Precession could affect curveball quality by continuously shifting the angle of the spin axis during the ball’s trajectory, thereby continuously redirecting instantaneous deflection and reducing total effective deflection. Obviously, the ball would not have different spin and deflection rates at the two poles. In addition, the spin axis has two poles-a dot pattern might appear at one pole, while the opposite pole displays a circle or bands. 1 and 2 occur on balls spinning at the same rate. Note that the dot and circular patterns shown in Figs. In all cases, precession is caused by a secondary torque perturbing a spinning body.Īlthough the rotation of a manifest point or the precession of a pole might cause the appearance of the nickel-sized circle, this pattern does not necessarily indicate a reduced magnitude of spin or deflection. Precession is also the basis of the behavior of a toy top, a gyro- scope, and a boomerang. when he described the effects of the wobble of the earth’s spin axis. The term was first used by Hipparchus of Nicea in 130 B.C. Precession is a common feature of spinning objects. The precession can rotate in the opposite direction or same direction as the spin. If the dot at the end of the spin axis rotates, it circumscribes a small circle. This is a “wobble” or gyration of the spin axis about a secondary axis. Note that the circular pattern around a mid-isthmian pole would be reinforced by having two manifest points rotating about the axis.Īnother possible cause of a circle on a nickel pitch would be a rotation of the dot, in a phenomenon called precession. In contrast to the circles caused by a pole migrating into a plain, this circle would be quite distinct and invariable in size. The seam spinning rapidly around the mid-isthmian point would produce a reddish circle with an internal area about the size of a nickel. The distance across the seamless part of the isthmus is approximately 22 mm, nearly equal to the diameter of a nickel (~21 mm). If the pole is located near the center of a plain, neither dot nor circle can be discerned.Ī possible cause of a distinct nickel-sized circle on a pitch would be the location of the spin-axis pole near or at the midpoint of the narrow gap or isthmus between two of the plains (as shown in Fig. Shifting the pole into the large plain of one of the Cassini ovals causes the circle to widen to an encompassing band. With a pole displacement of a few millimeters, a small, fuzzy, reddish circle can be discerned due to the manifest point rotating around the pole. We define the manifest point to be the point on the seam that is nearest the pole (Fig. The farther the pole is shifted from the seam, the less distinct the dot becomes. The dot appears on the dime curve or slider if one of the ball’s spin-axis poles is located on a seam. Plausible Explanations of the Dot and Circle Features Finally, we speculate as to how these inadvisable grip and release features might have become associated with a circular or banded spin pattern. Then for each of those two pitches, we describe how the grip and release of the ball could produce poor deflection. First, we present models that describe how the various orientations of spin axis and seam might result in the visible spin patterns of curveballs and sliders.
#Nickel dim3 series#
In this paper we will attempt to answer that question in a series of three steps. Generally, coaches and players assume the dot indicates a fast-spinning pitch (sometimes called a “tight” spin) with a consequential large deflection the circle or the pattern of indistinct bands is believed to signal a slower-spinning pitch with inferior deflection. When visible, these features can be seen on the face of the slider, from the side of the overhand curveball, or from above the sidearm curve. 2) that is observable on some sliders and curveballs. The monetary designations allude to the dime-sized red dot (Fig. Pitching coaches often refer to the appearance of sliders and curves in terms of two U.S.
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