# Mandalay Bay video wall fall



## jayvee

Little surprised to not see this here yet: https://www.reddit.com/r/Catastroph...0r0/300k_video_wall_came_down_today_in_vegas/


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## Van

Somebody said, "motor got stuck going down" I don't think that kind of smashed up gear comes from a slow motion fall. Something failed. Wish I could see a shot of up top.


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## BillConnerFASTC

Just one more incident to support my refusal to recommend or specify chain motors. Thanks for posting.


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## Van

BillConnerFASTC said:


> Just one more incident to support my refusal to recommend or specify chain motors. Thanks for posting.


A properly sized and maintained chain motor is a perfectly acceptable piece of equipment. 

How would you suggest rigging truss in an arena?


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## BillConnerFASTC

It can be done safely. Just too many times it hasn't been for me. Think of all the safe MAX 737 flights.

I haven't worked on the problem, but I am sure there are safer solutions that fail less, and I'm sure they cost more, probably a lot more.


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## egilson1

BillConnerFASTC said:


> It can be done safely. Just too many times it hasn't been for me. Think of all the safe MAX 737 flights.
> 
> I haven't worked on the problem, but I am sure there are safer solutions that fail less, and I'm sure they cost more, probably a lot more.




Hoist mechanical failure is VERY rare. VERY VERY rare. A large percent of failures attributed to hoist failure are due to operator misuse. 

I've heard a few "on site" versions on what happen in this particular collapse. I am waiting to get more actual data.

Ethan


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## MNicolai

Like @egilson1, I've heard a variety of stories. One guy said they went on break for lunch and found it like that when they came back. Another said motor got latched into going down which I don't believe could've caused that damage and there's no reason someone couldn't have hit an e-stop, and another mentioned that the wrong wire rope diameter was used for safeties and it snapped -- also seems like a pretty extraordinary failure mechanism.

I wouldn't believe anything in the rumor mill right now.


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## Van

Yeah, I head under sized motors, but there are a lot of picks on that truss. Seems odd that all would fail at the same time. Maybe the SR failed first and it was a cascading overload...? IDK.


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## JohnD

To add to the "OH Fudge" factor I wonder if this was on the IN or the OUT?


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## MNicolai

JohnD said:


> To add to the "OH Fudge" factor I wonder if this was on the IN or the OUT?



Out. There are photos flying around Facebook showing it in use during the show.


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## MNicolai

Some photos floating around.





(from someone on FB, all names redacted by me)


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## Van

the gripple safety seems to have failed...


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## MNicolai

@Van, the question being if it was a cause or an effect.


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## egilson1

Van said:


> the gripple safety seems to have failed...




Not necessarily. In my destructive testing of gliders/verlocks it’s not the hardware that fails but the wire rope breaks just adjacent to the fitting. And so far always above minimum breaking strength. I would want to see the hardware to determine if it was the fitting that failed or the was it the wire rope.

Ethan


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## Footer

Its also weird that it came down flat like that. I'm suprised it didn't buckle more. 

Its also amazing to me how many people are carrying video walls out there that have no idea how to rig or the dynamic forces walls can exert. I had a show come in a year or two ago that wanted to hang a wall on house pipe.... dumb.... add to that we are double purchase. Promoter got to pay for local truss and motor for that day.


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## Van

Footer said:


> Its also weird that it came down flat like that. I'm suprised it didn't buckle more.
> 
> Its also amazing to me how many people are carrying video walls out there that have no idea how to rig or the dynamic forces walls can exert. I had a show come in a year or two ago that wanted to hang a wall on house pipe.... dumb.... add to that we are double purchase. Promoter got to pay for local truss and motor for that day.


Currently working on a school. "Yes, I absolutely need your AV subs submittal. I need to know how much their video wall weighs so I can order counterweight for it
..oh and make sure the truss will carry it."


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## microstar

"Slightly used video wall panels available; a few dead pixels"


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## venuetech

A poster (zub93) on The reddit page is saying ....

“This wall was hung on a triangular truss, The LED panels were mounted directly to a pipe, which was in turn boroughed to the triangular truss, as pictured. The triangular truss was then "deadhung" from the box truss, by 5 1-Ton Motors, not 3 as people have been saying. (still hanging at close to trim height in the picture) However, i say "deadhung" as the triangular truss was hung using Jumbo Verlocks, not spansets. Couldn't have been more than 8-10 on the whole wall if my memory is correct. Motor failure caused a shock-load when the truss was bumped, Verlocks failed, the rest is evident.” Zub93

Mike’s photos show the box truss in place with its 5 hoists. And what looks to be a jumbo verlock with cable at the slack end and no cable on the load side of the device.


