Quad crash with "non damped mode" disabled

I just had a failed first flight of my quadcopter. I realise in hindsight I had the BLHeli “non damped mode” disabled, which… am I right in thinking I should have had it enabled?

I invite opinions as to what happened in this crash here:


Thanks for any help and tips!

I couldnt get non-damped mode to work properly at all when I tried.
You just need to disable Low RPM Power Protect, and probably the low voltage cutoff and ensure your FC can accurately measure battery voltage and act on it.

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I’ve put the settings I used for the crash below (they were the ESC defaults):

I don’t think it had anything to do with that. I always have it at default. Flight logs >> Video. Shawn’s certainly right about Low RPM PP.

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List your ESC, motor, prop and lipo setup, and a screenshot of PIDs from “Extended tuning” in MP.

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I have self tightening props which I had just attached so I think it is possible that the quick slowing down of the motors with the disabled non-dampened mode would cause unresponsive thrust from the props when slowing down, and again when speeding up due to prop slip.


MT 3515 650Kv

Prop is 13x5 CF.

PIDs are default Ardupilot ones.

If it’s on 4S, the setup is decent and should’ve hovered without too much fuss. It’s been a long time since I flew my quad with 710 kV and 12x5, but it used to be a decent sporty flyer.
A .bin logfile would’ve helped, to see your reactions on controls, other then throttle, if any.

But, from the short video, that’s not a landing gear. You need something sturdy, no matter how well the drone flies. And wider… mount it underneath the motors, so it maybe saves props from striking ground. And you don’t carry actual payload until it flies well, rather carry a piece of “something”, metal maybe, of the same weight, ziptied to the frame. Oh, and help the ESCs with some quality electrolytic caps. Even if BlH32 lore says caps are needed only for 6S operations, and 4S can do without, I never flew one without upgrading whatever crap the chinese provided with a quality Nichicon low-ESR cap.

Oh, and this close to the ground, there’s a thing called ground effect that wreaks havoc with your controls and autopilot response. 2m height is where I always bring a new build to check its behaviour.

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It’s a 6S setup. It’s good to hear that your large quad flew well but I wonder if you had the damped mode disabled in BLHeli?

Also, did you use self-tightening props?

I have one large capacitor on the input to the PDB, but no other capacitors apart from that. Maybe I need more?

I know things are a bit crazy with ground effect near the ground, you’re right, but it didn’t seem quite right when I was just off the ground so I aborted.

You’re also right about the landing gear. I will try and mount them further out near the motors. I’m not sure I can make it sturdy without making it much heavier. It is 3D printed. The payload underneath is quite tall which is why the landing gear is so tall.

Oh, 6S. You’re in trouble. For starters, your motor kV is way too high. Or, your prop too big. Probably a 10x5 would work OK on your motor-lipo combo, but would drop your flight time to half, at least.

Second, you don’t BlHeli32 on 6S without individual ESC caps. Ever. Your flight was obviously very short to cause smoke-emitting events, but the ideea is of flying up tens of minutes. My experience is mostly watching other people’s movies with electronic stuff burning out, so anywhere between 30 seconds and 3 minutes of hovering at 2m altitude, one of the ESCs will let the magic smoke out and your quad will tumble down to a crash.

Third, a 3D print is extremely weak along the printing plane. It’s difficult to correctly print a landing gear as opposed to say a camera holder. Please use some carbon fiber until your quad flies like a dream, if it ever will.

So, details aside, the damped mode setting on the ESC will matter only after your quad flies well at full throttle for a couple of minutes. Before it does that, though, there’s some bad construction and choice issues in your build that a simple software setting somewhere won’t solve. Sorry.

My advice is get a 4S LiPo. Simplest change, and your drivetrain is probably close to optimal with it. Mount the caps on the ESCs and build a sturdy landing gear for your noob landing mistakes.

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I have used self-tightening props before and never seen that happen. I did see once a prop spin off after it landed because “break on stop” was enabled. Personally I would get rid of the self tightening props.

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Dave, there’s props, then there’s the Graupner E-prop. Which comes in central-screw mounting, only. I’m not familiar with the sub-7" stuff people are flying nowadays, but back in the day E-props made for sporty screamers running the purple board.

I’m sticking with 6S for efficiency. I have designed it around the thrust tables for this specific motor which gives me max thrust at 6S and 13x5 prop. I’ve dealt with 3S and woeful efficiency in the past.

The fact that one of the props kept spinning after landing tells me that the damped mode was definitely an issue. i.e. it span the restraining nut loose with the motor spindle static.

The only motors I could find were self-tightening (or was it the props?). Anyway, I was restricted in where I could purchase this setup.

BTW, the 3D print issues don’t bother me. I’d rather the impact be absorbed by crunching sacrificial plastic.

I’ll get looking at some ESC caps, thanks.

I made a mistake. They are 13x4 props. Here are the thrust tables showing the combo I am using:

I wish I could but I couldn’t find any other sort of 13x4 props which is what I need. Is there any other type of prop attachment at this size of prop?

Don’t those motors accept T-type props? 1st choice for me by a long shot. I have 13” T-type props on a quad. Robust mounting, high torque cababilty and easy to fixture for balancing.

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Looked like lots of instability in that take off attempt. Have you had any successful take offs?
Have you got a .bin log file or even param file?

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They come with a 2cm diameter disc that has 1 large hole centre, and 2 smaller holes either side. One side of the disc has a pattern on it to make it rougher. No idea how it grips the motor though.

The center hole is a pilot, great feature, the other 2 holes are for screws. These are in shear under torque. The “washer” clamps it all. Can’t beat it, buy some.

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Here is a photo. I am not using the disc at present, just the silver nut.