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2" Gimbal


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#1 Tammy Jones

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Posted 03 March 2009 - 12:04 AM

Who can tell me what are the advantages and disadvantages of a 2" post and Gimbal?
thanks,
Tammy
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#2 Eric Fletcher S.O.C.

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Posted 03 March 2009 - 12:16 AM

Who can tell me what are the advantages and disadvantages of a 2" post and Gimbal?



It's more about the center post. You increase stiffness when you increase the diameter of the post. go from a 1.5" post to a 2" post and the stiffness goes up by the power of four. (eleven times)
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#3 chris fawcett

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Posted 03 March 2009 - 03:09 AM

Tammy,

The size of the gimbal is also an ergonomic question. Too big or too small for your hand is no good, but within the wide range most hands can 'handle,' size should relate the weight of the rig+camera, thus the pan inertia of the system. Light rigs have smaller gimbals, otherwise they would be too twitchy. Larger rigs need larger gimbals, otherwise you just couldn't get enough grip around them to control the rigs. A 2 inch gimbal is really big. I'd only consider it only if you have reasonably large hands, and work with heavy cameras.

Losing my grip,

Chris
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#4 JobScholtze

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Posted 03 March 2009 - 04:05 AM

Have to disagree with you on that one chris. I have a 2 inch and no big hands. I love the feel for it and it needs so little force to move around. My opinion is that it makes it more easy to move around more delicate.. When i started with 2 inch it was scary, after a few weeks i wouldnt change it back, period.


Its all personell i guess
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#5 Richard James Lewis

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Posted 03 March 2009 - 08:00 AM

Not forgetting that with the 2" gimbal, you have a larger pan bearing / bearings. Now this is not exclusively the case, as now other manufacturers do have larger bearings with gimbals that are still for 1.5 / 1.58 posts. But for those who don't, it means that you are more likely to have less friction as a larger bearing can cope better with increased weights. The fact that Job feels the gimbal takes less effort to use could be a factor of this has he moved from a Gold 1.5" Gimbal with a smaller bearing, and might not necessarily be totally down to the post diameter, but I'm not to second guess that.

Edited by Richard J Lewis, 03 March 2009 - 08:03 AM.

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#6 Jerry Holway

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Posted 03 March 2009 - 09:12 AM

The problem with a bigger diameter post and gimbal is that, as Job says in his praise of it, the sled moves more easily...

With a bigger diameter post, one has a bigger leverage, and our natural small movements will have a bigger (unwanted) influence on the rig. It's why we don't grab the rig far from the c.g. There's really no problem with a 2 inch post if the rig is heavy and spread out with lots of inertia, but smaller, lighter, and less inert rigs will show the disturbance.

At one extreme, the JR and Merlin have very small diameters and surfaces because they are so light and have so little inertia... a normal diameter/size surface and the thing wouldn't work at all...

For most situations, a 1.5 / 1.58 inch post is just fine (with a handle diameter about 1.85). Some folks will like the bigger diameter, some the smaller. It's an ergo thing as Chris points out, or an ego thing? or just something different that gets us to the next level.

Eric is right about the OD and stiffness, but OD is only one factor of many determining how stiff a rig is, and there's no real need, IMHO, to have a two inch post for stiffness.

What is critical in a gimbal is to have good bearings well centered, and there are plenty of low quality bearings and less than swift gimbal designs out there that will make your work suffer regardless of size. The pan bearings in the new Flyers, for instance (1" post?) is the same quality of bearing as is in the Ultra 2 but in a smaller size, and the feel is terrific.

Jerry
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#7 Alec Jarnagin SOC

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Posted 03 March 2009 - 11:36 AM

One thing about Steadicam that makes it so much fun yet so difficult on the manufactures is that we are a rather opinionated lot of people. I love my 2" post because it is insanely rigid. The rig just feels great too (I'm also a big fan of the XCS gimbal). I should add that the XCS 2" gimbal has a handgrip that is a mere 2.10" though since I think adding the usual .25" to .35" to the outer diameter would be a bit much. I think the place where rigidity is gained with the thicker post is when extended way out or using longer posts. The inner post on my XCS/PRO Hybrid is 1.75" which I think is a wonderful thing.

Jerry also points out that build quality is a large factor in stiffness and rigidity and he is absolutely right. A large part of operating with any diameter post is what you get used to.
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#8 Eric Fletcher S.O.C.

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Posted 03 March 2009 - 12:08 PM

For most situations, a 1.5 / 1.58 inch post is just fine (with a handle diameter about 1.85). Some folks will like the bigger diameter, some the smaller. It's an ergo thing as Chris points out, or an ego thing? or just something different that gets us to the next level.

Eric is right about the OD and stiffness, but OD is only one factor of many determining how stiff a rig is, and there's no real need, IMHO, to have a two inch post for stiffness.


Not going to agree with you Jerry, you can't beat physics. The stiffness of a tube is D^4 (Diameter to the 4th Power) using a 1.5" post as a baseline a 1.58" post is 1.23 times stiffer and a 2" post ELEVEN Times stiffer. Wall thickness BTW is what determines your strength. It has only a little impact on Stiffness.

