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Affordable truss suspension


cedd

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Hi all

Local small ish theatre venue have, on the advice of an independent survey, removed their lighting bars and over stage rigging. It was a hotch potch of old bars (some cast iron), blue nylon rope and all manner of dodginess. It had to go.

 

Now they are in a position though where they need to get at least some form of safe suspension (LX and a few cloths etc.) back.

 

One option that is looking like a strong contender over the stage is a truss structure with a pair of legs behind the pros arch and the upstage edge bolted in to the ludicrously thick end wall of the building. We have a plan to cut through the stage floor behind the pros to access the hall floor underneath, which I'm confident a structural engineer will sign off as capable of supporting the required load of the front legs, as will the upstage wall.

 

Front of house will be a little more tricky. It's an apex roof but the top of the triangle is chopped off by the ceiling (you can see the first 2 or 3m of the apex, then it continues above this Ceiling. Ceiling height is 10m and whilst there is limited access to above it, it'd need boarding properly to be regularly accessed (not impossible but also not ideal). There are plenty of decent sized timbers in the roof structure that again I'm sure a structural engineer will sign off suspension from. We don't need more than 250kg per truss (iwb's aren't an option given the number of suspension points required) and we could probably cope with 125kg per truss if required. The truss probably won't need bringing in that many times, but I don't think we can cope with it being completely static. They'd also like the option to remove it completely when the room isn't being used for theatre.

 

Initial plan was a pair of cheap electric hoists in the roof (I've found some that are double braked and designed for the construction industry) which would take the truss in and out, then use steels to suspend properly. We'd have to come up with some sort of safe working practice to ensure the steels were always reattached, but procedurally I think it's doable. The problem is this puts the hoists up in the roof as they're not designed to work inverted. As I've said, access isn't ideal and the headroom for the hoists is limited. They are designed to mount to a scaffold pole, and the roof continues to thr apex above the ceiling. Getting them far enough apart to reduce the cantilever on the truss means the joists in question are quite close to the ceiling - the hoist would end up on some sort of bracket arrangement alongside the joist rather than hanging underneath it. Again I think given the size of the timbers, a structural engineer would probably be ok with this despite the twisting moment, given the relatively low load.

 

What would be ideal though would be a hoist on the truss operating inverted, going up to a simple eye on the underside of the beam. We could make a small trapdoor alongside the point to allow the chain to be roped up and down when removal is required.

The problem we have though is simple - if you're after a hoist capable of operating inverted, you seem to be looking at very expensive (for them) entertainment hoists. What would be ideal would be a pair of manual chain hoists (to keep cost down and given the low number of times this thing needs flying) capable of operating inverted and capable of holding the load without need for a secondary suspension. Once the bar is out we could just nip up a set of zarges and put the chain in to a bag.

I can't find such a beastie though. Can anyone think of one? Or of a cheaper electric hoist that could operate inverted. We could still do a steel to properly suspend the bar if required, but if something happens to exist that doesn't need it, it'd be perfect.

 

Thanks all

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It kinda depends on budget doesn't it. Can you give any indication of what kind of money you're talking?

 

For the stage, your idea sounds relatively sensible. Truss structure into the floor at one end and into the wall at the other with some Hilti anchors, you'll be fine (subject to competent contractor etc etc usual)

 

For the FOH...

 

Well option 1, to answer your question... the Yale 360 chain hoist can be operated inverted. https://www.liftings...-hoist-209.html . That said, they're unlikely to meet the appropriate standard to be 'approved' for suspension over the audience without a secondary.

But is that a huge issue? If you're going up to pack the chain into a bag anyway, you could leave a pair of steels or chains hanging out of the roof with a shackle or latch hook on the end, to go into an eyebolt bracket on the truss. It's barely any extra work.

 

For electric chain hoists... you kinda get what you pay for. I'd personally steer clear of the scaffold type, they're designed for short term suspension and local control (ie use of a pendant stood next to it, not from a motor controller).

If you could opt for a D8+ or BS-7906 Cat A (now superseded by EN17206) compliant electric chain hoist, you could suspend the load on the motors all the time and not need access to the roof for removing steels etc - so it's a good thing for work at height etc.

