{
 "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": "drag-link-mechanism",
 "name": "Drag-link (double-crank) four-bar",
 "kind": "hardware",
 "category": "Mechanisms",
 "group": "Linkages",
 "year": null,
 "question": "What is a drag-link mechanism?",
 "tags": [
  "mechanism",
  "linkages",
  "kinematics"
 ],
 "aliases": [
  "drag link mechanism",
  "double crank mechanism",
  "grashof four bar"
 ],
 "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/drag-link-mechanism/",
 "sheet_txt": "https://xemstudio.com/objects/drag-link-mechanism/sheet.txt",
 "sheet": {
  "basis": "Xem Studio drawing; classic mechanism (Brown No. 231)",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "A four-bar whose shortest link is the fixed frame: both cranks turn fully round. Grashof: s + l ≤ p + q (20 + 50 ≤ 45 + 40).",
   "Input turns at constant speed, output at varying speed — the base of quick-return drives and some shaper and press mechanisms.",
   "Built from four-bar links of the lengths in the table.",
   "Parts (each has its own page): four-bar-links, pins-3mm. Brown's movement No. 231 shows it (1868)."
  ],
  "table": {
   "columns": [
    "parameter",
    "value"
   ],
   "rows": [
    [
     "frame (shortest) s",
     "20 mm"
    ],
    [
     "input crank",
     "40 mm"
    ],
    [
     "coupler",
     "50 mm"
    ],
    [
     "output crank",
     "45 mm"
    ]
   ]
  }
 },
 "sheet_text": "Drag-link (double-crank) four-bar — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/drag-link-mechanism/  (CC BY 4.0)\nBasis: Xem Studio drawing; classic mechanism (Brown No. 231)\nCatalog version: 2026-10-20\n\nSizes: see table below\n- A four-bar whose shortest link is the fixed frame: both cranks turn fully round. Grashof: s + l ≤ p + q (20 + 50 ≤ 45 + 40).\n- Input turns at constant speed, output at varying speed — the base of quick-return drives and some shaper and press mechanisms.\n- Built from four-bar links of the lengths in the table.\n- Parts (each has its own page): four-bar-links, pins-3mm. Brown's movement No. 231 shows it (1868).\n\nparameter  value\nframe (shortest) s  20 mm\ninput crank  40 mm\ncoupler  50 mm\noutput crank  45 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\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/drag-link-mechanism/index.json\nAPI: https://xemstudio.com/api/geometry?object=drag-link-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
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "four-bar-links",
  "pins-3mm"
 ],
 "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": "What is a drag-link mechanism?",
   "a": "A four-bar whose shortest link is the fixed frame: both cranks turn fully round. Grashof: s + l ≤ p + q (20 + 50 ≤ 45 + 40)."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "drag-link-mechanism-assembly",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/drag-link-mechanism/drag-link-mechanism-assembly.step",
   "stl": "https://xemstudio.com/files/hardware/drag-link-mechanism/drag-link-mechanism-assembly.stl",
   "note": "Assembled mechanism, all parts placed (STEP keeps each part separate)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/drag-link-mechanism/index.md"
}