3" Gizmo Ankle Biter

By tehllama on Mar 01, 2019

7  114  0

This build is for two identical 3" Gizmo racers. I think the title 'ankle biter' is extremely appropriate, because I can show up at races and hassle some fast pilots with their 5" setups. Just about the only downside is that these little punks lose when I have midairs, but I'm genuinely shocked I can keep up well enough for that to be a problem.

These are eminent budget racers - got the frames on closeout for $20, the motors were $10ea, Spedix IS20 is a great budget ESC, and the F4_SVTX is a great value FC/VTX at $23 (just runs really hot in the summer - set up and use the pit mode!). The batteries are CNHL and Turnigy 4S 650mAh packs, although I've ran these with 850mAh, and even 1000mAh 4S packs. Needless to say, these rip no matter what, althouth the heavier packs don't add much flight time. I did spring for the Gemfan 3052's, which really helps with pace (not so much efficiency).

The build itself is shockingly simple if you have 6-pin JST looms just hanging around, that becomes a quick and simple re-pin. The XM+ wires up easily, although my attempts to get an XSR with full telementry haven't worked. Tramp VTX control onboard the VTX does work well. Needs a bit of a stress loop on the U.FL antenna to be comfortable, but switching to the Lollipop and zip-tie direct to plate mounting the antenna solved any crash survivability issues. This setup handles crashes shockingly well, especially at the speeds I end up going.

Biggest downside with the frame is that 16:9 cameras will see the camera protection on the top plate - but any 4:3 camera ends up being just fine. Even that goes away pretty promptly as a downside, because these are just such a hoot to fly. The FC/VTX in 20x20mm form factor is a limitation when it's hot - if you leave it on, no matter what power, you'll have about five minutes before the VTX starts to do its thermal shutdown routine - do take advantage of the Betaflight low power capability if you plan on running more than 25mW output.

Efficiency isn't the greatest when pressed hard - but flying at 9/10ths these will achieve 3 minute flights readily at speeds which most people would thing require a 5" 6S rig. For me, antenna mounting with this particular setup remains tricky, but that's only because I crash really hard and quite a lot. Such is life for my track recce rigs, and exploration setups, but the durability in this build allows that. I do think that the weight offset of running a more conventional flight control stack and an AKK FX3 (or iFlight Succex) would help out, as would running a pigtail. The biggest limitation is that the narrow frame design does limit antenna mounting locations.

For anybody on a budget, it's really worth giving a 3" racer a try.

Being able to run <$8 batteries, having ~$175 complete builds, and the ability for these to absolutely shrug off most small crashes make it a phenomenal setup for racing and having fun.

Ethix sticker courtesy of SpiroFPV - while I was flying the other one of these. Well played...


Part List


Mode 2 Gizmo 3" Multipurpose Micro FPV Frame
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Flight Controller

F4 SVTX Flight Controller w/ Integrated 25/100/200mW VTX & OSD for BetaFlight (20x20mm)


Spedix IS20 2-4S 20A 4 in 1 BLHeli_S ESC (4 builds)


4 x 3BHOBBY Racing Motor 1408 3600KV (Pair)


GEMFAN FLASH 3052 (3" PROP) (8 builds)

FPV Camera

Caddx Turbo Micro F1 FPV Camera (77 builds)


A Pair Foxeer Lollipop 2 RHCP UFL IPX IPEX 5.8G 2.5dBi Super Mini Antenna For FPV Racing Drone (4 builds)


Frsky XM+ Micro D16 SBUS Full Range Receiver (1149 builds)


CNHL MiniStar 11.1V 3S 650mAh 70C LiPo Micro Battery - XT30 (11 builds)


Turnigy Graphene 650mAh 4S 65C Lipo Pack w/XT30 (2 builds)
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FrSky Taranis QX7 ACCESS 2.4GHz RC Transmitter - Choose Your Color (263 builds)


Flysight FPV Goggles 5.8Ghz Diverity Video Goggles SPX02 40CH Wireless RC Drone Racing Goggles with HDMI in and PIP Function DJI

Video Receiver

ClearView 5.8 Ghz Pro Receiver - ClearView Factory Direct

Radio Module

iRangeX IRX4 Plus 2.4G CC2500 NRF24L01 A7105 CYRF6936 4 IN 1 Multiprotocol STM32 TX Module With Case (5 builds)

Battery Charger

ISDT SC-608 150W 8A MINI Smart LCD Battery Balance Charger AU Warehouse (14 builds)

Soldering Iron

TS100 Portable Programmable Smart Soldering Iron (265 builds)


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