Another flying issue

[Mark Dawson]

Re: Another flying issue

Yeah, I posted it here as I consider it not good for many of the reasons given here. The owner thinks its fine, hence I opened it up for comment. I agree with Tim here, the load on the front means there's tension on that DIY weld at the rear mounting point. Putting the whole chance of failure onto a unqualified weld means it's a no go in my book. It might stay up, but theres no guarantees. It's the guarantees that calculates the risk that insurance companies bank on. Not to mention the potential for loss of life.

 

[Mark Dawson]

Re: Another flying issue

Also, saying that this is acceptable is opening up the floor for people to weld up some scrap, decide it'll be good enough, and fly overhead loads on it. The weight is irrellevent. Try catching 300 pounds that's accellerating my 9.8 metres a second every second. At that weight and height you won't feel the headache for long.

 

[Per Søvik]

Re: Another flying issue

In my experience, good workmanship trumps certificates every time. The load-bearing capability of a certificate is next to zero, and you really only need approval for structures that come crashing down, the ones that stay up tend to get on fine without the certificates. Obviously, a truss-lift or a tower from a reputable manufacturer complete with the right papers, is a good starting point, but there is a lot of crap to be had as well and not all approval and inspection is worth anything. I've seen too much work signed off by people that were obviously clueless, and would much rather trust my life to solid equipment put together by competent people than a certified structure assembled by morons.
In Norway the integrity of these things are hardly a problem, the entertainment industry hardly ever works down to a price point, so the equipment tend to be top notch, and people working in the industry never risk getting fired for speaking their mind on safety issues. Use of substandard equipment is far more widespread in the "real" industries where bean-counters and purchasers that earn their bonuses by replacing the good stuff with "equivalent" crap.

 

[Helge A. Bentsen]

Re: Another flying issue

In my experience, good workmanship trumps certificates every time. The load-bearing capability of a certificate is next to zero, and you really only need approval for structures that come crashing down, the ones that stay up tend to get on fine without the certificates. Obviously, a truss-lift or a tower from a reputable manufacturer complete with the right papers, is a good starting point, but there is a lot of crap to be had as well and not all approval and inspection is worth anything. I've seen too much work signed off by people that were obviously clueless, and would much rather trust my life to solid equipment put together by competent people than a certified structure assembled by morons.

Try telling that to your insurance company when you have an accident.

In Norway the integrity of these things are hardly a problem, the entertainment industry hardly ever works down to a price point, so the equipment tend to be top notch, and people working in the industry never risk getting fired for speaking their mind on safety issues. Use of substandard equipment is far more widespread in the "real" industries where bean-counters and purchasers that earn their bonuses by replacing the good stuff with "equivalent" crap.

I wish this was true. Sadly it isn't.
There are a lot of dangerous stuff going on all the time because a lot of people don't know how to do it "right". I'll admit that I've done it myself several times because I didn't know any better at that time. There are companies out there who don't inspect and rate their equipment because "we'd never had any accidents, so why should we bother to spend all those $$$ each year on paperwork". Price points are a major issue, and lowering your overhead costs by doing shortcuts is tempting for a lot of people.

If it's not rated, it shouldn't be used.
If it's rated and certified, it should be inspected by a competent person every time before it's used.

However, there are a strange exception to this. If you suspend something as a part of a permanent installation, and there are no moving parts, like a speaker suspended from a structural part of a building, technically you could do this without rated hardware. I have no idea why.

 

[Per Søvik]

Re: Another flying issue

Try telling that to your insurance company when you have an accident.

If you plan on having an accident, you'd better have all your certificates ~;-)~:wink:

I'm just saying that avoiding accidents have got a lot more to do with the people putting up the stuff than the certificates that comes with the stuff. I've seen scaffolding that was brand new, certified and signed off come crashing down. My collegue that wrote the work permit was in the clear because the structure was properly signed off by the company putting up the scaffolding. The guy that fell down and broke his leg was covered by the insurance, and the company and the employee that built and signed off on the scaffolding was in the clear because all the paperwork had been done. Makes you feel nice and safe, doesn't it?

