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ModeratorPermalink Reply by Dean Wynton on July 8, 2012 at 12:41pm

Just looking at the H6X, will that landing gear take much abuse or weight? before it breaks or the camera tray hits the deck? hard to tell from a picture.. :)

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Permalink Reply by Duran - SteadiDrone on July 8, 2012 at 11:29pm

Hey Dean. The landing gear legs are stiffer than they look :) very strong and we've not yet had any issued with hard landings.

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DeveloperPermalink Reply by R_Lefebvre on July 18, 2012 at 12:33pm

Bumping this back up...

So I was looking at getting an Octocopter because of the redundancy, being able to stay in the air and not crash if a motor or ESC failed.  For aerial photography obviously.

But then I recently heard that staying alive with a lost motor is not guaranteed.  Apparently the DJI units crash anyway.  But Mikrokopter can survive.

Does anybody have any example of Arducopter Octos being able to fly with a motor failure?

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DeveloperPermalink Reply by John Arne Birkeland on July 18, 2012 at 3:57pm

If a motor just stops spinning or if the propeller comes lose and just flies away, tests done by other people show that octos and even some hexa's should be ok. But in the real world electric motors usually don't die very gracefully and could result in power problem for the rest of the system. Another more realistic scenario is that the propeller drops a blade. The motor continues to spin, and the now very, very unbalanced propeller makes so much vibrations that the IMU becomes useless.

Below is perhaps the worlds longest lasting multicopter crash for entertainment value.. :)

http://www.youtube.com/watch?v=6rirlbjEk20

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Permalink Reply by Duran - SteadiDrone on July 18, 2012 at 11:09pm

Hello again, while building, testing and flying our octos over the last year, we've had one or two times when a motor would stop, once it was becase it was not plugged in, and the other can't remember, but both time the octo flew like i was not even aware of one less motor, I've also removed a prop all togtehr and taken off, I can do this again and shoot a short video if you like.

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DeveloperPermalink Reply by R_Lefebvre on July 19, 2012 at 6:53am

Thanks John.  Yeah, I know throwing half a blade is a big problem.  How often does that happen?  I've never ever had a prop throw a blade in 20 years of flying airplanes.  But it seems like the props I've been using are WAY more robust than these flimsy things on my quad.  I wonder if the problem is somewhat using Slow-fly props in a manner that was never intended by the manufacturer?  We're taking props meant for a 1 lb plane to cruise around a park, and then overloading them and spinning them too fast?

Would it be foolish to put a fuse on the power fed of each controller, such that it hopefully can't take down the rest of the power system if the ESC shorts?  I guess the problem is the in-rush current when you plug the ESC in.  But that can be solved using a "fire extinguisher" circuit, or anti-spark.  A positive line with a resistor in it that you connect before you connective the main positive line, charges the caps at a controlled rate.

What happened in that video?!  I couldn't really figure out where the problem arose, because it looked pretty bad as soon as he lifted off!  Did he hang the camera from a rope or what?!

Duran, I'd love to see some stuff like that.  Though, there is a difference between taking off with a prop missing vs. losing it mid-flight.  Taking off like that allows the APM to adapt before it gets very high.

A better test would be to rig up a FET into the signal line of one of the ESC, and then shut the ESC down mid-flight.

I would really really love to see some stuff like this!

Guys on other forums are saying the DJI units can't handle this at all.  

Obviously power/weight is a huge part of the problem.  If the copter simply doesn't have enough power with effectively 2 motors gone (because we have to shut down the opposing motor), it will have a problem.  I think some poeple are building large Octos, but then sticking huge cameras on them.

Anyway, if I saw some definitive proof of you flying with a disabled motor, it would help me make the decision to proceed, but I would build it over-powered and still with a light-ish camera.

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Permalink Reply by Brad Hughey on July 19, 2012 at 7:44am

Even though I don't "have a dog in this fight", that's never stopped me from having opinions.  ;-)

Unless there's an accidental strike, props should never fail.  If they do, then you bought the wrong ones.  I can't fathom that someone would choose to put $2 props on a $1,000 EMC (with all due respect to the data storage company, Electric Multi-Copter has become the generic term for these devices).  I've long held that commercially-available propeller technology for EMCs has seriously lagged the rest of the art.

I fuse my motors and consider it a best practice.  The way fuses are rated, a 60A fuse will pass 60A forever.  If you exceed 60A, the duration before interruption varies in inverse proportion to the current overload, with some fuses taking several minutes to pop even at 120A (2X rating).  The spike inrush to charge the main capacitor won't be a factor in the vast majority of cases, even with "quick blow" types.

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DeveloperPermalink Reply by John Arne Birkeland on July 19, 2012 at 2:56pm

I think the reason we have propeller blade drops with multicopters, is related to wanting big propellers for lift but at the same time as lightweight as possible to make it easier to change the rpm quickly. Some of the new CF multicopter propellers are much to thin for a traditional plane. For example my 15" props are 14g each. On a proper rigid carbon fiber arm, and with balanced motors that is no problem. But if the arm is to flexible and the motors are unbalanced then you can get into problems. And of course, some of the cheap plastic propellers are just crap no matter how balanced everything else is.. :)

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DeveloperPermalink Reply by John Arne Birkeland on July 19, 2012 at 7:49am

Regarding the video, I have no idea what caused it. But my guess would be electrical wiring problem causing brown-out's combines with wrongly set failsafe (full throttle, camera gimbal pointing in the sky etc.).

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DeveloperPermalink Reply by R_Lefebvre on July 19, 2012 at 7:52am

Well, whatever happened, it certainly was as you say, the longest multicopter crash in history. 

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Permalink Reply by tristan price on July 28, 2012 at 3:47pm

hi all, been reading this thread with much interest. Finally here is somthing i can add. i,m flying a hexa, and have recently been flying with a lot of weight. As a result i have suffered 2 mid air prop failures, followed by the motor being riped of it's mount. Thr craft has a momentry drop but then recovers fine, however it quickly starts to yaw , faster and faster. Now if you can switchin to simple mode you can get it back, but you need to land fast. This is with a hexa, i'm guessing the yaw affect would be much less with a octo. 

  So yes arducopter will fly with one motor out.

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Permalink Reply by Duran - SteadiDrone on July 19, 2012 at 8:25am

two words, 'APC props' they are by far the most reliable and strong props, we've never ever broken a single prop or had any trouble mid air (apart from the odd prop broken due to HUGE crashes)

APC, the best.

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