{
 "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": "coil-bobbin",
 "name": "Coil bobbin Ø10 core × 8 mm, Ø13 flanges",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Generators & instruments",
 "year": null,
 "question": "What size coil bobbin for a small axial flux generator?",
 "tags": [
  "bobbin",
  "coil",
  "winding",
  "generator",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "coil bobbin stl",
  "small coil former",
  "bobbin 13mm",
  "generator coil bobbin",
  "axial flux coil"
 ],
 "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/coil-bobbin/",
 "sheet_txt": "https://xemstudio.com/objects/coil-bobbin/sheet.txt",
 "sheet": {
  "basis": "Bobbin sized to the stator pocket: Ø13 flanges, Ø10 core, 8 long, wire slot in one flange",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "The bobbin has a hollow Ø10 core (0.5 mm wall) 8 mm long, closed by two Ø13 × 0.8 mm flanges.",
   "A 1.2 mm slot across one flange lets the start of the winding out.",
   "The winding window is 1.5 mm deep (Ø10 to Ø13) and 6.4 mm long between the flanges.",
   "The Ø13 flanges slide into the Ø13 pockets of the axial-flux stator."
  ],
  "table": {
   "columns": [
    "feature",
    "size_mm"
   ],
   "rows": [
    [
     "core",
     "Ø10 × 8 (Ø9 hollow)"
    ],
    [
     "flanges",
     "Ø13 × 0.8"
    ],
    [
     "winding window",
     "1.5 deep × 6.4 long"
    ],
    [
     "wire slot",
     "1.2 wide"
    ]
   ]
  }
 },
 "sheet_text": "Coil bobbin Ø10 core × 8 mm, Ø13 flanges — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/coil-bobbin/  (CC BY 4.0)\nBasis: Bobbin sized to the stator pocket: Ø13 flanges, Ø10 core, 8 long, wire slot in one flange\nCatalog version: 2026-10-20\n\nSizes: see table below\n- The bobbin has a hollow Ø10 core (0.5 mm wall) 8 mm long, closed by two Ø13 × 0.8 mm flanges.\n- A 1.2 mm slot across one flange lets the start of the winding out.\n- The winding window is 1.5 mm deep (Ø10 to Ø13) and 6.4 mm long between the flanges.\n- The Ø13 flanges slide into the Ø13 pockets of the axial-flux stator.\n\nfeature  size_mm\ncore  Ø10 × 8 (Ø9 hollow)\nflanges  Ø13 × 0.8\nwinding window  1.5 deep × 6.4 long\nwire slot  1.2 wide\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Wikipedia: Axial flux motor — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Axial_flux_motor\n- Wikipedia: Alternator — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Alternator\n- Hugh Piggott: A Wind Turbine Recipe Book (axial-flux alternator design) — web, PDF — Author's site [verify license at link] — http://scoraigwind.co.uk/\n- Long Earth Society: Engine and rig 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/coil-bobbin/index.json\nAPI: https://xemstudio.com/api/geometry?object=coil-bobbin\n",
 "sources": [
  {
   "publisher": "Wikipedia",
   "title": "Axial flux motor",
   "url": "https://en.wikipedia.org/wiki/Axial_flux_motor",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wikipedia",
   "title": "Alternator",
   "url": "https://en.wikipedia.org/wiki/Alternator",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Hugh Piggott",
   "title": "A Wind Turbine Recipe Book (axial-flux alternator design)",
   "url": "http://scoraigwind.co.uk/",
   "formats": [
    "web",
    "PDF"
   ],
   "license": "Author's site",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "Long Earth Society",
   "title": "Engine and rig 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": [
  "axial-flux-stator",
  "axial-flux-rotor"
 ],
 "fits": [
  {
   "role": "Goes in or on",
   "items": [
    {
     "slug": "axial-flux-stator",
     "why": "Ø13 flanges in the Ø13 coil pockets (slide)"
    }
   ]
  },
  {
   "role": "Also needed",
   "items": [
    {
     "slug": "axial-flux-rotor",
     "why": "magnets pass over the coil faces"
    }
   ]
  }
 ],
 "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": "bobbin flanges",
   "exact": "Ø20",
   "mates": "stator coil pocket Ø20",
   "fit": "slide",
   "files": "coil-bobbin-"
  }
 ],
 "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 is the winding space on the bobbin?",
   "a": "1.5 mm radially (Ø10 core to Ø13 flange) by 6.4 mm between the flanges."
  },
  {
   "q": "Does the bobbin fit the stator?",
   "a": "Yes: its Ø13 flanges match the Ø13 coil pockets (slide, see Mating features)."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "coil-bobbin-10x8",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/axial-flux-generator-kit/coil-bobbin-10x8.step",
   "stl": "https://xemstudio.com/files/hardware/axial-flux-generator-kit/coil-bobbin-10x8.stl",
   "note": "coil bobbin Ø10 core (Ø7 bore) × 8 long = the stator thickness, Ø20 × 0.8 flanges, winding window 5 radial × 6.4 axial (32 mm²), 1.2 mm lead slot in one flange"
  }
 ],
 "markdown": "https://xemstudio.com/objects/coil-bobbin/index.md"
}