{
 "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": "thermoacoustic-bore-spacer",
 "name": "Thermoacoustic bore spacers and liners for 2 in tri-clamp spools: 8.4, 60 and 61.7 mm",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Thermoacoustic & fluidyne",
 "year": null,
 "question": "How do I hold heat exchangers, a regenerator or a stack at the right place inside a 2 inch tri-clamp spool?",
 "tags": [
  "thermoacoustic",
  "spacer",
  "liner",
  "thermal buffer tube",
  "bore",
  "tri-clamp",
  "long earth society"
 ],
 "aliases": [
  "thermoacoustic spacer tube",
  "thermal buffer tube liner",
  "tri clamp bore spacer",
  "regenerator spacer ring",
  "heat exchanger spacer"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 3,
 "url": "https://xemstudio.com/objects/thermoacoustic-bore-spacer/",
 "sheet_txt": "https://xemstudio.com/objects/thermoacoustic-bore-spacer/sheet.txt",
 "sheet": {
  "basis": "ASME BPE 2 in bore Ø47.5; ISO 2852 Type B lip 1.95 past the face; inside Ø44 = the regenerator cage bore; lengths from the engine layouts in tools/gen_ta_family.py",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Thin tubes at the spool bore (Ø47.5 outside, Ø44 inside) that stand between the parts of a thermoacoustic core and hold each one where the acoustic design wants it. Their ends bear on the exchangers' 1.0 mm outer ring and on the gasket lip, so the whole stack is held between the two gasket lips of the spool with nothing loose.",
   "8.4: from a gasket lip to an exchanger at 10.35 mm from the face, so the exchanger sits under a 14 mm water jacket that starts 9.35 mm from the face (clear of the clamp).",
   "61.7: the loop core's thermal buffer tube liner. In a 6 in spool the stack of parts is lip, 8.4 spacer, exchanger 10, buffer tube 61.7, hot exchanger 10, regenerator 40, exchanger 10, 8.4 spacer, lip: exactly the 148.5 mm between the two lips.",
   "60: the hot-cavity liner of the standing-wave engines' closed hot end; it holds the hot exchanger 60 mm off the closed end, which in the model lowers the half-wave engine's onset from about 680 °C (exchanger on the closed end) to about 271 °C.",
   "Fits: outside slide in the bore; inside is gas passage; the end faces are flat rings."
  ],
  "table": {
   "columns": [
    "file",
    "outside_mm",
    "inside_mm",
    "length_mm",
    "use"
   ],
   "rows": [
    [
     "ta-spacer-2in-8.4",
     47.5,
     44,
     8.4,
     "end spacer"
    ],
    [
     "ta-spacer-2in-60",
     47.5,
     44,
     60,
     "hot-cavity liner"
    ],
    [
     "ta-spacer-2in-61.7",
     47.5,
     44,
     61.7,
     "thermal buffer tube"
    ]
   ]
  }
 },
 "sheet_text": "Thermoacoustic bore spacers and liners for 2 in tri-clamp spools: 8.4, 60 and 61.7 mm — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/thermoacoustic-bore-spacer/  (CC BY 4.0)\nBasis: ASME BPE 2 in bore Ø47.5; ISO 2852 Type B lip 1.95 past the face; inside Ø44 = the regenerator cage bore; lengths from the engine layouts in tools/gen_ta_family.py\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Thin tubes at the spool bore (Ø47.5 outside, Ø44 inside) that stand between the parts of a thermoacoustic core and hold each one where the acoustic design wants it. Their ends bear on the exchangers' 1.0 mm outer ring and on the gasket lip, so the whole stack is held between the two gasket lips of the spool with nothing loose.\n- 8.4: from a gasket lip to an exchanger at 10.35 mm from the face, so the exchanger sits under a 14 mm water jacket that starts 9.35 mm from the face (clear of the clamp).\n- 61.7: the loop core's thermal buffer tube liner. In a 6 in spool the stack of parts is lip, 8.4 spacer, exchanger 10, buffer tube 61.7, hot exchanger 10, regenerator 40, exchanger 10, 8.4 spacer, lip: exactly the 148.5 mm between the two lips.\n- 60: the hot-cavity liner of the standing-wave engines' closed hot end; it holds the hot exchanger 60 mm off the closed end, which in the model lowers the half-wave engine's onset from about 680 °C (exchanger on the closed end) to about 271 °C.\n- Fits: outside slide in the bore; inside is gas passage; the end faces are flat rings.\n\nfile  outside_mm  inside_mm  length_mm  use\nta-spacer-2in-8.4  47.5  44.0  8.4  end spacer\nta-spacer-2in-60  47.5  44.0  60.0  hot-cavity liner\nta-spacer-2in-61.7  47.5  44.0  61.7  thermal buffer tube\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\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, 3 parts): https://xemstudio.com/files/hardware/thermoacoustic-bore-spacer/index.json\nAPI: https://xemstudio.com/api/geometry?object=thermoacoustic-bore-spacer\n",
 "sources": [
  {
   "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": [
  "thermoacoustic-heat-exchanger",
  "regenerator-cage",
  "tri-clamp-cups",
  "list-ta-loop-2in",
  "list-ta-standing-half-wave-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": "outside",
   "exact": "Ø47.5",
   "mates": "2 in tri-clamp spool / head bore",
   "fit": "slide",
   "files": "all"
  },
  {
   "feature": "inside",
   "exact": "Ø44",
   "mates": "gas passage (no contact)",
   "fit": "designed",
   "files": "all"
  },
  {
   "feature": "end faces",
   "exact": "flat ring Ø44–Ø47.5",
   "mates": "heat-exchanger outer ring, regenerator cage end, Type B gasket lip",
   "fit": "designed",
   "files": "all"
  },
  {
   "feature": "length",
   "exact": "8.4 / 60 / 61.7",
   "mates": "positions of the exchangers, stack and regenerator in the layout",
   "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 does the buffer tube have a liner?",
   "a": "It is what the hot exchanger and the regenerator stand on: without it they would slide down the empty buffer tube."
  },
  {
   "q": "Do the spacers change the acoustics?",
   "a": "Slightly: the gas passage is Ø44 instead of Ø47.5 over their length; the model on the build lists includes it."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "ta-spacer-2in-8.4",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/thermoacoustic-bore-spacer/ta-spacer-2in-8.4.step",
   "stl": "https://xemstudio.com/files/hardware/thermoacoustic-bore-spacer/ta-spacer-2in-8.4.stl",
   "note": "Ø47.5 / Ø44 × 8.4: end spacer: from the Type B gasket lip (1.95 inside the face) to an exchanger at 8.0"
  },
  {
   "file": "ta-spacer-2in-60",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/thermoacoustic-bore-spacer/ta-spacer-2in-60.step",
   "stl": "https://xemstudio.com/files/hardware/thermoacoustic-bore-spacer/ta-spacer-2in-60.stl",
   "note": "Ø47.5 / Ø44 × 60: hot-cavity liner of the standing-wave head: closed end to the hot exchanger"
  },
  {
   "file": "ta-spacer-2in-61.7",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/thermoacoustic-bore-spacer/ta-spacer-2in-61.7.step",
   "stl": "https://xemstudio.com/files/hardware/thermoacoustic-bore-spacer/ta-spacer-2in-61.7.stl",
   "note": "Ø47.5 / Ø44 × 61.7: thermal buffer tube liner of the loop core: hot exchanger to the secondary ambient exchanger"
  }
 ],
 "markdown": "https://xemstudio.com/objects/thermoacoustic-bore-spacer/index.md"
}