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Losing static blance after checking drop time


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#1 Katerina Kallergis

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Posted 15 August 2009 - 09:34 PM

Hey everyone,

Having an issue on my Masters here. I've been static balancing my sled and finding that when I check the drop time the sled will then have lost it's balance. It'll then lean slightly forward, sometimes it'll lose its side to side balance, too. I'm not sure exactly but I think it may have to do with the topstage's dovetail lock. At one point, while holding the sled horizontally, I noticed the camera and dovetail sliding slowly towards the floor. I then tightened all the screws on the lock and didn't notice the sliding motion again, but it still lost static balance after each drop time check. Then I thought maybe it was the dovetail, I changed the dovetail I was using and the problem persists. Am I doing something wrong? Is it mechanical? What?

Your input would be greatly appreciated!

Thanks in advance,
Kat
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#2 Eric Fletcher S.O.C.

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Posted 15 August 2009 - 09:57 PM

Having an issue on my Masters here. I've been static balancing my sled and finding that when I check the drop time the sled will then have lost it's balance. It'll then lean slightly forward, sometimes it'll lose its side to side balance, too. I'm not sure exactly but I think it may have to do with the topstage's dovetail lock. At one point, while holding the sled horizontally, I noticed the camera and dovetail sliding slowly towards the floor. I then tightened all the screws on the lock and didn't notice the sliding motion again, but it still lost static balance after each drop time check. Then I thought maybe it was the dovetail, I changed the dovetail I was using and the problem persists. Am I doing something wrong? Is it mechanical? What?



Are you changing the gimbal position in order to adjust drop time, or are you just checking drop time? A bottom heavy rig will fool you into thinking it's balanced and when you go towards neutral your balance inaccuracies will start to show.

If you are not changing the drop time and it's changing balance then you have something loose, mounting plate, top stage, bottom stage, cables. something.
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#3 Mike Germond SOC

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Posted 15 August 2009 - 09:59 PM

I'll list my recent problem and solution in hopes that it helps you out somehow..

PROBLEM:
Flyer LE in perfect static balance...rotate 180º and the nose is dipping pretty badly. Gimbal appears to be in balance. Tiffen guarantees that my carbon fiber post is as round as round can be.

SOLUTION:
Tiffen said there was a loose or broken part at the top of the post that attached it to the stage. I believe the part was warped or something, causing the balance to be out of whack.



just something to check
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#4 Eric Fletcher S.O.C.

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Posted 15 August 2009 - 10:02 PM

I'll list my recent problem and solution in hopes that it helps you out somehow..

PROBLEM:
Flyer LE in perfect static balance...rotate 180º and the nose is dipping pretty badly. Gimbal appears to be in balance. Tiffen guarantees that my carbon fiber post is as round as round can be.

SOLUTION:
Tiffen said there was a loose or broken part at the top of the post that attached it to the stage. I believe the part was warped or something, causing the balance to be out of whack.



That's simple, the Gimbal is not concentric, the bearings are out of alignment
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#5 Katerina Kallergis

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Posted 15 August 2009 - 10:18 PM

Thanks for the replies.

No, I have not moved the gimbal position before checking drop time. I also noticed it goes off balance after I spin balance, as well. I thought I checked everything that could be loose. I'll give it another check though. I'll even check it without the cables attached to be sure there are no outside influences. If it doesn't do it, then I'll know it's the cables. Is it at all possible for the fore and aft, side to side adjustments to not lock into place?

-Kat
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#6 Mike Germond SOC

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Posted 15 August 2009 - 10:40 PM

Eric,

Dan Ikeda told me they suspected that as well so they realigned the gimbal and balanced the sled...when it was still out of whack, they dug deeper and found the warped part
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#7 Jerry Holway

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Posted 17 August 2009 - 07:04 AM

Kat-

It sounds like one or more of these:

play between the Yoke and the pan bearing - if you tip the rig on the side, (make those two bearings vertical) can you see some space growing or does the sled shift to one side?

Looseness in the stage - lots of stuff to tighten here, including bearing pre-load.

Misalignment of the yoke to the pan axis (test static balance, pan 90, then 180 degrees... does it hold?). They adjust this at the factory, of course it can shift over time or with a bump.

Call Peter!!

Jerry
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#8 Katerina Kallergis

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Posted 18 August 2009 - 09:51 AM

Thanks for the info Jerry. I've called Peter and he said he'll get back to me this week. Once I know what the problem is and how it is fixed I'll be sure to post it.

Thanks again to everyone.
-Kat
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#9 Katerina Kallergis

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Posted 20 August 2009 - 04:16 AM

Well, I took apart the top stage. Turns out there was a loose screw in there...not sure what for. No holes anywhere the screw may have belonged to. And I'm shocked I never heard it rolling around in there. hmmm. Anyway, after spending hours trying to put the stage together, successfully thank god, I still noticed the dovetail lock on the stage not locking properly. I think I may just need a new one. Any ideas where I could get this? Is that even a fix? Or, is there more to it than just replacing that one part?


It's 5:00am...yea, gonna go pass out now.


Thanks again,

Kat
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