MoVI M15 Pan Balance Question

Discussion in 'MōVI M15' started by Nick Rubino-Bradway, May 21, 2015.

  1. Nick Rubino-Bradway

    Nick Rubino-Bradway New Member

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    Hello - just a quick question regarding the pan balance on the M15.

    I read that, because of the dual pan tube on the M15, the need to do the second part of the Pan Balance (that is normally required to fine tune the Pan Balance on the M10) has been effectively eliminated. I did however check this step on my M15 when balancing it for the first time by tilting the M15 while the assembly was facing forward, and noticed that the M15 still drifted or "swung" to the left.

    I'm wondering what step I need to take to adjust this part of the Pan Balance since the dual-tube pan bar prevents the assembly from being rotated in either direction. Does the issue I'm running into make sense and has anyone else out there run into it?

    Thanks in advance for any help you can offer!

    Nick
     
  2. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Nick: Can you confirm that you have both the tilt and roll correctly balanced?
    If you have, then the trick is to move the "center of mass" of everything below the twin pan booms so that the center is directly below the shaft of the pan motor -- annd to do that you need only slide the two pan knuckles in towards the pan motor or back out away from the pan motor.

    If you find that just moving the pan knuckles in or out doesn't allow you to balance in the pan axis, it suggests that you might need to double check the tilt and roll axes -- in specific physical terms, if moving the pan knuckles in and out fails to bring the center of mass under the pan motor's shaft, then that suggests the center of mass is not properly on the extended center line of the pan booms. (Mr. Maller hates it when I go all technical...) :)

    Out of curiosity, what camera + accessories are you flying on the MōVI? It doesn't make any difference to the balancing technique, but others who have the same camera may be able to help.

    ANdy.
     
  3. Ben Platts

    Ben Platts Active Member

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    Hi Nick. I had never had a problem balancing the pan on my M15 until i tightened one of the quick release pan clamps. After a few confused minutes of why the pan was now unbalanced after I realised that by tightening the clamp it had slightly pulled the down bar to one side and was causing the problem. I'd make sure the down bar looks totally dead centre when both clamps are done up.
     
  4. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Good point, Ben. The down post should indeed be vertical otherwise it's really hard to get the center of mass right under the pan motor shaft axis and have tilt and roll balanced.

    Andy.
     
  5. Nick Rubino-Bradway

    Nick Rubino-Bradway New Member

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    Hey guys,
    Thanks so much for the quick replies - I can confirm that both my tilt and roll are correctly balanced. The camera stays in place when adjusted or repositioned, and does not drift, swing or pendulum in any direction when I change the position of the camera until I arrive at the second part of checking the pan balance.
    I am currently testing the equipment with the a simple Canon 7D with a stock lens setup, no bells and whistles. Just want to use something to check the general balance and get used to it before bringing it on set.
    I checked the Quick Release Pan Clamps and they both appeared level and tightened to the same degree. The bar also looks dead centre when the clamps are both locked and unlocked.
    Andy - I shot a quick video of the problem if you'd like me to forward it to you? I can't upload it to this thread, but I'm happy to upload it to DropBox and PM you a link if that would help. Maybe I'm missing an obvious step that you or someone at Freefly would spot?
    Nick
     
  6. Nick Rubino-Bradway

    Nick Rubino-Bradway New Member

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    Hey guys -

    No need to reply to this thread, I found the issue and it was the simplest thing in the world. I only had one MoVI LiPo Battery on the rig, instead of two (one in each battery cage). So when I would tilt it forward the rig would swing in the direction of the empty battery cage.

    I just want to verify that this is indeed a step that Freefly intends for the operators to take on each setup? That in order to achieve proper balance with the M15, both battery cages must have a battery inside them?

    Thanks for you help and can't wait to shoot!

    Nick
     
  7. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Ha! Nice work Nick....yes, the idea is that the assembly is balanced and thus needs the second battery so that "center of mass" is right under the pan motor.

    I should have asked you about the second battery in my first posting, but I spaced it....sorry.
    Andy.
     
  8. alex ryan

    alex ryan Member

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    I just modified my M10 to be basically an M15. I balanced it for the first time today and came across the same issue.

    Here's a video of the issue


    password: balance

    I just balanced it with the camera I had on hand at the time. Could it be that this camera is too small and I need to bring the side arms back a bit in order to achieve accurate balance?

    I spoke to someone about this and they said you dont have to worry about the second half of the balance process with the M15. Is this correct?

    If its not correct, what should I be doing differently?

    I should mention that I was able to achieve good stiffness values with the balance the way it is in the video

    Thanks
     
  9. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Alex:
    The problem you show in the video is that the MoVI is not balanced in the pan axis. It looks like the "battery side" of the assembly is too heavy as it pans around to lower the batteries right at the end of the video. That suggests that the center of gravity of the whole assembly is towards the batteries rather than at the pan axis motor shaft.

    You might want to experiment with using a heavier camera to mass-balance the weight of the items on the "battery side" of the gimbal.

    Hope this helps
    Andy.


    Forensic Software & sUAV / Drone Analyst : Photographer : Videographer : Pilot (Portland, Oregon, USA): Trees=2, Ground=1, Props=11. :(
    The Ground Is The Limit™
    ---------- Forensic Drone Analyst : Forensic sUAV Analyst : Forensic Unmanned Aircraft Analyst : Forensic Drone Expert
     
  10. alex ryan

    alex ryan Member

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    Thanks Andy,

    Just trying to get my head around this. If the CG is towards the battery side of the rig shouldn't the gimbal swing towards the batteries in the first part of the pan balance check (when the pan tubes are parallel with the handle bar)? it does appear to swing a few millimetres, but with the balance this close I would expect the gimbal to swing less assertively in the second part of the pan balance check.

