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Dynamic balance - side to side


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#1 Michael Wilson

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Posted 18 August 2013 - 08:22 AM

Trying to dynamic balance my rig with a fairly light weight f55 yesterday. When I would do a spin test the rig would dip to the left. Usually it needs to be adjusted forwards or backwards. Only thing I can think of is the ab battery on my Marshall is not centered. But I've balanced before w this monitor. I have the mk-v 1.5" gimbal. I can static balance 360 degrees. But when I spin it, it eventually starts dipping to the side.

Thoughts?
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#2 Mike Germond SOC

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Posted 18 August 2013 - 08:44 AM

Do you have a telescoping post? There's a chance the top and bottom stages aren't aligned dead center. Or even a camera slightly twisted on the dovetail (more apparent with longer payloads). Or if your monitor bracket rotates off center on the post. I check all the possible off center items first when that happens.
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#3 Michael Wilson

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Posted 18 August 2013 - 09:36 AM

Yes, telescoping post. Ill double check the alignment.
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#4 Jerry Holway

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Posted 18 August 2013 - 09:43 AM

The camera can be twisted and/or tilted (as in Mike's pix), but the monitor and battery c.g.'s must be on a line that runs through the center of the post, or put another way, the 3 c.g.'s (monitor, battery, camera and accessories c.g.'s) must form a plane that is coincident with the vertical axis of the gimbal... or more simply, you cannot easily correct for dynamic balance if the c.g.'s are off center side to side.

 

If you can, remove the monitor and check where its c.g. is; same for the battery.

 

Jerry


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#5 Marc R. Berger

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Posted 19 August 2013 - 01:32 AM

This helpes me a lot to find the 3 c.g.`s. 

And especially a great little tool to determine the side to side off of the monitor etc.

 

Marc


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#6 Victor Lazaro

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Posted 19 August 2013 - 11:22 AM

I've heard about this Mickey technique, but it won't work in my situation with the Zephyr as the pole in not circular.


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#7 Mark Baluk

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Posted 19 August 2013 - 06:58 PM

The outer post is circular. I believe you should be able to use it on there, just collapse the post all the way.


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#8 Chris Van Campen

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Posted 20 August 2013 - 03:37 PM

We talked about the Zephyr "Mickey" method over here:

 

http://www.steadicam...17941&hl=mickey

 

Works like a charm, you just need a 1/4x20 bolt, a nut, and a bearing with 1/4" ID. I think it ran me $5 at McMaster Carr...

 

Seriously this method gets you 95% of the way there in no time... and the adjustments are intuitive while you're doing it. No trial and error. You quickly learn that 1 mm adjustment on one of the rods makes a big difference.

 

My 2 cents  :)


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#9 Mark Schlicher

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Posted 20 August 2013 - 05:00 PM

Chris do you have a pic? I don't quite grasp how it's working for you...thanks!


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#10 Chris Van Campen

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Posted 21 August 2013 - 11:30 AM

Attached File  zephyr_mickey2.jpg   112.71KB   276 downloads


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#11 Jerry Holway

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Posted 03 September 2013 - 07:52 AM

To be clear, the Mickey is a complete waste of time when the monitor c.g. is raised up from the battery c.g. – as it is in many sleds.

 

If the monitor is raised up on your sled, the sled needs to be front heavy without the camera, and the Mickey can't help you at all.

 

If this seems wrong to you, you could do the math, or you could just spin balance your rig (however you get there), then remove the camera, and it will be clear.

 

On the other hand, if the monitor c.g. is not raised up, then the camera c.g. will be directly over the center post, and you don't really need a Mickey to balance your sled in a separate step - you've got a lovely gimbal to do that already.


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#12 Eric Fletcher S.O.C.

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Posted 03 September 2013 - 12:18 PM

To be clear, the Mickey is a complete waste of time when the monitor c.g. is raised up from the battery c.g. – as it is in many sleds.


Actually Jerry if you'd think before you post you'd realize the the Mickey works with every sled configuration, maybe it's too outside of your limited (Tiffen only) experience

This thread is about side to side balance...
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#13 Jerry Holway

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Posted 03 September 2013 - 03:45 PM

LOL


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#14 Brad Smith

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Posted 28 September 2013 - 05:42 PM

To be clear, the Mickey is a complete waste of time when the monitor c.g. is raised up from the battery c.g. – as it is in many sleds.

 

If the monitor is raised up on your sled, the sled needs to be front heavy without the camera, and the Mickey can't help you at all.

 

If this seems wrong to you, you could do the math, or you could just spin balance your rig (however you get there), then remove the camera, and it will be clear.

 

On the other hand, if the monitor c.g. is not raised up, then the camera c.g. will be directly over the center post, and you don't really need a Mickey to balance your sled in a separate step - you've got a lovely gimbal to do that already.

Thanks Jerry,

 

As always you're level of understanding of all things steadicam is a valuable insight and resource. Please don't stop coming here on account of the rudeness (I could go on but I'd like to keep this forum a respectful and courteous place).


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#15 thomas-english

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Posted 29 September 2013 - 09:58 AM

The effects of the centrifugal force applied to the post will be different the higher or lower its applied. Hence a non coplanar monitor will balance great on the mickey and not be in dynamic balance.

This is what Jerry is saying and it seems entirely correct to me. Eric, if you dispute this howabout doing so with some science.
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