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C-stand sandbag and arm placement questions

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kat hayes
C-stand sandbag and arm placement questions
on Jul 24, 2015 at 7:36:47 pm
Last Edited By kat hayes on Jul 24, 2015 at 7:38:30 pm

I want to make sure that my C-stands are stable, and I keep seeing conflicting info regarding sandbag placement and arm/knob location. I currently positioned the arms and bags based on what seemed stable. Can someone please look at my photos and give me feedback? Thanks!







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Todd Terry
Re: C-stand sandbag and arm placement questions
on Jul 24, 2015 at 7:40:37 pm

Hi Kat...

You look like you are doing it right...

You want to put the tall/high leg on the OPPOSITE side of the weight on the stand (i.e., if the arm/weight is pointing NORTH you'd want the tall leg pointing SOUTH). And you'd put the sandbag on that tallest SOUTH leg, facing away from the weight.

And you have at least one extra bag on yours, which isn't a bad idea if you have a lot of weight.

From what I can tell from your pic, looks like you've got it.

I have no idea what that spare part that fell out goes to though, it's nothing I immediately recognize.

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com



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Rick Wise
Re: C-stand sandbag and arm placement questions
on Jul 24, 2015 at 8:34:54 pm
Last Edited By Rick Wise on Jul 24, 2015 at 8:38:12 pm

Oh dear, it looks like for once I have to disagree with Todd! The high leg should be UNDER the weight bearing arm, not across from it. Of course, with enough sand bags, any arrangement will work. But run this simple experiment: run the arm out to the right. Place the high leg directly under it without any sand bag. Press down on the arm. It is extremely hard to tip the C-stand over this way. Now do the same thing, but this time with the leg on the opposite side of the arm. Now it's pretty easy to tip the c-stand over.

As for where the knuckle should be: If you are facing the knuckle, the weight should be out to your right. If you are standing behind the C-stand, the knuckle should be on the right side with the arm carrying any weight going straight out away from you. In the photo at the start of this thread, the weight is going out to the left of the knuckle when you stand in front of it. The reason the weight should be to the right is that if your are flying something heavy out on that arm, when the weight is to the right the knuckle tightens its grip as it starts to sag. Placed to the left, the knuckle loosens its grip. In the photo, the weight is miniscule so you could go either way. However, it's really good practice to ALWAYS place any weight to the right. Making that a habit will some day save your butt.

Rick Wise
Cinematographer
MFA/BFA Lighting and Camera Instructor Academy of Art University
San Francisco Bay Area
http://www.RickWiseDP.com


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Todd Terry
Re: C-stand sandbag and arm placement questions
on Jul 24, 2015 at 8:57:44 pm

Oh my... I have to RE-disagree with Rick. I think of the sandbag as a counterweight, ergo it is on the opposite side of the fulcrum (which would be the center of the turtle base). But no matter, if you pile enough weight on it either side will work.

BUT... do make sure you are using the tall leg for the sandbag. The bag is not doing all it can if part of it is resting on the floor.

And Rick is dead-on of course about the knuckle position. I was actually chiming in to explain why it's that way, but looks like Rick has updated his post and done a nice job of that. Just remember that the weight should tighten the knuckle, not loosen it. "Righty-tighty, lefty-loosy."

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com



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Rick Wise
Re: C-stand sandbag and arm placement questions
on Jul 24, 2015 at 9:16:55 pm
Last Edited By Rick Wise on Jul 24, 2015 at 11:48:26 pm

Todd, do the test I described and get back to us.... I know I resisted this idea too until I tried it out. At first it seems counter-intuitive. It may help to think of it this way: imagine a vertical pole. On the bottom there is a flat piece of metal that extends for six inches or so and is solidly screwed into the base of that pole. Hold the pole vertical. Push the pole toward the metal plate. The pole doesn't budge. Push it away from the plate, the pole goes over very easily. You can pile all the bags you want on that plate, but it will never be as solid at holding the pole upright if you are pushing away from the plate as it is when you push toward the plate..

The other two legs of a C-stand splay out. They do provide some resistance to topple, so they help a lot, but the laws of physics make it pretty clear: for the most stable resistance to topple, the weight on the C-stand goes over the highest leg sticking straight out under the load-bearing arm. (For a diagram, see p. 81, Set Lighting Technician's Handbook, 4th edition, by Harry C. Box, the grip and electrician's bible.)

Rick Wise
Cinematographer
MFA/BFA Lighting and Camera Instructor Academy of Art University
San Francisco Bay Area
http://www.RickWiseDP.com


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Todd Terry
Re: C-stand sandbag and arm placement questions
on Jul 24, 2015 at 9:19:27 pm

I refuse to believe this... Rick, you've only been doing this 40 years longer than me, what can you possibly know???

