Ballerina Music Box | ENGI 210: Prototyping and Fabrication

Welcome to a dive into Alessa Elkareh and Zekiye Kaya’s EDES 210 midterm project!!

Gate 1:

Our inspiration for the project was to create a mechanical music maker like the metal one below but with an antique feel like the ballerina box next to it!

This device consists of a metal sheet with perpendicular cuts of different lengths. This is what allows for the different notes in the song. It also contains a rotating barrel with spikes which are placed on the barrel according to the length and order of the notes.

At first we wanted to create a copy of the metal contraption, however, with the constraints of this project it would not have been possible. We then decided to change the aspect of the machine that is rotating. By having the metal sheet rotate we were allowed to make the barrel a disc instead. Below is a picture of our sketch!

As seen in the sketch we also decided to include a spinning ballerina and fully committed to the antique look. Below was the final sketch that was submitted! Along with photos of the .ai files made for each of the pieces. The thing only that was not accounted for was the metal sheet because we decided to do more research on it.

After meeting with the TAs and Dr. Wettergreen we decided to make the gears in wood for our Gate 2 submission and to push the metal sheet research until after Gate 3 in order to focus on the mechanisms first.

Gate 2:

For our low fidelity prototype we made the gears in wood and everything else using cardboard and paper! We made some changes, however due to all the pre work done in Gate 1 we didn’t have much to do for Gate 2! We made the holes inside the gears more exact to the sizing of the dowels. We made the top and bottom box using the press to fit box creator on the makercase website: https://en.makercase.com/#/ and adjusting for the kerf found.

After laser cutting all of our pieces on cardboard, we assembled everything together using scotch tape to keep things in place, and using rolled up paper as dowels. Our completed low fidelity prototype is shown below:

Through Gate 2, we were able to see that our gears were working as we wanted them to and our box was structured to our liking, so we were ready to move onto Gate 3.

Gate 3:

We started Gate 3 by testing out the kerf of the wood planks we were going to use. To test for the kerf we decided to have fun with it and we made some dice. We ended up deciding that a .0075 kerf is best!

Before moving on to cutting our box pieces with the wooden planks we had for our medium fidelity prototype, we started putting more focus on the musical components of our project. First, we picked out the song we wanted out music box to play to be Ode to Joy. With our song selected, we were able to plan out the notes in a circular pattern for our metal sheet to hit as shown below:

After having the notes down for a 30 second repetition of the song, we calculated the rpm we would need to have our metal sheet turn to be around 2 rpm. This was calculated with the assumption that the vertical gear we turn would be around 30 rpm. However, translating 30 rpm to 2 rpm with the current gear system we had was basically impossible within the dimensions we wanted, so we needed to redo our whole gear system. We decided to have the 30 rpm translate over to the rotation of the music sheet through a smaller, 4 tooth gear, by stacking two gears on one dowel. The two story gear systems we finalized on are as shown below:

With our new gear system, our music sheet would be at around 2.22 rpm, which is perfect for our needs.

At this point, we had started to research deeper into how our music sheet will need to be manufactured; however, after only one test cut with the waterjet, the waterjet was out of order. Therefore, we had to continue the rest of our project without the metal sheet that would produce the actual music.

Once our musical components were figured out, we were able to move onto laser cutting our pieces. We updated our box designs from gate 1 to include some vintage designs on our box, as well as to engrave the music notes as a guide for when we would nail the notes in place.

We initially laser cut the box pieces using the dimensions from our gate 1 and 2 designs, which fit together well with one another. However, when we tried to assemble our gear system inside of our box, we realized our new gears were too big for our old box design.

After going back to the box maker website, and inputting the new dimensions of our box, we had a complete medium fidelity prototype assembled.

This prototype allowed us to make all the necessary improvements we would need on our design, and got us ready for our final product.

Final Prototype:

For our final prototype, we decided to keep the box pieces and the gears we cut for our gate 3. This allowed us to save time and materials. With our pieces ready, we sanded everything down with 320 grit sandpaper. We had started off with 120 grit; however, this caused the wood to feel like fabric, so we decided to switch to a greater grit. 320 grit worked perfect to smooth everything out!

After sanding, we stained all of our box pieces, using a darker wood stain. The stain helped bring out the vintage feel we wanted for our box. After staining, we had to measure and cut down the dowels for our gear system. We were also able to tackle the music notes now that our box pieces were completely post-processed. We initially planned on using a nail gun to place the nails into place. However, when doing a test run, we saw that the nails from the nail gun would just fly completely through the wood due to how thin the plank was.

We were recommended to hammer in the nails instead by our TA’s. We found the thinnest nails we could find at the OEDK and got to work. We hammered each nail fully through the plank, and then went back to cut each piece down to an appropriate length. The process can be seen as follows:

With all of our pieces cut, sanded, and stained, we were ready to assemble our final product. We used superglue to place our bearings into our box as well as securing our dowels into the bearings. We then used wood glue to keep our gears in place on the dowels. We had also laser cut some wedges, which we placed between the gears to keep everything evenly spaced.

After the assembly of the technical components of our project, we moved on to the more aesthetic portion; the ballerina. We had been researching throughout this entire process on how we were going to make our ballerina, and we had decided on having a 3D, layered ballerina. To do so, we imported a .stl ballerina file we found online to Autodesk Slicer. We defined the dimensions of our planks into Slicer, edited the dimensions of the ballerina to be 8 inches tall (with everything set to scale), and sliced the design into layers. The 3D design was cut into numbered layers to be cut and assembled together.

Once our ballerina pieces were laser cut, we assembled the layers with wood glue. We wanted our ballerina to have a pop of color, to stand out within all the wood, so we added a blue vinyl sticker around its waist to act as a belt. While it was extremely hard to assemble, the final look of our ballerina was beautiful and sat well within our music box. After gluing the base of out ballerina to the designated dowel, our ballerina music box was done. All the gears in our system were working perfectly together, and would spin the ballerina as well as the music sheet dowel. In the future, we would definitely consider working on the metal sheet to actually have the musical component of our music box be functional! Our final product can be seen below: