{
 "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": "list-ta-twin-piston-2in",
 "name": "Build list: Thermoacoustic-Stirling engine with twin free-piston alternators, 2 in, pressurised",
 "kind": "list",
 "category": "Stirling engines",
 "group": "Guide",
 "year": null,
 "question": "What parts do I need to build a Thermoacoustic-Stirling engine with twin free-piston alternators, 2 in, pressurised?",
 "tags": [
  "list",
  "build",
  "thermoacoustic",
  "free piston",
  "linear alternator",
  "long earth society",
  "tri-clamp",
  "pressurised",
  "thermoacoustic-stirling",
  "twin piston",
  "helium",
  "torch",
  "jet pump"
 ],
 "aliases": [
  "thermoacoustic stirling engine alternator",
  "tashe free piston",
  "thermoacoustic generator jet pump",
  "twin piston thermoacoustic"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "not-scanned",
 "les": true,
 "free_files": 0,
 "url": "https://xemstudio.com/objects/list-ta-twin-piston-2in/",
 "sheet_txt": "https://xemstudio.com/objects/list-ta-twin-piston-2in/sheet.txt",
 "sheet": {
  "basis": "Every part is a free STEP/STL on this site or a standard part with its own page; quantities are the full count, every screw, nut, gasket and clamp. Numbers from the linear network model in tools/gen_ta_power.py (Rott / Swift equations, written from the published method).",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Backhaus & Swift's thermoacoustic-Stirling torus in 2 in tri-clamp with two opposed free-piston alternators on the junction cross, a jet pump, helium charge and a torch drum.",
   "Numbers: 20 bar helium · 24 Hz · onset 204 °C with the alternators open · ≈ 9 W electric for ≈ 67 W into the hot exchanger (14 %) at ±8 mm (model)"
  ],
  "table": {
   "columns": [
    "subsystem",
    "object",
    "parts",
    "qty",
    "note"
   ],
   "rows": [
    [
     null,
     "tri-clamp-custom-length-spools",
     "spool-2in-310.7mm",
     1,
     "core: plain 2 in tube with full ferrules"
    ],
    [
     null,
     "thermoacoustic-bore-spacer",
     "ta-spacer-2in-8.4",
     2,
     "gasket lip to each ambient exchanger"
    ],
    [
     null,
     "thermoacoustic-slotted-exchanger-insert",
     "hx-insert-2in-14",
     2,
     "main ambient (top) and secondary ambient (bottom) exchanger"
    ],
    [
     null,
     "regenerator-screen-disc-47-5",
     "screen-disc-47.5-m100",
     550,
     "regenerator: 110 mm of 100-mesh × 0.10 screen"
    ],
    [
     null,
     "thermoacoustic-slotted-exchanger-insert",
     "hx-insert-2in-12",
     1,
     "hot exchanger"
    ],
    [
     null,
     "thermoacoustic-buffer-tube-liner",
     "tbt-liner-2in-140",
     1,
     "thermal buffer tube"
    ],
    [
     null,
     "sanitary-clamp-crosses",
     "cross-2in",
     1,
     "the junction: core up, inertance down, a piston each side"
    ],
    [
     null,
     "thermoacoustic-jet-pump",
     "jet-pump-2in-30",
     1,
     "in the cross's lower branch, on the gasket lip: stops the steady flow round the torus"
    ],
    [
     null,
     "tri-clamp-caps-with-welded-boss",
     "cap-2in-x-0.75in-ferrule",
     2,
     "top of the core and bottom of the cross: the ¾ in inertance line joins here"
    ],
    [
     null,
     "tri-clamp-honed-cylinder-spool",
     "spool-2in-6in-honed-48.00",
     2,
     "piston cylinders, either side of the cross"
    ],
    [
     null,
     "free-piston-mover-2in",
