Building a custom octocopter from scratch with no prior hardware experience | Hacker News Reader

Building a custom octocopter from scratch with no prior hardware experience

karolina.mgdubiel.com

418 pointsnoleary91 comments

Hi!! I'm Karolina, and this is my project! Had no idea this got posted until someone DMed me about it on LinkedIn. Feel free to ask any questions or follow along via X (karolina_dubiel)

Thanks so much for all the kind words, it means a lot!

You seem very talented, great work!

This is very impressive! I researched fault-tolerant octorotor control using RL in grad school for a NASA project. Perhaps this may be helpful[1, see section 8.3]! The field is moving fast, so there may be better or more suitable approaches out there now.

For folks who are interested in UAV physics, I wrote up an explainer[2].

[1]: https://drive.google.com/file/d/1RTEVRd0XCWLuDXY2nkbmYuOaa5x...

[2]: https://iahmed.me/post/drone-physics/

This is lovely, thanks!

Something I've wondered for octocopters - could using a ring instead of arms be beneficial for weight? 6.28r < 8r, but then again the arm radius is usually less than the full circle, and some components want to be centrally located, etc. I could imagine holding the central components in tension via light filaments (carbon fiber, nylon, etc) in tension, vs having to have rigid structure, but the small factor between 6.28 and 8 and maybe makes it not worth it.

consider "tiled" hexagons, like honycomb.

large schedule 40 or 80 tubing sliced into rings would be pretty quick source material, starting with duct tape and zipties until you find a good arrangment then get into the glue and screws.

Amazing: I'm watching lots of homemade builds atm.

I've got a question: why CNC milling and not just FDM 3D printed parts? TFA doesn't talk much about it except saying she went to a machine shop.

> 2. CNC milling forms out of G-10 fiberglass (arms) and 5mm carbon fiber (body)

TFA also says this:

> The solution for this is to 3D print a 0-tolerance assembly jig to hold the arms in perfect position while the center of the drone is superglued together.

Why not 3D print it all?

There's this guy who built a drone that can fly for 3 hours and cover hundreds of miles, 3D printed at home on a $250 printer:

https://youtu.be/e7AIKGDrlgs

Then there was the $200 K quote for the body for a car that just did Pike's Peak with a four times Pike's Peak champion and instead the team... 3D-printed the car's body at home (something like 40 parts, assembled together), which cost them less than $2 K to make (1/100th of the quoted price for the car's body). Here's the vid where they print all the parts (on a $1500 consumer printer):

https://youtu.be/nt85nTMnY1w

Basically: why CNC milling and not 3D printing at home when many drones enthusiasts (and now too people building race cars) simply print parts at home on a consumer-grade 3D printer?

Stiffness. Important for how the frame behaves under load and buffetting etc.

^^ This was why I opted not to 3D print the whole thing :)

For "copter" style drones, 3D printing is basically a "noob" meme at this point; everyone thinks it's a good idea, tries it, and realizes that it's actually really hard and doesn't work.

Copter-style drones are exposed to vibration across a huge frequency range in every axis, and it's almost impossible to avoid really nasty resonance issues using generally-printable FDM filaments and "standard" design techniques; it's a lot easier to just use super-stiff carbon fiber and CNC it.

For planes, like what you linked, 3D printing is more "plausible" than for copters but also not really practical; you can 3D print a good plane, but plastic lacks the durability and favorable weight characteristics of foam - plastic planes tend to be "one time crashed" while foam is easy to repair, restore, and rebuild.

3D printing isn't stiff enough for a larger drone like this, you'll get flex which will upset the PID loop and cause it to be very unstable if it even flies at all.

You'll notice on your 3D printed drone link that the actual multirotor part is carbon fiber tubes. The motor mounts and other brackets can be 3D printed without issues.

I find it very hard to believe that someone who has never done any CAD could design that with Fusion 360 in a day. I do lots of 3D design with Fusion and there is a serious learning curve. It's not something you can pick up in a day. She is doubtless much smarter than me, but that's not credible.

Did you look at the parts and content, or just leap to this assumption?

