Abstract des Autors

In seam bowling, the first two fingers are supposed to impart equal amounts of back-spin to the ball. As the rotating
arm of the bowler and the backspin of the ball have different senses (clockwise vs. counterclockwise), the spin axis
moves rapidly from one hemisphere to the other, thereby crossing the seam, when finger torque is imparted onto the
ball. It is shown in this study analytically, that the rapidly precessing spin axis approaches the torque vector, but
reaches the torque vector only at large times. From the experimental data, the spin and torque vectors are
approximately 10-15º apart when releasing the ball in seam bowling. If the spin axis is not exactly at the pole of the
ball, i.e. perpendicular to the seam, then the seam wobbles by twice the angle between spin and torque vectors. It is
therefore advisable to have the finger centre of pressure slightly off seam by 10-15º.