Motor or ESC?

[Bashedcrab]

Hello all, iv'e just completed my DJI f650 Build and i have just run into a bit of a problem during a test flight.
I had just flown around my property and everything seemed to be ok, the gains were off and there was a lot of jello in the footage (nothing that cant be fixed with fine tuning) but otherwise it flew just fine. I landed it and did a few landings and take offs to test the motors were spooling up properly and to test if the quad took off cleanly without pitching into the ground and flipping. Then I bounced the hex on the ground to test for any loose connections etc by quickly running the motors up to 100% and down to 0% allowing the copter to drop from just under a foot.
This is when I ran into the error, after a quick run up and drop, one of the props stopped turning (M2), at first I thought some debris might have found its way into the motor or a bearing had seized as it was stiff to turn by hand. So I gave up on the testing and disconnected the batteries and took the model inside, once inside I realised the motor was spinning freely again and worked perfectly when connected to power and i can't seem to replicate the problem again.

I figure I can't fly until I figure out the problem because I could cause a lot of damage with a mid-sized hex if it malfunctioned in mid air.

If anyone can give me insight on what to look for and how to properly test the components involved it will be much appreciated. Also I apologise for the long-winded explanation, I just believe in giving as much info as possible.

My Hex configuration is
Frame: DJI F550 expanded to 650mm with aimdroix arms
Motors: Quanum MT series 3508 700kv
Props: CF 1205
Flight Controller: DJI Naza M V1 with V2 PMU and IOSDmini
ESC: DJI 30A 3s-4s 30-450Hz
Batteries: Multistar high capacity 5200MAH 10c X2
Video TX: Immersion RC 600mw
HD video: Sony HDR30ASV Actioncam

I have also attached pictures of the motor/esc install

 

[fltundra]

You get the quality you pay for, cheap motors will cost you more in the long run.

 

[tstrike]

Check for cold solder joints and stop dropping your hex, Newton already proved the theory of gravity.

 

[Bashedcrab]

lol don't diss the drop test. It did reveal the fault on the ground rather than 400ft in the air. I suspect the fault was exposed metal on the bullet connectors from bad heat shrinking contacting the sides of the aluminium arm. When the hex touched down hard it must've caused things to shift around and cause a short circuit through the frame.

Thanks for telling me to check the connectors tstrike!!!!

 

[Bashedcrab]

Happened again 150 feet in the air. I didn't crash though, the naza kept things in the sky until I could figure out a good landing approach for the paddock I was in. It was tricky as I had no yaw and the hex was far away so visual orientation was difficult, but I got it on the ground safely in the end, I think it's a real testament to the work that goes into even the simplest of controllers we use, and definitely not a testament to my workmanship!!!!

 

[Carapau]

Not sure on the motor issue but if you loose a motor in mid flight again, flick to home lock and then you dont have to worry about orientation, even if the aircraft is slowly spinning which can also happen on a motor out, the home lock is your friend.

 

[Bashedcrab]

I did think of using home lock but I wasn't sure what effect it would have on a malfunctioning vehicle. On further inspection one of the bullet connectors had appeared to come loose. That being said, in my experience a bad bullet connector will cause a motor to twitch rather than seize completely. I keep a couple of brand new escs in my crash bag so i'll swap that out tonight as well and see what happens tomorrow.