{
 "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": "parallel-crank-coupling-mechanism",
 "name": "Parallel cranks and coupling rods, two pairs at 90° (no dead centre)",
 "kind": "hardware",
 "category": "Mechanisms",
 "group": "Linkages",
 "year": null,
 "question": "Why are coupling rods set 90° apart?",
 "tags": [
  "mechanism",
  "linkages",
  "kinematics",
  "507 mechanical movements"
 ],
 "aliases": [
  "coupling rods",
  "parallel crank coupling",
  "quartered cranks",
  "parallelogram linkage",
  "manivelas paralelas con bielas de acoplamiento",
  "Parallelkurbelkupplung (Kuppelstangen)"
 ],
 "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/parallel-crank-coupling-mechanism/",
 "sheet_txt": "https://xemstudio.com/objects/parallel-crank-coupling-mechanism/sheet.txt",
 "sheet": {
  "basis": "Xem Studio design following Brown No. 230 (1868)",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Two shafts 80 mm apart each carry two cranks of equal radius; equal rods join crank to crank, so the shafts turn together at exactly the same speed (a parallelogram linkage). One pair alone would jam or flip at its two dead centres (rod in line with the cranks); a second pair set at 90° is at full leverage exactly then, so the drive never stops — no flywheel needed.",
   "Catalog Ø36 crank discs (pin at 12 mm) and 80 mm links: the rod length equals the shaft distance, which makes every rod parallel to the line of shafts.",
   "Brown's No. 230 (circular into circular motion by two pairs of connecting rods at right angles); the quartered cranks of locomotive coupling rods.",
   "Parts (each has its own page): crank-disc-36-pin-r12, four-bar-links, dowel-pins-metric.",
   "Brown's movement No. 230 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size."
  ],
  "table": {
   "columns": [
    "parameter",
    "value"
   ],
   "rows": [
    [
     "shaft centres",
     "80 mm"
    ],
    [
     "crank radius",
     "12 mm"
    ],
    [
     "rods",
     "2 × 80 mm"
    ],
    [
     "crank phase",
     "90°"
    ],
    [
     "ratio",
     "1 : 1, same direction"
    ]
   ]
  }
 },
 "sheet_text": "Parallel cranks and coupling rods, two pairs at 90° (no dead centre) — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/parallel-crank-coupling-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)\nBasis: Xem Studio design following Brown No. 230 (1868)\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Two shafts 80 mm apart each carry two cranks of equal radius; equal rods join crank to crank, so the shafts turn together at exactly the same speed (a parallelogram linkage). One pair alone would jam or flip at its two dead centres (rod in line with the cranks); a second pair set at 90° is at full leverage exactly then, so the drive never stops — no flywheel needed.\n- Catalog Ø36 crank discs (pin at 12 mm) and 80 mm links: the rod length equals the shaft distance, which makes every rod parallel to the line of shafts.\n- Brown's No. 230 (circular into circular motion by two pairs of connecting rods at right angles); the quartered cranks of locomotive coupling rods.\n- Parts (each has its own page): crank-disc-36-pin-r12, four-bar-links, dowel-pins-metric.\n- Brown's movement No. 230 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.\n\nparameter  value\nshaft centres  80 mm\ncrank radius  12 mm\nrods  2 × 80 mm\ncrank phase  90°\nratio  1 : 1, same direction\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. 230: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_230.html\n\nFree files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/parallel-crank-coupling-mechanism/index.json\nAPI: https://xemstudio.com/api/geometry?object=parallel-crank-coupling-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. 230: figure, his text and an animation",
   "url": "https://507movements.com/mm_230.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": [
  "crank-disc-36-pin-r12",
  "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": "Why are coupling rods set 90° apart?",
   "a": "Two shafts 80 mm apart each carry two cranks of equal radius; equal rods join crank to crank, so the shafts turn together at exactly the same speed (a parallelogram linkage). One pair alone would jam or flip at its two dead centres (rod in line with the cranks); a second pair set at 90° is at full leverage exactly then, so the drive never stops — no flywheel needed."
  }
 ],
 "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": "parallel-crank-coupling-mechanism-assembly",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "Xem Studio Design License",
   "step": "https://xemstudio.com/files/hardware/parallel-crank-coupling-mechanism/parallel-crank-coupling-mechanism-assembly.step",
   "stl": "https://xemstudio.com/files/hardware/parallel-crank-coupling-mechanism/parallel-crank-coupling-mechanism-assembly.stl",
   "note": "Assembled mechanism, all parts placed at one pose (STEP keeps each part separate)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/parallel-crank-coupling-mechanism/index.md"
}