Moving Truss and Staging during a show

[TobyF]

Hello.

 

I am currently doing a project at University where I have to do a ten minuet show controlled entirely by show controlled software. This is done in relatively small groups and I am in charge of rigging.

 

Our show is a "Stage disaster" scenario. We have plenty of ideas and most we know how to achieve. However, we want to do sudden truss movement such as drops and have part of the stage collapse to allow the drum kit slide off. The truss doesn't need to drop far, just enough to make people jump. It will not have any working equipment on it.

 

It is a bit like the automated theme park rides.

 

I was hoping someone may have experience in this before and have any suggestions. We want to know if dropping the truss safely is possible and what safeties to employ. I have had a look for equipment that can do this such as kabuki drops but they seem more appropriate for drape drops.

 

We need it to be remotely controllable and have dead man's switch capabilities, even if we have to make our own. If it can come to a controlled stop, that would also be nice. It also needs to be resettable in a reasonable amount of time.

 

We do have a small budget of £200-£300 max.

 

 

Any suggestions will be very helpful even if it's just pointing me in the right direction.

 

Thank you.

[Andrew C]

Have you considered the effects of a dynamic load on the truss, and the structure you are supporting it from? You may need to find some scrap truss!

[jonathanhill]

This sort of thing would need specialist knowledge and equipment such as an automation piece or motors controlled by a Kinesys type system. Calculations on the dynamic forces will have to be carried out and referenced to the loads that the supporting structure is capable of withstanding. Generally this is backed up with the use of load-cells and other devices during the production period.

[Ynot]

And might JUST cost a tad more than the OP's budget of £300 max...

;)

[trussmonkey]

a kinesys system wouldnt be the best choice for this you would need winches.

 

BUT....

 

any automation system would be far in excess of your total budget !!

[Chris Beesley]

Could you not do the old trick of one truss in the dark one lit, sudden loud SFX and change lighting states to highlight one that now appears to have moved? The drum kit could be on some form of low level truck.

[smalljoshua]

Could you not just ask Kit or Simon for advice on this? I'm sure they'll be able to help you.

 

Josh

[TobyF]

To just clarify. We have all the rest of the gear. The budget is just for the effect.

 

Our intial idea is to have a back truss held in place with some kind of drop, plus sets of steels and load arresters that would stop it after a 2m drop, plus another steel that would act as a secondary suspension after the drop. Naturally we would take dynamic loads on the truss, points, etc. into account.

 

The post was more to provide alternatives.

[paulears]

They could ask the staff - but wouldn't that rather defeat the point. However, as the staff will read the ideas here, then of course it's not your own idea anyway .....

 

If I had to to do, and ignoring all the sensible caveats about loading and stuff like that, I'd be tempted to try to design in ways of making the truss fall quickly enough to look good, but not quick enough to damage.

 

I think I'd be looking at kabuki style drop release at one end, but also having a cable and pulley system that with a suitable weight on the other end would prevent it simply dropping, the downwards speed would ramp up, and then maybe a bottom line on the counterweight with some kind of shock absorber/damper to stop the travel gradually. I'm visualising a car style damper that would be manually compressed, and then as the counterweight line becomes taut, the damper handles the last foot, or so, before the limit is reached. I think I could come up with something that would look good, but be safe, using standard truss. In a counterweight house, maybe you could rig a length of truss from two bars - well within capacity and then simply bring one in on cue. One end up, one end coming down. Can't see a snag with that off the top of my head. There'd be some lateral movement, but it would be manually controllable? Automating this kind of thing would be trickier/more expensive - but the original idea might be worth experimenting with.

[J Pearce]

Does the truss have to be real?

 

Pipe lagging foam sprayed silver with some light dowel inside to hold it straight? Would then be light enough for a kabuki drop system.

 

As an aside, the big bit of this project is your show control setup, don't underestimate how fiddly and fault prone it is. Dry run and test and find all the fault conditions of your system.

[dbuckley]

It is a bit like the automated theme park rides.

The thing about theme park rides is the degree to which everything possible is fake, and the idea for using fake truss is excellent, if possible because it gets rid of most of the weight.

