{
 "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-regenerative-displacer",
 "name": "Tri-clamp regenerative displacer: Ø31.8, Ø44.5 and Ø69.9 with 12 slots, 1.5 mm gap",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Tri-clamp engine parts",
 "year": null,
 "question": "What is a regenerative displacer and what size fits a tri-clamp spool?",
 "tags": [
  "displacer",
  "regenerator",
  "tri-clamp",
  "stirling",
  "beta",
  "annular gap",
  "long earth society"
 ],
 "aliases": [
  "regenerative displacer",
  "annular gap regenerator displacer",
  "tri clamp beta displacer",
  "senft regenerative displacer",
  "displacer with regenerator"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 6,
 "url": "https://xemstudio.com/objects/tri-clamp-regenerative-displacer/",
 "sheet_txt": "https://xemstudio.com/objects/tri-clamp-regenerative-displacer/sheet.txt",
 "sheet": {
  "basis": "Spool bore minus a 1.5 mm radial gap (Senft annular-gap regenerator); 16 ga ASME BPE bores 34.8 / 47.5 / 72.9 mm",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "An annular-gap regenerative displacer: the 1.5 mm radial gap between it and the spool is the regenerator path, so one spool with this displacer is a complete engine with no separate regenerator section.",
   "Sizes: 1.5 in Ø31.8 × 75, 2 in Ø44.5 × 90, 3 in Ø69.9 × 120 mm. Wall 1.5 mm, closed rounded end, open at the cap end.",
   "Twelve radial slots 1.2 mm wide run through the wall over the middle 70 % of the length (from 15 % to 85 % of L); they are the pockets for the regenerator matrix.",
   "Its cap has a spigot Ø(D − 3) × 3 into the shell, a Ø D × 1.5 flange and a Ø16 × 6 boss with the Ø3 rod hole; 10.5 mm overall."
  ],
  "table": {
   "columns": [
    "spool_in",
    "bore_mm",
    "displacer_od_mm",
    "length_mm",
    "radial_gap_mm",
    "slots"
   ],
   "rows": [
    [
     "1.5",
     34.8,
     31.8,
     75,
     1.5,
     12
    ],
    [
     "2",
     47.5,
     44.5,
     90,
     1.5,
     12
    ],
    [
     "3",
     72.9,
     69.9,
     120,
     1.5,
     12
    ]
   ]
  }
 },
 "sheet_text": "Tri-clamp regenerative displacer: Ø31.8, Ø44.5 and Ø69.9 with 12 slots, 1.5 mm gap — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/tri-clamp-regenerative-displacer/  (CC BY 4.0)\nBasis: Spool bore minus a 1.5 mm radial gap (Senft annular-gap regenerator); 16 ga ASME BPE bores 34.8 / 47.5 / 72.9 mm\nCatalog version: 2026-10-20\n\nSizes: see table below\n- An annular-gap regenerative displacer: the 1.5 mm radial gap between it and the spool is the regenerator path, so one spool with this displacer is a complete engine with no separate regenerator section.\n- Sizes: 1.5 in Ø31.8 × 75, 2 in Ø44.5 × 90, 3 in Ø69.9 × 120 mm. Wall 1.5 mm, closed rounded end, open at the cap end.\n- Twelve radial slots 1.2 mm wide run through the wall over the middle 70 % of the length (from 15 % to 85 % of L); they are the pockets for the regenerator matrix.\n- Its cap has a spigot Ø(D − 3) × 3 into the shell, a Ø D × 1.5 flange and a Ø16 × 6 boss with the Ø3 rod hole; 10.5 mm overall.\n\nspool_in  bore_mm  displacer_od_mm  length_mm  radial_gap_mm  slots\n1.5  34.8  31.8  75  1.5  12\n2  47.5  44.5  90  1.5  12\n3  72.9  69.9  120  1.5  12\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Long Earth Society: Tri-clamp Stirling engine builds — web, video — LES site — https://longearthsociety.com/engineering/\n- James R. Senft: An Introduction to Low Temperature Differential Stirling Engines (displacer and gap design) — book — Moriya Press [verify license at link] — https://www.stirlingengine.com/\n- Wikipedia: Stirling engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Stirling_engine\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 6 parts): https://xemstudio.com/files/hardware/tri-clamp-regenerative-displacer/index.json\nAPI: https://xemstudio.com/api/geometry?object=tri-clamp-regenerative-displacer\n",
 "sources": [
  {
   "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
  },
  {
   "publisher": "James R. Senft",
   "title": "An Introduction to Low Temperature Differential Stirling Engines (displacer and gap design)",
   "url": "https://www.stirlingengine.com/",
   "formats": [
    "book"
   ],
   "license": "Moriya Press",
   "license_verified": false,
   "hosted": false
  },
  {
   "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
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "tri-clamp-displacer",
