## 1 Introduction
In order to avoid this undesirable interference effect, supports are often attached downstream of the object, which minimizes their effect. To study the effect of ball orientation, however, the ball is supported on its spin axis, close to the flow separation. It is not clear how these attachments affect the location of the flow separation and drag measurements. Figure 1: Wind tunnel results show the effects of seam orientation on the drag coefficient from [10]. Baseballs have a characteristic white leather cover formed from two panels that are sewn together by hand with a single continuous seam. While they are similar in appearance, the construction and quality of baseballs vary widely between models. This work considers the Major League Baseball (MLB), given the high interest in ball response at this level of play and its high repeatability and quality. The effects of the drag are considered for \(Re\) = 170,000 (36 m/s), which is representative of play. Wind tunnel measurements of non-spinning MLB baseballs have found its drag to be as low as \(C_{d}\) = 0.3 [11] and as high as \(C_{d}\) = 0.6 [12]. While baseball drag in play is likely closer to \(C_{d}\) = 0.35 [13; 14], the range in \(C_{d}\) from wind tunnel measurements suggests that it is challenging, even for aerodynamic specialists to measure. The first free-flight baseball drag measurements occurred during the 1996 Olympics [15]. Balls were tracked with two 120 Hz cameras at a resolution of 640 \(\times\) 480 pixels. While the drag crisis from this work was likely overestimated due to low camera resolution (\(C_{d}\) = 0.15), it was an important advancement in aerodynamic measurement. In 2006, video-based ball tracking systems were installed in every Major League Baseball Park (PITCHf/x, Sportvision). The three components of each pitch trajectory are fit to second-order (constant acceleration) polynomials using a least-squares fit. The systems were primarily intended to track pitch speed, pitch movement and the strike zone location, but drag could also be extracted from the publicly available fit parameters. Drag measurements were susceptible to noise and environmental effects inherent with ballparks. These shortcomings were largely overcome by averaging the large amount of data collected over multiple seasons. One study reported \(C_{d}\) = 0.346 [16]. Another study measured the launch conditions and landing locations from balls projected 120 m from a pitching machine in an enclosed park and found \(C_{d}\) = 0.36 [17]. The balls were projected at 43 m/s, slowing to 27 m/s at their apex, with an average speed of 36 m/s over their trajectory. The general agreement in \(C_{d}\) between the wind tunnel (no spin) and free flight (with spin) measurements is noteworthy. The drag coefficient is known to increase with ball spin, although the dependence is weak [13; 18]. The agreement with the balls projected in the stadium also show that average drag properties have utility in describing ball trajectories. The following proposes a laboratory system to measure the drag of baseballs in free flight. The system avoids the large infrastructure and the potential effects of the sting and wall interference associated with wind tunnels. Baseball drag is measured as a function of orientation and compared to the drag of spinning balls.