[Henk Rijckhaert] recently participated in a “secret Santa” gift exchange. In a secret Santa, everyone’s name goes in a hat, and each person must pick a name without looking. Each gives a gift to the person whose name they drew.

Henk needed a gift for Amy, a friend who loves the water and water sports as well as maker-y things.  So he built her a wave automaton — a sea wave and fishies, and documented the build in this video.

The build is mostly plywood and 3D printed parts. We have to  think reprising it in a nice wood and brass would make a lovely project for a hobby wood and metalworker.

The bulk of the project is 30 plywood boards stacked up with spacers. Each board is mounted with a 3D printed stepped bushing on one end that rides in a horizontal slot. On the other end is a 3D printed eccentric riding in an oversized (about 5cm) hole. So the board moves in a circle at one end and back and forth at the other for a very nice simulation of an ocean wave.

The eccentrics all ride on a common shaft, but are offset in phase. He has a nice technique for setting the phases. Each eccentric has 3 small holes on a radius centered on the shaft. Toothpicks go in two of the holes, passing through holes 2 and 3 of the lower eccentric and holes 1 and 2 of the upper eccentric. 3D printed gears and hand crank drive the system.

The wave is fun, but a bit plain. So he 3D printed some flat fishies, glued them on brass rod, and epoxied the rods to the mechanism. Now the fishies jump in arcs out of the water as the shaft turns. The video isn’t clear, but we think they’re on the small ‘slot’ bearings.

There are a few interesting construction details. The 3D printed gears transmit torque to their shafts via nyloc nuts press fit into a hex hole. The handle transmits torque via a hex head bolt press fit in a 3D print.  The epoxy surprised us – there doesn’t seem to be any mechanical support for the brass rod. This might be us, as the video is in Dutch, and our Dutch is limited.

If you liked this build, check out the 3D printed water droplet automaton.