{
 "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": "spoked-flywheels",
 "name": "Spoked flywheels Ø50 to Ø150 × 10",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Drives & mechanisms",
 "year": null,
 "question": "What size flywheel does a small Stirling engine need?",
 "tags": [
  "flywheel",
  "spoked",
  "stirling",
  "inertia",
  "wheel",
  "long earth society"
 ],
 "aliases": [
  "flywheel stl",
  "model engine flywheel",
  "stirling flywheel 100mm",
  "spoked flywheel step"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 5,
 "url": "https://xemstudio.com/objects/spoked-flywheels/",
 "sheet_txt": "https://xemstudio.com/objects/spoked-flywheels/sheet.txt",
 "sheet": {
  "basis": "Rim Ø D × 10, five spokes 5 wide, Ø5 (Ø50) or Ø8 bore, radial M3 tapped hole",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "A Ø D × 10 wheel with five 5 mm spokes and a Ø5 (Ø50 wheel) or Ø8 (Ø80–150) bore; a radial Ø2.5 hole (M3 tap drill) at mid-thickness locks it to the shaft.",
   "Between the spokes the wheel is hollow inside: the band from 0.18 D radius to 8 mm inside the rim is a closed void with 1.5 mm faces on both sides.",
   "On the Ø80–Ø150 files the spoke ends stand proud of the rim; the overall size is in the table.",
   "Energy stored at a given speed goes with the fourth power of diameter, so diameter does more than thickness."
  ],
  "table": {
   "columns": [
    "file",
    "rim Ø",
    "thickness",
    "bore",
    "overall (spoke ends)"
   ],
   "rows": [
    [
     "flywheel-50",
     50,
     10,
     5,
     "50 × 50"
    ],
    [
     "flywheel-80",
     80,
     10,
     8,
     "83.6 × 84.5"
    ],
    [
     "flywheel-100",
     100,
     10,
     8,
     "106.0 × 108.1"
    ],
    [
     "flywheel-120",
     120,
     10,
     8,
     "128.4 × 131.7"
    ],
    [
     "flywheel-150",
     150,
     10,
     8,
     "162.0 × 167.0"
    ]
   ]
  }
 },
 "sheet_text": "Spoked flywheels Ø50 to Ø150 × 10 — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/spoked-flywheels/  (CC BY 4.0)\nBasis: Rim Ø D × 10, five spokes 5 wide, Ø5 (Ø50) or Ø8 bore, radial M3 tapped hole\nCatalog version: 2026-10-20\n\nSizes: see table below\n- A Ø D × 10 wheel with five 5 mm spokes and a Ø5 (Ø50 wheel) or Ø8 (Ø80–150) bore; a radial Ø2.5 hole (M3 tap drill) at mid-thickness locks it to the shaft.\n- Between the spokes the wheel is hollow inside: the band from 0.18 D radius to 8 mm inside the rim is a closed void with 1.5 mm faces on both sides.\n- On the Ø80–Ø150 files the spoke ends stand proud of the rim; the overall size is in the table.\n- Energy stored at a given speed goes with the fourth power of diameter, so diameter does more than thickness.\n\nfile  rim Ø  thickness  bore  overall (spoke ends)\nflywheel-50  50  10  5  50 × 50\nflywheel-80  80  10  8  83.6 × 84.5\nflywheel-100  100  10  8  106.0 × 108.1\nflywheel-120  120  10  8  128.4 × 131.7\nflywheel-150  150  10  8  162.0 × 167.0\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, 5 parts): https://xemstudio.com/files/hardware/spoked-flywheels/index.json\nAPI: https://xemstudio.com/api/geometry?object=spoked-flywheels\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": [
  "nut-pocket-flywheels",
  "shaft-adapter-5-to-8mm",
  "stirling-crankshafts",
  "bolt-on-counterweights"
 ],
 "fits": [
  {
   "role": "Goes in or on",
   "items": [
    {
     "slug": "stirling-crankshafts",
     "why": "Ø5 / Ø8 bore, M3 grub on the flat"
    }
   ]
  },
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "shaft-adapter-5-to-8mm",
     "why": "Ø8 bore on a Ø5 shaft"
    },
    {
     "slug": "bolt-on-counterweights",
     "why": "arc bolted opposite the crank pin"
    }
   ]
  },
  {
   "role": "Alternatives",
   "items": [
    {
     "slug": "nut-pocket-flywheels",
     "why": "rim pockets carry hex nuts"
    }
   ]
  }
 ],
 "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": [
  {
   "feature": "flywheel bore",
   "exact": "Ø5 / Ø8",
   "mates": "crankshaft (M3 set screw)",
   "fit": "slide",
   "files": "flywheel-"
  },
  {
   "feature": "flywheel set-screw hole",
   "exact": "Ø2.5",
   "mates": "M3 tap drill",
   "fit": "designed",
   "files": "flywheel-"
  }
 ],
 "fit_classes": {
  "press": "stays put: pin, tube, bearing or magnet held by interference. Typical FDM: hole +0.0 to +0.1 mm on diameter.",
  "slide": "assembles by hand and is held by a grub, pinch or clamp: shaft in a hub, rod in a socket, spigot in a bore. Typical FDM: +0.2 mm.",
  "run": "turns or slides in use: pin in a link, rod through a guide. Typical FDM: +0.3 mm.",
  "socket": "large sliding fit: syringe barrel, sleeve, bobbin in a bore. Typical FDM: +0.3 mm.",
  "clamp": "split part that closes on the mating part with screws: make it at size.",
  "designed": "a gap that is part of the design (piston fit option, displacer gap, air gap): do not change."
 },
 "faq": [
  {
   "q": "How big a flywheel for a 2 in tri-clamp engine?",
   "a": "The 2 in engines run Ø100 × 10 on an Ø8 shaft."
  },
  {
   "q": "What bore are the spoked flywheels?",
   "a": "Ø5 on the Ø50, Ø8 on the Ø80–150; the 5 → 8 shaft adapter puts an Ø8 wheel on a Ø5 shaft."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "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 overall: rim 8 wide (ID Ø34), hub Ø18, five spokes 5 wide × 7 thick on the mid-plane, open windows between; 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 overall: rim 8 wide (ID Ø64), hub Ø28.8, five spokes 5 wide × 7 thick on the mid-plane, open windows between; 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 overall: rim 8 wide (ID Ø84), hub Ø36, five spokes 5 wide × 7 thick on the mid-plane, open windows between; 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 overall: rim 8 wide (ID Ø104), hub Ø43.2, five spokes 5 wide × 7 thick on the mid-plane, open windows between; 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 overall: rim 8 wide (ID Ø134), hub Ø54, five spokes 5 wide × 7 thick on the mid-plane, open windows between; Ø8 bore, M3 set screw"
  }
 ],
 "markdown": "https://xemstudio.com/objects/spoked-flywheels/index.md"
}