{
 "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": "htd-generator-drive",
 "name": "HTD generator drive: 210 T crank gear and a 2208 bracket (14 : 1)",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Tri-clamp engine parts",
 "year": null,
 "question": "How do I gear a generator to a slow Stirling engine?",
 "tags": [
  "gear",
  "generator",
  "htd",
  "stirling"
 ],
 "aliases": [
  "stirling generator gearing",
  "210 tooth module 1 gear"
 ],
 "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/htd-generator-drive/",
 "sheet_txt": "https://xemstudio.com/objects/htd-generator-drive/sheet.txt",
 "sheet": {
  "basis": "Module 1, 20° involute (ISO 53) as the site's spur gears; the catalog's 15 T pinion, its 2208 adaptor and the 2208 envelope",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "210 : 15 = 14 : 1 at 112.5 centre distance: at 150 rpm the 2208 (KV 128, 14.4 Ω, published) turns 2100 rpm and makes 16.4 V open circuit.",
   "The bracket bolts to the seal cap's outer face with three M4; the motor's base takes four M3 countersunk screws from the bracket's back."
  ],
  "table": {
   "columns": [
    "part",
    "teeth",
    "tip_mm",
    "ratio"
   ],
   "rows": [
    [
     "gear-m1-210t-b12",
     210,
     212,
     14
    ],
    [
     "motor-bracket-2208-3in",
     "",
     "",
     ""
    ]
   ]
  }
 },
 "sheet_text": "HTD generator drive: 210 T crank gear and a 2208 bracket (14 : 1) — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/htd-generator-drive/  (CC BY 4.0)\nBasis: Module 1, 20° involute (ISO 53) as the site's spur gears; the catalog's 15 T pinion, its 2208 adaptor and the 2208 envelope\nCatalog version: 2026-10-20\n\nSizes: see table below\n- 210 : 15 = 14 : 1 at 112.5 centre distance: at 150 rpm the 2208 (KV 128, 14.4 Ω, published) turns 2100 rpm and makes 16.4 V open circuit.\n- The bracket bolts to the seal cap's outer face with three M4; the motor's base takes four M3 countersunk screws from the bracket's back.\n\npart  teeth  tip_mm  ratio\ngear-m1-210t-b12  210  212.0  14.0\nmotor-bracket-2208-3in      \n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- ISO: ISO 53 cylindrical gears, standard basic rack (20°, addendum 1 m, dedendum 1.25 m) — standard — dimensions are facts [verify license at link] — https://www.iso.org/standard/22952.html\n- T-Motor (maker's store page): GB2208 gimbal motor KV128: internal resistance 14.4 Ω — web — maker page; values are facts [verify license at link] — https://store.tmotor.com/goods-447-GB2208.html\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/htd-generator-drive/index.json\nAPI: https://xemstudio.com/api/geometry?object=htd-generator-drive\n",
 "sources": [
  {
   "publisher": "ISO",
   "title": "ISO 53 cylindrical gears, standard basic rack (20°, addendum 1 m, dedendum 1.25 m)",
   "url": "https://www.iso.org/standard/22952.html",
   "formats": [
    "standard"
   ],
   "license": "dimensions are facts",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "T-Motor (maker's store page)",
   "title": "GB2208 gimbal motor KV128: internal resistance 14.4 Ω",
   "url": "https://store.tmotor.com/goods-447-GB2208.html",
   "formats": [
    "web"
   ],
   "license": "maker page; values are facts",
   "license_verified": false,
   "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": [
  "list-htd-10in",
  "tri-clamp-generator-step-up-gears",
  "gimbal-motor-2208-envelope"
 ],
 "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": [
  {
   "feature": "gear bore",
   "exact": "Ø12, M4 grub",
   "mates": "Ø12 shaft",
   "fit": "slide",
   "files": "gear-"
  },
  {
   "feature": "mesh",
   "exact": "module 1, 210 : 15 at 112.5 centres",
   "mates": "pinion-m1-15t-b6",
   "fit": "designed",
   "files": "gear-"
  },
  {
   "feature": "bracket holes",
   "exact": "3 × Ø4.5 on r 30; 4 × Ø3.4 countersunk 90° to Ø6",
   "mates": "shcs-m4x12; csk-m3x8 into the motor base",
   "fit": "designed",
   "files": "motor-bracket-"
  },
  {
   "feature": "shaft hole",
   "exact": "Ø30",
   "mates": "shaft and seal (no contact)",
   "fit": "designed",
   "files": "motor-bracket-"
  }
 ],
 "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": "Why gear up 14 : 1?",
   "a": "A slow engine turns a small generator too slowly to make useful voltage; 14 : 1 puts the 2208 near 2000 rpm."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "gear-m1-210t-b12",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/htd-generator-drive/gear-m1-210t-b12.step",
   "stl": "https://xemstudio.com/files/hardware/htd-generator-drive/gear-m1-210t-b12.stl",
   "note": "crank gear module 1, 210 teeth, 20° (tip Ø212), 10 wide, hub Ø30 × 15, Ø12 bore, M4 radial tapped hole"
  },
  {
   "file": "motor-bracket-2208-3in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/htd-generator-drive/motor-bracket-2208-3in.step",
   "stl": "https://xemstudio.com/files/hardware/htd-generator-drive/motor-bracket-2208-3in.stl",
   "note": "generator bracket 5 thick: Ø76.2 disc on the seal cap (3 × M4 on r 30), arm to the motor 112.5 above the shaft, 2208 base holes countersunk"
  }
 ],
 "markdown": "https://xemstudio.com/objects/htd-generator-drive/index.md"
}