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Author Topic: Getting out of trouble before it happens (unistrut rigging)  (Read 920 times)

Dave Guilford

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Just acquired a set of srx835 speakers (finally) and a mobile stage (finally) that’s rated to hang 250lbs per side.  Fly bars protrude from roof of course, approx 12-18”. 

I have a few conversations with local rigging crew.  I’m smart enough not to do it my own, and I’m smart enough to know the good info I’ll get here.  Otherwise I’m pretty dumb.

In my head this works with a sling around fly bar, which puts me at one point for speaker. The speaker has m10 bolts at top, so a piece of unistrut spanning them (15” ish) with a eye bolt at the center of the unistrut.  An m10 eyebolt at the 3rd hole on top for safety cable. An m10 eyebolt at the rear botto
 for pullback.

NOW - tell me why this is a bad idea, and how I should do it properly. The trick is that we need the speakers up as high as they can be to the fly bars.  Mounting unistrut to top of speaker basically gets it “flush” to the sling / shackle.
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Doug Fowler

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Re: Getting out of trouble before it happens (unistrut rigging)
« Reply #1 on: June 15, 2021, 09:54:39 pm »

Just acquired a set of srx835 speakers (finally) and a mobile stage (finally) that’s rated to hang 250lbs per side.  Fly bars protrude from roof of course, approx 12-18”. 

I have a few conversations with local rigging crew.  I’m smart enough not to do it my own, and I’m smart enough to know the good info I’ll get here.  Otherwise I’m pretty dumb.

In my head this works with a sling around fly bar, which puts me at one point for speaker. The speaker has m10 bolts at top, so a piece of unistrut spanning them (15” ish) with a eye bolt at the center of the unistrut.  An m10 eyebolt at the 3rd hole on top for safety cable. An m10 eyebolt at the rear botto
 for pullback.

NOW - tell me why this is a bad idea, and how I should do it properly. The trick is that we need the speakers up as high as they can be to the fly bars.  Mounting unistrut to top of speaker basically gets it “flush” to the sling / shackle.

Is there something on the end of the fly bars (a lip?) to prevent sliding off the end?

And, is the roof system rated to raise it with the extra weight?

The M10 points on top are basically 18" apart.  Be careful of putting a lateral load on the M10s.   It's possible but it's also de-rated.

Measure the fly bars, it would be useful to know "how long".  A photo or a pointer to roof specs would be useful as well.
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Dave Guilford

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Re: Getting out of trouble before it happens (unistrut rigging)
« Reply #2 on: June 15, 2021, 11:40:51 pm »

Thanks for chiming in. 

- yes flybars have a lip to prevent sling from sliding off.  That was my first question I asked about them before buying the stage !

- roof goes up with hoists, and then hoists bring speakers up.  Which is why I’m down to 1 fly point.  Unless there’s something I don’t know about.  Again, part of why I’m running the idea here and thank you.

- I’m not sure there would be lateral loads in my concept , just vertical.  Assuming spacing of unistrut “lines up” with the spacing of m10 holes.

- fly bar is 12”. Maybe 18”.  I can check tomorrow. 

https://drive.google.com/file/d/1D6zy9Jf-STCohWAtXh0NA2SP-D6VI8rI/view?usp=drivesdk
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Doug Fowler

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Re: Getting out of trouble before it happens (unistrut rigging)
« Reply #3 on: June 16, 2021, 12:13:01 am »

Since the roof goes up with hoists rather than a pneumatic system driven by a small engine, is there not enough lifting headroom to take the loudspeakers up simultaneously?  It's not that much weight.
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Peter Morris

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Re: Getting out of trouble before it happens (unistrut rigging)
« Reply #4 on: June 16, 2021, 04:01:22 am »

Just acquired a set of srx835 speakers (finally) and a mobile stage (finally) that’s rated to hang 250lbs per side.  Fly bars protrude from roof of course, approx 12-18”. 

I have a few conversations with local rigging crew.  I’m smart enough not to do it my own, and I’m smart enough to know the good info I’ll get here.  Otherwise I’m pretty dumb.

In my head this works with a sling around fly bar, which puts me at one point for speaker. The speaker has m10 bolts at top, so a piece of unistrut spanning them (15” ish) with a eye bolt at the center of the unistrut.  An m10 eyebolt at the 3rd hole on top for safety cable. An m10 eyebolt at the rear botto
 for pullback.

NOW - tell me why this is a bad idea, and how I should do it properly. The trick is that we need the speakers up as high as they can be to the fly bars.  Mounting unistrut to top of speaker basically gets it “flush” to the sling / shackle.

