Physics and Acoustics of Baseball & Softball Bats
Daniel A. Russell, Ph.D.
Graduate Program in Acoustics
The Pennsylvania State University

The contents of this page are ©2003-2011 Daniel A. Russell

Today is This article was first posted on August 2, 2010 and its contents were last modified on August 3, 2010

Disclosure Concerning a Potential Conflict of Interest

During the past several months since the California legislature began considering a bill in the Spring of 2010 to ban metal bats, and especially since the June 11, 2010 airing of an episode of "Outside the Lines" on ESPN, I have been accused of having a conflict of interest. The most often cited concern is that because I have occasionally in the past done some small scale consulting tests for several bat manufacturers, the articles I have written about baseball bats (especially the article "Should Metal Bats be Banned Because they are Inherently Dangerous?") are claimed to be invalid and the conclusions reached in those articles are tainted and should be ignored. The concern of a conflict of interest has so far only been made either by people who wish to ban metal bats - perhaps because they don't agree with (or don't believe) the scientific facts that I quote, or by news reporters who wish to make their news story more "juicy" by stirring up controversy. Nevertheless, the potential for a conflict of interest does exist, and this article is an attempt to mitigate it.

According to the definition from Wikipedia:

A conflict of interest occurs when an individual or organization is involved in multiple interests, one of which could possibly corrupt the motivation for an act in the other. A conflict of interest can only exist if a person or testimony is entrusted with some impartiality; a modicum of trust is necessary to create it. The presence of a conflict of interest is independent from the execution of impropriety. Therefore, a conflict of interest can be discovered and voluntarily defused before any corruption occurs.

Since I am a university professor, there is a certain level of trust inherent in anything I write and post online. As a scientific expert on the subject of baseball physics, I should not officially take sides on the issue of banning metal bats, especially if there is any appearance of association with one of the parties involved. As I will attempt to demonstrate below, I have not taken a side on this issue - even though my articles have been used to support the arguments of people who are on one side or the other. As a researcher who studies the vibrational characteristics of sports equipment, it is practically impossible to avoid having a conflict of interest, because it is impossible to do thorough research without having some form of contact with or support from manufacturers of sports equipment, and/or with the governing bodies that oversee a given sport. In the interest of being clear about my intentions, I am disclosing the information in this disclaimer in an attempt to voluntarily defuse the conflict of interest regarding my research involving baseball and softball bats (including the articles I have written that are being used to argue for or against the banning of metal bats), and the consulting projects I have done for bat manufacturers.

Specific Details About My Past Consulting Activities

Why do I do consulting, and how much have I been paid?

I teach physics at a small undergraduate university which focuses primarily on engineering and the applied sciences. My work load is mostly comprised of teaching classes, but I do have several small scale research projects in my area of expertise in the field of acoustics and vibration. The kind of research projects I pursue are experiments that can involve undergraduate students. My area of research focuses on acoustics and vibration of structures. Largely because of my own personal interests as well as the interests of my students, I have ended up studying the vibrational and acoustic characteristics of sports equipment (softball and baseball bats, ice hockey sticks, field hockey sticks, racquetball rackets, golf clubs) and musical instruments (guitars, brass instruments, pianos, drums). I do not have any graduate students working for me - so I do not have to secure funding to cover graduate student stipends. I have neither the time nor the resources to pursue large externally funded research grants, and government funding agencies tend not be interested in funding small scale research on sports equipment. However, I do have a need to purchase laboratory equipment to be used for student learning in the laboratory courses I teach, as well as equipment for my own use in research - and I am required to do research and publish papers to earn tenure and be promoted. I need computer hardware, software and upgrades for my office and lab (I have to buy my own computers). And, since my department has a very limited travel budget, I occasionally need money to travel to professional conferences to expand my knowledge of my field, and to present papers about my research. The small scale consulting projects I have done have allowed me to meet most of these needs. These small consulting projects allow me focus on my teaching while still supporting a small research lab that can involve students in interesting experimental projects. I will disclose the fact that the amount of money these consulting projects have brought in to me personally totals $14,600 over the last 15 years. That amounts to less than $1000 per year. We are not talking about hundreds of thousands of dollars, nor are we talking about a researcher who is "in the pay" of a group of manufacturers. We're talking about a teaching professor at a small undergraduate school who uses a few small scale consulting projects to purchase computers and software for his office and lab, to travel occasionally to professional conferences, and to purchase lab equipment for his students to use and learn from. In addition to the specific projects I've done for bat manufacturers described below, I've also done a few similar projects for a field hockey stick company, two ice hockey stick companies, a golf club company, a company that makes fly-fishing rods, and two manufacturers of musical instruments (guitars and drums). These non-baseball related projects are included in the total amount of consulting money I mentioned above in boldface. I could probably make a lot more money if I pursued consulting as a major activity - but I'm not in it for the money. I'm interested in the science, and I simply use these opportunities to take care of basic equipment needs in our student laboratory.

