End of a two day shoot and had a motor failure.

[Benjamin Kenobi]

Hi everybody,

So I was in the last minute of a two day shoot and one of my motors failed on my S800 at about 50m. Well, it kind of failed. Stopped for two seconds, came on again, then off for two seconds, then on etc. I was quite surprised when a prop just stopped, especially since the S800 just held position and I still had full control. When the motor kept coming on again it caused a quick roll but levelled off instantly. I landed safely in the designated landing area so all good.

But now on the bench I can't recreate the fault. I had assumed a loose connection in either the ESC or frame hub or an ESC that was on it's way out. Left it running on the bench and no problem at all. Temperatures all equal and motor RPM stays constant. I tried flexing the arms whilst running and various twisting motions incase it was a loose connection in the wiring but all good.

What's my next course of action? I intend to replace the entire arm and ESC as a precaution. My S800 has had over 100 flights since April and I imagine wear and tear are starting to show up.

I'm so glad the failure happened at the easiest part of the shoot. I had been flying over sheep herding, expensive race horses, tractors and buildings as part of the shoot but when the failure happened I was just filming an empty walled garden with no one around (except my crew who were well impressed how I handled the incident!).

The logs show motor 6 cutting in and out. If you want to look at them just ask and I'll post.

Any sensible suggestions as to likely causes? I vote for an ESC problem.

 

[OneStopRC]

I have seen FC doing weird things, sometimes after a power cycle they play nice again. Certainly sounds very weird, hope you isolate it soon.

 

[DennyR]

Ben
There was a spat of bad connectors from the Rx cables to the center plate with many of the earlier S800's that cause such a problem. resoldering can eliminate that.

 

[QuadroPilot]

Ben
There was a spat of bad connectors from the Rx cables to the center plate with many of the earlier S800's that cause such a problem. resoldering can eliminate that.

Would that still be an issue since the problem didn't present until after 100+ flights?

 

[Benjamin Kenobi]

I'm still looking into the problem. Really can't replicate it on the bench. I'm using firmware 5.22. The only difference with this last shoot was we carried it around by the arms all over the place and in the back of small cars. I really thought it might be the frame arm mounting points but they seem solid. The rx wires are perfect also.

I'm still bloody impressed I had so much control after losing a motor. Everyone is always going on about 'get an octo for redundancy' I thought the S800 would spin to it's death. But no, blade stopped, I landed, even with the motor cutting in and out every few seconds which did scare me as it rolled quite a bit but levelled quickly.

Just uploading some clips from the shoot. The client was jumping for joy with the quality!

 

[Benjamin Kenobi]

PS - Does anyone know where I can get a complete CW Green LED S800 arm in the UK. All the usual suppliers are out. I think it would easier to make a claim in the event of an accident if the manufacturers done all the soldering and not me. They can't use the 'user modified' get out clause I've heard people using.

 

[Benjamin Kenobi]

Here's some clips from the shoot, not graded or anything, just cut and paste:

Cheers!

 

[deluge2]

Wow, for once Murphy Law didn't come with full complement of corollaries (like 'at the worst possible moment...'). Doesn't sound like FC issue since it appears to have handled the intermittent loss of 1 motor admirably. From DJI's video showing flight with simulated loss of 1 motor, the craft showed significant yaw, which it appears you did not experience. Can you estimate the duration of motor off and motor on periods once the malfunction began? Hard to imagine the FC getting screwed up enough to shut off 1 motor, but not enough that it couldn't still maintain proper attitude. Also I imagine an examination of the log by an experienced eye would support that the FC was operating nominally. Frustrating that you can't duplicate the problem on the ground though. I agree with your presumptive diagnosis that it's likely related to components on the affected arm. So the logical thing is amputation of the offending limb. Regarding the LED color, I was just thinking tonight that it's too bad DJI didn't use a modular mount so that one didn't have to match both rotation direction and LED color to get a complete factory replacement arm. Might want to take a very thorough look at the electrical contacts on the frame for that arm including both mechanical factors and integrity of all solder joints. There have been previous s800 pilots reporting that the take-down joint parts do wear out. May want to consider pro's and con's of replacing the Arm Mounting Bracket on the frame for that arm. You may be against this based on your warranty claim concerns. I suppose that might be solved by having your dealer do the replacement during some down time.

Anyway thanks for sharing your experience with this so far. Look forward to any other information that may shed light on this event.

Steve

Hi everybody,

<snip>

The logs show motor 6 cutting in and out. If you want to look at them just ask and I'll post.

Any sensible suggestions as to likely causes? I vote for an ESC problem.

 

[FlyGirl]

Here's some clips from the shoot, not graded or anything, just cut and paste:

Cheers!

Nicely done Ben! Although you probably should have helped that guy with the sheep herding Glad the motor issue didn't cause a complete failure...!!

 

[SamaraMedia]

Really nice work Ben, steady and smooth. Glad no catastrophic crashing with motor failure.

 

[Carapau]

Nice stuff Ben. I'm always amazed at how calm horses often are with an MR buzzing around given that every now and then they spook at their own shadows! Not sure as to what was causing the motor dramas but it can only really be a loose connection on the ESC to WK side or on the power side. My vote would be on the ESC to WK side.

 

[Benjamin Kenobi]

How would I share the IOSD data with you guys? File size is too large for normal forum upload (32Mb).

 

[DennyR]

Would that still be an issue since the problem didn't present until after 100+ flights?

Corrosion or vibration could open the circuit. I would check everything and then run it tethered between two chairs for an hour or so. Leave it free to rotate in roll and then in pitch. Run the motors from a PSU

 

[Stacky]

Nice stuff Ben. I'm always amazed at how calm horses often are with an MR buzzing around given that every now and then they spook at their own shadows! Not sure as to what was causing the motor dramas but it can only really be a loose connection on the ESC to WK side or on the power side. My vote would be on the ESC to WK side.

I thought horses would be calm when I flew near some but I spooked them and they all ran for it, some kicking out even though I wasnt very close. Wont do that again.

 

[maxwelltub]

I can't find it now but there was a video of someone flexing there arm and having the motor stop. They had it running with no prop and when he bent it a certain way it would cut out, and then when he release it it would start again. I'll keep looking for the video. Maybe this is a similar issue.

 

[Benjamin Kenobi]

That's the same video I saw. His ESC was also arming and disarming each time. Mine isn't. I'm actually quite sure it is where the arm meets the hub. The locking pin is loose compared to the others. I have more lateral movement in that one arm than the others. The movements are entirely normal when I swap arms.

As a precaution I will be replacing the entire arm and mounting hub.

On another note, I really want a Skyjib X4 with retracts! At the moment that is my dream rig.

 

[maxwelltub]

Ya a skyjib looks awesome. I am building a gryphon dynamic x8 and love it so far.