{
 "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": "gamma-crank-head",
 "name": "Gamma crank head for a 2 in tri-clamp spool: rod gland, crankshaft towers and power-cylinder seat in one part",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Tri-clamp engine parts",
 "year": null,
 "question": "What holds the crankshaft and power cylinder on a 2 inch tri-clamp gamma Stirling engine?",
 "tags": [
  "gamma",
  "crank head",
  "tri-clamp",
  "crankshaft",
  "power cylinder",
  "gland",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "gamma stirling crank head",
  "tri clamp stirling crankshaft mount",
  "gamma stirling power cylinder mount",
  "stirling displacer rod gland",
  "2 inch tri clamp gamma engine head"
 ],
 "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/gamma-crank-head/",
 "sheet_txt": "https://xemstudio.com/objects/gamma-crank-head/sheet.txt",
 "sheet": {
  "basis": "ISO 2852 cap face (the end-cap profile) on a pedestal clear of the two-bolt clamp; 625 bearing (5 × 16 × 5) pockets; Ø20 × 45 flanged liner seat (flange Ø44, 4 × M3 on Ø36); all positions from the gamma crank train worked out in tools/gamma_geom.py",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "One part closes the spool's cold end and carries the whole crank: the ISO 2852 face clamps to the spool like an end cap; a Ø50.8 pedestal rises clear of the clamp to a deck at 14–22 mm.",
   "Displacer rod: a Ø3 bore runs straight through the cap, pedestal, deck and a Ø10 boss to 40 mm, a 40 mm clearance-seal gland for the Ø3 rod (the running fit is listed under Mating features).",
   "Crankshaft: two towers (x 15.5–23.5 and 55.5–63.5) with Ø16 × 5 pockets for 625 bearings put a Ø5 × 80 shaft 127.5 mm above the face, along the deck. Tower A's pocket opens toward the rod axis, tower B's toward the power cylinder, so the crank discs and spacers on the two shaft ends hold the shaft between the bearings.",
   "Cranks are overhung: the displacer disc on the x = 3.5 end puts its con-rod on the rod axis, the power disc on the x = 83.5 end puts its con-rod on the power cylinder axis (x 87); the flywheel turns between the towers, Ø150 clear of the deck by 30.5 mm.",
   "Power cylinder: the Ø20 × 45 liner's flange sits on a Ø44 seat (top 47.8 mm) with four M3 tapped holes (Ø2.5) on R18; the seat is the cylinder head. A Ø4 passage runs from the cap face at x 15 up into the deck, along it at z 18, and up into the liner: the transfer port, with no tube.",
   "Exact dimensions: pockets, bores and holes are drawn at the bearing, rod and tap-drill sizes; their fits are under Mating features."
  ],
  "table": {
   "columns": [
    "feature",
    "size_mm",
    "position_mm"
   ],
   "rows": [
    [
     "ISO 2852 face",
     "2 in (Ø64 rim)",
     "z 0"
    ],
    [
     "pedestal",
     "Ø50.8",
     "z 4.5–14"
    ],
    [
     "deck",
     "141 × 54 × 8",
     "x -30..111"
    ],
    [
     "rod gland",
     "Ø3 × 40",
     "on the axis"
    ],
    [
     "625 pockets",
     "Ø16 × 5",
     "z 127.5; x 15.5–20.5 and 58.5–63.5"
    ],
    [
     "liner seat",
     "Ø44, 4 × M3 tapped on R18",
     "x 87, top z 47.8"
    ],
    [
     "transfer passage",
     "Ø4",
     "x 15 → 87 at z 18"
    ]
   ]
  }
 },
 "sheet_text": "Gamma crank head for a 2 in tri-clamp spool: rod gland, crankshaft towers and power-cylinder seat in one part — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/gamma-crank-head/  (CC BY 4.0)\nBasis: ISO 2852 cap face (the end-cap profile) on a pedestal clear of the two-bolt clamp; 625 bearing (5 × 16 × 5) pockets; Ø20 × 45 flanged liner seat (flange Ø44, 4 × M3 on Ø36); all positions from the gamma crank train worked out in tools/gamma_geom.py\nCatalog version: 2026-10-20\n\nSizes: see table below\n- One part closes the spool's cold end and carries the whole crank: the ISO 2852 face clamps to the spool like an end cap; a Ø50.8 pedestal rises clear of the clamp to a deck at 14–22 mm.\n- Displacer rod: a Ø3 bore runs straight through the cap, pedestal, deck and a Ø10 boss to 40 mm, a 40 mm clearance-seal gland for the Ø3 rod (the running fit is listed under Mating features).\n- Crankshaft: two towers (x 15.5–23.5 and 55.5–63.5) with Ø16 × 5 pockets for 625 bearings put a Ø5 × 80 shaft 127.5 mm above the face, along the deck. Tower A's pocket opens toward the rod axis, tower B's toward the power cylinder, so the crank discs and spacers on the two shaft ends hold the shaft between the bearings.