{
 "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": "flywheel-crank",
 "name": "Flywheel crank: Ø100 nut-pocket flywheel with a 7.5 mm crank pin (15 mm stroke)",
 "kind": "hardware",
 "category": "Hardware",
 "group": "Stirling & thermoacoustic",
 "year": null,
 "question": "Can a Stirling engine's flywheel carry the crank pin?",
 "tags": [
  "flywheel",
  "crank",
  "ltd",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "flywheel crank pin",
  "flywheel with crank stirling"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 1,
 "url": "https://xemstudio.com/objects/flywheel-crank/",
 "sheet_txt": "https://xemstudio.com/objects/flywheel-crank/sheet.txt",
 "sheet": {
  "basis": "The Ø100 M8 nut-pocket flywheel (tools/gen_shafts_flywheels.py) with one added Ø3 pin hole through the hub at 7.5 from the axis",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Same wheel as flywheel-100-m8-b3 (12 M8 pockets at R40.5, Ø3 hub with M3 grub), plus a Ø3 hole through the hub at 7.5 from the axis, 90° from the grub, for a dowel-3x16 crank pin (10 in the hub, through a 5 mm con-rod, 1 proud). Overhung at a shaft end with the hub toward the con-rod: on the mug LTD it is the displacer crank (the web on the far side, so the displacer clevis passes under the rim); on the test-tube marble engine it drives the rocking link.",
   "Six M8 nuts in alternate pockets to start."
  ],
  "table": {
   "columns": [
    "feature",
    "value_mm"
   ],
   "rows": [
    [
     "diameter",
     100
    ],
    [
     "crank throw",
     7.5
    ],
    [
     "pin hole",
     "Ø3 through the 12.3 hub"
    ],
    [
     "bore",
     "Ø3"
    ]
   ]
  }
 },
 "sheet_text": "Flywheel crank: Ø100 nut-pocket flywheel with a 7.5 mm crank pin (15 mm stroke) — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/flywheel-crank/  (CC BY 4.0)\nBasis: The Ø100 M8 nut-pocket flywheel (tools/gen_shafts_flywheels.py) with one added Ø3 pin hole through the hub at 7.5 from the axis\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Same wheel as flywheel-100-m8-b3 (12 M8 pockets at R40.5, Ø3 hub with M3 grub), plus a Ø3 hole through the hub at 7.5 from the axis, 90° from the grub, for a dowel-3x16 crank pin (10 in the hub, through a 5 mm con-rod, 1 proud). Overhung at a shaft end with the hub toward the con-rod: on the mug LTD it is the displacer crank (the web on the far side, so the displacer clevis passes under the rim); on the test-tube marble engine it drives the rocking link.\n- Six M8 nuts in alternate pockets to start.\n\nfeature  value_mm\ndiameter  100\ncrank throw  7.5\npin hole  Ø3 through the 12.3 hub\nbore  Ø3\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Long Earth Society: Engine builds — web, video — LES site — https://longearthsociety.com/engineering/\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/flywheel-crank/index.json\nAPI: https://xemstudio.com/api/geometry?object=flywheel-crank\n",
 "sources": [
  {
   "publisher": "Long Earth Society",
   "title": "Engine builds",
   "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": [
  "list-ltd-mug",
  "ltd-bottom-plate",
  "ltd-top-plate",
  "glass-syringes",
  "nut-pocket-flywheels",
  "hex-nut-weights"
 ],
 "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": [
  {
   "feature": "hub bore",
   "exact": "Ø3",
   "mates": "Ø3 shaft (crankshaft or dowel-3x30)",
   "fit": "slide",
   "files": "all"
  },
  {
   "feature": "crank-pin hole",
   "exact": "Ø3, 7.5 from the axis",
   "mates": "dowel-3x16 crank pin",
   "fit": "press",
   "files": "all"
  },
  {
   "feature": "grub hole",
   "exact": "Ø2.5 (M3 tapped)",
   "mates": "set-m3x8",
   "fit": "designed",
   "files": "all"
  },
  {
   "feature": "nut pockets",
   "exact": "12 × M8 hex, one flat outward",
   "mates": "M8 hex nut (flywheel weight)",
   "fit": "press",
   "files": "all"
  }
 ],
 "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": "Why put the crank pin in the flywheel?",
   "a": "The mug LTD's two cylinders are only 35 mm apart; with both cranks overhung there is no room for a separate flywheel on the shaft, so the flywheel is the displacer crank."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "flywheel-crank-100-m8-b3-s15",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/flywheel-crank/flywheel-crank-100-m8-b3-s15.step",
   "stl": "https://xemstudio.com/files/hardware/flywheel-crank/flywheel-crank-100-m8-b3-s15.stl",
   "note": "Ø100 flywheel with 12 M8 nut pockets (the nut-pocket flywheel's geometry, Ø3 hub, M3 grub) and a Ø3 crank-pin hole through the hub 7.5 from the axis (15 mm stroke), 90° from the grub"
  }
 ],
 "markdown": "https://xemstudio.com/objects/flywheel-crank/index.md"
}