     "mover-core-2in-130",
     2,
     ""
    ],
    [
     null,
     "free-piston-mover-2in",
     "mover-sleeve-48x130",
     2,
     ""
    ],
    [
     null,
     "neodymium-block-magnets",
     "magnet-block-30x10x4",
     96,
     "48 per mover"
    ],
    [
     null,
     "canned-linear-alternator-stator-2in",
     "stator-bobbin-half-2in-112",
     4,
     ""
    ],
    [
     null,
     "canned-linear-alternator-stator-2in",
     "stator-coil-2in-14x7",
     8,
     ""
    ],
    [
     null,
     "canned-linear-alternator-stator-2in",
     "stator-iron-half-2in-112",
     4,
     ""
    ],
    [
     null,
     "socket-head-cap-screws-metric",
     "shcs-m4x16",
     14,
     "return-shell ears (12), fin-sleeve ears (2, optional)"
    ],
    [
     null,
     "tri-clamp-flexure-carrier",
     "flexure-carrier-2in-60",
     2,
     "outboard of each cylinder"
    ],
    [
     null,
     "spiral-flexure-bearing",
     "flexure-40-3arm-w1.6-t0.5",
     8,
     "two per stack, opposite spiral hand"
    ],
    [
     null,
     "flexure-stack-spacer",
     "spacer-40-t2",
     4,
     ""
    ],
    [
     null,
     "flexure-rim-clamp-plate",
     "clamp-plate-40",
     4,
     ""
    ],
    [
     null,
     "flexure-hub-clamp-washer",
     "hub-clamp-40-b4",
     4,
     ""
    ],
    [
     null,
     "socket-head-cap-screws-metric",
     "shcs-m3x10",
     12,
     "stack rims into the carrier ledges"
    ],
    [
     null,
     "threaded-rods-metric",
     "rod-m4x195.9",
     2,
     ""
    ],
    [
     null,
     "hex-nuts-metric",
     "nut-m4",
     33,
     "hub nuts (8), return-shell ears (12), drum tabs (3), hangers (4), jackets (4, optional), fin sleeve (2, optional)"
    ],
    [
     null,
     "flat-washers-metric",
     "washer-m4",
     8,
     "under each hub nut"
    ],
    [
     null,
     "tri-clamp-spool",
     "tc-spool-2in-12in",
     2,
     "bounce spaces outboard of the carriers"
    ],
    [
     null,
     "tri-clamp-end-cap",
     "tc-cap-2in-flat",
     2,
     "close the bounce spools"
    ],
    [
     null,
     "tri-clamp-gasket",
     "tc-gasket-2in",
     11,
     "Type B profile at every 2 in joint, rated above the relief setting at the joint's temperature"
    ],
    [
     null,
     "sanitary-clamp-elbows",
     "elbow-90-0.75in",
     4,
     ""
    ],
    [
     null,
     "sanitary-clamp-spools",
     "spool-0.75in-12in",
     2,
     "bottom and top runs"
    ],
    [
     null,
     "sanitary-clamp-spools",
     "spool-0.75in-3in",
     1,
     "riser, lowest spool"
    ],
    [
     null,
     "sanitary-clamp-spools",
     "spool-0.75in-6in",
     1,
     "riser, top spool"
    ],
    [
     null,
     "tri-clamp-custom-length-spools",
     "spool-0.75in-80.4mm",
     1,
     "riser between the tee and the cross"
    ],
    [
     null,
     "sanitary-clamp-tees",
     "tee-0.75in",
     1,
     "fill branch"
    ],
    [
     null,
     "sanitary-clamp-crosses",
     "cross-0.75in",
     1,
     "gauge and relief branches"
    ],
    [
     null,
     "tri-clamp-caps-with-welded-boss",
     "cap-0.75in-x-1-4npt",
     3,
     "close the branches; each carries a 1/4 NPT instrument"
    ],
    [
     null,
     "npt-thread-envelopes",
     "npt-1-4-male",
     3,
     "1/4 NPT stems of the fill valve, pressure gauge and relief valve"
    ],
    [
     null,
     "sanitary-clamp-gaskets",
