Prototyping a percussion instrument

I had an idea a while ago. I remember seeing an instructional video in which Bill Bruford was playing a complex rolling pattern between his toms and a tongue drum placed on his snare. For clarity, a tongue drum (sometimes called a slit drum) usually looks something like this. You've seen them.

I thought it would be cool to make a circular tongue drum. I played with a number of configurations of rectangular tongues, but finally realized that the shape was calling for a radial arrangement of wedge-shaped tongues instead. Like this.

I have a lot of baltic birch plywood around from cabinet projects, and so I took a first pass at a prototype using one of those panels.

To cut the interior kerfs and allow the tongues to vibrate, I drilled through at the endpoints of the lines and threaded a scrollsaw blade through the hole.

Once the tongues were cut, I cut outside the diameter mark on the bandsaw to complete the rough top. My scrollsaw technique is very rusty, and those inside cuts aren't up to production quality. Better to make the mistakes on the prototype.

I thought I would try pulling a strip of the plywood around the radius by kerfing its backside every half inch.

To cut the regular kerf spacing quickly, I hacked a quick jig onto the tablesaw mitre gauge.

That's a fat roofing nail, nearly a full kerf thick, with its head cut off. Each cut kerf fits over the nail to position the next pass. Very quick, very accurate.

I used the waste from the top as a clamping form to glue the side closed in a rough circle. I had counted on the material curving evenly, but of course it did no such thing.

To try to bring it into round, I cut some spacers and arranged them inside. It helped, but not enough.

I glued the top to the side while it was still clamped to the form.

Finishing Bikes and Trees 3

This is the workpiece in progress, and in pieces.

And this is a closeup of the problematic foot. The deep scoring is from the chuck jaws, which I had previously clamped down on the base in frustration. The bowl had held securely, yes. But.

I considered some options. I could try to turn a jam chuck, remount between centres, and carefully turn the base again. That would give me a good chance at a concentric and nicely flowing base, but given the missing half rim and likelihood of further splitting, the risk seemed too great.

I thought about evening out the distribution of the chuck marks around the diameter and making decorative features out of them, but really, all I wanted to see was the profile.

In the end, I hand-shaped the base with chisels and abrasives. The process was tedious, and the result is not concentric or even perfectly circular, but most of the charm of the profile was preserved.

Instead, I added a pedestal of bike parts. First, I disassembled a very rusty rear wheel from a ladies' cruiser with a coaster brake. I tried the hub as an extension of the profile, but it was too narrow much too soon. I wanted to see the profile flare out again.

So I cut three sections of the rim and affixed them around the hub, one end tucked under the flange and against the hub body, and the other splayed out as a foot. To get an idea of the look, I held them in place with elastic bands.

It looked good, but with three legs the profile depended on the orientation of the pedestal. I didn't like how it looked that way, and so I cut a fourth leg.

I also used the grinder to cut a recess so that the tops of the legs were outside the flange rim instead of inset. The profile of the bowl flowed into the pedestal better that way.

All welded up, I was very pleased with it. I added an 18-tooth freewheel sprocket at the top of the pedestal, which was just the right size to provide a nice finish for the pedestal top and overhang for shadows.

I cleaned the pedestal with a toothbrush and alcohol, then hand sanded the bowl to 400 grit and rubbed in a beeswax finish. I avoided oil because I didn't want to further yellow the sapwood or dull the vivid reds and oranges of the branch endgrain.

I love the contrast between the discoloured, rusty, and worn metal, the soft creamy yellow sapwood, and the explosion of reds and oranges. Sometimes persistence pays off.