ACROBRAT

http://acrobrat.com/

Ummagawd created a miniquad that doesn’t intimidate newcomers, and doesn’t disappoint seasoned FPV pilots. A balance of size, budget and fun-factor, that encourages anyone to create awesome HD FPV videos, without risking expensive equipment, breaking laws, or scaring spectators.

Design Goals:

Deliver an HD freestyle quad for less than the price of a gopro session 5 (at the time $299)
A 3” quad that feels and flies like a 5”
Uses the runcam split mini, but mitigates the jello issues that the split is prone to
all in a package that is fairly durable and not intimidating for the pilot or spectators

Specs:

Unibody Main plate = 3mm bi-axial Toray Carbon Fiber
Side plates (w/adjustable FPV cam placement) = 2mm bi-axial Toray Carbon Fiber
Battery plate (w/optional top mount FC holes) = 1.5mm bi-axial Toray Carbon Fiber
Hardware = Stainless Steel
Frame Dampeners = Custom Poly-urethane
Motor to Motor (diagonal) = 163mm
Motor to Motor (front to back/side to side) = 115mm
Overall Frame size = 141x141mm
Frame height = 55.5mm
Dry Frame Weight = 54g
Motor bolt pattern = 12x12mm
Motor c-clip hole = 6mm

Which Camera?

My biggest concern is the FPV quality. After watching several videos comparing the available split cam options, I wasn't satisfied with all of them. I can live with the HD video output of all, since I only want to be able to record my flights, not to deliver production quality video.
But I want better FPV than this blurry output caddx turtlet, runcam split and foxeer mix deliver.

The new Caddx Tarsier - The cam to rule them all?

https://caddxfpv.com/products/caddx-tarsier?variant=21604688658521
https://www.banggood.com/Caddx-Tarsier-4K-30fps-1200TVL-Dual-Lens-Super-WDR-WiFi-Mini-FPV-Camera-HD-Recording-DVR-Dual-AudioOSD-for-RC-Racing-Drone-p-1467840.html?p=@K2800431511201401MH&ID=229&cur_warehouse=CN
18g

VTx Setup

?? The guys who built in a unify pro, talked about it going up to 800mW.
Since we are limited to 25mW anyways - Is there any other advantage of using the regular unify over the nano version?

The nano is 1s-3s - I need 4s. Therefore the regular unify pro. Or the race edition that is caped at 200mW but cheaper.

?? Regarding antenna and position. The antenna is pretty recessed into the 3d printed mount - Is this a good enough signal?
Or would it be better to use the stub, which protrudes a bit more. I guess in the end the drones tail is mostly up, so it doesn't matter all to much...

Its actually signal vs. sturdyness. I expect to crash a lot with this thing (The idea is to fly less conservative with it).
From this point of view, I tend to take the SMA antenna.

TBS Unify Pro 5G8 HV Race 2 MMCX - 4.2
https://www.dronefactory.ch/produkt/tbs-unify-pro-5g8-hv-race-2-mmcx/
Lumenier Micro AXII Shorty MMCX 5.8gHz Antenne (RHCP) - 2g
https://www.dronefactory.ch/produkt/lumenier-micro-axii-shorty-mmcx-5-8ghz-antenne-rhcp/
Total 6,2g

Motors

For the smoothest flight (and therefore least jello) the Specific Acrobrat motors (Hypetrain Brat 1407 4140kv Micro Motor) seem to be the best.
Also strong enough to carry the weight and the lightest I saw. Especially smooth with lower pitched props like the HQ 3x3x3

Hypetrain Brat 1407 4140kv Micro Motor - 13.3g, $17.-
https://rotorriot.com/products/rotor-riot-hypetrain-brat-1407-4140kv-micro-fpv-motor
?? The Hypetrain Brat 1407 4140kv Micro Motor need screws to mount or just a nut?