     "gasket-0.75in",
     15,
     "Type B profile at every ¾ in joint"
    ],
    [
     null,
     "thermoacoustic-burner-drum",
     "drum-single-lower",
     1,
     "round the hot zone; flue to the front, down to the torch"
    ],
    [
     null,
     "thermoacoustic-burner-drum",
     "drum-single-upper",
     1,
     ""
    ],
    [
     null,
     "socket-head-cap-screws-metric",
     "shcs-m4x20",
     7,
     "drum tabs (3), hangers (2 per hanger)"
    ],
    [
     null,
     "tri-clamp-torch-stand",
     "torch-stand-40",
     1,
     "on the bench under the flue; propane / butane torch head in its ring"
    ],
    [
     null,
     "set-screws-metric",
     "set-m4x10",
     3,
     "centre the torch head"
    ],
    [
     null,
     "thermoacoustic-water-jacket",
     "ta-jacket-half-2in-14",
     4,
     "optional: over the two ambient exchangers"
    ],
    [
     null,
     "socket-head-cap-screws-metric",
     "shcs-m4x25",
     4,
     "optional: jacket ears"
    ],
    [
     null,
     "thermoacoustic-fin-sleeve",
     "fin-sleeve-half-2in-34",
     2,
     "optional: over the hot exchanger inside the drum"
    ],
    [
     null,
     "tube-hanger-post",
     "hanger-post-2in-h235.3",
     2,
     "under the bounce spools: the engine stands on these two posts"
    ],
    [
     null,
     "spool-hanger-collars",
     "hanger-2in-tab",
     2,
     "round the bounce spools, bars to the posts"
    ],
    [
     null,
     "spool-hanger-collars",
     "hanger-2in-plain",
     2,
     ""
    ],
    [
     null,
     "socket-head-cap-screws-metric",
     "shcs-m5x16",
     4,
     "hanger bars into the posts' tapped holes"
    ]
   ]
  }
 },
 "sheet_text": "Build list: Thermoacoustic-Stirling engine with twin free-piston alternators, 2 in, pressurised — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/list-ta-twin-piston-2in/  (CC BY 4.0)\nBasis: Every part is a free STEP/STL on this site or a standard part with its own page; quantities are the full count, every screw, nut, gasket and clamp. Numbers from the linear network model in tools/gen_ta_power.py (Rott / Swift equations, written from the published method).\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Backhaus & Swift's thermoacoustic-Stirling torus in 2 in tri-clamp with two opposed free-piston alternators on the junction cross, a jet pump, helium charge and a torch drum.\n- Numbers: 20 bar helium · 24 Hz · onset 204 °C with the alternators open · ≈ 9 W electric for ≈ 67 W into the hot exchanger (14 %) at ±8 mm (model)\n\nsubsystem  object  parts  qty  note\nNone  tri-clamp-custom-length-spools  spool-2in-310.7mm  1  core: plain 2 in tube with full ferrules\nNone  thermoacoustic-bore-spacer  ta-spacer-2in-8.4  2  gasket lip to each ambient exchanger\nNone  thermoacoustic-slotted-exchanger-insert  hx-insert-2in-14  2  main ambient (top) and secondary ambient (bottom) exchanger\nNone  regenerator-screen-disc-47-5  screen-disc-47.5-m100  550  regenerator: 110 mm of 100-mesh × 0.10 screen\nNone  thermoacoustic-slotted-exchanger-insert  hx-insert-2in-12  1  hot exchanger\nNone  thermoacoustic-buffer-tube-liner  tbt-liner-2in-140  1  thermal buffer tube\nNone  sanitary-clamp-crosses  cross-2in  1  the junction: core up, inertance down, a piston each side\nNone  thermoacoustic-jet-pump  jet-pump-2in-30  1  in the cross's lower branch, on the gasket lip: stops the steady flow