Motor Failure on First Flight

I was hoping this first flight post was going to be something to celebrate after many weeks of testing to ensure I had all the calibration and IMU feedbacks correct.  However as I hope you can see in the video I lost the right motor which caused my quadcopter to flip and land smack on my expensive UBlox GPS. Ouch!  At least the new high rise legs from Jani look pretty nice against the blue sky.

 

I have checked the logs but cannot see anything which would suggest an APM issue.   This unfortunately was an expensive crash, destroying several motors, props, the frame arms and too many components to list.  A tip for the new guys like me into this great project, don't fly over a concrete driveway :-)

 

I am still puzzled at the crash and this is the second motor failure in the past 2 weeks.   I am using the 880KV with 12x45 props, 30A ESC's  I have found the motors are not very durable and wonder if there is a better alternative.  In the post crash testing I  checked the motor which stopped abruptly during the maiden flight and it is cutting out when I move the motor around.  Yet all the others do not demonstrate this behavior on the same ESC and wiring point on the power distribution board.  

 

For my Quad design I had in mind to get a little more pay load hence the larger 880Kv motor and 12 x45 props.   The arducopter is built from parts I source from the arducopter suppliers.

 

I have also noticed some tolerance variability in the prop mount hardware so I have to be careful when tightening the propellers to make sure the props run true.

 

Any suggestions on higher quality / more reliable motor alternatives which have been tested on the ARDUcopter frame would be appreciated.  I just want to focus now on building more reliability into the design.

 

First_Flight.MOV

IMG_1613.MOV

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Replies

  • So a week or so on I have rebuilt my ARducopter quad and had some good test flights this morning. AN interesting aberation I cannot explain is the same motor position running off pin 1 on the APM started to beep regularly before I armed the system. The arming was ok and all motors run in sync. I spent several hours yesterday doing manual calibration of all ESC,s The motor hich failed a week ago is replaced and as. precaution I replaced the ESC. Everything ran perfectly in sync, arming good as well. I seems to me there is something intermittment or some signal noise on pin 1 of the APM. I am running 2.0.37 which I understabd is the most stable version at the momment. Has anyone else expeirenced odd behaviour like this on startup with PIN 1 signal to the motor? I is most bizaare. My quad is flying well is very stable. It is just I worry when I cannot explain the beeping on that one motor before arming. I powered done the system and went through a startup again and now sound except for the expected initial response from all four motors. Hope someone has had some similar issue and can give me some advice on the APM signal to the ESC. I other words is this a normal artefact which occasionally pops up or may be code related to the verison I am using.
  • It interesting that the quad only seemed to tip to about 45 degrees after the failure - before impacting the concrete. Why did it not pitch right over? It may be that it reached the tilt limit (45 degree I think) in stabilise or simple mode control laws.

    What mode were you flying in?

    Makes me wonder if the control laws could be modified to detect this sought of failure and some how maneuver to try an keep the arducopter right side up while heading for the concrete - better to land on the legs hard than upside down or side on

    -Andrew

  • Are your motors hard soldered to the ESCs?

  • Developer

     

     

    I'm using AXI 2814/22 and 40A opto ESC from Hobbywing. As they are opto, you will need an external BEC to power the electronics. I rely on Castle Creation BEC for this.

     

    This is a quite powerfull setup to carry heavy loads. Not sure you need this on the base frame and i think the fixation is not the same width. But you could use smaller motors from AXI.

     

    AXI are expensive but they have a more serious design with 3 roller bearings instead of two on Pulso for the same motor size and better quality checking. On the Pulso, i've found that when they are hot, i have some radial play in the shaft. This mean that the roller bearing adjustment is not ok.

     

    As i plan to put an expensive camera on the frame, i couldn't tolerate that level of quality and i prefered to spend a bit more for motors.

     

    There are higher end motors than AXI, but AXI seems to be a quite good quality / price ratio if you want enhanced reliability.

     

    Do not forget that good ESCs and perfect wiring is 70% of the success. I would recommand to test the setup on the ground during a couple hours, with many motor start, stop, slow and fast throttle ramps, to be sure that everything is correct and can support max load before to fly.

     

    The only thing you should never do with sensorless ESCs when testing, is to stop motors and start them when the propeller is still rotating slowly. In this case there are great chances you'll have a motor stall, and eventually a motor destruction if you are using low cost ESCs without current protection.

     

    This is because backEMF fields are too weak when the rotation speed is slow, causing a false synchronisation between motor and ESC.

     

    I think that the best is to program a switch on the radio to be sure that you can't stop motors after start. The same switch can be used if you need to stop motors urgently.

    For this i used the throttle cut function set at 0%, and i reduced the EPA (end point adjustment) to 80% for lower end part of Ch3. So when the throttle cut switch is engaged, your motors can't start, but you can Arm or disarm them because throttle is locked at 0%. When the throttle cut switch is disengaged the minimum PWM value is never less than 20%, so you can use the throttle  stick normaly, the motors will never stop, and you will not be able to disarm them accidentally during flight.

     

     

     

     

     

     

     

     

  • Developer

     

    Did you check the max current you have at full throttle ? If not then connect a wattmetter and see if you are below the recommanded values.

     

    If you are too high, then lower your batterie voltage (switch to 3S if you are at 4S) or use smaller propellers.

     

    I'm using AXI motors. Expensive but well manufactured and with good quality roller balls. I don't go over the recommanded max continous current. I tried Pulso as well, but in the end i choosed AXI for roller ball quality. Pulso did have noisy roller balls. Magnets seems stronger on the AXI, detents are cleaner.

     

     

     

     

  • where are you use voltage 5 v connect to on APM? (you're use on ESC's motor failure or UBEC)

  • Hi Greg

    I've always used AXI motors they are the best but expensive, they are well made, reliable and efficient. However, I have recently switched over to Pulso motors, they are AXI rip-offs , they are equally well made and work exactly the same. They cost half as much as AXI.

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