 

Another option could be winches. With diverters in the roof, you could run the winch lines through the roof space back to a sensible place for the winch to live. Electric winch - that could be in the roof space, hand winch could possibly be on stage.

You could go with an electric winch or a manual winch could be a tad cheaper, particularly as you wouldn't need to budget for a controller (winch controllers tend to be dearer than chain hoist controllers). Some manual winches permit use of a cordless drill to turn rather than a handle.

On the cost front, the perk of winches is that you only need one machine, irrespective of how many lifting points. The downside is that winches - even hand winches - can be rather costly (1 winch + rope + control is likely to be similar cost to 2x Electric chain hoist + control, but cheaper than 4 hoists + control, if you'd be happy with always having to bring both bars in at once).

 

As a question for you - what's your plan regarding cable management FOH? If you want to get fancy you could do an IGUS energy chain, or perhaps flip-flop cable trays from the roof, a lot neater than a swag of cable. Otherwise you may also need a plan to hide your excess cable once you've raised the truss.

With electric chain hoists, you could potentially do chain runners from the roof.

Edited by dje
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Thank you both.

Budget is undecided, but not much. They are applying for a bounce back loan, which needs to cover a rewire and getting the stage usable. Rewire is domestic stuff in dressing rooms and downstairs function rooms. Will also include heavy (ish!) power up to the stage (cable already exists, just needs terminating in a board). I envisage 10k to be available to reinstate SOME rigging upstairs. The front of house truss (or pair of depending on cost) is probably the easiest/cheapest bit as, once the points are in, it's just bolt together some truss and fly it out.

 

The freestanding (ish) truss is the most expensive bit, and will probably come later. It prevents having to deal with the troublesome roof structure above the stage though. Once you're upstage of the pros the ceiling vanishes and the roof just goes straight up to the apex. The joists we'd be attaching to above the house continue through to above the stage, but they are too close together to fly a truss/bar/whatever of a useful length on stage. Out front of house the trusses will be 6m long, with points 4m apart (spacing of the joists). I'm happy with a 1m cantilever given it's replicated on both ends and will only be LX stuff. I may stick a "no more than xyz" on the cantilever, but don't think we're anywhere near making the bar unstable (calcs to be done!).

Above the stage though we need nearer 10m trusses/bars/whatever as the pros is 8m wide and if a show uses a few cloths we'll need stacking space (wipe tracks - no height for full flying). Putting a few cloths on the end of a 3m cantilever (given 4m apart pick up points) is starting to sound far more silly!

A freestanding mother truss with roped bars flown from it fulfills all their needs (they're never going to be able to fly higher than pros height as the roof apex begins almost straight away).

 

Cable routes are currently flexible. As much of the LX install is reasonably temporary it'll be socapexes to each truss. We have a route through the roof but won't go that way unless the flying method means we have to make it safe to get up there often. Instead we're considering some form of trough running down the side of the house, suitably decorated to not stick out like a sore thumb. This would be at roughly bar height. It'd be a trip up zarges to let out enough soca to drop a bar in, and then the reverse once they're out.

 

Those Yale hoists look ideal. A hanging steel will work well and I may look at some form of parachute cord tie back arrangement, so when the truss isn't in the venue they can be pulled outwards to follow the roof line so they're out of sight.

 

I'd probably construct some form of shroud to go around the hoists that attached to the top of the truss (an open topped/bottomed box) so they weren't so obviously bright yellow!

 

An alternative we'd considered to fixing points to the existing joists was to lay a pair of 40cm square trusses up in the loft space. A pair of 15m long trusses laid across the 5m spaced roof structure tie beams would get from the upstage wall (resin bolted in), across the stage and then through above the ceiling above the house. If a structural engineer would sign off the load per bay then the truss spec could be used to allow fixing points wherever we need, including future plans we don't yet know of. It'd just need a neat trapdoor style hole cutting in the ceiling.