My first couple days with Fusion had similar outcomes, and this is totally credible. There are extremely talented YouTubers that have information-dense guides through many features. It's totally plausible with that and having a mentor showing you a tool to succeed here.

Why add negativity to something cool? There is a build log! It's well done and tangible! It's not slop! Celebrating is always more fun than humbugging.

Hi, I’m Karolina! I get it!! I’d probably have some doubts if I saw this online too.

To be fair, I definitely did not get good at Fusion in a day (I’m still not very good at Fusion). The Day 1 CAD was all flat shapes -- all I had to do was use the line, curve, and pattern/mirror tools and then extrude those shapes to my body plate / arm thickness. Same with the screw holes -- I didn’t know there was a hole tool and was just drawing circles, patterning them, and extruding them backwards. It still took me forever, I started super early in the morning and worked on it until ~2pm, knowing it would probably take a MechE major 30 mins to do the same thing.

I also do have mentors in the form of eng majors who can give me verbal feedback / advice / show me which tools to use / get me unstuck. To me, it was very important that I was the only one actually doing the CAD so I could learn, but I definitely have had super amazing mentorship along the way to teach me and point me in the right direction. The motors and props are just 3rd-party components that I imported (still took me ages to figure out how to constrain them right). I went to the machine shop after and that took forever too, especially figuring out how I’m supposed to arrange the plates for printing in Fusion (but I had people to help me out there, they were not going to let me use a CNC mill alone with no exp lol)

I made the GPS / receiver mount way later in the process because I was so intimidated by the CAD for it (literally taped my GPS and my receiver to the drone for the first flight instead), and it took me days (also such a simple component, but the stuff that’s not just an extruded 2D shape is way harder for me).

I’m definitely not superhuman and it’s probably going to be years before I feel truly confident in Fusion :))

Cool project! For a DIY beginner, what would be a good starting point for a "normal" drone/octocopter project?

Hi, thank you!! There's so many great resources for building your own quad from scratch (ex https://www.youtube.com/watch?v=S9dvDU5RmQU&t=476s). I honestly wouldn't recommend an octo unless you have a reason for it (like wanting more fault tolerance, etc) solely because it's twice as expensive for the motors. I got all my parts from GetFPV and Amazon. At the very bare level, all you need is a FC, ESC, frame, props, motors, receiver, and battery (plus controller, and goggles/camera if you want it to be FPV)

If I were to get a dirt cheap Chinese drone, would that be more likely to use RL or MCP? What’s the “standard”?

PID is more than enough to keep level. FPV relies on manual flight, but you can get Ardupilot for autonomous missions. There's no need for RL, nothing to gain here; level flight and following waypoints is a solved issue already.

And frankly as a pilot, I'd rather not see any completely autonomous drones with no oversight in the sky - that's one incident away in which blame cannot be put solely on the operator from getting the hobby completely banned.

Interesting - thanks! OP's drone IS using RL and that's what jumped out at me - it felt a bit overkill for the usecase.

Hey! This is a great question because RL is overkill for my use case, you're right! The reason I'm using RL is because I wanted an RL project on real hardware, so I built this idea of a drone project around that concept, not vice versa. A lot of people on X have brought up alternative solutions -- like MPC -- that might be a better approach to this problem engineering-wise. I just really wanted a real-world RL problem and this was kind of the first cool idea I thought of :D

I'm sorry for the late response, I didn't realize someone had posted my project

That makes total sense, I never meant this in a negative way! I really like your project and am following along now, good luck!

As a researcher in the autonomous robotics space, there is a lot to gain in RL over PIDs and manual flight.

The delta between what is possible with current autonomous flight missions and manual FPV style flight is by having a brain on board that can dynamically adapt to a changing environment. There are a finite amount of PID profiles for each steadystate solution that a researcher can preprepare for. But RL allows an overarching heuristic to transiently alter the PIDs depending on the changing environment.

We use PIDs because analyzing robotics platforms as seeking a steadystate dramatically simplifies the math needed to where its computationally possible for us to solve for a situation.

We use RL in systems that have continuously changing environments with transient solution spaces that are easier to model in hyperspace with a RL model.

