Our Answer to this Week’s Post, “What’s wrong with this Entertainment Application?”

Our Answer to this Week’s Post, “What’s wrong with this Entertainment Application?”

Dave Carmack 8-28-12

Thank you, Tim & Harris, for your comments. We also received interesting insights on our Facebook page. You know your rigging!  Here is my take on this application:

This is a wire rope support grid. These 1 foot squares allow a rigger to quickly position light loads in specific spots by dropping in a rope through the appropriate square. The anchor point is fixed up above the structure. Notice the strap in the background.

Let’s now address the problems:

  • The thing that jumped out  most to me was the construction of the grid.  The wire ropes must be woven or knitted together.  These were not.  Each overlap should alternate over and under.  This installation has all the ropes in the same direction and on the same side.  The weaving should run in the x and y directions.
  • U-bolts are used to connect each overlap. Since the grid installation itself is wrong, U-bolts are not an acceptable option. U-bolts are typically used for light weight or minor connections such as conduit to a pole. I do not think that you could get the clamping force needed using U-bolts to keep the wire rope cables from slipping under a side force. Wire rope clamps are designed for use with cables.
  • A few of you observed the missing nut on one of the U-bolt assemblies. Nice catch.

When a wire rope support grid is assembled correctly, it transfers the stresses.  When the grid is assembled like in this application, the neighboring ropes are not supporting anything, which can lead to very unfavorable consequences.

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Thank you again to everyone who submitted comments. We love to hear from you!  Do you have an application you would like us to review?

 

Disclaimer

Dave Carmack

Dave is a Product Trainer for our CM Entertainment Division. Other credentials include being an ETCP Recognized Trainer & IATSE TTF Recommended Trainer.

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4 Replies to “Our Answer to this Week’s Post, “What’s wrong with this Entertainment Application?””

  1. Hi Charlie,
    Yes I did see your post. We thank you for your input and would love to get more responses from the field. If you have some “wrong” pictures, pictures for conversation or even words of wisdom, we would love to share them.
    All the best,
    Dave

  2. Dave,
    I commented on Mike Weston page, didn’t know it was you who wrote this. Did you see my response on the wrong use of U Bolts?
    Cheers,
    Charlie
    See ya soon.

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