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Rigging question
GOAL: Hang light grid of 1.5" pipe for new black box space
Roof/ceiling structure has wooden beams of 4" x 6" dimension to which we want to attach the grid. Current idea is using eyebolts horizontally through beams and chain with shackles from eyebolt to pipe. Grid will not be rigid but that seems ok. Do not want to pierce beams more than needed, do not want to lag vertically up into the beams.
Pipe sections weigh 100 lbs each at most. Each section might hold 4-6 instruments.
Please bestow wisdom, with my thanks.
Tags: rigging
Views: 111
Replies to This Discussion
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Permalink Reply by Michael Mell on -
Spend the money to engage a licensed structural engineer to tell you the safest and most appropriate way to hang the grid.
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Permalink Reply by Barry Martin on -
With all due respect, if I was hiring a structural engineer, why would I be asking for intelligent advice on this forum?
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Permalink Reply by SERGIO FERNANDEZ MARTINEZ on -
Structural Engineer is the best option. . . but if yo can send some photos or drawings . . .may be we can help you. . .
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Permalink Reply by Ted Jones on -
Michael's right. There are things the SE will not do. And there are some things you don't want he or she to do for you. Like design your pipe grid. That part should be left to a theatrical pro in concert with conversation with you, so you get what you want/need.
Most pipe grids are designed for between 20 lb/ft of pipe to 50 lb/ft. This means that all of your parts and pipe spans are designed with the idea that you could have 20 to 50 lb hanging on every one foot of pipe. (Hypothetical: 20' of pipe, design load= 30 lb/ft. 20 x 30= 600 lb) This is where the SE comes in. You tell the SE that your grid will be 46' x 24' with the grid members 4' OC in both directions. You or he/she comes up with 424' of pipe and multiplies that by 30 lb/ft and comes up with 12,720 lb of loading on your roof structure. The SE shakes his/her head and you run off into the trees. The grid alone will weigh about 1,300 to 1,400 lb depending on hanger hardware.
So, you realistically tell the SE to plan on 6,000 lb spread uniformly around the 46 x 24 area. BUT, that any point could be loaded with 500 lb. This where you NEED the SE. The SE can tell you where to anchor, how the anchors should attach to the wood, etc. The SE can also tell you if the structure will take the load.
We generally use rod to support pipe grids so they are more solid than if you hang them with chain or cable. We also tag them to the walls so they don't swing. We also specialize in flat grids as opposed to over/under grids.
There is a lot of other hardware used for pipe grids that are job/consultant/SE/contractor specific. Not to mention the states that require earthquake proof hangers.
Hopefully, the above gives you some ideas of where to go with your grid.
Ted
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Permalink Reply by Erich Friend on -
I'll back Michael, Sergio, and Ted. The combined static weight of the equipment, plus the dynamic weights of scenery, drapery, and technician that slips from the ladder and grabs the grid are all good reasons why a the inclusion of a registered structural engineer is highly recommended. Also, your structural engineer needs to be familiar with the PLASA / ANSI standards for theatrical equipment safety factors, as these are higher than what most structural engineers are used to dealing with.
A note of caution: There is a tendency in some engineering circles to look at the grid as if it was a sprinkler pipe system - don't let them go down that path. The fittings are different, there are live loads involved, and plumbers are not riggers. Use professionals that know their trades.
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Permalink Reply by Barry Martin on
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I'm not flying scenery, or hanging any draperies. I am working with theater professionals who know what they're doing, and what I described is what we have come up with as a plan that makes sense for a low-cost, hands-on installation. Obviously we will use materials that are over-designed for the loads but we are not a wealthy company. We are spending all we have to retrofit this space and get in in shape for revenue generation so we can pay the bills. Excuse me for being brusque, but we went through an earthquake a month ago that has set us back time-wise, and I am determined to meet our deadline anyway. That's why I came here for advice. So far the advice I am seeing is "spend more to hire someone." That isn't what I am looking for.
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Permalink Reply by Ted Jones on
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You asked for opinions, you got them.
Over designed doesn't tell us that someone sat down with a calculator and figured out what the loads may be and how they will be applied to your building structure. It also doesn't tell us what the overhead structure is or how old it is as wood deteriorates with age, what it was designed for.
What you do have is three people that have been willing to help you within the limits that we set for ourselves. We are all still willing to help you with this. But, wood is inconsistent and we all worry when we have to deal with it. Even if you had steel structure, we would still be suggesting an SE first.
BTW- The heaviest loads we deal with are lighting and Eric is correct that when the ladder slips, the person on the ladder becomes part of the load on the pipe.
Any one of us can give you very specific instruction on how to do this, but the information we have is not enough for any of us to be comfortable with it, yet.
We all get the budgetary restrictions you have, but lawsuits due to an injury don't help any of us.
Ted
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