Freefly servo's not having consistent movement at low speeds

Discussion in '3 Axis Gimbal' started by Kim Hoogervorst, Mar 14, 2013.

  1. Kim Hoogervorst

    Kim Hoogervorst New Member

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    Hello fellow flying cameramen :)

    I own a cinestar gimball for about a year and a half now. It's been great. I've been testing lately en started using some longer lenses 50-90 mm on a 5D. What my camera operator noticed was that especially on the yaw the movement is not consistent in slow movement. So when giving a certain (low) stick input the pan movement in this case will go from a little faster to slower in pulses of half a second or so. So i took the mount of and the yaw servo and started investigation. I connected the servo directly to an receiver and made a new model in my tx. Then i used the trim sticks to create a constant tx output to the servo. In the slow movement u can actually see and hear that the servo is not running constant. I tried it on 6v and 5v but no real difference. Then i wanted to know if the other servos had the same issue and surprisingly they all had problems on the low speeds. Is anyone else having these issues? And is this a known problem?

    I think it could be caused by usage but i think it was always there but we didn't notice it enough. Would be happy to hear from u guys and see what your findings are....

    Cheers!

    Fuwu
     
  2. Brad Meier

    Brad Meier Active Member
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    Can you try it without the servos connected to the belts? My thought is maybe the gimbal is binding in places, making the servo work harder in spots. Also when the belt is removed do the tilt and roll axis move freely?

    Brad
     
  3. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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  4. Kim Hoogervorst

    Kim Hoogervorst New Member

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    Hi Brad,

    thanks for the reply. I already did a dry run on the servo's without the belt and the servo removed from the mount. All axis run smoothly. When i've got time i'll make a short video to demonstrate. Any other thoughts?

    Thanks!
     
  5. Cyril Perrier

    Cyril Perrier New Member

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    I think I have the same issue... My camera operator has noticed the same effect. The pan rotation it not really constant when movements are slow. Sometimes, It even creates oscillations. As you can see on that video, the dampers are shacking.
    Radian gain is 50%, but the problem is still there with lower gain.
    There is No hard point in bearings. Without the belt, there is no resistance...
    Here is a screenshot of settings. Capture.JPG
     
  6. Shaun Stanton

    Shaun Stanton Active Member

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    I had the same issue. I was able to trace it to the lower bearing on the Center Hub of the gimbal, was grinding. By doing as KIM stated above you can tell with the belt off if the bearings have smooth movement. When rotating the center plate I noticed on mine that at real low rotations I could feel some binding. At higher speeds this goes away.

    I went one step further I removed the center plate and disassembled the center hub by popping out the spindle that attaches the the mounting plate. I ran my index finger through both bearings. I felt significant grinding on the bottom plate, either from being worn out or it had ingested some fine particulate matter like sand or dust.

    Tabb sent me some replacement bearings that I am going to press in today.
     
  7. Chris Theakstone

    Chris Theakstone New Member

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    Ours is doing this and it's all brand new, we've tried all sorts, gains up and down, expo, balanced everything with the belts off and still jerky slow pan and tilt. Our camera guys not happy
     
  8. Sebastian Meredith

    Sebastian Meredith Active Member

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    We adjusted the expo on the MX controllers to soften the sensitivity of the stick movement around the centre. This seems to help smooth it out and give more control in the movements.
     
  9. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    What I did was to use Expo on the TX and also reduce the slew rate in the pan Radian setting.

    Andy.
     

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