3 Crash in sequence - ALL HELP NEEDED PLEASE!

Cube Autopilot
#1

Hi everyone, I had 3 crash in sequence and I don’t know what else to do, I really need all help possible to analyse my logs and help me to find out what the problem with my drone.

First things first, my HEXA has a Cube FC (bought from irlock), RFD900 telemetry, L9R receiver, mauch eletronics (bec and current sensing), here 2 gps (i2c mode) and other 6v bec to power external servos. My motors are tmotor mn501-s kv 240, tmotor air esc 40A with 20" CF propellers and 6S 16A Lipo.

My problems started at my first crash, I was running in auto mode when in middle air one wire of one motor just broke, the copter tried with success to stabilize, but, I was flying above high grass and when the copter just stabilize it was literaly in the ground and becouse of the grass or something else, two propellers was out and I lost telemetry and radio at same time. I thought that the drone will turn off itself, but after 5 minutes I reached the crash place and all motors was running in full trust and they got extremelly hot, so hot that I’ve burned my hand instantaneously. (Copter version 3.6.12)

After this crash I fixed all problems and flew again and one problem appeared, I was in auto mode and the copter flew in straight line but the YAW was spinning, I never saw something like that. I did 3 attempt but in all flights I had the same problem. When I was on loiter I havent had any problems. (Copter version 4.0.2)

I thought that was problem with the firmware, so I downgraded to 3.6.12 again and did a test, everything was fine in loiter so start my tests and I moved the roll to right and left quickly, to check the stability and the copter just cant stabilize, I did the roll side to side just 2 times and stoped to se it stabilize, but it couldn’t, the copter keept doind the roll side to side without stop and this time started to go up and I lost the control, I couldn’t bring it back so I turned off the motors and I left crash into ground.

I really dont know what is wrong if my copter, I suspect of two things. In my first problems, my motors got extremelly hot, maybe there’s something wrong with them or with my escs, couse’ they should be hot as well. Its weird becouse after this crash, I used the same motor and esc and I done the other crashs, so esc and motor was functional.

Hope you guys help me!

All telemetry and FC logs are here: https://drive.google.com/open?id=1XjdOBHHxnJyXG6subA_WZss7XU2myDN2

*In first telemetry log, the problem occurred at end of log.

#2

if you overheat a neodynium magnet from which are created the AC motor rotor poles they are demagnetizying at temperatures above 100C on poor motor a bit higher on high quality motors. the reason of spinning will be probably insufficient thrust on one of them… but I try to look your RC OUT values than I tell you for sure…

but you definitely damaged or decreased life time of your motors.

#3

your compass is a bit shifted that maybe caused the AUTO crash… regarding the RCOUT its a bit messed the motors are fighting to each other and you have vibrations above 30 but no cliping. what is a bit sh. t is no crash detection enabled thats why your motors was turning after crash…

i think your motors are damaged due to heat pernament demag… but maybe somebody else say more.

#4

First, thanks a lot for your help.

About the compass What I can do to fix it? This copter is the same that i’ve been using for 2 months every 10 hour a week, same configs, same calibrations, no problems at all…

The crash detection didnt arm becouse the copter was perfectly horizontal, seems like it landed.

To fix the motor is easy, just replace, but how can I be sure that it is the problem? What you think about my ESCs?

#5

the crash detection is not only about to be horizontal… as well it detects if the vehicle is not stucked and able accelerate more than 3m/s/s so the crash detection is a bit more complex. regarding the magnetometers a good practice is to recalibrate. i suggest to do it every week… bcs by vibration can move orientation and etc… in 3rd flight you have definiteli disagree between mag meter…

#6

yes your FS_crashcheck - is 1 so it was set ok. that strange why it was not disarming.

regarding motors. All overheated motor are downgreaded… the magnets are permanently damaged. It can be more sensitive than for heat and it can loose its magnetic field rapidly in flight leading to insufficient thrust momentarly and after cool down it can regain better mag field… I experienced this 2816 750kv motor on fixed wings.

best is to replace them I suggest but if you have high quality motors maybe they withstand more heat but generali neodymium dont like high temps…

#7

Thanks for you help.

In 3rd flight I recalibrated the mag, accel, everything minutes before the crash, I dont know what went wrong. In this flight only, I was using dual here 2 gps, both i2c and internal compass as well.

About the motors they are t-motors, maybe the best in market, but I will replace them.

What about the ESC’s, maybe they got bad too?

#8

About the crash detection, I tought the copter will shutdown, becouse I lost all comunications, so I tought was a crash, but, the motor was in full trust when I reach the crash place. What you think went wrong to the copter not shutdown?