Gimbal repair

Discussion in '2 Axis Gimbal' started by Tuomas P., Dec 29, 2012.

  1. Tuomas P.

    Tuomas P. New Member

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    Hi,

    I had a battery burst while flying today and the heli came down smashing the gimbal. I need these parts:

    - Tilt steel axel
    -Tilt servo belt wheel
    -Tilt main belt wheel
    -Belt
    -Radian unit plastic front cover.

    Any help would be highly appreciated.

    Regards,
    Tuomas Pietinen, Cinecopter, Finland
     
  2. Tabb Firchau

    Tabb Firchau Administrator
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    Hi Tuomas,

    Everything but the Radian Cover should be available at your local reseller. Sent you a PM

    Tabb
     
  3. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Hi Tuomas:
    Sorry to hear about the mishap. Can you tell us more what happened? Which brand of battery were you using? Did it just explode and/or catch fire? I think there are several of us who would like to learn from what happened to you (or more particularly), the battery.

    Thanks
    Andy.
     
  4. Tuomas P.

    Tuomas P. New Member

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    Hi !
    First, thanks to Tabb for fast help! Yes, my X8 crashed today during a photo job. All as usual, until 2 minutes before the timer she comes down hitting a treetop first and then snow. Unfortunately icy and rock hard. My YS telemetry over the wifi lost contact and I also let the heli go behind a treetop momentarily. So I only could watch the monitor and the approaching trees.
    Like always, a combination of things here. The battery, a Zippy 4s 5800, was onboard in parallel with another one. They were in heat insulating bags. It was -12 Celsius. I tested them with a lipo checker before flight.
    But, as one battery indicated 3,7 V per cell after the crash, and the another, burst one 3 V, here is the clou:

    If the battery was already burst during charging in the bag, I could not see it. Still a burst battery can show decent voltage for a while. under load it will fail eventually. So luckily no bad damage here but the cold protecting can cause new problems. And this must be the last time when I go out from visual.
    Tuomas
     
  5. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Thanks for the additional information Tuomas. I would have hoped that your second battery would have allowed you to bring the aircraft home, but it sounds like that was not the case -- I suspect the bad battery dragged the voltage down on the good battery.

    You are very brave to fly in -12C. That must make everything far more difficult.

    I think you make a very good point about a battery that has exploded in a heat insulating bag might appear to be OK, but be bad. I guess that means there is no substitute for a pre-flight visual inspection -- although that will cool the batteries down....

    Thanks
    Andy.
     
  6. Steve Maller

    Steve Maller UAV Grief Counselor

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    As always, much appreciate the postmortem. Sound like you were both unlucky and lucky. Sorry and thank you. Good luck with the repairs!
     
  7. Ramesh Tahlan

    Ramesh Tahlan Member

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    Hi Toumas P.
    I always heard and also believe that one must never use batteries in Parallel to enhance the capacity... one should always go for a batt with the capacity needed... so just curious to know if u used diodes at both batteries end to prevent reverse current flow from the batt that is holding a higher charge so a higher voltage to the batt that is loosing charge faster and so has a lower voltage.....i dont know how much more weight diodes will add cause the current flow is fairly high and my guess is the diodes would be bulky more than the weight issue cause of the cooling fins needed ....
    regards
    Ramesh Tahlan
     
  8. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Ramesh: I'm afraid you've been misinformed (please don't kill the messenger! :) ). The higher capacity LiPos achieve their capacity by wiring cells in parallel. Provided that the two batteries have the same traits (vendor, charge history, etc), are are charged on a charger designed to charge batteries in parallel, it seems to be quite acceptable to use dual battery configurations.

    I think what happened in Tuomas' case is that unusual event of an exploding battery shorted out the bad battery which in turn dragged down the good battery's voltage.

    So, in sum, you certainly can put LiPo's in parallel subject to certain conditions that I mention above. No diodes required -- in fact, you'd experience a 1.4v diode junction voltage drop if you put them in -- plus they'd need to be rated for 80 Amps or more, I would expect.

    Andy.
     
  9. Ramesh Tahlan

    Ramesh Tahlan Member

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    Andy
    Many Thanks for clearing that up
    Ramesh Tahlan
     
  10. Tuomas P.

    Tuomas P. New Member

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    I am using the Quanum battery telemetry now monitoring every cell individually. A great tool-made me ditch almost all my batteries and order new ones...
    Tuomas
     

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