I'm trying to determine the maximum safe working load for the bottom batten of the electrics I hang my lights from . All my rigging was professionally installed so just assume all the suspension hardware is correct . My battens are 1 1/2" schedule 40 pipe hung at 8 foot centers . I'v seen from JRClancy's website that a maximum uniformly distributed load would be 49 lbs. a foot "at 1/3 yield" . I don't understand what 1/3 yield means . Could somebody explain that for me ? Thanks
Batten loading question .
- Thread starterwhaleboat
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shiben
Well-Known Member
The maximum pipe load should be marked near the lineset or in the specifications. I believe 1/3 yield is 1/3 the yield strength of the pipe? However, without looking at your system and your system Specs, you probably should avoid asking on here, because we cant really help. If your linesets were profesionally installed, I would imagine that there will be a listing of how much they can hold pipe and arbor side somewhere near your lock rail, or possibly on the loading bridge. Check those places?
Whatever you found on JR Clancy's website probably does not necessarily apply to your case. Information published there likely refers just to components (i.e. a pipe, a hoist, a _____). You need the overall rating for your system; not for individual components of it. It doesn't matter how many lights you can hang on the pipe before the pipe deflects or fails if the pipe that you're hanging your lights on is suspended with dental floss. It's a weakest link is the greatest strength of the chain sort of thing.
Tell us more about your system and we'll help in the ways that we can, but we can not give a stamp of approval on any weight ratings. What we can do is say that if your system was responsibly installed, counterweight sets should have no limits less than the amount of weight that fits in the arbor. We can also say that if you're hanging conventional fixtures on your electrics, and your electrics happen to be on a winch system, there's really no way you're going to accidentally hang one too many light fixtures. If you start getting into point loads or hanging scenery, that's another story.
There are a few places you might be able to find load ratings. There may be as-built drawings that either are stored somewhere in your facility, or that maybe the architect or general contractor who constructed the building would have rigging drawings for. When our theatre was built a couple years ago, the rigging contractor was required to submit drawings of their systems to the architect, which the architect then included in their drawings -- same thing applied for the audio and video contractors.
If you know who installed the system, you can contact them and ask for them to look in their records for what they installed there. If you don't know who installed it, you can try contacting JR Clancy to see if they keep records of who installed your system. Lastly, you can hire in a rigger to inspect your system head to toe to determine its load ratings (as well as confirm that all systems are healthy and maintained).
Tell us more about your system and we'll help in the ways that we can, but we can not give a stamp of approval on any weight ratings. What we can do is say that if your system was responsibly installed, counterweight sets should have no limits less than the amount of weight that fits in the arbor. We can also say that if you're hanging conventional fixtures on your electrics, and your electrics happen to be on a winch system, there's really no way you're going to accidentally hang one too many light fixtures. If you start getting into point loads or hanging scenery, that's another story.
There are a few places you might be able to find load ratings. There may be as-built drawings that either are stored somewhere in your facility, or that maybe the architect or general contractor who constructed the building would have rigging drawings for. When our theatre was built a couple years ago, the rigging contractor was required to submit drawings of their systems to the architect, which the architect then included in their drawings -- same thing applied for the audio and video contractors.
If you know who installed the system, you can contact them and ask for them to look in their records for what they installed there. If you don't know who installed it, you can try contacting JR Clancy to see if they keep records of who installed your system. Lastly, you can hire in a rigger to inspect your system head to toe to determine its load ratings (as well as confirm that all systems are healthy and maintained).
Ditto Bill. Or is it a counterweight system ?. How many counterweights you can fit on the arbor is usually the limiting factor.
And how many counterweights are bought for the space is the limiting factor for the venue. Don't go borrow more weight from your freinds theatre because you ran out... This is the case at Mrs. Footers venue. We only have enough weight to fill 1/2 the arbors or we "crack the egg".
As always with anything rigging related... just call the installer if you have any questions. Every venue is different. You could have a limited factor anywhere in the system, from cable, to steel, to bolts... the list goes on.
