Shaky video when descending vertically

Discussion in 'Radian' started by Alberto Restrepo, Sep 14, 2013.

  1. Alberto Restrepo

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    Hello.

    Someone can help me? My Cinestar 8 always vibrates very strong when it descends. I think isn´t the Radian because one year ago the Cinestar 8 with the 3 Axis Gimbal without Radian, vibrated too much.

    In the number 1 video (factory), you can see a flight of about a year ago without Radian and the number 2 video (buildings) you can see a flight on Sep 14 with Radian.





    The gain of the Radian are:

    Pan 35
    Roll 71
    Tilt 55

    Thanks
     
  2. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Alberto: The problem is one of aerodynamics. When the copter is descending it is flying into the turbulent air that has created itself from the downwards prop-wash. The only work-around is to descend at 20/30 degrees from the vertical to try and avoid this column of turbulent air by descending into clean air off to one side of the column of prop wash.

    PS: I changed the name of your thread to something more descriptive so other forum members can find it more easily. I hope you do not mind me doing that.

    Andy.
     
  3. Alberto Restrepo

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    Thanks Andy! There is no problem with the change of the subject. I will try to descend vertically on a 30° angle, and will let you know. Thanks again. When I finish uploading the video please watch it!
     
  4. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Thanks Alberto -- you may find that the column of turbulent air is blown off to one side if there is any wind, so sometimes you can have the copter descend closer to vertical on the upwind side of the air column without that turbulence.

    Andy.
     
  5. Paul conto

    Paul conto Member

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    The only real way to get the true strait down shot without any vibration is to cheat. Film it going up in the air and then in the editor play it backwards. Otherwise as they already said you need some horizontal movement to get away from the turbulent air.
     
  6. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    And then hope that there's no smoke, cars, trains, aircraft, people walking, etc. in shot! :)

    Andy.
     
  7. Steve Maller

    Steve Maller UAV Grief Counselor

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    I find that with the new MK ACC 2.2 installed on the FC board, if I have vario altitude hold enabled, I can descend slowly and it's quite smooth.
     
  8. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Steve: That's interesting. I presume that if you descend really slowly, the copter compresses the turbulent air down and away from it faster than it's descending into it....but I'm stretching my imagination to see what would be going on here...

    Andy.
     
  9. Jeff Scholl

    Jeff Scholl Distributor

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    This down pedestal camera movement was always a deal breaker with the Radians. Now with the MoVI you can descend like a drunken sailor and have everything perfect in the can.

    Cheers,
    Jeff
     
  10. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Hi Jeff:
    That's good to know. I was just responding to a posting from Forgeron in France and I wondered how Google translate your posting. <evil grin>

    Andy.
    ====
    Ce mouvement de la caméra sur pied à terre était toujours une pierre d'achoppement avec les radians. Maintenant, avec le Movi vous pouvez descendre comme un marin ivre et avoir tout soit parfait dans la boîte.
     
  11. Casey Van Nyhuis

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    Try descending at a slight angle outside your column of turbulence, while at the same time rapidly "feathering" the throttle up and down during your descent. I've found that between these two practices you can greatly improve stability on descents. I think that these short bursts of throttle, if done fast enough, seem to almost vent some of the turbulent air out from under the kopter. Could just be a placebo effect for me though ;)
     
    Steve Maller likes this.
  12. Brad McGiveron

    Brad McGiveron Active Member

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    Probably the single biggest advantage of a coaxial X configuration is the ability to descend slowly or rapidly without hardly any disturbance.
    It was the first thing I noticed when I first built one.
    Of coarse you get all the other pros and cons attached to this type of setup...
     
  13. David Pope

    David Pope New Member

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    Hi all. Just my two cents, but the main reason for 80% of the turbulence during descent is that the props are fixed pitch. Therefore, the ONLY way our MRs ascend or descend is through motor speed alone. Its fine for climbing and hovering, but when you descend, your "unloading" the props. No head speed = no load = no control.
    By decreasing pitch, and not speed, a SR heli's descents seem to involve so much less shuddering.
    I always wanted to build a smallish quad using four adjustable-pitch tail rotors turned on their sides to test feasibility... with big enough rotors, i bet it might even autorotate in emergencies. any thoughts?
     
  14. Jeff Scholl

    Jeff Scholl Distributor

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    Check out Youngbloods new stingray. Looks like 4 vibe tail rotors in quad fashion.

    Cheers,
    Jeff
     
  15. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Jeez. I can fly like that....but Youngblood does it deliberately. :)

    Andy.
     
  16. David Pope

    David Pope New Member

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    ha. ...always a day late and a dollar short. Remind me to someday tell ya 'bout all my ideas that allowed others to make millions.[​IMG]
    Also, now I remember why I always hated watching 3D hell videos - you never see a thing. Just sky. Cool model though. Ima keep watch on that.

    Thanks, Jeff
     

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