I recommend googling for the WSJ article "Injuries Put Safety in Spotlight at Cirque du Soleil" because it has a slideshow illustrating the following paragraphs:
According to OSHA, it seemed as if she “flew up at a higher rate of speed than normal toward the grid without tucking in her feet or legs.” The impact of this collision then caused a series of system shocks, ultimately severing the wire rope. Later that night, according to the OSHA files, Kà’s assistant head rigger found the rigger who had been on Guillot-Guyard’s line curled in a ball and crying. He was saying, “I felt the rope go through my hand.”
There may have been nothing he could have done. Ascending with her legs extended, instead of in a tuck—as witnesses testified—Guillot-Guyard collided with the grid. According to the OSHA report, “This collision caused a shock load to the winch; the wire rope came out of the sheave/pulley and scraped against a shear point cutting numerous wires in the wire rope. The wire rope broke apart.” Or as Pearson explained, “The cable jumped out of the pulley wheel and was exposed to the sharp edges of the mounting frame. This happened in a split second, almost instantaneously with the moment of impact. [The] cable got slammed against the edge of the wheel and into the sharp edge of the plate that was behind it, and that cut the cable.”
That part is literally quoted further down in the article and it makes me wonder why all the focus is on the choice of rope with respect to being used in a swivel joint set-up earlier in the article. They might as well have left that out, it's a whole pile of data but it does not actually seem to have been a factor in the accident at all.
The cord was cut. It was not an issue of internal torques or swivels.
Unless the helicopter rescue rope was made of a higher shearing strength material that would have gone through the harness without being cut it wouldn't have mattered
Simple material strength is not the only consideration. I'm not saying ULT4 rope would have been better in this case, but it is worth noting that ULT4 comprises strands which are not round and are arranged in a special pattern which among other things widens the contact patch with drums, sheaves, etc.
I'd like to see the design of the block with sheave that the rope came out of. Some designs have the rope quite captive, while in others it's easy for the rope to come out (sometimes intentionally).
The point is, there is a lot going on when you see one of these shows--it is truly "high performance."
Shear strength for rope is a totally different parameter than load-bearing capability. It looks from the account that the rope encountered something approaching a knife edge while traveling at high speed. It could have all the load bearing capacity in the world, if it isn't designed to deal with impact damage like that it will fail.
What surprises me about the whole affair is that a single rope breaking could lead to a death. This may be a function of the degrees of freedom required for the artists, so don't take this as a 'why don't they' entry, more of a what parameter caused them to choose this particular setup?
My experience is on high-performance sailboats rather than acrobatics, but single-rope seems to be the standard. You could imagine having two ropes for redundancy, but then not only would swiveling become more complex (at the sheaves, not the swivel), you would have something like twice the rope weight damping the movements of the acrobat.
Coming from a sailing background, another question would be: could they use synthetic/polymer ropes? Where cost is not much of a concern, things like Dyneema have taken over in a lot of roles.
Funny, I was writing that with my stint for a sailmaker in the back of my mind and yes, single rope is the standard. But in sailing gravity is not always luring to catch you if something goes wrong (though you can absolutely die from an accident during sailing if a line (or a stay) breaks).
Probably a better comparison would be mountaineering and there there are plenty of people that climb without ropes at all...
"Yet Cirque, as a corporate enterprise, is very different from Disney or MGM. Because it is a circus, the viability of its business is rooted in the willingness of a core group of performers to risk their lives on a daily basis."
It's completely tangential, but if anyone here is interested in learning circus skills, I'd highly recommend it. It's a great laugh and a fun way yi keep fit.
Source: used to teach juggling and similar, poi and other circus skills in my youth.
As a rock climber I see this entire 'ropes breaking' discussion very odd. Ropes carrying people shouldn't break. Full stop. There shouldn't be any sharp edges. Weight, even impact forces, shouldn't come anywhere near thinking about breaks. A rope should never be able to slip off a pulley. If it can, then the pulley needs to be redesigned. If it has any sharp edge then it is not to be trusted. Look at the equipment in at any climbing store. You won't find anything even remotely sharp.
Climbing ropes (rock climbing, not mountaineering) basically do not break. An entire system of standards mean that no matter how one falls, no matter the angle and accidental nature, the rope is expected to survive. To see actors hung off systems with sharp-edged pulleys and unconstrained rope movements with little regards for accidental or unexpected forces terrifies me.
