{
 "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-cups",
 "name": "Tri-clamp cups: closed-end spools (ferrule on a capped tube), 1.5, 2 and 3 in",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Tri-clamp engine parts",
 "year": null,
 "question": "What are the dimensions of a 2 inch tri-clamp spool with one end welded shut?",
 "tags": [
  "tri-clamp",
  "spool",
  "cup",
  "capped spool",
  "stirling",
  "long earth society",
  "cylinder"
 ],
 "aliases": [
  "tri clamp spool with one end closed",
  "capped tri clamp tube",
  "tri clamp cup",
  "sanitary tube welded cap",
  "tri clamp cylinder closed end",
  "closed end spool stl"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 13,
 "url": "https://xemstudio.com/objects/tri-clamp-cups/",
 "sheet_txt": "https://xemstudio.com/objects/tri-clamp-cups/sheet.txt",
 "sheet": {
  "basis": "ISO 2852 ferrule face (C2/C3, 2.85 mm rim, 1.6 mm recess, 20° back) and 16 ga ASME BPE tube from the tri-clamp ferrule entry; 3 mm flat end plate standing in for a welded cap",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "A cup is a spool with one ferrule and the other end closed: in stainless it is a tube with a cap welded on (or a 'tri-clamp end cap spool', sold as such); here it is one printed part. The ferrule end takes a stock clamp and gasket against any head on this shelf.",
   "What it is for: the hot end of a beta or gamma engine (the cup is the displacer cylinder, the open ferrule end gets the cold head with the rod guide), an alpha cylinder with the piston in it and the head carrying the con-rod gland, a cold-side water jacket cap, or a mock-up to check lengths before buying steel.",
   "Printed cups are cold-side and mock-up parts: PETG is good to ~70 °C. For a burner-fired hot end buy a stainless capped spool and use the printed one to set the length. Inner diameter matches the steel (34.8 / 47.5 / 72.9), so the displacers and pistons on this shelf fit both.",
   "Print closed end down, 0.2 mm layers, 3+ walls; the ferrule's 20° back cone needs no supports. Sand the face flat on a sheet of 400 grit on glass so the gasket seals.",
   "Lengths: 1.5 in 50/75/100, 2 in 60/90/120/150, 3 in 80/120/160; the -rod3 version has a Ø3.2 centre hole in the end for a displacer rod gland on the closed end (beta engines with the drive on the hot side are rare; it is there for a cold-end cup)."
  ],
  "table": {
   "columns": [
    "size",
    "od_mm",
    "id_mm",
    "length_mm",
    "end_plate_mm",
    "end"
   ],
   "rows": [
    [
     "1.5",
     38.1,
     34.8,
     50,
     3,
     "plain"
    ],
    [
     "1.5",
     38.1,
     34.8,
     75,
     3,
     "plain"
    ],
    [
     "1.5",
     38.1,
     34.8,
     100,
     3,
     "plain"
    ],
    [
     "1.5",
     38.1,
     34.8,
     75,
     3,
     "Ø3.2 centre hole"
    ],
    [
     "2",
     50.8,
     47.5,
     60,
     3,
     "plain"
    ],
    [
     "2",
     50.8,
     47.5,
     90,
     3,
     "plain"
    ],
    [
     "2",
     50.8,
     47.5,
     120,
     3,
     "plain"
    ],
    [
     "2",
     50.8,
     47.5,
     150,
     3,
     "plain"
    ],
    [
     "2",
     50.8,
     47.5,
     90,
     3,
     "Ø3.2 centre hole"
    ],
    [
     "3",
     76.2,
     72.9,
     80,
     3,
     "plain"
    ],
    [
     "3",
     76.2,
     72.9,
     120,
     3,
     "plain"
    ],
    [
     "3",
     76.2,
     72.9,
     160,
     3,
     "plain"
    ],
    [
     "3",
     76.2,
     72.9,
     120,
     3,
     "Ø3.2 centre hole"
    ]
   ]
  }
 },
