{
 "version": "2026-10-20",
 "license": "Dimension sheets: CC BY 4.0. Standard and published-size files: CC BY 4.0. Xem Studio's own designs (files_license = Xem Studio Design License): free to use and sell things from, not to redistribute as files — https://xemstudio.com/license/. Other publishers' files: their own license, linked beside them.",
 "slug": "fast-and-loose-pulleys-two-speed-mechanism",
 "name": "Two speeds from two belts on fast and loose pulleys",
 "kind": "hardware",
 "category": "Mechanisms",
 "group": "Belt and friction drives",
 "year": null,
 "question": "How do fast and loose pulleys give two speeds?",
 "tags": [
  "mechanism",
  "belt and friction drives",
  "kinematics",
  "507 mechanical movements"
 ],
 "aliases": [
  "fast and loose pulleys",
  "two speed belt drive",
  "loose pulley",
  "belt shifter",
  "poleas fija y loca (dos velocidades)",
  "Fest- und Losscheibe (zwei Gänge)"
 ],
 "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/fast-and-loose-pulleys-two-speed-mechanism/",
 "sheet_txt": "https://xemstudio.com/objects/fast-and-loose-pulleys-two-speed-mechanism/sheet.txt",
 "sheet": {
  "basis": "Xem Studio design following Brown No. 60 (1868)",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "The upper shaft carries a wide Ø80 and a wide Ø40 pulley; each drives its own belt. Below, each belt can run on a fast pulley (keyed to the shaft) or on a loose one beside it (free to turn). With belt 1 on its fast Ø40 the lower shaft runs at 2 × upper speed; shift belt 1 to its loose pulley and belt 2 onto its fast Ø80 and it runs at 0.5 ×.",
   "Drawn in the fast (2 : 1) setting: belt 1 on the fast Ø40, belt 2 idling on the loose Ø80. Both belts are the same length, 471.36 mm (Ø40 + Ø80 at 140 mm). Pulleys plain (no flanges) so the belts can be shifted; upper faces 34 mm wide for both positions.",
   "Brown's No. 60. Only one belt may be on a fast pulley at a time.",
   "Parts (each has its own page): plain-flat-pulley-80x34, plain-flat-pulley-40x34, plain-flat-pulley-40x16, plain-flat-pulley-80x16, flat-belt-16x1-5-pulleys-40-80-c140-open, linear-shafts-h6.",
   "Brown's movement No. 60 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size."
  ],
  "table": {
   "columns": [
    "parameter",
    "value"
   ],
   "rows": [
    [
     "upper pulleys",
     "Ø80 × 34 and Ø40 × 34 (fast)"
    ],
    [
     "lower pulleys",
     "Ø40 fast + loose, Ø80 loose + fast, × 16"
    ],
    [
     "speeds",
     "2 : 1 and 1 : 2"
    ],
    [
     "belts",
     "2 × 16 × 1.5, 471.36 mm"
    ],
    [
     "shafts",
     "Ø8, 140 mm apart"
    ]
   ]
  }
 },
 "sheet_text": "Two speeds from two belts on fast and loose pulleys — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/fast-and-loose-pulleys-two-speed-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)\nBasis: Xem Studio design following Brown No. 60 (1868)\nCatalog version: 2026-10-20\n\nSizes: see table below\n- The upper shaft carries a wide Ø80 and a wide Ø40 pulley; each drives its own belt. Below, each belt can run on a fast pulley (keyed to the shaft) or on a loose one beside it (free to turn). With belt 1 on its fast Ø40 the lower shaft runs at 2 × upper speed; shift belt 1 to its loose pulley and belt 2 onto its fast Ø80 and it runs at 0.5 ×.\n- Drawn in the fast (2 : 1) setting: belt 1 on the fast Ø40, belt 2 idling on the loose Ø80. Both belts are the same length, 471.36 mm (Ø40 + Ø80 at 140 mm). Pulleys plain (no flanges) so the belts can be shifted; upper faces 34 mm wide for both positions.\n- Brown's No. 60. Only one belt may be on a fast pulley at a time.\n- Parts (each has its own page): plain-flat-pulley-80x34, plain-flat-pulley-40x34, plain-flat-pulley-40x16, plain-flat-pulley-80x16, flat-belt-16x1-5-pulleys-40-80-c140-open, linear-shafts-h6.\n- Brown's movement No. 60 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.\n\nparameter  value\nupper pulleys  Ø80 × 34 and Ø40 × 34 (fast)\nlower pulleys  Ø40 fast + loose, Ø80 loose + fast, × 16\nspeeds  2 : 1 and 1 : 2\nbelts  2 × 16 × 1.5, 471.36 mm\nshafts  Ø8, 140 mm apart\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. 60: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_060.html\n\nFree files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/fast-and-loose-pulleys-two-speed-mechanism/index.json\nAPI: https://xemstudio.com/api/geometry?object=fast-and-loose-pulleys-two-speed-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. 60: figure, his text and an animation",
   "url": "https://507movements.com/mm_060.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": [
  "plain-flat-pulley-80x34",
  "plain-flat-pulley-40x34",
  "plain-flat-pulley-40x16",
  "plain-flat-pulley-80x16",
  "flat-belt-16x1-5-pulleys-40-80-c140-open",
  "linear-shafts-h6"
 ],
 "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 fast and loose pulleys give two speeds?",
   "a": "The upper shaft carries a wide Ø80 and a wide Ø40 pulley; each drives its own belt. Below, each belt can run on a fast pulley (keyed to the shaft) or on a loose one beside it (free to turn). With belt 1 on its fast Ø40 the lower shaft runs at 2 × upper speed; shift belt 1 to its loose pulley and belt 2 onto its fast Ø80 and it runs at 0.5 ×."
  }
 ],
 "files_license": {
  "name": "Xem Studio Design License",
  "holder": "Xem Studio",
  "url": "https://xemstudio.com/license/",
  "note": "Xem Studio's own design: free to use, print, modify and sell things made from it; not to be republished or redistributed as files."
 },
 "offers": [
  {
   "file": "fast-and-loose-pulleys-two-speed-mechanism-assembly",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "Xem Studio Design License",
   "step": "https://xemstudio.com/files/hardware/fast-and-loose-pulleys-two-speed-mechanism/fast-and-loose-pulleys-two-speed-mechanism-assembly.step",
   "stl": "https://xemstudio.com/files/hardware/fast-and-loose-pulleys-two-speed-mechanism/fast-and-loose-pulleys-two-speed-mechanism-assembly.stl",
   "note": "Assembled mechanism, all parts placed at one pose (STEP keeps each part separate)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/fast-and-loose-pulleys-two-speed-mechanism/index.md"
}