Looks like it takes 2 M2x8mm screws each - t mount
https://rotorbuilds.com/pictures/f_10058_7kU8jnuaVT3hmgoB0nXpDUxbg.jpg

3D printed parts + colored stand offs / screws

Some parts seem to suppprt a cleaner build (backplate), even though they don't look great. Therefore I added the brain3d acrobrat set (in black so it does not catch the eye). WIll use all but the ugly frontbumper (especialy since I plan to use colored spacers).
https://www.brain3d.co/products/ummagawd-acrobat-accessory-kit?variant=12557036388439

!! Buy with forever tubes for the antennas

!! The parts seem to be pretty heavy (18g for the whole set).
Guess I go for some lighter skids:
Acrobrat Lightweight Feet - 3,1g
https://www.thingiverse.com/thing:3100892
And just for the backplate from brain3d:
https://www.brain3d.co/products/ummagawd-acrobat-antenna-mounts?variant=12185868140658

?? Do I need M2 20mm standoff's or M3 25mm standoff's?

Hardwarepack says > M3x6 screws & M3 25mm standoff's

Put a cap on - It's noisy out there

?? Which capacitor?
1000uF 35V (4S, 5S), soldered at XT30

The come usually with the esc

1000 uF, 35VDC - Low ESR Kondensator Kurz lang
https://fpvracing.ch/de/bauelemente/1281-1000-uf-35vdc-kondensator.html?search_query=low+esr&results=7

https://oscarliang.com/capacitors-mini-quad/
https://youtu.be/VTkBM8IN5_Y?t=1092

Batteries

4s 500mAh 80c - 65g, 60x30x19
https://www.getfpv.com/lumenier-500mah-4s-15-2v-high-voltage-80c-lipo-battery.html
4s 650mAh 75c - 74g, 60x31x21
https://www.getfpv.com/tattu-650mah-4s1p-75c-14-8v-lipo-battery-pack-with-xt30-plug.html
4s 700mAh 75c - 80g, 57x30x25
https://www.getfpv.com/lumenier-graphene-700mah-4s-75c-lipo-battery-xt-30.html
4s 850mAh 95c - 104g, 60x30x30
https://www.getfpv.com/tattu-r-line-850mah-4s-95c-lipo-battery-xt-30.html

!! Check out Swaytronic.ch - A swiss LiPo producer. They also offer completly customized batteries.
4S 450mAh 75C/150C XT30 - 55g, 58x30x18
https://www.swaytronic.ch/Sway-FPV/Sway-FPV-4S-14-8V-75C---140C/sway-fpv-lipo-4s-14-8v-450mah-75c-150c-xt30.html
4S 700mAh 75C/150C XT30 - 80g, 57x30x25
https://www.swaytronic.ch/Sway-FPV/Sway-FPV-4S-14-8V-75C---140C/sway-fpv-lipo-4s-14-8v-700mah-75c-150c-xt30.html
4S 850mAh 75C/150C XT30 - 102g, 55x30x35
https://www.swaytronic.ch/Sway-FPV/Sway-FPV-4S-14-8V-75C---140C/sway-fpv-lipo-4s-14-8v-850mah-75c-150c-xt30.html

Estimated Weight - Target <= 250g

54,0g Frame (Is this with hardware parts? > Yes)
3,0g FC
7,1g ESC
8,2g Props (2,05g x 4)
19,5g FPV Cam (Spec says 18g, review says 19,5g)
5,0g VTx Transmitter
1,4g VTx Antenna
1,5g Rx
3,0g Xt30 plug
3,1g 3D printed lightweight feet
~5,0g 3D printed backplate
~1,0g Micro SD card
53,2g Hypetrain Brat Motors (13,3g x 4)
~165,0g without battery
80,0g Battery
245g total

Cost

Not a budget build. Pretty expensive actually. For the same money I could also build a 5" frame.
Getting more expensive kind of counters the idea of a smaller, cheaper craft to fly more risky.
So I analyzed why my build is like 80 bucks more expensive than the average.

The culprits are:

• FC and ESC > I want the FlightOne (Otherwise maybe 35 bucks less).
• Cam > Tarsier is 33% more expensive (40 bucks less with caddx turtle)
• 3D printed parts > backplate is nice (Otherwise 10 bucks less)

So basically the flightOne products and the tarsier cam - Can live with that.

Build Videos

Tommy himself (with different fc though)

Skitzo's Nova build (uses a similar fc/esc combo)

Ummagawd Acrobrat Build Tips

Kremer FPV - Ummagawd Acrobrat - Build & Flight

Other builds

https://rotorbuilds.com/build/13506
https://rotorbuilds.com/build/14408
https://rotorbuilds.com/build/14179
https://oscarliang.com/acrobrat-split-mini-build/