round the torus\nNone  tri-clamp-caps-with-welded-boss  cap-2in-x-0.75in-ferrule  2  top of the core and bottom of the cross: the ¾ in inertance line joins here\nNone  tri-clamp-honed-cylinder-spool  spool-2in-6in-honed-48.00  2  piston cylinders, either side of the cross\nNone  free-piston-mover-2in  mover-core-2in-130  2  \nNone  free-piston-mover-2in  mover-sleeve-48x130  2  \nNone  neodymium-block-magnets  magnet-block-30x10x4  96  48 per mover\nNone  canned-linear-alternator-stator-2in  stator-bobbin-half-2in-112  4  \nNone  canned-linear-alternator-stator-2in  stator-coil-2in-14x7  8  \nNone  canned-linear-alternator-stator-2in  stator-iron-half-2in-112  4  \nNone  socket-head-cap-screws-metric  shcs-m4x16  14  return-shell ears (12), fin-sleeve ears (2, optional)\nNone  tri-clamp-flexure-carrier  flexure-carrier-2in-60  2  outboard of each cylinder\nNone  spiral-flexure-bearing  flexure-40-3arm-w1.6-t0.5  8  two per stack, opposite spiral hand\nNone  flexure-stack-spacer  spacer-40-t2  4  \nNone  flexure-rim-clamp-plate  clamp-plate-40  4  \nNone  flexure-hub-clamp-washer  hub-clamp-40-b4  4  \nNone  socket-head-cap-screws-metric  shcs-m3x10  12  stack rims into the carrier ledges\nNone  threaded-rods-metric  rod-m4x195.9  2  \nNone  hex-nuts-metric  nut-m4  33  hub nuts (8), return-shell ears (12), drum tabs (3), hangers (4), jackets (4, optional), fin sleeve (2, optional)\nNone  flat-washers-metric  washer-m4  8  under each hub nut\nNone  tri-clamp-spool  tc-spool-2in-12in  2  bounce spaces outboard of the carriers\nNone  tri-clamp-end-cap  tc-cap-2in-flat  2  close the bounce spools\nNone  tri-clamp-gasket  tc-gasket-2in  11  Type B profile at every 2 in joint, rated above the relief setting at the joint's temperature\nNone  sanitary-clamp-elbows  elbow-90-0.75in  4  \nNone  sanitary-clamp-spools  spool-0.75in-12in  2  bottom and top runs\nNone  sanitary-clamp-spools  spool-0.75in-3in  1  riser, lowest spool\nNone  sanitary-clamp-spools  spool-0.75in-6in  1  riser, top spool\nNone  tri-clamp-custom-length-spools  spool-0.75in-80.4mm  1  riser between the tee and the cross\nNone  sanitary-clamp-tees  tee-0.75in  1  fill branch\nNone  sanitary-clamp-crosses  cross-0.75in  1  gauge and relief branches\nNone  tri-clamp-caps-with-welded-boss  cap-0.75in-x-1-4npt  3  close the branches; each carries a 1/4 NPT instrument\nNone  npt-thread-envelopes  npt-1-4-male  3  1/4 NPT stems of the fill valve, pressure gauge and relief valve\nNone  sanitary-clamp-gaskets  gasket-0.75in  15  Type B profile at every ¾ in joint\nNone  thermoacoustic-burner-drum  drum-single-lower  1  round the hot zone; flue to the front, down to the torch\nNone  thermoacoustic-burner-drum  drum-single-upper  1  \nNone  socket-head-cap-screws-metric  shcs-m4x20  7  drum tabs (3), hangers (2 per hanger)\nNone  tri-clamp-torch-stand  torch-stand-40  1  on the bench under the flue; propane / butane torch head in its ring\nNone  set-screws-metric  set-m4x10  3  centre the torch head\nNone  thermoacoustic-water-jacket  ta-jacket-half-2in-14  4  optional: over the two ambient exchangers\nNone  socket-head-cap-screws-metric  shcs-m4x25  4  optional: jacket ears\nNone  thermoacoustic-fin-sleeve  fin-sleeve-half-2in-34  2  optional: over the hot exchanger inside the drum\nNone  tube-hanger-post  hanger-post-2in-h235.3  2  under the bounce spools: the engine stands on these two posts\nNone  