The tie beams won't be perfect so the truss would need shimming to ensure it was in contact with all of them nicely. Is this something that is done often? I consider myself competent in the basics of theatre rigging, but establishing the points is very different (and won't be completed by me). It's helpful though to understand what we're asking for and in deciding which avenues to pursue when writing a spec and speaking with contractors.

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Taking kit out usually leads to damaged kit and damaged venue, plus something always goes missing. Plus (again) kit kept high looks small but gets bigger as it get's closer to the ground and it's the big stuff that needs a space to live in.

 

The stage in my old school had a dropped ceiling between the (predictable) three bars and roller blind like horizontal cloth shutters to cover the bars! With the lanterns flown the screens didn't close so they never got pulled -ever!

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Disclaimer - all advice below is given 'in principle' with the usual caveat that any engineering decisions should be made on the professional advice of a suitably qualified engineer.

The freestanding (ish) truss is the most expensive bit, and will probably come later. It prevents having to deal with the troublesome roof structure above the stage though. Once you're upstage of the pros the ceiling vanishes and the roof just goes straight up to the apex. The joists we'd be attaching to above the house continue through to above the stage, but they are too close together to fly a truss/bar/whatever of a useful length on stage. Out front of house the trusses will be 6m long, with points 4m apart (spacing of the joists). I'm happy with a 1m cantilever given it's replicated on both ends and will only be LX stuff. I may stick a "no more than xyz" on the cantilever, but don't think we're anywhere near making the bar unstable (calcs to be done!).

Above the stage though we need nearer 10m trusses/bars/whatever as the pros is 8m wide and if a show uses a few cloths we'll need stacking space (wipe tracks - no height for full flying). Putting a few cloths on the end of a 3m cantilever (given 4m apart pick up points) is starting to sound far more silly!

A freestanding mother truss with roped bars flown from it fulfills all their needs (they're never going to be able to fly higher than pros height as the roof apex begins almost straight away).

 

Well the good news is that your 4m spacing in a 6m truss is more or less textbook (providing the truss loading is uniformly distributed) so don't worry about your FOH trusses too much, it sounds like those beams are already in a good place.

 

In principle the freestanding ground support makes absolute sense - especially if at the U/S end you can utilise the wall for support rather than needing truss towers.

BUT - of course you don't want to be hanging a 10m bar / truss from the far ends. For a 10m bar on 2 points, I'd recommend a point spacing of approx 6.5 to 7m. So with an 8m pros, that means either (a) having your truss towers in view (which I presume you don't want!!) or having to put some additional truss in this ground support to support your (presumably) sub-hung bars.

 

I wouldn't say using the roof joists is out of the question - you could attach a truss directly to the beams to take the weight, and sub-hang your bar below.

If the beams are good for the weight, then your truss* (see below) would likely be fine providing that it itself is suitably rated for the cantilever load and the deflection is suitable for your purposes.

I say truss*, because it may be that you can do it with steel or aluminium section fabricated into a custom 'rigging beam' by a suitable engineering company.

 

Cable routes are currently flexible. As much of the LX install is reasonably temporary it'll be socapexes to each truss. We have a route through the roof but won't go that way unless the flying method means we have to make it safe to get up there often. Instead we're considering some form of trough running down the side of the house, suitably decorated to not stick out like a sore thumb. This would be at roughly bar height. It'd be a trip up zarges to let out enough soca to drop a bar in, and then the reverse once they're out.

 

Sounds reasonable. Alternatively, you could drop socas down from the same hole as the rigging point and secondary, which stay at that set length... then when lowering the truss in, add extensions in which can be removed once the truss is back at height. Might be neater, and you can share one set of soca extensions between all your trusses to save some cost.

 

 

I'd probably construct some form of shroud to go around the hoists that attached to the top of the truss (an open topped/bottomed box) so they weren't so obviously bright yellow!

 

Alternatively, how about a fabric 'jacket' with a velcro or zip enclosure which could be applied to the hoist once fixed in position, and removed before lowering? Then there's no need to worry about anything getting caught in the mechanism.

Painting them isn't completely out of the question (as long as you keep the paint away from the moving and load-bearing parts), but you may want to check with the manufacturer for explicit written permission (bum covering).

