{
 "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": "fpse-displacer-cylinder",
 "name": "Free-piston displacer liner: Ø40 bore, regenerator inner wall, rim clamped in the tri-clamp joint",
 "kind": "hardware",
 "category": "Hardware",
 "group": "Stirling & thermoacoustic",
 "year": null,
 "question": "How is the displacer cylinder held inside a tri-clamp hot end?",
 "tags": [
  "liner",
  "displacer",
  "free piston",
  "regenerator",
  "tri-clamp",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "displacer liner stirling",
  "free piston displacer cylinder",
  "regenerator inner wall"
 ],
 "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/fpse-displacer-cylinder/",
 "sheet_txt": "https://xemstudio.com/objects/fpse-displacer-cylinder/sheet.txt",
 "sheet": {
  "basis": "Design values of the free-piston generator: displacer bore Ø40.00 (0.30 radial gap to the Ø39.4 displacer), regenerator annulus Ø41.5–Ø47.5, rim at the ISO 2852 flange diameter",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "It hangs from joint A: its Ø64 × 0.8 rim is clamped between two half gaskets exactly like the flexure leaves, so it is centred by the clamp and sealed by the gaskets; six windows in the rim over r 20.75–23.75 let the gas from the regenerator through to the cooler.",
   "The tube (Ø40 bore, 0.75 wall) is the regenerator's inner wall and the displacer's bore, from 5 mm above the outer bottom (the gas turns under its end) to the joint.",
   "Six 10° spokes 2 thick at 73.05–75.05 mm carry the 389 screen rings and centre the tube in the bore; below them the heater insert slides onto the tube from the bottom (optional).",
   "Fits: bore Ø40 is the displacer's designed 0.30 gap (no contact); spokes and rim OD locate in the Ø47.5 bore and the clamp; the rim is clamped."
  ],
  "table": {
   "columns": [
    "feature",
    "value"
   ],
   "rows": [
    [
     "bore",
     "Ø40.00 (displacer gap 0.30)"
    ],
    [
     "tube OD",
     41.5
    ],
    [
     "rim",
     "Ø64 × 0.8, 6 windows"
    ],
    [
     "spokes",
     "6 × 10°, 2 thick, z 73.05–75.05"
    ],
    [
     "bottom end",
     "z 5 (2 above the floor)"
    ]
   ]
  }
 },
 "sheet_text": "Free-piston displacer liner: Ø40 bore, regenerator inner wall, rim clamped in the tri-clamp joint — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/fpse-displacer-cylinder/  (CC BY 4.0)\nBasis: Design values of the free-piston generator: displacer bore Ø40.00 (0.30 radial gap to the Ø39.4 displacer), regenerator annulus Ø41.5–Ø47.5, rim at the ISO 2852 flange diameter\nCatalog version: 2026-10-20\n\nSizes: see table below\n- It hangs from joint A: its Ø64 × 0.8 rim is clamped between two half gaskets exactly like the flexure leaves, so it is centred by the clamp and sealed by the gaskets; six windows in the rim over r 20.75–23.75 let the gas from the regenerator through to the cooler.\n- The tube (Ø40 bore, 0.75 wall) is the regenerator's inner wall and the displacer's bore, from 5 mm above the outer bottom (the gas turns under its end) to the joint.\n- Six 10° spokes 2 thick at 73.05–75.05 mm carry the 389 screen rings and centre the tube in the bore; below them the heater insert slides onto the tube from the bottom (optional).\n- Fits: bore Ø40 is the displacer's designed 0.30 gap (no contact); spokes and rim OD locate in the Ø47.5 bore and the clamp; the rim is clamped.\n\nfeature  value\nbore  Ø40.00 (displacer gap 0.30)\ntube OD  41.5\nrim  Ø64 × 0.8, 6 windows\nspokes  6 × 10°, 2 thick, z 73.05–75.05\nbottom end  z 5 (2 above the floor)\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Ohio University (Urieli): Stirling cycle machine analysis: ideal adiabatic and simple analysis (after Urieli & Berchowitz, Stirling Cycle Engine Analysis, 1984) — web — author's site — https://www.ohio.edu/mechanical/stirling/\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/fpse-displacer-cylinder/index.json\nAPI: https://xemstudio.com/api/geometry?object=fpse-displacer-cylinder\n",
 "sources": [
  {
   "publisher": "Ohio University (Urieli)",
   "title": "Stirling cycle machine analysis: ideal adiabatic and simple analysis (after Urieli & Berchowitz, Stirling Cycle Engine Analysis, 1984)",
   "url": "https://www.ohio.edu/mechanical/stirling/",
   "formats": [
    "web"
   ],
   "license": "author's site",
   "license_verified": true,
   "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-closed-end-spool",
  "fpse-regenerator-screen-ring",
  "fpse-fin-inserts",
  "fpse-displacer",
  "tri-clamp-leaf-half-gasket",
  "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": "bore",
   "exact": "Ø40.00",
   "mates": "displacer Ø39.4 (0.30 radial gap, no contact)",
   "fit": "designed",
   "files": "all"
  },
  {
   "feature": "rim",
   "exact": "Ø64 × 0.8",
   "mates": "two half gaskets in joint A; centred on the flange rims by the clamp",
   "fit": "clamp",
   "files": "all"
  },
  {
   "feature": "spoke tips",
   "exact": "Ø47.5",
   "mates": "hot spool bore",
   "fit": "slide",
   "files": "all"
  },
  {
   "feature": "tube OD",
   "exact": "Ø41.5",
   "mates": "heater insert bore",
   "fit": "press",
   "files": "all"
  },
  {
   "feature": "tube OD",
   "exact": "Ø41.5",
   "mates": "regenerator ring bores",
   "fit": "slide",
   "files": "all"
  },
  {
   "feature": "bottom end",
   "exact": "2 above the closed end",
   "mates": "gas passage (no contact)",
   "fit": "designed",
   "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": "Why is the liner clamped in the joint?",
   "a": "The joint centres it on the vessel's axis as accurately as the clamp centres the two spools, and the gaskets seal over it; nothing needs fixing inside the hot end."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "fpse-liner-40-rim64",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/fpse-displacer-cylinder/fpse-liner-40-rim64.step",
   "stl": "https://xemstudio.com/files/hardware/fpse-displacer-cylinder/fpse-liner-40-rim64.stl",
   "note": "displacer liner: tube Ø40 / Ø41.5 from 5 above S1's outer bottom to the rim; six 10° spokes 2 thick under the regenerator (z 73.05–75.05) out to Ø47.5; rim Ø64 × 0.8 clamped in joint A with six windows over the regenerator annulus"
  }
 ],
 "markdown": "https://xemstudio.com/objects/fpse-displacer-cylinder/index.md"
}