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Dolly Accident...Caught on Video!


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#1 Karl Lee

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Posted 01 November 2014 - 12:50 AM

This video may have already made the rounds, but in case anyone missed it...

 

<Click here to view the Facebook video.>

 

Yikes!  So ultimately, what was the culprit here?  Was it simply the rising center of gravity?  Also, out of curiosity, is that an Elemack dolly rig?


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#2 Alessandro Machi

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Posted 01 November 2014 - 01:27 AM

wow, that is dramatic! Might the problem have been that the grip at the very back of the dolly could not stay back far enough  on the swing around because of the subway tracks? The farther back he can stay the more counter weight he provides. So at the beginning of the shot he has all the counter weight room he needs, but as the dolly moves on the track and he swings around, he can only go back a limited amount so he has less counter weight to offer.

 

That is one complicated math problem to figure out on the set. Was that a rehearsal or an actual take? I am curious if there are prior takes to what we are seeing. If there are prior takes and the dolly did not fall over, than that might mean the tolerance on the back end was so tight that simply anticipating the move of the dolly just a moment too soon versus being a counter weight a moment longer was all it took to cause the dolly to tip over.

 

Plus I noticed the track was elevated with wedges and that could have had an affect as well on a swing around.


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#3 Jeff Wolfram

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Posted 01 November 2014 - 08:33 AM

I see two triangles, first;  camera to grip to point on floor at tracks. The second triangle; camera to point on floor at tracks and then straight up to top of the crane (perpendicular to the floor's point).  I believe (imho) that the math of the second triangle is to blame for the fall.  As the distance between camera and the point on the arm of the crane expands out the force between the line from camera to track's point increases.  I believe the solution would be more weight at the base of the crane to justify the extension of the crane's arm(with weight of camera operator)

 

While it's true extending out the grip might help, his position is more of a fluid up and down of the arm not stability of a crane.

 

I also agree that even an empty test run might (should) shown this instability where grips(human strength) might of caught the weight instability before catastrophic failure. 


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#4 Jeff Wolfram

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Posted 01 November 2014 - 08:43 AM

p.s.  the math should always be done on the most extended out point of the move and that's why I see this as a two-demension problem not accounting for the swing. the beginning is just in a more stable position and I don't believe momentum had any factor in this example.


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#5 Phil Rhodes

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Posted 01 November 2014 - 10:21 AM

Can't see it. Not on facebook.

 

(Face ridiculous)


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#6 Richard Boddington

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Posted 01 November 2014 - 12:02 PM

Clearly not enough weight in the back, as I was watching it I thought, hmmmm, not many weights on the back of that thing.  When I've seen that type of crane used there are typically a lot more weights. As the crane extends out and the load gets further from the centre, physics takes over, and the rig goes over.

 

I always make it a policy to personally inspect any rig that will go over the top of an actor.  If a camera fell off the crane and landed on the actor, well I can't image what devastation that would cause.  So once the rigging is done, I'll ask the ACs to walk me through the entire set up.  I want to see the safety chain going from the camera direct to the crane structure.  There's no such thing as being too careful in these cases.

 

R,


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#7 Alessandro Machi

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Posted 01 November 2014 - 05:28 PM

p.s.  the math should always be done on the most extended out point of the move and that's why I see this as a two-demension problem not accounting for the swing. the beginning is just in a more stable position and I don't believe momentum had any factor in this example.

 

That's what is so tricky about this. If full extension happens before the grip can be completely behind the rig, then the counter force provided by the grip is much less. But then this brings up another question, what percentage of counterweight is the grip at the back responsible for versus using more counterweights as Richard Boddington suggested. Are there actual standards?


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#8 Bill DiPietra

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Posted 01 November 2014 - 06:15 PM

Even if there had been enough weight in the rear, the grip in the back could have easily tripped on the dolly track. 

 

Very poor set-up as far as safety goes.


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#9 Chris Millar

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Posted 01 November 2014 - 07:29 PM

Does any one have a link or name of that rig (or one just like it if it is generic enough) - I'd like to find a clearer image of it so I can get my head around it's dynamics...

 

Of course any resultant discussion is all academic, but yeah - still interested :)


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#10 Bruce Greene

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Posted 01 November 2014 - 07:44 PM

I have used this rig when filmming in Russia. It's a Panther / Magnum dolly.

The dolly grip has always said no rotation while on tracks. The wheel base is not wide enough, as you can see in the video...
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#11 David Mullen ASC

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Posted 01 November 2014 - 07:54 PM

One could put some sort of low outriggers with weights at the base to give it more stability.


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#12 Chris Millar

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Posted 01 November 2014 - 09:24 PM

Although it's a little bit armchair CSI...

 

The unit is obviously heavy on the operator end of the arm, that combined with:

 

- the rotation of the unit had just aligned the arm with the direction of motion

- the continual rise of the centre column

- a bit of dodgy track, maybe a joint or wedge fail - (the 'pop' at 28 secs... - within 1 sec the unit stops on the tracks and over it goes ?)

 

Did someone mention motion control - or at least operator on remote wheels and focus?

 

And as David mentions, lower it's CoM - and/or extend it's natural pivots (the dimension of the base) - >edit:as Bruce suggests


Edited by Chris Millar, 01 November 2014 - 09:24 PM.

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#13 Gregg MacPherson

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Posted 01 November 2014 - 10:10 PM

That was a needless accident.  Due to overconfidence.

The crane providor should give data tables for the hard ballast needed for any load (operator and camera kit) to be safe at any position.  The fulcrum or pivot point will be the centre of the dolly wheel unit nearest the camera.

If the grip hates reading or is really bad at high school math he can do a dry run using a stand in mass for the camera and operator loads.


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#14 Richard Boddington

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Posted 01 November 2014 - 10:23 PM

I haven't seen one of these things used in Toronto in a long time now, everyone uses remote heads, no need to have a human operator out on a crane.

 

R,


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#15 Bill DiPietra

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Posted 01 November 2014 - 10:26 PM

I haven't seen one of these things used in Toronto in a long time now, everyone uses remote heads, no need to have a human operator out on a crane.

 

R,

 

Interesting point.  I never thought about remote heads from a safety standpoint until now.


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#16 Chris Millar

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Posted 01 November 2014 - 11:43 PM

The fulcrum or pivot point will be the centre of the dolly wheel unit nearest the camera

Neat! another physics discussion :)

 

I would say that if the wheel locks up the pivot point actually runs along the circumference of the wheel.

 

If the wheel is free to turn then again it's a moving target, close to the wheel axle as you point out, but not perfectly centre (conservation of momentum, friction etc...)


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#17 Gregg MacPherson

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Posted 02 November 2014 - 12:59 AM

Neat! another physics discussion :)

 

 

Putting the fulcrum anywhere within the truck for that wheel unit would have worked.  (cat screaming while it goes to the bathroom face)


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#18 Phil Rhodes

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Posted 02 November 2014 - 07:23 AM

I'd love to see the movie, but... facebook. Is it anywhere else?


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#19 John Salim

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Posted 02 November 2014 - 09:07 AM

I'd love to see the movie, but... facebook. Is it anywhere else?

 

I'm using a raher slow Windows XP pc ( with IE ) Phil, and have to wait a while for the video to load ( ... I even get a  'do you want to run this script'  prompt - click yes ) and it eventually plays.

 

I'm not on facebook and it's openly accessable.

 

John S ^_^


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#20 Phil Rhodes

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Posted 02 November 2014 - 09:20 AM

Oh, I see. Ouch.


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