MPowers
Well-Known Member
The original question asked by the OP was,
When a greater force is applied, a material will begin to deform plastically, that is, the material deforms beyond the point where it can completely recover and at least some of the deformation is permanent and non reversible (except by exerting a force equal to the original force and in the opposite direction). Note that when a material has passed the yield point it is also permanently weakened. Straightening out a bent pipe may return it to the original shape and look, but it will not return it to the original strength rating. A good example of this is bending a wire back and forth until it breaks. -
Applying this to the JRC Allowable Batten Loads table we see that for a 1 1/2" pipe supported at 8', there are two load ratings for evenly distributed loads. One is 49# at 1/3 yield and the other (coincidence) is also 49# for 1/360 deflection. What this means is that when the pipe is loaded at 49 lbs/ft, it will bend slightly. 1/360 x 96". This = .266" or about 1/4" that the pipe will deflect under that load. When the load is removed, the pipe will straighten back out. The other figure is 1/3 yield, also at 49#. That means that at 3 times that load, 147 lbs/ft, the pipe will reach it's yield point and permanently bend.
NOW! Just because the pipe will hold a specific load, does NOT mean the system can hold that same load. System loading is determined by a number of factors, wire rope size and number, trim chain size and type, shackle size, loft block rating, counterweight arbor capacity, et. al. You mention that your electric is a double batten. Load capacity is also affected by the method of installing the double batten. Are the pipes joined by welded plates or only by the raceway double pipe hanging brackets? As you can see, we can tell you what A pipe will support, but not what your system will support, unless we come to your theatre and perform a complete rigging inspection.
If your system was recently installed by professional company, there should be a placard or sign posted on a wall nearby stating the load capacities of the line sets, if not, ask them for one. It should be there and it should be prominently displayed.
When materials are subjected to outside force, they first will deform elastically, that is they will flex or bend and when the force is removed, they return to the original shape. The point where the material begins to bend is called the "flex point".
When a greater force is applied, a material will begin to deform plastically, that is, the material deforms beyond the point where it can completely recover and at least some of the deformation is permanent and non reversible (except by exerting a force equal to the original force and in the opposite direction). Note that when a material has passed the yield point it is also permanently weakened. Straightening out a bent pipe may return it to the original shape and look, but it will not return it to the original strength rating. A good example of this is bending a wire back and forth until it breaks. -
Applying this to the JRC Allowable Batten Loads table we see that for a 1 1/2" pipe supported at 8', there are two load ratings for evenly distributed loads. One is 49# at 1/3 yield and the other (coincidence) is also 49# for 1/360 deflection. What this means is that when the pipe is loaded at 49 lbs/ft, it will bend slightly. 1/360 x 96". This = .266" or about 1/4" that the pipe will deflect under that load. When the load is removed, the pipe will straighten back out. The other figure is 1/3 yield, also at 49#. That means that at 3 times that load, 147 lbs/ft, the pipe will reach it's yield point and permanently bend.
NOW! Just because the pipe will hold a specific load, does NOT mean the system can hold that same load. System loading is determined by a number of factors, wire rope size and number, trim chain size and type, shackle size, loft block rating, counterweight arbor capacity, et. al. You mention that your electric is a double batten. Load capacity is also affected by the method of installing the double batten. Are the pipes joined by welded plates or only by the raceway double pipe hanging brackets? As you can see, we can tell you what A pipe will support, but not what your system will support, unless we come to your theatre and perform a complete rigging inspection.
If your system was recently installed by professional company, there should be a placard or sign posted on a wall nearby stating the load capacities of the line sets, if not, ask them for one. It should be there and it should be prominently displayed.
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If you don't know who installed it and there is no limits placard and no inspection record then I'd venture you don't know that it was professionally installed. When was the last time it was professionally inspected? I'd start by getting your system inspected and while they're doing that you can pepper them with questions about your specific system. If there's no placard, find out why and get one installed. Also, keep in mind that cabling weight can far outweigh instruments.
Thanks , Mr.Powers , that is exactly the information I was looking for .
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