Sample Sidebar Module

This is a sample module published to the sidebar_top position, using the -sidebar module class suffix. There is also a sidebar_bottom position below the menu.

Sample Sidebar Module

This is a sample module published to the sidebar_bottom position, using the -sidebar module class suffix. There is also a sidebar_top position below the search.
Saturday, 01 July 2017 03:27

Is Modtruss Really Needed?

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Modtruss is awesome, shiny and cool looking. But is it really needed? I pulled up the spec sheets for 12" aluminum Modtruss, 12" Tomcat, and 20.5" Tomcat to crunch the numbers. Here are my thoughts...

Let me start this article by explaining that I have never personally used Modtruss. I saw it for the first time at Paramount during Cinegear in 2016 and I thought it was something awesome, fascinating, innovative and cool. I have however used Tomcat, Thomas, and other brands of the standard truss for years. I got excited thinking this was something new I could start using as a part of my toolset. It lead me to research it more.

A year later, and this in my current opinion. I personally am not a fan of the mod truss. Yes it looks cool. Yes it is versatile. And just the fact that it means I never have to use a grapple again makes me want to run out and buy it. But for my needs, 90% of the time I don't think I would want to use it it. Here is why I feel it falls short...

One of the major elements we have to take into account when designing truss structures, is the weight of the truss itself. A lot of the times we are hanging truss in a building, we are limited by the building structure and will hit the point load limit of the structure before we will hit the limit of our truss. The heavier the truss is, the less capacity you are going to have to hang items from it before hitting your point load limit on your rigging anchors. Also, if you are hanging truss spans from other truss, the weight of the lower truss itself needs to be accounted for and starts eating into your available capacity fast.

Chapman Supernova truss platform designed by Scene Snipers

When my crew and I build a truss platform on the end of the Chapman Supernova. One of the biggest variables was shaving every ounce of weight off the structure we could SAFELY. That meant using aluminum decking instead of steel deck, aluminum cheeseboros instead scaffold clamps, etc. We ended up just shy of the weight capacity on the arm of that crane. We never would have been able to do that rig with Modtruss. The chapman supernova would not have been able to support it. As it was, chapman had to send a stake bed out with additional weights to balance the arm.

Lets do some comparisons of the weight of a 10’ long stick of 12" Modtruss against the tomcat 12” & 20.5” truss.

12” Modtruss: 95.5 lbs
12” Tomcat: 60 lbs
20.5” Tomcat: 69 lbs

The Modtruss is significantly heavier than both the 12” and 20.5” Tomcat truss. Now lets look at the load limits for a 10’ span of truss.

Evenly distributed capacity, 10’ span:
12” Modtruss: 9636 lbs
12” Tomcat: 4909 lbs
20.5” Tomcat: 6200 lbs

Center point capacity, 10’ span:
12” Modtruss: 6286 lbs
12” Tomcat: 2483 lbs
20.5” Tomcat: 5289 lbs

Capacity per pound of truss: (based on center point load @ 10’ span)
12” Modtruss: 6286 / 95.5 = 65.82 lbs
12” Tomcat: 2483 / 60 = 41.38 lbs
20.5: Tomcat: 5289 / 69 = 76.65 lbs

Now I'll stop here for a second. One place where the modtruss shines is in the fact that it is much stronger at short spans, and can support much more weight in a scenario where hanging point load limits and deflection are NOT a significant factor. The mod truss is stronger than even the larger 20.5” truss at short spans. However, if you are not loading your truss to the maximum loads supported by the truss, you can save weight on the structure and still hang your lights needed by utilizing the standardized 20.5” truss. Now, lets see what happens when we have longer spans of truss:

Weight, 40' span
12” Modtruss: 382 lbs
12” Tomcat: 240 lbs
20.5” Tomcat: 276 lbs

Evenly distributed capacity, 40’ span:
12” Modtruss: 2146 lbs
12” Tomcat: 1040 lbs
20.5” Tomcat: 3040 lbs

Center point capacity, 40’ span:
12” Modtruss: 9636 lbs
12” Tomcat: 2483 lbs
20.5” Tomcat: 5289 lbs

Capacity per pound of truss: (based on center point load, 40’ span)
12” Modtruss: 6286 / 95.5 = 65.82 lbs
12” Tomcat: 2483 / 60 = 41.4 lbs
20.5: Tomcat: 5289 / 69 = 76.7 lbs

Here is where it gets interesting. At longer spans, the Modtruss is superior to the 12” Tomcat truss, but it cannot keep up with the 20.5” Tomcat truss. The Modtruss deflects more than the 20.5” truss, weighs over 100 lbs more, and supports 125 lbs less load. Also, another point to note is that the 20.5” box truss provides specsheet data up to 60’ spans, whereas the mod truss only provides data up to 40’.

For me, the choice is clear. For most of my rigging work where I will be hanging truss from an overhead structure, if I need higher capacity than what standard 12” truss can provide, I will opt to use 20.5” truss. There is no benefit to using the mod truss for standard usage other than the cool ability to attach it to itself without the use of grapples. It has a cool design, but that design is not enough to overthrow the functionality of the 20.5” truss the entertainment industry has been using for so many years. 

Wade Cordts

Wade Cordts is a Hollywood based I.A.T.S.E local 80 Key Grip. He is the team lead for the Scene Snipers and specializes in custom rigging, stunt rigging, fabrication, and the unusual.

Facebook: @wadecordts
Twitter: @wadecordts
Instagram: @wadecordts

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