Data Analysis

We analyzed our data in MATLAB. One of the main findings of this is that each bat is unique. Our MATLAB script generated several plots: Amplitude vs. Oscillation, Amplitude vs. Distance Away From Bottom of Bat, Frequency of Oscillation vs. Distance Away From Bottom of Bat, and Amplitude vs. Frequency of Oscillation. As you can see below, each of the four bats we tested is different. The "Sweet Spot" is the point at which the vibrations are minimized (smallest amplitude) and the oscillations are quicker (larger frequency of oscillation).

BAT 1 (Cupped)

BAT 2 (Cupped)

BAT 3 (Non-Cupped)

 

BAT 4 (Non-Cupped)

Test Procedure and Results

Our test rig allowed a ball to be swung from a pendulum from 11 different heights which corresponded to hitting the bat in 11 different spots. These spots were from 0-10 inches away from the bottom of the bat. For each trial, a ball was released from 40 degrees to ensure that the bat would be hit with a constant force. While the ball was released, the accelerometer that was mounted to the handle of the bat was turned on, recording 3 seconds worth of data.

The data that came from our testing was raw accelerometer data in the X, Y, and Z directions. The data was “raw” because it was unprocessed values that came straight from the accelerometer. Over the 3 second period that each test was being administered, the accelerometer took 300 readings in each the X, Y, and Z directions. The next step is to process that data and further analyze it to find the sweet spot of each bat.  

Test Rig

Our test rig was designed on the principle of a pendulum. We chose this for two reasons, first was for its ease of repeatability with consistent results. Secondly it allowed us to hit the bat at different locations while providing a consistent force. When a pendulum of the same length is released from the same angle it will strike the bat with the same force. In order to strike the bat at different locations the height of the pendulum was raised while holding the length of the pendulum. Each bat was hit at one inch increments for the lower third (barrel part) of the bat starting at the bottom of the bat. This procedure was repeated for each bat. More information about pendulums can be found here.

3D Printing

We utilized 3D printing to create a part for our testing rig that would be too expensive to purchase and too difficult to manufacture. It saved us a lot of money and time to make a way to connect the bats to the testing rig. To get a part 3-D printed what you first need to do is create a model of your part. Once you have made your part you have to follow a specific procedure to convert into an .stl file, (the file format for 3-D). You must go to either your export button, or save as button and click .stl. Once you choose that setting it will ask you how rendered you want your part. Then just save your file. This is demonstrated in the Tutorials section.

3D Model 

Printed Part

Bat Holder in Testing Rig

Arduino

We are using an Arduino Uno to acquire our raw accelerometer data. Utilizing the Arduino coding environment, code was developed to read the accelerometer and send the data to a PC where it can be processed and further analyzed in MATLAB. The code developed for our experiment can be found in the Tutorials section.

Accelerometer in Housing

Arduino Uno

Both Attached on Bat in Testing Rig