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Huge flight time drop

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

  1. Cris Olariu

    Cris Olariu Member

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    Hey guys -

    Finally moved from shooting on my CS8 with 3-axis Radian gimbal with the GoPro Hero2 to the Canon 60D with a 28-70 Sigma lens. Well, it definitely looks much better. But... I was getting a little over 8 minutes of flight on a Quadropower 8000mAh when shooting with the GoPro, and now my DX8 starts warning me of low voltage at little over the 2 minute mark!!! On the OSD, it shows that I've used only about 3000 mAh, but voltage drops to almost 14.2 by the time I land (if not even lower). Same results I get with the Zippy 8000.
    Now, I am using still the APC 14x4.7 props, but plan to upgrade this weekend to the XOAR 14x5s (they've just been shipped my way). I'm sure that will increase flight time, but I highly doubt it'll be by 6 minutes.
    The gimbal itself is pretty balanced, with a slight off-balance towards the back leg. Unfortunately, I don't think I can get better results balancing it until I order longer booms (I've seen someone order longer roll booms so they can push the camera forward more).

    I'll post a little later a couple of the logs both from today and from when I shot last with the GoPro, maybe someone can spot the issue.

    Any thoughts/ideas are appreciated.
    Thank you!
     
  2. Gary Haynes

    Gary Haynes Administrator
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    How much does your 60D with lens weigh? Any other changes to your setup? Total all up weight? Which motors?
     
  3. Steve Maller

    Steve Maller UAV Grief Counselor

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    That's a pretty heavy lens.
     
  4. Matt Barker

    Matt Barker Member

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    That is a big jump in weight. You are going from 4oz to 45oz.

    A lighter lens might be need to be your next upgrade.

    QC Motors?

    What C are you charging your batteries at?
     
  5. Cris Olariu

    Cris Olariu Member

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    @Steve That is indeed a heavy lens. I should be receiving the adjustable camera plate in a couple days and that will allow me to rebalance it with a 28mm or a 50mm lens (since I'm not using the zoom yet).
    @Gary Absolutely no other changes but the camera. I haven't weighted the camera, but I can do that tonight and let you know. I'm using the QC-3328 motors.

    Also, here are 2 log files. The one from 07/23/13 is with the GoPro, and the one from 08/07/13 is with the 60D. Seems like the time and the amount of mAh I get to pull out of the battery until it starts warning me both get halved.
     

    Attached Files:

  6. Cris Olariu

    Cris Olariu Member

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    @Matt: I only charge my batteries at 1.0 Amps, sometimes even lower. And they all look healthy, taking in all the mAh they can get. :) Is there a better zoom lens you would recommend on this? As I mentioned, I plan on switching to either the 28mm or the 50mm prime as soon as I get the adjustable plate in the mail, but a zoom would be nice to have on there.
     
  7. Dave King

    Dave King Well-Known Member

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    I get a minute less flight times with my XOAR props than I did with the APC props. For my CS8, gas at idle is about 8% more but the motor temps drop about 10%. I get 8 minutes with a CS8, 3 axis gimble, 2 QC6200 batteries and a 7D with a lighter 20mm prime lens.
     
  8. Cris Olariu

    Cris Olariu Member

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    Wow Dave. I thought everyone's consensus was that XOAR props increases flight times. Good to know that's not always the case.
     
  9. Brad McGiveron

    Brad McGiveron Active Member

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    The Xoar consensus is that the quality of the flight is way better, not the amount of flight.;)

    Yes, your camera and lens weight is just taking the stock config to its knees when you figure in the mount and all, its beyond what its really comfortably flying. I know lots fly it with the stock config and similar weights, I used to... but a lighter lens is required for reasonable flight times or more power.
     
  10. Cris Olariu

    Cris Olariu Member

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    @Brad That's good to know. What else would you recommend I do, other than changing up the lens?

    Is there anything unusual you guys notice on the GPX files that I could address in the meantime?
     
  11. Brad McGiveron

    Brad McGiveron Active Member

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    Not much you can do with the MK BL's as far as more power goes, so a much lighter lens selection is probably your best bet.

    Otherwise you need to look at larger motors and new ESC's. Many threads on upgrades and converted builds around here which continue to use the MK stack and the converter.
     
