{
 "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": "gimbal-motor-2208-envelope",
 "name": "2208 gimbal motor: outside envelope and mounting holes (Ø27.5 × 23, base M3 on 19 × 16, rotor M2 on 12 × 12)",
 "kind": "hardware",
 "category": "Hardware",
 "group": "Stirling & thermoacoustic",
 "year": null,
 "question": "What are the dimensions and mounting holes of a 2208 brushless gimbal motor, and how much does it make as a generator?",
 "tags": [
  "motor",
  "gimbal motor",
  "outrunner",
  "2208",
  "generator",
  "envelope",
  "tri-clamp",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "2208 gimbal motor dimensions",
  "gb2208 mounting holes",
  "gimbal motor as generator",
  "low kv motor generator",
  "gimbal motor 27.5 mm"
 ],
 "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/gimbal-motor-2208-envelope/",
 "sheet_txt": "https://xemstudio.com/objects/gimbal-motor-2208-envelope/sheet.txt",
 "sheet": {
  "basis": "T-Motor GB2208 KV128: Ø27.5 × 23, KV 128, internal resistance 14.4 Ω, 12N14P (maker's page); Tiger GB2208 listing: 4.5 hollow shaft, stator holes 4-M3 on 19 × 16, rotor holes 4-M2 on 12 × 12; tap depths assumed",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "An envelope, not a model of the motor: the can, the hollow-shaft bore and the base and rotor-top holes at the published sizes. The base is the stator side that bolts down; the rotor top turns and carries what it drives.",
   "Electrical: 128 rpm per volt and 14.4 Ω (published). As a generator on the sealed engine it turns 2.8 times the crank speed through a 42 : 15 gear pair: 19.7 V open circuit at 900 crank rpm (2520 motor rpm).",
   "Why this motor: copper loss in a generator is (T / Km)², with Km = Kt / √R the motor constant; the gearing divides the torque. Of the low-KV motors whose size, KV and resistance are published and that fit the 2 in cross with the gearing that fits there, this one gives the most watts; the table shows the others (4 and 8 W at the crank, 2 % gear loss, drag not included).",
   "The GM4108 would do far better (Km five times higher) but at Ø47 it has no running clearance in a 2 in bore."
  ],
  "table": {
   "columns": [
    "motor",
    "can_mm",
    "KV",
    "R_ohm",
    "fits",
    "ratio",
    "E_open_V_at_900",
    "W_out_at_4W",
    "W_out_at_8W",
    "V_at_8W"
   ],
   "rows": [
    [
     "A2212/13T 1000 KV (2212 drone outrunner)",
     "Ø27.5 × 30",
     "1000",
     0.133,
     "yes",
     "2.80",
     2.5,
     3.6,
     6.55,
     2.1
    ],
    [
     "A2212/13T 1000 KV (2212 drone outrunner)",
     "Ø27.5 × 30",
     "1000",
     0.133,
     "yes",
     "1.00",
     0.9,
     "past matched load",
     "past matched load",
     ""
    ],
    [
     "T-Motor GB2208 KV128 (gimbal)",
     "Ø27.5 × 23",
     "128",
     14.4,
     "yes",
     "2.80",
     19.7,
     3.35,
     5.56,
     14
    ],
    [
     "T-Motor GB2208 KV128 (gimbal)",
     "Ø27.5 × 23",
     "128",
     14.4,
     "yes",
     "1.00",
     7,
     "past matched load",
     "past matched load",
     ""
    ],
    [
     "iPower GM2804 (gimbal)",
     "Ø35 × 15",
     "168 (from no-load rpm)",
     9,
     "yes",
     "1.83",
     9.8,
     2.47,
     "past matched load",
     ""
    ],
    [
     "iPower GM2804 (gimbal)",
     "Ø35 × 15",
     "168 (from no-load rpm)",
     9,
     "yes",
     "1.00",
     5.4,
     "past matched load",
     "past matched load",
     ""
    ],
    [
     "iPower GM3506 (gimbal)",
     "Ø40 × 17.8",
     "141 (from no-load rpm)",
     5.6,
     "yes",
     "1.50",
     9.6,
     2.98,
     4.09,
     5
    ],
    [
     "iPower GM3506 (gimbal)",
     "Ø40 × 17.8",
     "141 (from no-load rpm)",
     5.6,
     "yes",
     "1.00",
     6.4,
     "past matched load",
     "past matched load",
     ""
    ],
    [
     "iPower GM4108H-120T (gimbal)",
     "Ø47 × 22.7",
     "27 (from no-load rpm)",
     11.1,
     "no",
     "1.00",
     33.3,
     3.84,
     7.36,
     30.7
    ]
   ]
  }
 },
