Pipes is a custom “marimba” percussion instrument built for Kyle Harris (Blue Man Group, Ben Levin Group, Boston Drum Lessons), and Curtis Sharhorn. The two drummers wanted to conduct a special “tandem” performance of “Extremes” [credit pending], but they needed a specialized set of pipes to be played in tandem. I designed and fabricated the instrument, while implementing some parametric design features along the way.
The primary design challenges for the project revolved around the fabrication and mounting of the pipes such that they 1) resonated at their desired frequencies, and 2) rang as loudly and clearly as possible. It turns out there is an equation for achieving these properties––the team of us retrieved a handful of journal publications authored by fellow percussion instrument-makers like ourselves.
Regarding the first challenge, I used a standard equation in our literature to derive the lengths of the pipe cuts. I input the pipes' variables into the equation––material, outer dimension, inner dimension, and desired frequency––to output these necessary cut lengths.
For the second challenge, I also used published data to determine how to mount the pipes such that they clearly and uniformly resonate. It turns out that any pipe has a predictable “anti-node” (a point of least resonance) 20% of it’s length from either end. I rapid prototyped cradles to be positioned at these anti-nodes, and generated a baseboard for their positioning.
With these data, I used equation-driving features in Solidworks to automate the instrument’s 3D model and ultimate design. That is to say, a whole new variation of the instrument can be easily generated from the model––pipe lengths, legs, and corresponding baseboard––by a user simply entering a set of desired frequency values (better known as notes) into the model (e.g. a C5 octave). Once entered, pipe lengths are automatically generated in the model, along with their legs correctly positioned at two anti-nodes. Plus a baseboard is generated with proper through-holes for the pipes’ positioning.
After several tests, we ultimately went with 3/4” diameter copper pipe. This stock material had the best sound to it, according to the expert ears of Kyle and Curtis. The legs were 3D printed on a Form 2, while the baseboard was prototyped with MDF on a Shopbot CNC mill.
Fun project. I’m looking forward to seeing how else I might use these parametric features in other musical instrument hardware. For instance, lengths of strings, inner diameters of brass––these hardware features of musical instruments can surely be ported over to my model to generate a new kind of string or wind instrument. Onward!