Spreader plates

[BillConnerFASTC]

In process of inspecting 20+ year old rigging. There were spreader plates for one every 5' basically, not unusual for the time but deficient based on today's standards and "best practice" of one every 2'. Easy enough to add on most sets but the shell sets are in the 4000-5000 pound range, and of course weights never removed. Since the spreader plates generally are to keep the weights on the arbor in the case of a runaway, does it matter on a lineset where the weight never changes? Is it really worth deading off the load, and unloading and reloading thousands of pounds of weights?

 

[RonHebbard]

In process of inspecting 20+ year old rigging. There were spreader plates for one every 5' basically, not unusual for the time but deficient based on today's standards and "best practice" of one every 2'. Easy enough to add on most sets but the shell sets are in the 4000-5000 pound range, and of course weights never removed. Since the spreader plates generally are to keep the weights on the arbor in the case of a runaway, does it matter on a lineset where the weight never changes? Is it really worth deading off the load, and unloading and reloading thousands of pounds of weights?

No.
Toodleoo!
Ron Hebbard.

 

[venuetech]

Worth a note, but no need to put it on a punch list.

 

[BillConnerFASTC]

I noted and discussed it but now do I recommend they include it in a contract for various corrective issues.

 

[egilson1]

I disagree. It is worth it. The issue your not considering is a catastrophic failure where the load on the batten no longer equals the load on the arbor, such as a lift line failulre which leads to the other lift lines becoming overloaded and failing. There are numberless examples we could create as potential examples, but the point being is that the spreader plates are there to keep the arbor rods from being able to spread, and there is a reason the ansi standard requires them on all arbors regardless if the load is ever changed or not. In addition, to recommend that the owner go against the manufacturers guidelines as well as the ansi standard is also somting to consider.

Ethan

 

[BillConnerFASTC]

Spontaneous lift line failure. 7 - 3/8" gac holding 4000 pounds. Seems somewhat implausible. But I will consider it.

 

[BillConnerFASTC]

You and others convinced me. I'm going to tell them they have to pay to have this done. I don't believe it would ever make a difference, and that the money could buy more safety in other places, but so be it.

I don't know how you would ever have a run-away on these fixed loads, and even if you did and the arbor crashed, the rigging pit is really deep (think top of arbor around stage floor level) and enclosed by poured concrete walls. And someone will have to move the the partially loaded arbor quite a bit - like from loading bridge to fly gallery - to reach all the arbor and do the work. And the shell is a single, monolithic custom piece - so it can't be readily disassembled. So putting it onto the low bid contractor since I don't think it wise for the users to do it.

 

[sk8rsdad]

N.B. this stupid idea is not to be taken as rigging advice.

I wonder if there are alternatives to spreader plates that don't require unloading the arbor to install; for instance, metal banding? Seems to me if the arbors are never going to be unloaded it ought to be possible to weld or bolt something that would keep them in the arbor and keep the arbor from deforming.

 

[MNicolai]

Marcus Center in Milwaukee had their shell ceiling fall out of the fly loft a few years ago so that failure method isn't unprecedented. Of course, theirs weighed 27,000lbs.

Probably something to be said though that if your orchestra gets flattened like a pancake it doesn't much matter at that point whether the arbor spills its weight.

 

[BillConnerFASTC]

The problem with welding is protecting the other rigging. I did also think about banding - but more like building a box arbor around the weights - and suspect by the time it was designed and built you would have send more than the labor and chain motors and probably span sets to control the load and install spreaders.

 

[BillConnerFASTC]

Marcus Center in Milwaukee had their shell ceiling fall out of the fly loft a few years ago so that failure method isn't unprecedented. Of course, theirs weighed 27,000lbs.

Probably something to be said though that if your orchestra gets flattened like a pancake it doesn't much matter at that point whether the arbor spills its weight.

But that was a very different design and not one where it was balanced at all. A shell hinged off the back wall and all motorized - no counterweight IIRC - is asking for problems.

 

[RonHebbard]

Marcus Center in Milwaukee had their shell ceiling fall out of the fly loft a few years ago so that failure method isn't unprecedented. Of course, theirs weighed 27,000lbs.

Probably something to be said though that if your orchestra gets flattened like a pancake it doesn't much matter at that point whether the arbor spills its weight.

@MNicolai How did this occur, what failed??
Toodleoo!
Ron Hebbard.

 

[gafftapegreenia]

I would do it if you are already working on the shell. Do any components need to be replaced? Lift lines? Blocks?

 

[BillConnerFASTC]

Gafftapegrenia - Not otherwise touching shell rigging beyond removing middle guide from arbor.

Ron - I think a gear box of shaft (key) issue. Not sure. I will search my laptop and see if I can find a reference. I had, around 1995, been consultant for renovation of Popejoy at UNM in Albuquerque, and we removed a very similar shell - ceiling hinged to rear wall and the motorized rigging.