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## Jay Ashworth

Van said:


> Currently working on a school. "Yes, I absolutely need your AV subs submittal. I need to know how much their video wall weighs so I can order counterweight for it
> ..oh and make sure the truss will carry it."


"Videowall doesn't weigh anything"...


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## Michael K

I've had arena rigging on my mind lately, will definitely be looking out for the final conclusions drawn from this.


Jay Ashworth said:


> "Videowall doesn't weigh anything"...


My arms beg to differ after hanging any significant number of aluminum framed double panels (biggest so far is to 8 m x 4 m/~26 ft x 13 ft, did that one solo, yay arm day!) (Side note, an alum. framed 8x4m wall weighs just over an imperial ton/under a metric ton.)


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## Malabaristo

Jay Ashworth said:


> "Videowall doesn't weigh anything"...



"That is correct, but only because it will be staying in the road cases/on the truck unless you provide me with the information necessary to hang it safely in a timely fashion."


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## MNicolai

Michael K said:


> I've had arena rigging on my mind lately, will definitely be looking out for the final conclusions drawn from this.



I'll be curious what investigation takes place. With no injuries, it may be a strictly private investigation for the purposes of insurance. That could end just being a lot of photos getting taken for later review without an independent third-party surveying the damage first-hand. Could end in a settlement between the riggers and the video wall provider 2-3 years later over the property damage claims.


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## ruinexplorer

Sad, but true. We likely will never hear the exact results of this accident.


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## Les

MNicolai said:


> One guy said they went on break for lunch and found it like that when they came back.



This is the version you tell the boss...


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## TimMc

Les said:


> This is the version you tell the boss...



A former employee of one of our clients tried that line when their mothergrid got tweaked when the upstage line of motors was not engaged during an attempted re-trim. Seems it was done while our crew and most of the house crew were on lunch.

The other issue was that the grid was already loaded.

The ex-employee was terminated after review of facility surveillance video showed he was the only employee with access (keys) to the system who was in the venue in the lunch time frame.


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## Van

Les said:


> This is the version you tell the boss...


I was involved with a rig years ago, at the <insert name of great big hotel chain with big beautiful ballrooms> in Downtown Portland. We installed a great big truss rig, from permanent house points, with chain motors, Hung fixtures, checked everything, ran the rig out to about 3/4's of it's play height and walked away for the night. Came back the next morning and found one corner on the ground along with it's chain motor. The point was torn out of it's spot, apparently they were really weren't rated for what they labelled, But yeah Boss shows up, " It was like this when we found it!"


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## fredthe

venuetech said:


> ...And what looks to be a jumbo verlock with cable at the slack end and no cable on the load side of the device.


I wasn't familiar with verlocks, so I went looking. I found one reference that specifically said "Not To Be Used For Overhead LIFTING*" *though it seems marketed for that. I've also seen both 425 and 500 lb WLL quoted, and have yet to find an official spec.


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## josh88

fredthe said:


> I wasn't familiar with verlocks, so I went looking. I found one reference that specifically said "Not To Be Used For Overhead LIFTING*" *though it seems marketed for that. I've also seen both 425 and 500 lb WLL quoted, and have yet to find an official spec.


I've had speakers (most specifically pendants) delivered from the manufacturer with Verlocks or gripples specifically to be used to hang them and I've seen them used extensively for banners and screens.


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## BillConnerFASTC

Do separate overhead lifting from overhead suspension. For instance, you can dead hang a batten with grade 30, but OSHA - and the chain manufacturers say you can't lift with it over heads.


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## ruinexplorer

Generally Ver-locks are used for leveling, but you always have a safety in place. Since one of them could slip, that could put your rig out of balance and put greater weight on another pick point. If that was a Ver-lock, that is a beafier one than I have ever used.


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## Footer

Malabaristo said:


> "That is correct, but only because it will be staying in the road cases/on the truck unless you provide me with the information necessary to hang it safely in a timely fashion."



I'm using that. I can't tell you how many times a year I hear that.


