Motorized Kinetic Wave Sculpture - 24-Cam Travelling Sine Wave Desk Automaton, N20 Motor

A desk sculpture with an ocean wave that never stops rolling. A small N20 gear motor turns a camshaft with 24 eccentric cams. Each cam is set 15 degrees further round than the one before, so the 24 sliders riding on them always form exactly one full sine wave. As the shaft turns, that wave travels along the row. Each slider carries a geometric breaking-wave crest with a white foam cap, so the top looks like a curling ocean wave in four shades of blue. The camshaft is behind clear windows in a white case on a walnut-look base. Every part prints without supports.

**How it works** - Camshaft: a printed 8 mm hex shaft carries 24 round eccentric cams (42 mm discs, 12 mm off-centre, 24 mm of lift) at a 9 mm pitch. The motor shaft plugs straight into a D-socket in the end of the shaft - Followers: flat-footed sliders resting on the cams. A round cam under a flat foot gives a true sine-shaped lift. Each slider is guided by two slotted combs 40 mm apart, so it stays upright - Gravity return: the sliders just rest on the cams and drop back down under their own weight, so there are no springs - Balanced load: the 24 cams are spread evenly round a full turn, so while half the sliders are being lifted, the other half are coming down. The motor only has to overcome friction

**Cams that set their own phase** - There are four cam types, A, B, C and D (6 of each), with the hex bore turned 0, 15, 30 or 45 degrees. Each cam hub has a small peg that only drops into the next cam's hole when that cam sits exactly 15 degrees further round - Slide them on in the order A B C D A B C D... and turn each one until it drops flat onto the peg. If a cam will not sit flat, it is the wrong letter. The letters and 1-4 dots are engraved on every cam

**What is in the kit (21 STL files; the number to print is in each file name)** - Walnut: base in two halves (304 x 120 mm in total, hollow for the battery box) joined by 2 butterfly keys, motor cover and switch cover - White: motor end plate (with a pocket for the N20) and idler end plate, 2 window frames, guide comb, top deck, hex camshaft, 24 followers, 24 foam caps - Navy: 4 cam types (6 of each) and 2 shaft collars - Blue: 24 breaking-wave crest tiles. Print 6 each in four blues for the gradient shown, or all in one colour - Clear: 2 window panels (clear PETG, or cut them from 1.5 mm clear PET sheet using the STL as a template) - Tolerance test coupon

**Tolerance test coupon (prints in about 14 minutes)** - Print it first. It has the cam bore (slide fit), the collar bore (press fit), the N20 gearbox pocket, the follower guide slot (running fit), the crest-tile socket (press fit), the N20 D-bore and the cam peg hole, plus a short sample of the 8 mm hex shaft and the 4.5 x 8 mm follower stem to try in them. If anything is too tight or too loose, adjust your flow or horizontal expansion before printing the big parts

**Hardware you need (not included)** - 1 x N20 gear motor, 6 V, 15-30 rpm, 3 mm D-shaft (12 x 10 mm gearbox). A 15 rpm motor gives a slow, calm swell; a 30 rpm motor sends one wave along the row every 2 seconds - 1 x 4 x AA battery holder (fits inside the hollow base), or a 5 V USB lead (the 6 V motor runs a little slower on 5 V) - 1 x SS12D00 mini slide switch and a little wire - 4 x M3 x 20 screws (end plates, from below), 4 x M3 x 16 screws (covers, from below), 8 x M3 x 10 countersunk screws (window frames) - Glue for the foam caps, butterfly keys and clear panels. Optional: rubber feet (12 mm) and a little dry PTFE or graphite lubricant on the cam rims

**Designed and checked** - The camshaft was turned through a full revolution in 72 steps in CAD, with all 24 cams, followers, crest tiles and foam caps checked against the combs, deck, frames, panels, end plates and each other at every step: no collisions, at least 0.30 mm running clearance everywhere. Every foot stays on its cam (contact gap 0.00-0.02 mm at every step) - Gravity return: the followers stay on the cams up to about 250 rpm, far above the 15-30 rpm the sculpture runs at - Jamming check: the sliders do not self-lock at any cam angle, even with very sticky friction (coefficient 0.5) - Torque: about 0.3 kg.cm with dry PLA, up to about 1.1 kg.cm if everything is very sticky. A 15-30 rpm N20 gives several times that - Fits used: press fits 0.10-0.12 mm per side, slide fits 0.20-0.25 mm per side, running clearances 0.30 mm

**Size** - About 30 x 12 x 22 cm assembled, with 24 crest tiles moving up and down 24 mm

**Colours** - The 3MF has five colours: walnut base and covers; white case, shaft, followers and foam caps; navy cams; blue crest tiles; clear windows. Each foam cap is dovetailed onto its tile and lies flat beside it on the print bed, so a multi-colour printer can print the tile and foam cap as one part

**Printing** - No supports needed. Designed and slice-checked in PrusaSlicer (0.4 mm nozzle, 0.2 mm layers, 3 walls, 15 percent infill): all 21 files slice clean without supports. Use a 5 mm brim for the hex shaft and the two covers - About 890 g of filament for one complete sculpture (white about 330 g, walnut about 230 g, navy about 137 g, blue about 107 g, clear about 89 g) and about 78 hours of printing - You need a bed of at least 235 x 210 mm (the window frames are 231 mm long, the shaft 237 mm) - The cams, followers, crest tiles, foam caps, combs, frames, panels and shaft all print flat. The end plates print lying down. The base halves and top deck print upside down, and the covers print upright - PLA or PETG

**Assembly** - Push the butterfly keys into the underside of the two base halves (with a little glue), then screw both end plates on from below (4 x M3 x 20) - Put one collar into the motor plate bore from the outside, flange out. Push the hex shaft in through the idler plate. Inside the case, slide the cams onto it in order (A first, hub and peg toward the idler end, then B C D A B C D...), turning each one until it drops onto the peg of the one before. Press the shaft into the motor-side collar, then press the second collar on at the idler end, leaving a paper-thin gap - Press the N20 into its pocket from outside, turning its shaft so the flat lines up with the D-socket - Glue the clear panels into the window frames and screw both frames to the end plates (8 x M3 x 10) - Feed the 24 followers up through the guide comb from below and lower the comb onto the cams, with its end tabs sliding down the channels in the end plates. Put the top deck over the stems - Glue the foam caps onto the crest tiles and press the tiles onto the stems, lips to the front - Glue the switch behind the window in the switch cover, wire motor, switch and battery holder, and screw both covers on from below (4 x M3 x 16). Turn the shaft once by hand, then switch on

Note: original design built from scratch in Blender; designed and slice-checked in PrusaSlicer, mechanism checked for collisions in CAD; this exact version has not been test-printed yet.