I wish this was true. Sadly it isn't.

Helge, you are travelling all over the world doing sound, so you must know the kind of cut-throat pricing you see in Britain and other countries. In Norway, even if you can't afford to pay for the inspections (the yearly inspection of a shackle probably costs more than the purchase price), at least the rigging equipment tends to be top notch and according to spec. I'm not talking about people flying old, non-flying equipment, and wonky groundstacks that look like it might come crashing down at the first hard hit of the bass drum, but the line arrays currently in use by bigger and medium sized providers.

 

[Art Welter]

Re: Another flying issue

Quite honestly, I see very little wrong with that system. They have the truss loaded in its strongest direction, they aren't relying on the motors to hold the load, they've definitely overbuilt that "knocked-up design".

Milt,

Whether "overbuilt" or not, the triangle truss is loaded in it's weakest direction.
The load is carried well in front of the truss, putting the two forward (downstage) members in compression, while the single rear (upstage) member is in tension, each weld and pin is being pulled apart by the lever arm holding the 1000+ pounds of speakers, flying frame, top rig and motor weight.
The outrigger load point looks to be about twice the width of the truss, so well over a ton (2000 pounds) of tension is on the rear member, assuming Mark Dawson's figure of 251 pounds per speaker is correct.
A tension failure is far more likely than a compression failure in that rig, turning the truss around so two members are in tension would cut the tension load in half.

Art

 

[Helge A. Bentsen]

Re: Another flying issue

Per,

Part of the problem is that several companies have sold off their "old" line arrays to new and smaller companies. I've seen several of these companies having name-brand equipment but no idea how to deploy and fly it. That's scary. People have been killed in the past due to accidents because someone did stuff they thought was right or by old habits. Moving from being a small provider with a stackable rig to putting something heavy in the air requires real knowledge and a lot of $$$, not everybody does this properly.
I've seen a fair share of poor workmanship and bad equipment around the world, here we have a more dangerous combination; name brand gear and poor workmanship. Some of these people get bigger gigs than they can handle just because they have the right brand name on their gear, but they have no training and no QC on their flying hardware. It's scary as hell. Just because someone is able to buy a line array with the right sticker doesn't make them qualified for rigging it.

As I see it, there really is no excuses to compromise with these things. I've refused on several occasions to put stuff up in the air because the flying hardware wasn't rated or certified. Some people claim "the show must go on", I don't think this is a wise attitude towards safety issues. I'd rather catch hell for not doing something that I consider dangerous that risk serious injury and death.

 

[Milt Hathaway]

Re: Another flying issue

Milt,

Whether "overbuilt" or not, the triangle truss is loaded in it's weakest direction.
The load is carried well in front of the truss, putting the two forward (downstage) members in compression, while the single rear (upstage) member is in tension, each weld and pin is being pulled apart by the lever arm holding the 1000+ pounds of speakers, flying frame, top rig and motor weight.
The outrigger load point looks to be about twice the width of the truss, so well over a ton (2000 pounds) of tension is on the rear member, assuming Mark Dawson's figure of 251 pounds per speaker is correct.
A tension failure is far more likely than a compression failure in that rig, turning the truss around so two members are in tension would cut the tension load in half.

Art

Please look at the pics again. All three beams of that truss are in compression, as there is a pull down strap on a beam on the upstage of the assembly. Also, there is no way those speakers weigh over 250# each. 75# each is more likely. That's why I estimated a total load on the downstage side to be approximately 400# including rigging and winch.

Worst case there is 500# on each of the downstage beams, if the strap is tensioned equal to the weight of the total speaker/rigging load.

 

[Per Søvik]

Re: Another flying issue

Per,

Part of the problem is that several companies have sold off their "old" line arrays to new and smaller companies. I've seen several of these companies having name-brand equipment but no idea how to deploy and fly it. That's scary. People have been killed in the past due to accidents because someone did stuff they thought was right or by old habits. Moving from being a small provider with a stackable rig to putting something heavy in the air requires real knowledge and a lot of $$$, not everybody does this properly..