 

An alternative we'd considered to fixing points to the existing joists was to lay a pair of 40cm square trusses up in the loft space. A pair of 15m long trusses laid across the 5m spaced roof structure tie beams would get from the upstage wall (resin bolted in), across the stage and then through above the ceiling above the house. If a structural engineer would sign off the load per bay then the truss spec could be used to allow fixing points wherever we need, including future plans we don't yet know of. It'd just need a neat trapdoor style hole cutting in the ceiling.

The tie beams won't be perfect so the truss would need shimming to ensure it was in contact with all of them nicely. Is this something that is done often? I consider myself competent in the basics of theatre rigging, but establishing the points is very different (and won't be completed by me). It's helpful though to understand what we're asking for and in deciding which avenues to pursue when writing a spec and speaking with contractors.

 

To confirm, are you suggesting 2 beams running the full length of the room from the US wall, to the far rear-of-auditorium wall (or, at least as far as the furthest D/S points would need to be)?

If yes, then IMO this is a strong idea. You could space them at the ideal spacing (for your stage trusses I'd say that's circa 6.5-7m). For your FOH bars, you could still go to the roof beams as previously discussed, or alternatively you could lay a truss spreader over these 2 up-downstage beams.

To answer your question... yes, laying trusses atop of roof beams is relatively common practice. Often referred to as 'spreaders' or the Americans say 'spanners' (because 'spanners' are 'wrenches' blink.gif )

Shimming them is indeed the responsible thing to do. You'll likely secure the truss at each point where it crosses a roof beam anyway so the shim can be inserted and the truss secured down to the shim so there's no movement.

I once did an install with a 50m long rolling beam track secured below the beams in the roof. The installer didn't shim or adjust them for variance in the exact beam heights. When the show came out several years later, the trusses were permanently warped. huh.gif

 

 

This is all something I could help you with (professionally) if you want to drop me a PM.

 

Taking kit out usually leads to damaged kit and damaged venue, plus something always goes missing.

 

Whilst in a slightly different context... touring shows manage to take kit out of venues night after night and put it all into new venues without losing or damaging any kit or the venue...

 

So de-rigging stuff doesn't have to mean damage or loss, does it? For me it's a case of designing the install to be demountable - designing it almost like a touring system in effect.

Plenty of venues have done this successfully, with kit kept in cases / transport dollies etc, cable looms built and labelled, etc etc - as you would for a tour.

Just needs a bit of thinking about, up front.

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Taking kit out usually leads to damaged kit and damaged venue, plus something always goes missing. Plus (again) kit kept high looks small but gets bigger as it get's closer to the ground and it's the big stuff that needs a space to live in.

 

Whilst in a slightly different context... touring shows manage to take kit out of venues night after night and put it all into new venues without losing or damaging any kit or the venue...

 

So de-rigging stuff doesn't have to mean damage or loss, does it?

I think I know where JM is comng from.I find that in schools and probably more so in AmDram the transportation/storage facilities are not the rather lovely flight cases used by touring companies.

In schools the storage is so often shared with sports kit, music department, etc. I've even seen stage lights in the grounds maintenance hut amoungst the lawn mowers forks, brooms & line marking machines etc. So often plugs get pinched, hook clamps take up too much space and get removed and so on.

By the time kit is used again the teacher responsable for putting it away has moved on to another job and no one has a clue that he found space in the boiler room and no one thinks to ask the caretaker [or whoever has responsibility for the boilers] who keeps tripping over them.

The box of colour frames and gels never does resurface etc.

 

AmDram, at the end of a show there is so often a discussion of who can take what home and yes I've known their dozen lights going off to six different cars. a year later when they put on their next show the denials come in but miraculously a couple of fitting resurface some months later when the Christmas decorations are moved in the loft. The original extention leads purchased by the group are long forgotten when they have been used for the new position of the HiFi etc

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I'd been in a job at a school for 2 months before I found the box of mac600s hiding in the disabled loo.

2 months...

 

Doesn't count.

 

My school had an old building [big private house with multiple extentions] and annex some mile+ away. My intake was the first to use the big new building beside the old house and our fantastic new hall and stage.

