{
 "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": "tri-clamp-generator-step-up-gears",
 "name": "Step-up gears for a generator inside a 2 in tri-clamp cross: 42 : 15, module 1",
 "kind": "hardware",
 "category": "Hardware",
 "group": "Stirling & thermoacoustic",
 "year": null,
 "question": "How do I speed up a small generator from a Stirling crankshaft inside a 2 inch tri-clamp cross?",
 "tags": [
  "gear",
  "spur gear",
  "step-up",
  "generator",
  "module 1",
  "tri-clamp",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "stirling generator gear ratio",
  "step up gear crankshaft generator",
  "42 tooth module 1 gear 3 mm bore",
  "gimbal motor pinion adaptor"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 3,
 "url": "https://xemstudio.com/objects/tri-clamp-generator-step-up-gears/",
 "sheet_txt": "https://xemstudio.com/objects/tri-clamp-generator-step-up-gears/sheet.txt",
 "sheet": {
  "basis": "ISO 53 basic rack (20°, addendum 1 m, dedendum 1.25 m), involute flanks as the spur gears on this site; centre distance m (z1 + z2) / 2; tooth counts set by the room in the cross; rotor-top holes from the 2208 listing",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "The crank gear (42 teeth, tip Ø44) sits on the −X crankshaft beside the crank, in place of one flywheel disc and just as heavy; the 15-tooth pinion turns with the motor's rotor. Centre distance 28.5 mm, ratio 2.8 : 1.",
   "The pinion rides on an adaptor: a Ø18 × 2 flange bolted to the rotor top with four M2 × 4 (their heads on the flange's outer face) and a Ø6 stub through the pinion, which an M3 grub holds. The rotor's holes sit at r 6, inside the pinion's teeth, so the pinion cannot be bolted on directly.",
   "Why 2.8 and not more: the motor's Ø27.5 can lies over the crank, so its axis has to be at least 13 + 13.75 mm above the crankshaft (the crank's con-rod eyes sweep R 13), and the crank gear has to turn inside the Ø47.5 bore. 42 : 15 at module 1 puts the can 1.75 mm clear of the crank and the gear tip 1.75 mm inside the bore.",
   "Both gears are drawn at exact size with no backlash; their teeth are a mating feature (see Mating features)."
  ],
  "table": {
   "columns": [
    "part",
    "teeth",
    "pitch_dia_mm",
    "tip_dia_mm",
    "width_mm",
    "bore_mm"
   ],
   "rows": [
    [
     "crank gear",
     42,
     42,
     44,
     12,
     3
    ],
    [
     "pinion",
     15,
     15,
     17,
     10,
     6
    ],
    [
     "adaptor",
     "",
     "",
     18,
     14,
     ""
    ]
   ]
  }
 },
 "sheet_text": "Step-up gears for a generator inside a 2 in tri-clamp cross: 42 : 15, module 1 — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/tri-clamp-generator-step-up-gears/  (CC BY 4.0)\nBasis: ISO 53 basic rack (20°, addendum 1 m, dedendum 1.25 m), involute flanks as the spur gears on this site; centre distance m (z1 + z2) / 2; tooth counts set by the room in the cross; rotor-top holes from the 2208 listing\nCatalog version: 2026-10-20\n\nSizes: see table below\n- The crank gear (42 teeth, tip Ø44) sits on the −X crankshaft beside the crank, in place of one flywheel disc and just as heavy; the 15-tooth pinion turns with the motor's rotor. Centre distance 28.5 mm, ratio 2.8 : 1.\n- The pinion rides on an adaptor: a Ø18 × 2 flange bolted to the rotor top with four M2 × 4 (their heads on the flange's outer face) and a Ø6 stub through the pinion, which an M3 grub holds. The rotor's holes sit at r 6, inside the pinion's teeth, so the pinion cannot be bolted on directly.\n- Why 2.8 and not more: the motor's Ø27.5 can lies over the crank, so its axis has to be at least 13 + 13.75 mm above the crankshaft (the crank's con-rod eyes sweep R 13), and the crank gear has to turn inside the Ø47.5 bore. 42 : 15 at module 1 puts the can 1.75 mm clear of the crank and the gear tip 1.75 mm inside the bore.\n- Both gears are drawn at exact size with no backlash; their teeth are a mating feature (see Mating features).\n\npart  teeth  pitch_dia_mm  tip_dia_mm  width_mm  bore_mm\ncrank gear  42  42.0  44.0  12.0  3.0\npinion  15  15.0  17.0  10.0  6.0\nadaptor      18.0  14.0  \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), as the involute spur gears on this site — standard — dimensions are facts [verify license at link] — https://www.iso.org/standard/22952.html\n- GetFPV (product listing): Tiger GB2208-80 gimbal motor: 27.5 × 23, 4.5 hollow shaft, stator 4-M3 on 19 × 16, rotor 4-M2 on 12 × 12 — web — vendor page; dimensions are facts [verify license at link] — https://www.getfpv.com/tiger-gb2208-80-brushless-gimbal-motor-hollow-shaft.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, 3 parts): https://xemstudio.com/files/hardware/tri-clamp-generator-step-up-gears/index.json\nAPI: https://xemstudio.com/api/geometry?object=tri-clamp-generator-step-up-gears\n",
