Welcome to this week’s installment “From the Dugout” which takes a dive into understanding the optimal bat/ball impact location known as the “sweet spot”.
At Leadbury we are extremely dedicated to growing our own understanding of baseball bat mechanics and helping transfer that knowledge to our customers. Our Engineered to Outperform mindset encompasses everything we do at Leadbury. We have combed through the available technical literature on this topic to bring an easy to understand summary to you.
From the player’s perspective, the sweet spot is the contact point that produces the optimal hit, it often comes along with a crack of the bat and very little vibration. The player can tell very easily when the sweet spot is missed; significant vibration, a different sound and often a broken bat.
To understand what the sweet spot is, and why it is so important to make contact there, we must develop an understanding of the vibrational bending modes of a baseball bat. There are three primary bending modes of a baseball which are determined by a measurement called modal analysis. Modal analysis allows the relative motion of each point on the bat to be measured. The first three bending modes are shown in figure 1.
When the bat strikes the ball, these vibrational bending modes are excited causing the bat to vibrate. The fundamental bending mode has two zero positions as shown in the figure, one roughly six inches from the barrel end and one the same distance from the knob where your top hand grips the bat. The second vibration mode has three nodes, one roughly 4.5 inches from the barrel end, one near the middle of the bat and one at the location of your bottom hand.
The sweet spot is defined scientifically as the region located between the nodes of the first and second modes of vibration, roughly 4 – 7 inches from the end of the bat, indicated by the blue area in the figure.
Contact in this region results in very little vibration and maximum energy applied to the ball. When contact is made off the hands or the end of the bat, the energy is dissipated by the vibration and impact and thus significantly less energy is transferred to the ball. This vibration weakens a wood bat over time, and therefore repeated impacts outside of the sweet spot will eventually result in a broken bat.
The data also shows that Ash exhibits slightly less vibration and a slightly larger sweet spot than maple, as shown by the green and red lines in figure two respectively. The increased flex ring porous woods have compared to the stiffer diffuse porous woods like maple reduces vibration amplitude and increases the distance between nodes. Ash is often described as having more “feel” than maple. The modal analysis shows the larger sweet spot and reduced vibration make ash bats more forgiving and backs up the subjective data players provide.
In conclusion, the fact bat vibration can be accurately measured using modal analysis means the exact location of the sweet spot can be determined. Although this has no direct implications to the player, as a manufacturer it is an extremely important concept to understand, and to the baseball nerds, a cool concept you can explain to your teammates.
The information and figures in this text are a summary of Acoustics and Vibration of Baseball and Softball Bats, a research study conducted by Daniel A. Russell of Pennsylvania State University.