    There was still room to bring the assembly further forward on the pan tubes, I was just in a bit of a rush to get out of the studio so didn't have time to fine tune, but if I understand what your saying correctly, if I brought the assembly forward so there was absolutely no swing in the first part of the pan balance check I should see no swing in the second pan balance check position?

    As someone that is used to the M10 balancing procedure it is slightly confusing to me that there is no longer the pan side to side balance parameter and I'm trying to work out how to achieve accurate pan balance, especially when accessories and landing gear are attached to the rig. If I attach landing gear to one of the pan tubes and a video transmitter to the 'brains' won't this throw the balance of the rig off (unless the items are placed perfectly in balance)?

    The guy that built the modification that you see on my gimbal said you can only achieve perfect balance with use of counterweights or perfect placement of the accessories, but in practice it will not matter, the gimbal will perform perfectly as long as the first pan balance check is perfect. Is this correct?
     
  11. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    What we used to do back in the Dim Times to check the pan axis, is rotate the entire gimbal so that it was rotating in a vertical plane (the shaft of the pan motor would then be horizontal) and then see which way it wanted to move. Before you rotate into that position, you have to use some Velcro or cable ties to lock the various parts of gimbal in their normal position to avoid it flopping all over the place.

    You might want to try that as it then makes it completely obvious what's going on.

    The gimbal can certainly overcome a certain amount of "out of balance" force -- but to do so it has to make the motors work harder so it will reduce the battery life.

    Hope that helps.
    Andy

    Forensic Software & sUAV / Drone Analyst : Photographer : Videographer : Pilot (Portland, Oregon, USA): Trees=2, Ground=1, Props=11. :(
    The Ground Is The Limit™
    ---------- Forensic Drone Analyst : Forensic sUAV Analyst : Forensic Unmanned Aircraft Analyst : Forensic Drone Expert
     
  12. Graham Futerfas

    Graham Futerfas Well-Known Member

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    Andy's correct -- you appear too heavy toward the back of the Movi, and should keep sliding along the double-pan-tubes toward the camera.

    Or add your video transmitter to the top of the camera cage? That will put weight away from the back of the Movi.

    I check Pan balance a little differently -- maybe a less extreme version of what Andy's suggesting? You don't have side-to-side Pan Balance with the double tubes because it's not possible to be rotated that way with the M15.

    Here's how I do it: (only the first 2 minutes are applicable to adjusting an M15)
     
  13. alex ryan

    alex ryan Member

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    I'll give that a go Andy,

    It's interesting because the balance seems to be quite a bit off on the pan axis, but with this light camera I was still able to get motor stiffness value of 180 and in a stationary position the motor was working at 2%. This seems pretty good to me.
     
  14. Graham Futerfas

    Graham Futerfas Well-Known Member

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    By the way, that's a really great-looking modification from the M10 to the M15.
     
  15. alex ryan

    alex ryan Member

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    Yeah, I havent tested it in the field yet. That will happen in a couple of days, but I'm pretty impressed. It was built by a company called Ignite Digi based here in Australia.
     
  16. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    I'm not sure the stiffness value relates linearly to the mass-off-balance, Alex....Also, how hard the motors are working really needs to be assess in two different states: 1) MoVI at rest, 2) MoVI subjected to accelerations (like you're movin' dude...) :)

    Andy.

    Forensic Software & sUAV / Drone Analyst : Photographer : Videographer : Pilot (Portland, Oregon, USA): Trees=2, Ground=1, Props=11. :(
    The Ground Is The Limit™
    ---------- Forensic Drone Analyst : Forensic sUAV Analyst : Forensic Unmanned Aircraft Analyst : Forensic Drone Expert
     
  17. alex ryan

    alex ryan Member

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    Ill be taking it for a fly on friday so hopefully I'll have a better idea how it is operating
     
  18. alex ryan

    alex ryan Member

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    A few people have suggested putting the video transmitter on the cage or attaching to the camera. I use a amimon connex and am just wondering if i where to mount it to the camera/cage, where would I mount the antenna so they dont get in the way, still point downwards and maintain a two inch separation from carbon and metal on the gimbal?
     
  19. alex ryan

    alex ryan Member

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    So today I took it for a fly and when I added the landing gear and vtx it all balances out perfectly. Marginally heavier camera set up, but pretty similar. The only significant difference that I can see that would have effected the pan balance this much is the back landing gear. It's almost as if in order to be in perfect balance it needs landing gear attached to the right hand horizontal pan tube.
     
  20. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Alex, you may have to add some weight to that right hand horizontal pan tube -- but, if you can, rather than just adding dead weight, can you shift a battery, perhaps? It is a bit of a balancing act (in every sense of the phrase!).

    Andy

    Forensic Software & sUAV / Drone Analyst : Photographer : Videographer : Pilot (Portland, Oregon, USA): Trees=2, Ground=1, Props=11. :(
    The Ground Is The Limit™
    ---------- Forensic Drone Analyst : Forensic sUAV Analyst : Forensic Unmanned Aircraft Analyst : Forensic Drone Expert
     

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