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J-Bracket Flexing


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#1 thomas-english

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Posted 12 December 2009 - 06:20 PM

I use this J-Bracket out of convenience. I have a G70 arm with a 5/8th post (MK-V). I like it because I can simply slot it in in seconds without changing anything on my post and have my gimble really low. Unfortunately it does flex a little and on 35mm packages I dare not use it. Do your J brackets flex? If so is it a cause for concern?

I suspect I am being too ambitious with that distance and I need to get a 6 inch steadicam to 5/8th post, pop it in upside down and a ciniwidgets setup.

Any advice?

Thanks

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#2 Mike Germond SOC

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Posted 12 December 2009 - 07:35 PM

I can't answer your J-bracket question, because my arm does not require one. But I do have a 12" 5/8 post from Tiffen that scares the daylights out of me when I put a fully loaded rig on it. I have visions of it snapping and a sharp aluminum post with 20lbs+ of expensive weight stabbing me in the chest..

I have combined it with my D-bracket to get extra low (almost like a J-bracket). For some reason I feel more comfortable hanging a rig off of it than setting a rig on top of it..
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#3 thomas-english

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Posted 12 December 2009 - 10:28 PM

Yeah, I had an 18 inch post made up for me once. I even used it with a 435 and it really was not right. I have since heard from qualified sources that 12 inches is the most one should go. I wonder if anyone could confirm that. I think the advice was that it was not the post that would snap but the castings at the top of the arm that were structurally less secure with these torsions.

I have since binned the 18inch post.
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#4 Alec Jarnagin SOC

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Posted 13 December 2009 - 03:24 AM

"I can't answer your J-bracket question, because my arm does not require one. "

And which arm is this? No arm REQUIRES one; it is a mere option to adjust the camera position which comes in handy if you ask me.
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#5 Mike Germond SOC

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Posted 13 December 2009 - 10:18 AM

Flyer LE arm...I guess what I mean is one doesn't exist. My only choice of bracketry accessories was the D bracket (back when I purchased this stuff)
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#6 Brian Freesh

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Posted 13 December 2009 - 01:58 PM

Flyer LE arm...I guess what I mean is one doesn't exist. My only choice of bracketry accessories was the D bracket (back when I purchased this stuff)


Do you mean "F" Bracket?

If so, I agree the name doesn't fit.

how does your 12" post work with the Flyer? My understanding was that Tiffen didn't make any for the Flyer. And the 5/8" is the full diameter, that's really thin if so! But the arm post is only 1/2" yes? Or is it different on the LE?

Sorry Thomas, I hijacked...
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#7 Mike Germond SOC

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Posted 13 December 2009 - 03:37 PM

Yea that's the one. They call that an F-bracket? Odd..

It's a direct swap out for the stock post. It uses the same screw and everything. You're right in that it is 1/2", not 5/8", and it is the same diameter down the entire post. I may have gotten it by a fluke in Tiffen's system because they accidentally charged me only $35..
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#8 Brian Freesh

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Posted 13 December 2009 - 06:21 PM

Interesting. So it only extends, what, like 7 inches higher than the standard post? I still see the fear, but that's better than the full 12"!

Did you see the extensions I had made? They're in a thread here somewhere... But they're anodized now. Mark Schlicher also bought a set. Only time I've needed them so far was before I had them made, but they're quick and easy to change, and you can have them in multiple heights, instead of just the one.
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#9 Erwin Landau

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Posted 14 December 2009 - 04:27 AM

Thomas,

I use a J-Bracket on a regular basis. I use a 6 inch and a 8 inch, i used to use longer ones but they proven to be unpractical as the arm was always in the way were I wanted my operating hand to be...
I use them underslung, meaning I insert them from below and keep them in place with an arm post clamp. Try it it will greatly reduce the flexing as you have one point of attack versus 2 places to get bend...
But I admitting: the longer the arm post and with it the larger lever and he heavier the payload the bigger the chance of flexing... or if to heavy, permanent deformation of the arm post... if not also damage to the bearings in the D-Link of the arm.