Take for example platforms that have tiltrotors. They ideally have a minimum of 3 PID profiles for flying. One when it best fits a multirotor profile. A second when it is transitioning from multirotor to fixed wing flight, and a third for when fixed wing flight is established. What happens when the researcher has a need to fly in the transition state, or subconfigurations of the states? How many PID profiles are you looking to think of and train for? This is where RL has dividends.

Low end and most open source stuff will use a PID inner loop for “fast path” control (stabilization) and either a second PID loop or something a little better (Kalman filter etc) for the slow path (position / path hold).

Higher end stuff will use a ton of inputs (visual odometry, binocular vision, lidar, range finding, etc) fused into some kind of proprietary blended algorithm that you could probably call an MPC.

RL is pretty cutting edge, especially for fast path motor control; there are a lot of university competitions for drone control that lead to a lot of papers and projects in the space (some promising) but most commercial stuff has not adopted this yet, certainly not at the low end.

Phrased in a slightly different way, assuming the standard is Betaflight/Ardupilot/PX4. (This article uses BF): Inner PID rate loop; this compares IMU-measured rates vs that commanded by manual controls. This might run at 1-4kHz.

On top of this (Maybe at a few hundred hz), you can add outer controls to set attitude. This could be an autopilot, or having the controls command attitude instead of rate. Betaflight pilots usually don't both with this, and have the simple setup of control maps to rate.

I've programmed firmware using a weird hybrid where the controls command a change in the target attitude. So it flies like rate, but has the forced attitude stability of an attitude-based control system. Non-standard, but makes it so you don't need to worry as much about tuning the PID loop. In practice, you can do full aerobatic flight with this like you'd do with a rate-only setup. (Basically, there is a commanded attitude quaternion; controls nudge it; the PIDs update motor power to maintain this commanded quaternion.)

Kudos for such a great learning journey!

I love everything about this. Well done! but missed opportunity to name it R_of_L-copter.

This is cool as sugar! I have to ask though, how many end mills did you go through milling G10 fiberglass and carbon fiber‽

I've heard the dust from carbon fiber is second to asbestos for inhaling.

Also there was a video about touching the edges of carbon fiber where it is not surface treated is embedding countless small shards of carbon into your skin, only visible through magnification, which cannot be healthy..

We shed the outer layers of our skin fairly often so I don't imagine it would be a big problem unless they were pushed deep enough maybe?

Asbestos is dangerous not because it's asbestos, but because it makes small and sharp fibres that embed in the lung tissue.

Carbon Fiber (and even fibreglass) can make fibres that small and sharp. So yeah, responsible dust handling is key.

The good news is that Asbestos easily puts off those small fibres just by being handled. CF and FG need to be damaged or machined to do it, handling the material after the dust has been dealt with is fine.

Will follow a fellow Polish inventor! :)

Hi!! Would love to connect :) My X is karolina_dubiel and LinkedIn: https://linkedin.com/in/karolinadubiel

I do not notice that the time of posts is reversed haha. I am confused whether you had build it.

Thank you, it's cool!

Newest is at the top :D If you press the little "Collapse All" button on the top right of the blog posts, you can see the full timeline + dates of the entries.

I did start by designing/building a regular FC (no RL or anything) and am doing RL training afterwards, so I agree that the whole timeline looks a little confusing without background context since it goes real drone --> sim haha

Thank you for your reply. it is a good reading experience, too. :)

I wonder if the 3-propeller design has advantages.

Love it, great to explore and learn, and I like the mixed background too of cybersec and robotics (all the way to CNC), just like myself, I think these two new fields will make a new industry, similar to OT cyber but more niche.

Which also means great people can go beyond what’s their school was about, so a CS major doing CNC isn’t “weird” or different, I remember when applying for jobs in systems in aerospace industry and get rejected despite having a systems background too, with feedback of “they are looking for people with education only in aerospace”, which is idiotic thing to consider.

So good luck OP, start exploring hacking mavlink or similar protocols which is what im working on.

Super cooool

You know you're doing a great job, OP, when the peanut gallery here has nothing more substantial to add than to critique your em-dashes; greek-latin root word mix-ups despite the common vernacular having moved on from that; and lack of title brevity.

