One day she is happy, the next she isn't! But this is our Movi MR not my girlfriend!

Discussion in 'MōVI MR' started by Sam Leggett, Feb 22, 2014.

  1. Sam Leggett

    Sam Leggett Member

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    Hello All,

    Despite being a member for some time and reading all your invaluable posts, this is my first thread, and comment even.

    We have a Cinestar HL and have started flying with our new Movi MR. The first few flights were done in really marginal gusty and turbulent conditions and the results blew us out of the water. Continued testing in better conditions showed that the footage while hovering was so still it looked like someone had paused the TV! We haven't spent too long tuning - we just followed Tabb's videos and away we went, couldn't believe our luck!

    However, using the same set up we have started having issues. Today we had a small, but noticeable horizon drift and some vibration. The conditions were still a bit windy but nothing on other days. One thing we have noticed just recently and do not understand is that although the camera is perfectly balanced in the tilt - the camera sits perfectly in any tilt orientation, the roll wants to return to horizontal. How is this possible?! If we raise the camera so tilt is too high and the camera wants to tip over slightly, either forwards or backwards, THEN roll is balanced properly sitting in any roll orientation. Its as if the horizontal bars from the roll bar to tilt motor must droop, but they are carbon! We have had no hard landings or mishaps of any kind either that would stress the Movi.

    This is our stiffness set up:

    Pan: 80
    Roll: 70
    Tilt: 60

    And here is a photograph of our set up. We are flying a C300. We have put our video downlink transmitter, battery and HDMI converter on the tilt bar so there are no cables affecting balance. The lens is not our flying one, it has just been put on for problem solving... we have been flying with a large 24-70mm lens.

    We know we haven't spent too long on our tuning, and we know our big heavy lens choice is not optimum, but we do not understand how we have had such great results one day and bad ones the next.

    Any help would be greatly appreciated!

    Oh and I know someone will say please up load footage, but we do not have the editing software to cut to the appropriate bits. If anyone knows what you need to do that with an MXF file I will get straight on to it.

    Many thanks for your time,

    Sam
     

    Attached Files:

  2. Gary Haynes

    Gary Haynes Administrator
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    Sam there is a very slight amount of resistance from the cable on the roll axis. So you may see it move a bit when you are setting it up. Not fast, not with much force. But may be there regardless.

    Was there any kind of temperature shift that might have affected the vibration dampers? For example you flew originally above freezing and the shots with a bit of wiggle were below freezing?

    Best way to post video is simply take a clip in your edit software and load it to YouTube or Vimeo. Then embed the video by clicking on the small screen icon at the top of the typing window and pasting the URL.
     
  3. Sam Leggett

    Sam Leggett Member

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    Hi Gary,

    Many thanks for your reply, we thought about the cables and trimmed off the cable ties to see if that made a difference. No joy. Also if we balance the camera so the tilt is slightly top heavy and the camera wants to topple then the Roll is perfect... it sits exactly where it is left just as it does in Tabb's tutorials.

    There has not been a great deal of temperature change here, not enough to change the stiffness of the rubber I wouldn't think. Its always cold and miserable at the moment here!

    Unfortunately we don't have any editing software! My business partner is a freelance TV cameraman and all his normal work goes off to the editors, while I am a model flying hobbyist of many years.

    Sam
     
  4. Gary Haynes

    Gary Haynes Administrator
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    Sam the next best thing would be some photos of your setup and maybe a cell phone video of what happens as you balance.
     
  5. Sam Leggett

    Sam Leggett Member

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    Hi Gary,

    Here is a short clip of our balance issue:



    When in the air the horizon (flying at the beach - the ultimate acid test) was just slightly higher at one side.

    The vibration is harder to describe. Its a high frequency judder - we think in the pan. At some points in the flight it is worse and sometimes it goes away. The airframe has been great in the past and the props are all balanced and have not been knocked. The pilot go pro downlink seems very nice - although we are going to record from there and watch on a big screen to test.

    Thanks very much for your suggestions,

    Sam
     
  6. Janne Hoglund

    Janne Hoglund Member

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    Clearly looks like you need to increase the height of the roll bar, but as I understand things that adjustment is non existent now with the new alu roll bar?
     
  7. Sam Leggett

    Sam Leggett Member

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    Yes that is what I thought!

    We have been racking our brains. We have taken the roll bar off and turned the roll motor 180 deg and put it all back just in case the axle was bent by some mystery incident... and it is not. Our next effort was putting a thin shim on the bottom bolt between the roll bar and the triangular plate that attaches the whole thing to the motor. This has fixed the problem. Our shim is a touch thick and will need filing down as the camera shows a tiny tendency to want to carry on rolling at extremes.

