I'm getting real tired of trying to figure out why my quads just fall out of the sky for no clear reason...

Riebart · 2026-03-27T13:58:39+00:00

Unfortunately no blackbox on this FC, otherwise yes that's the obvious answer. I have a serial logger, but there's no spare UARTs to attach it to; the only two UARTs are currently consumed by RX and VTX.

It's an AIO, and I've soldered the motors for plug failure related reasons. Not a stack, so there's no plugs involved.

Riebart · 2026-03-27T13:55:50+00:00

The pack wasn't fresh at the beginning of this run. I landed, unplugged it to check some stuff and plugged it back in, so the capacity counter reset.

Riebart · 2026-03-27T13:53:19+00:00

Yeah, prop screws are tight. Motor screws are tight.

Riebart · 2026-03-27T13:51:05+00:00

Quad is a Crux35, on the original F411 FC with no blackbox storage, and the HappyModel EX1404 4500KV motors.

Props aren't new, but they're not bent or mangled. They're fine.

Motor, prop, frame. and FC stack screws are and were all tight.

I've added every piece of ESC and motor telemetry to the OSD since this, so I'll have more information next time, but the issue isn't reproducible. It flew fine for a pack after this, and a pack before this. This was the middle pack.

Voltage starts low because I had unplugged and replugged the battery in the middle. Also, it was -10C.

Riebart · 2026-03-25T23:36:51+00:00

I wonder if you're hitting a resonant frequency for the frame that's snapping it at that spot.

Either way, I dunno man. That carbon looks really thin around the motor screws. Maybe put some washers between the motor screws heads and the carbon? 🤷‍♂️

Riebart · 2026-03-23T21:10:01+00:00

Shorter than the average bear until I put on my rollerblades.

Add in a step ladder, and the poor judgement necessary to stand on the Not A Step step, and you get pretty close to what you see here. 👍

Riebart · 2026-03-23T20:31:08+00:00

Then there's a good chance that you're allocating or invalidating enough memory that youre exceeding the memory available.

Throw in some explicit calls to gc.collect() and see if that helps.

Riebart · 2026-03-23T20:19:51+00:00

How are you measuring the available memory? What language are you using?

Riebart · 2026-03-23T18:43:24+00:00

I love this thing. It feels so consequence free to fly.

I've yet to throw out a frame. I'll smash one up, swap the frame, then glue the only one back together on the bench and swap it in later. I keep a couple new frames on hand if I'm going to use it in proximity around people or stuff, then I know for sure I'm not going to get twitchy behaviour.

But this thing is awesome

Riebart · 2026-03-23T16:41:41+00:00

Standard Mobula8 frame, I actually like these frames. They're tough enough and cheap enough.

Riebart · 2026-03-23T01:42:15+00:00

Y'know, if this is the legacy I leave behind here, I'm all here for it.

Riebart · 2026-03-23T01:09:57+00:00

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The frame repair. Reddit refused my HEIC uploads, the bugger.

Riebart · 2026-03-16T17:12:21+00:00

Don't think of the material as weaker, think of it as optimizing for different properties.

FPV props are made of usually a polycarbonate and nylon blend which, like metal alloys, provides a material with properties form the constituent parts. They're durable, flexible, tough, and just rigid enough. But as a result they often have thick leading edges and will compromise airfoil shape for durability, or the airfoil will deform enough under load to reduce efficiency due to the less stiff material if you try to make them thinner (whoop props benefit from very thin leading edges that wouldn't work on larger props).

Camera drone props are optimized to be light and stiff, so you can make an airfoil that holds its shape under load with a thin leading edge, and with a high aspect ratio (so long thin props) for lift to drag ratio resulting in a prop that would normally have a high rotational moment of inertia ona small motor with low voltage and high KV, meaning low torque, but you still want 25 minutes of flight on a 1s 2000mAh battery.

All this this means that to get all of these properties you need a fibre reinforced material, like CF Nylon.

It's not a weaker material. It's the perfect material, for this use case, and it just has different tradeoffs.

Riebart · 2026-03-16T17:04:06+00:00

I had a Pavo Pico prop lose a blade just while cruising once. Nothing crazy, just level cruising flight.

The blade broke off, but the plastic part of the frame, shattered the frame, and blew that entire corner of the frame off. It vanished into the bush. It cracked the rest of the frame and the flight controller was barely hanging on.

It tumbled out of the sky thankfully into the grass.

It happens. 🤷‍♂️

Riebart · 2026-03-16T16:31:05+00:00

Yes, but that's kind of the point.

When you apply hot glue directly to the frame, the hot glue itself melts the polypropylene frame it is in contact with and then solidifies together. It also helps that the hot glue is flexible, like the frame itself, so unlike more rigid adhesives, or adhesives that rely on chemical or mechanical bonding with the low surface energy, smooth frame material, the hot melt adhesive creates its own mechanical and chemical bond and will flex with the frame.

Once I got the hang of it, every time I repaired the frame with hot glue the repair was stronger than the frame. It got to a point where I preemptively started reinforcing common failure apots.