  12. Aleksej Bukilic

    Aleksej Bukilic New Member

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    I get 7-8 minutes of flight time with CS8, MK electronics, 3x gimbal, KW4 motors, Xoar 14/4 props lifting a 5D MkII + Canon 16-35 lens using either 2x5800mah 5s Zippys or one 10000mah 5s Gens ace Lipo. I had 3-4 minute flights with a RED + Canon 17-40 lens with Gens aces (I almost filled my pants doing it). If you go for the 5s's make sure that your FC is 5s ready or you will fry it.
     
  13. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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  14. Steve Maller

    Steve Maller UAV Grief Counselor

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    I would take a good look at your motors, and in particular make sure they're all perfectly vertical, and that you don't possibly have one or more bad motor bearings or something. And you also may have your yaw trim on your transmitter out of whack, or maybe even one of your flight controller PIDs misconfigured.

    The voltages are severely unbalanced, which is an indication of something wrong, and could explain the anemic battery performance. Look at these levels. And the corresponding temperatures are also really high.

    Motor1: 7.5 12.4 18.4 A Temp: 40 84 97 °C
    Motor2: 5.7 7.1 9.4 A Temp: 39 69 79 °C
    Motor3: 5.1 14.7 19.3 A Temp: 39 80 95 °C
    Motor4: 0.9 5.9 8.7 A Temp: 37 59 78 °C
    Motor5: 8.7 11.3 13.8 A Temp: 38 74 94 °C
    Motor6: 4.5 6.7 9.3 A Temp: 37 59 77 °C
    Motor7: 0.5 13.7 16.4 A Temp: 39 80 91 °C
    Motor8: 1.4 7.8 10.6 A Temp: 39 71 81 °C
     
  15. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Them's be Amps, Mr. Maller. Not be Volts.
    But your diagnosis seems sound -- all the counterclockwise motors are working REALLY hard in comparison to the clockwise spinning ones.

    Andy.
     
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  16. Steve Maller

    Steve Maller UAV Grief Counselor

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    Dammit, Captain, I'm a hacker, not an engineer! :cool:
     
  17. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    OK. In which case, I'll use really short words: Ampy thingies, not volty thingies.... :)
     
  18. Cris Olariu

    Cris Olariu Member

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    Hey Steve -

    Thanks for replying! Looks like I had the same problem prior to mounting the Canon 60D. I gotta start digging into it. Here's the plan:
    1. Re-balance the motors
    2. Check motors for bad bearings (How does one do that by the way?)
    3. Since the yaw trim is (as far as I remember, without having it in front of me) at 0, I'll take a look at the PIDs. I know I messed with those a while back, following the videos Tiago made in Brazil. What do you guys use for that?
    4. Is there anything else that would force only the odd motors to eat up twice the Amps?

    Thank you guys (all of you) for replying and helping thru this. I have to say, this forum is filled with awesome people!!! Keep it up please. :)
     
  19. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Cris:
    It's not the motor's balance as such but whether or not the axis of the prop shaft is vertical with respect to the hub plates and the other booms.

    You can check this quickly by swinging the prop blades on motor 1 around and then bring the prop blades on motor 2 around -- are the the blade tips on motor 1 at the same height as on motor 2? If not, then one of the motors is out of vertical.

    You can also get some idea of the vertical alignment if, from about two feet from a motor, you sight along the vertical side of the motor's "bell" and shift your head left and right to line up the side of the bell with one of the battery plate posts. The side of the motor should be absolutely parallel with the battery plate post.

    If one or more motors are not perfectly vertical, then the "center of thrust" of that motor will be inducing a yawing motion. In this case, it's likely that one of the even numbered motors is out of alignment as the odd numbered motors are having to work harder to oppose the resulting yawing motion.

    I'd suggest making a note of the PID values you currently have and then setting them back to the default by clicking on the icon that's an exclamation mark in the red triangle -- but watch out -- that sets *everything* back to its default value for the currently selected parameter set (which is the number just to the right of the red triangle).

    To check for bad bearings, take the props off all the motors and, using MK Tool's motor test, spin up each motor in turn and listen. If the motor sounds at all raspy or harsh, or you can hear any ticking, then the bearings may be bad.

    Hope this helps.
    Andy.
     
  20. Cris Olariu

    Cris Olariu Member

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    Thank you Andy. I'll give all that a try over the next couple days.
     

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