Definitely, there are risks in the second-hand market, but again I believe the trend you see in Norway is that rigs are handed off as complete sets with the proper rigging hardware as opposed to a collection of boxes with no rigging hardware that you often find in the bigger markets.

I've seen a fair share of poor workmanship and bad equipment around the world, here we have a more dangerous combination; name brand gear and poor workmanship. Some of these people get bigger gigs than they can handle just because they have the right brand name on their gear, but they have no training and no QC on their flying hardware. It's scary as hell. Just because someone is able to buy a line array with the right sticker doesn't make them qualified for rigging it.

Unfortunately that is true for any line of work that involves heavy equipment with the potential to maim and kill. Strict rules and good systems for competence assurance could go a long way of making a lot of things safer, but in the end it all comes down to individuals. Individuals doing the job, individuals certifying the ones that do the job, individuals signing off on jobs etc.

As I see it, there really is no excuses to compromise with these things. I've refused on several occasions to put stuff up in the air because the flying hardware wasn't rated or certified. Some people claim "the show must go on", I don't think this is a wise attitude towards safety issues. I'd rather catch hell for not doing something that I consider dangerous that risk serious injury and death.

...and that's where being Norwegian is an asset. In our culture we have a healthy disrespect for authority, we are not afraid to challenge and speak our mind and we are brought up to think for ourselves. Working for a multinational company with facilities in different parts of the world I can state with confidence that the average Norwegian worker is more likely than most to react when things don't look right. Obviously, you still need the competence to tell when things are not right :?~:-?~:???:

 

[Mark Dawson]

Re: Another flying issue

Milt,

Whether "overbuilt" or not, the triangle truss is loaded in it's weakest direction.
The load is carried well in front of the truss, putting the two forward (downstage) members in compression, while the single rear (upstage) member is in tension, each weld and pin is being pulled apart by the lever arm holding the 1000+ pounds of speakers, flying frame, top rig and motor weight.
The outrigger load point looks to be about twice the width of the truss, so well over a ton (2000 pounds) of tension is on the rear member, assuming Mark Dawson's figure of 251 pounds per speaker is correct.
A tension failure is far more likely than a compression failure in that rig, turning the truss around so two members are in tension would cut the tension load in half.

Art

Hi Art, exactly my point. There's a tension load on a single point of failure of dubious origin. Also my 251 pound figure is for the total of the 4 speakers (derived from the rcf website.

Chur

 

[Per Søvik]

Re: Another flying issue

Art, Mark & all, you are arguing this case based on false assumptions from an engineering point of view.
Weight is relevant, the whole structure is in compression, the ratchet strap might very well be rated (probably at 2500 to 3000 lbs) and certified (allthough I doubt it), the welds look ok as far as we can tell etc. The structure looks sound from an engineering point of view, particularly given the light load it is obviously carrying.

If you argue that it is not legal based on rules and regulations that state that certain thing have to be in a certain way, that is fine and I have no problem with that.

Most of us are aware that lifting equipment have to follow certain standards, welds have to be certified, damaged equipment have to be scrapped, equipment have to undergo yearly inspections. There are sometimes uncertainties and ambiguities in respect of what constitutes lifting equipment and what is sourrounding structure, and some of us are obviously clueless as to specific regulations for the music and theatre industries both in other countries and sometimes even in our own country allthough we are familiar with the laws about safe working practices, internal control etc.

 

[Dick Rees]

Re: Another flying issue

the whole structure is in compression,

How is this?

 

[Randy Gartner]

Re: Another flying issue

I'm certainly not defending the use of un approved equipment.However most of the disaters we have witnessed in recent times happened with " approved ' equipment.

 

[Mike Pyle]

Re: Another flying issue

How is this?

That would be assuming that the rear strap is pulling down with a force equal to the weight in front, in which case the compression force on the truss would be twice the weight of the array.