    This must mean that we have put a very slight bend in our triangular plate, or the roll bar as a whole, but I don't think that would bend easily with all those triangles and L shaped aluminium. This problem has not been through any heavy landings, I fly it like its made out of fine cut glass! However, it has been in the car on short journeys with the camera still attached, and, despite it being on the seat with plenty of soft shock absorbing I think may have flexed the aluminium bracket. LESSON LEARNED!

    I just only hope now that this, leading to out of balance roll, has also been the cause for the recent shakes and horizon issue! We just missed the best flying day in God knows how long but at least we weren't on a job!
     
  8. Sam Leggett

    Sam Leggett Member

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    Ok, a bit more detective work... the said triangular roll motor mount that the ali roll bar fits on to appears to be carbon fibre in the photos in the Freefly store. Ours is Aluminium. Could anyone who knows please confirm whether or not there are carbon fibre mounts out there?

    Many thanks!
     
  9. Gary Haynes

    Gary Haynes Administrator
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    Sam the photos are not up to date. You have the correct version, aluminum.
     
  10. Sam Leggett

    Sam Leggett Member

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    Thanks Gary, ok well we have a slightly thinner shim now and the roll balances perfectly again. At least we have found the problem.

    It does make you think twice about mounting it on a car as a tracking cam!
     
  11. Janne Hoglund

    Janne Hoglund Member

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    And maybe Freefly should modify the alu rollbar so that the user could adjust it a little in height?!
    Carbon fibre does flex, but aluminium does bend slightly under load...
     
  12. Gary Haynes

    Gary Haynes Administrator
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    Sam what shims did you change?
     
  13. Sam Leggett

    Sam Leggett Member

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    Hi Gary,

    Um, my bad wording - there were no shims originally, I meant today we changed what we tried yesterday to something thinner.

    We now have a thin washer between that triangular aluminium motor mount and the aluminium roll bar on the bottom screw only. The top two screws are exactly as before. This angles the two carbon tilt tubes up very slightly. The roll now balances as it should. However, thinking about it all and staring for a good many minutes repeatedly I cannot see any sort of bend in either the triangular mount or the roll bar, and despite the not insignificant leverage caused by the weight of the camera (C300) I don't think slowly coming off a kerb in a car with the Movi on the rear seat seatbelted in would bend it. But the bottom line is something has changed as our roll was fine and now its not. Its a bit of a mystery, but we have been testing in handheld mode today and all is good and well.
     
  14. Gary Haynes

    Gary Haynes Administrator
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    Sam that's interesting. Others on the forum have used the 300 and this is the first I have ever heard of anyone with any rig needing to shim the roll beam.
     
  15. Joe Lawry

    Joe Lawry Member

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    After watching your video i am unsure what the problem is.. the roll on my MR always goes back to center (unlike the cinestar3 did) and its been like this since day1.. I've never had a problem.
     
  16. Sam Leggett

    Sam Leggett Member

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    Hi Gary,

    I don't think its the C300.. I think it is the Movi, but I am really at a loss for what it might be. Roll never used to self centralise when tilt was balance correctly, but now it does. And like I said the worst that has happened is going down a kerb in a car with it on the back seat with the camera still attached.

    Thanks for checking in Joe, I have been going from the online tutorials... the roll should sit in any position just like tilt does. Ours did, and now it doesn't!

    We still have slight vibration issues too, only ever so often. Sometimes it looks as if the shot is on pause it's so steady and other times it gets a judder on. The issue is that it ruins nearly every sequence! We have a number of things to try and will let you know.
     
  17. Janne Hoglund

    Janne Hoglund Member

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    I dont want to be rude but if Roll does self center, it needs to be moved uppwards, yes?
     
  18. Sam Leggett

    Sam Leggett Member

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    Hehe its not rude, but there is no "upwards" adjustment on roll. The only thing you can move upward is the camera - to adjust tilt, but tilt is perfect (see video) if the camera is raised to make the roll perfect then its too high for tilt and so topples forwards or backwards.
     
  19. Janne Hoglund

    Janne Hoglund Member

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    Thats what I think is the problem, the lack of roll adjustment.
    Talking about bicyle frames it is a well known fact that Alu frames get a little distorted as time goes by, and depending how hard they are used. As of today most high end frames are Carbon fibre.
    Carbon fibre does flex a little, how much depending of the amount and direction of the fibers used in the item.
    Alu does to flex but does not, like carbon fibre, 100% ¨flex back to original shape¨.

    I think maybe Freefly need to modify the rollbar to allow a little adjustment on the roll, dont you agree?!
     
  20. Sam Leggett

    Sam Leggett Member

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    Yes perhaps a bit of roll adjustment in the vertical plane might be beneficial. This afternoon I took everything apart and put the bits on a perfectly flat steel surface. Nothing is bent at all. And so the mystery of roll continues...
     

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