spool-hanger-collars  hanger-2in-tab  2  round the bounce spools, bars to the posts\nNone  spool-hanger-collars  hanger-2in-plain  2  \nNone  socket-head-cap-screws-metric  shcs-m5x16  4  hanger bars into the posts' tapped holes\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Nature (S. Backhaus, G. W. Swift): A thermoacoustic Stirling heat engine, Nature 399, 335-338 (1999) — web — journal article; cited [verify license at link] — https://doi.org/10.1038/20624\n- J. Acoust. Soc. Am. (S. Backhaus, G. W. Swift): A thermoacoustic-Stirling heat engine: detailed study, JASA 107(6), 3148 (2000): torus with inertance and compliance, thermal buffer tube, jet pump against Gedeon streaming — web — journal article; cited [verify license at link] — https://doi.org/10.1121/1.429343\n- Appl. Phys. Lett. (S. Backhaus, E. Tward, M. Petach): Traveling-wave thermoacoustic electric generator, APL 85, 1085 (2004): a thermoacoustic-Stirling engine driving linear alternators, 18 % heat to electricity — web — journal article; cited [verify license at link] — https://doi.org/10.1063/1.1781739\n- Applied Energy (Z. Wu, G. Yu, L. Zhang, W. Dai, E. Luo): Development of a 3 kW double-acting thermoacoustic Stirling electric generator, 136, 866-872 (2014): three engines and three linear alternators in a loop, 5 MPa helium, 86 Hz, 1.57 kW electric, 16.8 % — web — journal article; cited [verify license at link] — https://doi.org/10.1016/j.apenergy.2014.04.105\n- G. W. Swift (Acoustical Society of America / LANL): Thermoacoustics: A Unifying Perspective for Some Engines and Refrigerators (Rott's equations, the energy equation, screen relations; the method behind DeltaEC) — web, book — cited [verify license at link] — https://www.lanl.gov/org/ddste/aldps/materials-physics-applications/condensed-matter-magnet-science/thermoacoustics/\n- J. Thermophysics and Heat Transfer (G. W. Swift, W. C. Ward): Simple harmonic analysis of regenerators, 10(4), 652-662 (1996): stacked-screen friction c1(φ) = 1268 − 3545φ + 2544φ² — web — journal article; cited [verify license at link] — https://doi.org/10.2514/3.842\n- Steel & O'Brien: Clamp ratings (clamp + elastomer gasket assembly): 2 in single-pin 450 psi at 70 °F / 300 psi at 250 °F; high-pressure bolted 1000 / 800 psi — PDF — manufacturer's rating sheet; numbers cited — https://www.steelobrien.com/wp-content/uploads/2020/06/SOB-Clamp-Ratings.pdf\n- NIST Chemistry WebBook: Thermophysical properties of fluid systems (helium, air): viscosity and conductivity used for the model's fits — web — US Government data — https://webbook.nist.gov/chemistry/fluid/\n- Long Earth Society: Engine builds — web, video — LES site — https://longearthsociety.com/engineering/\n\nXem Studio scan: not planned; the official CAD above covers it.\nAPI: https://xemstudio.com/api/geometry?object=list-ta-twin-piston-2in\n",
 "sources": [
  {
   "publisher": "Nature (S. Backhaus, G. W. Swift)",
   "title": "A thermoacoustic Stirling heat engine, Nature 399, 335-338 (1999)",
   "url": "https://doi.org/10.1038/20624",
   "formats": [
    "web"
   ],
   "license": "journal article; cited",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "J. Acoust. Soc. Am. (S. Backhaus, G. W. Swift)",
   "title": "A thermoacoustic-Stirling heat engine: detailed study, JASA 107(6), 3148 (2000): torus with inertance and compliance, thermal buffer tube, jet pump against Gedeon streaming",