I think the SRX835 has 3 bolt holes on the top  https://jblpro.com/en/site_elements/jbl-professional-srx835-spec-sheet
 
So ... get an engineering shop to build a frame a bit like this that bolts to the top of the box and the pick a hole on the middle beam for your shackle (rated) that gives you the box angle you need. To fly stuff design it with a 10:1 safety factor.
« Last Edit: June 16, 2021, 04:05:41 am by Peter Morris »
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Doug Fowler

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Re: Getting out of trouble before it happens (unistrut rigging)
« Reply #5 on: June 16, 2021, 04:30:21 am »

I think the SRX835 has 3 bolt holes on the top  https://jblpro.com/en/site_elements/jbl-professional-srx835-spec-sheet
 
So ... get an engineering shop to build a frame a bit like this that bolts to the top of the box and the pick a hole on the middle beam for your shackle (rated) that gives you the box angle you need. To fly stuff design it with a 10:1 safety factor.

Perfect.  The question remains about lifting loudspeakers with the roof, to maximize trim height.
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Dave Guilford

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Re: Getting out of trouble before it happens (unistrut rigging)
« Reply #6 on: June 16, 2021, 08:05:23 am »

My stage designer has always said “lights can go up with the roof but not PA”.  I suppose I could try , but I’d rather be safe than sorry.

As for fly bar - that looks super.  I like it.

I’m not familiar with “engineering shops” in my area.  A fabricator?  Or do any of you folks have the means?  What would you expect to pay for custom fly bars like that?
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Peter Morris

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Re: Getting out of trouble before it happens (unistrut rigging)
« Reply #7 on: June 16, 2021, 10:34:48 am »

My stage designer has always said “lights can go up with the roof but not PA”.  I suppose I could try , but I’d rather be safe than sorry.

As for fly bar - that looks super.  I like it.

I’m not familiar with “engineering shops” in my area.  A fabricator?  Or do any of you folks have the means?  What would you expect to pay for custom fly bars like that?

FWIW here is a frame I made for our J7's. Its 50 x 50mm RHS with a wall thickness of 2.5mm (from memory, I would need to check)  - more than 10:1 safety factor and the J7 weighs 125Kgs.  It bolts onto the box through the 4 holes in the top of the frame.
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Scott Holtzman

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Re: Getting out of trouble before it happens (unistrut rigging)
« Reply #8 on: June 17, 2021, 03:55:34 am »

My stage designer has always said “lights can go up with the roof but not PA”.  I suppose I could try , but I’d rather be safe than sorry.

As for fly bar - that looks super.  I like it.

I’m not familiar with “engineering shops” in my area.  A fabricator?  Or do any of you folks have the means?  What would you expect to pay for custom fly bars like that?


Did you buy a Great Lakes Stage?  I can't wait to hear your experience.  It fills a niche for the rib fests and such that the SL50/75 is too much for but is still safe and decent size.  Well he says it is safe and sturdy, I want to hear what you have to say!



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Scott AKA "Skyking" Holtzman

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Dave Guilford

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Re: Getting out of trouble before it happens (unistrut rigging)
« Reply #9 on: June 17, 2021, 09:25:35 am »


Did you buy a Great Lakes Stage?  I can't wait to hear your experience.  It fills a niche for the rib fests and such that the SL50/75 is too much for but is still safe and decent size.  Well he says it is safe and sturdy, I want to hear what you have to say!

Yes I did!   Too much to type here for all details BUT here’s a quick review, based on the 4 or 5 times I’ve used it so far.

-very clever. Most things get used for more than one purpose. Thought-out design!
- good construction. Feels stable and sturdy when put together properly.
- a lot of small steps. The old “do this before that” and order of operations. Lots of hand work, since no pneumatics or hydraulics.
- definitely a money maker.  SL50/75 goes for $1500-2200 in my area.  I’m doing $700-800ish (varies on a number of things of course).
- has some limitations, like only 250lbs per side on wings. But at this level I ground stack PA anyways.
- lots of moving parts means I’ll likely need replacements to cover wear and tear. However parts are cheap since it’s all “off the shelf” things.  A worm gear $150 every few years.  125ft airline cable every few years. 
- unique look means people recognize it “I saw that on a Facebook ad”
-only 67mph wind rating.
- feels safe, yes.

All in all, very nice price up front but extra work bc no automation with setting it up. For half the cost of a SL75, I’m quite happy. Certified for insurance compliance is a must, and this meets that.

I’m pretty sure I’ve seen you in mobile stage pro group in Facebook.  I’ll post some extra photos of today’s gig with it over there
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Re: Getting out of trouble before it happens (unistrut rigging)
« Reply #9 on: June 17, 2021, 09:25:35 am »


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