Achieving Dynamic Balance (Glidecam V16 w/ XL1S

[Levi A. Taylor]

This is my first post on this site and I’m excited to get feedback. I have been following threads for a longtime and have always been impressed with what I have learned.

I have recently purchased a Glidecam V16 stabilizer (kit 3). I did a lot of research on the rig (largely on this website), so I had a pretty good idea of what I was getting myself into. I knew I wouldn’t be able to just strap on the vest and start flying smooth and easy. I knew that it would be a strain on my back for a while. I was prepaired to spend lots of time working with this unit to perfect the art of stabilized shooting.

What I wasn’t prepared for was the frustration of achieving dynamic balance. I have spent several days trying to get the rig balanced, and have only achieved getting myself frustrated. I am using a Canon XL1s, which I know is a bit light for the unit, but I have read about several people using this camera with this rig, so I wasn’t expecting it to be a problem. I have access to a JVC DV5000, that’s why I bought the V16 instead of the V8, but I planned on practicing with my own XL1S.

I could go into extensive detail about what I have done so far during the balancing procedure. But before I do, I would love to see, or hear about, another V16 operator's set up with a XL1s.

Can anybody who has successfully flown the Glidecam V16 with a Canon XL1s give me any pointers. A list and/or pic of their setup would be so appreciated!

I was so excited about receiving the unit. Now, if I could only use it…

[Charles Papert]

Levi, perhaps you mean static balance? It's entirely possible to fly a rig that is properly statically balanced but out of whack dynamically (dynamic balance was a concept that wasn't "invented"/grasped until the third production model of the Steadicam came along--"The Shining" was shot with a tragically out-of-dynamic-balance rig, and that came out pretty wonderfully!)

I'd be happy to give you my thoughts but I can't speak specifically to the V16 setup with your camera. If you just describe what's going wrong, maybe I can give you a simple fix.

[Charles King]

[QUOTE=Charles Papert;660388]came along--"The Shining" was shot with a tragically out-of-dynamic-balance rig, and that came out pretty wonderfully!)
QUOTE]


...and that could be, because the man behind the camera was none other than the God father of the Steadicam, Mr Garrett Brown. ;) HA HA. You left yourself open there CP. HA Hope you are well.

[Ben Winter]

Can someone shoot me a link/explanation of what static/dynamic balance is?

[Levi A. Taylor]

Hey Charles,
Thanks for responding so quickly. I have to tell you how much I respect a professional at your level being so involved and dedicated to helping guys like me who are just starting out. It shows a great deal of character, and demands a lot of respect.

Ok, I have experimented with so many different setups that my head spins just thinking about where to start. The common result of all my approaches is this:

I can achieve horizontal balance pretty easily. I use a very tiny level to assure that the sled isn’t leaning at all one way or another. Since the XL1s is so front heavy (due to it’s small body and massive lens) I place most of the weights I use on the back bottom of the sled, and keep the front bottom of the sled equipped with the light weight L7-Pro LCD monitor, and two of the monitor’s small batteries. Anyway I can achieve horizontal balance with this configuration pretty quickly.

Moving on to the vertical balance is where I run into problems. First of all, when I extend the sleds central post to find it’s center of balance, it always places the camera too high. As is I’m a pretty tall guy (6’5’’), combined with the camera’s high level after adjusting the vertical balance, I’m left with an awkwardly high angle for most tracking shots. Anyway, that’s frustrating, but a different problem probably all together.

Once I’ve found the central balance of the sled’s post, holding the sled vertically with the lens facing the ground, the sled tries to roll over when I let go (so the lens faces the ceiling. That makes me think I have too much weight on the back of the sled. However, if I distribute some of my weights from the back bottom of the sled to the front with the monitor, my horizontal balance is totally off, leaving the camera leaning forward.

After offsetting the central posts center of gravity, so the sled naturally pulls back down towards the floor, I’ll perform the “Sled Arc Test”. Letting go of the sled from a vertical position, the bottom of the sled takes roughly two seconds to fall level to the floor (which I’ve read is good). However, the sled still tends to roll (turn) to the left or right as it falls. Not lean left or right mind you (I fine tune the horizontal balance a second time before performing the test) but pan left or right.

After all this, when I hook the sled to the vest and begin to move there is definitely more sway than there should be. The camera doesn’t seem to float the way it should when it meets momentum. I know I should probably expect a little of this. But it just feels like way too much. I’m fighting it from swaying left and right, up and down, more then I should. I’m not ready to give up by any means. I’m just stumped. I’ve always read that you’ll just suddenly feel it when it’s balanced correctly. And I certainly don’t feel it. But I don’t know what to do differently.

Again, any advice is always appreciated and revered at the highest level. Thanks.

[Charles Papert]

Here's everything you might want to know about dynamic balance (includes explanation of static, which is much easier):

http://www.steadicam-ops.com/docs/dynamicPrimer.pdf

You can skip over the mathematical section as it gets pretty heady--the practical section will answer any questions.

[Charles Papert]

Levi:

You mention extending the center post when vertically balancing--if I'm not mistaken, the V16 has a moveable gimbal, yes? So since you have an issue with the XL1 flying so high (being a lighter camera for that rig), you should be keeping the center post collapsed (short) as much as possible, and doing the balance tuning with the gimbal position.

When you describe the issue of moving weight from the back of the sled forward and the horizontal balance going off, can you not adjusting the camera's position by sliding it back on the platform? This is how dynamic balance is achieved--a repositioning of the weight from front to back both at the base and top of the sled.

Easiest way to find this without having to do a lot of trial and error is to find the CG of your camera by balancing it on a fulcrum (like a rod/dowel). The camera should be mounted on the sled so that the CG is slightly behind the center of the post, perhaps by 1/2". This is assuming that your rig has a raised monitor that is higher than the counterweights at the back of the rig--according to the pix on the GC site this is the case. Then position the weights on the bottom until a static balance is achieved.

I don't know if your docking bracket allows you to spin balance, but this is the easiest way to dial in dynamic balance--it maybe be possible when bodymounting, if the monitor doesn't hit the arm. The rig needs to be able to pan continuously, so remove any cables that would prevent this.

Give it a nice clean pan, not too fast or slow and watch how the rig behaves as it goes around. The desired effect is a flat spin, where the camera does not dip in any direction. Chances are you will be seeing a wonky spin! You need to observe a precession (dip) in the same place on the rotation each time it goes around; if it is acting erratically you may have given it a bad spin. Once you have observed a repeatable action, such as the camera is dipping towards the nose for instance, then do the following: move the camera incrementally in the direction that it is falling during the spin balance, and then adjust your lower weights to compensate. Try the spin again. If it is better but not perfect, make another adjustment in the same direction (or obviously, if it got worse, adjust in the reverse direction).

Good luck!

[Allen Plowman]

Charles, I am new to using a glidecam, I have been following your instructions here.
I just wanted to say thanks, Mine now spins flat. :)

[Charles Papert]

Great! glad to hear it Allen. Have fun with your rig, it should feel better now.