( h o w . t o . m a k e ) something big

gershon dublon
responsive environments group :: MIT media lab

using a waterjet cutter and a shopbot mill

This week we learned about the waterjet cutter and shopbot CNC mill. Our assignment was to make something big(ger). I thought about making a xylophone, inspired by this guy. As it turned out Laurel had the same idea, and was further along in its development, so I decided to follow her progress while making a tongue drum.

Laurel and I went to Home Depot and a lumber yard to get materials: glass because we were both interested in glass xylophone keys, PVC pipes for resonators, and some hardwood for my tongue drum top. I settled on mahogany, and bought more material than I should have.

Designing lengths for resonating bars with some semblance of relative pitch can be confusing, but the free-bar length calculator on this website makes it easy. I mapped out a design using the relative lengths given by the calculator and cut it on the waterjet. John advised me to cut without submerging the wood and immediately dry it, so as to avoid warping. The waterjet is incredible and horrible-- the laser-cutter's loud, splashy uncle.

Right off the waterjet, the drum was completely damped and nearly silent, and I realized that the wood was too thick (0.9") to resonate. I brought it over to the shopbot and Tom helped me mill (plane) off about a third of its thickness. I should have gone through that step first, because the vibrating material left deep cuts in the wood. Several hours worth of corrective sanding later, the drum was starting to sound. I cut parts for a resonator box on the bandsaw and glued them overnight, and the drum finally worked! It's amazing what a difference a resonator makes. The drum still needs sanding (to clean off some stray glue) and finishing, but it sounds pretty good. The keys don't vibrate as independently as I would have liked, instead playing distinct chords on either side of the drum. Recordings are forthcoming.

I also made some other models, traced from a tongue drum design that appeared in an issue of Wood Magazine, but haven't put them on resonators yet. The aluminum cut is intensely loud when struck, with overtones everywhere, almost like a gong.

The aluminum one:

The wooden one:

> tongue drum designs (adobe illustrator)
> tongue drum designs (dxf)

mas863 2009