[SML] Rigging calculation question...

[Brian Munroe]

This is an indeterminate load and virtually impossible to easily calculate accurate loads-per-point.  Load cells would be your best bet.

 

A rough starting point (and I mean very rough) might be to discard the outer two motors from your calculations and then use a uniformly distributed load of the wall and truss weight on a four point system.  Remember that, as Bill said, the inner points will have a majority of the weight.  Using the percentages from Jay Glerum’s book for line sets, you would see .113 on the outer motors (of four) and .367 on the inner motors.  Again this is very rough.

 

Why a 70’ truss for a 44’ load?  Also being used as a cable bridge?

 

 

From: Stagecraft [mailto:stagecraft-bounces at theatrical.net] On Behalf Of Jason C via Stagecraft
Sent: Wednesday, October 5, 2016 4:05 PM
To: Stagecraft <stagecraft at theatrical.net>
Cc: Jason C <jasonclights at gmail.com>
Subject: [SML] Rigging calculation question...

 

So how do you all calculate loads for large items that have several connection points to the truss they are hung from?

 

Example, 70' Truss flown off 6 motors to steel beams.  Hanging an LED wall off the truss.  Wall is 44' long, centered on the truss.  Total weight of wall and hanging hardware is roughly 4600lbs.  the wall/hardware will connect to the truss at approximately 20 points along the length of the wall.

 

To get a rough estimate, I was encouraged to just do an evenly distributed calc across the 6 motors, but I know this is not accurate as the wall only extends a few feet past the inside 4 motors.  Almost all the weight is contained to the inside 4 motors if I understand it correctly. 

 

Any thoughts as to how should I be calculating this load so I can get an acceptably accurate idea of load per motor point?

 

Thanks!

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