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## Ted jones

BillConnerFASTC said:


> It can be done safely. Just too many times it hasn't been for me. Think of all the safe MAX 737 flights.
> 
> I haven't worked on the problem, but I am sure there are safer solutions that fail less, and I'm sure they cost more, probably a lot more.



Bill,

When we sell chain hoists, we use ones rated for overhead by the manufacturers. Stagemaker is the one we use. 10 to 1 factor. Secondary brake on the load side. Everything is beefier, not working as hard and we have a manufacturer behind it for those under it. 

The jerk start and stop keeps us from using it too often.

T


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## BillConnerFASTC

Ted jones said:


> Bill,
> 
> When we sell chain hoists, we use ones rated for overhead by the manufacturers. Stagemaker is the one we use. 10 to 1 factor. Secondary brake on the load side. Everything is beefier, not working as hard and we have a manufacturer behind it for those under it.
> 
> The jerk start and stop keeps us from using it too often.
> 
> T


Isnt there a finite life to those per manufacturer?


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## Ted jones

Yearly inspections, parts replacement and machine replacement when appropriate. Much like the rest of rigging equipment is supposed to be in our perfect world. Although, as I said earlier, when the parts are not working hard, IE: At less than 10% of failure, they tend to last longer.


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## BillConnerFASTC

I just looked at Stagemaker maintanence schedule. There are a whole lot of venues where there is not a chance most or all that work will be done, like schools, churches, the vast majority of universities - and I think that's around 99% of venues in US.


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## Ted jones

BillConnerFASTC said:


> I just looked at Stagemaker maintanence schedule. There are a whole lot of venues where there is not a chance most or all that work will be done, like schools, churches, the vast majority of universities - and I think that's around 99% of venues in US.



Using that logic, we should bag most of stage rigging. Again, we start with units that are made to a higher rating than the standard hoists. Essentially double the strength on all parts with the load limited to rating. We also rarely sell this style hoist due to the many issues with chain hoists in the situations that you and I play in. Most are utility hoists for storage not for use during shows.

We all hope the standards are followed, along with manufacturers instructions, but we cannot enforce it.


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## MNicolai

Stagemaker hoists are also pretty keen on chewing up their own chains if you run the chain while there's no load to keep everything taut and plumb.


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## Ted jones

MNicolai said:


> Stagemaker hoists are also pretty keen on chewing up their own chains if you run the chain while there's no load to keep everything taut and plumb.


We have not observed this in the 20+ years of selling them. Probably because they are not used much.

BTW- Are you speaking of the 5 to 1 standard Stagemakers? Or the 10 to 1 units?


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## MNicolai

I heard it 2nd hand from a couple different people while soliciting feedback for an upcoming project. Consensus seemed to be, concept of reversible motor up/down = awesome, reliability of hoists = less awesome. I believe the use case was when they had them set on the ground and were feeding chain through without taking any care to ensure chain entered straight. Something about in the input gearing allowing the chain to misfeed and cause trouble.

I've used them before and not had problems, but only for flying semi-permanent PA speakers that are a very controlled, low turnover application.


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## TimMc

I use electric motor chain hoists on every arena or ltheater I work in. Also took the C-M classes and got my enterainment hoist technician card and cute diploma.

Hoists themselves fail for only a few reasons but the basic causes are lack of maintenance and overloading/severe operation. Almost any failure repair should be based on a full PM disassembly, inspection, replacement of parts as needed, and full lubrication, followed by load testing. Some things only need adjustment, like the limit switches, or obvious replacement like starting caps on single phase hoists.

On a concert tour with 120 points and almost as many hoists, it's common to see only 1 or 2 spare hoists in each size and in the last 6 or 7 shows I've rigged I can recall having to swap out a hoist only once.

I'm not sure how we got to chain hoist reliability unless there is some indication that the Mandalay Bay wall came down because a hoist lost power, control, or somehow got a jammed chain.


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## MNicolai

@TimMc, the most persistent rumor I hear is that whether through malfunction, disconnection, or something missed at the controller, the rig was lowered and one hoist in the group didn't follow. Supposedly that hoist absorbed the load until it couldn't anymore, and then when the load dropped and was caught by the other hoists, it shock-loaded the verlocks to the lower truss which then ate their cables.

Disclaimer / That could all be wrong but from the photos at least looks plausible.