 "sheet_text": "2208 gimbal motor: outside envelope and mounting holes (Ø27.5 × 23, base M3 on 19 × 16, rotor M2 on 12 × 12) — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/gimbal-motor-2208-envelope/  (CC BY 4.0)\nBasis: T-Motor GB2208 KV128: Ø27.5 × 23, KV 128, internal resistance 14.4 Ω, 12N14P (maker's page); Tiger GB2208 listing: 4.5 hollow shaft, stator holes 4-M3 on 19 × 16, rotor holes 4-M2 on 12 × 12; tap depths assumed\nCatalog version: 2026-10-20\n\nSizes: see table below\n- An envelope, not a model of the motor: the can, the hollow-shaft bore and the base and rotor-top holes at the published sizes. The base is the stator side that bolts down; the rotor top turns and carries what it drives.\n- Electrical: 128 rpm per volt and 14.4 Ω (published). As a generator on the sealed engine it turns 2.8 times the crank speed through a 42 : 15 gear pair: 19.7 V open circuit at 900 crank rpm (2520 motor rpm).\n- Why this motor: copper loss in a generator is (T / Km)², with Km = Kt / √R the motor constant; the gearing divides the torque. Of the low-KV motors whose size, KV and resistance are published and that fit the 2 in cross with the gearing that fits there, this one gives the most watts; the table shows the others (4 and 8 W at the crank, 2 % gear loss, drag not included).\n- The GM4108 would do far better (Km five times higher) but at Ø47 it has no running clearance in a 2 in bore.\n\nmotor  can_mm  KV  R_ohm  fits  ratio  E_open_V_at_900  W_out_at_4W  W_out_at_8W  V_at_8W\nA2212/13T 1000 KV (2212 drone outrunner)  Ø27.5 × 30  1000  0.133  yes  2.80  2.5  3.6  6.55  2.1\nA2212/13T 1000 KV (2212 drone outrunner)  Ø27.5 × 30  1000  0.133  yes  1.00  0.9  past matched load  past matched load  \nT-Motor GB2208 KV128 (gimbal)  Ø27.5 × 23  128  14.4  yes  2.80  19.7  3.35  5.56  14.0\nT-Motor GB2208 KV128 (gimbal)  Ø27.5 × 23  128  14.4  yes  1.00  7.0  past matched load  past matched load  \niPower GM2804 (gimbal)  Ø35 × 15  168 (from no-load rpm)  9.0  yes  1.83  9.8  2.47  past matched load  \niPower GM2804 (gimbal)  Ø35 × 15  168 (from no-load rpm)  9.0  yes  1.00  5.4  past matched load  past matched load  \niPower GM3506 (gimbal)  Ø40 × 17.8  141 (from no-load rpm)  5.6  yes  1.50  9.6  2.98  4.09  5.0\niPower GM3506 (gimbal)  Ø40 × 17.8  141 (from no-load rpm)  5.6  yes  1.00  6.4  past matched load  past matched load  \niPower GM4108H-120T (gimbal)  Ø47 × 22.7  27 (from no-load rpm)  11.1  no  1.00  33.3  3.84  7.36  30.7\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- T-Motor (maker's store page): GB2208 gimbal motor KV128: Ø27.5 × 23, internal resistance 14.4 Ω, 12N14P, 39.5 g with cable — web — maker page; values are facts [verify license at link] — https://store.tmotor.com/goods-447-GB2208.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- iFlight (maker's shop): iPower GM2804: Ø35 × 15, 9 Ω, no-load speed at 10 V (KV derived) — web — maker page; values are facts [verify license at link] — https://shop.iflight.com/ipower-gm2804-gimbal-motor-pro1153\n- iFlight (maker's shop): iPower GM3506: Ø40 × 17.8, 5.6 Ω, 2149–2375 rpm no-load at 16 V (KV derived), 0.17 A no-load — web — maker page; values are facts [verify license at link] — https://shop.iflight.com/ipower-motor-gm3506-brushless-gimbal-motor-pro967\n- iFlight (maker's shop): iPower GM4108H-120T: Ø47 × 22.7, 11.1 Ω, 513–567 rpm no-load at 20 V (KV derived) — web — maker page; values are facts [verify license at link] — https://shop.iflight.com/ipower-motor-gm4108h-120t-brushless-gimbal-motor-pro217\n- iFuture Technology (product listing): A2212/13T 1000 KV outrunner: Ø27.5 × 30, shaft Ø3.17 × 12, mounting holes M3 on 16 mm × 19 mm, 1000 rpm/V — web — vendor page; dimensions are facts [verify license at link] — https://ifuturetech.org/product/a2212-1000-kv-bldc-brushless-dc-motor-for-drone/\n- Flying Tech (product listing): SunnySky X2212-13 980 KV II: internal resistance 133 mΩ, no-load 0.3 A at 10 V, rotor Ø27.5, body 30, shaft Ø3.175, 12N14P — web — vendor page; values are facts [verify license at link] — https://www.flyingtech.co.uk/product/sunnysky-x2212-13-980kv-ii-2-4s-multirotor-brushless-motor/\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/gimbal-motor-2208-envelope/index.json\nAPI: https://xemstudio.com/api/geometry?object=gimbal-motor-2208-envelope\n",
 "sources": [
  {
   "publisher": "T-Motor (maker's store page)",
