Team Members
Sponser
JJ Ruby- Houston Astros Senior Director of R&D
Abstract
For this project, the team was tasked with creating a machine that universally holds a Major League Baseball Bat and testing its moment of inertia to find specific differences between bats. The sponsor laid out a set of variables, combined with the MLB rule book of baseball bats, that led to requirements and specifications for the product to be made. In the end, a machine was created that, when the bat was balanced at its center of mass on a V in the machine, a lever would pull, releasing a spring-loaded spinner that would fully constrain the bat to the machine. Once constrained, a touch screen will prompt the weight of the bat and how far the end of the bat is from the V the center of mass is balanced. Once confirmed, the user would rotate the device unit it hits a button, where it will then be released with the MOI recorded and displayed. The universal bat hold showed success in a strong constraint for rotation.
Problem Statment
The Houston Astros need a way to measure the moment of inertia (MOI) of baseball bats—a key factor in swing feel and performance. Current tools only measure weight and length, missing critical data that affects player consistency and injury risk. There is no portable, accurate, or non-destructive MOI measurement device on the market. Our system fills this gap, giving the Astros a tool to optimize bat selection across players.
Requirments
- Portable
- Accommodate MLB bats of various shapes and designs
- Nondestructive – does not mark or damage the bat
- Must measure MOI, must have an electronic display
- Must be powered electronically (plug or battery)
- Doesn’t require external computation
- Must repeat measurements accurately
Specifcations
- Final assembly less than 20lbf
- The maximum bat length it can measure: 40in
- The maximum bat weight it can measure: 4 oz
- The maximum bat diameter it can measure: 3in
- For multiple measurements of MOI relative to major bat axis, results within 1 standard deviation of the mean can have no greater than a 5% error relative to known MOI, and for 2 standard deviations, no more than 10%
Design
The finalized device was fabricated using traditional machining equipment, and early prototypes were 3D printed to test fit and function, enabling rapid design iteration. A manufacturing readiness review and CAD support from experts helped refine the design for manufacturability, including components requiring low tolerancing. Final components were machined from Delrin and aluminum using tools like lathes, mills, and ProtoTRAK CNC to ensure precision and durability. Real-time design adjustments were made during assembly due to material delays, showcasing an agile and adaptive fabrication process.
Testing
| Average MOI (oz*in^2) | Percent Error (%) | Standard Deviation (oz*in^2) |
| Louisville Slugger Genuine RA13CD Houston Astros bat | ||
| 8519.20 | 21.1 | 20.09 |
| Hollow Aluminum Tube (41 in length, 43.3 oz weight) – Calculated MOI: 9207 oz*in^2 | ||
| 10295.66 | 11.9 | 267.04 |
Recommendations for Future Work
If we had an additional six months or another design cycle, we would focus on improving the system’s overall accuracy and ease of use. Actions would be taken to try and reduce the size and weight of the device to enhance portability and make it more convenient for field use. Extended testing across a wider range of bats would allow the system to be fine-tuned for maximum consistency.
Simulation tools such as Finite Element Analysis (FEA) could be incorporated into the design process to support these improvements. FEA could be used to model the spring wire constraint system, validate shoulder screw loading conditions, and predict contact stresses between the spring wire and the shoulder screws. Thread stress in the aluminum mounting plate could also be evaluated to ensure durability under cyclic loading. More broadly, simulation could help optimize the system’s mechanical structure by identifying opportunities to reduce material use, lower weight, and improve stiffness without sacrificing strength. Integrating simulation-based design methods would allow a more systematic approach to enhancing the performance, reliability, and manufacturability of the device.
Acknowledgments
We would like to give a big thank you for all the help and guidance received throughout the semester. We couldn’t have done it without the time dedicated by JJ Ruby, Christopher Muir, Chris Pratt, Jim Alkins, Sam Kriegsman, and Alex Prideaux.
Final Design Review
Additional Photos
