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I'm at a lost here!!!

Discussion in 'Drone Builds and Kits' started by traxx2003, May 11, 2016.

  1. traxx2003

    traxx2003 Member

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    Mar 30, 2015
    California
    Posted by traxx2003, May 11, 2016 #1
    Hello everyone! First allow me to offer some details of my build and some details of the problem I'm having:

    Skyhero 850 X4 configuration
    TMotor 4120 400kv
    KDE 55AESC's
    SuperX controller
    17x5.5 CF props
    EZUHF control system

    My problem:
    I first attempted to use a Pixhawk FC with this build but after experiencing some issues with compass calibration errors I've decided to try a SuperX controller I already had. Below are some ofvthecisdues I'm axperiencing:
    - With both the Pixhawk & SuperX, the motors just sound like they are running at too low RPM. Tge hover is just not stable, the quad has a tendency to drift toward the right/rear (more pronounced to be just ATTI normal drift).

    -After countless attempts to get the gains dialed in with both FC's this think will not hover in a stable manner. CG is spot on and in line with FC.

    - With Pixhawk I noticed that both motors &ECS's ram much cooler after a 10 minute autotune / hover test flight. Motors & ESC's were 42 degrees C after a 10-15 min hover flight. With the SuperX the ESC's were super hot, could not keep finger on them for more than 2 sec.

    My theory is since I'm experiencing somewhat similar problems with two different FC's I could be dealing with faulty motors or ESC's?

    How could I troubleshoot a potentially faulty motor or ESC? Not sure what to do.
     
    Tags:
  2. Posted by John Doecliff, May 11, 2016 #2
    Just to clarify, have you done a throttle cal? Are those the right props for that motor? Consider trying smaller ones which will get you a higher rpm and possibly lower current. Assuming this is all good I would also check the balance of the MR. it shouldn't be heavy towards the back, front or side to side. I find it odd that all four ESC's are hot and would think that its something else rather then all four being bad at the same time. You might be right at the 55amp limit. Is the battery voltage rating correct for the ESC's? A clamp on amp meter might be able to tell you a lot, you would have to tether it to the ground to test it though.
     
  3. traxx2003

    traxx2003 Member

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    Mar 30, 2015
    California
    Posted by traxx2003, May 11, 2016 #3
    Well the 17" props may be at the top of the motors I have, but according to ecalc and current AUW=4987g, the motors at hover should run around 46% throttle during hover and at around 42 degrees C. This was pretty much validated during my first hover flight with Pixhawk. It's just that that FC I was constantly getting all kinds of error messages related to bad compass health/calibration and barometer errors which pretty much killed my confidence on that particular FC. I do have a replacement which I'll be trying out. But I'm not sure about the motors anymore or ESC's for that matter. As far the CG, on this frame the CG is not located at the center of the main body, but rather towards the back. I did however made sure that the CG is in line with the FC. This frame is asymmetrical so the CG is kind of a little of center. Is there a test I can do to check the health of the ESC/motor system. Also I did a amperage reading with an in-line amp meter between the battery and PDB and at hover I was pulling around 34-40 amps total. So this 55a ESC's are actually a little too much I think.
     
  4. traxx2003

    traxx2003 Member

    111
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    Mar 30, 2015
    California
    Posted by traxx2003, May 11, 2016 #4
    Almost forgot, I'm running a 6s batt on this MT, the ESC's are KDE Direct 55a, rated up to 8S voltage. They are 55a constant and 95a burst. I thing I will test run each motor separate connecting them directly to the receiver and see how the do.
     
  5. Hexacrafter

    Hexacrafter Manufacturer

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    Dec 11, 2012
    Cuyahoga Falls, Ohio
    Posted by Hexacrafter, May 11, 2016 #5
    Dumb question???
    How do the motor/ ESC act when connected directly to a RX? Full throttle range? Any strange noises/ loss of timing with rapid full throttle movements?
    Are you sure that KDE ESC play nice with T-Motor MN-4120- 400 kva??
    Seems like a strange match... why not T-Motor t60a esc .. the recommended ESC??
    Firmware & timing compatibility between this pairing is something I would question.
    Finally..... turn 17" with that motor is pretty aggressive... things are going to heat up!!
     
  6. traxx2003

    traxx2003 Member

    111
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    1
    Mar 30, 2015
    California
    Posted by traxx2003, May 11, 2016 #6
    Hexacrafter, I'll be testing each motor with RX later on this afternoon, to answer your question why this motor /ESC combination , I already had the motors and the ESC 's, I just got a really good deal on them. $50 each new, never opened. Honestly not sure if my problem is due to comparability issues with this setup. I figured people use motors/ESC's from different manufactures without issues so....... Regarding the prop size, my decision to go with 17" instead of 16" was based on ecalc data that indicated that given my current AUW-4987g and current setup (see first post) temp would be around 42 degrees c while at hover & throttle around 45%.
     