   "url": "https://doi.org/10.1121/1.429343",
   "formats": [
    "web"
   ],
   "license": "journal article; cited",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "Appl. Phys. Lett. (S. Backhaus, E. Tward, M. Petach)",
   "title": "Traveling-wave thermoacoustic electric generator, APL 85, 1085 (2004): a thermoacoustic-Stirling engine driving linear alternators, 18 % heat to electricity",
   "url": "https://doi.org/10.1063/1.1781739",
   "formats": [
    "web"
   ],
   "license": "journal article; cited",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "Applied Energy (Z. Wu, G. Yu, L. Zhang, W. Dai, E. Luo)",
   "title": "Development of a 3 kW double-acting thermoacoustic Stirling electric generator, 136, 866-872 (2014): three engines and three linear alternators in a loop, 5 MPa helium, 86 Hz, 1.57 kW electric, 16.8 %",
   "url": "https://doi.org/10.1016/j.apenergy.2014.04.105",
   "formats": [
    "web"
   ],
   "license": "journal article; cited",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "G. W. Swift (Acoustical Society of America / LANL)",
   "title": "Thermoacoustics: A Unifying Perspective for Some Engines and Refrigerators (Rott's equations, the energy equation, screen relations; the method behind DeltaEC)",
   "url": "https://www.lanl.gov/org/ddste/aldps/materials-physics-applications/condensed-matter-magnet-science/thermoacoustics/",
   "formats": [
    "web",
    "book"
   ],
   "license": "cited",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "J. Thermophysics and Heat Transfer (G. W. Swift, W. C. Ward)",
   "title": "Simple harmonic analysis of regenerators, 10(4), 652-662 (1996): stacked-screen friction c1(φ) = 1268 − 3545φ + 2544φ²",
   "url": "https://doi.org/10.2514/3.842",
   "formats": [
    "web"
   ],
   "license": "journal article; cited",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "Steel & O'Brien",
   "title": "Clamp ratings (clamp + elastomer gasket assembly): 2 in single-pin 450 psi at 70 °F / 300 psi at 250 °F; high-pressure bolted 1000 / 800 psi",
   "url": "https://www.steelobrien.com/wp-content/uploads/2020/06/SOB-Clamp-Ratings.pdf",
   "formats": [
    "PDF"
   ],
   "license": "manufacturer's rating sheet; numbers cited",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "NIST Chemistry WebBook",
   "title": "Thermophysical properties of fluid systems (helium, air): viscosity and conductivity used for the model's fits",
   "url": "https://webbook.nist.gov/chemistry/fluid/",
   "formats": [
    "web"
   ],
   "license": "US Government data",
   "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": "not-scanned",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "list-ta-ring-3x2in",
  "thermoacoustic-jet-pump",
  "free-piston-mover-2in",
  "canned-linear-alternator-stator-2in",
  "tube-hanger-post",
  "list-ta-loop-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": [],
 "faq": [
  {
   "q": "How much electricity does it make?",
   "a": "About 9 W in the model at 20 bar helium and 550 °C."
  },
  {
   "q": "Does it run in air or at 1 bar?",
   "a": "Not at a torch's temperature in my model: this layout needs pressurised helium."
  },
  {
   "q": "Why two pistons?",
   "a": "Twice the piston area at the junction, and opposed so the engine does not shake."
  }
 ],
 "files_license": null,
 "offers": [],
 "markdown": "https://xemstudio.com/objects/list-ta-twin-piston-2in/index.md"
}