Crash cage or dome

Discussion in 'Cinestar 8' started by Mikko Kosonen, Jul 12, 2012.

  1. Janne Hoglund

    Janne Hoglund Member

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    Second that one!

    If only Tabb or the good people at QC had a tutorial since this seems to be such a vital step![/quote]
     
  2. William Johnston

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    I was hoping Josh would have posted one of his GPX files by now.

    Anyway, I found my old paper on my brushless DC motor controler simulator. It looks positivly primitive by todays standards, at the time I thought it was hot stuff. It does have the equations for a brushless DC motor which somebody might find useful for simulating a copter.
    http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=593031
     
  3. William Johnston

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    Well Hell. After waiting over 8 weeks I got the part back unaltered. The message (in German) says that the motor test was ok and that the temperature message of BL #8 is functioning. And that they won't do a part swap. I could have told them that they can run the motor and get a temperature reading, that doesn't actually test what was wrong with it.

    I guess I can do those tests now. I would have much rather have gotten a functioning part. :-(

    This is not as bad as a stick in the eye, but just barely.
     
  4. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Bummer. But, as you say, you can do some tests on it and see whether that BL has a capacitative coupling to the PDB....
    As you say, not quite as a kick in the rear with a sharp stick....so to speak....

    Andy.
     
  5. William Johnston

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    Well Darn... I think I figured out what is wrong with my CS8. I went to balance the propellers yesterday and when I took the first one off I thought, "that doesn't look right." Having not looked at it for a couple of months let me see it with new eyes. Well damn. Damn. Damn. Damn. Damn. I haven't flow it yet so I can't be certain that that is the problem, but I'm 99% certain. I have Phd in engineering and it took me four months to figure this out. Sheesh... I wonder if a sharp stick in the eye will make me feel better.

    So here the rule:
    If your deans plug melts, your propellers are on upside down.

    Yep, I systematically put every propeller on upside down. I did that. Worse than that, is that I never even gave a thought to the propellers as being the problem. Not even once. Oh well, the sign on the door says electrical engineer not aeronautical engineer.

    Soooooo..... I owe some Germans an apology for the terrible thoughts I was thinking about them.

    You know, crow doesn't taste so bad with a bit a salt.
     
  6. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    William:
    Full kudos to you for (a) finding the problem, (b) 'fessing up to what it was, and (c) sharing it with us.

    What I do, when I balance the props during the evening as I watch The Daily Show, is I take a Sharpie pen and draw on one blade about 1" out from the hub, an arrow on the top surface showing the direction in which the prop should rotate and then the word "Odd" or "Even" so I can check the boom number on which I'm mounting the prop.

    I also make a note (on the other blade) of the boom number on which I mount the prop and the date when it was put into service.

    But congratulations on earning your first honorary credit towards aeronautical engineering!

    Andy.
     
  7. William Johnston

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    In thinking about the problem I considered the plug, the gauge of the power wire, the solder connection of the power wire to the power distribution board, the power distribution board, the ESCs, the solder connection of the motor wire to the ESC, the plugs on the motor wire, the gauge of the motor wires, and the motors. It never occurred to me that the propellers might be the problem. They're just a piece of nylon and I could see that they were fine by looking at them. What could possible be wrong with propellers after all? And I thought I was really on to something with the replaced ESC only reporting 5.4 amps, but now I think that that ESC is measuring the current wrong.

    Looking at the number again:

    Flight Time: 2012-08-12T16:52:29Z
    Flight Duration: 59 seconds
    Average Current (Amps):
    18.0 19.8 14.9 12.7 5.5 13.2 14.3 19.0 0.0 0.0 0.0 0.0 Total=117.5
    Maximum Temperature (Celsius):
    105.0 107.0 77.0 81.0 73.0 73.0 79.0 95.0 0.0 0.0 0.0 0.0

    We can use temperature as a proxy for current and figure that the motor is really pulling about 13 amps.
     
  8. Josh Lambeth

    Josh Lambeth Well-Known Member

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    Are those numbers after flipping all your props around? Hopefully not!

    Josh
     
  9. William Johnston

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    Oh no. Those are the numbers from before. It's that low 5.5 value that made me think that there was something wrong with all the other ESCs. It lead me on a wild goose chase. I wasted two months RMAing the part back. I'm pretty sure now that the 5.5 amp measurment on ESC 5 is wrong.

    I haven't flown it yet since I flipped the props over. It was too windy this morning and I ran out of light last night. I have an indoor facility that I can fly at, but I have read that it won't write a GPX file if it can't get satellite lock. I don't know if that's true or not. I'll find out later this week when I do flight duration tests (assuming that my current problem is fixed).
     
  10. Josh Lambeth

    Josh Lambeth Well-Known Member

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    I don't believe that is true... If you check the box to allow you to start motors w/out a GPS lock it will still record. At least it has for me...

    Josh
     
  11. William Johnston

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    OK the results are in. Drum roll please:

    Flight Time 2012-10-22T23:44:27Z
    Flight Duration 3 minutes 35 seconds
    Average Current (Amps)
    4.5 2.6 4.2 1.5 1.5 1.5 3.6 2.6 0.0 0.0 0.0 0.0 Total=22.1
    Maximum Temperature (Celsius)
    67.0 55.0 55.0 41.0 46.0 41.0 55.0 51.0 0.0 0.0 0.0 0.0

    So that's that. I wish I had had the ah-ha moment 3 months ago, but better late then never as they say.

    I'm happy that it's finally working, but I'm sad that it was my own lunkhead fault that it wasn't working in the first place. On the bright side, I learned a lot trying to figure out what was wrong.
     
  12. Josh Lambeth

    Josh Lambeth Well-Known Member

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    Nice! Congrats on getting things all sorted out!

    Josh
     
  13. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Nice work, William.
    For those who follow and read this thread later, would you say that the "clue" that things are wrong was the unusually high current and temps for seven out of the eight motors? That's seems to be the primary traits of the problem?

    Now, weather permitting, you can fly and enjoy yourself...in between the heart stopping moments, that is. :rolleyes:

    Andy.
     

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