 "sheet_text": "Tri-clamp cups: closed-end spools (ferrule on a capped tube), 1.5, 2 and 3 in — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/tri-clamp-cups/  (CC BY 4.0)\nBasis: ISO 2852 ferrule face (C2/C3, 2.85 mm rim, 1.6 mm recess, 20° back) and 16 ga ASME BPE tube from the tri-clamp ferrule entry; 3 mm flat end plate standing in for a welded cap\nCatalog version: 2026-10-20\n\nSizes: see table below\n- A cup is a spool with one ferrule and the other end closed: in stainless it is a tube with a cap welded on (or a 'tri-clamp end cap spool', sold as such); here it is one printed part. The ferrule end takes a stock clamp and gasket against any head on this shelf.\n- What it is for: the hot end of a beta or gamma engine (the cup is the displacer cylinder, the open ferrule end gets the cold head with the rod guide), an alpha cylinder with the piston in it and the head carrying the con-rod gland, a cold-side water jacket cap, or a mock-up to check lengths before buying steel.\n- Printed cups are cold-side and mock-up parts: PETG is good to ~70 °C. For a burner-fired hot end buy a stainless capped spool and use the printed one to set the length. Inner diameter matches the steel (34.8 / 47.5 / 72.9), so the displacers and pistons on this shelf fit both.\n- Print closed end down, 0.2 mm layers, 3+ walls; the ferrule's 20° back cone needs no supports. Sand the face flat on a sheet of 400 grit on glass so the gasket seals.\n- Lengths: 1.5 in 50/75/100, 2 in 60/90/120/150, 3 in 80/120/160; the -rod3 version has a Ø3.2 centre hole in the end for a displacer rod gland on the closed end (beta engines with the drive on the hot side are rare; it is there for a cold-end cup).\n\nsize  od_mm  id_mm  length_mm  end_plate_mm  end\n1.5  38.1  34.8  50  3.0  plain\n1.5  38.1  34.8  75  3.0  plain\n1.5  38.1  34.8  100  3.0  plain\n1.5  38.1  34.8  75  3.0  Ø3.2 centre hole\n2  50.8  47.5  60  3.0  plain\n2  50.8  47.5  90  3.0  plain\n2  50.8  47.5  120  3.0  plain\n2  50.8  47.5  150  3.0  plain\n2  50.8  47.5  90  3.0  Ø3.2 centre hole\n3  76.2  72.9  80  3.0  plain\n3  76.2  72.9  120  3.0  plain\n3  76.2  72.9  160  3.0  plain\n3  76.2  72.9  120  3.0  Ø3.2 centre hole\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- ISO: ISO 2852:1993 Stainless steel clamp pipe couplings for the food industry — standard — ISO [verify license at link] — https://www.iso.org/standard/7873.html\n- Long Earth Society: Tri-clamp Stirling engine builds — web, video — LES site — https://longearthsociety.com/engineering/\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 13 parts): https://xemstudio.com/files/hardware/tri-clamp-cups/index.json\nAPI: https://xemstudio.com/api/geometry?object=tri-clamp-cups\n",
 "sources": [
  {
   "publisher": "ISO",
   "title": "ISO 2852:1993 Stainless steel clamp pipe couplings for the food industry",
   "url": "https://www.iso.org/standard/7873.html",
   "formats": [
    "standard"
   ],
   "license": "ISO",
   "license_verified": false,
   "hosted": false
  },
  {
   "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
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "tri-clamp-spool",
  "tri-clamp-ferrule",
  "tri-clamp-end-cap",
  "tri-clamp-displacers-and-heads",
  "tri-clamp-power-pistons",
  "tri-clamp-clamps"
 ],
 "fits": [
  {
   "role": "Parts that fit it",
   "items": [
    {
     "slug": "spool-hanger-collars",
     "why": "same tube OD"
    }
   ]
  },
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "tri-clamp-clamps",
     "why": "clamps its ferrule face to any head"
    }
   ]
  },
  {
   "role": "Alternatives",
   "items": [
    {
     "slug": "tri-clamp-spool",
     "why": "spool + flat end cap"
    },
    {
     "slug": "tri-clamp-end-cap",
     "why": "cap a plain spool"
    }
   ]
  },
  {
   "role": "Also needed",
   "items": [
    {
     "slug": "tri-clamp-displacers-and-heads",
     "why": "displacer and cold head"
    },
    {
     "slug": "tri-clamp-power-pistons",
     "why": "alpha cylinder piston"
    }
   ]
  }
 ],
 "faq": [
  {
   "q": "Can I use a printed tri-clamp cup as the hot end of a Stirling engine?",
   "a": "Only on a hot-plate or warm-water engine (under ~70 °C for PETG). For a tea light or burner use a stainless capped spool; print the cup to set the length and test the fit first."
  },
  {
   "q": "What is the inside diameter of a 2 inch tri-clamp cup?",
   "a": "47.5 mm, the same as a 16 ga 2 in spool, so the Ø46 displacer and the Ø47.3 lapped piston both fit."
