{
 "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": "treadle-crank-mechanism",
 "name": "Treadle and crank (crank-rocker four-bar)",
 "kind": "hardware",
 "category": "Mechanisms",
 "group": "Linkages",
 "year": null,
 "question": "How does a treadle turn a wheel?",
 "tags": [
  "mechanism",
  "linkages",
  "kinematics",
  "507 mechanical movements"
 ],
 "aliases": [
  "treadle crank",
  "crank rocker",
  "foot treadle mechanism",
  "four bar crank rocker",
  "pedal y manivela (manivela-balancín)",
  "Tretkurbel (Kurbelschwinge)"
 ],
 "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/treadle-crank-mechanism/",
 "sheet_txt": "https://xemstudio.com/objects/treadle-crank-mechanism/sheet.txt",
 "sheet": {
  "basis": "Xem Studio design following Brown No. 158 (1868)",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "A foot treadle rocking on a pivot drives a crank round through a connecting rod: a crank-rocker four-bar. Because the crank is the shortest link and next to the frame (Grashof: s + l ≤ p + q), it turns fully while the treadle only rocks.",
   "Here crank 20, rod 80, treadle 100 and frame 100 mm (catalog four-bar links): the treadle swings 25.08° per crank turn; a flywheel carries the crank through the two dead points where rod and crank line up.",
   "Brown's No. 158 (treadle driving a disc or crank), the drive of foot lathes, grinders and sewing machines.",
   "Parts (each has its own page): four-bar-links, dowel-pins-metric.",
   "Brown's movement No. 158 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size."
  ],
  "table": {
   "columns": [
    "parameter",
    "value"
   ],
   "rows": [
    [
     "crank",
     "20 mm"
    ],
    [
     "connecting rod",
     "80 mm"
    ],
    [
     "treadle",
     "100 mm"
    ],
    [
     "frame",
     "100 mm"
    ],
    [
     "treadle swing",
     "25.08°"
    ]
   ]
  }
 },
 "sheet_text": "Treadle and crank (crank-rocker four-bar) — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/treadle-crank-mechanism/  (CC BY 4.0)\nBasis: Xem Studio design following Brown No. 158 (1868)\nCatalog version: 2026-10-20\n\nSizes: see table below\n- A foot treadle rocking on a pivot drives a crank round through a connecting rod: a crank-rocker four-bar. Because the crank is the shortest link and next to the frame (Grashof: s + l ≤ p + q), it turns fully while the treadle only rocks.\n- Here crank 20, rod 80, treadle 100 and frame 100 mm (catalog four-bar links): the treadle swings 25.08° per crank turn; a flywheel carries the crank through the two dead points where rod and crank line up.\n- Brown's No. 158 (treadle driving a disc or crank), the drive of foot lathes, grinders and sewing machines.\n- Parts (each has its own page): four-bar-links, dowel-pins-metric.\n- Brown's movement No. 158 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.\n\nparameter  value\ncrank  20 mm\nconnecting rod  80 mm\ntreadle  100 mm\nframe  100 mm\ntreadle swing  25.08°\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. 158: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_158.html\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/treadle-crank-mechanism/index.json\nAPI: https://xemstudio.com/api/geometry?object=treadle-crank-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. 158: figure, his text and an animation",
   "url": "https://507movements.com/mm_158.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": [
  "four-bar-links",
  "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 treadle turn a wheel?",
   "a": "A foot treadle rocking on a pivot drives a crank round through a connecting rod: a crank-rocker four-bar. Because the crank is the shortest link and next to the frame (Grashof: s + l ≤ p + q), it turns fully while the treadle only rocks."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "treadle-crank-mechanism-assembly",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/treadle-crank-mechanism/treadle-crank-mechanism-assembly.step",
   "stl": "https://xemstudio.com/files/hardware/treadle-crank-mechanism/treadle-crank-mechanism-assembly.stl",
   "note": "Assembled mechanism, all parts placed at one pose (STEP keeps each part separate)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/treadle-crank-mechanism/index.md"
}