{
 "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": "can-engine-diaphragm",
 "name": "Can-engine diaphragm: membrane, clamp rings and centre disc, Ø40 / 50 / 60",
 "kind": "standard",
 "category": "Stirling engines",
 "group": "Can & LTD engines",
 "year": null,
 "question": "What are the dimensions of the diaphragm clamp rings for a can Stirling engine?",
 "tags": [
  "diaphragm",
  "clamp ring",
  "power piston",
  "can engine",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "diaphragm clamp ring stl",
  "stirling diaphragm piston",
  "can engine diaphragm dimensions",
  "diaphragm centre disc"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 9,
 "url": "https://xemstudio.com/objects/can-engine-diaphragm/",
 "sheet_txt": "https://xemstudio.com/objects/can-engine-diaphragm/sheet.txt",
 "sheet": {
  "basis": "Ring bore = diaphragm working diameter; centre disc at half the bore; 6 × M3 clearance (ISO 273) on the ring",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "The diaphragm power piston of the can engine: a 0.2 mm membrane clamped round its edge between two identical rings, with a stiff centre disc the con-rod screws to.",
   "Rings come in Ø40, Ø50 and Ø60 bores, each 3 thick with an outside of bore + 16 (Ø56 / 66 / 76) and 6 × Ø3.4 holes on a bore + 8 circle (Ø48 / 58 / 68).",
   "Each ring size has its own centre disc at half the bore: Ø20, Ø25 or Ø30 × 2 with a Ø3.2 hole for the M3 con-rod screw.",
   "Each membrane is the rings' outside diameter (Ø56 / 66 / 76) × 0.2 with the same six Ø3.4 holes and a Ø3.2 centre hole; its free span is the ring bore. One membrane, two rings and one disc of the same size make one diaphragm."
  ],
  "table": {
   "columns": [
    "size",
    "ring bore",
    "ring outside",
    "screw circle",
    "ring thickness",
    "disc",
    "disc hole"
   ],
   "rows": [
    [
     "40",
     40,
     56,
     48,
     3,
     "Ø20 × 2",
     3.2
    ],
    [
     "50",
     50,
     66,
     58,
     3,
     "Ø25 × 2",
     3.2
    ],
    [
     "60",
     60,
     76,
     68,
     3,
     "Ø30 × 2",
     3.2
    ]
   ]
  }
 },
 "sheet_text": "Can-engine diaphragm: membrane, clamp rings and centre disc, Ø40 / 50 / 60 — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/can-engine-diaphragm/  (CC BY 4.0)\nBasis: Ring bore = diaphragm working diameter; centre disc at half the bore; 6 × M3 clearance (ISO 273) on the ring\nCatalog version: 2026-10-20\n\nSizes: see table below\n- The diaphragm power piston of the can engine: a 0.2 mm membrane clamped round its edge between two identical rings, with a stiff centre disc the con-rod screws to.\n- Rings come in Ø40, Ø50 and Ø60 bores, each 3 thick with an outside of bore + 16 (Ø56 / 66 / 76) and 6 × Ø3.4 holes on a bore + 8 circle (Ø48 / 58 / 68).\n- Each ring size has its own centre disc at half the bore: Ø20, Ø25 or Ø30 × 2 with a Ø3.2 hole for the M3 con-rod screw.\n- Each membrane is the rings' outside diameter (Ø56 / 66 / 76) × 0.2 with the same six Ø3.4 holes and a Ø3.2 centre hole; its free span is the ring bore. One membrane, two rings and one disc of the same size make one diaphragm.\n\nsize  ring bore  ring outside  screw circle  ring thickness  disc  disc hole\n40  40  56  48  3  Ø20 × 2  3.2\n50  50  66  58  3  Ø25 × 2  3.2\n60  60  76  68  3  Ø30 × 2  3.2\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- Long Earth Society: Can engine build — video, web — LES site — https://longearthsociety.com/engineering/\n- Long Earth Society: Engine builds (videos and write-ups) — web, video — LES site — https://longearthsociety.com/engineering/\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 9 parts): https://xemstudio.com/files/hardware/can-engine-diaphragm/index.json\nAPI: https://xemstudio.com/api/geometry?object=can-engine-diaphragm\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": "Long Earth Society",
   "title": "Can engine build",
   "url": "https://longearthsociety.com/engineering/",
   "formats": [
    "video",
    "web"
   ],
   "license": "LES site",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Long Earth Society",
   "title": "Engine builds (videos and write-ups)",
   "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": [
  "can-engine-cap",
  "pin-end-con-rods",
  "list-can-engine",
  "syringe-cradle"
