{
 "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-back-iron-sleeve",
 "name": "Linear alternator back-iron sleeve Ø60.5 × Ø52.5 × 30",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Free-piston",
 "year": null,
 "question": "What size is the back iron of the linear alternator?",
 "tags": [
  "linear alternator",
  "back iron",
  "sleeve",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "linear alternator back iron",
  "back iron sleeve size",
  "alternator flux sleeve"
 ],
 "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/linear-alternator-back-iron-sleeve/",
 "sheet_txt": "https://xemstudio.com/objects/linear-alternator-back-iron-sleeve/sheet.txt",
 "sheet": {
  "basis": "Tube at the sizes in the generator: OD 60.5, bore 52.5 (the bobbin flange OD), length 30 (the bobbin length)",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "The outer flux return of the alternator: a tube Ø60.5 × Ø52.5 bore × 30 long.",
   "The bobbin slides into its bore (Ø52.5, fit: slide) and it sits in the housing's Ø60.5 pocket (fit: socket) on a 2 mm ledge, held down by the cap ring.",
   "The magnetic gap from magnet face to the sleeve is 8.8 mm."
  ],
  "table": {
   "columns": [
    "parameter",
    "value"
   ],
   "rows": [
    [
     "outside",
     60.5
    ],
    [
     "bore",
     52.5
    ],
    [
     "length",
     30
    ]
   ]
  }
 },
 "sheet_text": "Linear alternator back-iron sleeve Ø60.5 × Ø52.5 × 30 — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/linear-alternator-back-iron-sleeve/  (CC BY 4.0)\nBasis: Tube at the sizes in the generator: OD 60.5, bore 52.5 (the bobbin flange OD), length 30 (the bobbin length)\nCatalog version: 2026-10-20\n\nSizes: see table below\n- The outer flux return of the alternator: a tube Ø60.5 × Ø52.5 bore × 30 long.\n- The bobbin slides into its bore (Ø52.5, fit: slide) and it sits in the housing's Ø60.5 pocket (fit: socket) on a 2 mm ledge, held down by the cap ring.\n- The magnetic gap from magnet face to the sleeve is 8.8 mm.\n\nparameter  value\noutside  60.5\nbore  52.5\nlength  30\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, 1 parts): https://xemstudio.com/files/hardware/linear-alternator-back-iron-sleeve/index.json\nAPI: https://xemstudio.com/api/geometry?object=linear-alternator-back-iron-sleeve\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-bobbin",
  "linear-alternator-housing",
  "schedule-40-pipe"
 ],
 "fits": [
  {
   "role": "Goes in or on",
   "items": [
    {
     "slug": "linear-alternator-housing",
     "why": "in the Ø60.5 pocket"
    }
   ]
  },
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "linear-alternator-bobbin",
     "why": "bobbin in the Ø52.5 bore"
    },
    {
     "slug": "linear-alternator-cap-ring",
     "why": "held down by the cap ring"
    }
   ]
  },
  {
   "role": "Alternatives",
   "items": [
    {
     "slug": "schedule-40-pipe",
     "why": "NPS 2 Sch 40 pipe has a 52.5 bore"
    }
   ]
  }
 ],
 "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 in the housing",
   "exact": "Ø60.5",
   "mates": "housing pocket",
   "fit": "socket",
   "files": "alt-back-iron-"
  }
 ],
 "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": "What does the back-iron sleeve do?",
   "a": "It closes the magnets' flux outside the coils so the flux crosses the windings."
  },
  {
   "q": "What size is the back-iron sleeve?",
   "a": "Ø60.5 outside, Ø52.5 bore, 30 long."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "alt-back-iron-sleeve",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/linear-alternator-kit/alt-back-iron-sleeve.step",
   "stl": "https://xemstudio.com/files/hardware/linear-alternator-kit/alt-back-iron-sleeve.stl",
   "note": "back-iron sleeve Ø60.5 × Ø52.5 × 30: closes the magnet flux outside the coils; the bobbin slides in, the sleeve sits in the housing"
  }
 ],
 "markdown": "https://xemstudio.com/objects/linear-alternator-back-iron-sleeve/index.md"
}