{
 "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": "linear-alternator-housing",
 "name": "Linear alternator housing for Ø80 and Ø100 flexures (2 in / 3 in)",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Free-piston",
 "year": null,
 "question": "What housing holds the linear alternator stator on a free-piston engine?",
 "tags": [
  "linear alternator",
  "housing",
  "stator",
  "free piston",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "linear alternator housing",
  "free piston alternator mount",
  "alternator stator housing stl"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 2,
 "url": "https://xemstudio.com/objects/linear-alternator-housing/",
 "sheet_txt": "https://xemstudio.com/objects/linear-alternator-housing/sheet.txt",
 "sheet": {
  "basis": "Rim screw circle of the flexure head (R35.2 for Ø80, R44 for Ø100 flexures); sleeve pocket at Ø60.5; M3 clearance Ø3.4",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "The stator body: a Ø63.7 barrel 36 tall between a base flange and a top flange (Ø96 for the 2 in, Ø116 for the 3 in), each 4 thick.",
   "From the top, a Ø60.5 pocket (fit: socket) takes the back-iron sleeve on a 2 mm ledge; a Ø40 passage lets the Ø35 mover through without contact; a 2.5 × 3 slot lets the leads out.",
   "3 × Ø3.4 holes on the flexure head's rim circle (R35.2 or R44) bolt it to standoffs above flexure stack A; the coil centre sits 21 mm above its underside."
  ],
  "table": {
   "columns": [
    "file",
    "flexure",
    "flanges",
    "rim circle",
    "height",
    "sleeve pocket",
    "mover passage"
   ],
   "rows": [
    [
     "alt-housing-2in-flex80",
     "Ø80 (2 in)",
     "Ø96 × 4",
     "R35.2",
     36,
     60.5,
     40
    ],
    [
     "alt-housing-3in-flex100",
     "Ø100 (3 in)",
     "Ø116 × 4",
     "R44",
     36,
     60.5,
     40
    ]
   ]
  }
 },
 "sheet_text": "Linear alternator housing for Ø80 and Ø100 flexures (2 in / 3 in) — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/linear-alternator-housing/  (CC BY 4.0)\nBasis: Rim screw circle of the flexure head (R35.2 for Ø80, R44 for Ø100 flexures); sleeve pocket at Ø60.5; M3 clearance Ø3.4\nCatalog version: 2026-10-20\n\nSizes: see table below\n- The stator body: a Ø63.7 barrel 36 tall between a base flange and a top flange (Ø96 for the 2 in, Ø116 for the 3 in), each 4 thick.\n- From the top, a Ø60.5 pocket (fit: socket) takes the back-iron sleeve on a 2 mm ledge; a Ø40 passage lets the Ø35 mover through without contact; a 2.5 × 3 slot lets the leads out.\n- 3 × Ø3.4 holes on the flexure head's rim circle (R35.2 or R44) bolt it to standoffs above flexure stack A; the coil centre sits 21 mm above its underside.\n\nfile  flexure  flanges  rim circle  height  sleeve pocket  mover passage\nalt-housing-2in-flex80  Ø80 (2 in)  Ø96 × 4  R35.2  36  60.5  40\nalt-housing-3in-flex100  Ø100 (3 in)  Ø116 × 4  R44  36  60.5  40\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- NASA (NTRS, public domain): Linear alternator design for free-piston Stirling convertors (2005) — PDF — US Government work, public domain — https://ntrs.nasa.gov/search?q=20050182934\n- NASA (NTRS, public domain): Sunpower/NASA 80 We free-piston Stirling convertor (2002) — PDF — US Government work, public domain — https://ntrs.nasa.gov/search?q=20020047256\n- Wikipedia: Linear alternator — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Linear_alternator\n- Wikipedia: Free-piston engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Free-piston_engine\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, 2 parts): https://xemstudio.com/files/hardware/linear-alternator-housing/index.json\nAPI: https://xemstudio.com/api/geometry?object=linear-alternator-housing\n",
