{
 "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-free-piston-2in",
 "name": "Build list: Free-piston Stirling, 2 in tri-clamp (flexure-suspended)",
 "kind": "list",
 "category": "Stirling engines",
 "group": "Guide",
 "year": null,
 "question": "What parts do I need to build a free-piston Stirling, 2 in tri-clamp?",
 "tags": [
  "list",
  "build",
  "stirling",
  "free piston",
  "flexure",
  "long earth society"
 ],
 "aliases": [
  "free piston stirling parts list",
  "fpse build",
  "flexure stirling engine parts"
 ],
 "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-free-piston-2in/",
 "sheet_txt": "https://xemstudio.com/objects/list-free-piston-2in/sheet.txt",
 "sheet": {
  "basis": "Every printed part is a free file on this site.",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "No crank: displacer rod through the piston, both hung on spiral flexure stacks; the demonstrator NASA's convertors grew from.",
   "Numbers: Ø46 × 90 displacer · Ø47.3 piston · Ø80 flexures, 2 stacks · two-row moving-magnet alternator · 10–20 Hz"
  ],
  "table": {
   "columns": [
    "subsystem",
    "object",
    "parts",
    "qty",
    "note"
   ],
   "rows": [
    [
     "Hot end",
     "tri-clamp-cups",
     "cup-2in-90",
     1,
     "printed for a warm-plate demonstrator."
    ],
    [
     "Cylinder",
     "tri-clamp-spool",
     "tc-spool-2in-6in",
     1,
     "16 ga, 47.5 bore"
    ],
    [
     "Joints",
     "tri-clamp-end-cap",
     "tc-gasket-2in",
     2,
     "ISO 2852 Type B gaskets on the cold joints"
    ],
    [
     "Clamps",
     "tri-clamp-clamps",
     "clamp-half-2in",
     4,
     "two halves per joint."
    ],
    [
     "Displacer",
     "tri-clamp-displacers-and-heads",
     "displacer-shell-2in-90, displacer-cap-2in",
     1,
     "Ø3 rod on the cap's M3 grub"
    ],
    [
     "Power piston",
     "tri-clamp-power-pistons",
     "piston-2in-f020-rod, lapping-handle-2in",
     1,
     "lap to fit; bushing in the crown"
    ],
    [
     "Piston plug",
     "tri-clamp-free-piston-kit",
     "fp-piston-plug-2in",
     1,
     "carries the 5 mm tube rod"
    ],
    [
     "Wrist dowels",
     "dowel-pins-metric",
     "dowel-3x16",
     2,
     "retain the plug"
    ],
    [
     "Rod bushing",
     "bearing-housings-and-rod-supports",
     "bushing-3x5x6",
     1,
     "no oil"
    ],
    [
     "Rods",
     "brass-tube-ks",
     "brass-5mm",
     1,
     "5 mm K&S tube piston rod"
    ],
    [
     "Displacer rod",
     "stirling-shafts-and-rods",
     "rod-3x200",
     1,
     "through the piston bushing and the tube."
    ],
    [
     "Flexure head",
     "tri-clamp-free-piston-kit",
     "fp-flexure-head-2in",
     1,
     "clamps on the spool's open ferrule"
    ],
    [
     "Flexure ring",
     "tri-clamp-free-piston-kit",
     "fp-flexure-ring-80",
     1,
     "stack B, on standoffs"
    ],
    [
     "Stand",
     "spool-hanger-collars",
     "hanger-2in-tab, hanger-2in-plain",
     1,
     "hangs the engine from a 2020 crossbar over the heat"
    ],
    [
     "Frame rails",
     "t-slot-extrusions",
     "2020-100",
     3,
     "two uprights + crossbar; M5 T-nuts"
    ],
    [
     "Leaves",
     "spiral-flexure-bearings",
     "flexure-80-3arm-w2.5-t2",
     4,
     "2 per stack; alternate spiral hand."
