Squash ball mechanics and implications for play.

The purpose of this research was to examine how temperature and velocity affect coefficient of restitution and how temperature affects the force-deformation properties of balls used in the international game of squash. The balls used were the international yellow dot and a newly developed double yellow dot. Coefficient of restitution increased with temperature and decreased with increases in projection velocity. The effect of temperature was most marked at low projection velocities. Coefficient of restitution was smallest for the double yellow dot ball but differences between balls decreased with increases in both temperature and projection velocity. Static tests showed increasing ball stiffness with increases in both force applied and temperature, and the yellow dot ball showed the greatest stiffness. Static tests indicated that standards published by the Canadian Squash Racquets Association are inappropriate. These results are discussed in the contexts of play and testing and design criteria for the balls.