The same can be said for a bearing, the larger the bearing the smoother it is and the stiffer it is.
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#9 Ed Moore

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Posted 03 March 2009 - 12:25 PM

Whilst we're still vaguely on topic, can someone explain to this idiot exactly what it means to 'center' a gimbal - and when would I know mine needs centering?
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#10 Erwin Landau

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Posted 03 March 2009 - 08:46 PM

Whilst we're still vaguely on topic, can someone explain to this idiot exactly what it means to 'center' a gimbal - and when would I know mine needs centering?



Ed: Balance your rig statically, rotated or tilting your rig 90 degrees. Nothing should happen, the rig should return to it's balanced neutral point. If your Gimbal is not up to snuff the rig will start to lean to wards one or the other side being off level. That means that the 3 axes are not intersecting at the same imaginary point inside the centerpost, which means that the Gimbal is not centered. But make sure that gimbal is clean before you do so or it will give you fouls results.


I don't think that the size of the center post has anything to do with ego. I think that goes more into the size of the car you drive and how much horsepower it has (BTW: Red VW Van with 201 bhp)...
Having used the 3A 1.5" with the Alu post as well as the one with the carbon fiber one and later owned a PRO with the DeRose center post and the early GPI center post it was outright a tragedy. On wip-pans were the base stopped a split second after the rest of the rig... annoying as hell. That prompted me to get a custom post made... Greg Bubb was so kind to provide me with the necessary resources and a lot of his time. Which ultimately lead to the purchase of a whole Ultimate...

Jerry you must admit that a 2" post gives you more stability then a 1.58" which was, according to several former CP employees including one which unfortunately no longer is with us, had more to do with starving Paddock and his PRO for Gimbals then increased stability, at least I have never seen an outrigger and stabilizing cable set up provided for an XCS, BearBel, or Betz sled in super post mode.

Going from my 1.5" PRO gimbal to the 2" XCS gimbal (6 years and 3 generation and counting) was for me quite an improvement. I felt that with the larger diameter bearing I had a better feel and control over the rig. As i used the over size grip (2.1") on the PRO before it was immediately familiar because the diameter is identical on the Ultimate gimbal AND it was tool-less which was new back then... for me at least. If you feel that something is not right there is no rational way to convince anybody otherwise... So you have to find the parts that make you feel comfortable so that you can concentrate on the shot and not think about the equipment.

Everyone his own. Mine works great for me and the sales numbers speak for itself.


Peace,

Erwin
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#11 Eric Fletcher S.O.C.

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Posted 04 March 2009 - 02:00 AM

I don't think that the size of the center post has anything to do with ego. I think that goes more into the size of the car you drive and how much horsepower it has (BTW: Red VW Van with 201 bhp)...



How big of a gimbal is a Grey AMG E55 with 630HP?

that quote made me laugh!
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#12 Matteo Quagliano

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Posted 04 March 2009 - 05:32 AM

I might go for 2" Baerbel post... What do you think on that sled?

Thanks
Matteo
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#13 Jerry Holway

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Posted 04 March 2009 - 09:17 AM

I really wanted to dig out some old engineering articles here, but qucik google "research" got me to one manufacturer who said that the modulus of elasticity(stiffness) formulas for carbon fiber tubes don't just work nicely; so they must do both real and FEA tests to determine how it all works out (which they declined to share on the website with examples).

Simply: materials matter, diameter matters a lot, wall thickness matters (a 2" diameter tube with a 1.5" ID is stiffer (and, as Eric rightly points out, much stronger) than one with a 1.85 ID), bearing type and quality matters.. it all adds up. Split metal tubes (as used in some early designs to keep the tubes registered (EFP?)), allow for a lot of twist.. not good with whip pan stresses, as Erwin points out.

What you need depends on what you do, what you are willing to pay, and like everything Steadicam, what you like and what compromises you are willing to work with or around. Or perhaps for you that feature isn't even a compromise, yet it might be for others...

So where some feel a 2 inch post is the cat's meow (as well articulated by many), I am of another opinion (also articulated, I hope). Tammy asked, what's the deal with a 2" post and she got some good answers.

The ego comment was a joke - BTW...

The spreaders and stays are only for extreme situations... never use mine, BTW... just nice to have.

Jerry
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#14 nealnorton

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Posted 04 March 2009 - 10:16 AM

I have used a few different post/gimbal sizes. The first was a steadicam model 1 with the skinny (3/4"?) post, then bought a steadicam model 2 still with the skinny post and pistol grip gimbal. Then the model 3 with the 1 1/2", then the 3a followed by a PRO sled, then a sled with a 2" gimbal and a heavy carbon fiber post.

I sold the 2" sled and bought a new PRO. The post is plenty stiff, really. I appreciate the very light rig and have no problem with vibration. I have not experienced a better gimbal.

The XCS sled is a wonderful product. . . I have tried it and liked it a lot. The post and gimbal are just beautiful. . . but I simply can't see any difference in the results because of the post diameter. There might be a good argument that the increase in strength and stiffness could help prevent a failure in the event of a crash or a dropped rig.
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#15 Alec Jarnagin SOC

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Posted 04 March 2009 - 11:41 AM

Neal,

"The XCS sled is a wonderful product. . . I have tried it and liked it a lot. The post and gimbal are just beautiful. . . but I simply can't see any difference in the results because of the post diameter. "

I should add that I made these modifications to my sled before the VZ gimbal (I wanted tooless) and before the newer version of the PRO center post (they still had a slit in the inner post at the time). I've heard only great things about the new 1.5" post from PRO.

From your description and praise about XCS, I'll assume you were using someone else's system that you sold.
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