{
 "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": "crank-conrod-flywheel-kit",
 "name": "Crank discs, connecting rods and flywheels for model engines",
 "kind": "hardware",
 "category": "Hardware",
 "group": "Stirling & thermoacoustic",
 "year": null,
 "question": "What stroke and flywheel size does a small Stirling engine need?",
 "tags": [
  "crank",
  "connecting rod",
  "flywheel",
  "engine",
  "mechanism",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "crank disc stl",
  "connecting rod 3d print",
  "flywheel stl",
  "stirling engine crank",
  "model engine flywheel",
  "crankshaft stroke"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 15,
 "url": "https://xemstudio.com/objects/crank-conrod-flywheel-kit/",
 "sheet_txt": "https://xemstudio.com/objects/crank-conrod-flywheel-kit/sheet.txt",
 "sheet": {
  "basis": "Parametric parts sized for 3 mm crank pins, 623 bearings (3 × 10 × 4) in the rod ends, and 5 / 8 mm shafts; proportions from the Long Earth Society tri-clamp engines",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Crank disc: pin hole at stroke/2 from the bore; 3 mm dowel pin pressed in (2.95 mm hole in metal, 3.2 mm printed then reamed). Set screw locks the disc to a 5 mm shaft.",
   "Con-rod: 10.2 mm pockets take a 623 bearing at each end so the rod runs on balls, not plastic; centres 30–80 mm. Rod length ≥ 2 × stroke keeps the piston side-load low.",
   "Flywheel: energy ∝ D⁴, so go wide and thin: Ø100 × 10 mm in PLA with a brass rim insert outruns Ø60 solid. Balance by drilling the heavy side after the first run.",
   "Long Earth Society: the 2 in tri-clamp engines use a 20 mm stroke, 50 mm rod and Ø100 flywheel on an 8 mm shaft in 608 bearings."
  ],
  "table": {
   "columns": [
    "part",
    "sizes",
    "shaft_or_pin",
    "bearing"
   ],
   "rows": [
    [
     "crank disc",
     "stroke 10, 15, 20, 25, 30",
     "Ø5 shaft, Ø3 pin",
     "—"
    ],
    [
     "con-rod",
     "centres 30, 40, 50, 60, 80",
     "Ø3 pins",
     "623 both ends"
    ],
    [
     "flywheel",
     "Ø50, 80, 100, 120, 150 × 10",
     "Ø5 (50) / Ø8",
     "608 on the shaft"
    ]
   ]
  }
 },
 "sheet_text": "Crank discs, connecting rods and flywheels for model engines — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/crank-conrod-flywheel-kit/  (CC BY 4.0)\nBasis: Parametric parts sized for 3 mm crank pins, 623 bearings (3 × 10 × 4) in the rod ends, and 5 / 8 mm shafts; proportions from the Long Earth Society tri-clamp engines\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Crank disc: pin hole at stroke/2 from the bore; 3 mm dowel pin pressed in (2.95 mm hole in metal, 3.2 mm printed then reamed). Set screw locks the disc to a 5 mm shaft.\n- Con-rod: 10.2 mm pockets take a 623 bearing at each end so the rod runs on balls, not plastic; centres 30–80 mm. Rod length ≥ 2 × stroke keeps the piston side-load low.\n- Flywheel: energy ∝ D⁴, so go wide and thin: Ø100 × 10 mm in PLA with a brass rim insert outruns Ø60 solid. Balance by drilling the heavy side after the first run.\n- Long Earth Society: the 2 in tri-clamp engines use a 20 mm stroke, 50 mm rod and Ø100 flywheel on an 8 mm shaft in 608 bearings.\n\npart  sizes  shaft_or_pin  bearing\ncrank disc  stroke 10, 15, 20, 25, 30  Ø5 shaft, Ø3 pin  —\ncon-rod  centres 30, 40, 50, 60, 80  Ø3 pins  623 both ends\nflywheel  Ø50, 80, 100, 120, 150 × 10  Ø5 (50) / Ø8  608 on the shaft\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Wikipedia: Crank (mechanism) — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Crank_(mechanism)\n- Wikipedia: Flywheel — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Flywheel\n- Wikipedia: Stirling engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Stirling_engine\n- Long Earth Society: Engine builds that use these parts (videos and write-ups) — web, video — LES site — https://longearthsociety.com/engineering/\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 15 parts): https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/index.json\nAPI: https://xemstudio.com/api/geometry?object=crank-conrod-flywheel-kit\n",
 "sources": [
  {
   "publisher": "Wikipedia",
   "title": "Crank (mechanism)",
   "url": "https://en.wikipedia.org/wiki/Crank_(mechanism)",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wikipedia",
   "title": "Flywheel",
   "url": "https://en.wikipedia.org/wiki/Flywheel",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wikipedia",
   "title": "Stirling engine",
   "url": "https://en.wikipedia.org/wiki/Stirling_engine",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Long Earth Society",
   "title": "Engine builds that use these parts (videos and write-ups)",
   "url": "https://longearthsociety.com/engineering/",
   "formats": [
    "web",
    "video"
   ],
   "license": "LES site",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "spur-gears-involute",
  "ball-bearings-metric",
  "608-bearing",
  "dowel-pins-metric",
  "tri-clamp-spool",
  "set-screws-metric"
 ],
 "faq": [
  {
   "q": "How big should a Stirling engine flywheel be?",
   "a": "For a 2 in (50 mm bore) displacer engine, Ø100 × 10 mm is a good start; energy stored goes with the fourth power of diameter, so diameter beats thickness."