So, let me share some of the consulting projects I have done. I want to point out that with one exception, for every one of these projects, I was approached by the manufacturer to do some testing. I did not seek out the manufacturer as a consultant for hire. They sought me out for my expertise in the field of acoustics and vibration. I have some lab equipment and knowledge of certain vibration tests that they don't have access to, and they sought me out to provide some data for them. The only time I asked for money was to cover the high cost of sending bats to a registered lab for performance testing, and I'll provide details of that below.

First, however, I wish to publicly go on record to assert that not a single one of these consulting projects have in any way influenced the content of the articles I have written and posted on my webpage. I wrote these articles on my own initiative to provide clear and scientifically based answers to questions I have been asked. I have never been paid, nor have I received any benefits (monetary or otherwise) for the content or conclusions of any of my articles. Nor has any manufacturer or organization ever influenced me to change or alter the content of any my articles (no one has ever tried to do so, nor would I ever agree to any such compromise).


In 2001-2003 I conducted a series of laboratory tests for CE-Composites, a Canadian manufacturer of composite hockey sticks (Ballistics Hockey) that was starting to get into the softball and baseball market (Combat). They sent me several prototype bats and asked me to perform an experimental modal analysis - a test which determines the vibrational behavior a structure and provides resonance frequencies and bending mode shapes. I was paid just over $4000 during the two years this testing took place. CE-Composites used the data I provided to help correlate actual vibration data with the computer models they were developing for their bats. I also wrote a one-page explanation of "swing weight" which they may have used for some marketing purposes. I used the data from this project to help me understand the physics of the trampoline effect in hollow bats. Further (unfunded) research on the trampoline effect in hollow bats has resulted in a couple of published papers, and more will be published in the near future in scientific research journals. What I have learned I have shared openly with the bat industry, and has proved to be extremely useful to both manufacturers and governing bodies like ASA and NCAA; it has helped them better understand how hollow metal and composite bats behave.

Albin-Damping (Marucci Bats)

In 2005 and 2007 I did some testing for Albin Athletics, (now part of Marucci Bats) to help them refine the design of a vibration absorber in the knob of their bats in an attempt to reduce the painful sting that results from a bat hit away from the sweet spot. I, and tested a number of their prototype vibration absorbers, assessed the amount of damping they provided for a variety of metal bats and made some recommendations as to how they could change their design to enable their absorber to more effectively reduce sting. I haven't heard from them in a while, but it would appear that their absorber pretty effectively reduces the sting for bat hits. My involvement in this project extended over several months both in 2005 and again in 2007. I was paid approximately $4000 total for this consulting work. I have seen some marketing materials on their website where they have chosen to use my name and affiliation to strengthen their marketing claims - even though I have asked them not to do so.

Other Tests for Individual Bat Manufacturers

Between 2003 and 2008 I conducted several small, short tests for a few individual manufacturers (Easton, Nike, DeMarini, Metal Wood, Rawlings, Miken, Mattingly Baseball). A manufacturer would send me a collection of 4-6 slow-pitch softball or adult baseball bats and request damping information or a measurement of the bending frequencies and vibration shapes. Each individual project was on the order of $400-$800, and I have done this about half a dozen times, once for each manufacturer.

