{
 "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": "belt-and-pulleys-mechanism",
 "name": "Open flat belt and two pulleys (2 : 1)",
 "kind": "hardware",
 "category": "Mechanisms",
 "group": "Belt and friction drives",
 "year": null,
 "question": "How do you work out a belt drive's ratio and length?",
 "tags": [
  "mechanism",
  "belt and friction drives",
  "kinematics",
  "507 mechanical movements"
 ],
 "aliases": [
  "belt drive",
  "pulley and belt",
  "flat belt drive",
  "transmisión por correa y poleas",
  "Riementrieb"
 ],
 "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/belt-and-pulleys-mechanism/",
 "sheet_txt": "https://xemstudio.com/objects/belt-and-pulleys-mechanism/sheet.txt",
 "sheet": {
  "basis": "Xem Studio design following Brown No. 1 (1868)",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "An open belt on two pulleys turns both shafts the same way; speed ratio = D₂/D₁ = 80/40 = 2 : 1 (less a little slip). Belt inside length here 471.36 mm for 140 mm centres.",
   "Wrap on the small pulley = 2·acos((R₂ − R₁)/C) = 163.6°: the smaller the wrap, the less torque before slipping.",
   "Brown's No. 1 (belt and pulleys); a crossed belt (No. 2) reverses the driven shaft.",
   "Parts (each has its own page): flanged-flat-pulley-40, flanged-flat-pulley-80, flat-belt-1-5x16-pulleys-40-80-140.",
   "Brown's movement No. 1 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size."
  ],
  "table": {
   "columns": [
    "parameter",
    "value"
   ],
   "rows": [
    [
     "pulleys",
     "Ø40 and Ø80, flanged"
    ],
    [
     "centres",
     "140 mm"
    ],
    [
     "ratio",
     "2 : 1"
    ],
    [
     "belt",
     "16 × 1.5, 471.36 mm"
    ]
   ]
  }
 },
 "sheet_text": "Open flat belt and two pulleys (2 : 1) — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/belt-and-pulleys-mechanism/  (CC BY 4.0)\nBasis: Xem Studio design following Brown No. 1 (1868)\nCatalog version: 2026-10-20\n\nSizes: see table below\n- An open belt on two pulleys turns both shafts the same way; speed ratio = D₂/D₁ = 80/40 = 2 : 1 (less a little slip). Belt inside length here 471.36 mm for 140 mm centres.\n- Wrap on the small pulley = 2·acos((R₂ − R₁)/C) = 163.6°: the smaller the wrap, the less torque before slipping.\n- Brown's No. 1 (belt and pulleys); a crossed belt (No. 2) reverses the driven shaft.\n- Parts (each has its own page): flanged-flat-pulley-40, flanged-flat-pulley-80, flat-belt-1-5x16-pulleys-40-80-140.\n- Brown's movement No. 1 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.\n\nparameter  value\npulleys  Ø40 and Ø80, flanged\ncentres  140 mm\nratio  2 : 1\nbelt  16 × 1.5, 471.36 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. 1: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_001.html\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/belt-and-pulleys-mechanism/index.json\nAPI: https://xemstudio.com/api/geometry?object=belt-and-pulleys-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. 1: figure, his text and an animation",
   "url": "https://507movements.com/mm_001.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": [
  "flanged-flat-pulley-40",
  "flanged-flat-pulley-80",
  "flat-belt-1-5x16-pulleys-40-80-140"
 ],
 "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": "How do you work out a belt drive's ratio and length?",
   "a": "An open belt on two pulleys turns both shafts the same way; speed ratio = D₂/D₁ = 80/40 = 2 : 1 (less a little slip). Belt inside length here 471.36 mm for 140 mm centres."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "belt-and-pulleys-mechanism-assembly",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/belt-and-pulleys-mechanism/belt-and-pulleys-mechanism-assembly.step",
   "stl": "https://xemstudio.com/files/hardware/belt-and-pulleys-mechanism/belt-and-pulleys-mechanism-assembly.stl",
   "note": "Assembled mechanism, all parts placed at one pose (STEP keeps each part separate)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/belt-and-pulleys-mechanism/index.md"
}