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Merlin balance drifting


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#1 Jeff Wong

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Posted 24 November 2008 - 04:51 PM

I purchased a Merlin a few weeks ago, and am having some problems keeping it balanced.

The camera I have mounted is an HV20 with WD-H43 wide angle, and Sennheiser MKE-400 mic. Just a little over 2lbs total. It's balanced quite well statically and dynamically, and the drop time is just about 1 sec.

I've gotten the hang of balancing it. However, I find the balance is drifting quite a bit.

When I tilt the camera to the side about 45 degrees, that's enough to throws the L/R balance off (the bubble is almost to the left or right). Tilting it 90 degrees to check the drop time completely throws it off (the bubble is all the way to the left or right, and can take up to 1/2 turn of the trim roller to level again).

At first, it was my camera wobbling around, but putting some rubber strips on the dovetail plate minimized that. If I grab onto the stage, and tilt it on the side, there is virtually no drift of the balance from the camera mount, so it must be something else jiggly.

I've found that the balance drifts when I grab on to the gimbal handle and tilt it (like in normal use or a drop test). It's almost like there is play in the trimming mechanism. I thought it might be the gimbal, but I tried to let go of the handle and do the same holding the guide ring, and same thing happens.

Is this normal? It really is a pain to have the trim thrown off after a gentle tilt of the camera. I'm not expecting the balance to stick forever, but I did hope it would retain trim well enough through gentle use and handling.

The caliper is locked, and the locking knobs are really tight. I had them loose before, and the balance shifted like crazy. I haven't tried tightening the allen bolts on the upper and lower spar, but they do feel reasonably rigid.

Any ideas? Trick or techniques?
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#2 Jeff Wong

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Posted 27 November 2008 - 02:07 PM

Perhaps everyone is using a big rig here? There must be someone that's using a Merlin with some experience to share.

The title for this thread may not be the best; I do know the balance will drift - but the question probably be better asked should it drift with a gentle movement/tilt?
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#3 RobinThwaites

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Posted 28 November 2008 - 05:30 AM

Hi Jeff

You should probably call the factory in Glendale on Monday (closed for thanksgiving today) however just as a couple of pointers

"there is virtually no drift of the balance from the camera mount" ANY movement of the camera or anything attached will have a huge result on the Merlin balance because it is a lightweight system.

" It's almost like there is play in the trimming mechanism. I thought it might be the gimbal, " Can you detect any slack in the gimbal or trim mechanism?

"Sennheiser MKE-400 mic. " I have seen the little bit of flex in the microphone shockmount cause unusual balance problems; microphones are often on the top of the camera which means that any movement will cause a great effect. Also make sure that the cable cannot move as this will affect the balance.

Robin Thwaites
Tiffen Europe, Oxford, England.
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#4 Graham Thomsen

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Posted 08 October 2009 - 08:28 PM

Jeff,

New to the forum but reading your post matches almost exactly a problem I am having with my
New Metal Gimbal. I am Flying a Canon 5D Mark II with a 17-40 L Zoom Lens Set to 40mm
and AF off. I was balancing on hole "M" because the more natural hole "N" blocked the battery door.

I find that using hole "M" requires the stage to be trimmed almost to the limit. So I moved it back
to "N" which improved things alittle...but same problem with drift like you. Do a drop test and
boom....balance gone.

Did you ever get this problem solved ? I do notice a very slight "play" in the gimbal itself...sort of
a very slight clicking sound when I move the handle up and down...did your do that ? Not sure how
tight it should be....

Graham
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#5 Robert Skates

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Posted 24 October 2009 - 08:41 AM

Jeff,

New to the forum but reading your post matches almost exactly a problem I am having with my
New Metal Gimbal. I am Flying a Canon 5D Mark II with a 17-40 L Zoom Lens Set to 40mm
and AF off. I was balancing on hole "M" because the more natural hole "N" blocked the battery door.

I find that using hole "M" requires the stage to be trimmed almost to the limit. So I moved it back
to "N" which improved things alittle...but same problem with drift like you. Do a drop test and
boom....balance gone.