 

[Tim McCulloch]

Re: Another flying issue

I'm certainly not defending the use of un approved equipment.However most of the disaters we have witnessed in recent times happened with " approved ' equipment.

Yes, and used in a manner not consistent with the ENGINEERING of the structure or components. The Radiohead roof collapse in Canada this past June, for example. The band brought extra stuff (video, IIRC) and wanted it hung in places the load could be not safely supported. When the on-site person responsible for the roof & stage said "no", he was fired and a seemingly random person was hired on the spot. New guy says "sure, let's do it" and the band's drum tech was killed. Also note that in the absence of wind and storms, most rigging & support failures occur during the lift.

This is why rigging is a *system*. This is why it's important to have the assurance of proper engineering, materials and fabrication. With the contraption in the pictures, we have ZERO, ZIP, NADA in the way of assurance. As for the relative weight differences, 250# will kill you just as dead as 2500#.

Finally, when I see something like this at a fair or festival, I usually want a much closer look at the power distribution, too...

 

[Per Søvik]

Re: Another flying issue

How is this?

The ratchet strap at the rear pulls down on the rear member of the top rail, offsetting the pull of the speaker load, and depending on the tension of the ratchet strap, puts a compressive load on the rear member of the truss. Not that it is needed for that purpose, the tension on the rear member wouldn't exceed 700-800 lbs, a relatively modest number compared to using the same truss in a horisontal configuration and loading up with lights and stuff. As a rod by itself is less likely to fail under tension than in compression, I wouldnt worry about the tension stress anyway. The rear ratchet strap stabilizes the whole construction though, and the combination of tension and compression along paralell axes go a long way in providing for a very stable construction.

 

[Tim McCulloch]

Re: Another flying issue

That would be assuming that the rear strap is pulling down with a force equal to the weight in front, in which case the compression force on the truss would be twice the weight of the array.

And if that triangle truss was designed to be a vertical tower and support a top-borne load (which it might be, we just don't have enough info), that ONE part of this contraption MIGHT be within spec. But how do we know for sure?

The problem with the strap is there is no obvious way to determine if the tension on the strap is equal to the force applied by the load sticking out past the tower's COG, born by the head block. This is why support towers typically user roller head blocks and sleeve blocks that ride up the tower - the load distributes equally. IF there was a dynamometer in line with the strap, we could do a little math and see how much tension would be needed. Then it would be necessary to apply that amount of force, monitoring it with the dyno, and for the strap and ratchet to continuously bear that amount of force with a safety margin of at least 5:1 if there were no humans in the possible fall zone; 7:1 or 10:1 is required in some jurisdictions.

Then we get back to the design of the head block.. how do we KNOW that the design shape, materials and construction are suitable without a professional engineer examining the design? What about proof of performance, i.e. destructive testing?

Just some things to think about...

 

[Charles Harrigan]

Just as an aside, the typical breaking point of a locking caribeaner is about 3700 pounds. So for a safety factor of 10 that would be 370 lbs, however; the literature has limits based on shock loading and states that they must be discarded after a certain number of shock events. Also they are made of aluminum which has a much shorter fatigue life than steel, though to what extent I can't say. It also says that for safety systems that may experience shock loading, the biner shouldn't be in contact with other metal devices. Climbing gear is designed to be as light as possible and still protect you from your mistakes. It was never intended to be used for rigging or overhead lifting.



Sent from my neural implant

 

[Per Søvik]

Re: Another flying issue

And if that triangle truss was designed to be a vertical tower and support a top-borne load (which it might be, we just don't have enough info), that ONE part of this contraption MIGHT be within spec. But how do we know for sure?

I'm quite sure that is a horisontal truss, the cross members indicates that.

<snip>
Just some things to think about...

Thinking is allways good, think twice - do once.
One question one should allways ask is if there is a single point of failure that will make the whole construction or the load come crashing down.

 

[Evan F. Hunter]

Re: Another flying issue

Im likely missing something, but I still dont see it. What is holding the truss vertical with a load suspended out on the top front? The blue truck strap?