving the string was barely detectable. Rotation of the bow about a vertical axis while the arrow was on the string can be expected to be very small due to the substantial inertia about that axis added by the bow’s stabiliser system.…”

“…Park and Logan 14 used very high-frame-rate video photography to analyse the archer’s technique and arrow behaviour both during and immediately following the power stroke of a recurve bow. Sixteen world-class archers were studied, and average event times and magnitudes were obtained for the various aspects of arrow behaviour, with the later objective that they could be used for comparison with modelled arrow behaviour.…”

Development of release velocity and spin prediction models for passing machines in American football

“…The chosen measurement method was a high-speed camera with image post processing. This approach is common for measurements of correlation, orientation or displacement, [8][9][10][11][12][13] although applying this method to enhance the performance of a passing machines is new. The image post processing uses videos from the camera to obtain position data of the ball.…”

“…With the assumption that the relative movement between ball and inertia wheels becomes zero before the line of release, the angular speed of the inertia wheels and ball are as shown in equations (7) and (8)…”