{
 "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": "tri-clamp-crank-head",
 "name": "Tri-clamp crank head: ISO 2852 cap with Ø3 rod bore and two 623 towers, 1.5, 2 and 3 in",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Tri-clamp engine parts",
 "year": null,
 "question": "What tri-clamp head carries the displacer rod and a crankshaft on the cap itself?",
 "tags": [
  "tri-clamp",
  "end cap",
  "crank",
  "623",
  "stirling",
  "beta",
  "long earth society"
 ],
 "aliases": [
  "tri clamp crank head",
  "stirling cap with crankshaft",
  "tri clamp end cap bearing towers",
  "displacer rod seal tri clamp",
  "623 bearing tri clamp cap"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 3,
 "url": "https://xemstudio.com/objects/tri-clamp-crank-head/",
 "sheet_txt": "https://xemstudio.com/objects/tri-clamp-crank-head/sheet.txt",
 "sheet": {
  "basis": "ISO 2852 cap face; Ø3 run bore for the displacer rod; two 623 bearing pockets (Ø10) on a Ø3 crank axis 30 mm above the face",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "An ISO 2852 end cap that carries both the displacer rod and a small crankshaft, so the drive sits right on the cylinder.",
   "On centre: a Ø18 × 9 boss with a Ø3 bore straight through for the Ø3 displacer rod (run fit); the bore is the rod guide and the clearance seal.",
   "Two towers 10 × 14 × 28 mm stand on the back of the 6 mm cap, centred ±(C3/2 − 11) from the axis (±14.25 / ±21.0 / ±34.5 mm for 1.5 / 2 / 3 in), each with a Ø10 pocket for a 623 bearing; the Ø3 crankshaft axis is 30 mm above the face, 24 mm above the cap's back.",
   "The overall height is 34 mm; flange Ø50.5 / 64.0 / 91.0."
  ],
  "table": {
   "columns": [
    "size_in",
    "flange_od_mm",
    "rod_bore_mm",
    "tower_centres_mm",
    "bearing",
    "crank_axis_above_face_mm"
   ],
   "rows": [
    [
     "1.5",
     50.5,
     3,
     28.5,
     "623 (Ø10)",
     30
    ],
    [
     "2",
     64,
     3,
     42,
     "623 (Ø10)",
     30
    ],
    [
     "3",
     91,
     3,
     69,
     "623 (Ø10)",
     30
    ]
   ]
  }
 },
 "sheet_text": "Tri-clamp crank head: ISO 2852 cap with Ø3 rod bore and two 623 towers, 1.5, 2 and 3 in — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/tri-clamp-crank-head/  (CC BY 4.0)\nBasis: ISO 2852 cap face; Ø3 run bore for the displacer rod; two 623 bearing pockets (Ø10) on a Ø3 crank axis 30 mm above the face\nCatalog version: 2026-10-20\n\nSizes: see table below\n- An ISO 2852 end cap that carries both the displacer rod and a small crankshaft, so the drive sits right on the cylinder.\n- On centre: a Ø18 × 9 boss with a Ø3 bore straight through for the Ø3 displacer rod (run fit); the bore is the rod guide and the clearance seal.\n- Two towers 10 × 14 × 28 mm stand on the back of the 6 mm cap, centred ±(C3/2 − 11) from the axis (±14.25 / ±21.0 / ±34.5 mm for 1.5 / 2 / 3 in), each with a Ø10 pocket for a 623 bearing; the Ø3 crankshaft axis is 30 mm above the face, 24 mm above the cap's back.\n- The overall height is 34 mm; flange Ø50.5 / 64.0 / 91.0.\n\nsize_in  flange_od_mm  rod_bore_mm  tower_centres_mm  bearing  crank_axis_above_face_mm\n1.5  50.5  3  28.5  623 (Ø10)  30\n2  64.0  3  42.0  623 (Ø10)  30\n3  91.0  3  69.0  623 (Ø10)  30\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Long Earth Society: Tri-clamp Stirling engine builds — web, video — LES site — https://longearthsociety.com/engineering/\n- James R. Senft: An Introduction to Low Temperature Differential Stirling Engines (displacer and gap design) — book — Moriya Press [verify license at link] — https://www.stirlingengine.com/\n- Wikipedia: Stirling engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Stirling_engine\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 3 parts): https://xemstudio.com/files/hardware/tri-clamp-crank-head/index.json\nAPI: https://xemstudio.com/api/geometry?object=tri-clamp-crank-head\n",