Indirect Methods of Assessing Bat Performance

Prior to 2005, several manufacturers and organizations (including ASA softball, and SGMA) were concerned about the problem of illegal altering (doctoring, shaving, rolling) of composite softball bats. I had been experimenting with a couple of ways to indirectly predict bat performance through an analysis of the acoustic and vibration signatures of the bat barrel. In 2005 I wrote a proposal to the SGMA asking for $21,000 to have 30 softball bats tested for performance at the Sport Science Laboratory at Washington State University. It costs $500 to measure the performance of a single softball bat at the WSU lab in accordance with the ASTM 2219 test protocol used by ASA softball. The SGMA came up with $7000 from their high speed softball testing fund, and seven manufacturers chipped in with $1500 each, for a total of $21,000. $15,000 was spent directly on the cost of having 30 slow-pitch softball bats tested at WSU to measure their performance. Another $2000 was used to purchase equipment and build an experimental testing apparatus. The remaining $4000 was used to cover travel expenses to nine meetings (three per year) of the SGMA and ASTM committees so I could provide updates on the project. I am still in the process of analyzing the final data and will be writing a couple of research papers to summarize the results. But, I want to be clear that not a single penny of this funding was taken salary. Not a dime made it into my personal pocket.

Donation of Bats for Research Projects

Most of my research into the trampoline effect in hollow bats has revolved around slow-pitch softball bats. I have received donations of slow-pitch softball bats as well as a few adult and youth baseball bats from several manufacturers (Easton, Louisville Slugger, DeMarini, Worth, Miken, CE-Composites, Anderson Bats Co, Toledo Bats, Toloso, Metal Wood, Reebok, Rawlings). All of these were bats that I specifically requested for my research into the science of the trampoline effect because I wanted to investigate the behavior of a specific type of bat. Most of these bats have cosmetic blemishes and could not be sold because of scratches or graphics defects, but were otherwise in perfect playing condition. All of these bats were donated with absolutely no strings attached. They were donated freely for me to do whatever I wanted with them, with no expectations either way. The only thing manufacturers asked of me is that I blind all of the data when publishing it (meaning that i don't reveal specific bat models or brands when discussing the results in a published paper). I have not asked for (or received) any new bats since 2007.

Bat-Ball 101 Short Course

In 2001, 2002, and 2003, I co-taught (along with two other experts in the field of baseball physics) a 2-day short course called "Bat-Ball 101". This short course was attended by engineers from most of the major and minor bat manufacturers. The first course offering coincided with changes in the bat performance standard adopted by ASA softball. We taught the attendees the physics behind the bat-ball collision, and the science behind the various bat and ball performance metrics used by various baseball and softball organizations (ASA, USSSA, NCAA) and the ASTM standards that specify how those performance metrics are experimentally measured. Each year I received a small honorarium (in the amount of $400 to $600) to cover my travel expenses.

Interaction with Bat Manufacturers at Professional Meetings

Since 2004 I have been a voting member of the ASTM F.26 Subcommittee on Baseball and Softball Equipment. This committee oversees the standards and protocols that all laboratory testing of baseball and softball bats and balls are required to follow. These are the laboratory tests used to certify bats as meeting the ASA 98-mph BBS standard for slow-pitch softball, the NCAA BESR standard for college and high school baseball, and the BPF standard used by USSSA softball and Little League Baseball. My presence on the committee as an academic researcher of general interest is necessary to off set the number of votes by manufacturers. Between 2003 and 2005 I also attended and participated in several annual meetings of the Baseball and Softball division of the SGMA. Through both of these avenues, I have made a number of contacts with the engineers who design bats for all of the major bat manufacturers and many of the minor bat makers. I have presented some of my research findings at several of these meetings - always in a completely open fashion. But, there is no coercion, no attempts to influence my personal research projects or my research findings.

I Don't Always Say or Write What Bat Manufacturers Want To Hear

Disagreements with Bat Manufacturers and Organizations

In the June 4, 2007 issue of USA Today I was quoted as completely disagreeing with a representative from Easton regarding the facts about how fast metal baseball bats hit balls. The Easton rep claimed that the BESR standard ensures that metal and wood bats hit balls with the same maximum batted-ball speed, and he stated that all Easton bats hit balls with the same maximum speed as wood bats (97mph). I argued that the BESR standard used to NCAA to regulate the performance of baseball bats allows metal bats to hit balls up to 6-mph faster than the best wood bats available. My argument was completely validated in 2008 when the NCAA commissioned an experimental study of over 400 wood, metal, and composite bats and found that a large number of non-wood bats, which passed the BESR bat standard, actually produced batted-ball speeds up to 6-mph faster than wood. I have personally interacted with this particular Easton employee on several occasions at SGMA and ASTM meetings, but that did not prevent me from arguing against his incorrect statement.

