Cookie Tin Banjo and 3D Printed Banjo

We are Alejandro Higuero Ruiz and Pablo Díaz Urbano, two engineering students at the University of Malaga and this is our project for Acústica Musical. In this project we wanted to test the importance of materials when making an instrument. In our case we chose a banjo. The banjo was a good instrument to try this on as it produces sound through vibrations in the strings, traveling through a wooden bridge to the surface of the body. Therefore the material of the box (body) affects the sound of the banjo a lot. In the following instructions, we explain how we made our two banjos.

1. 3D printer
2. Cords (we used bronze acoustic guitar cords)
3. Wooden Bridge
4. Tuning pegs
5. Cookie tin
6. Some screws (different types and sizes)
7. A plank of wood
8. Some tools like a drill or a saw

Except the tools every other supply we found it on Amazon

The first step was measuring everything; the plank of wood (to make the neck long enough), and the cookie tin (to make the 3D printed box the same size). When making the 3D printed box, we made sure to leave a hole wide enough to pass the neck through.

As both banjos have the same neck, this process was repeated for the second banjo.

Next, we had to prepare the headstock. This is where the tuning pegs are attached, so we had to make holes to put them in and make room for the nut (the raised section between the headstock and neck). In our design, the nut is made of a bolt. At the end of the neck, we made three tiny holes to pass the strings through, and made dents in the wood to keep them straight.

To prepare the cookie tin, we just needed to make a hole with the same size as the neck, and then screw both parts together.

Now that we had every individual part ready, we had to assemble it. Again, this process was the same with both banjos, so we did this twice.

Once both necks had their respective boxes, we passed the strings through the holes and the tuning pegs, making sure they stayed straight, but we didn’t tension them until we had put the wooden bridge and nut in place. The wooden bridge had to be placed a little below the middle of the tin. Once the nut and the wooden bridge were in place, it was time to tune the strings. These two pieces stayed in position thanks to the tension of the strings, so we didn’t have to worry about screwing them in.

This is a friend playing both banjos and you can tell the difference between the sound they make.