The validity of a rigid body model of a cricket ball-bat impact

Abstract

Rigid body impact models have been used in a number of racket and bat sports to better understand how physical properties such as mass, moment of inertia and balance point can affect ball rebound speed. Cricket is sport whereby players can select their preferred bat with a wide range of different physical properties. No previous studies have attempted to validate the use of rigid body impact models in cricket, and player choices are typically made through intuition with little consideration of impact mechanics. This study measured the performance of three different cricket bats in freely suspended impact tests, and compared the results to predictions made by a rigid body model. Ball rebound speed was measured using high speed video on impacts locations across the blade. The physical properties of the different bats were measured and used as the input for the rigid body model predictions. It was found that for impact locations close to the bat's centre of mass, the rigid body model worked well, but some discrepancies were found as the impact location moved away from the centre of mass. These discrepancies were believed to be caused by the large vibrations evident during the impacts (a clear violation of the model's rigid body assumption) and the erroneous method that was employed to measure the bats coefficient of restitution. It was concluded that using a rigid body model to describe the impact of a cricket ball with a cricket bat is valid as a first approximation and that it has significant value in terms of exploring how changing a bat's physical properties may affect its performance.