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Old January 24th, 2004, 10:03 PM   #1
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What is a gimbal?

I have seen these in pictures and heard about them, but really, what are they?
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Old January 24th, 2004, 10:23 PM   #2
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Know the two rings that hold a ship's compass and allow it to stay level while the box or binnacle in which it sets tilts?

http://www.mathworks.com/access/help...h/gimbal.shtml

Was turned up with a very simple Google search. Just type in Gimbal and this URL was listed on the first page.
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Old January 25th, 2004, 04:09 AM   #3
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Jonathan, A gimbal is simply(not to be taken too literally), a bearing system that allows the sled to rotate freely in all three of it's axis. It is made up of bearings which control the pan, tilt and roll of the sled. It is simply a part of the steadicam system that helps control the sled with it's mounted camera in time and space and at the same time helps in preventing outside forces from acting upon the sled.

To be exact, it uses inertia to resist rotation whenever a force imminates through the steadicam Arm. It is also responsible for placing the sled at it's center of gravity or CG, or usually just below it. It is also one of the most important part in the steadicam system. Next comes the arm.

Charles P. probably have something else to add. Maybe he might just correct me if I missed or got something wrong :)
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Old January 25th, 2004, 02:53 PM   #4
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You got it, Charles.
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Old January 25th, 2004, 05:38 PM   #5
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I know what you are saying but you are contributing effects to the gimbal in which it can play no part.

A gimbal has only two degrees ( X & Y tilt ) of motion freedom. If it's outer ring is held steadily horizontal, it resists motion in the Z-axis. Z-Axis motion in allowed by the user's arm or the spring-loaded arm that is hung on the vest.

The gimbal doesn't resist anything except vertical motion in this application. It is really just a 2-axis bearing setup that allows the inner ring to tilt in both axis simultaneously. In fact, resistance is the last thing one wants from a gimbal in the two allowed degrees of freedom.

Inertia is the element that creates the resistance.

The responsibility for CG is in placement of the weights. Through application of those weights after proper placement of the camera, CG is established at or very near the gimbal.

I know, I know, I'm being anal about this. :-))
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Old January 26th, 2004, 12:29 AM   #6
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It's a bit confusing because we didn't actually define if we were discussing gimbals in general or those used on a Steadicam in general.

If one were to consider a true three axis gimbal, with the axes representing pan, tilt and roll, it would incorporate a series of concentric rings with the inner controlling pan by means of a circular bearing, and the outer two affecting tilt and roll with pivots at 90 degrees to each other. This was the original Steadicam gimbal design, but it was quickly realized that the limited degree of movement afforded by this design would handicap the operator too much in the tilt axis. Thus this pivot was moved back to the handle attached to the gimbal, allowing 360 degree rotation vs the 45 degree planetary ring design.

If I understand how you are defining "z" axis, Mike, perhaps we can agree that there are three angular axes: pan, tilt and roll (X,Y, Z) and three spatial axes, fore and aft, side to side and up and down (also X, Y and Z). Gimbals only act on angular axes. Yes?

Otherwise, you are correct about inertia and resistance. We could reword Charles K's comments to "gimbal-based stabilizer" and they might be more accurate. Yes again?
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Old January 26th, 2004, 12:46 AM   #7
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Yes and yes.

I've only machined a modification for a Glidecam for a DP and other than examining a Steadycam at NAB, I've not had one in my hands. Superficially they look similar but the Glidecam that I worked on was crudely manufactured in areas although the gimbal was OK. I seem to remember that the Steadycam looked a bit more tidy.
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Old January 26th, 2004, 01:36 AM   #8
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I guess I could hav gone into the real technical clarification but as Charles P. stated. I was relating a gimbal to a steadicam based device. sorry :/
I imagine that what he wanted to know.
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Old January 26th, 2004, 02:43 AM   #9
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If you have to ask: you've never seen anything
like it -- atleast the SteadiCam version. Wouldn't
want to try to build one at home.
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Old January 26th, 2004, 10:23 AM   #10
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Charles,

There is no 'sorry' here in any way. The functional part of the post was much better than my first post about the compass.

Building one isn't really difficult if you have the tools. Making the results work correctly takes experience both for the builder and the user, I'd guess.
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Old January 26th, 2004, 02:20 PM   #11
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Haha, well, I now know more than I ever need to about a gimbal. Thanks guys :)

I realized that i was confusing a gimbal with a hi-hat. what is a hi-hat?
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Old January 26th, 2004, 03:23 PM   #12
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AFAIK, a High Hat is the equivalent of a very low tripod. It is a base shaped sort of like a High Hat in the top of which is an appropriate receptical for a tripod head. Usually it is a concave hemisphere for accepting a head with a matching convex hemisphere on the bottom.
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Old January 27th, 2004, 02:55 PM   #13
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Aren't those huge machines on which partial sets are put (or
things like boats) which can then be rocked around also called
gimbals?
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