{
 "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-frame",
 "name": "Tri-clamp crank frame: ISO 2852 cap with 608 towers for a Ø8 crankshaft, 1.5, 2 and 3 in",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Tri-clamp engine parts",
 "year": null,
 "question": "How do I mount a crankshaft on a tri-clamp spool?",
 "tags": [
  "crank frame",
  "tri-clamp",
  "608",
  "crankshaft",
  "stirling",
  "alpha",
  "beta",
  "long earth society"
 ],
 "aliases": [
  "tri clamp stirling crankshaft frame",
  "crank frame tri clamp",
  "608 crank mount stirling",
  "tri clamp cap with bearing towers"
 ],
 "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-frame/",
 "sheet_txt": "https://xemstudio.com/objects/tri-clamp-crank-frame/sheet.txt",
 "sheet": {
  "basis": "ISO 2852 cap face; pedestal Ø = tube OD to clear the clamp; two 8 mm towers with Ø22 608 pockets, 21 mm apart, crank axis 32 / 34 / 40 mm above the face",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "A crank frame that clamps onto the open ferrule of a spool with a stock clamp and gasket, and holds a Ø8 crankshaft in two 608 bearings above it.",
   "Base: the 6 mm ISO 2852 cap, a pedestal the tube's OD (38.1 / 50.8 / 76.2) up to 14 mm so the clamp clears, and a Ø C3 plate 4 mm thick on top. A con-rod window Ø21 / Ø28 / Ø44 runs through the centre.",
   "Two towers 8 mm thick with rounded tops stand 21 mm apart; each has a Ø22 × 7 pocket for a 608 from the outside face, and the shaft hole between is Ø9.2 so the Ø8 shaft touches only the bearings.",
   "Crank axis 32 / 34 / 40 mm above the face for 1.5 / 2 / 3 in; overall height 47.7 / 54 / 60 mm."
  ],
  "table": {
   "columns": [
    "spool_in",
    "flange_od_mm",
    "window_mm",
    "crank_axis_mm",
    "tower_gap_mm",
    "bearing",
    "overall_h_mm"
   ],
   "rows": [
    [
     "1.5",
     50.5,
     21,
     32,
     21,
     "608 (Ø22)",
     47.7
    ],
    [
     "2",
     64,
     28,
     34,
     21,
     "608 (Ø22)",
     54
    ],
    [
     "3",
     91,
     44,
     40,
     21,
     "608 (Ø22)",
     60
    ]
   ]
  }
 },
 "sheet_text": "Tri-clamp crank frame: ISO 2852 cap with 608 towers for a Ø8 crankshaft, 1.5, 2 and 3 in — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/tri-clamp-crank-frame/  (CC BY 4.0)\nBasis: ISO 2852 cap face; pedestal Ø = tube OD to clear the clamp; two 8 mm towers with Ø22 608 pockets, 21 mm apart, crank axis 32 / 34 / 40 mm above the face\nCatalog version: 2026-10-20\n\nSizes: see table below\n- A crank frame that clamps onto the open ferrule of a spool with a stock clamp and gasket, and holds a Ø8 crankshaft in two 608 bearings above it.\n- Base: the 6 mm ISO 2852 cap, a pedestal the tube's OD (38.1 / 50.8 / 76.2) up to 14 mm so the clamp clears, and a Ø C3 plate 4 mm thick on top. A con-rod window Ø21 / Ø28 / Ø44 runs through the centre.\n- Two towers 8 mm thick with rounded tops stand 21 mm apart; each has a Ø22 × 7 pocket for a 608 from the outside face, and the shaft hole between is Ø9.2 so the Ø8 shaft touches only the bearings.\n- Crank axis 32 / 34 / 40 mm above the face for 1.5 / 2 / 3 in; overall height 47.7 / 54 / 60 mm.\n\nspool_in  flange_od_mm  window_mm  crank_axis_mm  tower_gap_mm  bearing  overall_h_mm\n1.5  50.5  21  32  21  608 (Ø22)  47.7\n2  64.0  28  34  21  608 (Ø22)  54.0\n3  91.0  44  40  21  608 (Ø22)  60.0\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 Stirling Engines (piston fit and leakage) — book — Moriya Press [verify license at link] — https://www.stirlingengine.com/\n- ASME: BPE tube dimensions (16 ga sanitary tube) — standard — ASME [verify license at link] — https://www.asme.org/codes-standards/find-codes-standards/bpe-bioprocessing-equipment\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 3 parts): https://xemstudio.com/files/hardware/tri-clamp-crank-frame/index.json\nAPI: https://xemstudio.com/api/geometry?object=tri-clamp-crank-frame\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 Stirling Engines (piston fit and leakage)",