I was hoping for a mountaineer to speak up. Thank you for this comment. I have zero knowledge of mountaineering other than that I used some mountaineering gear to do roofing work and the whole 'sharp edge' and 'rope jumped pulley' thing as well as the fact that there is no automatic shut-off should a line get caught (they hint in the article that the winches would keep running if a line gets caught) is troubling to me. The problem with such thinking is that it leads you to go 'why don't they' and that's not a very productive path for a lay-person in the field. OHSA presumably has been over this with a microscope and it is strange that none of those issues deserved a mention. Personally - if I were inclined to put my life at stake in a circus - I would have wanted to know exactly how all of this gear that my body is suspended from is working and how it is rated (and if such information would not be shared then I'd leave). It's got to be pretty safe though because with all the cycles it has gone through there have not been more accidents.
OHSA should, but they are not experts in the field. Nobody is. Circus is a constantly evolving practice. Everything is new. EveryONE is new. The stages are all temp installs. And there are only ever a couple hundred people in the country doing this sort of act at any one time. There are some old hats, but there isn;t that large community needed to establish was are and aren't statistically safe practices.
OSHA does well with factories where thousands of people perform the same actions thousands of time. They do not do well with one-off jobs.
Imagine being an OHSA inspector, an expert in fall arrest, and walking into a scene where an acrobat was hanging by a single wire rope (no backup device or soft spot) over a tank of water, in total darkness, while on fire ... and the tank is full of live killer whales. And the whole rig was build last month and will probably be torn down in a couple months. Such a scenario isn't much of an exaggeration.
That's an excellent point, yes, the temporary nature of the circus business changes everything. Even so 'sharp edges' and 'rope' in close proximity give me the willies.
Another point that surprised me was the reference to the Cirque performers desiring an adrenaline rush, which seems at odds with safety. I've read of rock climbers saying that everything should be calm when they are climbing and that if there's ever an adreniline rush, it means something has gone wrong.
Ya, um, well, that is the sort of thing climbers say when cameras are around, like a baseball pitcher remaining calm as he throws a perfect game. Adrenaline is always part of climbing.
18 comments
[ 3.2 ms ] story [ 34.4 ms ] threadAccording to OSHA, it seemed as if she “flew up at a higher rate of speed than normal toward the grid without tucking in her feet or legs.” The impact of this collision then caused a series of system shocks, ultimately severing the wire rope. Later that night, according to the OSHA files, Kà’s assistant head rigger found the rigger who had been on Guillot-Guyard’s line curled in a ball and crying. He was saying, “I felt the rope go through my hand.”
There may have been nothing he could have done. Ascending with her legs extended, instead of in a tuck—as witnesses testified—Guillot-Guyard collided with the grid. According to the OSHA report, “This collision caused a shock load to the winch; the wire rope came out of the sheave/pulley and scraped against a shear point cutting numerous wires in the wire rope. The wire rope broke apart.” Or as Pearson explained, “The cable jumped out of the pulley wheel and was exposed to the sharp edges of the mounting frame. This happened in a split second, almost instantaneously with the moment of impact. [The] cable got slammed against the edge of the wheel and into the sharp edge of the plate that was behind it, and that cut the cable.”
The cord was cut. It was not an issue of internal torques or swivels.
Unless the helicopter rescue rope was made of a higher shearing strength material that would have gone through the harness without being cut it wouldn't have mattered
I'd like to see the design of the block with sheave that the rope came out of. Some designs have the rope quite captive, while in others it's easy for the rope to come out (sometimes intentionally).
The point is, there is a lot going on when you see one of these shows--it is truly "high performance."
What surprises me about the whole affair is that a single rope breaking could lead to a death. This may be a function of the degrees of freedom required for the artists, so don't take this as a 'why don't they' entry, more of a what parameter caused them to choose this particular setup?
Coming from a sailing background, another question would be: could they use synthetic/polymer ropes? Where cost is not much of a concern, things like Dyneema have taken over in a lot of roles.
Probably a better comparison would be mountaineering and there there are plenty of people that climb without ropes at all...
Direct link to the slideshow: http://graphics.wsj.com/cirque-embed-only-042215/?embed=1
I think I'll remember that one.
Source: used to teach juggling and similar, poi and other circus skills in my youth.
Climbing ropes (rock climbing, not mountaineering) basically do not break. An entire system of standards mean that no matter how one falls, no matter the angle and accidental nature, the rope is expected to survive. To see actors hung off systems with sharp-edged pulleys and unconstrained rope movements with little regards for accidental or unexpected forces terrifies me.
OSHA does well with factories where thousands of people perform the same actions thousands of time. They do not do well with one-off jobs.
Imagine being an OHSA inspector, an expert in fall arrest, and walking into a scene where an acrobat was hanging by a single wire rope (no backup device or soft spot) over a tank of water, in total darkness, while on fire ... and the tank is full of live killer whales. And the whole rig was build last month and will probably be torn down in a couple months. Such a scenario isn't much of an exaggeration.