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My horror story

Discussion in 'Electronics' started by Lauri Hakala, Jan 26, 2014.

  1. Lauri Hakala

    Lauri Hakala Member

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    Watch this first, take a firm grip of your seat!
    https://dl.dropboxusercontent.com/u/12790890/TheHorror.mp4

    Here's my horror story that happened this month, still sweating :0 So I was in the middle of shot trying to fly slowly above the road when suddenly our copter sped up like crazy and started to dive. Few moments after that the voice telemetry started to say "low voltage warning" and of course I thought that was the case. The copter had already dived really close to the sea level when I managed to get some kind of control over the copter, still wasn't able to stop it from yawing and just going all over the place. At the same time "low voltage" ringing in my head I decided that this is it, goodbye beloved Cinestar, I'm just gonna let it rest in the sea so it won't go anywhere near the buildings. Then I realised that I hadn't tried CH function and almost instantly when I clicked CH on the copter stabilised itself and started to come home really slowly. So both me and my camera operator where praying it would come back in time because it was still over the sea and low voltage alarm had already been on for almost a minute. So somehow it managed to come back to our take off point and I immediately switched everything back to manual and now it was flying totally smooth and I managed to land it perfectly!! So after a fast examination of the copter I found out that I indeed had lost a prop during the intended "flying slowly above the road" -shot :0 I didn't see or hear anything so I only thought that my batteries had to be really low voltage because of the alarm and that was the reason for odd behaviour.

    My setup is all mikrokopter boards with navi/gps. The flight log gpx file had recorded an amazing maximum speed of 75km/h (46mp/h)!! Never want this to happen again. It was also about -5 celcius degrees (23F) so I'm starting to think maybe the APC SF props can crack in cold environments or what do you think? So would you guys recommend using wooden xoars in the cold weather? Really scared to fly again in the cold with APC's :/ The nut had also been disappeared from the prop adapter so don't really know if the nut just got loose during the flight.

    After all I'm really amazed that I could get our bird back from that kind of horror dive, of course huge props for the mikrokopter boards!
     
  2. Lauri Hakala

    Lauri Hakala Member

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  3. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Nice save, Lauri.
    It's at times like that, that you discover that adrenalin is brown. :eek:

    Andy
     
  4. Steve Maller

    Steve Maller UAV Grief Counselor

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    OMG :eek:
    Fantastic recovery!!!

    I have lost an ESC in flight, but it was far less dramatic than your experience. Sadly, you might never know what caused the prop to exit the copter. But IMHO it probably wasn’t a broken prop, as that would have possibly caused a huge instability. The fact that the copter came back with no nut on the shaft is a clue that the prop nut might have worked its way loose. It doesn’t look like you’re using “nylock” nuts. Are you? They lock more positively and if they do come loose, stand a fighting chance of staying on the copter.
    [​IMG]
    The other option is going to a newer motor and CF props, many of which have a new mounting system that uses 2 small screws to mount the prop. But at $50-60 per prop, they’re quite pricey!
     
  5. Dave King

    Dave King Well-Known Member

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    Hi Lauri

    You find that these situations make you a better pilot. Nice recovery. Like Steve says, I can't stress enough that you use nylon nuts. Also I never reuse a nylon nut more than 2-3 times because that nylon does wear out. If you take the props off to transport the copter a lot buy a big bag of these nuts and consider them as consumables. As for the props I believe its just the opposite. I think the APC plastic props are better for colder weather and the wooden props are not that great for extreme cold weather as I think they can crack easily. I wouldn't run plastic props with heavy payloads though regardless of weather so it depends on your flight weight.
     
  6. Gary McCready

    Gary McCready Active Member

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  7. Gary Haynes

    Gary Haynes Administrator
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    Gary did you replace all 6 or just the CCW ones? You said all 6, hoping it is a typo.
     
  8. Gary McCready

    Gary McCready Active Member

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    I replaced all six, 3 CCW, and 3 CW. Sorry for the confusion. I did have to stop and think about which motors they went on, but it is easy figure out if you just spin the props...in their correct direction.
     
  9. Lauri Hakala

    Lauri Hakala Member

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    I also think that the nut just came loose because I haven't been using locking nuts, just have regularly checked they are tight. I'll definitely change to nylock ones now :) But I'm still a bit worried about the APC props cracking in the cold temperatures although some of you guys say that wooden props would crack even easier? My all up weight is about 7kg/15lbs and so far the 14x4.7 APC SF props have been working great on 2814 710kv 4s setup.
     
  10. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    I often pondered using a "lock nut" -- a second Nylok nut on top of the lower one. You tighten the top one down on to the second Nylok -- it doesn't increase the pressure on the prop, but it certainly stops the lower nut from coming loose.

    Andy.
     
  11. Ozkan Erden

    Ozkan Erden Distributor

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    I am very glad that you saved the copter.

    For prop choice, I would recommend the t-motor carbon props. They are very light, very well balanced and stiff.

    Being very light and very well balanced, it also prolongs the life of motor bearings. I see that you are probably using a 2814 motor with 6mm prop adapter. These carbon props will fit on 6mm adaptor.

    If possible, can you please upload the gpx file so we can take a look into it?
     
  12. Lauri Hakala

    Lauri Hakala Member

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    Thanks for the all great tips.
    Ozkan, here's the GPX file attached.
     

    Attached Files:

  13. Paul conto

    Paul conto Member

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    Andy - the double nut is one thing i did on another bird of mine. NEVER lost a nut/prop, works great.
     

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