 

[Colin]

Add to the causes of runaways here the possibility that someone will decide that the "fixed load" set is the perfect place to hang a piece of scenery or a big star drop or something else sufficiently heavy to run. The shell load may be permanent but that doesn't keep people from trying to add to it. In a multi-use space at least, shell pieces take up a ton of prime real estate. In my own space the upstage shell line set is the only option for masking a far upstage electric. There's enough capacity left in the set, so I bought an extra tall border for the purpose. I don't plan on inviting it to run away but it ought to be enough to at least do a... swift creep... if muscled up unbalanced.

 

[BillConnerFASTC]

Add to the causes of runaways here the possibility that someone will decide that the "fixed load" set is the perfect place to hang a piece of scenery or a big star drop or something else sufficiently heavy to run. The shell load may be permanent but that doesn't keep people from trying to add to it. In a multi-use space at least, shell pieces take up a ton of prime real estate. In my own space the upstage shell line set is the only option for masking a far upstage electric. There's enough capacity left in the set, so I bought an extra tall border for the purpose. I don't plan on inviting it to run away but it ought to be enough to at least do a... swift creep... if muscled up unbalanced.

Good point. In this case, it's unlikely to creep, which is why the plan is to add motorized counterweight assist. So if they had that - which adds plus or minus 750 or 1000 pounds of holding power, still think they're needed? Hasn't the possibility of a runaway been greatly diminished?

We play odds every day. Medical treatments - weigh the consequences of one against another and make the best bet. If rigging were unacceptably unsafe, we wouldn't allow it, and it certainly is never without some hazard, so we accept the odds. Life is a gamble. And then there is the issue of budget. Resources are finite and how to alot them is - a wager. Do I make this stage safer by motorizing electrics or a hundred other things?

I am recommending they add the spreaders and trying to give an estimate. I know the spreader cost but not the labor and other expenses. And I worry that in the process of doing this - when things must necessarily be very unbalanced - something goes sideways. Is that risk worth the returns? Am I ok with it just because it will be some rigging contractors liability, not mine?

These are not simple questions.

 

[RickR]

Not simple at all.

For me the issue is that the people under the load have no understanding of the risks and therefore no consent is possible. They trust us to keep them safe in all but 'acts of God' situations. Or as I say to amateurs "Is it safe enough for your (grand)child?"

 

[MPowers]

.......... A shell hinged off the back wall and all motorized - no counterweight IIRC - is asking for problems.

Who designed/consulted that particular structure?? Back in '84-'85, can't remember exactly, I was teaching at the U of Maine, Orono while they were building a new PAC. George Izenour was the consultant, but he was hired by the architect not the university and he designed a building that was actually a very nice concert hall that the architect wanted but not the Road House the University needed and wanted. Long story there for another time. Anyway, it had a huge steel shell, side walls were hinged to fold open or closed in 18' tall by 8' wide steel doors on each side, the roof hinged to the back wall in a single large panel. It was roughly 70'-80' wide and 25' +- front to back. The rigging was by Hoffend, I forget who built the shell, might have been Hoffend but I can't recall. The shell structure was 16 g. steel plate rolled in to large cylindrical sections about 18" deep and 4'-6' wide running the entire depth of the shell. The sheets were welded to a framework of I-beams ranging from 3" for the spanning members to 10" for the main beams running front to back. The shell was installed and for about 4-6 weeks, the roof was just hanging there folded to the back wall. The local Vermont rigging company that was doing the install then put the line shaft winch on the grid and in the process of raising the ceiling the first time, got it just past halfway up and the rigging attachment failed ( 'nother long story for another time!) and the roof fell, swung in freefall and slammed into the rear wall which was a stationary version of the same steel shell structure. While falling the roof looked like the famous galloping Gertie Narrows bridge, (I was a witness to the fall) and put huge 3' and 4' dents in the steel back wall. Luckily Hoffend had demanded additional building structure before providing the winch and the shell. (guess I reminded myself, Hoffend did manufacture the shell) As a result there was an additional 12" I-beam running from foundation to the structural grid of the building at each of the hinge points. The accident inspector concluded that without the added beams the shell would probably have pulled free of the hinges or pulled the back wall down at the hinge points when the roof hit bottom. Anyway, just curious if the shell roof collapses listed in this thread are connected in any way??

 

[MPowers]

Gafftapegrenia - Not otherwise touching shell rigging beyond removing middle guide from arbor.

Ron - I think a gear box of shaft (key) issue. Not sure. I will search my laptop and see if I can find a reference. I had, around 1995, been consultant for renovation of Popejoy at UNM in Albuquerque, and we removed a very similar shell - ceiling hinged to rear wall and the motorized rigging.

Again, who was the consultant on this project??

 

[MNicolai]

It was another George Izenour gig. See here: http://www.marcuscenter.org/wp-content/uploads/2013/06/Orchestra.pdf