 "sources": [
  {
   "publisher": "ISO",
   "title": "ISO 53 cylindrical gears, standard basic rack (20°, addendum 1 m, dedendum 1.25 m), as the involute spur gears on this site",
   "url": "https://www.iso.org/standard/22952.html",
   "formats": [
    "standard"
   ],
   "license": "dimensions are facts",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "GetFPV (product listing)",
   "title": "Tiger GB2208-80 gimbal motor: 27.5 × 23, 4.5 hollow shaft, stator 4-M3 on 19 × 16, rotor 4-M2 on 12 × 12",
   "url": "https://www.getfpv.com/tiger-gb2208-80-brushless-gimbal-motor-hollow-shaft.html",
   "formats": [
    "web"
   ],
   "license": "vendor page; dimensions 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": [
  "gimbal-motor-2208-envelope",
  "spur-gears-involute",
  "tri-clamp-crankcase-flywheel",
  "tri-clamp-motor-mount-plate",
  "list-tri-clamp-sealed-diaphragm-generator"
 ],
 "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": "teeth",
   "exact": "module 1, 20°, 42 T and 15 T at 28.5 centre distance, no backlash",
   "mates": "each other",
   "fit": "designed",
   "files": "all"
  },
  {
   "feature": "crank-gear bore",
   "exact": "Ø3",
   "mates": "Ø3 crankshaft (M3 grub, radial from the rim)",
   "fit": "slide",
   "files": "crank-gear-"
  },
  {
   "feature": "pinion bore",
   "exact": "Ø6",
   "mates": "adaptor stub Ø6 (M3 grub)",
   "fit": "slide",
   "files": "pinion-m1-"
  },
  {
   "feature": "adaptor stub",
   "exact": "Ø6",
   "mates": "pinion bore",
   "fit": "slide",
   "files": "pinion-adaptor-"
  },
  {
   "feature": "adaptor flange holes",
   "exact": "4 × Ø2.4 on the 12 / 12 pattern",
   "mates": "shcs-m2x4 into the motor rotor top",
   "fit": "designed",
   "files": "pinion-adaptor-"
  },
  {
   "feature": "grub holes",
   "exact": "Ø2.5 (M3 tapped)",
   "mates": "set-m3x10 (gear), set-m3x3 (pinion)",
   "fit": "designed",
   "files": "crank-gear-"
  },
  {
   "feature": "grub hole",
   "exact": "Ø2.5 (M3 tapped)",
   "mates": "set-m3x3 onto the adaptor stub (ends at r 6, inside the r 6.25 root)",
   "fit": "designed",
   "files": "pinion-m1-"
  }
 ],
 "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 ratio, and why not more?",
   "a": "2.8 : 1. The motor can has to clear the crank and the gear has to fit the 2 in bore; that sets the centre distance at 28.5 mm."
  },
  {
   "q": "How much do the gears lose?",
   "a": "A single spur mesh like this loses roughly 1 to 3 % of the power through it; the estimate on the build list uses that range."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "crank-gear-m1-42t-b3",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-generator-step-up-gears/crank-gear-m1-42t-b3.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-generator-step-up-gears/crank-gear-m1-42t-b3.stl",
   "note": "crank gear: module 1, 42 teeth, 20° (pitch Ø42, tip Ø44), 12 wide, Ø3 bore, radial M3 tapped hole (Ø2.5) at mid-width"
  },
  {
   "file": "pinion-m1-15t-b6",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-generator-step-up-gears/pinion-m1-15t-b6.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-generator-step-up-gears/pinion-m1-15t-b6.stl",
   "note": "pinion: module 1, 15 teeth, 20° (pitch Ø15, tip Ø17), 10 wide, Ø6 bore, radial M3 tapped hole (Ø2.5)"
  },
  {
   "file": "pinion-adaptor-2208",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-generator-step-up-gears/pinion-adaptor-2208.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-generator-step-up-gears/pinion-adaptor-2208.stl",
   "note": "pinion adaptor: flange Ø18 × 2 with 4 × Ø2.4 on the 12 / 12 rotor pattern, Ø6 stub 12 long"
  }
 ],
 "markdown": "https://xemstudio.com/objects/tri-clamp-generator-step-up-gears/index.md"
}