On several other situations I have adamantly disagreed in public and in writing and over the phone with spokespersons from SGMA and the Don't Take My Bat Away Coalition regarding the differences between metal and wood bats. For many years both groups (SGMA and DTMBAC) have ardently argued that metal bats hit balls with the exactly the same speed as wood. In contrast, I have argued (and written articles in support of) the truth that metal bats do hit balls faster than wood bats, and that composite bats can even hit balls faster than metal bats, especially if they have been tampered with. It has only been within the past year that spokespersons from SGMA and DTMBAC have publicly referred to my articles as supporting their stance on the metal bat issue. Prior to the experimental data collected by NCAA (showing that metal bats can indeed hit balls up to 6mph faster than wood, and that a well broken-in composite bat can significantly exceed performance limits) and the announcement of adoption of the new BBCOR bat standard, more often than not my articles were at least partially at odds with their public statements.

I have written articles explaining the experimental scientific data clearly shows that metal bats provide several important advantages to a hitter compared to wood, and that composite bats provide additional advantages to metal bats. Not all of those advantages result in balls being hit faster, but I have never argued that metal bats hit balls the same as wood - I have always argued that metal bats can hit balls faster than wood, and have not been afraid to publicly disagree with manufacturers or organizations who say otherwise - even in spite of the fact that I have performed some consulting services for them or received small amounts of funding from them.

Just because a group or person uses an article I wrote as evidence to support their particular stance does not mean that I necessarily agree with the position they are taking. I don't get any royalty every time an article I wrote is mentioned on TV or in a newspaper. And I most certainly did not receive any kind of monetary compensation for any of the articles I have written.

My failed chance at being an expert witness

In May of 2007 I was approached by a lawyer representing Easton and Hillerich & Bradsby in a lawsuit concerning an injury to a player from a ball hit by a metal bat. The lawyer wanted to know if I would be willing to serve as an expert witness in a lawsuit involving metal bats. After meeting with me for several hours to discuss what I know about baseball bats, the lawyer ended up deciding not to ask me to be an expert witness, mainly because I could not say what they wanted me to say. The lawyer even wrote up an affidavit position statement for me to sign - but I refused to sign it because I could not agree with the position they were trying to take. When the lawyer told me they decided not to use me, he told me "my testimony as an expert witness would have done more damage to their case than it would have helped them." The only payment I got out of this experience was a free salad lunch at Applebee's.

Why I Don't Like to Call The Articles Posted on My Website "Research"

On many occasions, I have attempted to explain to people (mostly people who attempt to use my articles incorrectly to support their viewpoint) that the articles posted on my website don't really constitute research. That may seem like a really strange thing to say, and I should probably give up trying to convince people otherwise. But, the truth of the matter is that these articles are not research in the manner that the term "research" is consistently used in the academic community. None of the articles on my website could be published in ar archived research journal. They do not represent my own original work. I didn't conduct a bunch of experimental tests on bats and then study the data. I didn't conduct field trials of players swinging bats. For a couple of articles I did run some computer calculations - but these are things that anybody with a computer and an understanding of the equations for projectiles and air-drag can reproduce. Occasionally I may have brought in a few results from my own research when they are relevant to the question I am trying to answer, but only on rare occasions. Now, I have done, and am still doing, some "legitimate" research on softball and baseball bats that has been and will be published in peer-reviewed research journals. But, the articles on my website are not the same thing at all as this other, more technical, scientific writing.

What I did for the articles on my website is thoroughly read all of the available published literature about the research that other people have done and published regarding baseball and softball bats. Then, I wrote a series of summaries explaining these research findings so that an average person - without a university degree in science - can hopefully understand the experimental data and the science behind it. To quote from the front page of my "Physics of Baseball Bats" website: my articles are

". . .answers to often asked questions concerning the physics of baseball bats. An important distinction for my webpages is that the articles provided below are not opinions, but are based on a thorough reading of the available published research literature as well as results from my own experimental research. A full listing of references is attached to each article so interested readers can look up the facts for themselves."
When I start getting the same question from multiple sources, I do some background reading, gather the information, and write an article that answers the question based on scientific evidence as may be found in the published literature.

