The use of Safeties

[ianl]

maybe someone could market an inertia safety where the lump attaches to the truss and the wire gets pulled up to the roof

[Andrew C]

Can someone put my mind at rest here? I was under the impression that inertia reels only locked on a sudden application of load, and as such, would be of no use if a motor started slipping slowly....

[Wilf dLampy]

If a motor is slipping slowly enough for the inertia to keep running out (which IMHO is unlikely on a chain-based motor) then it will take quite a while for the load to reach a point where it is in a position to cause injury. (note- this is my own opinion, don't rig something based on what I say)

 

Having said that, there are situations where inertias would not be appropriate. Off the top of my head (and I'm open to corrections on this) if a truss was suspended above another and in the event of failure dropped onto this lower truss the bottom truss would be (potentially) subjected to the load of both trusses. The bottom truss system (truss, rigging etc) may not have been designed to take this load- even gradually applied- and could in turn fail itself.

 

Long winded way of saying "make sure the equipment you are using is suitable for the task"

[Nick Evans]

Maybe taking a lead from the transport industry at large and developing on the meatrack/dolly ideas used elsewhere in our own industry might be a step forward.

A meat rack full of cable?

 

Whether or not to use a bridle is entirely dependent on the needs of that particular point. The inertia is used as an independent secondary suspension. Yes, there are times when this means putting a (seperate) bridle on it, but it's still easier and safer than a traditional steel drop.

If a point needs to go between two beams, you bridle or use spreader truss. In the touring environment spreader truss is most commonly used in venues which are either low or have insufficient bracing to accept a bridle. If the point is bridled the inertia must also be bridled otherwise it will not oppose the load applied to it. I am not sure you will find a manufactirer who condones the use of inertias with anything but a vertical application of load.

 

but it's still easier and safer than a traditional steel drop.

What exactly is easier?

 

It may be easier to leave the inertia connected to a grounded truss and (evenly) pull it up extending as you go

No comment.

 

tie a lightweight line to the inertia, send it up and then the ground crew pull it out and then attach the line to the next inertia they send up.

You nearly got it but then....

Each inertia is rigged with a tagline attached. When the inertia is required (e.g. once the pickups are on and it is about to be floated) the taglines are used to pull the hooks down for fixing to the truss with the truss pickup of your choice. The tagline is coiled and fixed such that it cannot fall but not untied from the hook. Later, during the load out, the tag lines are used when the hook is released from the truss such that the hook is allowed to retract in a controlled manner.

 

maybe someone could market an inertia safety where the lump attaches to the truss and the wire gets pulled up to the roof

I suspect that this will probably end up as a solution.

[Wilf dLampy]

If the point is bridled the inertia must also be bridled otherwise it will not oppose the load applied to it. I am not sure you will find a manufactirer who condones the use of inertias with anything but a vertical application of load.

<{POST_SNAPBACK}>

If you attach an inertia to a bridle it is having only a vertical load applied to it. The horizontal load is being created/absorbed by the O-ring or shackle at the bottom of the bridle.

 

I do like Ianl's idea of a truss-mounted inertia block, a similar design to the harness-mounted inertia systems currently available.

 

While we're on the subject of safety's and ideas for manufacturers, how about mirror balls with integral rotators, so you're not providing a secondary support to just the (little) rotator and not the (big) mirror ball itself. Personally I don't have the budget to R+D this with a moving head light and a mirror ball :blink:

[peternewman]

While we're on the subject of safety's and ideas for manufacturers, how about mirror balls with integral rotators, so you're not providing a secondary support to just the (little) rotator and not the (big) mirror ball itself. Personally I don't have the budget to R+D this with a moving head light and a mirror ball :blink:

<{POST_SNAPBACK}>

It wouldn't even need to be that complicated. All you would need would be a standard motor and then some sort of commutator/ring and brush type system. I'm not sure if it would be safer however, at the moment if a mirror ball fell only a lightweight polystyrene ball falls, if however it had a motor in its going to be considerably heavier. From the sounds of your moving light comment basically all you want is the mirror ball on a fixed spindle not dangling on a length of chain. In fact some of the cheap disco style ones already do this and I guess it is probably safer.

 

PN

[Chris Higgs]

The 'inertia down', as opposed to 'up', was researched by the company that ended up owning BH Sala some years ago.

I took an R&D guy around several venues I was involved with to see the application I had in mind.

Sadly, as with many things we think about a) there was not sufficient volume to make it worth their while, and b) he was not all convinced the units they had in mind (2000 kgs +, big ones to make it all worth while and mounted in a truss section) would actually work upside down.....