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## DavidJones

MNicolai said:


> @TimMc, the most persistent rumor I hear is that whether through malfunction, disconnection, or something missed at the controller, the rig was lowered and one hoist in the group didn't follow. Supposedly that hoist absorbed the load until it couldn't anymore, and then when the load dropped and was caught by the other hoists, it shock-loaded the verlocks to the lower truss which then ate their cables.
> 
> Disclaimer / That could all be wrong but from the photos at least looks plausible.



I had seen all of those photos and have heard a few similar accounts. It sounds plausible that at some point either only one hoist ran, or one failed to run, or someone ran the hoists down, but accidentally missed a switch, had one hoist set to up.

Either way It was the verlocks on the truss below that failed not the motors themselves. Those look to be 1/4" or 5/16" verlocks. That is a strange way to rig a video wall, to say the least, and with the turnbuckles there, a redundant form of leveling. The way verlocks work can easily wear out the cable and if these cables and verlocks were used often at around the same length it would create one spot on the cable that was particularly worn. All it takes is a couple of broken strands, and the cable is no longer thick enough for the gripping mechanism to hold. I would not have used a verlock to hang this truss, there are much better solutions to hang under a carrier truss.

Side point about stagemakers. It's not that they eat the chain so much as, that any twist in the chain eats the chain guide. The SM series had plastic chain guides and later cast aluminum guides. You MUST run these out of the box with a pickle, and keep tension on the chain the last foot ot two as it takes the weight. Any twist that gets to the guide will shatter or crack it. Typically the chain is fine since its a harder material, but that motor is of no use until the guide is replaced.

The current SR Motor series I think is a lot better about this, and has a lot of much nicer features than most other hoists out there. They also run SIGNIFICANTLY quieter than CM.


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## DavidJones

BillConnerFASTC said:


> It can be done safely. Just too many times it hasn't been for me. Think of all the safe MAX 737 flights.
> 
> I haven't worked on the problem, but I am sure there are safer solutions that fail less, and I'm sure they cost more, probably a lot more.



And this you don't fly also, ever, full stop? 

I don't think this is a fair analogy. The 737 MAX was a manufacturing error. The pilots did not make a mistake, the equipment failed.
Plane crashes do happen, and yet is it still statistically safer than driving, and nobody's going end all commercial flights. 

In the case of this video wall, the motors did not cause this, even it was a motor that got "stuck running," The part that failed was the Verlocks holding the lower truss, which in my opinion was an inappropriate choice of hardware for the application. The fault is not on the gear; it's on a person.

Personally, I have known two people who were involved in runaways in theaters. This is not a reason to never specify counterweight fly systems. People either did not have proper training, or they made a mistake. Just because you don't understand something, are afraid of it, or have limited experience with it, does not make that thing inherently bad, it just means we have the opportunity to learn something new.


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## TimMc

So a couple of phone calls later... the rumour mill grinds out that this was a multi-part failure - operator, design, hoist not working. I have no way of knowing first hand and my Vegas contacts were not on that show so consider this to be at least 4 degrees from Kevin Bacon.

That said, a year or so ago in out downtown arena we had a heavy (lbs/tons,KG) and automation-centric (moving trusses dancing, etc) show that had 1 hoist on the mother grid hang up/not get power/had non-functional control as they brought the grid in. Fortunately the hoist operator hit the Big Red Button when the truss broke, 60 feet in the air. It was loud and for those of us who Had a Frickin' Clue, scared us downstage of the possible/likely "It's Raining Truss" moment. The Weather Girls did not sing, but it took a long time for some of the local hands to move out of the Gravity Sucks Zone in spite of all we graybeards yelling at them to vacate the area. {/story repeat}

I hope to never be a part of such a situation again.

I've said this before - for the most part, there are no accidents, no random and completely unpredictable failure of adequately rated materials, when used and deployed in accordance with KNOWN engineering principles. These are ultimately *people* failures, whether they are from inadequate training, improper training, operator failure to fully and completely implement that training, design defects or improper material selection, or improper assembly/use/storage/transport, one or more persons made a deliberate decision to deviate from best practices. And "stuff" happened.


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## TimMc

MNicolai said:


> @TimMc, the most persistent rumor I hear is that whether through malfunction, disconnection, or something missed at the controller, the rig was lowered and one hoist in the group didn't follow. Supposedly that hoist absorbed the load until it couldn't anymore, and then when the load dropped and was caught by the other hoists, it shock-loaded the verlocks to the lower truss which then ate their cables.
> 
> Disclaimer / That could all be wrong but from the photos at least looks plausible.



