{
 "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-closed-end-spool",
 "name": "Tri-clamp closed-end spool: 2 in × 152.4 mm (6 in) with a welded closed end, the hot end of a pressurised Stirling",
 "kind": "hardware",
 "category": "Hardware",
 "group": "Sanitary clamp fittings",
 "year": null,
 "question": "What is a closed-end tri-clamp spool and how do I order one for a Stirling hot end?",
 "tags": [
  "spool",
  "closed end",
  "hot end",
  "fabrication",
  "sanitary",
  "tri-clamp",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "closed end tri clamp spool",
  "tri clamp hot end",
  "2 inch closed end spool",
  "sanitary spool welded cap",
  "stirling hot end tri clamp"
 ],
 "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/tri-clamp-closed-end-spool/",
 "sheet_txt": "https://xemstudio.com/objects/tri-clamp-closed-end-spool/sheet.txt",
 "sheet": {
  "basis": "Fabrication spec: a standard 2 in ferrule (ISO 2852 face, as the ferrule on this site) on BPE 2 in tube Ø50.8 × 1.65, closed at the far end by a 3 mm welded end; plain outside (heat exchangers clamp on, see the fin sleeve)",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Drawing to send to a sanitary fabricator: '2 in × 152.4 mm closed-end spool, one 2 in clamp ferrule, tube Ø50.8 × 1.65, closed end 3 mm, 1.5 outside round'. The face is a standard 2 in clamp face; the rest is plain tube.",
   "On the free-piston generator it is the hot end: the burner fires at its closed end and lower half, and the only joint is at the top, at the regenerator's cold end, so no gasket is near the flame.",
   "Inside it are the displacer liner, the heater insert, the regenerator screens and the displacer's hot end. The bore is a slide fit for the liner's spokes and the inserts.",
   "At the generator's relief setting (15 bar gauge) the tube's hoop stress is 23.0 MPa; whether that is acceptable at the hot-end temperature depends on what the spool is made of, which is the builder's check."
  ],
  "table": {
   "columns": [
    "feature",
    "value"
   ],
   "rows": [
    [
     "face",
     "ISO 2852, 2 in (Ø64 flange, Ø56.5 groove, 1.6 recess)"
    ],
    [
     "tube",
     "Ø50.8 × 1.65 (bore Ø47.5)"
    ],
    [
     "face to outer end",
     152.4
    ],
    [
     "closed end",
     "3.0, 1.5 outer round"
    ]
   ]
  }
 },
 "sheet_text": "Tri-clamp closed-end spool: 2 in × 152.4 mm (6 in) with a welded closed end, the hot end of a pressurised Stirling — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/tri-clamp-closed-end-spool/  (CC BY 4.0)\nBasis: Fabrication spec: a standard 2 in ferrule (ISO 2852 face, as the ferrule on this site) on BPE 2 in tube Ø50.8 × 1.65, closed at the far end by a 3 mm welded end; plain outside (heat exchangers clamp on, see the fin sleeve)\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Drawing to send to a sanitary fabricator: '2 in × 152.4 mm closed-end spool, one 2 in clamp ferrule, tube Ø50.8 × 1.65, closed end 3 mm, 1.5 outside round'. The face is a standard 2 in clamp face; the rest is plain tube.\n- On the free-piston generator it is the hot end: the burner fires at its closed end and lower half, and the only joint is at the top, at the regenerator's cold end, so no gasket is near the flame.\n- Inside it are the displacer liner, the heater insert, the regenerator screens and the displacer's hot end. The bore is a slide fit for the liner's spokes and the inserts.\n- At the generator's relief setting (15 bar gauge) the tube's hoop stress is 23.0 MPa; whether that is acceptable at the hot-end temperature depends on what the spool is made of, which is the builder's check.\n\nfeature  value\nface  ISO 2852, 2 in (Ø64 flange, Ø56.5 groove, 1.6 recess)\ntube  Ø50.8 × 1.65 (bore Ø47.5)\nface to outer end  152.4\nclosed end  3.0, 1.5 outer round\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- ISO (via iTeh sample): ISO 2852 clamp liners: face profile and flange / groove diameters — PDF — standard excerpt; dimensions are facts — https://cdn.standards.iteh.ai/samples/7850/eb49c396488d408c8ced3e2961d76cf3/ISO-2852-1974.pdf\n- ASME: BPE Bioprocessing Equipment (tube OD and wall, clamp fittings) — standard — ASME; dimensions are facts [verify license at link] — https://www.asme.org/codes-standards/find-codes-standards/bpe-bioprocessing-equipment\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/tri-clamp-closed-end-spool/index.json\nAPI: https://xemstudio.com/api/geometry?object=tri-clamp-closed-end-spool\n",
 "sources": [
  {
   "publisher": "ISO (via iTeh sample)",
   "title": "ISO 2852 clamp liners: face profile and flange / groove diameters",
   "url": "https://cdn.standards.iteh.ai/samples/7850/eb49c396488d408c8ced3e2961d76cf3/ISO-2852-1974.pdf",
   "formats": [
    "PDF"
   ],
   "license": "standard excerpt; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "ASME",
   "title": "BPE Bioprocessing Equipment (tube OD and wall, clamp fittings)",
   "url": "https://www.asme.org/codes-standards/find-codes-standards/bpe-bioprocessing-equipment",
   "formats": [
    "standard"
   ],
   "license": "ASME; dimensions are facts",
   "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": [
  "tri-clamp-bored-spool",
  "tri-clamp-hot-end-fin-sleeve",
  "tri-clamp-split-burner-shroud",
  "fpse-displacer-cylinder",
  "list-fpse-generator-2in"
 ],
 "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": "face",
   "exact": "ISO 2852 2 in (land Ø56.5–Ø64, rim 2.85, 1.6 recess, 20° back)",
   "mates": "high-pressure clamp + half gaskets round the liner rim",
   "fit": "clamp",
   "files": "all"
  },
  {
   "feature": "bore",
   "exact": "Ø47.5 × 149.4 to the closed end",
   "mates": "liner spokes, heater insert OD, regenerator ring ODs",
   "fit": "slide",
   "files": "all"
  },
  {
   "feature": "tube OD",
   "exact": "Ø50.8 (z 2–68.5 and 76.5–82.5 from the closed end)",
   "mates": "fin sleeve halves, shroud lids",
   "fit": "clamp",
   "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": "Can I order this from a sanitary fabricator?",
   "a": "Yes: it is a standard 2 in ferrule on standard tube with a welded closed end; the drawing and the one-line spec above are what they need."
  },
  {
   "q": "Why not a cap and a gasket at the hot end?",
   "a": "A gasket in the flame is the first thing to fail on a pressurised engine; closing the tube in one piece puts the only joint at the cold end."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "closed-spool-2in-152.4",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-closed-end-spool/closed-spool-2in-152.4.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-closed-end-spool/closed-spool-2in-152.4.stl",
   "note": "2 in × 152.4 mm closed-end spool: ISO 2852 ferrule face at the open end, Ø50.8 × 1.65 tube, 3 mm welded closed end with a 1.5 outer round; bore Ø47.5 to the closed end (149.4 deep)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/tri-clamp-closed-end-spool/index.md"
}