{
 "version": "2026-10-20",
 "license": "Dimension sheets are written by Xem Studio from the cited sources and are free to use (CC BY 4.0, attribute 'Xem Studio'). Linked files belong to their publishers under the license shown; Xem Studio does not host them. 'license_verified: false' means the license shown is from memory or the publisher's page as last read and should be confirmed at the link before commercial use.",
 "slug": "ratchet-and-pawl",
 "name": "Ratchet wheels and pawl (anti-reverse / one-way drive)",
 "kind": "hardware",
 "category": "Hardware",
 "group": "Stirling & thermoacoustic",
 "year": null,
 "question": "How do I design a 3D printed ratchet and pawl?",
 "tags": [
  "ratchet",
  "pawl",
  "one-way",
  "mechanism",
  "reel",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "ratchet stl",
  "pawl design",
  "anti reverse ratchet",
  "fishing reel ratchet",
  "one way clutch 3d print",
  "ratchet wheel"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 4,
 "url": "https://xemstudio.com/objects/ratchet-and-pawl/",
 "sheet_txt": "https://xemstudio.com/objects/ratchet-and-pawl/sheet.txt",
 "sheet": {
  "basis": "Sawtooth ratchet: tooth depth 3 mm, 85/15 flank split; pawl pivot 3 mm; dimensions chosen for printing at 0.4 mm nozzle",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Ratchet tooth: the drive face is radial, the back face slopes; the pawl must contact the drive face at or below the tooth tip so load pushes it deeper, not out. Pivot the pawl so its contact point trails the pivot by 10–15°.",
   "12 teeth = 30° steps (coarse, strong); 24 = 15°; 36 = 10°. Spring: a printed cantilever or a 0.5 mm music-wire torsion spring on the pivot.",
   "Where it goes: fishing-reel style anti-reverse, hand-wound starters, a one-way drive between a Stirling flywheel and a generator so the generator never back-drives the engine."
  ],
  "table": {
   "columns": [
    "part",
    "teeth",
    "step_deg",
    "od_mm",
    "bore_mm"
   ],
   "rows": [
    [
     "ratchet-12t",
     12,
     30,
     40,
     5
    ],
    [
     "ratchet-24t",
     24,
     15,
     40,
     5
    ],
    [
     "ratchet-36t",
     36,
     10,
     40,
     5
    ],
    [
     "pawl-24",
     "—",
     "—",
     "24 long",
     3.2
    ]
   ]
  }
 },
 "sheet_text": "Ratchet wheels and pawl (anti-reverse / one-way drive) — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/ratchet-and-pawl/  (CC BY 4.0)\nBasis: Sawtooth ratchet: tooth depth 3 mm, 85/15 flank split; pawl pivot 3 mm; dimensions chosen for printing at 0.4 mm nozzle\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Ratchet tooth: the drive face is radial, the back face slopes; the pawl must contact the drive face at or below the tooth tip so load pushes it deeper, not out. Pivot the pawl so its contact point trails the pivot by 10–15°.\n- 12 teeth = 30° steps (coarse, strong); 24 = 15°; 36 = 10°. Spring: a printed cantilever or a 0.5 mm music-wire torsion spring on the pivot.\n- Where it goes: fishing-reel style anti-reverse, hand-wound starters, a one-way drive between a Stirling flywheel and a generator so the generator never back-drives the engine.\n\npart  teeth  step_deg  od_mm  bore_mm\nratchet-12t  12  30  40  5\nratchet-24t  24  15  40  5\nratchet-36t  36  10  40  5\npawl-24  —  —  24 long  3.2\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Wikipedia: Ratchet (device) — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Ratchet_(device)\n- Wikipedia: Pawl — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Pawl\n- Long Earth Society: Engine builds that use these parts (videos and write-ups) — web, video — LES site — https://longearthsociety.com/engineering/\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 4 parts): https://xemstudio.com/files/hardware/ratchet-and-pawl/index.json\nAPI: https://xemstudio.com/api/geometry?object=ratchet-and-pawl\n",
 "sources": [
  {
   "publisher": "Wikipedia",
   "title": "Ratchet (device)",
   "url": "https://en.wikipedia.org/wiki/Ratchet_(device)",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wikipedia",
   "title": "Pawl",
   "url": "https://en.wikipedia.org/wiki/Pawl",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Long Earth Society",
   "title": "Engine builds that use these parts (videos and write-ups)",
   "url": "https://longearthsociety.com/engineering/",
   "formats": [
    "web",
    "video"
   ],
   "license": "LES site",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "spur-gears-involute",
  "crank-conrod-flywheel-kit",
  "dowel-pins-metric",
  "ball-bearings-metric"
 ],
 "faq": [
  {
   "q": "How many teeth should a ratchet have?",
   "a": "Fewer teeth are stronger: 12 teeth (30° steps) for a hand-wound starter, 24–36 for fine positioning. Tooth depth 3 mm prints cleanly."
  },
  {
   "q": "Which way does the pawl point?",
   "a": "Its contact point trails the pivot in the locking direction so load drives it into the tooth; the back of the tooth lifts it on the free stroke."
  },
  {
   "q": "Can a printed ratchet hold an engine flywheel?",
   "a": "Yes at model scale: a 12-tooth PETG wheel with a 6 mm face holds several N·m; keep the pawl thick (6 mm) and pivot it on a 3 mm steel pin."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "ratchet-12t-d40",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/ratchet-and-pawl/ratchet-12t-d40.step",
   "stl": "https://xemstudio.com/files/hardware/ratchet-and-pawl/ratchet-12t-d40.stl",
   "note": "ratchet wheel Ø40 × 6, 12 teeth 3 mm deep, Ø5 bore"
  },
  {
   "file": "ratchet-24t-d40",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/ratchet-and-pawl/ratchet-24t-d40.step",
   "stl": "https://xemstudio.com/files/hardware/ratchet-and-pawl/ratchet-24t-d40.stl",
   "note": "ratchet wheel Ø40 × 6, 24 teeth 3 mm deep, Ø5 bore"
  },
  {
   "file": "ratchet-36t-d40",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/ratchet-and-pawl/ratchet-36t-d40.step",
   "stl": "https://xemstudio.com/files/hardware/ratchet-and-pawl/ratchet-36t-d40.stl",
   "note": "ratchet wheel Ø40 × 6, 36 teeth 3 mm deep, Ø5 bore"
  },
  {
   "file": "pawl-24",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/ratchet-and-pawl/pawl-24.step",
   "stl": "https://xemstudio.com/files/hardware/ratchet-and-pawl/pawl-24.stl",
   "note": "pawl 24 mm, Ø3.2 pivot, for the Ø40 wheels; spring not modeled"
  }
 ],
 "markdown": "https://xemstudio.com/objects/ratchet-and-pawl/index.md"
}