 

In a theme park ride they are not going to drop a heavy object and have it come to a stop unless there is no possible way to avoid it, as the shock loadings get silly and thus expensive. If you can (a) make your dropped thing light(er) in weight, and (b) if it needs to stop (as opposed to just swing around) then bring it to a controlled stop rather than a sudden stop.

 

The remarkable thing about theme park technology isn't the show or the reproducibility, its the reliability; the show runs many times a day for an extended period, and has to work every time. If you're doing a one-off then that degree of reliability, or the ability for an effect to work time and time and time again are not necessary, and you can fudge around some of the issues.

[RobA]

Hi all, I'm working with the OP on this event.

 

Thanks for all the suggestions and advice. Unfortunately fake truss is not a viable option since we're planning on rigging fixtures on it. Before anyone panics these will be scrap fixtures, stripped of fittings, lamps, optics, etc. and they'll be on highly over-rated half couples and safeties. They will probably be fitted with microdets or some other small pyro, but that's for another thread... They key area where we could use advice and suggestions is on arresting the fall at a sensible rate - probably at somewhere around 40ms^-2, since that would keep us under 25% or the rating of the points we're using (I think, we will triple-check the maths long before we even think about a low altitude test). Clearly we need to do our own research, but suggestions and recommendations are very welcome (on any aspect of this), and anything we use will be credited.

[Seano]

I think I'd be looking at kabuki style drop release at one end

I think Paul is on the right track here, but I'd be looking at something less complicated.

 

Would then be light enough for a kabuki drop system.

A 3m length of 4-chord Astralite (an example of a lightweight real truss) weighs about 12kgs - already light enough for a kabuki drop type system.

 

and the idea for using fake truss is excellent

<some snippage> the ability for an effect to work time and time and time again are not necessary

Quite agree, but there's fake truss and fake truss. You're still faking it if you use a lighter duty truss than you would use for a real lighting truss, and attempting to manufacture your own floaty light pretend truss could be counterproductive if it isn't strong enough to hold together. You don't want even bits of dowelling falling out of the sky if that isn't part of the plan - dropping stuff, even wispy insubstantial stuff, that you don't intend to drop is bad mmmmkay. ;)

 

Regarding the latter - Pauls suggestion of a mechanical shock absorber would be the kind of thing that might work repeatedly for a long time. The stretch of a stretchy rope might be an effective shock absorber for a more limited working life of say about: (umpteen rehearsals + show) x safety factor.

 

My not-very-carefully-thought-out suggestion would be this (I'm assuming a space with a theatre grid, where a usable rigging point/spot line is available more on less anywhere):

 

Several short lengths of truss rather than a single longer truss which, when dropped, simulate a longer truss being broken into pieces.

Say 2-3m section of something like Astralite - real truss, very light duty but definitely strong enough to support its own weight under deceleration. Again taking Astralite4 as an example, a 3m length weighs 12kg and has a max rated CPL of 600kg - suggests to me you're unlikely to damage it at less than 50g deceleration (which is *huge*).

 

Each truss hanging on two points. At one end a dead-hang on a steel drift, on the other a black low stretch rope (ie: an EN1891 abseiling type rope) long enough to let the truss hang down at its 'broken' angle, then shortened with a maillon tied into an alpine butterfly and brought up to a kabuki solenoid to level the truss in its preset position.

 

For ease of resetting, you could divert the rope through a pulley and down to fly-rail or stage floor and rig the solenoid there. (Taking measures to ensure the 'slack' rope can't snag on anything when the truss 'drops'.)

 

Of course you'd be needing to do your own risk assessment, but one advantage of using a shorter length of truss rigged high relative to its length is that you cant hit the ground unless you either drop both ends of it or break the truss itself - lightweight truss is very strong relative to its weight. Having one end of the truss on a dead-hang rather than the kabuki stunt malarky means that can also easily be make very strong relative to the weight of the truss.

 

On each truss I'd prolly be inclined to rig a couple of empty par cans on half-couplers (*not* hook clamps) - its not going to look like a lighting truss with no lights on it after all.

If pyros are 'in' a few robotics or the truss might be very nice to create the impression that there's something 'electrical' going on. (Having one end of the truss 'fixed' gives you an easy route to run a bell-wire in without having to deal with the length of the cable run changing throughout the effect).