ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: [1]   Go Down

Author Topic: Please be aware of your rigging points.  (Read 2007 times)

Al Rettich

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 598
Please be aware of your rigging points.
« on: July 16, 2018, 02:46:30 PM »

Hey everyone.  I’m hoping by attaching this photo when you are at your gig you won’t rig your PA this way.  This is a K1/K2 array by my bare eye guess I’m saying 1900-2000 pounds.  To get a front and back point they took a five foot piece of truss and clamped from the top.  Again it’s been awhile, but I think the last time I checked the heavy duty clamps were good for 1100lbs. Looking at this photo front and back is good for 2200lbs.  Yet if you’ve been rigging for awhile you know the load we worry about is shock. I ran into a similar situation like this and the clamps were rated for 600lbs each.  Please be safe out there. 
Logged

Mike Pyle

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1215
  • Santa Rosa, CA
Re: Please be aware of your rigging points.
« Reply #1 on: July 17, 2018, 11:04:56 AM »

It would appear the load is resting on top of the clamps, not suspended by them.
Logged
Mike Pyle  Audiopyle Sound  707-315-6204
Dealer For: JBL, Soundcraft, Crown, dbx, AKG, Yorkville, EV, QSC, RCF, FBT, Danley Sound Labs, Meyer Sound, Fulcrum Acoustic, Tannoy, Lab Gruppen, Powersoft, Linea Research, EAW, Allen & Heath, Ashly, APB, Audix, One Systems, Presonus, K&M, Ultimate, Global Truss, Intellistage, SKB, Gator, Radial Engineering, Turbosound, Midas, dB Technologies, American DJ, Odyssey, ProCo, Rapco, CBI, Elation, Mipro, Chauvet, Blizzard, Shure, Whirlwind, Bassboss, Yamaha, Line 6, Behringer, On-Stage, more...

Al Rettich

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 598
Re: Please be aware of your rigging points.
« Reply #2 on: July 17, 2018, 10:17:55 PM »

Correct, but as the Pa goes up in the air it’s pulling from the back to the front or vice Versa.  What happens if a problem with the front motor, and the full amount of the PA is resting on either the front or back point.  Think those clamps would hold 2000lbs of weight??
It would appear the load is resting on top of the clamps, not suspended by them.
Logged

Milt Hathaway

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2300
    • http://www.fitzcosound.com
Re: Please be aware of your rigging points.
« Reply #3 on: July 17, 2018, 10:26:48 PM »

Think those clamps would hold 2000lbs of weight??

In compression? Certainly. And much more than the thinner aluminum pipes they are sitting between.

I'm betting all ratings for double-cheeseboroughs are either in tension parallel to the connecting pin or the shear strength of the pin itself, whichever is lowest. Either of these is certainly lower then straight compression.
Logged
--
Milt
FitzCo Sound, Inc.
Midland, TX
http://www.fitzcosound.com

Jason Glass

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 918
    • CleanWirelessAudio.com
Re: Please be aware of your rigging points.
« Reply #4 on: July 17, 2018, 11:11:24 PM »

In compression? Certainly. And much more than the thinner aluminum pipes they are sitting between.

I'm betting all ratings for double-cheeseboroughs are either in tension parallel to the connecting pin or the shear strength of the pin itself, whichever is lowest. Either of these is certainly lower then straight compression.
If either one of those motors or chains lets go, one pair of clamps instantly becomes a fulcrum and the other pair goes into tension, with the mass on a cantilever, multiplying its load on the tensioning clamps.  Think see-saw.  Same situation if strong wind starts swinging the PA.

Sent from my Nexus 5 using Tapatalk
« Last Edit: July 17, 2018, 11:17:45 PM by Jason Glass »
Logged

brian maddox

  • Hero Member
  • *****
  • Online Online
  • Posts: 3267
  • HeyYahWon! ttsss! ttsss!
Re: Please be aware of your rigging points.
« Reply #5 on: July 17, 2018, 11:25:03 PM »

If either one of those motors or chains lets go, one pair of clamps instantly becomes a fulcrum and the other pair goes into tension, with the mass on a cantilever, multiplying its load on the tensioning clamps.  Think see-saw.

Sent from my Nexus 5 using Tapatalk

I went back and looked at the picture and then imagined the downstage point giving way.  The extra leverage and the resulting torsional force on that upper truss.  The PA Swinging down and back and the centripetal forces involved.

*shudder.... 

Yeah, that would break things and come down hard, I don’t care what the rating of the cheesboroughs is.

It bears repeating.  Safe rigging isn’t figuring out what will be safe if everything holds.  It’s figuring out what will still be safe when something fails.
Logged
"It feels wrong to be in the audience.  And it's too peopley!" - Steve Smith

brian maddox
[email protected]
Savannah, GA

'...do not trifle with the affairs of dragons...

       ....for you are crunchy, and taste good with ketchup...'

ProSoundWeb Community

Re: Please be aware of your rigging points.
« Reply #5 on: July 17, 2018, 11:25:03 PM »


Pages: [1]   Go Up
 



Site Hosted By Ashdown Technologies, Inc.

Page created in 0.045 seconds with 25 queries.