Severe vibrations last might

Discussion in 'MōVI M15' started by jim mundell, Oct 1, 2015.

  1. jim mundell

    jim mundell Member

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    Hello, my M15 had vibrations periodically all nite on a live tv shoot. Client not too happy.
    Used a fs700 (client supplied), stripped down (no top handles, evf, hot shoe), no focus motor, on a canon 16-35 with speed booster. It balanced out perfectly, stayed in every position on each axis moved freely. Did autotune on the movi handle then eventually moved to the Movi ring. Once I tuned it on handle it came in around 235 pan/ 56 roll / 117 tilt and had to back it down to have it stop vibrating. Moved to the ring and had to back it down even more. Think it was around 198 / 54/ 98?? Or close to that.
    Motors all read between 0-3.
    Had times when it just vibrated during shots, when it was still, etc. Wasn't consistent either. Could repeat shots and only did it sometimes. Got to the point that I had to lightly touch Movi (with other hand on ring) to stop vibrations. Then it was fine for a bit.
    Redid auto tune earlier in the night and got same results.
    Have a ticket into FF but have gotten little help so far. All he said my balance was off. Due to my readings of roll being half of tilt. I have shot a ton with this movi and this camera and other cameras and my roll is always lower then the others. Have never had issues before. He hasn't given me what the proper ratio should be. I also remember similar ratios between roll and tilt when I took the Movi class at Abel too and have seen others balance with same ratios.

    I have balanced Jib and rob heads for over 20 years so I have a pretty good feel for when things aren't balanced right. But I can always be wrong. Not sure what else I could have done to balance better though. Used thin flexible cables that had slack in them so as not to pull on axis.

    Can anyone give some help please? Also where can I find detail info on the settings in the GUI? Have only found some info in FF videos and info.
    Thanks.
     
  2. Brett Harrison

    Brett Harrison Active Member

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    Friends don't let friends use autotune.

    That 198 is way too high. If you're getting vibes, start knocking down the values until it stops. For most situations on heavy setups you will be fine with anything over 40 (notwithstanding very energetic moves)
     
  3. jim mundell

    jim mundell Member

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    Thanks Brett.
    I autotune most times and then tweak as pre autotune to check, but have done manual tune and gotten similar numbers. Thats why I stayed with autotune mostly. Thing is it stopped vibrating when I sat down to tune it at that 198. As I started to use it, it vibrated more and more. Lowered it, was fine then did it again, but didnt seem to matter. Never got to 40.
    40 huh? Thats seems low. If your running with athletes would you still keep it at 40? How about in or on a vehicle?
    What are your other settings around? Know it depends on camera, situation, etc.
     
  4. Brett Harrison

    Brett Harrison Active Member

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    You should be suspicious when a given motor is so much higher than the others. There's going to be some variation but when a motor is artificially stable due to a pendulum (that is, bottom heaviness in the tilt axis will dampen the roll and tilt motors for zero angles), that will become apparent when you reach different orientations during operation (hence why you didn't get vibes when you were balancing and tuning). Likewise if it's top heavy but well centered, once you stat tilting or rolling, it becomes too much for the system but this was masked while you were tuning). So you need to test a variety of orientations before you sign off on a balance/tuning.

    You'd be surprised what 40 gives you if you've also balanced the axes well. Give it a try.
     
  5. Brett Harrison

    Brett Harrison Active Member

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    Before you head out, look at the motors chart to see how hard the motors are working as you rotate through angles on the motors (use the remote and lift one side of the handle for the pan motor). If it's outputting significantly more power at a given angle (more than when the angles are zeroed) while at rest in that angle, it's possibly due to a poor balance. If you have a good balance you have to go to very high stiffness settings to ever get vibrations.
     
  6. jim mundell

    jim mundell Member

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    Thanks again for the info Brett.
    The confusing part is this thing stayed put at every axis at every angle. Didnt drift or fall to any particular side when balancing. Didnt pendulum, so low was good or fall over the top from being top heavy, didnt roll off center in roll axis and stayed put it the pan axis when rolling handles. Cables weren't pulling on anything.
    Will check the numbers with the test you mentioned next time but Im pretty sure it was balanced.
    What kind of numbers are you normally getting in the tilt and roll axis?
    Any other thoughts?
     
  7. jim mundell

    jim mundell Member

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    Brett, what camera setup you using to get a 40 on pan? Consensus seems to be that is pretty low.
     
  8. Brett Harrison

    Brett Harrison Active Member

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    Hi Jim just saw this now.

    I usually work with camera setups weighing near the limit, so I can go very high with the stiffness settings, usually around 100 to 200.

    I don't recommend using 40 for the sake of hitting that number - just pointing out that stiffness is a tool - don't ever use more than you need IMO. At the same time: the higher the stiffness number you can use without getting vibes the heavier the setup/the better the balance. High, stable stiffness numbers are symptomatic of a good balance.
     
  9. Brett Harrison

    Brett Harrison Active Member

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    In summary, your vibrations are due to a bad balance or your camera setup is too light for 198 stiffness setting. But likely the former.

    give 40 a try on all sorts of weights. You'd be surprised what it does for you even with very heavy setups.

    Once you realise this, you will see that high stiffness settings only come into play where high forces are in effect, including a biased balance (i.e. not a neutral balance which will be more-or-less balanced for all angles on the motors)
     
  10. Robert Eder

    Robert Eder New Member

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    With your setup the numbers look fine to me. What Gyro filter and Output values are you using. Also what PTR stiffness settings?

    Usually pan is the biggest value, then tilt, than roll, however this depends on the cam setup. Yours is rather long so pan and tilt gains should be high.

    If you are around 40 something is wrong. Check the screws of the toad or on the handle connection to see if something is wrong. Also really check the pan balance!

    Greetings
     

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