  "tri-clamp-crank-head",
  "tri-clamp-spool",
  "regenerator-mesh-disc",
  "tri-clamp-power-piston"
 ],
 "fits": [
  {
   "role": "Goes in or on",
   "items": [
    {
     "slug": "tri-clamp-spool",
     "why": "Ø44.5 in the Ø47.5 bore, 1.5 mm radial gap"
    }
   ]
  },
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "tri-clamp-crank-head",
     "why": "Ø3 rod through the cold-end head"
    }
   ]
  },
  {
   "role": "Alternatives",
   "items": [
    {
     "slug": "tri-clamp-displacer",
     "why": "plain displacer with a separate regenerator"
    }
   ]
  },
  {
   "role": "Also needed",
   "items": [
    {
     "slug": "regenerator-mesh-disc",
     "why": "matrix in the 12 slots"
    }
   ]
  }
 ],
 "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": "displacer OD in the spool bore",
   "exact": "bore − 2 × 0.6 / 0.75 / 1.0",
   "mates": "tri-clamp-spool bore",
   "fit": "designed",
   "files": "displacer-"
  },
  {
   "feature": "regenerative displacer OD in the spool bore",
   "exact": "bore − 2 × 1.5",
   "mates": "tri-clamp-spool bore",
   "fit": "designed",
   "files": "displacer-regenerative-"
  },
  {
   "feature": "regenerative cap spigot in the shell",
   "exact": "shell bore (bore − 6)",
   "mates": "regenerative displacer shell",
   "fit": "slide",
   "files": "displacer-regenerative-cap-"
  },
  {
   "feature": "regenerative cap rod hole",
   "exact": "Ø3",
   "mates": "Ø3 displacer rod",
   "fit": "slide",
   "files": "displacer-regenerative-cap-"
  }
 ],
 "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": "What is a regenerative displacer?",
   "a": "A displacer whose gap to the cylinder is the regenerator: here a 1.5 mm radial gap with 12 slotted pockets in the wall, so the gas passes the matrix every stroke."
  },
  {
   "q": "What size regenerative displacer for a 2 inch spool?",
   "a": "Ø44.5 × 90 mm in the Ø47.5 bore, 1.5 mm radial gap."
  },
  {
   "q": "How big are the slots?",
   "a": "1.2 mm wide, through the 1.5 mm wall, 12 around, over the middle 70 % of the length: 63 mm on the 2 in displacer."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "displacer-regenerative-1.5in-75",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/displacer-regenerative-1.5in-75.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/displacer-regenerative-1.5in-75.stl",
   "note": "1.5 in annular-gap regenerative displacer Ø31.8 × 75: 12 radial slots for regenerator mesh, 1.5 mm radial gap"
  },
  {
   "file": "displacer-regenerative-cap-1.5in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/displacer-regenerative-cap-1.5in.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/displacer-regenerative-cap-1.5in.stl",
   "note": "cap for the 1.5 in regenerative displacer: Ø28.8 × 3 spigot, Ø31.8 × 1.5 flange, Ø16 × 6 boss with the Ø3 rod bore and an M3 grub (Ø2.5 tapped) at 8 mm"
  },
  {
   "file": "displacer-regenerative-2in-90",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/displacer-regenerative-2in-90.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/displacer-regenerative-2in-90.stl",
   "note": "2 in annular-gap regenerative displacer Ø44.5 × 90: 12 radial slots for regenerator mesh, 1.5 mm radial gap"
  },
  {
   "file": "displacer-regenerative-cap-2in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/displacer-regenerative-cap-2in.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/displacer-regenerative-cap-2in.stl",
   "note": "cap for the 2 in regenerative displacer: Ø41.5 × 3 spigot, Ø44.5 × 1.5 flange, Ø16 × 6 boss with the Ø3 rod bore and an M3 grub (Ø2.5 tapped) at 8 mm"
  },
  {
   "file": "displacer-regenerative-3in-120",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/displacer-regenerative-3in-120.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/displacer-regenerative-3in-120.stl",
   "note": "3 in annular-gap regenerative displacer Ø69.9 × 120: 12 radial slots for regenerator mesh, 1.5 mm radial gap"
  },
  {
   "file": "displacer-regenerative-cap-3in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/displacer-regenerative-cap-3in.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/displacer-regenerative-cap-3in.stl",
   "note": "cap for the 3 in regenerative displacer: Ø66.9 × 3 spigot, Ø69.9 × 1.5 flange, Ø16 × 6 boss with the Ø3 rod bore and an M3 grub (Ø2.5 tapped) at 8 mm"
  }
 ],
 "markdown": "https://xemstudio.com/objects/tri-clamp-regenerative-displacer/index.md"
}