 

The contention that the HSE are out to stop us all working (OK that's a slight precis) is incorrect IMO. There isn't a limit to loads being handled and the other things people trot out. Everything is down to risk assessment and I hope that we are all getting involved in doing them, because if we don't some non entertainment industry person is going to do it for us. Then we may find there are some silly rules. At present, we can decide what we do and how we do it.

I firmly believe that LOLER, the Management Regs and the WaH Regs help, not hinder. Learn the rules.

Of course there will be some people who insist that the law is irrelevant, - easy to say if you aren't being held to account.

 

As far as motors go, a 1000kg motor may have a brake capable of holding say 350% of SWL (so maybe 3500kgs) and when de-rated to holding say 500 kgs will have an increase in headroom to say the least. The whole of the lifting industry is based on the concept of factors of safety as we all know.

If all motors were 2 tonners not 1 tonners, and all 2 tonners were 5 tonners, I would have less of an issue with the idea of secondaries being pointless.

In Germany the infamous VBG70 and now BGV C1, where it might be applied to chain motors, is based in that notion.

When I started and certainly when 'working for the house', production motors used to slip quite frequently, trusses were often well past their sell by date and yes, we had a show to get on. So we used to get as much stuff wrapped around as much stuff as possible. Admittedly, things improved and by the late 90's I would suggest not many shows were that bad on the arena circuit, but smaller scale shows and some rigging on theatre tours was not so hot.

There are still a lot of companies that aren't aware of what LOLER is about, and although the rigging and motor side may be much improved, as I said some time ago, there are still companies who don't inspect their trusses (and some who have never had anything looked at).

Of course there should be secondaries along the truss if need be - it's not just the motor or point I'd be concerned about, perhaps that was not as obvious a statement as I had imagined.

The issue is to prevent loads from being uncontrolled, not just to bypass motors.

 

I still prefer a secondary because then there is no argument (assuming you subscribe to my belief that the secondary should be as good or better than the primary) and you can show you have done everything reasonable and practicable as a means of affording security, particularly since we are lifting over people in many cases. Again, if the secondary is not rigged with the expectation it will take any load, Nick is quite right, don't bother and take your chances in court.

Yes, it is a remote risk, but the consequences are potentially catastrophic so the reaction should be in proportion to the risk.

 

I appreciate the points Nick rightly makes about driving, promoters and the rest, but to accept it as 'the way it will stay' is surely what a lot of us, certainly the PSA, ABTT and PLASA want to get away from. It will be hard, and although I am not directly involved (and appreciate that therefore it is easy for me to say) I do devote most of my waking hours to trying to help that process along.

[MartinGreen]

The 'inertia down', as opposed to 'up', was researched by the company that ended up owning BH Sala some years ago.

I took an R&D guy around several venues I was involved with to see the application I had in mind.

Sadly, as with many things we think about a) there was not sufficient volume to make it worth their while, and b) he was not all convinced the units they had in mind (2000 kgs +, big ones to make it all worth while and mounted in a truss section) would actually work upside down.....

<{POST_SNAPBACK}>

 

Tractel, who are a global supplier of Load arrestors do have a load arrestor that can be used "inverted".

 

Hopefully this link will get you to the product you are talking about.

 

Load arrestor that fits in truss

 

This is available currently up to 1t WLL and 25m HOL. I don't know if its the answer, but it might help. I saw them at PLASA a couple of years ago.

 

If you want further info on them, give me a call and I will Email you a PDF with all the information.

[Wilf dLampy]

at the moment if a mirror ball fell only a lightweight polystyrene ball falls, if however it had a motor in its going to be considerably heavier.

With three foot and larger mirror balls the weight of the ball can really add up, even before the rotator is attached :blink:

 

From the sounds of your moving light comment basically all you want is the mirror ball on a fixed spindle not dangling on a length of chain. In fact some of the cheap disco style ones already do this and I guess it is probably safer.

<{POST_SNAPBACK}>

Yep, my other interest in this was that the rotator would be suitably rated for the mirror ball it is turning. There wouldn't be the option of putting an unsuitable rotator on a ball, as it would be integral to the design.

[Chris Higgs]

Ah, the Tirfor 'Blocstop' with a 'Coilamatic'. How do they behave on a truss?

The only experience I have of Blocstops was not happy, needed a lot of nursing which kind of defeated the object. Admittedly they were rented from a plant hire place and were a bit grubby, but I think at present I would be concerned about them being used as permanent installs.