 "sources": [
  {
   "publisher": "NASA (NTRS, public domain)",
   "title": "Linear alternator design for free-piston Stirling convertors (2005)",
   "url": "https://ntrs.nasa.gov/search?q=20050182934",
   "formats": [
    "PDF"
   ],
   "license": "US Government work, public domain",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "NASA (NTRS, public domain)",
   "title": "Sunpower/NASA 80 We free-piston Stirling convertor (2002)",
   "url": "https://ntrs.nasa.gov/search?q=20020047256",
   "formats": [
    "PDF"
   ],
   "license": "US Government work, public domain",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wikipedia",
   "title": "Linear alternator",
   "url": "https://en.wikipedia.org/wiki/Linear_alternator",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wikipedia",
   "title": "Free-piston engine",
   "url": "https://en.wikipedia.org/wiki/Free-piston_engine",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "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": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "linear-alternator-cap-ring",
  "linear-alternator-back-iron-sleeve",
  "tri-clamp-flexure-head",
  "threaded-standoffs-metric",
  "list-free-piston-2in"
 ],
 "fits": [
  {
   "role": "Goes in or on",
   "items": [
    {
     "slug": "tri-clamp-flexure-head",
     "why": "on standoffs on the flexure head's rim screws"
    }
   ]
  },
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "linear-alternator-back-iron-sleeve",
     "why": "sleeve in the Ø60.5 pocket"
    },
    {
     "slug": "linear-alternator-cap-ring",
     "why": "cap on the top flange"
    }
   ]
  },
  {
   "role": "Also needed",
   "items": [
    {
     "slug": "threaded-standoffs-metric",
     "why": "M3 × 30 standoffs"
    },
    {
     "slug": "socket-head-cap-screws-metric",
     "why": "M3 × 10 / 12 / 16"
    }
   ]
  }
 ],
 "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": "sleeve pocket",
   "exact": "Ø60.5",
   "mates": "back-iron sleeve OD",
   "fit": "socket",
   "files": "alt-housing-"
  },
  {
   "feature": "housing rim holes",
   "exact": "Ø3.4",
   "mates": "M3 screw clearance",
   "fit": "designed",
   "files": "alt-housing-"
  },
  {
   "feature": "mover passage",
   "exact": "Ø40",
   "mates": "Ø35 mover (no contact)",
   "fit": "designed",
   "files": "alt-housing-"
  }
 ],
 "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": "How does the linear alternator mount on the free-piston engine?",
   "a": "Its base flange sits on 3 × M3 × 30 standoffs above flexure stack A, on the flexure head's rim circle (R35.2 for 2 in)."
  },
  {
   "q": "Does it fit a 1.5 in engine?",
   "a": "No: the Ø60 flexures of the 1.5 in engine are too small for this stator."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "alt-housing-2in-flex80",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/linear-alternator-kit/alt-housing-2in-flex80.step",
   "stl": "https://xemstudio.com/files/hardware/linear-alternator-kit/alt-housing-2in-flex80.stl",
   "note": "2in housing: Ø96 base and top flanges with 3 × M3 on the R35.2 rim circle (same as the flexure head), pocket for the back-iron sleeve on a 2 mm ledge, Ø40 mover passage, lead slot; 36 tall"
  },
  {
   "file": "alt-housing-3in-flex100",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/linear-alternator-kit/alt-housing-3in-flex100.step",
   "stl": "https://xemstudio.com/files/hardware/linear-alternator-kit/alt-housing-3in-flex100.stl",
   "note": "3in housing: Ø116 base and top flanges with 3 × M3 on the R44 rim circle (same as the flexure head), pocket for the back-iron sleeve on a 2 mm ledge, Ø40 mover passage, lead slot; 36 tall"
  }
 ],
 "markdown": "https://xemstudio.com/objects/linear-alternator-housing/index.md"
}