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faulty gimbal or bad DB?


Wing Gee
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Trying to figure out if my gimbal is out of whack or i'm just not balancing correctly. When I static balance. Then spin the rig 180 degrees from it's original position, (camera facing opposite direction) the top of the rig is now tipped a bit forward. Trying to figure out if this is a gimbal issue or me not spending enough time trying to get it in to dynamic balance.

 

Thanks!

Wing

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Hi Wing,

 

It's almost definitely a balance problem. Unless you hear or feel any strange noises, grindings, or other odd phenomena coming from the gimbal, you can be assured it's most likely operating properly.

 

Dynamic balance is a tricky thing at first - and can be tricky for long after that, too. If you haven't already, study Jerry Holway's Dynamic Balance Primer. Also, read through other posts here regarding the issue. There are a lot of different tips and techniques you can try out.

 

Best of luck,

Afton Grant

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I guess i should have mentioned this first. The gimbal I have is a home built gimbal, I got it on a groupbuy on hbs. the bearings are really smooth. One thing i'm not certain about is whether or not the yoke is centered with the rest of the gimbal.

 

This gimbal is on my 3a sled.

 

Here are some pictures of the gimbal.

 

http://www.turborocco.com/wingcam2/gimbal/

 

I guess i should have mentioned this first. The gimbal I have is a home built gimbal, I got it on a groupbuy on hbs. the bearings are really smooth. One thing i'm not certain about is whether or not the yoke is centered with the rest of the gimbal.

 

This gimbal is on my 3a sled.

 

Here are some pictures of the gimbal.

 

http://www.turborocco.com/wingcam2/gimbal/

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I have to concur with Peter. What you have here is a faulty gimbal. The tilting you have described after panning 180 indicates that the pan axis is not aligned with the tilt axis (the axis in the yoke handle). Depending on the design of your gimbal, this could be corrected to some degree by placing small shims between the pan housing and the yoke. This will effectively move the pan axis into position so that it agrees with the tilt axis.

 

On a side note, the misalignment you describe is the reason why a really good gimbal (PRO, XCS, Tiffen) costs upwards of $5-7k. The precise alignment of the axes is all in the design and the machining.

 

Good luck,

 

Jeff L. Clark, SOC

Los Angeles

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Wing--

 

This sitation is common for gimbals whether they are home made or a factory produced unit.

 

Most often, the pan bearings have worn to the point of failure to align with each other and the bearing carrier thus allowing your rig to balance in one position and not in another.

 

What has to happen is a precise measuring of the components and new bearings installed along with shims to correct the dimensions inside the bearing carrier housing. Once things are realigned and reassembled correctly, your repositioning or panning of the sled should not affect the trim of the sled.

 

Best,

 

Brant S. Fagan, SOC

Steadicam/Camera Operator

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Thanks everyone for the advice and comments.

 

The bearings are all new (new gimbal). I think i just need to shim it correctly. which i had to do with a older crappy progear 3a gimbal.

 

At least i have a better understanding now and not freaking out cause i can't get the sled into DB.

 

Thanks!

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  • 12 years later...

Hey everyone,

I'm reviving this thread as it's the closest I've found to my situation, and haven't quite found a solution anywhere else on the forum.

Basically, I'm having the classic "is my gimbal centered?" issue, but I think my issue may be because of slop rather than it not being calibrated correctly.

What is happening: When pointed perpendicular to the handle, I can balance the sled perfectly. If I rotate it 90 or 180 degrees, as described in the U2 manual, it's out of whack. From the camera's perspective, it tilts forward and yaws toward the handle. The odd thing is that after adjustments, it always tilts forward regardless of where it's pointed. Since it tilts in both directions on the axis, this makes me think it's slop in the bearing rather than misalignment, which I expect would tilt it in the same direction regardless of which was the sled was pointing. 

What I've done about it: To start, this is a Flyer LE gimbal, so maybe it just has looser bearings than the big boys. I took handle off the yoke, and the yoke bearing feels tight and correctly adjusted. I removed the yoke from the pan bearing and tested the two tilt bearings, and they felt good. While mostly disassembled, I felt the large pan bearing and it feels like it has was slop. It looked like it was a cage bearing set into a race and retained rather than a sealed bearing, and didn't seem like there was a way to tighten it. After reassembly, I could feel and barely hear the slop coming from the pan bearing. I retightened everything I had the means to get at, short of the circlip holding the pan bearing in.

Long explanation I know, but hopefully enough that someone might recognize my issue. Any thoughts on if the pan bearing is the cause, or if it's a different bearing or something entirely else? And if all else fails, any recommendations on who to send it off to, Tiffen included?

Thanks so much for your help on this and for the best forum on the internet!

Scott

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  • 1 month later...

Update time! 

I eventually got my gimbal all nice and centered, and figured out what my issue was. Effectively, the two pins that hold the pan bearing centered were over tightened, which pinched the yoke and distorted how everything sat. I called on my experience working at a bike shop college,  and started by backing both pins out until I could feel slop, making sure to feel for slop in the pins and not the little bit of shift the pan bearing has when not under load. Then I very gradually tightened the pins until the slop was removed but wasn't binding. Then I followed the standard recentering procedure and everything was good to go. I'm sure more qualified techs have a precise tolerance for setting the pins, but I couldn't track down that info and this seems to work well for me so far.

Hopefully this helps someone else out later!

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