Huge flight time drop

Discussion in 'Cinestar 8' started by Cris Olariu, Aug 7, 2013.

  1. Steve Maller

    Steve Maller UAV Grief Counselor

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    Dave King likes this.
  2. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Thanks for posting that link, Steve....I went looking for it, but couldn't find it.

    Andy.
     
  3. Cris Olariu

    Cris Olariu Member

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    Steve -
    Took a look at your video about the motor with the bad bearing, then went and did the same thing for my CS8. I believe motor #3 doesn't sound right. The actual problem though is that now I became paranoid and it sounds to me like at least half my motors sound like something's wrong.
    Please watch the attached video and tell me what you guys think. I did a test on each motor individually, bringing them to about 60 in the MK Tool motortest.

     
  4. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Here's my take:

    Motor 1: Harsh
    Motor 2: Good.
    Motor 3: Slightly harsh.
    Motor 4: Good.
    Motor 5: Good.
    Motor 6: Good.
    Motor 7: Good.
    Motor 8: Good.

    Andy.
     
  5. Cris Olariu

    Cris Olariu Member

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    Awesome Andy, thank you. Is it really possible that because of those 2 motors, all the odd motors are pulling more current?
     
  6. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Maybe. Motor #1 sounds like a naffed up bearing IMO.

    Did you double check that all the prop shafts are absolutely vertical? If they are, then, by a process of elimination, I'd swap out motors 1 and 3 just to see if they're the cause -- you probably won't know the cause except in hindsight, I'm afraid.

    Seems to happen a lot to me that I swap out something and the problem in question goes away -- and then the light goes on in my head! Oh! So that's what was causing it! :)

    Andy
     
  7. Cris Olariu

    Cris Olariu Member

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    Thank you Andy. Would you recommend new motors altogether or just changing the bearings?
     
  8. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    My personal preference is to have spare motors so that I can swap motors out in the field and be back flying ASAP. Then I replace the bearings on the suspect motors. I view the bearings as a consumable. The motors themselves should last a lot longer, so I tend to view them as somewhat less of a consumable.

    That's a bit of a vague answer to your question -- sorry about that.... but that's just what I do.

    Andy.
     
  9. Steve Maller

    Steve Maller UAV Grief Counselor

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    If you are moderately handy, changing bearings is pretty easy. The little tool pays for itself after one replacement. There's little to go wrong in these motors other than the bearings, unless you've had a bad crash, in which case the shaft could be bent (or somehting else messed up). If that's the case, you should replace the motor.

    I keep a couple sets of bearings and one new motor around in my parts kit.
     
  10. Steve Maller

    Steve Maller UAV Grief Counselor

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  11. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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  12. Cris Olariu

    Cris Olariu Member

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    No massive crash yet (and hope to keep it that way). Thank you guys for your help! I'll be purchasing the replacement kit and the bearings and get working on it as soon as they arrive, and keep asking questions if I run into trouble.
     
  13. Steve Maller

    Steve Maller UAV Grief Counselor

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    Good luck. I hope it works. In the meantime I'd be very careful about flying the copter like that. Bearings sometimes don't fail very gracefully, and you don't want your motors and/or ESCs to overheat.
     
  14. Cris Olariu

    Cris Olariu Member

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    Yeah Steve, I'm probably not gonna fly at all till I get the new bearings installed. It'll give me a chance to look into other things that might need adjusting.
     
  15. Cris Olariu

    Cris Olariu Member

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    Just wanting to double check this before placing the order with Bart for the tool... I will need the 4mm version of his tool for the QC-3328 motors, correct?
     
  16. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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  17. Cris Olariu

    Cris Olariu Member

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    Alright. Finally got all my parts and tools and replaced the bearings this morning before going into work. That was quite easy with the little tool from Bart.
    Now, I just need to double check some of the props, they seem to be off balance horizontally (on the hub). Other than Velcro and superglue, what do you guys use on the APC props? (I saw people use lead tape for the wooden props, but that seems heavy for APCs)
     
  18. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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  19. Cris Olariu

    Cris Olariu Member

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    Alright. Grabbed some lead tape from a sporting good store, and got all the APC propellers nicely balanced. Did a couple flights, but I'm not noticing any improvement in flight time. Definitely the GPX file shows improvement in the overall current draw since I swapped the bearings. I'm attaching an example of a GPX file. But still did not solve my problem. :(
    I also went in and did a reset of all the settings in MKTool, and started fresh. No improvement there either.
    So I guess now I have to go on and either get a smaller (less heavy) camera, or upgrade the motors. I think for now I'll be looking into what motors might still go with the BLs I have, and wait for the Synapse to come out and splurge for that. But first, I've been looking either at a Sony Nex camera, or the Canon EOS M. I'm more inclined to get the Canon, since I can easily purchase a lens adapter and be able to use the lenses I already have (for various other projects, not aerials).
     

    Attached Files:

  20. Steve Maller

    Steve Maller UAV Grief Counselor

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    Chris, I looked at the GPX file, and those are some alarming temperatures. It appears as though you were mostly just hovering, so that might explain the high temps. You definitely want to get some airflow going over the power distribution board. I am always concerned when the BL temps hit 100°C. What is the AUW (all up weight) of your copter? You're running one battery, right? If you're at 15-16 lbs AUW, these performance numbers are probably about right. I'd also be concerned with the average wattage and current draws.

    MK Version: FC HW:2.1 SW:0.88n + NC HW:2.0 SW:0.28n

    Flight date: 8/26/2013 8:17:46 AM
    Flight time: 8:17:46 AM - 8:22:06 AM (260 secs, 00:04:20)
    Batt. time : 276 secs, 00:04:36

    Elevation(GPS) : 0 1.26 8.344 m (min/avg/max)
    Altitude(Barom.): -1.4 2.63 9 m
    Vertical speed : -1.49 -0.08 1.02 m/s
    Max speed : 8.1 km/h
    Max target dist.: 0 m

    Sats : 9 13 15

    Voltage : min. 14, max. 16.4 V
    Current : 11.4 79 94.3 A
    Wattage : 169 1170 1369.35 W
    Capacity: 5953 mAh

    Motor1: 0.3 7.5 11.6 A Temp: 45 77 92 °C
    Motor2: 1.0 10.8 13.1 A Temp: 47 86 102 °C
    Motor3: 1.5 9.5 13.2 A Temp: 44 82 94 °C
    Motor4: 1.2 10.5 14.7 A Temp: 45 94 107 °C
    Motor5: 1.2 9.0 12.1 A Temp: 45 87 99 °C
    Motor6: 0.8 10.2 12.9 A Temp: 47 94 108 °C
    Motor7: 2.1 9.0 12.9 A Temp: 47 84 100 °C
    Motor8: 2.2 10.1 13.1 A Temp: 49 88 104 °C

    Magnet Field: 86 90 97 % (ok)
    Magnet Inclination: 55 56 60 deg

    Errors / warnings:
    FC-Flag "LowBat" (5) occured 3 times!
     

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