2.5" BR25 / Runcam Split Mini / 1106 / R-XSR

By ghostface on Apr 08, 2018

22  2,538  15


Goal was to something a little smaller and less loud than my 3" beast - including HD capabilities.
Running 2.5" props on 1106 6000kv and 2-3s lipos, I will try 4s at some point but not sure if the Zeus will explode (can only handle up to 13a current draw on 4s).
I ended up at 103g dry and its a little pocket rocket!

Karl makes awesome frames and he already redesigned the sides for his br 2/3 frames to support a full stack + runcam split mini.
I am going to build a 4" using his br3 frame (which supports 3-4" props) next, using the new sides and a split mini but for the br2 I had already bought a zeus a while ago, so for this build I will stick to the "old" side-plates for now.

3d printed addons include the bumpers as well as some generic standoffs all printed in filaflex TPU.

Some painted highlights on the frame and red M3 screws and standoffs and paracord for the motor wires carry the color scheme further. I wish the runcam split mini came in red/black but for now this will do (maybe I'll repaint it someday). If you don't care about hd - a predator micro is a perfect fit!

R-XSR got depinned and is hooked up with full telemetry running F.Port.

Update after maiden

Had some issues with the split mini freezing at random times during my maiden. Video would still record and the red dot would also keep blinking as well as full OSD and quad control but no fpv feed (frozen still).
After inspecting I did notice that one of the brass nuts from the split stack was gone - not sure if it was the softmounting, the lost nut or voltage issues I decided to fix everything at once.

  • I changed the wiring and connected the split directly to one of the 5v pads of the Zeus FC, and moved the r-xsr to be powered by the vtx03 5v out.
  • I also swapped the top brass nuts for nyloc nuts and tightened them properly.

FPV feed was immediately clearer (less horizontal shadow lines) and all problems are gone now - no more freezing!

Initially I had problems with betaflight not being able to start/stop recording by switch - a firmware upgrade on the split mini solved that tho.

Flies very nice both with 2s and 3s 500-550mah lipos :)

Update on the VTX Mount

I ended up mangling my uxii and designed a vtx mount that keeps the vtx super safe, see link below.
The stl is actually a better version that I have yet to install compared to when I took the picture which is still from an earlier draft of the mount.
The new version prints perfectly without supports and gaps anywhere.

Alt Tag

Update - new sides and caddx

I ended up swapping the sideplates for the taller ones and the split mini for a caddx. Unlike the split I get practically no jello anymore (even on bent props :D)
Will probably post a separate log later on but here's a pic. Also sub 100g now :D

Alt Tag

3D Printed Parts


Part List


BR25 2 and half inch frame kit (2 builds)

Flight Controller

HGLRC F4 Zeus F4 Flight Controller Integrated with OSD BEC PDB AIO 15A BLheli_S 4 In 1 ESC for RC Racing Drone (15 builds)


4 x EMAX RS1106 4500KV 6000KV 7500KV Micro Brushless Motor CW Thread for RC Multirotor FPV Racing Drone (35 builds)


4 Pairs Gemfan Flash 2540 2.5x4 2.5 Inch 3-Blade Propeller with 1.5mm Mounting Hole (171 builds)

FPV Camera

RunCam Split Mini FPV Camera / HD 1080P 60 FPS Recorder (57 builds)

FPV Transmitter

Eachine VTX03 Super Mini 5.8G 72CH 0/25mW/50mw/200mW Switchable FPV Transmitter (417 builds)


Realacc UXII Stubby LHCP U.FL/IPEX IPX 5.8GHz 1.6dBi Super Mini Antenna For TX RX Fatshark Goggles (6 builds)


FrSky R-XSR Ultra SBUS/CPPM D16 16CH Mini Redundancy Receiver 1.5g for RC Multirotor FPV Racing Drone (936 builds)


Turnigy Bolt 500mAh 2S 7.6V 65~130C High Voltage Lipoly Pack (LiHV)


FrSky ACCST Taranis Q X7 Transmitter 2.4G 16CH Mode 2 White Black International Version for RC Drone (263 builds)


Skyzone SKY02S V+ 3D 5.8G 48CH FPV Goggles With Head Tracking HD Port DVR Playback for RC Drone (22 builds)

Misc Parts

5Pcs Realacc 58mm Battery Tie Down Strap for RC Micro FPV Racing Quadcopter Multirotor (6 builds)

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 Q6 Pro BattGo 300W 14A Battery Balance Charger (47 builds)
See Site

Soldering Iron

MINI TS100 Digital OLED Programmable Interface DC5525 Soldering Iron Station Built-in STM32 Chip (264 builds)
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zippity_dugas   Jul 05, 2018  

What about battery draw? Does using the runcam split affect battery life more or less than attaching the extra weight of a GoPro?

ghostface   Jul 05, 2018 

Split uses about 650ma while recording, for comparsion a microswift will use about 130ma according to my notes - compared to the added weight of the gopro you will fare much better ;) So for a 3 min. flight it will eat a little more than 30ma of your battery.

ghostface   Jul 06, 2018 

Correction Split Mini actually draws only 600ma

Esquisse   Jun 25, 2018  

do you see props on your split hd footage?

ghostface   Jun 26, 2018 

With the split running on the maximum fov setting and maximum uptilt that the frame allows you can see them a bit in the corners (check pic - i am using transparent props).
I am rebuilding this quad using the new sides and a tx20 vtx and that will get rid of them (no props in view on my 4" with the same sides).

fiveomustang   May 15, 2018  

Could you shoot me a link to the motor/frame protectors you printed? I can't seem to find them at your link above. Also, how did you secure the VTX to the top of the stack? I orderd your BOM above and going to build the same! Your build looks great by the way!

ghostface   May 15, 2018 

I talked to the creator of the frame and he gave me permission to upload the bumpers on thingiverse (I initially thought I downloaded them from thingiverse).
I also ended up designing a better vtx mount as I mangled my uxii with the zip tie mounting solution :D
I updated the post accordingly.

VTX Mount: https://www.thingiverse.com/thing:2876436
Bumpers: https://www.thingiverse.com/thing:2913566

ghostface   May 15, 2018 

Ah sorry regarding the vtx I just used some vhb tape. Alternatively the vtx can also fit exactly between the standoffs and can be stuck/clamped in place by them but I still had some space below so I just it to the split along with the receiver.

fiveomustang   May 15, 2018 

Thank you!

ghostface   Apr 09, 2018  

Frames are also available at armattan productions btw: https://armattanproductions.com/pages/shop_product_grid/2209

7uvoK   Apr 08, 2018  

Nice! I have been told elsewhere, and the product specs now clearly state, that the Zeus is 3S only.

I am building a 3" micro with the Split Mini too. I don't have the brass standoffs. I was planning to use nylon washers as spacers. ANy reason that will not work?

ghostface   Apr 08, 2018 

You are mistaken, hglrc page says "Must keep current under 13AMP at 4S", no bursting above that at all or it will catch fire :D

I actually mailed runcam about the standoffs on the split mini and they replied to me that they can be replaced with nylons and they are not required for the split to function.

I just kept them between the boards to ensure that the connector between them is not stressed by the standoffs flexing in a crash or something.

7uvoK   Apr 08, 2018 

Thank you, very helpful.

acromode   Apr 08, 2018  

i like the velcro cable tie battery strap!

ghostface   Apr 08, 2018 

Yep saves weight! But that one is only good up till 3s battery size, 4s would need a longer strap, but perfect for 2-3s

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