{
 "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": "fluidyne-manifold",
 "name": "Fluidyne (liquid-piston Stirling) manifold and tees for 1/2 in copper U-tubes",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Thermoacoustic & fluidyne",
 "year": null,
 "question": "How do I build a fluidyne liquid piston Stirling engine and what tube sizes does it use?",
 "tags": [
  "fluidyne",
  "liquid piston",
  "stirling",
  "pump",
  "no moving parts",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "fluidyne engine",
  "liquid piston stirling engine",
  "fluidyne pump design",
  "west fluidyne",
  "fluidyne tube size"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 2,
 "url": "https://xemstudio.com/objects/fluidyne-manifold/",
 "sheet_txt": "https://xemstudio.com/objects/fluidyne-manifold/sheet.txt",
 "sheet": {
  "basis": "West's fluidyne (Harwell, 1970s): a U-tube of water is the displacer, a second water column the power piston, gas spaces above; natural period of the U-tube sets the frequency: T = 2π√(L/2g) with L the water column length",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "No solid moving parts: water in a U-tube rocks back and forth (the displacer), shuttling the gas above it between a heated and a cooled leg; a third column (the output) is pumped by the pressure swing. Frequency comes from the U-tube: T = 2π√(L/2g): a 400 mm water column oscillates at ~1.1 Hz. The hot leg is heated above the water line, the cold leg left bare or water-cooled.",
   "Tube: 1/2 in Type L copper (15.88 OD, 13.8 ID) for the U legs; glass (test tube or 16 mm borosilicate tube) for a see-through cold leg. Gas space above each leg 2–3 × the swept volume; tuning line (4 mm) between the gas spaces sets the phase (West's 'tuning column'). Output column: another 1/2 in leg with check valves for a pump.",
   "The printed manifold joins the two legs at the top with a gas passage and the tuning port; the tee adds the output column. Seal copper into the sockets with silicone; everything above the water stays under 60 °C so PETG is fine, the heated copper is below it.",
   "LES: the no-moving-parts demonstrator next to the thermoacoustic one: same spools, water instead of pistons."
  ],
  "table": {
   "columns": [
    "part",
    "size",
    "note"
   ],
   "rows": [
    [
     "U legs",
     "1/2 in copper, 300–500 long",
     "water column"
    ],
    [
     "manifold",
     "2 sockets @ 60 mm, 4 mm tuning port",
     "printed"
    ],
    [
     "output tee",
     "1/2 in + 4 mm port",
     "pump column"
    ],
    [
     "period",
     "2π√(L/2g)",
     "L = water column length"
    ]
   ]
  }
 },
 "sheet_text": "Fluidyne (liquid-piston Stirling) manifold and tees for 1/2 in copper U-tubes — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/fluidyne-manifold/  (CC BY 4.0)\nBasis: West's fluidyne (Harwell, 1970s): a U-tube of water is the displacer, a second water column the power piston, gas spaces above; natural period of the U-tube sets the frequency: T = 2π√(L/2g) with L the water column length\nCatalog version: 2026-10-20\n\nSizes: see table below\n- No solid moving parts: water in a U-tube rocks back and forth (the displacer), shuttling the gas above it between a heated and a cooled leg; a third column (the output) is pumped by the pressure swing. Frequency comes from the U-tube: T = 2π√(L/2g): a 400 mm water column oscillates at ~1.1 Hz. The hot leg is heated above the water line, the cold leg left bare or water-cooled.\n- Tube: 1/2 in Type L copper (15.88 OD, 13.8 ID) for the U legs; glass (test tube or 16 mm borosilicate tube) for a see-through cold leg. Gas space above each leg 2–3 × the swept volume; tuning line (4 mm) between the gas spaces sets the phase (West's 'tuning column'). Output column: another 1/2 in leg with check valves for a pump.\n- The printed manifold joins the two legs at the top with a gas passage and the tuning port; the tee adds the output column. Seal copper into the sockets with silicone; everything above the water stays under 60 °C so PETG is fine, the heated copper is below it.\n- LES: the no-moving-parts demonstrator next to the thermoacoustic one: same spools, water instead of pistons.\n\npart  size  note\nU legs  1/2 in copper, 300–500 long  water column\nmanifold  2 sockets @ 60 mm, 4 mm tuning port  printed\noutput tee  1/2 in + 4 mm port  pump column\nperiod  2π√(L/2g)  L = water column length\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Wikipedia: Fluidyne engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Fluidyne\n- C. D. West: Liquid Piston Stirling Engines (1983) — book, reports (OSTI) — reference / US Gov reports public domain [verify license at link] — https://www.osti.gov/search/semantic:fluidyne\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, 2 parts): https://xemstudio.com/files/hardware/fluidyne-manifold/index.json\nAPI: https://xemstudio.com/api/geometry?object=fluidyne-manifold\n",
 "sources": [
  {
   "publisher": "Wikipedia",
   "title": "Fluidyne engine",
   "url": "https://en.wikipedia.org/wiki/Fluidyne",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "C. D. West",
   "title": "Liquid Piston Stirling Engines (1983)",
   "url": "https://www.osti.gov/search/semantic:fluidyne",
   "formats": [
    "book",
    "reports (OSTI)"
   ],
   "license": "reference / US Gov reports public domain",
   "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": [
  "copper-pipe-type-l-m",
  "borosilicate-test-tubes",
  "silicone-tube-and-fittings",
  "stirling-configurations-guide",
  "thermoacoustic-stacks-and-resonators"
 ],
 "fits": [],
 "faq": [
  {
   "q": "What is a fluidyne engine?",
   "a": "A Stirling engine whose displacer and piston are columns of water in U-tubes; gas above the water is heated and cooled as the water rocks. No solid moving parts; it pumps water."
  },
  {
   "q": "What sets a fluidyne's frequency?",
   "a": "The U-tube's natural period, T = 2π√(L/2g): a 400 mm water column gives about 1.1 Hz; longer columns are slower."
  },
  {
   "q": "What tube size for a fluidyne?",
   "a": "1/2 in copper (15.88 mm) legs 300–500 mm long with the gas spaces above; a 4 mm tuning line between the gas spaces sets the phase."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "fluidyne-manifold-2x-1-2in-copper",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/fluidyne-manifold/fluidyne-manifold-2x-1-2in-copper.step",
   "stl": "https://xemstudio.com/files/hardware/fluidyne-manifold/fluidyne-manifold-2x-1-2in-copper.stl",
   "note": "fluidyne displacer manifold: two Ø15.88 (1/2 in copper) sockets 60 mm apart joined by a gas passage, 4 mm tuning port"
  },
  {
   "file": "fluidyne-output-tee-1-2in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/fluidyne-manifold/fluidyne-output-tee-1-2in.step",
   "stl": "https://xemstudio.com/files/hardware/fluidyne-manifold/fluidyne-output-tee-1-2in.stl",
   "note": "output-column tee for 1/2 in copper with a 4 mm side port"
  }
 ],
 "markdown": "https://xemstudio.com/objects/fluidyne-manifold/index.md"
}