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Sled won't stay level


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#1 Michael Wilson

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Posted 08 November 2013 - 12:38 AM

I have the MK-V genesis sled with a 1.5" post and gimbal with a 3a style topstage.  I have noticed that  after I balance the sled on the stand and then put it on the arm it is just a touch off level.  Not debilitating but a PITA for sure.  After experimenting I noticed that after balancing then doing a drop test or docking the rig and going back to balance the rig on the stand the rig again is just a touch off level.  

 

So I went over to a fellow ops place to swap out PRO parts to try and track down the problem. Swapped out topstage for DB2, and MK-V gimbal for a PRO gimbal (brand new btw).  Still the problem persisted.  We tried almost every combination and after balancing to level and doing a simple drop test the rig would go slightly off level.  

 

The base of my sled has a knurled mount.  Outside of the post is threaded with a screw down fastener.  Put some loc tite on it and tightened the hell out of it.  I also tightened the kip handle on the telescoping post section.  I tightened the monitor mount as well.  It is a cinetronic yoke that has a plastic insert in the spud which I can move if I push hard enough.  

 

So something is moving right?  Any other information that would help diagnose the problem? 

 

Anyone know the cost or resources involved in switching to a PRO style lower base mount? 

 

BTW the Pro cinelive sled balances wonderfully and retains balance.   


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#2 Alan Rencher

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Posted 08 November 2013 - 01:09 AM

Have you checked your gimbal?
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#3 Michael Wilson

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Posted 08 November 2013 - 01:19 AM

Well I swapped out my gimbal for a new pro gimbal and still the same results.  Do you mean anything else by checking the gimbal?


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#4 Benjamin Treplin

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Posted 08 November 2013 - 04:18 AM

After the drop test what direction does the rig go? Drop test with lens up -> rig: tilt up or tilt down or off level left or right? 


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#5 Jerry Holway

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Posted 08 November 2013 - 08:13 AM

If you are very neutrally balanced, the rig is going to be very tender - subject to the slightest disturbance and go off level if anything is loose.

 

If so, it may be that the cabling inside the post is laying one way or another after the drop test, and that might be enough to affect your balance.


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#6 Michael Wilson

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Posted 08 November 2013 - 09:43 AM

@Ben - Sled always tilts right.  Bubble always breaks the center line on the left of the level.  Maybe 10% of the bubble creeps over that left line.  

 

@Jerry - I've tried varying drop times.  Cable is an interesting culprit.  The cable does move inside the post.  I don't think I'll want to remove the cable as I've put Loc tite on the base and want to let it cure.  I wonder if I can put some sort of stuffing in the post to keep the cable from moving.  


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#7 Michael Desiderio

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Posted 26 November 2013 - 03:21 PM

I'm betting on the cable as well.  Recently ran some cable through one of our sleds and now have the same result.  Not debilitating when operating, but a bit of a nuisance when you're checking your gear.


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#8 Eric Fletcher S.O.C.

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Posted 26 November 2013 - 06:17 PM

Sounds like the post has been ground off center
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#9 Ken Nguyen

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Posted 26 November 2013 - 10:21 PM

I second Eric.

Also, check to see there is any play at your topstage.

(strongly pressing the topstage side-to-side and for-aft with your finger against the post)

 

Cable shifting inside the post (assume your cable is original or made by professional) is not really affecting the balance of the rig, unless you balance it neutral (0 drop time)

 

Cheers,

 

Ken Nguyen.


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#10 Jerry Holway

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Posted 27 November 2013 - 09:01 AM

BTW - post roundness is irrelevant once the gimbal is clamped - all the centering is in the gimbal.

 

An out of round or centered post is perhaps annoying if you rotate the gimbal relative to the post, has zero to do with balance once the structure is locked to the gimbal via the inner race of the pan bearing.

 

Check out the JR, Merlin, etc. for the logic.

 

Many posts - especially the metal ones - are egg-shaped when clamped - no problem.

 

Most likely culprits are loose bits like the top stage, but anything can shift. I've seen the internal cable affect balance when the sled is very lightly balanced top to bottom - some of the internal cables are quite heavy.


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#11 thomas-english

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Posted 27 November 2013 - 02:13 PM

First place I would look on this sled is if the base is rotating slightly. it need only be half a degree of play. Next is cables especially post cable. 


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#12 Michael Wilson

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Posted 28 November 2013 - 12:12 AM

I took the entire sled apart and tightened everything.  Going to do some more testing when I get back to town this weekend.  

 

Base is very tight.  Still could be the base.  I mean why not.  

 

So lets say its the center post cable?  How would I go about correcting this?


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#13 thomas-english

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Posted 28 November 2013 - 03:25 AM

Well try with zero cable in there and see if the balance falls over. If it is the cable then contact Ash at MK-V because the cables have been improved over the years. The old ones did slop about and the new ones are coil rigged. 


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#14 Michael Wilson

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Posted 04 December 2013 - 05:26 PM

I did some more testing.  Made a nice little document with pics.  I took the center post cable out for these tests.   

 

The majority of the times the sled goes off balance is in the side to side.  Everything is tight.  

 

 

 

Attached Files


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#15 Ken Nguyen

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Posted 04 December 2013 - 08:24 PM

Michael,

Let go through the list:

- Post cable is removed. Checked.

- Change Topstage.  Checked.

- Change gimbal.  Checked.

- Using solid weight cage to eliminate moving part inside camera problem.  Checked.

 

The list of possible problems is now as below (in order of troubleshooting):

- Tighten all screws which connect topstage and battery hanger to the post.

- Check the plastic insert in the spud of your monitor bracket.

- Shake the battery hanger and also the monitor to hear if there is any noise.  If yes, open it and look for loose part.

- Change the post to another one.

 

If all of the above won't solve the problem, send the sled out to a nearest well-known Steadicam repair and service.

 

Cheers,

 

Ken Nguyen.


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