{
 "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-hot-fin-sleeve",
 "name": "Thermoacoustic hot-end fin sleeve: radial fins that slide over a 2 in closed-end cup",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Thermoacoustic & fluidyne",
 "year": null,
 "question": "How do I put fins on the hot end of a tri-clamp thermoacoustic engine?",
 "tags": [
  "thermoacoustic",
  "fins",
  "heat exchanger",
  "hot end",
  "optional",
  "tri-clamp",
  "long earth society"
 ],
 "aliases": [
  "thermoacoustic hot end fins",
  "slide on fins 2 inch tube",
  "finned sleeve tri clamp",
  "propane heated thermoacoustic engine fins"
 ],
 "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/thermoacoustic-hot-fin-sleeve/",
 "sheet_txt": "https://xemstudio.com/objects/thermoacoustic-hot-fin-sleeve/sheet.txt",
 "sheet": {
  "basis": "ASME BPE 2 in tube OD Ø50.8 (the sleeve's bore); fin count, thickness and reach are design values; M4 set screws ISO 4026",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "A separate, optional heat exchanger for the closed hot end of the standing-wave engines: a sleeve whose bore is exactly the tube's Ø50.8 slides over the closed end of the plain cup-2in-133.35 (a standard closed-end 2 in spool, 133.35 mm), and 16 radial fins carry the torch's heat into the hot cavity and the hot exchanger. Three M4 set screws in a band above the fins hold it.",
   "It covers 49 to 131.85 mm from the cup's face, so it stays clear of the water jacket and the clamp; the fins reach Ø80, as far from the tube as the Ø76 fins the hot end used to carry built on.",
   "Without it the flame heats the bare cup: the engine is complete and still runs, but needs more heat to start. The cup stays a plain part a sanitary fabricator makes; the sleeve can be made any way you like.",
   "Fits: the bore slides on the tube OD (slide fit), the set screws clamp it."
  ],
  "table": {
   "columns": [
    "feature",
    "value"
   ],
   "rows": [
    [
     "bore",
     "Ø50.8 (tube OD)"
    ],
    [
     "length",
     82.85
    ],
    [
     "wall",
     2
    ],
    [
     "fins",
     "16 × 1.6 thick, to Ø80"
    ],
    [
     "set screws",
     "3 × M4, 0 / 120 / 240°"
    ],
    [
     "fits",
     "cup-2in-133.35"
    ]
   ]
  }
 },
 "sheet_text": "Thermoacoustic hot-end fin sleeve: radial fins that slide over a 2 in closed-end cup — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/thermoacoustic-hot-fin-sleeve/  (CC BY 4.0)\nBasis: ASME BPE 2 in tube OD Ø50.8 (the sleeve's bore); fin count, thickness and reach are design values; M4 set screws ISO 4026\nCatalog version: 2026-10-20\n\nSizes: see table below\n- A separate, optional heat exchanger for the closed hot end of the standing-wave engines: a sleeve whose bore is exactly the tube's Ø50.8 slides over the closed end of the plain cup-2in-133.35 (a standard closed-end 2 in spool, 133.35 mm), and 16 radial fins carry the torch's heat into the hot cavity and the hot exchanger. Three M4 set screws in a band above the fins hold it.\n- It covers 49 to 131.85 mm from the cup's face, so it stays clear of the water jacket and the clamp; the fins reach Ø80, as far from the tube as the Ø76 fins the hot end used to carry built on.\n- Without it the flame heats the bare cup: the engine is complete and still runs, but needs more heat to start. The cup stays a plain part a sanitary fabricator makes; the sleeve can be made any way you like.\n- Fits: the bore slides on the tube OD (slide fit), the set screws clamp it.\n\nfeature  value\nbore  Ø50.8 (tube OD)\nlength  82.85\nwall  2.0\nfins  16 × 1.6 thick, to Ø80\nset screws  3 × M4, 0 / 120 / 240°\nfits  cup-2in-133.35\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- G. W. Swift (LANL / Acoustical Society of America): Thermoacoustics: A Unifying Perspective for Some Engines and Refrigerators (Rott's equations, screen relations, DeltaEC) — web, software — LANL [verify license at link] — https://www.lanl.gov/org/ddste/aldps/materials-physics-applications/condensed-matter-magnet-science/thermoacoustics/\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/thermoacoustic-hot-fin-sleeve/index.json\nAPI: https://xemstudio.com/api/geometry?object=thermoacoustic-hot-fin-sleeve\n",
 "sources": [
  {
   "publisher": "G. W. Swift (LANL / Acoustical Society of America)",
   "title": "Thermoacoustics: A Unifying Perspective for Some Engines and Refrigerators (Rott's equations, screen relations, DeltaEC)",
   "url": "https://www.lanl.gov/org/ddste/aldps/materials-physics-applications/condensed-matter-magnet-science/thermoacoustics/",
   "formats": [
    "web",
    "software"
   ],
   "license": "LANL",
   "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": [
  "tri-clamp-cups",
  "thermoacoustic-stack",
  "thermoacoustic-heat-exchanger",
  "thermoacoustic-bore-spacer",
  "thermoacoustic-water-jacket",
  "set-screws-metric",
  "list-ta-standing-quarter-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": "bore",
   "exact": "Ø50.8 = the 2 in tube OD",
   "mates": "cup-2in-133.35 tube OD (over its closed end)",
   "fit": "slide",
   "files": "all"
  },
  {
   "feature": "set-screw holes",
   "exact": "3 × Ø3.3 at 0 / 120 / 240°",
   "mates": "M4 tap drill; M4 × 4 set screws onto the tube OD",
   "fit": "clamp",
   "files": "all"
  },
  {
   "feature": "fins",
   "exact": "16 × 1.6 to Ø80, 56–131.85 from the cup face",
   "mates": "torch flame (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": "Do I need it?",
   "a": "No. It is an optional heat exchanger; without it the engine needs more heat at the cup to start."
  },
  {
   "q": "Why not fins on the cup itself?",
   "a": "Sanitary fabricators make plain spools and closed-end cups; fins built onto one are not something they make. A separate sleeve keeps the cup standard."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "ta-fin-sleeve-2in-16x80",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/thermoacoustic-hot-fin-sleeve/ta-fin-sleeve-2in-16x80.step",
   "stl": "https://xemstudio.com/files/hardware/thermoacoustic-hot-fin-sleeve/ta-fin-sleeve-2in-16x80.stl",
   "note": "radial-fin sleeve for the 2 in tube: bore Ø50.8 (the tube OD) × 82.85, 2 mm wall, 16 radial fins 1.6 thick to Ø80 over the last 75.85, 7 mm band with 3 × M4 tapped (Ø3.3) at 0 / 120 / 240°; drawn in the cup's frame (49 to 131.85 from its face)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/thermoacoustic-hot-fin-sleeve/index.md"
}