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Geneva drive: 4 and 6 station wheels, R30, with drive discs

How do I make a Geneva drive with 3D printed parts? · Hardware · basis: Geneva geometry: centre distance c = R / cos(π/n), drive pin radius R·tan(π/n); Ø5 pin, Ø5 shafts

Long Earth Society build part. Indexing drive, shelf part for LES rigs. The engines

Exact dimensions. Every file is drawn at true size with no printing tolerance. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your printer's or process's clearance before making the part. Mating features

sizes
2 in table

Notes

  • Turns continuous rotation into steps: the wheel indexes 360/n degrees once per turn of the drive, then is held by the drive's locking disc until the next index.
  • Wheels are R30 × 6 with 5 mm slots for the Ø5 drive pin. The drive is a 3 mm base plate carrying the locking disc and the pin; the wheel runs in the plane of the disc and pin, 3 mm above the base.
  • The locking arcs on the wheel are 0.3 mm larger than the locking disc: a designed gap, keep it.
  • Checked over a full turn of the drive for both wheels: pin, disc and wheel never overlap.

Sizes

stationsindex anglecentre distancedrive pin radiuslocking disc radius
490°42.4 mm30.0 mm26.0 mm
660°34.6 mm17.3 mm13.3 mm

Mating features

Drawn at the exact size. Open press, slide, run and socket features by your process's clearance; leave designed gaps and clamp fits as drawn.

featureexactmates withfitfiles
wheel and drive boresØ5Ø5 shaftspressall
wheel slots5Ø5 drive pin (slides in them)slidegeneva-*
locking arc gap0.3drive discdesignedgeneva-*

Where the files are

Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.

WikipediaGeneva drivewebCC BY-SA 4.0 (text)
Long Earth SocietyEngine and rig builds on extrusion framesweb, videoLES site

Free files

★ Free files 4 parts. Generated by Xem Studio from the standard; threads are plain cylinders at major diameter. CC BY 4.0. index.json

geneva-4-wheel-r30Geneva wheel, 4 stations, R30, 5 mm slots, Ø5 boreSTEP · STL
geneva-4-drive-r30Geneva drive for the 4-station wheel: 3 mm base with arm, R26.0 locking disc and Ø5 pin at R30.0 in the wheel's plane, Ø5 bore (centre distance 42.4 mm)STEP · STL
geneva-6-wheel-r30Geneva wheel, 6 stations, R30, 5 mm slots, Ø5 boreSTEP · STL
geneva-6-drive-r30Geneva drive for the 6-station wheel: 3 mm base with arm, R13.3 locking disc and Ø5 pin at R17.3 in the wheel's plane, Ø5 bore (centre distance 34.6 mm)STEP · STL

Plain text: sheet.txt · JSON: /api/geometry?object=geneva-drive

Geneva drive: 4 and 6 station wheels, R30, with drive discs, isometric render of a generated part
Render of geneva-6-wheel-r30 from the free STEP; not to scale.

How it fits

Goes in or on

Stirling shafts and rodsØ5 shafts for wheel and drive

Alternatives

Ratchet wheels and pawlstep motion driven by a rocker

Also needed

Ball bearings, 683 to 6210 and flanged F6xx625 bearings for the Ø5 shafts

You might also need

Spur gears, involute 20°: module 0.5, 1 and 2, 12–60 teeth, isometric render of a generated part
Spur gears, involute 20°: module 0.5, 1 and 2, 12–60 teeth21 sizes★ 21 files

Questions

What centre distance does a Geneva mechanism need?

C = R / cos(π/n): for a 6-station wheel of R30, 34.6 mm; the drive pin sits at R·tan(π/n) = 17.3 mm from the drive centre.

How long does the wheel stay still?

For n stations it moves during (180 − 360/n)° of each drive turn: 90° of 360 for 4 stations, 120° for 6.