Top view of the bat and ball testing facility at the Sport Science Laboratory at Washington State University with a bat as the impact surface. For some of the studies the bat was replaced by a fixed rigid surface, either flat or cylindrical.
Measured values of the COR versus the incident speed for three 1970s balls (closed symbols) and three 2004 balls (open symbols), with different plotting symbols corresponding to different balls. The vertical line at 58 mph is the range of COR specified by Major League Baseball. The at 104 mph is the measurement of Briggs13 on 1938 baseballs.
Ball weight as a function of relative humidity, showing that the weight increases by 3.8%, as the relative humidity is increased from 0.33 to 0.75.
Cylindrical COR as a function of relative humidity and temperature. These data show that the ball COR decreases by 4.5% when the relative humidity is increased from 0.3 to 0.5 and by 3.3% when the temperature is decreased from 70 to .
Properties of the Rawlings 34 in bats used in the studies and the results of the measurements. The hollow and corked bats are modifications of the “unmodified” bat. The control bat is a similar but different bat. The weight is in ounces, the center-of-mass (CM) is measured in inches from the knob end of the bat, and the moment of inertia is with respect to a point 6 in from the knob and in units of . The collision efficiency , the ratio , and the ball-bat COR are measured at an impact location 29 in from the knob. Estimated uncertainties in the least significant digit are given in parentheses.
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