Pearl Pulse

A palm-sized jellyfish that runs on a rubber band. Press the bell 4 mm and the last bead on every strand swings 18.8 mm out.

At rest

8 strands of 8 beads hang from 8 pivots under the bell. 114 separate solids, 48 print jobs, no screws and no glue.

The press

The bell is the top of that sliding ring, not a button. Push it and the ring runs down the stand until it meets its stop on the carrier, 4 mm later.

The reach

Every root turns 34.8° about its own pivot — 8 of them, one every 45° — and the strands swing outward and lift as they go.

The shell lifts off

A 12° turn on three posts and the bell comes away. Everything that moves is underneath it, held by 11 identical flat clips.

One turn, one pulse

Take the frame away: the pulse is a disc that is not flat. Tilted 1 mm in every 7, it carries the follower on its 14 mm track the whole 4 mm down and back, once per turn.

One strand

A root and 8 beads, 9 bodies in a single print job. Ø2.4 mm pins sit inside Ø3.2 mm eyes with 0.4 mm of clearance, articulated straight off the bed.

bell0.0 mm
last bead0.0 mm

4 mm down at the bell, 18.8 mm out at the tip

Pressing the bell slides a ring down the stand. The 8 roots do not move with it: each one is a single rigid piece pinned to the fixed frame 29 mm out from the axis, with a 7 mm horn pointing inward and an 18 mm arm hanging below. The ring catches the horns and takes them down; the arms swing out. That is the whole multiplication — no gears, no levers stacked on levers.

Let go and two rubber loops pull the ring back up. In the pressed pose the run itself authored, the bend is spread across the first 5 joints rather than folded at the top — no joint turns more than 6.97° — so a strand curves out instead of kinking at the root.

Pearl Pulse at rest: eight bead tentacles hanging straight down under a scalloped pearl bell.
At rest. The strands hang straight inside the width of the bell.
The same object pressed to its stop, every tentacle swung outward and lifted.
At the stop. Each root has turned 34.8°; the last bead stands 18.8 mm further out and 4.8 mm higher.

The pulse is a disc that is not flat

A rubber band runs up the inside of the hollow stand, from a bayonet anchor under the foot to a hook on the shaft, and turns a face cam under the bell. Its working face is tilted 1 mm in every 7, so a ball-ended follower on the 14 mm track is lowered and raised the full 4 mm once per revolution — one pulse per turn, slowed by a film of damping grease in the cup above it so the whole thing ambles rather than snaps.

Press the bell by hand and the follower simply lifts away from the cam. There is no clutch to disengage and nothing to wind first; the hand press and the motor drive the same ring.

The bell lifted away, showing the fixed frame, three bayonet posts and the drive stack at the centre.
Service. The shell unlocks with a 12° turn on three posts and lifts straight off. The cam, cup and shaft come out from above; the 11 flat clips are all the same part.

48 print jobs, 114 separate solids

None of the joints are assembled. A tentacle arrives as one job of 9 bodies — a root and 8 captive beads laid out flat, each Ø2.4 mm pin already sitting in its Ø3.2 mm eye with 0.4 mm of clearance around it. The strand comes off the plate already articulated, and the only thing you owe it is not to force a bead that has fused.

The bell is one shell in three colours, printed crown-down with its blush and mist regions registered at a shared origin rather than snapped together from wedges. 4 colours in all — pearl, blush, mist and lavender — one PETG family for the lot, which is what the build notes ask for.

One tentacle as it is printed: a root and eight beads in a line, laid out flat.
One strand, off the bed. 9 bodies in a single job, printed at a slight zig-zag so no gap closes on the first layer.
The bell alone, showing sixteen shallow scallops and the co-printed blush and mist stripes.
The bell. 16 shallow scallops around a 1.2 mm wall, with the two accent regions bonded into the shell as it prints.

The parts that are not plastic

One closed rubber loop — about 70 mm doubled, cut from 4 × 1 mm strip — hooks between the anchor under the foot and the shaft above it. That is the motor. Two smaller loops, about 56 mm around, are the return springs that lift the ring. A thin film of damping grease on the cup's working annulus is what stops the cam unwinding in one go. Wind clockwise from below, no more than 16 turns from relaxed, and let the key go.

About 30 seconds of pulsing from a full wind is the design target, not a measured result. This design's CAD was checked for fit, wall thickness and clearance; it was not run, and no sound, runtime or fatigue was tested. Rubber and grease vary, so the band tension and the grease charge are yours to settle at the desk.

The numbers

Overall size
3.2 × 3.2 × 4.6 in
Weight
2.4 oz
Print jobs
48one of them a 9-body strand, printed 8 times
Separate solids
11464 of them beads, captive from the first layer
Filament
4 PETG colourspearl, blush, mist, lavender
Nozzle and layers
0.4 mm nozzle, 0.16 mm layers
Bed
220 × 220 × 220 mm
Print time
about 10.3 hours
Bell travel
4 mm to the stop34.8° at every root
Winding
no more than 16 turns from relaxed
Not printed
one motor loop, two return loops, a little damping grease