    ],
    [
     "Stack hardware",
     "spiral-flexure-bearings",
     "spacer-80-t2, clamp-plate-80, hub-clamp-80-b5",
     2,
     "one set per stack"
    ],
    [
     "Hub collars",
     "tri-clamp-free-piston-kit",
     "hub-collar-80-b5, hub-collar-80-b3",
     2,
     "two b5 on the tube, two b3 on the displacer rod"
    ],
    [
     "Centring bush",
     "tri-clamp-free-piston-kit",
     "hub-bush-80-b3",
     1,
     "centres stack B's Ø5 hub bores on the Ø3 rod"
    ],
    [
     "Alternator mover",
     "linear-alternator-kit",
     "alt-mover-35-2x8-10x3",
     1,
     "on the 5 mm tube above stack A; centre it in the coils, then grub"
    ],
    [
     "Magnets",
     "neodymium-disc-magnets",
     "magnet-10x3",
     16,
     "N42 Ø10 × 3: row 1 all N out, row 2 all S out (check with a compass)"
    ],
    [
     "Alternator stator",
     "linear-alternator-kit",
     "alt-bobbin-37-2x10, alt-housing-2in-flex80, alt-cap-2in-flex80",
     1,
     "two bays wound opposite ways, in series"
    ],
    [
     "Back iron",
     "linear-alternator-kit",
     "alt-back-iron-sleeve",
     1,
     "the bobbin slides in; sits on the housing ledge"
    ],
    [
     "Coils",
     "linear-alternator-kit",
     "alt-coil-bay",
     2,
     "one per bobbin bay, the second wound the opposite way"
    ],
    [
     "Alternator standoffs",
     "threaded-standoffs-metric",
     "standoff-m3x30",
     3,
     "between stack A and the housing"
    ],
    [
     "Alternator screws",
     "socket-head-cap-screws-metric",
     "shcs-m3x16, shcs-m3x10, shcs-m3x12",
     3,
     "16 up through head + stack A; 10 housing to standoffs; 12 through top flange + cap"
    ],
    [
     "Standoffs",
     "threaded-standoffs-metric",
     "standoff-m3x30",
     6,
     "3 under the alternator housing, 3 above it to the flexure ring"
    ],
    [
     "Fasteners",
     "socket-head-cap-screws-metric",
     "shcs-m3x10",
     12,
     "rims to head and ring"
    ],
    [
     "Heat",
     "tea-light-candles",
     "tea-light-maxi-58x24",
     1,
     "or a hot plate under the cup"
    ]
   ]
  }
 },
 "sheet_text": "Build list: Free-piston Stirling, 2 in tri-clamp (flexure-suspended) — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/list-free-piston-2in/  (CC BY 4.0)\nBasis: Every printed part is a free file on this site.\nCatalog version: 2026-10-20\n\nSizes: see table below\n- No crank: displacer rod through the piston, both hung on spiral flexure stacks; the demonstrator NASA's convertors grew from.\n- Numbers: Ø46 × 90 displacer · Ø47.3 piston · Ø80 flexures, 2 stacks · two-row moving-magnet alternator · 10–20 Hz\n\nsubsystem  object  parts  qty  note\nHot end  tri-clamp-cups  cup-2in-90  1  printed for a warm-plate demonstrator.\nCylinder  tri-clamp-spool  tc-spool-2in-6in  1  16 ga, 47.5 bore\nJoints  tri-clamp-end-cap  tc-gasket-2in  2  ISO 2852 Type B gaskets on the cold joints\nClamps  tri-clamp-clamps  clamp-half-2in  4  two halves per joint.\nDisplacer  tri-clamp-displacers-and-heads  displacer-shell-2in-90, displacer-cap-2in  1  Ø3 rod on the cap's M3 grub\nPower piston  tri-clamp-power-pistons  piston-2in-f020-rod, lapping-handle-2in  1  lap to fit; bushing in the crown\nPiston plug  tri-clamp-free-piston-kit  fp-piston-plug-2in  1  carries the 5 mm tube rod\nWrist dowels  dowel-pins-metric  dowel-3x16  2  retain the plug\nRod bushing  bearing-housings-and-rod-supports  bushing-3x5x6  1  no oil\nRods  brass-tube-ks  brass-5mm  1  5 mm K&S tube piston rod\nDisplacer rod  stirling-shafts-and-rods  rod-3x200  1  through the piston bushing and the tube.