 ],
 "fits": [
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "pin-end-con-rods",
     "why": "con-rod screwed to the centre disc's Ø3.2 hole"
    }
   ]
  },
  {
   "role": "Alternatives",
   "items": [
    {
     "slug": "syringe-cradle",
     "why": "a syringe as the power piston instead"
    }
   ]
  },
  {
   "role": "Also needed",
   "items": [
    {
     "slug": "socket-head-cap-screws-metric",
     "why": "6 × M3 through the rings, 1 × M3 in the disc"
    }
   ]
  }
 ],
 "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": "clamp-ring screw holes",
   "exact": "Ø3.4",
   "mates": "M3 screw clearance",
   "fit": "designed",
   "files": "diaphragm-ring-"
  },
  {
   "feature": "centre-disc screw hole",
   "exact": "Ø3.2",
   "mates": "M3 screw clearance (ISO 273 fine)",
   "fit": "designed",
   "files": "diaphragm-disc-"
  }
 ],
 "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": "Which centre disc goes with which ring?",
   "a": "Half the ring bore: Ø20 disc with the Ø40 rings, Ø25 with Ø50, Ø30 with Ø60."
  },
  {
   "q": "How are the diaphragm rings fastened?",
   "a": "Six M3 screws through Ø3.4 holes on a circle 8 mm larger than the bore (Ø58 on the 50 mm ring), through both rings and the membrane."
  },
  {
   "q": "Which size does the can engine use?",
   "a": "The can-engine build list uses the Ø50 rings with the Ø25 disc."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "diaphragm-ring-40",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-ring-40.step",
   "stl": "https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-ring-40.stl",
   "note": "diaphragm clamp ring Ø40 bore × Ø56, 3 thick, 6 × Ø3.4 (M3 clearance); two per diaphragm, one each side of the membrane"
  },
  {
   "file": "diaphragm-disc-20",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-disc-20.step",
   "stl": "https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-disc-20.stl",
   "note": "diaphragm centre disc Ø20 × 2, Ø3.2 M3 clearance hole for the con-rod screw"
  },
  {
   "file": "diaphragm-membrane-40",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-membrane-40.step",
   "stl": "https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-membrane-40.stl",
   "note": "diaphragm membrane Ø56 × 0.2 with the rings' 6 × Ø3.4 holes and a Ø3.2 centre hole; free span Ø40 between the rings"
  },
  {
   "file": "diaphragm-ring-50",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-ring-50.step",
   "stl": "https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-ring-50.stl",
   "note": "diaphragm clamp ring Ø50 bore × Ø66, 3 thick, 6 × Ø3.4 (M3 clearance); two per diaphragm, one each side of the membrane"
  },
  {
   "file": "diaphragm-disc-25",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-disc-25.step",
   "stl": "https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-disc-25.stl",
   "note": "diaphragm centre disc Ø25 × 2, Ø3.2 M3 clearance hole for the con-rod screw"
  },
  {
   "file": "diaphragm-membrane-50",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-membrane-50.step",
   "stl": "https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-membrane-50.stl",
   "note": "diaphragm membrane Ø66 × 0.2 with the rings' 6 × Ø3.4 holes and a Ø3.2 centre hole; free span Ø50 between the rings"
  },
  {
   "file": "diaphragm-ring-60",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-ring-60.step",
   "stl": "https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-ring-60.stl",
   "note": "diaphragm clamp ring Ø60 bore × Ø76, 3 thick, 6 × Ø3.4 (M3 clearance); two per diaphragm, one each side of the membrane"
  },
  {
   "file": "diaphragm-disc-30",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-disc-30.step",
   "stl": "https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-disc-30.stl",
   "note": "diaphragm centre disc Ø30 × 2, Ø3.2 M3 clearance hole for the con-rod screw"
  },
  {
   "file": "diaphragm-membrane-60",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-membrane-60.step",
   "stl": "https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-membrane-60.stl",
   "note": "diaphragm membrane Ø76 × 0.2 with the rings' 6 × Ø3.4 holes and a Ø3.2 centre hole; free span Ø60 between the rings"
  }
 ],
 "markdown": "https://xemstudio.com/objects/can-engine-diaphragm/index.md"
}