\n- Cranks are overhung: the displacer disc on the x = 3.5 end puts its con-rod on the rod axis, the power disc on the x = 83.5 end puts its con-rod on the power cylinder axis (x 87); the flywheel turns between the towers, Ø150 clear of the deck by 30.5 mm.\n- Power cylinder: the Ø20 × 45 liner's flange sits on a Ø44 seat (top 47.8 mm) with four M3 tapped holes (Ø2.5) on R18; the seat is the cylinder head. A Ø4 passage runs from the cap face at x 15 up into the deck, along it at z 18, and up into the liner: the transfer port, with no tube.\n- Exact dimensions: pockets, bores and holes are drawn at the bearing, rod and tap-drill sizes; their fits are under Mating features.\n\nfeature  size_mm  position_mm\nISO 2852 face  2 in (Ø64 rim)  z 0\npedestal  Ø50.8  z 4.5–14\ndeck  141 × 54 × 8  x -30..111\nrod gland  Ø3 × 40  on the axis\n625 pockets  Ø16 × 5  z 127.5; x 15.5–20.5 and 58.5–63.5\nliner seat  Ø44, 4 × M3 tapped on R18  x 87, top z 47.8\ntransfer passage  Ø4  x 15 → 87 at z 18\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Wikipedia: Stirling engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Stirling_engine\n- ISO: ISO 2852 clamp pipe couplings (face profile) — standard — ISO [verify license at link] — https://www.iso.org/standard/7873.html\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/gamma-crank-head/index.json\nAPI: https://xemstudio.com/api/geometry?object=gamma-crank-head\n",
 "sources": [
  {
   "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": "ISO",
   "title": "ISO 2852 clamp pipe couplings (face profile)",
   "url": "https://www.iso.org/standard/7873.html",
   "formats": [
    "standard"
   ],
   "license": "ISO",
   "license_verified": false,
   "hosted": false
  },
  {
   "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-gamma-2in-tri-clamp",
  "tri-clamp-spool",
  "tri-clamp-clamps",
  "power-cylinder-liner",
  "counterweighted-crank-discs",
  "stirling-crankshafts",
  "ball-bearings-metric",
  "nut-pocket-flywheels"
 ],
 "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": "head face",
   "exact": "ISO 2852",
   "mates": "ferrule face + Type B gasket",
   "fit": "clamp",
   "files": "all"
  },
  {
   "feature": "rod gland",
   "exact": "Ø3 × 41",
   "mates": "Ø3 displacer rod (clearance seal)",
   "fit": "run",
   "files": "all"
  },
  {
   "feature": "tower bearing pockets",
   "exact": "Ø16 × 5",
   "mates": "625 bearing",
   "fit": "press",
   "files": "all"
  },
  {
   "feature": "tower shaft clearance",
   "exact": "Ø11.2",
   "mates": "Ø5 shaft (no contact)",
   "fit": "designed",
   "files": "all"
  },
  {
   "feature": "liner seat holes",
   "exact": "Ø2.5 × 8",
   "mates": "M3 tap drill (liner flange screws)",
   "fit": "designed",
   "files": "all"
  },
  {
   "feature": "transfer passage",
   "exact": "Ø4",
   "mates": "engine space to the liner (gas path)",
   "fit": "designed",
   "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": "How does the power cylinder connect to the displacer space on the tri-clamp gamma?",
   "a": "Through a Ø4 passage inside the crank head, from the cap face under the displacer to the liner seat; there is no transfer tube."
  },
  {
   "q": "What bearings does the gamma crank head take?",
   "a": "Two 625s (5 × 16 × 5) in Ø16 × 5 pockets, one per tower, on a Ø5 crankshaft."
  },
  {
   "q": "How high is the crankshaft on the 2 in gamma?",
   "a": "127.5 mm above the ISO 2852 face, far enough that the Ø3 × 100 displacer rod reaches its clevis and the Ø150 flywheel clears the deck."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "gamma-crank-head-2in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/gamma-crank-head/gamma-crank-head-2in.step",
   "stl": "https://xemstudio.com/files/hardware/gamma-crank-head/gamma-crank-head-2in.stl",
   "note": "2 in gamma crank head: ISO 2852 cap face, Ø50.8 pedestal to 14, deck 141 × 54 × 8, Ø3 rod gland through cap and a Ø10 boss to 40, two towers with 625 pockets for a Ø5 crankshaft 127.5 above the face, Ø44 liner seat at x 87 (top 47.8, 4 × M3 tapped on R18), Ø4 transfer passage from the cap face to the liner"
  }
 ],
 "markdown": "https://xemstudio.com/objects/gamma-crank-head/index.md"
}