Congratulations --- this is a super cool project. I wonder if you've considered using ultralight filaments and 3dprinting the frame? PLA is stiff but brittle, and I know Bambu and a few others sell specialised versions that supposedly weigh less than normal.

Yes. And when your design is simply beautiful as this is:

https://karolina.mgdubiel.com/drone/drone-img/05-30-26/cnc_c...

Most filament based printed frames end up with really nasty resonance; it’s possible to engineer damping around the issue with some clever 3D design if the parameters of the prints are measured, but overall 3D printing copter frames doesn’t tend to be a straightforward solution.

I agree with your first point.

The milled fiberglass the author used is a much better UAS frame material than anything from a filament 3d printer due to stiffness and related considerations.

Oh no doubt. I'm no drone expert!

[flagged]

I will stick up for spiralcoaster. This post is direct and could be interpreted as offensive. Sarcasm both in general, and especially over text is often not appreciated. (It partially depends on culture). Yet, I think this analogy is appropriate here, and I was thinking along the same lines.

But people do 3d print frames for drones and gliders. It's undoubtedly worse than carbon fibre, I guess, but I found it interesting enough to share that you can buy especially lightweight filaments designed for aeronautic stuff.

I wish we had some standard filament testing that most manufacturers were willing to provide results for.

Until that happens, this guy here is probably the next best thing: https://www.youtube.com/@MyTechFun

Plot twist: many of the "special" filaments aren't special at all or at least very exaggerated.

> the peanut gallery here has nothing more substantial to add than to critique

The comments in this thread are overwhelmingly positive by now. Watch out for the contrarian dynamic! (https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...).

Needlessly negative comments tend to show up first in a thread, while positive responses emerge over time. (Why? well, I have my theories: https://hn.algolia.com/?dateRange=all&page=0&prefix=true&sor...)

It's a fine thing to counteract that with a positive comment, but if you can, please omit the snarky bits (such as in your first paragraph). I know they're tempting, but they tarnish the positivity and substance that you correctly want to see in the discussion - and in the end they "bond" (in the molecular sense) more with the negative posts than with the outright positive ones.

Your second paragraph on its own would make a much better (indeed excellent) post - and that is the best way to combat the negativity.

(I know my reply here is itself an instance of the thing I'm talking about - responding negatively to the negative bits. Sorry!)

Hi! Thanks for your kind words. I actually had no idea this got posted here, I'm Karolina, and this is my project! Really cool to see some feedback here! I went with CNC cutting over 3D printing just because I wanted to avoid any stiffness/vibrational issues. I don't actually have any prior drone experience, so I wanted to play it really safe with that.

People are so jealous. This is cool as hell.

It's cool, but I could have done it 2.45 weeks!

Something happened recently that attracted a whole bunch of quite ignorant and frustrated people to this site.

So many activists of different kinds.

Activists have political ambitions, but most LLM nonsense is just engagement farming. =3

Don't forget bot AstroTurf, and several con artists attempting various scams. =3

Hm making an AI assisted page and replacing the emdashes with double dashes seems like more work than to just rewrite the text yourself. Not sure why you would do that.

What? That’s a simple find and replace vs rewriting the whole thing. If someone had the savvy to write the thing, they probably wouldn't have been using the the assistant in the first place. Either way, comparing a find/replace to rewriting is farcical

The abstract certainly smells like 100% LLM-generated text.

Tbh this is cooler than anything on your github so he (edit: she) can do what he wants IMO

> more work than to just rewrite the text yourself

You think s/—/--/g is more work than rewriting a whole article? Is this what you're saying?

I use Claude Code to help me with the updates on my website/blog because I have a full time job and try to squeeze this side project into as little time as possible :) It's definitely not fully AI-generated, though, I love writing, and I'd consider myself "savvy" enough haha. But it's ok if you don't agree! Sometimes it's easier to use Claude to condense ideas (for ex, the abstract) when I'm on a time crunch. But either way, Claude definitely didn't solder, CAD, or CNC-cut anything for me :D

I don't think there's any shame in using LLMs to save time on documenting your projects. Let's be kind and positive to each other!!

You could be more fault redundant by having two motors and props on each axis.