   "url": "https://www.stirlingengine.com/",
   "formats": [
    "book"
   ],
   "license": "Moriya Press",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "ASME",
   "title": "BPE tube dimensions (16 ga sanitary tube)",
   "url": "https://www.asme.org/codes-standards/find-codes-standards/bpe-bioprocessing-equipment",
   "formats": [
    "standard"
   ],
   "license": "ASME",
   "license_verified": false,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "tri-clamp-crank-web",
  "tri-clamp-con-rod",
  "tri-clamp-power-piston",
  "608-bearing",
  "metric-shafts",
  "tri-clamp-clamps"
 ],
 "fits": [
  {
   "role": "Goes in or on",
   "items": [
    {
     "slug": "tri-clamp-spool",
     "why": "ISO 2852 face on the open ferrule"
    }
   ]
  },
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "608-bearing",
     "why": "608 in each Ø22 × 7 pocket"
    },
    {
     "slug": "tri-clamp-crank-web",
     "why": "two webs on the Ø8 shaft between the towers"
    }
   ]
  },
  {
   "role": "Also needed",
   "items": [
    {
     "slug": "metric-shafts",
     "why": "Ø8 shaft and collar"
    },
    {
     "slug": "tri-clamp-clamps",
     "why": "clamp and gasket on the face"
    },
    {
     "slug": "nut-pocket-flywheels",
     "why": "Ø8-hub flywheel outside a tower"
    }
   ]
  }
 ],
 "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": "crank-frame bearing pockets",
   "exact": "Ø22",
   "mates": "608 bearing",
   "fit": "press",
   "files": "crank-frame-"
  },
  {
   "feature": "crank-frame face",
   "exact": "ISO 2852",
   "mates": "tri-clamp ferrule face + Type B gasket",
   "fit": "clamp",
   "files": "crank-frame-"
  },
  {
   "feature": "crank-frame shaft clearance",
   "exact": "Ø9.2",
   "mates": "Ø8 shaft (no contact; the 608s carry it)",
   "fit": "designed",
   "files": "crank-frame-"
  }
 ],
 "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 put a crankshaft on a tri-clamp cylinder?",
   "a": "Clamp the crank frame to the open ferrule; a Ø8 shaft runs in two 608s in its towers, 34 mm above the face on the 2 in frame."
  },
  {
   "q": "How wide is the gap between the crank-frame towers?",
   "a": "21 mm: crank web, con-rod, crank web (5 mm each) with 1 mm gaps."
  },
  {
   "q": "Does the shaft touch the frame?",
   "a": "No: the shaft hole is Ø9.2; the Ø8 shaft runs only in the 608s."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "crank-frame-1.5in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-power-pistons/crank-frame-1.5in.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-power-pistons/crank-frame-1.5in.stl",
   "note": "1.5 in crank frame: ISO 2852 cap face (clamps to the spool with a stock clamp), Ø21 con-rod window, two towers with 608 pockets for a Ø8 crankshaft 32 mm above the face, 21 mm between towers"
  },
  {
   "file": "crank-frame-2in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-power-pistons/crank-frame-2in.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-power-pistons/crank-frame-2in.stl",
   "note": "2 in crank frame: ISO 2852 cap face (clamps to the spool with a stock clamp), Ø28 con-rod window, two towers with 608 pockets for a Ø8 crankshaft 34 mm above the face, 21 mm between towers"
  },
  {
   "file": "crank-frame-3in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-power-pistons/crank-frame-3in.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-power-pistons/crank-frame-3in.stl",
   "note": "3 in crank frame: ISO 2852 cap face (clamps to the spool with a stock clamp), Ø44 con-rod window, two towers with 608 pockets for a Ø8 crankshaft 40 mm above the face, 21 mm between towers"
  }
 ],
 "markdown": "https://xemstudio.com/objects/tri-clamp-crank-frame/index.md"
}