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Steadicam Merlin Arc Distance and Magic Formula


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#1 Ihab Ali

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Posted 15 November 2011 - 03:21 PM

Hello,
I'm having some issues using the magic formula spreadsheet with my Merlin and gopro 3d setup. I used the formula successfully in the past with my Canon 5&7Ds, but I noticed for the Gopro 3d setup(at 370grams) the Arc distances calculated are smaller than the arc distance the Merlin is capable of. The minimum achievable arc distance as measured from the top of the stage to the setscrew plane is 225mm..the formula comes up with numbers like 216mm depending on my vertical C.g(which I can control with some of the included gopro accessories). I noticed also that the manual states that the minum achievable arc distance is just under 217mm(on page 13). Is something wrong with my Merlin or am I measuring things incorrectly? The caliper hinge is at the first mark when the arc is at the measured minimum of 225mm.

I'm actually able to get a fairly balanced setup when I somewhat ignore the settings and go with setting the balance manually(making sure the fall time is slow enough), but I'm not getting a perfect dynamic balance(there is wobble/imbalance when I pan from stationary)...not sure if this is because of the arc distance or because the camera is simply too light.


A related quick question just to make sure I understand everything correctly, the stage marking is the one on the left handside looking from the top with the front weight infront of you, correct? The reason I ask is I've never been able to use the recommended stage mark settings from the spreadsheet even with the heavier cameras.

Regards,
Ihab
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#2 Alan Rencher

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Posted 16 November 2011 - 05:21 PM

Hello,
I'm having some issues using the magic formula spreadsheet with my Merlin and gopro 3d setup. I used the formula successfully in the past with my Canon 5&7Ds, but I noticed for the Gopro 3d setup(at 370grams) the Arc distances calculated are smaller than the arc distance the Merlin is capable of. The minimum achievable arc distance as measured from the top of the stage to the setscrew plane is 225mm..the formula comes up with numbers like 216mm depending on my vertical C.g(which I can control with some of the included gopro accessories). I noticed also that the manual states that the minum achievable arc distance is just under 217mm(on page 13). Is something wrong with my Merlin or am I measuring things incorrectly? The caliper hinge is at the first mark when the arc is at the measured minimum of 225mm.

I'm actually able to get a fairly balanced setup when I somewhat ignore the settings and go with setting the balance manually(making sure the fall time is slow enough), but I'm not getting a perfect dynamic balance(there is wobble/imbalance when I pan from stationary)...not sure if this is because of the arc distance or because the camera is simply too light.


A related quick question just to make sure I understand everything correctly, the stage marking is the one on the left handside looking from the top with the front weight infront of you, correct? The reason I ask is I've never been able to use the recommended stage mark settings from the spreadsheet even with the heavier cameras.

Regards,
Ihab


Try adding some weight to the top stage.
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#3 Ihab Ali

Ihab Ali

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Posted 17 November 2011 - 03:47 AM

Hello,
I'm having some issues using the magic formula spreadsheet with my Merlin and gopro 3d setup. I used the formula successfully in the past with my Canon 5&7Ds, but I noticed for the Gopro 3d setup(at 370grams) the Arc distances calculated are smaller than the arc distance the Merlin is capable of. The minimum achievable arc distance as measured from the top of the stage to the setscrew plane is 225mm..the formula comes up with numbers like 216mm depending on my vertical C.g(which I can control with some of the included gopro accessories). I noticed also that the manual states that the minum achievable arc distance is just under 217mm(on page 13). Is something wrong with my Merlin or am I measuring things incorrectly? The caliper hinge is at the first mark when the arc is at the measured minimum of 225mm.

I'm actually able to get a fairly balanced setup when I somewhat ignore the settings and go with setting the balance manually(making sure the fall time is slow enough), but I'm not getting a perfect dynamic balance(there is wobble/imbalance when I pan from stationary)...not sure if this is because of the arc distance or because the camera is simply too light.


A related quick question just to make sure I understand everything correctly, the stage marking is the one on the left handside looking from the top with the front weight infront of you, correct? The reason I ask is I've never been able to use the recommended stage mark settings from the spreadsheet even with the heavier cameras.

Regards,
Ihab



Try adding some weight to the top stage.



Thanks Alan, I did add some accessories to the camera to increase the weight, I also raised the mounting point to get a higher C.G. With the smallest achievable arc distance like I said, I am able to get proper static balance(with 1sec+ drop time). But trim and dynamic balance become very tricky: horizontal trim is extremely hard to achieve(very touchy) and the dynamic balance test always fails(panning results in dippings). Do you think this is because the camera is too light or is there a different way to setup the dovetail plate and gimbal position to get perfect dynamic balance?
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#4 Alan Rencher

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Posted 17 November 2011 - 10:44 PM

I haven't used the merlin, but with larger rigs, adding weight to the top stage is what you need to do to get light cameras balanced. My thought would be to add enough weight to the top to get it about the same as the 7D setup that you're used to. After that, It should be more familiar to balance.
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