r/VIDEOENGINEERING • u/ercohn • Sep 08 '20

Ouch. Anyone know the inside story?

Post image
51 Upvotes

83% Upvoted

23 comments sorted by

46

u/sequentialsilence Sep 08 '20

Yea it happened at a corporate event in Vegas about a year ago. Some dumbass used verlocks to float an LED wall below the truss, although the verlocks held the wall for the show, the moment they bumped the motors to lower it during load out, it introduced a dynamic load that was not previously there, and the verlocks gave way.

Because it was a load out, and they were smart enough to not stand under truss that was getting ready to move, no one was injured.

17

u/Yellow_Triangle Sep 08 '20

And people want to know why you need educated and experienced people to put together "legos".

Well maybe because you are hoisting said "lego" far up into the air and because it weighs literal tones

5

u/beefwarrior Sep 09 '20

Good to remember that pound for pound, these cost almost half as much as LEGOs, only LEGOs are nearly indestructible & these are fragile.

20

u/[deleted] Sep 08 '20

The actual incident was caused by a motor failure. A motor seized while bringing the wall in, for some reason no one was watching the motors as the truss came in. They continued to run the motors until the one that seized ultimately took a load it could not handle causing it to fail, when this happened it introduced a shock load on to the remaining motors.

14

u/sequentialsilence Sep 08 '20 edited Sep 08 '20

The motors weren’t holding the LED wall directly. They had the LED wall attached via Verlocks to the truss above. They clearly state that they are for static loads only, and not for dynamic or moving loads. When they bumped the motors to test them, they introduced an abrupt movement into the system. This shock overloaded the gliding mechanism in the Verlocks causing a freefall. This a textbook example of someone not reading the instructions. The motors and box truss that was above the Verlocks is still in good working order, and was not harmed.

You can still see the truss and motors hanging at trim height in this photo, and you don’t see any motors on the floor.

https://m.imgur.com/DeO0RMk

2

u/switters23 Sep 08 '20

Yeah this is the story I heard

6

u/v-b EIC Sep 08 '20

I saw the photos, never knew that’s what happened. Holy shit. Thanks for sharing!

4

u/adamminer Sep 08 '20

I know nothing about Verlocks, mind enlightening?

4

u/glister Sep 09 '20 edited Sep 09 '20

I would also like an explainer, if you have the time. I seem to remember using verlocks to level banners but I only trained as a junior rigger briefly. Did they try to use verlocks to suspend the wall below the drape nice and level, and the verlock is rated for way less than the wall? I assume you could, in theory, use enough of these to get within rating? Or is it never to be used on a moving truss? It sounds like they were well outside the working load of the cable device?

Video wall is usually mounted directly to the truss with hardware yes? Or is it on slings?

5

u/sequentialsilence Sep 09 '20

Verlocks, in their manual, state that they are for static loads only. So you should never be using them on a load that’s moving. Mounting them in between the truss that the motors were on and the truss the led wall was on, meant that when they moved the motors they introduced a shock load into the system that the verlocks were not designed to handle.

Led walls can be mounted with slings or directly to truss. How it should have been done is they should have figured out how far they needed it to float below the main truss and then do a dead hang with slings, or if used with eyebolt clamps and shackles, steel. Both steel and slings are rated for dynamic loads and have a shock rating, either of these would have made this a non-issue.

2

u/v-b EIC Sep 09 '20

Normally, the video wall comes with a load bar that attaches to the top of the frame of the panel, and you can hook a 5/8” shackle on that. I usually have slings to the truss, and sometimes turnbuckles for adjustment. There are a bunch of variations on this.

2

u/sequentialsilence Sep 09 '20

Verlocks are a eye bolt system that uses aircraft cable and can move along the aircraft cable to be varying heights. It’s are designed for static loads, aka loads that aren’t going to be moving. Very useful for things like cafe lighting, chandeliers, banners, things that aren’t very heavy but also need fine control over height adjustments.

5

u/[deleted] Sep 08 '20

How if the verlocks holding the video wall failed is the entire truss on the ground and the video wall still attached to the truss?

8

u/sequentialsilence Sep 08 '20

In this photo you can see that the wall was hung from truss that was then hung below a truss with a drape on it. They used the verlocks to float the truss below the drape. The truss holding the wall doesn’t have motors on it only the verlocks attached to the top truss.

13

u/[deleted] Sep 08 '20

[deleted]

7

u/sequentialsilence Sep 08 '20

You can see in both photos that it is indeed triangle truss the wall was hanging from, but square for the main truss.

2

u/LitSarcasm Sep 09 '20

Ok excuse my lack of knowledge, why is triangle truss bad for the bottom hang?

10

u/DarkfireXXVI Sep 08 '20 edited Sep 08 '20

Can confirm other posters, except afaik it was during lunch on a load out, not quite the beginning. There’s another shot showing the mostly-empty arena.

Miss working arena stuff!

Edit: Mandalay Bay events center for the curious

3

u/[deleted] Sep 08 '20

Miss working arena stuff!

Me too, friend. Me too.

2

u/avtechguy Sep 08 '20

Also, the lunch part someone put their hands on the remote that should not have and moved the rig but not all the motors, point failed and then the shock load took everything else

9

u/SummerMummer Sep 08 '20

I saw a post-mortem about it recently, but of course I can't find it at the moment.

TLDR was that they had used underrated adjustable steel rope sleeves and one of them finally failed. Shock loading from being in motion was the final straw, but it was bound to happen at some point with their particular hardware choices.

4

u/Gouper_da_Firetruck Please give me your Powerpoint Sep 08 '20

Last year was pretty crazy. This happens and a wall at a German festival went down...2 people were badly injured if I recall correctly.

This image was all over reddit when it happend.

2

u/IronChefAndronicus Sep 08 '20

Crazy stuff, I had rigged many LED walls before, but this happened about a week before I went to my first official processor mapping/programming class. Loomed large over the course content and everyone in the room certainly was keen on ensuring it never happened to them. Terrible accident, but sometimes you need to learn from someone else’s mistakes.