First, this isn't a "I have a dumb idea to making things fall on people" thread; just looking for resources to hand to a structural engineer who isn't too familiar with theatre. Not planning to rig anything without his stamp.
Question 1: I've been told some hand-wavy numbers about spacing on lift lines for dead hung battens (some for boring things like legs, some for more exciting things like electrics). I've generally heard 8' is safe and 10' might be ok. Are there any good sources I can point to? (He would like 3'...) Naturally, we plan to use 1-1/2" schedule 40 "gas pipe", with batten splices where appropriate, probably in 20' lengths.
Question 2: Also, this space will involve entirely dead-hung battens, with the possibility for expansion or at least movement later. The only access to the ceiling will be via scaffold (or lift). There are structural beams running SL<->SR above the stage, which our engineer plans to specify attaching to. The only place I've worked that has done this has used unistrut running upstage-downstage, structurally attached to the beams, with the channel facing down, with rated eye bolts mounted on unistrut mounts that are then attached to shackles and finally lift lines. Even though the plan is that you can loosen the eye bolt, slide the mount along to the desired position, and re-tighten it, to my mind the possibility of doing that under load without realizing it or of not tightening it appropriately or in the proper orientation is mind-boggling. (Disclaimer -- this setup also came with an engineer's stamp of approval -- were I the engineer, I shouldn't think I'd stamp it, and I don't recommend you use this setup.) Obviously I've worked plenty of places where I-beams were installed upstage-downstage in the appropriate locations and enormous beam clamps were used for the lift lines, but this appears to be orders of magnitude more expensive, not to mention that we need to subtract the weight of the new beams and hardware from what we'll be allowed to eventually hang. Could anyone point to some good resources that I could give the engineer on this subject? (I'm also secretly hoping there is a product like unistrut where the mounts don't just fall out if you're careless, or a magical circular unistrut mount that's a pain to install but doesn't actually fall out when it's a little loose -- I've seen safer systems for track lighting in office ceilings.) And yes, I understand that the sleepy or the careless shouldn't be doing rigging, and that a sufficiently sleepy or careless person can make anything fall on anyone regardless of design; it's just that the unistrut system seems so questionable that it keeps me up at night, especially since I've definitely worked with reasonably experienced people who are unfamiliar with unistrut and are floored by the fact that the little piece can just come right out -- what about the day I'm not there to tell them? (Unistrut isn't a super-theatrical item, either, so saying "use trained people" doesn't always cover it...)
Thanks, and again, please understand that I'm not trying to ask questions that I shouldn't on this forum -- a nudge in the right direction toward a standards document and/or some manufacturers is entirely ok. Advance apologies if I've said or asked something I shouldn't.
Question 1: I've been told some hand-wavy numbers about spacing on lift lines for dead hung battens (some for boring things like legs, some for more exciting things like electrics). I've generally heard 8' is safe and 10' might be ok. Are there any good sources I can point to? (He would like 3'...) Naturally, we plan to use 1-1/2" schedule 40 "gas pipe", with batten splices where appropriate, probably in 20' lengths.
Question 2: Also, this space will involve entirely dead-hung battens, with the possibility for expansion or at least movement later. The only access to the ceiling will be via scaffold (or lift). There are structural beams running SL<->SR above the stage, which our engineer plans to specify attaching to. The only place I've worked that has done this has used unistrut running upstage-downstage, structurally attached to the beams, with the channel facing down, with rated eye bolts mounted on unistrut mounts that are then attached to shackles and finally lift lines. Even though the plan is that you can loosen the eye bolt, slide the mount along to the desired position, and re-tighten it, to my mind the possibility of doing that under load without realizing it or of not tightening it appropriately or in the proper orientation is mind-boggling. (Disclaimer -- this setup also came with an engineer's stamp of approval -- were I the engineer, I shouldn't think I'd stamp it, and I don't recommend you use this setup.) Obviously I've worked plenty of places where I-beams were installed upstage-downstage in the appropriate locations and enormous beam clamps were used for the lift lines, but this appears to be orders of magnitude more expensive, not to mention that we need to subtract the weight of the new beams and hardware from what we'll be allowed to eventually hang. Could anyone point to some good resources that I could give the engineer on this subject? (I'm also secretly hoping there is a product like unistrut where the mounts don't just fall out if you're careless, or a magical circular unistrut mount that's a pain to install but doesn't actually fall out when it's a little loose -- I've seen safer systems for track lighting in office ceilings.) And yes, I understand that the sleepy or the careless shouldn't be doing rigging, and that a sufficiently sleepy or careless person can make anything fall on anyone regardless of design; it's just that the unistrut system seems so questionable that it keeps me up at night, especially since I've definitely worked with reasonably experienced people who are unfamiliar with unistrut and are floored by the fact that the little piece can just come right out -- what about the day I'm not there to tell them? (Unistrut isn't a super-theatrical item, either, so saying "use trained people" doesn't always cover it...)
Thanks, and again, please understand that I'm not trying to ask questions that I shouldn't on this forum -- a nudge in the right direction toward a standards document and/or some manufacturers is entirely ok. Advance apologies if I've said or asked something I shouldn't.
