2208 gimbal motor: outside envelope and mounting holes (Ø27.5 × 23, base M3 on 19 × 16, rotor M2 on 12 × 12) — dimension sheet Source: Xem Studio, https://xemstudio.com/objects/gimbal-motor-2208-envelope/ (CC BY 4.0) 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 Catalog version: 2026-10-20 Sizes: see table below - 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. motor can_mm KV R_ohm fits ratio E_open_V_at_900 W_out_at_4W W_out_at_8W V_at_8W 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 14.0 T-Motor GB2208 KV128 (gimbal) Ø27.5 × 23 128 14.4 yes 1.00 7.0 past matched load past matched load iPower GM2804 (gimbal) Ø35 × 15 168 (from no-load rpm) 9.0 yes 1.83 9.8 2.47 past matched load iPower GM2804 (gimbal) Ø35 × 15 168 (from no-load rpm) 9.0 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 5.0 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 Files elsewhere (not hosted by Xem Studio; license as stated by the publisher): - 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 - 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 - 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 - 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 - 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 - 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/ - 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/ - Long Earth Society: Engine builds — web, video — LES site — https://longearthsociety.com/engineering/ Free files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/gimbal-motor-2208-envelope/index.json API: https://xemstudio.com/api/geometry?object=gimbal-motor-2208-envelope