  },
  {
   "q": "How do I print the ferrule face so it seals?",
   "a": "Face up, closed end on the bed; afterwards rub the face on 400 grit on glass until it is uniformly matte, then clamp with a stock gasket."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "cup-1.5in-50",
   "formats": [
    "step",
    "stl"
   ],
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   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-cups/cup-1.5in-50.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-cups/cup-1.5in-50.stl",
   "note": "1.5 in closed-end spool Ø38.1 × 50: ISO 2852 ferrule face, 16 ga wall, 3 mm closed end with a 1.5 mm outer fillet (the weld); print closed end down"
  },
  {
   "file": "cup-1.5in-75",
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   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-cups/cup-1.5in-75.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-cups/cup-1.5in-75.stl",
   "note": "1.5 in closed-end spool Ø38.1 × 75: ISO 2852 ferrule face, 16 ga wall, 3 mm closed end with a 1.5 mm outer fillet (the weld); print closed end down"
  },
  {
   "file": "cup-1.5in-100",
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   "stl": "https://xemstudio.com/files/hardware/tri-clamp-cups/cup-1.5in-100.stl",
   "note": "1.5 in closed-end spool Ø38.1 × 100: ISO 2852 ferrule face, 16 ga wall, 3 mm closed end with a 1.5 mm outer fillet (the weld); print closed end down"
  },
  {
   "file": "cup-1.5in-75-rod3",
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   "stl": "https://xemstudio.com/files/hardware/tri-clamp-cups/cup-1.5in-75-rod3.stl",
   "note": "1.5 in closed-end spool × 75 with a Ø3.2 centre hole in the end for a displacer rod or gland"
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  {
   "file": "cup-2in-60",
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   "stl": "https://xemstudio.com/files/hardware/tri-clamp-cups/cup-2in-60.stl",
   "note": "2 in closed-end spool Ø50.8 × 60: ISO 2852 ferrule face, 16 ga wall, 3 mm closed end with a 1.5 mm outer fillet (the weld); print closed end down"
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   "file": "cup-2in-90",
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   "note": "2 in closed-end spool Ø50.8 × 90: ISO 2852 ferrule face, 16 ga wall, 3 mm closed end with a 1.5 mm outer fillet (the weld); print closed end down"
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   "file": "cup-2in-120",
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   "note": "2 in closed-end spool Ø50.8 × 120: ISO 2852 ferrule face, 16 ga wall, 3 mm closed end with a 1.5 mm outer fillet (the weld); print closed end down"
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  {
   "file": "cup-2in-150",
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   "note": "2 in closed-end spool Ø50.8 × 150: ISO 2852 ferrule face, 16 ga wall, 3 mm closed end with a 1.5 mm outer fillet (the weld); print closed end down"
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  {
   "file": "cup-2in-90-rod3",
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   "stl": "https://xemstudio.com/files/hardware/tri-clamp-cups/cup-2in-90-rod3.stl",
   "note": "2 in closed-end spool × 90 with a Ø3.2 centre hole in the end for a displacer rod or gland"
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   "file": "cup-3in-80",
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   "stl": "https://xemstudio.com/files/hardware/tri-clamp-cups/cup-3in-80.stl",
   "note": "3 in closed-end spool Ø76.2 × 80: ISO 2852 ferrule face, 16 ga wall, 3 mm closed end with a 1.5 mm outer fillet (the weld); print closed end down"
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   "file": "cup-3in-120",
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   "stl": "https://xemstudio.com/files/hardware/tri-clamp-cups/cup-3in-120.stl",
   "note": "3 in closed-end spool Ø76.2 × 120: ISO 2852 ferrule face, 16 ga wall, 3 mm closed end with a 1.5 mm outer fillet (the weld); print closed end down"
  },
  {
   "file": "cup-3in-160",
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   "stl": "https://xemstudio.com/files/hardware/tri-clamp-cups/cup-3in-160.stl",
   "note": "3 in closed-end spool Ø76.2 × 160: ISO 2852 ferrule face, 16 ga wall, 3 mm closed end with a 1.5 mm outer fillet (the weld); print closed end down"
  },
  {
   "file": "cup-3in-120-rod3",
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   "stl": "https://xemstudio.com/files/hardware/tri-clamp-cups/cup-3in-120-rod3.stl",
   "note": "3 in closed-end spool × 120 with a Ø3.2 centre hole in the end for a displacer rod or gland"
  }
 ],
 "markdown": "https://xemstudio.com/objects/tri-clamp-cups/index.md"
}