  },
  {
   "q": "What bearings go in a model engine connecting rod?",
   "a": "623 (3 × 10 × 4) at each end on 3 mm pins; the rod pocket is 10.2 mm in a print."
  },
  {
   "q": "How do I set the stroke on a crank disc?",
   "a": "Stroke = 2 × pin offset. The discs here have the pin at 5, 7.5, 10, 12.5 and 15 mm for 10–30 mm strokes."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "crank-disc-stroke10",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/crank-disc-stroke10.step",
   "stl": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/crank-disc-stroke10.stl",
   "note": "crank disc for 10 mm stroke (pin at 5.0 mm), Ø5 bore, M3 set screw, Ø3 pin hole"
  },
  {
   "file": "crank-disc-stroke15",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/crank-disc-stroke15.step",
   "stl": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/crank-disc-stroke15.stl",
   "note": "crank disc for 15 mm stroke (pin at 7.5 mm), Ø5 bore, M3 set screw, Ø3 pin hole"
  },
  {
   "file": "crank-disc-stroke20",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/crank-disc-stroke20.step",
   "stl": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/crank-disc-stroke20.stl",
   "note": "crank disc for 20 mm stroke (pin at 10.0 mm), Ø5 bore, M3 set screw, Ø3 pin hole"
  },
  {
   "file": "crank-disc-stroke25",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/crank-disc-stroke25.step",
   "stl": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/crank-disc-stroke25.stl",
   "note": "crank disc for 25 mm stroke (pin at 12.5 mm), Ø5 bore, M3 set screw, Ø3 pin hole"
  },
  {
   "file": "crank-disc-stroke30",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/crank-disc-stroke30.step",
   "stl": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/crank-disc-stroke30.stl",
   "note": "crank disc for 30 mm stroke (pin at 15.0 mm), Ø5 bore, M3 set screw, Ø3 pin hole"
  },
  {
   "file": "conrod-30",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-30.step",
   "stl": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-30.stl",
   "note": "connecting rod, 30 mm centres, 10.2 mm pockets for 623 bearings both ends, 5 thick"
  },
  {
   "file": "conrod-40",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-40.step",
   "stl": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-40.stl",
   "note": "connecting rod, 40 mm centres, 10.2 mm pockets for 623 bearings both ends, 5 thick"
  },
  {
   "file": "conrod-50",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-50.step",
   "stl": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-50.stl",
   "note": "connecting rod, 50 mm centres, 10.2 mm pockets for 623 bearings both ends, 5 thick"
  },
  {
   "file": "conrod-60",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-60.step",
   "stl": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-60.stl",
   "note": "connecting rod, 60 mm centres, 10.2 mm pockets for 623 bearings both ends, 5 thick"
  },
  {
   "file": "conrod-80",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-80.step",
   "stl": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-80.stl",
   "note": "connecting rod, 80 mm centres, 10.2 mm pockets for 623 bearings both ends, 5 thick"
  },
  {
   "file": "flywheel-50",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/flywheel-50.step",
   "stl": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/flywheel-50.stl",
   "note": "spoked flywheel Ø50 × 10, Ø5 bore, M3 set screw"
  },
  {
   "file": "flywheel-80",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/flywheel-80.step",
   "stl": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/flywheel-80.stl",
   "note": "spoked flywheel Ø80 × 10, Ø8 bore, M3 set screw"
  },
  {
   "file": "flywheel-100",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/flywheel-100.step",
   "stl": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/flywheel-100.stl",
   "note": "spoked flywheel Ø100 × 10, Ø8 bore, M3 set screw"
  },
  {
   "file": "flywheel-120",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/flywheel-120.step",
   "stl": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/flywheel-120.stl",
   "note": "spoked flywheel Ø120 × 10, Ø8 bore, M3 set screw"
  },
  {
   "file": "flywheel-150",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/flywheel-150.step",
   "stl": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/flywheel-150.stl",
   "note": "spoked flywheel Ø150 × 10, Ø8 bore, M3 set screw"
  }
 ],
 "markdown": "https://xemstudio.com/objects/crank-conrod-flywheel-kit/index.md"
}