\nFlexure head  tri-clamp-free-piston-kit  fp-flexure-head-2in  1  clamps on the spool's open ferrule\nFlexure ring  tri-clamp-free-piston-kit  fp-flexure-ring-80  1  stack B, on standoffs\nStand  spool-hanger-collars  hanger-2in-tab, hanger-2in-plain  1  hangs the engine from a 2020 crossbar over the heat\nFrame rails  t-slot-extrusions  2020-100  3  two uprights + crossbar; M5 T-nuts\nLeaves  spiral-flexure-bearings  flexure-80-3arm-w2.5-t2  4  2 per stack; alternate spiral hand.\nStack hardware  spiral-flexure-bearings  spacer-80-t2, clamp-plate-80, hub-clamp-80-b5  2  one set per stack\nHub collars  tri-clamp-free-piston-kit  hub-collar-80-b5, hub-collar-80-b3  2  two b5 on the tube, two b3 on the displacer rod\nCentring bush  tri-clamp-free-piston-kit  hub-bush-80-b3  1  centres stack B's Ø5 hub bores on the Ø3 rod\nAlternator mover  linear-alternator-kit  alt-mover-35-2x8-10x3  1  on the 5 mm tube above stack A; centre it in the coils, then grub\nMagnets  neodymium-disc-magnets  magnet-10x3  16  N42 Ø10 × 3: row 1 all N out, row 2 all S out (check with a compass)\nAlternator stator  linear-alternator-kit  alt-bobbin-37-2x10, alt-housing-2in-flex80, alt-cap-2in-flex80  1  two bays wound opposite ways, in series\nBack iron  linear-alternator-kit  alt-back-iron-sleeve  1  the bobbin slides in; sits on the housing ledge\nCoils  linear-alternator-kit  alt-coil-bay  2  one per bobbin bay, the second wound the opposite way\nAlternator standoffs  threaded-standoffs-metric  standoff-m3x30  3  between stack A and the housing\nAlternator screws  socket-head-cap-screws-metric  shcs-m3x16, shcs-m3x10, shcs-m3x12  3  16 up through head + stack A; 10 housing to standoffs; 12 through top flange + cap\nStandoffs  threaded-standoffs-metric  standoff-m3x30  6  3 under the alternator housing, 3 above it to the flexure ring\nFasteners  socket-head-cap-screws-metric  shcs-m3x10  12  rims to head and ring\nHeat  tea-light-candles  tea-light-maxi-58x24  1  or a hot plate under the cup\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\nXem Studio scan: not planned; the official CAD above covers it.\nAPI: https://xemstudio.com/api/geometry?object=list-free-piston-2in\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": "not-scanned",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "tri-clamp-cups",
  "tri-clamp-spool",
  "tri-clamp-end-cap",
  "tri-clamp-clamps",
  "tri-clamp-displacers-and-heads",
  "tri-clamp-power-pistons",
  "tri-clamp-free-piston-kit",
  "dowel-pins-metric",
  "bearing-housings-and-rod-supports",
  "brass-tube-ks",
  "stirling-shafts-and-rods",
  "spool-hanger-collars"
 ],
 "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": "What parts do I need to build a Free-piston Stirling, 2 in tri-clamp?",
   "a": "39 parts, every one a free STEP/STL on this site; see the table and the build order on this page."
  },
  {
   "q": "How do I download every STL for this build at once?",
   "a": "The stl-list.txt on this page lists every printed part's STL URL."
  }
 ],
 "files_license": null,
 "offers": [],
 "markdown": "https://xemstudio.com/objects/list-free-piston-2in/index.md"
}