   "title": "GB2208 gimbal motor KV128: Ø27.5 × 23, internal resistance 14.4 Ω, 12N14P, 39.5 g with cable",
   "url": "https://store.tmotor.com/goods-447-GB2208.html",
   "formats": [
    "web"
   ],
   "license": "maker page; values 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": "iFlight (maker's shop)",
   "title": "iPower GM2804: Ø35 × 15, 9 Ω, no-load speed at 10 V (KV derived)",
   "url": "https://shop.iflight.com/ipower-gm2804-gimbal-motor-pro1153",
   "formats": [
    "web"
   ],
   "license": "maker page; values are facts",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "iFlight (maker's shop)",
   "title": "iPower GM3506: Ø40 × 17.8, 5.6 Ω, 2149–2375 rpm no-load at 16 V (KV derived), 0.17 A no-load",
   "url": "https://shop.iflight.com/ipower-motor-gm3506-brushless-gimbal-motor-pro967",
   "formats": [
    "web"
   ],
   "license": "maker page; values are facts",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "iFlight (maker's shop)",
   "title": "iPower GM4108H-120T: Ø47 × 22.7, 11.1 Ω, 513–567 rpm no-load at 20 V (KV derived)",
   "url": "https://shop.iflight.com/ipower-motor-gm4108h-120t-brushless-gimbal-motor-pro217",
   "formats": [
    "web"
   ],
   "license": "maker page; values are facts",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "iFuture Technology (product listing)",
   "title": "A2212/13T 1000 KV outrunner: Ø27.5 × 30, shaft Ø3.17 × 12, mounting holes M3 on 16 mm × 19 mm, 1000 rpm/V",
   "url": "https://ifuturetech.org/product/a2212-1000-kv-bldc-brushless-dc-motor-for-drone/",
   "formats": [
    "web"
   ],
   "license": "vendor page; dimensions are facts",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "Flying Tech (product listing)",
   "title": "SunnySky X2212-13 980 KV II: internal resistance 133 mΩ, no-load 0.3 A at 10 V, rotor Ø27.5, body 30, shaft Ø3.175, 12N14P",
   "url": "https://www.flyingtech.co.uk/product/sunnysky-x2212-13-980kv-ii-2-4s-multirotor-brushless-motor/",
   "formats": [
    "web"
   ],
   "license": "vendor 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": [
  "tri-clamp-motor-mount-plate",
  "tri-clamp-generator-step-up-gears",
  "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": "can",
   "exact": "Ø27.5 × 23 (envelope)",
   "mates": "motor-mount face and the crank below (1.75 clear)",
   "fit": "designed",
   "files": "all"
  },
  {
   "feature": "base holes",
   "exact": "4 × M3 (Ø2.5 tap drill, 4 deep): pairs 16 and 19 apart",
   "mates": "csk-m3x6 through the mount face",
   "fit": "designed",
   "files": "all"
  },
  {
   "feature": "rotor-top holes",
   "exact": "4 × M2 (Ø1.6 tap drill, 3 deep): pairs 12 apart",
   "mates": "shcs-m2x4 through the pinion adaptor flange",
   "fit": "designed",
   "files": "all"
  },
  {
   "feature": "hollow shaft",
   "exact": "Ø4.5 bore",
   "mates": "nothing (clear)",
   "fit": "designed",
   "files": "all"
  }
 ],
 "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 are the mounting holes of a 2208 gimbal motor?",
   "a": "Base: four M3, pairs 19 and 16 mm apart. Rotor top: four M2, pairs 12 mm apart (Tiger GB2208 listing)."
  },
  {
   "q": "Is this a CAD model of the motor?",
   "a": "No: it is the space the motor takes and where it bolts, at the published outside sizes."
  },
  {
   "q": "Why not drive it straight from the crank?",
   "a": "At 900 rpm it makes only 7.0 V and its 14.4 Ω winding could deliver at most 0.86 W into a matched load; geared 2.8 : 1 it makes 19.7 V and can take the engine's few watts."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "gimbal-motor-2208-envelope",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/gimbal-motor-2208-envelope/gimbal-motor-2208-envelope.step",
   "stl": "https://xemstudio.com/files/hardware/gimbal-motor-2208-envelope/gimbal-motor-2208-envelope.stl",
   "note": "ENVELOPE, not a motor: 2208 gimbal-class outrunner at its published outside size, can Ø27.5 × 23 with the base (stator mounting face) at z 0 and the rotor top at z 23, Ø4.5 hollow-shaft bore; 4 × Ø2.5 (M3 tap drill, 4 deep, assumed) in the base, pairs 16 and 19 apart; 4 × Ø1.6 (M2 tap drill, 3 deep, assumed) in the rotor top, pairs 12 apart"
  }
 ],
 "markdown": "https://xemstudio.com/objects/gimbal-motor-2208-envelope/index.md"
}