Analysis of Knuckleball Trajectories
Wind Tunnel and Related Research
Other Studies Using PITCHf/x Tracking Data
Knuckleballs in the Media
The R. A. Dickey Nasty Pitch Gallery
Physics of Knuckleballs
Baptiste Darbois Texier, Caroline Cohen, David Quéré and Christophe Clanet
New Journal of Physics 18, July 2016
Zigzag paths in sports ball trajectories are exceptional events. They have been reported in baseball, volleyball and soccer. Such trajectories are associated with intermittent breaking of the lateral symmetry in the surrounding flow. The different scenarios proposed in the literature (such as the effect of seams in baseball) are first discussed and compared to existing data. Then experiments are performed on zigzag trajectories and a new explanation is proposed based on unsteady lift forces. In a second step, ind tunnel measurements of these unsteady lift forces are exploited to solve the equations of motion for various sports and deduce the characteristics of the zigzags, pointing out the role of the drag crisis. Finally, the conditions for the observation of such trajectories in sports are discussed.
- Rod Cross's Knuckleball Page. Rod Cross is one of the world's premier sports physicists. Click on the link to see his discussion of the physics of knuckleballs.
- The Knuckleball Mystique: Using PITCHf/x to Distinguish Perception from Reality, an article I wrote that was published January 31, 2012 in Baseball Prospectus. The research involved an analysis of raw tracking data from the PITCHf/x system for four games from the 2011 season, two each by Tim Wakefield and R. A. Dickey. The essential result reported in the article is that knuckleball trajectories are as smooth as those of ordinary pitches, at least within the measurement uncertainty of a few tenths of an inch, despite the fact that the movement on the pitch is erratic and unpredictable.
- Using PITCHf/x Technology to Uncover the Mysteries of the Knuckleball, a powerpoint file from a talk I gave at the Saberseminar at Boston University, August 2012.
- Analysis of Knuckleball Trajectories, an article published in the proceedings of the 9th Engineering of Sport Conference, July 9-13, 2012, in Lowell MA. This article is a more technical version of the one published in Baseball Prospectus. The slides from the accompanying presentation can be viewed here.
- Anatomy of a Really Nasty Pitch, an analysis of a seemingly bizzare R. A. Dickey knuckleball that he threw in a game in June 2012. The analysis synthesizes high-speed video, tracking data, and wind tunnel measurements to come up with a plausible description of the pitch.
- Aerodynamics of a Kunckleball, a seminal article by Prof. Robert Watts and his student Eric Sawyer of Tulane University, published in the November 1975 issue of American Journal of Physics. The article investigates the dependence of the aerodynamic forces on a baseball as a function of the orientation of the ball in the four-seam configuration.
- THE KNUCKLEBALL In this brief article, the author parametrizes the results of the Watts/Sawyer experiment, then uses those results to calculate simulated knuckleball trajectories.
- Aerodynamics of the Knuckleball Pitch: Experimental Measurements on Slowly Rotating Baseballs, an article by Prof. John Borg and Michael Morrissey from Marquette University and published in American Journal of Physics, October 2014. This research is a more modern version of the Watts work, extended to include the all-important two-seam configuration. In addition to the wind tunnel studies, the authors actually interviewed Mets knuckleball pitcher R. A. Dickey for the article. The research was the Master's thesis of Mike Morrissey.
- Gameday Meets the Knuckleball, an article by Dan Fox published in Baseball Prospectus in June 2007. The article analyzes the movement of Tim Wakefield's pitches. It is the first article of which I am aware to use PITCHf/x data to study the knuckleball and the first to examine, both qualitatively and quantitaviely, the movement of the pitch. Fox shows that, unlike normal pitches, the movement on the knuckleball is erratic and unpredictable, both in magnitude and direction.
- Butterflies Are Not Bullets, an article by John Walsh published in The Hardball Times in November 2007. Walsh follows up and extends Fox's analysis to show a direct correlation between hitting statistics and movement. In short, if there is not much movement, the pitch gets clobbered.
- These are links to a series of articles written by Josh Smolow in 2010.
- Mastering the Knuckleball Part I: A Look at the Long-Established Knuckleballer, Tim Wakefield
- Mastering the Knuckleball Part 2: How has R.A. Dickey Developed and Why is his Knuckleball So Much Better than Tim Wakefield's?
- Mastering the Knuckleball Part 3: The Future of the Knuckleball in the Major Leagues.
- Knuckling Under at Two Speeds: R. A. Dickey's Two Knuckleballs.
- R. A. Dickey on "Letting the Butterflies Loose", an article by Eno Sarris published July 3, 2012 in FanGraphs.
R. A. Dickey on 60 Minutes Lesley Stahl interviews R. A. Dickey on a 60 Minutes episode, which aired on April 14, 2013.
How a Baseball Star's Tricky Pitch Strikes Out Hitters--and Baffles Physicists This is an excellent article that appeared on November 12, 2012 in the on-line edition of Discover Magazine, written by Associate Editor Andrew Grant. The baseball star is R. A. Dickey. Grant gets all the facts right and does a good job posing the outstanding problems that still baffle people like me.
Knuckleball! A documentary film by Ricki Stern and Annie Sundberg. Quoting from their publicity blurb: "This classic sports story recounts the 2011 journey of the last professional knuckleball pitchers: Tim Wakefield, a 17-year Red Sox veteran, and Mets up-and-comer R.A. Dickey. Together with just four other living knuckleballers, they shine a light on their remarkable brotherhood and the shared pursuit of honor and craftsmanship." It debuted in April 2012 at the NYC Tribeca Film Festival, it had a special viewing at SABR42 convention in July, and it is scheduled for general release later in 2012.
The Knuckleball: The science behind why it's so damn hard to hit,
a video shoot at Parkland College. The clip features left-handed knuckleball pitcher and Grinnell College physics undergraduate student Andrew Kelley, who worked with me in summer 2012 on knuckleball research. Published June 23, 2012 by ReutersTV.
Nobody Hits It This story appeared in Sports Illustrated in 1959 and is about HoF knuckleballer Hoyt Wilhelm. Starting on page 4 is a section called "Scientific Expose of the Knuckler."
- A New Take on Why a Knuckleball is so Hard to Hit. A very nice graphic that accompanied an article about R. A. Dickey in the Washington Post, June 2012.