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Author Topic: Rig truss below or above material lifts  (Read 482 times)

Shy Clyman

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Rig truss below or above material lifts
« on: September 12, 2017, 03:00:09 am »

Hey guys,
Just looking for some pointers. I have Genies that currently have some custom fork adapters to have a single hang point that are used for line arrays. We occasionally need to have a section of truss run across the top of the stage. Should the truss be suspended from the forks via truss pick or laid on top of the forks and secured down and why?

Thanks!
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Mark Cadwallader

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Re: Rig truss below or above material lifts
« Reply #1 on: September 13, 2017, 09:17:35 pm »

If given a choice, I would rest the truss on top of the forks rather than hang them. First, there are two points of support, rather than the single point hang. Second, the rigging between the two forks loads the forks in compression (squeezed towards each other). I doubt (but don't know) that was part of the design spec and intended loading. Either reason seems to me to be sufficient by itself to rest the truss on the forks, but I am not a licensed professional engineer or a certified rigger, so YMMV.
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Scott Holtzman

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Re: Rig truss below or above material lifts
« Reply #2 on: September 13, 2017, 09:19:32 pm »

If given a choice, I would rest the truss on top of the forks rather than hang them. First, there are two points of support, rather than the single point hang. Second, the rigging between the two forks loads the forks in compression (squeezed towards each other). I doubt (but don't know) that was part of the design spec and intended loading. Either reason seems to me to be sufficient by itself to rest the truss on the forks, but I am not a licensed professional engineer or a certified rigger, so YMMV.

Seems to make sense to me too, however I have always seen them rigged below the forks on Genie's in my limited experience (and all with guys from the same local)

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Mark Cadwallader

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Re: Rig truss below or above material lifts
« Reply #3 on: September 13, 2017, 09:32:24 pm »

Seems to make sense to me too, however I have always seen them rigged below the forks on Genie's in my limited experience (and all with guys from the same local)

It probably takes a bit more thought process to figure out a good way to secure the truss to the forks so they can't walk or slip off the forks. But because you don't have to hang the load from rigging, I suspect that you have a wider choice of materials and techniques. Once you have figured out a reasonable way to do it, you don't have to re-invent the process.  Whether it is faster one way or the other, I don't know. It is probably faster to double check being secured to the forks than triple checking a hanging load.
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