3DR Y6B w/Pixhawk won't take off for first flight

Log Analysis -- deprecated Copter Logs -- deprecated
1

I just bought the 3DR Y6 kit with Pixhawk and Ublox GPS. It is setup in the Y6B configuration with 10 4.5 rotors top and bottom. Running Mission Planner 1.3.7 for programming. Firmware is Arducoptor V3.1.5 Y6. Setup Y6B configuration in the wizard. Motor order and direction confirmed using the CLI and motor test.

After following the assembly documents, several times running through the wizard and hardware configuration I found one ESC was bad because the #4 motor wouldn’t turn. The ESC was replaced and then re-ran all of the checks.

It was finally time to make the first flight, and I noticed that Motor #2 calibrated fine, but with the rotor on it, it required more than minimum throttle to start while the other motors spun up just fine.

In trying to take off, the front right side always stayed low. While I couldn’t get off the ground, the entire thing would rotate and eventually flip while still on the ground at full throttle.

After verifying the motor numbers and directions for the 100th time, I assumed it was an ESC problem, I recalibrated them. Still no luck. Then I went through and calibrated each individually.

Still, the same problem. The arm with motor #2 seemed to be underpowered.

Then I switched the ESCs going from #1 to #3 and #2 to #4. Still had the same problem, motor #2 seemed to be weak. Problem stayed with motor, not ESC and Pixhawk assumed frame location. I switched everything back to the correct motor positions. Without blades, I can easily stop the motor with just a little pressure applied to the housing with my finger. The other motors can’t be stopped easily this way.

Looking at the logs, the power for the top motors (odd numbered) look like they have reduced output signals. Motor #2 looks like it has the highest, but all even numbered motors are mostly at max.

When I put throttle to max quickly, the coptor will try to take off, but flips about 6 inches off the ground.

Does this look like a motor problem or some configuration and calibration problem so that Pixhawk is telling the system to reduce power?

Looking at the #2 motor, the output signal is maxed out. #4 and #6 are slightly lower. #1, 3, 5 are much lower and are dropping as takeoff starts.

Log #15 and #17 both show this. I was playing some with roll, pitch and yaw to see the response as well.

2

If you can stop the motor with your fingers, it’s a motor or esc problem.

Since it has redundancy, it’s possible that it could fly with a motor out like that, but also possibly not because the Y6 tends to be front-heavy. Regardless, it almost certainly won’t be doing it with the roll and pitch gains you have now.

Definitely get a replacement for that motor (contact help@3drobotics.com)

3

jschall,

Thanks. I have been using all the default settings so I assumed it should go even with a weak motor, but I guess not.

I ran the motors and held it up, then tipped the right side down and while the motors did speed up, there was almost no extra power. If I do this to the left, the motors compensate and push really hard.

There is a small “ringing” noise or almost ping that occurs when the #2 motor speeds up or has added load, it sounds like the motor is the problem. Once I replace it I will post a follow-up.

4

Got a replacement motor from 3D Robotics and that fixed the problem. Quick test flight this evening after swamping motors and instantly it took off and was stable.

It has been a frustrating build as first an ESC was bad and then a motor off a brand new kit. Now it appears to be working well after replacing parts.