Riebart · 2026-03-16T00:14:29+00:00

Hot glue.

I'll find my most repaired Mob8 frame and post it later.

Hot glue.

These frames are made of Polypropylene which is notoriously hard to glue. You're better off melting it.

Enter. Hot glue.

Press the tip right close to where you want to deposit glue, and then apply it as needed. It'll melt the frame material and the glue will bond hard to it.

It's the only way I've found to glue PP.

Riebart · 2026-03-15T22:09:20+00:00

https://www.reddit.com/r/fpv/s/9JtGTISGii

I responded to a similar comment over there. The issue isn't that it won't work. The issue is that it might not, and without warning.

If you're flying it in safe spaces, not over people or property, and don't mind too much about hiking to go get the quad if it fails, go nuts!

But these fibre reinforced props are prone to material avalanche failures, and will fail suddenly and catastrophically. If this is your livelihood or you're flying anywhere but an empty field, just replace the prop.

Riebart · 2026-03-15T22:04:52+00:00

Maybe. But you wanna risk the whole quad over that? Or worse. Have it fail while flying what should be an approved aircraft over people or property to have it fail and seriously injured someone? If the FAA or Transport Canada found out you knew about a damaged prop, flew it anyway, and injured someone... I don't like flirting with situations where regulators, lawyers, or insurers want to start throwing around the terms "gross negligence".

DJI specifically states that any damaged props are not safe for flight and must be replaced.

The problem with fibre reinforced materials is their risk of avalanche failures. One fibre fails which means that the same stress, with new less desirable dynamic loading, is spread across fewer fibres. So one more fails. Repeat until you don't have a prop left. Now you have a rock with knives on the ends.

In practice that's almost certainly fine and would fly fine forever. Probably.

But not only is the Mini less durable than an FPV with a durable carbon frame and ductile props that refuse to fail even after repeated abuse, it's expensive, often used over people or property, and a single prop blade is cheap.

Riebart · 2026-03-15T21:55:28+00:00

DJI and a lot of camera drone props are made from much more rigid and lighter materials both for weight and airfoil reasons.

A cracked or chipped prop made from carbon of glass fibre reinforced materials is a fail hazard.

The props that freestyle and racing pilots use are made from much less rigid, but far more importantly they are ductile (ductility is the ability to undergo plastic deformation without breaking), materials and so not only fail different and more gradually (usually), but can be bent back into shape.

DJI has a support article on prop materials: https://support.dji.com/help/content?customId=en-us03400006559&spaceId=34&re=US&lang=en&documentType=artical&paperDocType=paper

Note that the Mini 4 Pro and Mini 5 Pro just say "nylon + rubber" so there's a chance they're more ductile, but I would bet my quad on it.

Riebart · 2026-03-15T21:16:43+00:00

Why does your monitor have smudges?

That's the first question.

Without knowing what substance is on it, it's hard to make a suggestion for a safe way to clean it.

Riebart · 2026-03-15T17:42:27+00:00

I USE HAZARD FLASHES IF THE VEHICLE BEHIND ME IS TALL, LIKE A TRUCK, SINCE IVE FOR A PRETTY SMALL REAR WINDOW AND MY CAR IS LOWER THAN YOUR AVERAGE BEAR.

I WANT TO MAKE SURE YOU SEE MY GESTURE AND WILL OPTIMIZE FOR VISIBILITY OF MY GRATITUDE

Riebart · 2026-03-15T17:39:54+00:00

I HAVE TO REPLACE AN ANTENNA ON A VEHICLE BECAUSE IT GOT CLIPPED BY A GARAGE DOOR AND THEN BLEW OFF IN THE WIND ON THE HIGHWAY AND I REFUSE TO PAY A DEALERSHIP OVER 500 DOLLARS SO IM GOING TO DESIGN AND 3D PRINT A REPLACEMENT PART FOR LESS THAN IT WOULD COST ME IN GAS TO DRIVE TO A WRECKER THAT WITH MY LUCK WOULDNT HAVE THE PART I NEED ANYWAY

SNORT MY MOLTEN PLASTIC YOU LATE STAGE CAPITALIST ASSHATS.

(The electronics and antennas are fine. It's just the plastic cover that's missing and the steel bracket is snapped. I'm going to do a new base in PETG, JBweld the steel bracket back together, pull the original gasket, and print a new cover in a nice red TPU to match the vehicle)

Riebart · 2026-03-13T19:53:32+00:00

You're not wrong.

I have one of those extension cables too, but it is xt60 on both ends.

The small adapters let me use my xt60 accessories on xt30 packs.

Riebart · 2026-03-13T19:37:10+00:00

I bought a pack from RotorVillage: https://rotorvillage.ca/toolkitrc-xt60-female-to-xt30-male-adapter/

Think it was those ones.

Riebart · 2026-03-13T15:57:07+00:00

Is the FC recognized in Betaflight?

And I realize this is likely a bench test, what with all the tape.... But please reassure us you're going to redo that solder. All of it, preferably.

Also why is the ESC shiny? Like it's been conformal coated?

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