 

What the guy I referred to had in mind was the Globestock type and with a reasonable HOL - 9m, but with a 2000kg SWL, they gave up.

Rigging them at the appropriate height on a stinger is the way forward, I reckon.

[Brixton]

If a motor is slipping slowly enough for the inertia to keep running out (which IMHO is unlikely on a chain-based motor)

Stranger things have happened chap I think I recall Pete Rayel saying he had been on a truss and as he skipped merrily toward a hoist it started to cruise earthwards. I believe that at the time Verlindes had both a clutch and a brake. One was tight and the other loose when the load was "rig" the motor was fine but as the load became "rig plus rigger" it started going. I believe he affected a quick fix by ramming a pen through the chain link in the dead chain!

Maybe it wasn't Pete but it was a long time ago and I was probably under the influence at the time. I did spend most of the 80's/90's under the influence.

[Nick Evans]

A concern has been raised that there may be people reading posts in this and other threads and taking the contents as the gospel truth. Any person who undertook any practice based on what they had read on the internet and nothing else is in my opinion making an uninformed and ill-judged decision. Any activity at work must be undertaken with due consideration to the prevailing legislation and licensing requirements, whether you consider them relevent or not. "Some bloke on the internet said it was ok" will not stand up in court, neither will your insurance company support you. If you don't know, you are probably not qualified to be doing it and should seek the advice of one who does, not through the internet but through recognised suppliers of rigging services.

 

Hello P.D.

[gareth]

A concern has been raised that there may be people reading posts in this and other threads and taking the contents as the gospel truth. Any person who undertook any practice based on what they had read on the internet and nothing else is in my opinion making an uninformed and ill-judged decision. Any activity at work must be undertaken with due consideration to the prevailing legislation and licensing requirements, whether you consider them relevent or not. "Some bloke on the internet said it was ok" will not stand up in court, neither will your insurance company support you. If you don't know, you are probably not qualified to be doing it and should seek the advice of one who does, not through the internet but through recognised suppliers of rigging services.

Fair point. We do have a warning attached to our Safety forum which reads as follows :

The Blue Room Safety Forum is provided for the informal discussion of safety-related technical production matters. No warranty is implied concerning the accuracy of any information contained therein. The administrators of this site can accept no responsibility for any inaccuracy of information in the Safety Forum, or for any loss, damage or injury arising from any interpretation of its contents. Opinions expressed are not necessarily those of the site administrators. If in doubt, consult a qualified professional.

There's a similarly-worded one attached to the Electrical & Power forum. If people are starting to take information that they read here as being the gospel truth, perhaps the Staging & Rigging forum should have a warning too?

[Nick Evans]

After re-reading the last few posts...

 

I still prefer a secondary because then there is no argument (assuming you subscribe to my belief that the secondary should be as good or better than the primary) and you can show you have done everything reasonable and practicable as a means of affording security, particularly since we are lifting over people in many cases. Again, if the secondary is not rigged with the expectation it will take any load, Nick is quite right, don't bother and take your chances in court.

I have never said "take a chance". The whole contention of my argument is that in my personal opinion safeties do not add any extra safety value and contribute towards added risk. This has been outlined ad nauseum previously. When I hang safeties I do so in such a manner that they will work, because I take pride in what I do, even when I believe (and still believe) there is a mathematical argument to support my position regarding safeties. (And risk assessment is exactly that, assigning a number to a risk. Breaking hazard and frequency down into matrices is a way of simplifying it IMHO, mathematics is used for proper FMEA, FMECA and fault tree analysis, though none of these last three take account of human error as it is impossible to quantify)

Rigging them at the appropriate height on a stinger is the way forward, I reckon.

I think you all know what I am going to say, it doubles the number of points to be pulled up, increasing exposure time etc. etc. etc.

Of course there should be secondaries along the truss if need be - it's not just the motor or point I'd be concerned about, perhaps that was not as obvious a statement as I had imagined.

The issue is to prevent loads from being uncontrolled, not just to bypass motors.

I guess this means that a rig would have more safeties than it would motor points.

I appreciate the points Nick rightly makes about driving, promoters and the rest, but to accept it as 'the way it will stay' is surely what a lot of us, certainly the PSA, ABTT and PLASA want to get away from.

I only wish these organizations had managed to convince the Inland Revenue that the old system of self employment was not making us all millionaires at the expense of the Exchequer.

[Nick Evans]

<< sits down to read LOLER 98 ACOP >>