Vertical Trussing

[Sam_Lowers]

Hi All.

 

Just looking for some explanations.

 

I have seen so many rigs done by other designers where they have rigged moving lights on different types of vertical trussing.

 

What am wondering is how you rig two types:

 

1) Vertical Truss - Rigged from deck level upwards:

How would you rig a piece of truss, e.g. 2m high, from the floor and then put a mover on top of it?

Would the truss need to have outriggers on it to make it into some kind of tripod?

Also how does the trussing cope with a fast mover? Are the bases of the fixture ratchet strapped onto it in some way?

 

2) Vertical Truss - Rigged as drop down booms from a main structure:

Obviously the trussing would be made with drop down sections from the main rig but would placing movers on one side of it not cause stress on the joining pins at the top? also how would a mover be fitted directly in the centre of the base of the truss? Would it need some kind of baseplate?

Is this very common or is it more common to use drop down T-Bers like they rig movers on in TV Studios?

 

Lastly:

Are there only certain manufactures of trussing who make truss for these jobs or is it universal thing?

 

It would be nice to know how people do this!

 

Cheers

Sam

[johnnypalmer]

Depends on your truss, but......

 

With our large QX40 40cm box truss we have large (1800mm across) base plates. I happily use these at 6m and climb to the top.

 

With light truss like trilite, get steel base plates made with spogots.

 

As for rigging it from a truss - two swivel couplers joining the two with some safeties.

 

Look on my website www.sxsevents.co.uk and you will find loads of photos of this being done.

 

You need to bear in mind that you are placing a large point-force on the cords, which they are typically not designed for.

 

I think most people would agree that this is a speak with the maker scenario, and if in doubt check with a structural engineer.

[mac.calder]

This is almost a "Don't know, then you shouldn't be doing it" type of thing (as with most things involving truss), but it really is quite simple in principal. Many manufacturers make truss plates that attach to the bottom of the mover and the top of the truss. The truss is bolted to a "Barbecue" plate (maybe that is aussy slang, but essentially a heavy metal base), and Bob's your Uncle.

[Sam_Lowers]

The truss is bolted to a "Barbecue" plate (maybe that is aussy slang, but essentially a heavy metal base)

I had a suspician that it would be like this but is that really strong enough to hold it? Obviously it is wide and heavy but do you need to bolt it down at all because of if its on a stage would the vibrations not effect it?

 

Not to worry I am not planning on doing it but was just wondering!

 

Sam

[Ken Coker]

Chapter 9 of Peter Hind's book,(find it here ETBooks) will give you some insight into the issues of towers/vertical trusses. The rest of the book you might find useful too.

 

KC

[Seano]

1) Vertical Truss - Rigged from deck level upwards:

How would you rig a piece of truss, e.g. 2m high, from the floor and then put a mover on top of it?

As a general rule, rigging of lights takes place at ground level wherever possible. In this case, most likely build it flat and walk it up with 2 or 3 people.

 

Would the truss need to have outriggers on it to make it into some kind of tripod?

Maybe, or - much more likely - a suitable baseplate with or without additional ballast. It depends.

 

Also how does the trussing cope with a fast mover? Are the bases of the fixture ratchet strapped onto it in some way?

Usually something like that, yep.

 

2) Vertical Truss - Rigged as drop down booms from a main structure:

Obviously the trussing would be made with drop down sections from the main rig but would placing movers on one side of it not cause stress on the joining pins at the top?

Yep. All 4 (or three) chords of the truss would most likely be under tension. When a truss is flown horizontally the bottom chords are mostly under tension and the top chords in compression. Truss manufacturers literature always includes information about maximum span, max CPL and UDL for when its flown horizontally, you don't often see explicit figures for hanging it vertically - so what you have to do is look at the specs, work out what kind of loads you'll be putting on it and decide whether a) the loading is relatively trivial (ie: you're imposing a much lower tensile load than bits of the truss would experience in 'normal' use), b) to consult the manufacturer or c) to get a bigger/stronger truss so that a applies.

 

also how would a mover be fitted directly in the centre of the base of the truss? Would it need some kind of baseplate?

Maybe, or a scaff arrangement of some description.

 

Is this very common or is it more common to use drop down T-Bers like they rig movers on in TV Studios?

Both are common. The choice is aesthetic rather than practical - ie: it depends on the look the LD is trying to create.

 

Are there only certain manufactures of trussing who make truss for these jobs or is it universal thing?

It would be nice to know how people do this!

I've never heard of a truss designed specifically to be dangled vertically (in tension). Most truss designed to be flown has diagonal bracing in only one plane (ie: the truss is stiffened by additional bracing only in the up/down direction) - when truss is stood on end (ie: its vertical and under compression), unless the loading is pretty trivial, it needs to be braced in both planes to prevent it from buckling. This is generally known as 'tower' truss.

 

 

The truss is bolted to a "Barbecue" plate (maybe that is aussy slang, but essentially a heavy metal base)

I had a suspician that it would be like this but is that really strong enough to hold it?

 

Its a fairly simple calculation, if you're interested, why not do it as an exercise. What you need to do is look at moments, and don't forget that it isn't the weight that counts, its the component of it perpendicular to a line between the edge of the baseplate and the CofG of the whole shebang. (Assuming that both baseplate and structure are rigid.) Its well within A level maths/physics, no idea where it'd pitch up between GCSE and rocket science though, soz, its been a very long time since I had anything to do with the education system.

 

Vibration and the nodding of a nodding bucket are probably a side issue (unless the nodding bucket in question is a monster like a synchrolite or a biglite) - the truss has to be able to withstand someone bumping into it without falling over, which is probably going to be a much greater destabilising force than anything resulting from the waggling of a wagglie.

 

Peter Hind's book

Second that. A bit technical here and there, maybe, but a very good read.

 

As for rigging it from a truss - two swivel couplers joining the two with some safeties.

 

Oh, and by the way..

Corner blocks are a more common solution in concert/conference industies. Neater & stronger.

[Simon Lewis]

With our large QX40 40cm box truss we have large (1800mm across) base plates. I happily use these at 6m and climb to the top.

 

Erm, just curious.... are you climbing to 6m on a vertical truss fixed with just a base plate (albeit quite a large one?). Or is the truss fixed to something else as well?