Print-in-place mechanisms that come off the bed already assembled — a cycloidal
drive spinner, a herringbone planetary gear set, a clicky ratchet, and a Geneva stop-motion drive.
Dial in your printer's tolerance with the built-in test print, then every fidget you generate is
tuned to your machine.
drag to orbit · pinch or the buttons to zoom
Mechanism
Not sure? Print the test print below — the tightest spinner that
still turns freely is your number.
More lobes, slower wobble — one knob turn walks the disc 1/7 of a revolution.
Herringbone teeth lock the gears in the shell — no pins, no caps.
Small wheels fit fewer teeth — the stats bar shows what you'll actually get.
More pawls, more clicks per tooth — and a firmer feel under your thumb.
The orange wheel snaps between stops while the drive knob turns — the
same mechanism that advanced film in old projectors.
Print it
Test print: six captive spinners at clearances 0.15 / 0.20 / 0.25 / 0.30 /
0.35 / 0.40 mm, marked with tick lines — one tick is 0.15, six ticks is 0.40. Snap each
one free and spin it; the tightest that turns freely is your printer's tolerance.
Printing notes
No supports, no rafts. Every moving part either sits on the bed or bridges a
gap smaller than 8 mm.
Layer height 0.2 mm works everywhere; 0.12 mm makes the gears feel
silkier.
PLA or PETG. The ratchet pawls flex on purpose — PETG gives them a longer
life if you're a heavy clicker.
First motion is the hardest. Fresh off the bed, twist firmly to crack the
first layer's kiss-welds — after a dozen turns everything frees up.
If a part is fused solid, print the test again with a bigger tolerance; if it
rattles, go smaller.
How they work
Cycloidal: the knob's eccentric cam makes the lobed disc roll around the pin
ring — one knob turn nudges the disc one lobe. Hypnotic wobble, huge reduction.
Planetary: the sun drives three to six planets inside a ring gear. Herringbone
teeth mean the gears cage themselves — the classic fidget gearbox.
Ratchet: leaf-spring pawls ride a toothed wheel and snap into each valley.
The click you can't stop clicking.
Geneva: a pin on the drive wheel catches slots in the orange cross, turning
smooth motion into crisp indexed stops, with a locking disc holding it rigid between
them.