Why not just say from scratch instead of no prior experience, is it to brag

Might be intended to preemptively deflect criticism of "reinventing the wheel"/solving subproblems in a non-standard/convoluted way.

I'd expect an engineering project with "no prior experience" to take weird/experimental approaches more often compared to a "from scratch" project (where I would expect proven minimalism instead).

"from scratch" and "no prior experience" have very little in common.

This person made it from scratch with no prior experience, so the bragging rights are well earned.

Nit pick:

The name "octocopter" does not make sense. "Helicopter" is a compound word made of "helico-" and "pter", which means "screw-wings". "Octo-" means eight, "-co-" means nothing.

"Octopter" would be a correct compound word meaning "8-wings", but that would be ambiguous, so the object discussed in TFA is better named just "8-propeller drone".

The -copter suffix is very common in the drone community.eg quadcopter is widely accepted https://en.wikipedia.org/wiki/Quadcopter

Hence a nit.

Nit pick: "nit pick" means to remove tiny bugs from hair, which this is not.

Oh, language changes and now "nit pick" means "to make trivial criticisms" even though neither "nit" nor "pick" etymologically has anything to do with criticisms? How very self-serving of you ;)

Unrelated.

It's a metaphor:)

Are you trying to say that it’s been co-opted? Did anyone consult the Egyptian Christian community about this?

Similarly, "heli" is a commonly recognized clipping of helicopter: https://en.wiktionary.org/wiki/heli#English

See e.g. https://en.wikipedia.org/wiki/Helipad

Counterpoint: -copter is a perfectly cromulent suffix. https://en.wiktionary.org/wiki/-copter

gyrocopter, helicopter, quadcopter, hexacopter, octocopter, parcelcopter, and—most famously—

roflcopter, https://en.wiktionary.org/wiki/roflcopter#/media/File:Roflco...

They all have their own dictionary entries.

Octocopter makes perfect sense. Everyone understands immediately what it means, and that's the only purpose of language: to convey ideas. It should be clear, which this is, and concise, which this is.

Fidelity to ancient Greek is not, and should not, be a goal for English.

Great examples. The English lexicon is continuously embiggened by the adoption and expansion of terms.

9/10, missed opportunity for "cromulent terms" at the end there.

The reference in the parent comment was already suitably frabjous.

Blame language evolving over time rather than OP, octocopter is a widely-used term for '8 propellor drones'.

A nit pick with your post - you use the word 'ambiguous' but really this is from the latin root 'ambiguus' so we don't need the supurflous 'o' in between the two u's.

Well I was confused by it! I was expecting an article on amateur semiconductor fabrication. Granted, that was due to my misreading it as 'optocoupler'.

This is quite a common linguistic phonomenon, where a word is rebracketed to form a new suffix, even if it doesn't make sense with the original etymology. See also -holic (alcoholic -> workaholic), -thon (marathon -> danceathon) or -gate (Watergate -> partygate). Termed a "libfix" from liberated affix

>phonomenon

I guess this was a typo, but fits perfectly. Kudos!

That ship has long sailed. You’re correct, but the author isn’t the one who “named the thing” in this case, they are just using the name commonly used to describe it.

Multi-rotor drones have been called tricopters, quadcopters, hexacopters, octocopters based on their propeller counts conversationally for as long as I can remember.

There are plenty of commercial vendors who use the exact term for their expensive industrial drones.

Update: I see that in the four minutes it took for me to validate my initial inclination and post that plenty of others also had the same thought :) No need to me to belabor the point!

"Copter" is a known word, short for helicopter.

https://dictionary.cambridge.org/dictionary/english/copter

On a related note, pronunciation variance in "Helicopter" -> "Helacopter" -> "Helocopter" leads to a confusing abbreviation - "Helee" vs "Heelo"

I guess it's a play on the popular word "quadcopter", rather than "helicopter".

McDonald’s getting a strongly worded letter from the Mayor of Hamburg over their use of “cheeseburger”.

In this fundamental paper, the authors argue for multirotor instead of -copter. In academia, this term seems to have stuck.

https://ieeexplore.ieee.org/document/6289431

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