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[Brian Larson]

I have an event coming up where sight lines are very important. I would like to fly a pair of QRX212s and some LED pars from a piece of truss sitting on Applied L-11 crank stands.

The max rated weight each stand can take is 200lbs. Since I'll be using two stands connected by 20' of truss, the total weight I can lift is 400lbs, correct?

I plan to have the stands in about 2' from the ends of the truss and hang the speakers (with proper hardware) on the outsides of the stands.

The math makes sense:

QRX212: 85lbs ea.--170lbs
Truss segment: 42lbs ea.--84lbs
LED par: 10 lbs ea.--60lbs
Hardware/cabling: +/- 50lbs

The total weight should be about 354lbs.

Does anyone think this could be safe?

Thanks.

[James A. Griffin]

I have an event coming up where sight lines are very important. I would like to fly a pair of QRX212s and some LED pars from a piece of truss sitting on Applied L-11 crank stands.

The max rated weight each stand can take is 200lbs. Since I'll be using two stands connected by 20' of truss, the total weight I can lift is 400lbs, correct?

I plan to have the stands in about 2' from the ends of the truss and hang the speakers (with proper hardware) on the outsides of the stands.

The math makes sense:

QRX212: 85lbs ea.--170lbs
Truss segment: 42lbs ea.--84lbs
LED par: 10 lbs ea.--60lbs
Hardware/cabling: +/- 50lbs

The total weight should be about 354lbs.

Does anyone think this could be safe?

Thanks.

My own Rule Of Thumb is to limit loads on lifts to 80% of rating, even though rating likely has a safety factor of 2.    In case of L11, that's 320# per pair.   Not saying not to do it.  YMMV

[David Morison]

I plan to have the stands in about 2' from the ends of the truss and hang the speakers (with proper hardware) on the outsides of the stands.

[Not a Rigger - gut reaction only follows]
I'd want to check with Applied and possibly also the Truss manufacturer to be sure that doing this won't pose too much of an offset load on the stand, with too much of the weight off-centre - I can easily imagine that may require de-rating the load capacity if so.
[/Non-Rigger gut reaction]

[Geoff Doane]

I'd want to check with Applied and possibly also the Truss manufacturer to be sure that doing this won't pose too much of an offset load on the stand, with too much of the weight off-centre - I can easily imagine that may require de-rating the load capacity if so.

If the truss is level, and the stands are vertical, the only load on the stands is vertical. As long as the load on the truss is symmetrical (it doesn't even have to be evenly distributed), the vertical load on the stands will be the total weight divided by two.

Concentrating the load in only two locations (or in the middle) might unduly stress the truss, but not the stands.

As far as whether your scenario is safe, I'm going to take the easy way out, and decline comment. 

GTD

[Marlow Wilson]

I'm going to take the easy way out, and decline comment. 
GTD

Always the safe route Geoff!

I'm not a rigger either, and I would recommend calling applied who may well tell you that it isn't a very good option.  One thing I can comment on is the truss arrangement.  In general you want the truss supported at both ENDS so that as the bending moment and shear force within the truss transfers back to the support points, the top chords are kept in compression and bottom chords in tension.  This is how it's designed to work. 

My experience working with city engineers to approve designs using L16's was that they were most concerned about having an adequate ballast for outdoor events.  Is this outdoors?

[Brian Larson]

The event is under a tent. Not sure yet if there will be side walls.

I'll give Applied a call. Thanks everyone!

[Mac Kerr]

The event is under a tent. Not sure yet if there will be side walls.

I'll give Applied a call. Thanks everyone!

Call the tent company. Modern truss type tents can support some extra weight. The tent company may have the hardware to attach to their tracks.

Mac

[Brian Larson]

Good call, Mac. Hadn't thought of that.