Baseball Music Box

October 2018   Bianchini

Project Documents


I wanted to build a unique engineering-focused display for a baseball in a way that would make people laugh. I used this idea for my project in Stanford's class ME203 Design and Manufacturing. My inspiration came from my desire to make a gift for a family friend whose was a Major League baseball player when he was younger, then became an engineer for the rest of his career. Thus, a baseball display with exposed engineering elements would be the perfect way for my friend to display a piece of his young and later life in her apartment.

Motivation + opportunity

I knew I wanted to make something for this friend of mine for a while.  She was one of the key people in getting me interested and involved in engineering at an early age, so engineering something for her made a lot of sense.

Figure 1:  The first sketch I made of this project idea.

During my first quarter at Stanford, I took ME203 Design and Manufacturing, one of the cornerstone Product Realization Lab (PRL) classes.  Stanford does machine shops differently than MIT, which has dozens of separate shops with different equipment for different purposes and available to different subgroups of people.  Stanford has the PRL, which is one expansive, all-inclusive machine shop for any university affiliates to use.  It's pretty impressive, including a casting foundry, welding equipment, forming tools, mills, lathes, CNC mills, CNC lathes, a finishing lab, rapid prototyping tools, and a fully-stocked wood shop.  You can find all of this at MIT, too, just scattered around campus and not always accessible to everyone.

Initial prototype

As a proof-of-concept, I built my first prototype out of Lego Mindstorms.  Though this prototype did not resemble the form I desired for the final product, it had all of the design features incorporated, including the hand-powered crank, rolling the baseball, and playing the music from the music box.

Video 1:  First assembly of Lego Mindstorms prototype.

Video 2:  Including a hand crank on the Lego Mindstorms prototype.

Video 3:  The final Lego Mindstorms prototype could roll a baseball in place and play "Take Me out to the Ball Game," all powered by a hand crank.

This prototype helped me see how likely it would be that I could have the front roller be passive, as in it would only rotate when pushed by the friction against it and the ball.  This worked quite well for this prototype, so I included this in my final design.


Figure 2:  CAD assembly.

Figure 3:  Sketch to help determine the length of the rear shaft.

Figures 4 + 5:  Sketches to help determine the length of the front and bottom shafts.


The music box is mainly composed of a gearbox. This gearbox is powered by the user via a hand crank. This rotary motion turns the rear rollers, which makes a baseball sitting on it start to roll. This baseball’s motion makes the front roller turn as well; otherwise, this front roller is passive. The rear shaft is coupled to the lower shaft via gears. This lower shaft is coupled to the hand crank of the purchased music box. Thus, the user’s hand cranking motion makes the ball roll and the music box play.

Design details

Figure 6:  Sketch of an early design's exploded assembly.

I made Patti’s game with three aluminum plates: bottom, right, and left plates.