Monday, July 21 2014
Some of you may have wondered why the lack of posts over the last few months. One of the reasons is for a flood of other work that I had to attend to but the other was due to this accident we had here with the x8.
After it happened we were left scratching our heads and heavy hearts as to why this happened. This was during a weight lift test of 15lbs. As you can see, the motors on the front/right (stage right) stopped and the arm dips, not to recover. It happened so fast that we never noticed any heat issues with the ESCs via telemetry.
After some time had passed from the accident, a friend of mine with a similar setup had a similar problem with a similar ESC/Motor setup. His conclusion is that the TMotor U7s are under rated and pull much more power than on the spec. sheet. I also later heard from Maytech (ESCs) and they said that it was later discovered that SimonK firmware is not compatible with these motors.
If you look at the flight log data, you’ll see that the Wookong was doing all the right things. The IMU sensed the dipping of the arm and gave 100% to the arm in question in an attempt to stabilize. (I was in attitude mode.)
T-Motor now makes 70amp ESCs which we’ll most likely test. Up until this point I had never had an accident with a multirotor and suppose I was too cavalier to go about weight testing without doing extensive bench testing first.
Another thing I learned is to test at least over grass. Some of the motors were scuffed on the pavement and will need to be repaired if not replaced. All in all, about $1500 in damage.
Would love to know your thoughts on this. All things seem to be pointing to the ESCs not playing well with the motors but please do share any feedback you might have in the comments below.