{
 "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": "weighted-belt-tightener-mechanism",
 "name": "Weighted belt tightener: pulley on a slide pulled by a hanging weight",
 "kind": "hardware",
 "category": "Mechanisms",
 "group": "Belt and friction drives",
 "year": null,
 "question": "How does a weighted tightener keep a belt tight?",
 "tags": [
  "mechanism",
  "belt and friction drives",
  "kinematics",
  "507 mechanical movements"
 ],
 "aliases": [
  "belt tensioner",
  "weighted tensioner",
  "gravity belt tensioner",
  "constant tension belt",
  "tensor de correa con contrapeso",
  "Riemenspanner mit Gewicht"
 ],
 "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/weighted-belt-tightener-mechanism/",
 "sheet_txt": "https://xemstudio.com/objects/weighted-belt-tightener-mechanism/sheet.txt",
 "sheet": {
  "basis": "Xem Studio design following Brown No. 23 (1868)",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "The driven pulley turns on a slide that runs on guide rods; a weight hung from the slide pulls it away from the driver, so the belt stays at the same tension however it stretches.",
   "Belt tension ≈ half the weight's pull per strand: a 394.58 g steel weight gives about 1.94 N in each strand. Here Ø80 driver over a Ø40 pulley 150 mm below, 16 × 1.5 belt of 491.17 mm.",
   "Brown's No. 23 (hanging, weighted tightener on a sliding frame).",
   "Parts (each has its own page): flanged-flat-pulley-40, flanged-flat-pulley-80, flat-belt-16x1-5-pulleys-40-80-c150, tightener-slide-8mm-stub, hanging-weight-d40x40-lug, linear-shafts-h6, dowel-pins-metric.",
   "Brown's movement No. 23 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size."
  ],
  "table": {
   "columns": [
    "parameter",
    "value"
   ],
   "rows": [
    [
     "pulleys",
     "Ø80 above Ø40, 150 mm"
    ],
    [
     "slide",
     "60 × 20 × 10 on 2 × Ø6 rods"
    ],
    [
     "weight",
     "Ø40 × 40 (394.58 g steel)"
    ],
    [
     "belt",
     "16 × 1.5, 491.17 mm"
    ]
   ]
  }
 },
 "sheet_text": "Weighted belt tightener: pulley on a slide pulled by a hanging weight — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/weighted-belt-tightener-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)\nBasis: Xem Studio design following Brown No. 23 (1868)\nCatalog version: 2026-10-20\n\nSizes: see table below\n- The driven pulley turns on a slide that runs on guide rods; a weight hung from the slide pulls it away from the driver, so the belt stays at the same tension however it stretches.\n- Belt tension ≈ half the weight's pull per strand: a 394.58 g steel weight gives about 1.94 N in each strand. Here Ø80 driver over a Ø40 pulley 150 mm below, 16 × 1.5 belt of 491.17 mm.\n- Brown's No. 23 (hanging, weighted tightener on a sliding frame).\n- Parts (each has its own page): flanged-flat-pulley-40, flanged-flat-pulley-80, flat-belt-16x1-5-pulleys-40-80-c150, tightener-slide-8mm-stub, hanging-weight-d40x40-lug, linear-shafts-h6, dowel-pins-metric.\n- Brown's movement No. 23 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.\n\nparameter  value\npulleys  Ø80 above Ø40, 150 mm\nslide  60 × 20 × 10 on 2 × Ø6 rods\nweight  Ø40 × 40 (394.58 g steel)\nbelt  16 × 1.5, 491.17 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. 23: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_023.html\n\nFree files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/weighted-belt-tightener-mechanism/index.json\nAPI: https://xemstudio.com/api/geometry?object=weighted-belt-tightener-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. 23: figure, his text and an animation",
   "url": "https://507movements.com/mm_023.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-16x1-5-pulleys-40-80-c150",
  "tightener-slide-8mm-stub",
  "hanging-weight-d40x40-lug",
  "linear-shafts-h6",
  "dowel-pins-metric"
 ],
 "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 does a weighted tightener keep a belt tight?",
   "a": "The driven pulley turns on a slide that runs on guide rods; a weight hung from the slide pulls it away from the driver, so the belt stays at the same tension however it stretches."
  }
 ],
 "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": "weighted-belt-tightener-mechanism-assembly",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "Xem Studio Design License",
   "step": "https://xemstudio.com/files/hardware/weighted-belt-tightener-mechanism/weighted-belt-tightener-mechanism-assembly.step",
   "stl": "https://xemstudio.com/files/hardware/weighted-belt-tightener-mechanism/weighted-belt-tightener-mechanism-assembly.stl",
   "note": "Assembled mechanism, all parts placed at one pose (STEP keeps each part separate)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/weighted-belt-tightener-mechanism/index.md"
}