Kinda my understanding from the "I wasn't there, but I heard...." mill as well.


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## venuetech

fredthe said:


> I wasn't familiar with verlocks, so I went looking. I found one reference that specifically said "Not To Be Used For Overhead LIFTING*" *though it seems marketed for that. I've also seen both 425 and 500 lb WLL quoted, and have yet to find an official spec.


GripLock is another brand, with the largest for 5/16” cable. Looks to be German made.


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## BillConnerFASTC

DavidJones said:


> In the case of this video wall, the motors did not cause this, even it was a motor that got "stuck running,"



The system failed and the motors reportedly not functioning as they were intended was a part of the system failure. You sound like a politician parsing their words.


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## DavidJones

BillConnerFASTC said:


> The system failed and the motors reportedly not functioning as they were intended was a part of the system failure. You sound like a politician parsing their words.



My point was that from all the information that was gathered, this looks like it was a poor system design and/or application. If I used underrated or worn verlocks to hang something from a batton, and the verlocks failed, would you blame the counterweights, or the arbor, or the head blocks.... or maybe flyman?

Knowing that a motor could potentially go out of weight is part of the consideration when planning something like this. If proper hardware had been used and one motor failed to run, the brake should start to slip at 125% of its rated load, the load would then roughly rebalance. I'd be willing to be this is exactly what happened. It will result in a shock load, but its proper safety factor is observed, the wall probably would have stayed in the air; some of the rigging and motors might have sustained damage. At that point, it would be prudent to cautiously disassemble this system and take the rigging out of service until inspection and load testing are done.


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## egilson1

DavidJones said:


> If proper hardware had been used and one motor failed to run, the brake should start to slip at 125% of its rated load, the load would then roughly rebalance.



Yeah, that’s wrong. The break on cm hoists are designed to hold a LOT more than 125% of rated capacity. Now the protector is designed to slip at 125% to 230% of load. But remember the protector is there to prevent motor from overheating and not necessarily to stop the user from lifting to much.

Another thing that has been bugging me in social media posts about this failure is that everyone is blaming the VERlock/glider. As I mentioned before unless there is evidence that the device physically failed, such as the the ball bearings inside the shaft came out, or the ring cracked, etc, the the photos I’ve seen seem to show that the wire rope itself failed. In every destructive test I’ve done on them the wire rope has failed at over its ultimate strength. I’ve even retested gliders on follow tests and they still worked.

Now we can certainly call into question if they should have been using 1/4” (if that was indeed what size they were working with) wire rope.

But we also can’t tell just by the photos alone. Without examination of the actual hardware we can’t determine what happened.

Ok, off soapbox.

Ethan


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## TimMc

egilson1 said:


> Yeah, that’s wrong. The break on cm hoists are designed to hold a LOT more than 125% of rated capacity. Now the protector is designed to slip at 125% to 230% of load. But remember the protector is there to prevent motor from overheating and not necessarily to stop the user from lifting to much.
> 
> Another thing that has been bugging me in social media posts about this failure is that everyone is blaming the VERlock/glider. As I mentioned before *unless there is evidence that the device physically failed, such as the the ball bearings inside the shaft came out, or the ring cracked, etc, the the photos I’ve seen seem to show that the wire rope itself failed. In every destructive test I’ve done on them the wire rope has failed at over its ultimate strength.* I’ve even retested gliders on follow tests and they still worked.
> 
> Now we can certainly call into question if they should have been using 1/4” (if that was indeed what size they were working with) wire rope.
> 
> But we also can’t tell just by the photos alone. Without examination of the actual hardware we can’t determine what happened.
> 
> Ok, off soapbox.
> 
> Ethan



Yes and yes to the text in bold. Metal fails when loaded beyond its tensile strength and at the point where its elasticity is compromised - a pinch point, kink, etc. Wire rope ain't exactly new stuff and the failure modes are well understood. The design choices based on what we can make from the pictures raise some questions with me as well, but they are unlikely to have *caused* the primary failure, the question is whether or not the design was appropriate for the load and if the design intent was for the secondary rigging to survive, intact, a primary suspension failure.

I hope there are definitive answers to come from the investigation, but because there were no deaths or personal injuries I don't think Nevada OSHA will investigate and any findings by insurance investigators are proprietary.

Ethan, you're absolutely right: without forensic metallurgical analysis we're left to speculation.


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