:)

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com



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Craig Alan
Re: C-stand sandbag and arm placement questions
on Aug 1, 2015 at 1:36:59 am

A stand will tip over in the direction between two legs (to one side of the load) not tip toward the point of a single leg. Two sand bags draped over two legs will secure any small load. Since the three legs are not an extension of each other but at 120 degree angles, no one leg will actually be a direct counter weight except if you place a bag on the gobo arm extended on the opposite side of the stand/load.

The longer taller leg would be the most difficult to tip forward but tipping happens at the point of
least resistance. The slight advantage of the longer leg is that it creates a foot more directly under the load but not by a whole lot. And the two other legs are lower and have a lower center of gravity when you place sand bags on them.

I just grab the stand and push and pull to see if it wants to tip. If it seems iffy, throw on another bag.

Are there saddle bags designed specifically for the legs of c-stands and/or baby jrs.? Mine tend to drag on the floor.

Mac Pro, macbook pro, Imacs (i7); Canon 5D Mark III/70D, Panasonic AG-HPX170/AG-HPX250P, Canon HV40, Sony Z7U/VX2000/PD170; FCP 6 certified; FCP X write professionally for a variety of media; teach video production in L.A.


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Erik Anschicks
Re: C-stand sandbag and arm placement questions
on Jul 25, 2015 at 7:04:57 pm
Last Edited By Erik Anschicks on Jul 25, 2015 at 7:13:34 pm

I agree with Rick and Todd about the knuckle placement. You always want the arm that is extending out to be going in the same direction that the knuckle tightens in. As Rick said, stand BEHIND the stand with the arm extended in front of and away from you and the handle for the knuckle should always be on your right. This way, the downward force of the object applies pressure to the knuckle, causing it to tighten more.

The second picture where you show the foamcore shows the INCORRECT position, as both knuckle handles are to the left from where you're standing and taking the photo. Try pulling down on the arm in that configuration and you'll see that the knuckle will loosen as you do, since you're working against gravity. In the opposite (correct) configuration, the arm would tighten the knuckle.

As for the leg placement, you do indeed always want the highest/largest leg under the arm or light because that leg can absorb the most pressure. Tipping it over in that direction will be the most difficult. Place a sandbag on that highest leg, and certainly add another if you're using more weight. Speaking of which...

BIG SAFETY TIP: When arming out something lightweight, like the foamcore in the photo or a flag/net, you can indeed use a (sandbagged) C-stand. However, when using something heavier, like a small light rigged onto a boom arm and extended, use a Combo/Jr. stand and NOT a C-stand. A combo stand is much more robust with a wider leg base and therefore has more stability than a C-stand. Really anytime a boom arm or something larger than a C-stand arm is used, it should be on a combo and probably have a sandbag on the opposite side as a counterweight in addition to bagging the stand itself. I see pictures or examples of people arming out FAR too much weight on C-stands all the time and it is a serious safety hazard. I understand that combos are heavier and less easy to travel light with, but I believe they, and the appropriate amount of sandbags for them, are necessary anytime flying things around the set comes into play.


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Rick Wise
Re: C-stand sandbag and arm placement questions
on Jul 25, 2015 at 7:44:21 pm

Good safety tip, Eric. To fly a 300W and maybe a 650 Fresnel out on a C-stand arm will be OK, though I think it's best to also hang a sandbag off the back end of the arm as counter-weight. Anything heavy enough to make the arm bow more than a tiny bit is too heavy. Then it's time for much larger and more sturdy support systems, as you described.

Rick Wise
Cinematographer
MFA/BFA Lighting and Camera Instructor Academy of Art University
San Francisco Bay Area
http://www.RickWiseDP.com


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Erik Anschicks
Re: C-stand sandbag and arm placement questions
on Jul 25, 2015 at 8:35:42 pm
Last Edited By Erik Anschicks on Jul 25, 2015 at 8:40:13 pm

Thanks Rick, and I agree with you about small units on C-stand arms, I should have been a bit more specific.

The extension length is the main factor, since that's where the weight starts to add up quickly. I'd say anything relatively lightweight that you need to arm out further than what a regular 40" arm would provide (and not start to bow the arm, as you said) is where I'd start to use a combo stand. I've put tweenies and smaller units on the end of a C-stand arm if I just needed a little extension, and appropriately bagged, it's been just fine. I wouldn't go further than that though in terms of weight and yes, always hang a sandbag on the opposite side as a counterweight. When I start to need a real boom arm though, I'd ALWAYS put that on a combo.

I should add that all of these scenarios are for indoor use. For outdoor use with wind and weather issues, I wouldn't trust flying hardly anything for any extended period of time without a combo stand, especially here in Chicago!


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Joseph W. Bourke
Re: C-stand sandbag and arm placement questions
on Sep 18, 2015 at 4:01:20 pm

Here's a good, short tutorial on C-Stands:

https://vimeo.com/blog/post/all-about-c-stands

Joe Bourke
Owner/Creative Director
Bourke Media
http://www.bourkemedia.com


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