Did you ever get this problem solved ? I do notice a very slight "play" in the gimbal itself...sort of
a very slight clicking sound when I move the handle up and down...did your do that ? Not sure how
tight it should be....

Graham


Gentleman,
I had the exact same issue. 5D Mark II w/24-105 lens set to 35mm. I use the "N" hole. Everything would be balanced perfectly then I do a drop test and the camera would then lean in that direction. Drop in the opposite direction the Merlin would be biased in that direction.

I sent the Merlin in for service. It came back from Glendale just in time for a 3 day job out of town. I did a quick test on a stand and the problem was much improved but not perfect. My job was in a remote National Park that required the crew to hike several miles between locations. I decided to just keep the arm, vest and merlin with camera on during a few of the hikes. It was easier than packing up and gave me a chance to practice operating up and down hills and over trails. Once I had the whole rig built and was operating the problem seemed to go away. Perhaps I noticed it less because I was concentration on the shot and keeping a level horizon. Or maybe the the long hike gave the gimbal a workout that eased up something that was sticking.
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#6 Graham Thomsen

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Posted 24 October 2009 - 10:17 AM

Robert,

Thanks for your reply. I spoke with Glendale and they sent me a new gimbal to try. Turns out that this new gimbal
behaved exactly as my old one. I had some concern that the slight clicking I mentioned might have been just mine. Looks
like this is the normal manufacturing tolerance. The factory was very helpful but given they don't have an 5D's hanging
around they don't know if its a specific merlin/5D interaction issue. The 5D is alot wider than long.....unlike most videocams
and perhaps this is an issue ?

Anyway...my current theory is that the camera MUST be shifting somehow. I have ruled out something inside the camera shifting
during the drop test. My current setup has me placing a piece of rubber on the dovetalk and then reefing down the screw as tight as I dare. I really want to use hole "M" because the video chew through batteries and I really need to change them without unscrewing...for obvious reasons.

However....still has the issue. I know you have to keep the zoom constant and given the camera is off....the focus is not a factor. The spar seems nice and tight as does the stage. Did the factory tell you what they did to your rig while they had it ?

Anyway..I just got my arm and vest and will be trying it out overseas next week.....hope I can duplicate your experience. The factory rep told me I am not the only 5D person he has heard from.

Any other theories would be welcome.
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#7 john ray

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Posted 25 October 2009 - 12:29 PM

Although I'm not flying my 5d Markii, but XHA1 w/no accessories..I'm having similar issues. I can balance the camera perfectly while it's on the stand but as soon as I take it off and do a few movements the balance goes way off.. It seems to work better when used with the vest and arm...I was about to try ordering a new gimbal myself Friday...but I see that did not work for you. Back to the drawing board I guess....
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#8 Graham Thomsen

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Posted 26 October 2009 - 06:29 PM

John,

I have noted that it seems to fly better with the arm and vest...but can't figure why. In my handheld setup I had
the spar adjusted smaller with one additional mid-weight. I found that with the spar closed it interfered with the
arm when I boomed. So....I made the spar max size and removed a mid-weight from the bottom and it seems
to behave alittle better during moves...but the drop test still throws it off in the direct of drop. I will be working
on it overseas and see where it gets me.

However...the arm and vest are very cool.....Olive Oil is happy that Popeye has stopped complaining....:)

Graham
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#9 James Elias

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Posted 06 November 2009 - 06:48 AM

Hi Gents:

It sounds to me as if something is moving... bear in mind that the Canon 5D has no locating pin to stop the camera from turning on the plate. Ensure you use some gaffer tape either side of the camera mounting hole to make a small pad the camera body can grip onto when you tighten down the screw.

The slower you make the drop time, the more sensitive you will make the trim - if you have a drop time over one second and the camera turns slightly when you go to test the drop time, it will loose trim! Likewise, A slight turn on the trim controls with slow drop times will make a world of difference. The effect will be minimized with a faster drop time of around one second exactly. It's just physics!

Best,
James
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