Gear Fidget Keychain - Two Meshing Spur Gears
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Two meshing spur gears on posts and a keyring hole. Parametric, built with TrueGeometry Playground commands.
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Model information
- Source
- Printables
- Category
- Other Gadgets
- License
- Creative Commons — Attribution
Gear fidget keychain concept: two meshing spur gears (module 1.5, 12T and 10T) on a 52 x 28 x 2 mm base plate with posts, retaining caps and a keyring loop. Built with native TrueGeometry Playground commands only (no Booleans, no scripts). AI-assisted design.
HONEST STATUS: concept model, not print-tested. 8 separate closed shells (posts and keyring loop overlap the plate and are not fused), 90 zero-area triangles from the gear generator. Centre distance is 17.0 mm (textbook 16.5 mm + 0.5 mm backlash): measured minimum tooth clearance 0.20 mm, no tooth overlap. Gear bore 4.0 mm on 3.6 mm posts, gears 0.4 mm above the plate. Keyrings are a choking hazard for small children.
Full write-up with images and FAQs: https://blog.truegeometry.com/0_0_0_0/blogs/post-d6c4edf7.html
FULL PLAYGROUND COMMAND RECIPE (open https://www.truegeometry.com/CoreWebGLTG/KBEAgentHTTP.html, type one line at a time into the chat box; lines starting with # are comments):
# Gears: module 1.5. Argument order observed: module teeth thickness pressure_angle bore_radius
/gear spur 1.5 12 3 20 2
/tag_last GearA
/gear spur 1.5 10 3 20 2
/tag_last GearB
# Textbook centre distance = (12+10)/2 x 1.5 = 16.5. Measured tooth clearance there is only 0.02 mm (would bind),
# so the centre distance is opened to 17.0 mm: measured minimum tooth clearance 0.20 mm (the backlash allowance)
# Rotate B half a tooth pitch (360/10/2 = 18 deg) so a tooth meets a gap
/move @GearB 17 0 0
/rotate @GearB 0 0 18
# Posts: cylinder args = radius_top radius_bottom height. Dia 3.6 in a 4.0 bore = 0.2 mm clearance per side
/parametric cylinder 1.8 1.8 5.3
/tag_last PostA
/rotate @PostA 90 0 0
/move @PostA 0 0 -0.35
/parametric cylinder 1.8 1.8 5.3
/tag_last PostB
/rotate @PostB 90 0 0
/move @PostB 17 0 -0.35
# Retaining caps dia 6, 0.4 mm above the gear faces
/parametric cylinder 3 3 0.8
/tag_last CapA
/rotate @CapA 90 0 0
/move @CapA 0 0 2.3
/parametric cylinder 3 3 0.8
/tag_last CapB
/rotate @CapB 90 0 0
/move @CapB 17 0 2.3
# Base plate 52 x 28 x 2, top face 0.4 mm below the gears (Z -3.9..-1.9)
/parametric box 52 28 2
/tag_last Plate
/move @Plate 8.5 0 -2.9
# Keyring loop: torus major radius 5, tube radius 1 (hole dia 8, outer dia 12), flush with the plate thickness
/parametric torus 5 1
/tag_last KeyRing
/move @KeyRing -21 0 -2.9
# Export
/export_stl all
To customise: keep the module equal on both gears, centre distance = (z1 + z2)/2 x module + ~0.5 mm, rotate the second gear 180/z2 degrees about Z.