I did drama - but avoided being on stage - from 2nd to 5th year [years 8, 9, 10, 11] and despite repeatedly gaining access to all sorts of storage places for 3 years the stash of patt45's, 23's and 4 of these: https://www.ebay.co....m4383.l4275.c10 complete with stands, which had been moved from the annex and just piled up in an attic space along with a load of other unrelated stuff had gone unseen. There were also some 500/1000W dimmers from the old predecessor to the junior 8.

 

The lighting bars [grey painted scaff with hanging clamps and patt 23's & 123's had been stashed in the boiler room and found quite early.

Edited by sunray
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I think we're in a pretty good place from a kit removal point of view. There are 2 or 3 volunteers who are pretty savvy and with pro theatre backgrounds. We're hopeful in time (Covid aside!) the venue will become profitable enough to support the wage of one employed technical staff member at least. Up until now it has been a venue run by an am dram society (owned by the council but with a long term lease that pretty much wants no involvement with the interior of the building). Aside from their own shows it has had the odd dance school show and then just been a home for line dancing and Zumba classes. It's a good looking space (once the decor gets sorted) and has held a wedding recently. This is a market they're keen to pursue. The decor is very "vintage" and it's a theme they are wanting to keep.

Eventual goal is for it to have the feel of an old theatre (clam shell footlights etc.). In this mode the trusses would seem out of place, and we feel we can get suitable lighting cover from the kit hidden by the prosc and some period luminaires that are awaiting an overhaul (possible led conversion within the original shell).

There would be a wedding season so it's and out's wouldn't be too often, and we may even have the space under the stage front to leave the truss assembled and rigged if we can create a trolley for it.

 

The on stage truss plan includes an upstage and downstage truss running across the stage, with a central truss running to front to back (with the same at the stage left and right ends) so we have 3 good pick up points. These will pick up ladder truss which will either be rigged as LX or will carry curtain tracks.

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I think I know where JM is comng from.I find that in schools and probably more so in AmDram the transportation/storage facilities are not the rather lovely flight cases used by touring companies.

In schools the storage is so often shared with sports kit, music department, etc. I've even seen stage lights in the grounds maintenance hut amoungst the lawn mowers forks, brooms & line marking machines etc. So often plugs get pinched, hook clamps take up too much space and get removed and so on.

By the time kit is used again the teacher responsable for putting it away has moved on to another job and no one has a clue that he found space in the boiler room and no one thinks to ask the caretaker [or whoever has responsibility for the boilers] who keeps tripping over them.

The box of colour frames and gels never does resurface etc.

 

 

I do understand where JM was coming from too - and you - but firstly, cedd made no mention of this being a school or AmDram society; and secondly, my whole point was that if you build the install like you'd prep a tour (whatever that entails for your needs) then removing and re-installing shouldn't be an issue.

Kit doesn't have to be in flight cases to be safe and organised. There's all sorts of options for carts, stillages, boxes, meat racks or whatever.

The main point is that it's thought about, that's all. Where do we store it (without needing to remove hook clamps)? How do we keep it safe? How do we ensure things are plugged back in the same place?

You don't need to admit defeat and leave kit in the air, just because some other people couldn't organise themselves well enough (whether their own poor drills, or poor decisions further up etc) to keep their gear in order when it's in storage.

It's not just touring either - a lot of corporate event venues keep their own equipment in stock, but the venues need to be available without kit, too. It just takes some thought and planning. Theatres too, need to remove things when receiving tours. All sorts.

 

Eventual goal is for it to have the feel of an old theatre (clam shell footlights etc.). In this mode the trusses would seem out of place, and we feel we can get suitable lighting cover from the kit hidden by the prosc and some period luminaires that are awaiting an overhaul (possible led conversion within the original shell).

There would be a wedding season so it's and out's wouldn't be too often, and we may even have the space under the stage front to leave the truss assembled and rigged if we can create a trolley for it.

 

I'd suggest that as a good plan. At 6m, fabricating a trolley that one or even both trusses could land on - with fixtures remaining rigged (depending on how high your stage is) should be doable! A nice neat solution right there.

