{
 "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": "internal-gear-and-pinion-mechanism",
 "name": "Internal gear and pinion, 60 : 20 (3 : 1, same direction)",
 "kind": "hardware",
 "category": "Mechanisms",
 "group": "Gears",
 "year": null,
 "question": "Why does an internal gear turn the same way as its pinion?",
 "tags": [
  "mechanism",
  "gears",
  "kinematics",
  "507 mechanical movements"
 ],
 "aliases": [
  "internal gear",
  "ring gear and pinion",
  "annulus and pinion",
  "engranaje interior y piñón",
  "Hohlrad und Ritzel"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": false,
 "free_files": 1,
 "url": "https://xemstudio.com/objects/internal-gear-and-pinion-mechanism/",
 "sheet_txt": "https://xemstudio.com/objects/internal-gear-and-pinion-mechanism/sheet.txt",
 "sheet": {
  "basis": "Xem Studio design following Brown No. 34 (1868)",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "A pinion meshing inside a ring gear: both turn the same way (an external pair reverses), the ratio is 60 : 20 = 3 : 1, and the centres are only m(N_ring − N_pinion)/2 = 20 mm apart — a compact reduction.",
   "More teeth are in contact than in an external pair of the same size (the concave ring wraps the pinion), so it carries more load, as Brown notes.",
   "Module 1, 20°; the ring's spaces are the exact involute tooth of a 60-tooth gear; no backlash drawn.",
   "Parts (each has its own page): internal-ring-gear-m1-60t, spur-gears-module-1.",
   "Brown's movement No. 34 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size."
  ],
  "table": {
   "columns": [
    "parameter",
    "value"
   ],
   "rows": [
    [
     "ring",
     "60 T internal, Ø80"
    ],
    [
     "pinion",
     "20 T"
    ],
    [
     "ratio",
     "3 : 1, same direction"
    ],
    [
     "centre distance",
     "20 mm"
    ]
   ]
  }
 },
 "sheet_text": "Internal gear and pinion, 60 : 20 (3 : 1, same direction) — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/internal-gear-and-pinion-mechanism/  (CC BY 4.0)\nBasis: Xem Studio design following Brown No. 34 (1868)\nCatalog version: 2026-10-20\n\nSizes: see table below\n- A pinion meshing inside a ring gear: both turn the same way (an external pair reverses), the ratio is 60 : 20 = 3 : 1, and the centres are only m(N_ring − N_pinion)/2 = 20 mm apart — a compact reduction.\n- More teeth are in contact than in an external pair of the same size (the concave ring wraps the pinion), so it carries more load, as Brown notes.\n- Module 1, 20°; the ring's spaces are the exact involute tooth of a 60-tooth gear; no backlash drawn.\n- Parts (each has its own page): internal-ring-gear-m1-60t, spur-gears-module-1.\n- Brown's movement No. 34 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.\n\nparameter  value\nring  60 T internal, Ø80\npinion  20 T\nratio  3 : 1, same direction\ncentre distance  20 mm\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Henry T. Brown (1868, public domain): Five Hundred and Seven Mechanical Movements — scan on archive.org — web — Publisher's page; dimensions are facts — https://archive.org/details/fivehundredseven00browiala\n- 507movements.com: Brown's movement No. 34: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_034.html\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/internal-gear-and-pinion-mechanism/index.json\nAPI: https://xemstudio.com/api/geometry?object=internal-gear-and-pinion-mechanism\n",
 "sources": [
  {
   "publisher": "Henry T. Brown (1868, public domain)",
   "title": "Five Hundred and Seven Mechanical Movements — scan on archive.org",
   "url": "https://archive.org/details/fivehundredseven00browiala",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "507movements.com",
   "title": "Brown's movement No. 34: figure, his text and an animation",
   "url": "https://507movements.com/mm_034.html",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "internal-ring-gear-m1-60t",
  "spur-gears-module-1"
 ],
 "fits": [],
 "dimensions": "exact (nominal, no printing tolerance)",
 "dimension_rule": "All geometry on Xem Studio is exact (nominal, true size) with no printing tolerance. Where a part meets another part, the object lists its mating features (feature, exact size, what it mates with, fit class: press, slide, run, socket, clamp or designed). Apply your process's allowance to those features only; 'designed' gaps are part of the design and stay as drawn.",
 "mating": [],
 "faq": [
  {
   "q": "Why does an internal gear turn the same way as its pinion?",
   "a": "A pinion meshing inside a ring gear: both turn the same way (an external pair reverses), the ratio is 60 : 20 = 3 : 1, and the centres are only m(N_ring − N_pinion)/2 = 20 mm apart — a compact reduction."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "internal-gear-and-pinion-mechanism-assembly",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/internal-gear-and-pinion-mechanism/internal-gear-and-pinion-mechanism-assembly.step",
   "stl": "https://xemstudio.com/files/hardware/internal-gear-and-pinion-mechanism/internal-gear-and-pinion-mechanism-assembly.stl",
   "note": "Assembled mechanism, all parts placed at one pose (STEP keeps each part separate)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/internal-gear-and-pinion-mechanism/index.md"
}