I'll be right up front and state that, in my opinion, NONE of the articles I have written (including the one "Should Metal Bats be Banned") should ever be used as supporting evidence either in opposition to or in support of arguments for a lawsuit, court case, or legislative bill. Instead, the original published research articles that I quoted from should be used as evidence. All I am trying to do is to bring the available research and the factual scientific data into the hands of the general public. The vast majority of the scientific data summarized and explained in my articles did not originate with me - I simply read and summarized what other researchers have done.

Things I Have Done to Help Improve Safety in Baseball and Softball

I would also like to offer some evidence that I am not blind to the issue of safety.

General articles about metal and composite bats

Several of the articles I have written tell the truth about how non-wood bats outperform wood, and provide scientific evidence for the advantages of using them. My article about Metal Bats shows that metal bats can be swung faster (though this does not mean they hit balls faster) allowing a player to have more control during the swing, and make better contact the ball. Metal bats don't break on inside pitches. And, because of the trampoline effect - metal bats have a slightly larger area on the barrel where maximum ball speeds may be produced. I also have an article discussing some of the advantages that composite bats provide compared to metal bats (though this article is primarily about softball bats. My explanation of the BESR performance standard used for NCAA and high school baseball bats clearly shows how this standard allows for metal and composite bats to hit balls up to 6-mph faster than wood.

I also have an article that tracks the NCAA Statistics for college baseball since 1970. The data shows clearly how changes in bat design have led to increases in runs per game, home runs per game and batting averages. The data also shows the immediate decrease in bat performance after changes to the performance standards were instituted in 1995, 1998, and 2009. I'll be looking for further drops in bat performance once the new NCAA BBCOR bat standard takes effect in 2011.

Articles about the problems of bat doctoring and bat-rolling

I have written two articles that highlight the dangerous (and illegal) practice of doctoring composite bats. The performance of a composite bat improves as it is used, as the bat breaks-in and the barrel walls start to crack. The performance of a composite bat can also improved through various means of altering the structural integrity of the barrel. My article on Doctored Bats attempts to educate the public about this problem by showing how some people attempt to doctor their bats, and the dramatic increase in performance this can bring about. My article about Bat Rolling discusses the more controversial practice of rolling the barrel of a composite bat to improve its performance. In both articles I am very up front with the danger this represents, why these practices are considered to be illegal, and the increase in batted-ball speeds that altering a bat can produce pComposite bats are very easy to doctor through illegal bat doctoring or accelerated break-in techniques

Project to Detect Illegally Altered Composite Bats

A current project (not funded by any manufacturer or agency) is an attempt to develop a simple to use hand-held device that could be used by an umpire to tap a bat barrel and indirectly measure the trampoline effect from the acoustics signature of the bat. I currently have a couple of students working on this. The data from the SGMA funded Indirect Methods Study has shown that we can correlate the actual field performance of a slow-pitch softball bat with its acoustic signature. Because of the recent increase in problems with illegally altered composite bats (including techniques like shaving and rolling) there is a growing desire for some kind of simple tool that could detect illegally altered bats in the field, before they are used to hit a ball faster than is safe (or at least faster than the specific bat performance standards allow). If our project is successful, we could extend it to be used for youth baseball as well.

Changes to the BPF protocol for LLB

Finally let me offer a couple of additional facts that might demonstrate further that I am not "in the pay" of manufacturers. Little League Baseball recently (October 2008) modified the procedure for their BPF (bat performance factor) bat standard in two important ways. They started scanning along the barrel to find the location where the bat performed the best - instead of simply impacting at one location (the center-of-percussion). They also started rolling bats prior to the certification testing. Both of these changes were the direct result of my strong urging to Little League official Steve Keener that these changes be made. When the BPF test used to be conducted at only one location (center-of-percussion) - as it was for more than 15 years - all bat manufacturers knew how cheat the test. It is very easy to design a bat that performs poorly for impacts at the COP but hits balls much faster at the actual sweet spot. Directly because I was able to convince Steve Keener of LLB, the BPF test was changed for youth baseball, and it is no longer possible for manufacturers to cheat the test - at least through that specific loophole. The practice of rolling composite bats is necessary because composite bats improve with use as they become broken in. We have know this in slow-pitch softball for 10 years, but youth baseball is only just waking up to this fact. In 2009 NCAA placed a moratorium banning composite bats because of this problem - and the NFHS followed suit for high schools in 2010. Again, because of my direct insistence, LLB now breaks in composite bats before testing them to be approved for play. I'm not "in the pay" of any manufacturer . . . I'm after the truth no matter whether people like it or not.

