Electric Rubber Band Bass

If, like me, you often made some variation of a rubber band instrument during childhood, mine often consisted of multiple rubber bands stretched around an empty tissue box, then perhaps you are also curious to revisit their musical potential. With access to a 3D printer and a deeper understanding of the construction and amplification of musical instruments, I wanted to create a musical instrument that met the following criteria:

• Utilises 3D printed parts as well as existing material
• Is easy to assemble
• Has the ability to change in pitch
• Is easy and fun to play
• Can be amplified

• Access to a 3D Printer
• Large Rubber Bands
• Broom Handle

Using the free browser-based 3D modeling software Tinkercad, I started by 3D modeling a housing around the components that will make up the amplification system of the instrument: a 27mm piezo element and an enclosed ¼’’ audio jack.

The goal was to create a housing with a relatively small footprint, broken into two indexable halves, which could later be permanently assembled after the electronics were installed.

To meet the criteria of pitch variation, I looked around to see what I could utilize as the main body of the instrument. After a brief search, I settled on… a broom handle! This led immediately to adding a corresponding female broom handle thread (either ¾’’ x 5 TPI or ¾’’ x 4 TPI) onto the amplification housing.

Next, I added a bridge to the amplification housing. This bridge spans across the piezo element pickup and has two indentations onto which the rubber band ‘’strings’’ will rest. I then added a stop-tail of sorts onto which the rubber bands can be affixed.

The next component to tackle is the moveable headstock of the instrument. I started by creating a cylindrical sleeve that fit loosely around the broom handle. A quick way to the test the fit around the broom handle is to print out a test version of the tube shape that is only a few millimeters tall, as it only takes a few minutes to print and you can ensure a perfect fit. To this tube shape I added hooks for the rubber bands to attach to and small finger rests to help grip the headstock while playing the instrument. With that completed, I sent all the pieces off to my slicing software then to the 3D printer!

After a few hours, I had all the components I needed and could start assembling everything. I started by soldering the leads coming off the enclosed ¼’’ audio jack to the piezo element. The piezo I used was salvaged which is why there is some adhesive residue on it. A word of warning about piezo elements, they're fairly fragile and require care when soldering to them. Keep the interactions with the iron brief or solder on a heat sink to avoid damaging it. It’s important to test your circuit to make sure that it works BEFORE installing it into the housing. After testing the circuit, I installed the jack into the housing.

Next, I glued in the piezo element, and tucked the wires away into the voids of the housing before gluing both corresponding halves together with CA glue.

Once it dried, I attached two large rubber bands to the stop-tail on the housing by looping them through themselves. This secured the rubber bands and enables me to easily swap them out.

Once the rubber bands were securely installed, I then screwed the housing onto the end of the broom handle. Lastly, I slid the headstock onto the broom handle and attached the rubber bands to its hooks.

After playing around with the new rubber band instrument for several minutes, I realized that I could plug it into my amp stack! At last, the rubber band’s potential as a legitimate musical instrument was realized! The best part about creating your own instruments is that you immediately become the best player of said instrument whilst simultaneously also becoming the worst.

Make several, and rock out with your friends in your new RUBBER BAND!

Cheers!

Mr. Ham