I had several 20 inch arm posts or "man makers" that Bob Ulland had made to make up for what had nature given him or not in the vertical roam... not a size that I would be comfortable to use. The flexing scared the crap out of me.


Brian,

If you bought it from CP/Tiffen then it's an F-Bracket, If you bought it from PRO it's a D-Bracket... and if you add a second arm post to it, it's a J-Bracket either way.
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#10 Charles Papert

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Posted 14 December 2009 - 09:00 AM

I've used a 15 or 18" manmaker post (forgot which) for many years without incident to either the post or the arm (12 year old PRO arm, prior to that upgraded Model 1 arm, now 30 years old and still in service for Dave Isern). Yes, it flexes a little under full load, but then again so do I.
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#11 thomas-english

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Posted 14 December 2009 - 06:53 PM

Thanks guys, your advice as per usual is really most informative.

Are your man-makers solid or hollow I wonder?

On your advice and for the sake of my G70 arm that I love (in a weird way). I am going to undersling a J-Braket. I just need to find a collar to go onto the steadicam Master portion of my post since it is going to go in upside down. i.e. at the top of the attached picture.

In this document:

Steadicam_Access_Brchr_0307-1.pdf "The steadicam accessories brochure"

There is a Locking spinning collar for ultra/MS Arm post 250/7211, I wonder if this could be the one since everywhere else I search collars are designed for 5/8th posts. Anyone have any better suggestions for a safety/locking collar?

In a moment of stupidity I did notice that the 5/8th post is 16mm ish and the MS/Ultra part is 19mm. It would be perfect if I could just use a steel ARRI 19mm camera bar and a 19mm to 15mm dog bone (a strong one) at the bottom. Thus enabling me to use a 19mm dogbone at the top as a collar and as a handle of sorts. I did try shoving a 19mm bar down the gullet of my G70 but she weren't happy and did protest; demonstrating my sheepish ignorance. I will stick to plan A.

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#12 Jerry Holway

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Posted 14 December 2009 - 08:52 PM

Do you mean "F" Bracket?

If so, I agree the name doesn't fit.

how does your 12" post work with the Flyer? My understanding was that Tiffen didn't make any for the Flyer. And the 5/8" is the full diameter, that's really thin if so! But the arm post is o


FYI, the F bracket was named after the guy who thought it up, Francois Ambarchaud.... and that's what it was called first and publicly in the Steadicam Letter long ago. Now I'm curious, why is the PRO stage called a "Donkey Box?" Really - anybody know?

Jerry
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#13 Jerry Holway

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Posted 14 December 2009 - 09:00 PM

Also, FYI, the MS and G-70 arm posts have an OD of .740, not 19mm (.748).

One should also be careful with any long arm posts and heavy loads, as the torque on the arms will increase with the longer arm posts. Lightweight arms, like the Flyer arm, really should not be used with long arm posts and high loads.

Even if the arm and post can handle the loads, it's pretty uncomfortable reaching the upper limits with a post much longer than 12 inches...

2 more cents...

Jerry
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#14 Mark Schlicher

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Posted 14 December 2009 - 09:29 PM

I like my arm post extensions very much. Mentioned them to Jerry and Garrett at the Workshop last week and they made the same observation Jerry makes elsewhere in this thread: that the Flyer arm is not engineered to take the torque that a heavy camera on a long arm post could theoretically exert. So, use with caution. I only use them with my HVX200.

Interesting. So it only extends, what, like 7 inches higher than the standard post? I still see the fear, but that's better than the full 12"!

Did you see the extensions I had made? They're in a thread here somewhere... But they're anodized now. Mark Schlicher also bought a set. Only time I've needed them so far was before I had them made, but they're quick and easy to change, and you can have them in multiple heights, instead of just the one.


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#15 Erwin Landau

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Posted 14 December 2009 - 09:53 PM

Now I'm curious, why is the PRO stage called a "Donkey Box?" Really - anybody know?

Jerry


I never got Chris Haarhoff to tell the whole story... just something with Mexico... a lot of booz... and some kind of donkey show... but I could be mistaken... sounds very much like the 1980ies workshop where they came up with missionary...
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