My Personal Opinion About the Metal Bat Issue

What is my personal stance on the metal bat issue? To be honest, I'm not really sure. I would definitely never let my own son pitch without wearing a protective helmet with face-guard - and that would be true whether the bats being used were metal, composite or wood. I am a very firm advocate of the idea that youth baseball pitchers should be required to wear protective helmets. Batters have to wear helmets to protect their heads from pitched balls that reach speed of 70-85 mph, and they must keep their helmets on while running the bases to protect their heads from injuries from thrown balls. Why isn't a pitcher required to wear a helmet when a ball might be hit directly at him at speeds in excess of 90mph?

I do believe that metal and composite bats provide several advantages to a hitter. And, I do believe that metal and composite baseball bats currently approved for play by the NCAA, NFHS can hit balls faster than wood - though according to the experimental data (and there is a lot of it) the difference is only 6-mph, and not the huge speed differences often quoted. Based on my thorough understanding of the physics involved, and the experimental data available, I do not believe that there is enough of a difference in batted-ball speeds between metal and wood bats to argue that banning metal bats is going to solve the problem of safety for teenage pitchers. From the limited published research on pitcher reaction times (coupled with several recent incidents of MLB pitchers being hit by line drives), I'm not convinced that a pitcher has enough time to react to any ball hit directly toward him that leaves the bat at a speed of 90mph or more, whether it was hit with a metal or wood bat. There is definitely a risk involved with standing in the direct line, less than 60 feet away from a hard projectile moving at speeds between 90-100mph, especially when the batter has been trained to "hit the ball as hard as you can right up the middle." Unfortunately the word "dangerous" is not a scientific term that can be quantified or measured. It can only be interpreted through personal opinion.

I do know that these kind of injuries (pitchers being hit in the head by a batted ball) are - while tragic - extremely rare. The statistics of the number of kids playing baseball on any given day, and the number of hit balls that are put into play, compared to the number of pitchers who are injured is extremely minimal. Of course, that doesn't change the fact that these injuries are tragic, nor do those statistics do anything to assuage the grief of parents whose child is injured or killed. However, it is my personal opinion that banning metal bats is an emotional knee jerk reaction that won't solve the problem in the long run.

I also believe that our modern American society is far to prone to file a lawsuit every time an accident happens. Whenever a tragic accident occurs (which is what these injuries really are), our immediate reaction is to search for a scapegoat, to find someone or some corporation (usually with large purses) who must be held responsible for causing this accident, and we file lawsuits to compensate for damages. I personally detest this litigious aspect of our American culture and society.

I do know that I don't really care for the "ping" sound of a metal bat (though it does allow me to "listen" to a simple tap test to determine whether or not one bat has a greater trampoline effect than another). I like the purity of the game as played with wood - I like the idea of manufacturing runs, getting solid base hits to advance runners one base at a time. I like the possibility of exciting defensive plays, and enjoy the thrill of watching a runner stealing a base. Yes, I do enjoy watching home runs, but runs scored from line drives are much more exciting to me.

I am concerned about the problem of composite bats that improve in performance with age - and the more dangerous practice employed by many adult softball players and many parents of youth baseball players, in which a composite bat is modified either through shaving or rolling to the point that the composite bat can hit balls significantly faster than they were designed to. I do firmly believe that the performance of all metal and composite bats should be closely regulated and held to some upper limit of performance. To that end, I am a voting member of the ASTM subcommittee that oversees the laboratory standards for the tests currently used by the NCAA, ASA, USSSA, and LLB to measure the performance of baseball and softball bats.


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