/dist/images/branding/favicon

Eliminating roll twitch...

Discussion in '3 Axis Gimbal' started by Benjamin Rowland, Mar 3, 2013.

  1. Benjamin Rowland

    Joined:
    Jun 29, 2012
    Messages:
    88
    Likes Received:
    12
    I've noticed that in windy conditions that the roll axis can get a bit twitchy. From reading the forum posts, many others have seen this as well. My theory (shared with others) is that the connection between the gimbal and copter allows for too much movement of the gimbal, even with a lighter camera, causing the Radian to get stuck for a bit in a cycle of twitch. The o-ring setup definitely keeps the motor vibes from reaching the camera, but it would seem there's a bit too much movement between the two parts.

    People have posted several mods that have had varying results. Can anyone report back on what works really well?

    We have another multirotor that we're working out some issues with, but it does not exhibit the roll twitch, so I know it is possible to achieve better results on the roll axis than I'm currently getting.

    All that said, we love our Cinestar. We're just trying to fix this one issue so we can get it closer to perfection. Thanks for your help!

    all the best,
    Ben
     
  2. Pavlos Antoniou

    Joined:
    Oct 6, 2012
    Messages:
    321
    Likes Received:
    18
    Welcome to our club Ben...!!! :) :)
    We wish that freefly will release something on NAB ...

    Otherwise a good solution might be the Allieddrones echo qck antibive systems..!
     
  3. Howard Dapp

    Howard Dapp Active Member

    Joined:
    Aug 18, 2012
    Messages:
    977
    Likes Received:
    111
    I also fly a custom built rig and the only dampening I use between 3x gimbal and airframe are rubber grommets. I see absolutely no vibes down at the gimbal and through the 5D lens and honestly I never balance props. I've once suggested that you guys try hard mounting your gimbals or at least use a much stiffer dampening solution or some sort of grommet dampening to see if you still experience these issues. If the issues go away but in turn you're seeing vibes, then you need to look into stiffening that frame. My frame is alu so I'm not sure if CF does a better job at amplifying vibes. Some guys are stiffening their CF frames by linking the ends of their booms with some sort of aluminum wire.
     
  4. Pavlos Antoniou

    Joined:
    Oct 6, 2012
    Messages:
    321
    Likes Received:
    18
  5. Howard Dapp

    Howard Dapp Active Member

    Joined:
    Aug 18, 2012
    Messages:
    977
    Likes Received:
    111
  6. Gary Haynes

    Gary Haynes Administrator
    Staff Member

    Joined:
    Jul 6, 2012
    Messages:
    5,211
    Likes Received:
    460
    Howard what are 'those' and where do you find them?
     
  7. Howard Dapp

    Howard Dapp Active Member

    Joined:
    Aug 18, 2012
    Messages:
    977
    Likes Received:
    111
  8. Ryan J. Rowe

    Ryan J. Rowe Member

    Joined:
    Oct 27, 2012
    Messages:
    71
    Likes Received:
    8
    I'm running out of ideas on the roll twitch issue as well. I too have tried everything and still rely on post stab to remove the small twitches. I've noticed that the higher the gain the less twitch and I've taken the gain high enough that the twitch is gone, but then the oscillation action occurs. Maybe the science doesn't allow it but it seems like we need more gain without oscillation?.....
     
  9. Tim Joy

    Tim Joy Active Member

    Joined:
    Aug 2, 2012
    Messages:
    405
    Likes Received:
    72
    For me it seems to be a combination of oscillation between radian and the o-rings and the slop in the servo/ belt if the drive system. When it's off, even with the belt tight there's stretching of the belt and flexing of the servo mount that can be seen by moving it.
     
  10. Ryan J. Rowe

    Ryan J. Rowe Member

    Joined:
    Oct 27, 2012
    Messages:
    71
    Likes Received:
    8
    I agree Tim. I see that as well.
     
  11. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
    Staff Member

    Joined:
    Jul 31, 2012
    Messages:
    10,383
    Likes Received:
    1,164
  12. Howard Dapp

    Howard Dapp Active Member

    Joined:
    Aug 18, 2012
    Messages:
    977
    Likes Received:
    111
    Andy, my company ordered them in bulk direct from Gelmec a couple years back for another project unrelated to multirotors. I'm not sure if an individual can actually order them in small quantities. There are other suppliers of these I've found here in the states but they're not made of the same thermoplastic material.
     
  13. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
    Staff Member

    Joined:
    Jul 31, 2012
    Messages:
    10,383
    Likes Received:
    1,164
    I'll email Gelmec and find out who might be able to supply them.

    Thanks
    Andy.
     
  14. Gary Haynes

    Gary Haynes Administrator
    Staff Member

    Joined:
    Jul 6, 2012
    Messages:
    5,211
    Likes Received:
    460
    These look exactly like the grommets that come with the Hoverfly boards. Looked on the the Gelmec website and they have them in blue. Dead ringer for HF.
     
  15. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
    Staff Member

    Joined:
    Jul 31, 2012
    Messages:
    10,383
    Likes Received:
    1,164
    Yeah, if you do a Google search, there are whole bunch of anti-vibration grommets, so I'm sure someone in the USA will have them.

    Andy.
     
  16. Howard Dapp

    Howard Dapp Active Member

    Joined:
    Aug 18, 2012
    Messages:
    977
    Likes Received:
    111
    Those blue grommets are not made from the same soft material but still may work. I purchased a bunch some time ago but never used them so I'm not sure how well they'll isolate high frequency vibes. Here's a supplier of those in the states:
    http://www.vibrationmounts.com/Store.asp?Page=Products7.htm
    gromm.jpg
     

Share This Page