An efficient quad is lightweight and equipped with large propellers. Until now, I've been building the following machines based on ready-made frames:
- 3-inch with a 1-cell 2400mAh battery: Offers good flight time (22 minutes) and minimal maneuverability.
- 4-inch with a 2-cell 550mAh battery: Provides sufficient flight time (9 minutes) and high satisfaction in terms of maneuverability.
This time, I decided to take on a more extreme setup.
I aim to keep the weight below 100 grams. This aligns with the drone regulations in my country, Japan.
Regarding the frame construction, I found that using carbon plates would inevitably add some minimum weight, making it impossible to achieve a 5-inch machine. So, I opted to create the frame by cutting carbon fiber rods and using 3D-printed parts for connections.
As for the motors, I went with lightweight and affordable 1104 4500kv motors. I chose these motors based on their official test data for 1s 5-inch props, which suggested they could handle 5-inch propellers.
After assembling everything and conducting test flights, I found that the angle mode was not feasible, possibly due to frame flex and extreme lightness causing issues with the accelerometer. However, in acro mode, although some vibrations remained, it was possible to fly, and I managed to hover indoors for about 7 minutes.
Based on these results, I confirmed that when building a sub-100g efficient machine, 3-inch or, at most, 4-inch setups are the limits. If a manufacturer were to produce a highly precise and lightweight 5-inch frame in the future, there might be room for improvement. However, in my personal efforts, this is about the extent I could achieve.
Photos
Part List
Frame |
LIUHUA カーボンファイバーロッド スクエアのめに RC飛行機DIYクワッドローターの翼チューブアー
Amazon.co.jp
|
See Site |
Flight Controller |
F405 Brushless Flight Controller
(13 builds)
Betafpv.com
|
$16.99 |
Motors |
4 x マイクロブラシレスモーター1104 m,1 2s,4300kv,ミニリモートコントロールドローン,日曜大工,ミニfp
Ja.aliexpress.com
|
$12.68 |
Propellers |
HQ Durable Prop T5X2X3
Stanfpv.com
|
$2.89 |
FPV Camera |
C03 FPV Micro Camera
(3 builds)
Betafpv.com
|
$19.99 |
FPV Transmitter |
TBS Unify Pro32 Nano 5G8 V1.1 VTx Video Transmitter
(396 builds)
Pyrodrone.com
|
$29.95 |
Receiver |
HappyModel 2.4GHz EP2 RX ELRS Receiver - Ceramic AntennaDefault Title
(17 builds)
Racedayquads.com
|
$13.49 |
Batteries |
Gazoneng ドローン用バッテリー,550mah,2s,3s,4s,6s,100c,7.6v,11.4v,15.2v,22.8v,XT30U F v,rc fpv用プラグ付き
Ja.aliexpress.com
|
$8.43 |
3D Printed |
Adjustable Angle Whoop Canopy [Remix of Tiny Whoop - Mobula 6 - Canopy ] by nerdCopter
(7 builds)
Thingiverse.com
|
See Site |
3D Printed |
SUB100g 5inch Ultra-light quad by odekake_P
Thingiverse.com
|
See Site |
Hey...another avenue you can look down is using gears. The old Blade 180qx used large props with brushed motors. Take a look at my old build here -
https://rotorbuilds.com/build/7187
Going to take some more serious 3d designing though for the Brushless motor mounts, custom gears, etc... ;)
You could borrow some of the work already done on this from other modders:
https://www.thingiverse.com/search?q=mqx&page=1&type=things&sort=relevant
Your build and design truly impressed me!
Even in Japan, where I reside, I remember there were geared toy drones released about 9 years ago.
https://hitecrcd.co.jp/products/galaxyvisitor6/
It's highly informative!
However, I doubt I can achieve such precision in design and manufacturing with my current skills😂
the new Transformer 5" Ultralight adopts a lot of the same design philosophies with larger props and more payload capacity. It can fly upwards of 20 minutes on a 4 cell Li-Ion battery pack and in ideal conditions it's got a range of over 4 to 5 miles. In this guide I'll walk..
Awesome ! !
I hope you try to push the 5" further. Maybe replacing 3D parts by rigid aluminum hardware ?
7hHow does it sound? I guess it can barely be heard
Yes it was about flight noise. I built a 7'' 250gr (without lipo) back in the days and it was astonishingly silent.
If you are open to suggestions here is a link for inspiration https://dragonplate.com/new-tee-joint-carbon-fiber-tube-connector
If it was me, I would use the screws of the motor in combination with 'stainless steel paper clips' that I would reshape so that screws, rods and motors are joined by metal/carbon only. Also 'eating' some of the carbon with a file to make sure the 'paper clip' grabs thee rods firmly.
when you try to flex the quad by holding the motors, do you feel whether it's the rod that flexes first or the 3d printed joint ?
Also many flight controller batches have been 'polluted' by bad gyros. You can make sure yours has a mpu6000 by typing 'status' in the betaflight client.
I love how every gram counts to the extent that the props are screwless :)
Thank you for the wonderful links! They are very helpful in understanding how the parts are connected.
I noticed that when I bend the quad, the 3D printed parts are the first to flex. There's also some distortion due to the parts not gripping the rods securely.
I agree with your opinion that the parts should have a firm hold on each other. This is an area that needs improvement.
Yes, as you mentioned, the FC I'm using is equipped with an MPU6000.
Thank you for your valuable insights!
hey there! Whats the weight of the frame alone? I've also designed a sub100g 5" 3s Li-Ion with DJI Mavic Mini motors in the past using my tubular designs (www.eyeflydesigns.com). Maybe i can help you out, and also learn something from you regarding most efficient motor/prop combination. If you like hit me up on my Discord, (https://discord.gg/kq7auE6e9E). Greetings, Nic
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how does this work, wouldnt the motors get superhot?
The motors get hot, but they didn't reach temperatures high enough to cause damage. I'm using 6A ESC, and it might be because I've built it in a way that doesn't allow too much current flow.