  7. Hexacrafter

    Hexacrafter Manufacturer

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    Dec 11, 2012
    Cuyahoga Falls, Ohio
    Posted by Hexacrafter, May 11, 2016 #7
    I am a BIG advocate of using & recommending mfg. matched or recommended pairings. I am not saying this to be difficult, but rather from experience. Each mfg. has specific differences on how they approach timing, esc refresh rates & waves. Funny enough when you have been around as long as some of us, we have even seen mfg. accidently create ESC that are not compatible with their own recommended motor pairing.... No Names Please.... When a problem becomes apparent, it becomes a finger pointing contest. .... T-Motor.... well we don't know anything about KDE ESC..... KDE.... we only can guarantee that they work with our KDE paired motor... and so on.....
    A few more comments from experience......
    IMHO.... you are pushing it with 17" props...... Most of the charts are BS...... Bench test it yourself & keep an eye on motor & ESC temps!!!!
    Flight Controllers are happiest (designed at 50%). We have tested down in the 30% range and things get weird.... sometimes very unstable and just weird....
    My suggestions.....
    Confirm motor & ESC pairing..... I think KDE run a firmware "similar" to simon K.... Simon ESC did not play well with the 45 series motors...
    Prop down to hover at close to 50%..........Not less than 45%...... confirmed in manual mode via throttle position... not e-calc..... or charts...
    Traxx.... just trying to offer suggestions from years of trials & tests...... learned a lot of lessons the hard way...... especially about motor & ESC pairings....... all seems fine and after 12-15 flights..... wham.....timing goes crazy after a quick gust and down comes the investment....
     
  8. Posted by John Doecliff, May 11, 2016 #8
    How can one be sure the pairing is correct? Is it on the motor spec sheet?
     
  9. traxx2003

    traxx2003 Member

    111
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    Mar 30, 2015
    California
    Posted by traxx2003, May 11, 2016 #9
    Hexacrafter, I really appreciate your inputs and I welcome any suggestion / advice I can get, after all this is how you learn. Besides the fact I already had the motors, the only reason I went with KDE ESC's was because one I was looking for some high end quality ESC's and second I got a good deal on a new set. Also KDE published a video where they use the exact same ESC I have to drive a TMotor U7 on a bench test. So I figure why not give it a try. At this point I'm suspecting that one 17" props are just too much, I have a set of 16x5.5 APC's to do some testing. And I'll be testing the motors on the ground taking the FC out if the loop to see if I can cause any timing synch issues with rapid throttle changes like you suggested. I will report back .
     
  10. traxx2003

    traxx2003 Member

    111
    6
    1
    Mar 30, 2015
    California
    Posted by traxx2003, May 11, 2016 #10
    Ok, I just finished testing the motors on the ground and I quickly discovered that I do in fact have some synch issues between my MN4120 400kv and KDE 55A ESC's. This of course is to no fault from T Motor or KDE. It is virtually impossible to design a motor or a ESC that is compatible with every motor or ESC available in the market. Unfortunately I learned this lesson the hard way $$$$$. Now I'm left with the decision to either get a set of KDE motors to match the ESC's I already have, or get some ESC's that will work with the Motors I already have.
     
  11. traxx2003

    traxx2003 Member

    111
    6
    1
    Mar 30, 2015
    California
    Posted by traxx2003, May 11, 2016 #11
    Is there a way to calibrate KDE ESC's using the transmitter manual mode? Im new to KDE ESC's.
     
  12. Hexacrafter

    Hexacrafter Manufacturer

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    Dec 11, 2012
    Cuyahoga Falls, Ohio
    Posted by Hexacrafter, May 12, 2016 #12
    For T-Motor the recommended products are on the T-Motor specific motor page with all of the accessories at the bottom of the page.
    For KDE they state the ESC pairing at the top of the page.
    If you are looking at other brands, I recommend that you contact the Mfg. and ask for a tested or proven pairing.
    Traxx.... I am glad you got it figured out...
     
    2 people like this.
  13. traxx2003

    traxx2003 Member

    111
    6
    1
    Mar 30, 2015
    California
    Posted by traxx2003, May 12, 2016 #13
    Ok, so I downloaded the black box data from my SuperX, the links below are for the flight data for the two rather short test flights I did on my new build. Maybe someone can interpret the data and could possibly identify any potential discrepancies. Currently I belive I do have a sync problem between my TMotor MN4120 400KV and KDE 55A esc's.

    Black Box data:

    http://log.xaircraft.com/report.htm#2016_05_12_231913.528_78.1.02.05

    http://log.xaircraft.com/report.htm#2016_05_12_231913.528_77.3.00.19
     
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