Archive for May, 2016

Can you Trust your Truss??

May 3, 2016 Comments Off on Can you Trust your Truss?? Working in Circus

Opening Caveat! We are not riggers. While a professional qualified rigger was consulted for this blog, this blog is only meant to help you identify red flags and to know when to bring in the expert. Experts take years and lots of math to do what they do well. Please do not go around fixing anything based on what you see here. And really, ask questions, and take a rigging class. In other words, don’t try this at home. Okay, butts covered. Now we may begin. 

P1010096 (4)I don’t know about you but when I started as an aerialist and I heard there was a truss to hang from on a gig, I would relax. To me, it meant I didn’t have to make some judgment call about a hook in the ballroom or figure out how to get around a beam that was covered by a false ceiling with some damn chandelier in the way. All I would have to do is tell the tech person the proper load ahead of time, ride that genie lift, whip out my span set, and boom, finito. Latte sipping til show time.

Needless to say, I’ve wised up. I now send a qualified rigger to check things out (especially if we are using multiple aerialists) when there is a truss involved. I’ve realized that all tech people don’t necessarily listen or know what they are doing, because, well, hanging flying humans is a different thing than hanging lights. Luckily, I listened to my gut, and was able to fix situations that looked wrong. I also have access to an amazing human and rigger, Bill Auld, who is happy to answer questions at odd hours and who is also partly responsible for some of this information. Anything incorrect is probably my error.

Here are some things to look for and to know whether or not you need blow the whistle and get a qualified second opinion, which is why you want to try as hard as possible to speak to the rigger who is setting up your truss if at all possible ahead of time.

Truss comes in a few different flavors – engineers may more accurately call them “configurations.” In big bold terms you want truss that is built to be used for how you are using it. What flavor is that? That is, you need truss that is engineered to be a beam – or lay on its side spanning a gap – that you can then hang from. That is truss that is square or rectangular in shape that has diagonal runs going all the way up the sides and every so often a diagonal ‘chord’ running on the inside. Truss that is marked “antenna truss” is right out. It is meant to be used to stand up on end like a big radio or TV antenna and not laid on its side like you are using it. Any truss that is triangular in nature, or worse ‘flat’ – that is it looks like a ladder (Often called ‘two-dimensional truss’) – should just be passed over and left to engineers.

1. If a chain motor is holding the truss, how many people are on it? What are they rated for? How many are being used? Not all chain motors are the same. Chain motors aren’t made to handle dynamic loads. Generally speaking the gears holding that thing in the air when it is stopped aren’t made for you to be bouncing on them.  If it is being hung from a chain motor, is there a way to “dead hang” it once it is up in the air? That is, to haul it up and then tie it off or hang in on proper rigging steel cables so that the first line of defense against gravity is not those gear teeth that don’t like you jumping on them?

2. How is the truss assembled? Does anything look off? We showed up somewhere and found chain wrapped a few times (and unsecured) around the top section of truss then “reinforced” with 2 by 4’s!!! I’m not kidding. A more common mistake when untrained people assemble truss is that they don’t line up the diagonal webs of it. Check where two sections are attached together. Does that diagonal run along the side that makes the endless series of triangles continue unbroken? If so, great. If you are tracing it with your finger and see it go DOWN, UP, DOWN,… DOWN! UP right at the point where two sections are bolted together, then someone assembled the truss wrong. It is not as strong as it could be. Have them take it apart and flip a section so that pattern remains unbroken.

3. Can the truss handle the load the way it is set up? You just have to have common sense. Is there a 50 foot stick going across the room unsupported in the middle? (This just happened, for realz). If so, it won’t handle much in the middle. Find out who made it. Remember the people that make the truss are on your side! They want you to be safe as much as you do and so reputable manufacturer’s of truss often freely post what their stuff can handle – at least in big bold terms. Google is your friend.

4. Does the person who built the truss actually understand dynamic forces? Do they believe you when you say each aerialist can generate 1000 pounds of force? If they don’t or seem surprised by that fact, be nervous. Very nervous.

5. Even if you have sent your tech rider and told them what you need, find out if they actually read it or if the end person got that information. Many times it gets passed around, and never actually read.

6. Neatness counts! “I used to jump out of airplanes for a living and when I did there was a saying bantered about, “Tie your shoes properly or someone dies!” Now that seems like hyperbole if taken literally. What it was referring to was that there is a certain thorough tidiness to a good craftsman’s work. It reflects the idea that if someone takes the time and effort to manage the small things you can see quite easily, they are prone to doing that for all the big things they do as well. That comes from having the discipline to do the job right; something that is both rare and to be prized. Nowhere is this more relevant than with aerial work – either rigging or performing. So apply that to the truss you are about to trust. If you look up and see a truss that has been assembled carefully, the ropes and chains holding it have been coiled and dressed neatly, all the little details have been arranged systematically, and the space has been cleaned up lovingly, than breathe a little sigh of relief. “I cannot say the rigger who did that work knows what they are doing. I cannot even say everything will be fine. But I can say whoever did do that possesses a certain level of training and discipline on the small scale that will have significant effects on the fortitude and safety of your rig on the large scale. And in the end, that may make all the difference in the world.” – Bill Auld.

 

So there you have it from the horse’s mouth. Obviously, we have not covered all the possible outlandish scenarios here and may have forgotten an important point, so if you have a story of your own or something to add please share!

Dare to Imagine Safety!

Angela Attia