 "sources": [
  {
   "publisher": "Long Earth Society",
   "title": "Tri-clamp Stirling engine builds",
   "url": "https://longearthsociety.com/engineering/",
   "formats": [
    "web",
    "video"
   ],
   "license": "LES site",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "James R. Senft",
   "title": "An Introduction to Low Temperature Differential Stirling Engines (displacer and gap design)",
   "url": "https://www.stirlingengine.com/",
   "formats": [
    "book"
   ],
   "license": "Moriya Press",
   "license_verified": false,
   "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
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "tri-clamp-displacer",
  "tri-clamp-regenerative-displacer",
  "ball-bearings-metric",
  "rod-clevises",
  "crank-discs-5mm-bore",
  "tri-clamp-clamps"
 ],
 "fits": [
  {
   "role": "Goes in or on",
   "items": [
    {
     "slug": "tri-clamp-spool",
     "why": "ISO 2852 face on the cold-end ferrule"
    }
   ]
  },
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "tri-clamp-displacer",
     "why": "Ø3 rod through the Ø3 bore"
    },
    {
     "slug": "ball-bearings-metric",
     "why": "623 (3 × 10 × 4) in each Ø10 pocket"
    },
    {
     "slug": "rod-clevises",
     "why": "Ø3-bore crank discs and rod clevis on the Ø3 shaft and rod"
    }
   ]
  },
  {
   "role": "Also needed",
   "items": [
    {
     "slug": "stirling-crankshafts",
     "why": "Ø3 crankshaft and Ø3 displacer rod"
    },
    {
     "slug": "tri-clamp-clamps",
     "why": "clamp and gasket on the face"
    }
   ]
  }
 ],
 "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": "bearing pockets",
   "exact": "Ø10",
   "mates": "623 bearing",
   "fit": "press",
   "files": "head-crank-"
  },
  {
   "feature": "head faces",
   "exact": "ISO 2852",
   "mates": "ferrule face + Type B gasket",
   "fit": "clamp",
   "files": "head-"
  },
  {
   "feature": "rod-gland bore",
   "exact": "Ø3 × 13.4 (through cap and Ø18 boss)",
   "mates": "Ø3 displacer rod",
   "fit": "run",
   "files": "head-crank-"
  }
 ],
 "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 do I seal the displacer rod through a tri-clamp cap?",
   "a": "With a clearance seal: the crank head has a Ø3 bore straight through its Ø18 × 9 boss, and the Ø3 rod runs in it with no O-ring."
  },
  {
   "q": "How high is the crankshaft on the crank head?",
   "a": "The Ø3 crank axis is 30 mm above the sealing face (24 mm above the cap's back), in two 623 bearings."
  },
  {
   "q": "How far apart are the crank-head towers?",
   "a": "28.5 mm centre to centre on 1.5 in, 42.0 on 2 in, 69.0 on 3 in."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "head-crank-1.5in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/head-crank-1.5in.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/head-crank-1.5in.stl",
   "note": "1.5 in ISO 2852 cap: clearance-seal rod gland (Ø3 bore straight through the cap and its Ø18 boss, 13.4 mm long, for the Ø3 rod; no O-ring) and two 623 bearing towers for a Ø3 crankshaft 24 mm above the cap"
  },
  {
   "file": "head-crank-2in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/head-crank-2in.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/head-crank-2in.stl",
   "note": "2 in ISO 2852 cap: clearance-seal rod gland (Ø3 bore straight through the cap and its Ø18 boss, 13.4 mm long, for the Ø3 rod; no O-ring) and two 623 bearing towers for a Ø3 crankshaft 24 mm above the cap"
  },
  {
   "file": "head-crank-3in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/head-crank-3in.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/head-crank-3in.stl",
   "note": "3 in ISO 2852 cap: clearance-seal rod gland (Ø3 bore straight through the cap and its Ø18 boss, 13.4 mm long, for the Ø3 rod; no O-ring) and two 623 bearing towers for a Ø3 crankshaft 24 mm above the cap"
  }
 ],
 "markdown": "https://xemstudio.com/objects/tri-clamp-crank-head/index.md"
}