 

As a thought for you - when it comes to 'hiding' the safety steels we talked about, one thing that has worked in other places is to hang chandeliers on the end of them. If you leave the short soca tail in as I said about, you can use one circuit of that to run the chandelier, too. That might fit nicely with your aesthetic.

 

The on stage truss plan includes an upstage and downstage truss running across the stage, with a central truss running to front to back (with the same at the stage left and right ends) so we have 3 good pick up points. These will pick up ladder truss which will either be rigged as LX or will carry curtain tracks.

 

That seems reasonable, but it's quite a lot of truss. If you could do the two long trusses running the full length of the venue (as per the previous post), then providing the roof beams are good for the load, this could well give you all the over-stage support you need for a much lower cost.

It seems silly to build a freestanding ground support if the building has a load bearing roof, no?

Edited by dje
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I think I know where JM is comng from.I find that in schools and probably more so in AmDram the transportation/storage facilities are not the rather lovely flight cases used by touring companies.

In schools the storage is so often shared with sports kit, music department, etc. I've even seen stage lights in the grounds maintenance hut amoungst the lawn mowers forks, brooms & line marking machines etc. So often plugs get pinched, hook clamps take up too much space and get removed and so on.

By the time kit is used again the teacher responsable for putting it away has moved on to another job and no one has a clue that he found space in the boiler room and no one thinks to ask the caretaker [or whoever has responsibility for the boilers] who keeps tripping over them.

The box of colour frames and gels never does resurface etc.

 

 

I do understand where JM was coming from too - and you - but firstly, cedd made no mention of this being a school or AmDram society; and secondly, my whole point was that if you build the install like you'd prep a tour (whatever that entails for your needs) then removing and re-installing shouldn't be an issue.

Kit doesn't have to be in flight cases to be safe and organised. There's all sorts of options for carts, stillages, boxes, meat racks or whatever.

The main point is that it's thought about, that's all. Where do we store it (without needing to remove hook clamps)? How do we keep it safe? How do we ensure things are plugged back in the same place?

You don't need to admit defeat and leave kit in the air, just because some other people couldn't organise themselves well enough (whether their own poor drills, or poor decisions further up etc) to keep their gear in order when it's in storage.

It's not just touring either - a lot of corporate event venues keep their own equipment in stock, but the venues need to be available without kit, too. It just takes some thought and planning. Theatres too, need to remove things when receiving tours. All sorts.

I'm there with every word you say, I was just trying to indicate some of my experiences particularly in shared spaces or where the stage plays a minor role in a venue.

I'm mostly a public address guy, but dabble in other areas, and very little of my kit is racked or even stored/transported in cases but as a 'one man band' I don't have the above problems

I do agree that eaving kit rigged is short sighted if it's not in regular use.

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  • 1 month later...

Out this morning went past the church hall where an AmDram has kit stored. Theoretically the whole of the stage belongs to them along with the cupboards built in one wing. When I drove past a few nights ago I saw stage lights were in use which is theoretically not possible as their DMX desk is locked away and not available for general use and certainly not part of 'hall hire'.

 

The kit consists of 2x4way packs [with IEC sockets], 4xprofiles and 4xfresnels plus 4xLED PAR. The 'stage lighting supply consists of 3x 16A radial feeding 3x13A socket each. from a dedicated CU fed by a 63A mcb. When not in use we switch off the 63A, and all devices in the CU.

 

 

As I was passing I thought I'd pop in and have a look. All 8 of the IEC plugs were plugged into 13A/IEC leads in the 13A sockets [sockets switched off] with all MCB's on.

However the point I'm adding is our LOCKED storage areas under the stage have been compromised and rearranged to make space for others items; one section is childrens toys so I assume it's the nursery/playschool and the other is boxes of clothes.

The result is our carefully sorted and stacked kit in the storage provided and maintained by the group has been mixed up and crammed in fewer storage boxes. Additionally extention leads which were in storage are currently being used for Christmas decorations.

These are the sort of problems I was referring to previously in mixed useage venues.

 

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