Cheesboro cantilever question

[Mistermon]

Hello CB,

My Auditorium is in the midst of a major renovation and I'm having a bit of anxiety about the way some things have been rigged... specifically, I have two torm positions (HR and HL) with only vertical pipe.

In the past, I've used cheeseboro clamps with a cross pipe and an evenly distrubuted load left and right of vertical. The contractors (who are a legitimate company) installed the clamps and pipe, but hung 90-95 % of the pipe to the on stage side of vertical. (making the pipe look like an L instead of a T) Overall length of the cross member is about 4 feet. Hanging on the cross pipe are 2 source 4 LEDs.

Is this a safe way to hang these instruments? We didn't take possession of the space yet, so there is no immediate danger to injuring anyone, but I want to ensure it's right before we do. I'll try to get in and snap a few pictures to give better idea what I'm talking about.

Thanks for the help you always provide,
Rob

 

[egilson1]

Steel or aluminum clamps? Do you know the manufacturer of the clamp?

 

[Mistermon]

Clamps are aluminum. Purchased them from production advantage about 5 years ago.

 

[egilson1]

Assuming they are the light source 90 degree fixed coupler then they use a roll pin to keep them ridged. So the sheer strength of the pin is what is keeping the pipe perpendicular to the vertical pipe, which is not a lot. I wouldn't do it that way. I would center the 4' pipe so the load is symmetrical, or if that is not an option I would change to a different clamp. The ultimate solution is to do a Mega Side arm which is rated at 150 lbs at 24". They do make a 36" version. http://www.thelightsource.com/products/mega-sidearm-fixed-126

 

[Mistermon]

Thanks egilson.

That is how my initial installation was and my thought as to how it should have been done. The contractors, "allegedly" ETCP certified riggers as well, had some other glaring installation mistakes so I wanted to verify.

 

[BillConnerFASTC]

I just posted this elsewhere but I was at the Booth Theatre Sunday and all 6 box booms were loaded with side arms - I'd say 6 to 8 on each boom - looked like The Light Source but could have been other - with about 4' of pipe and three units - including LEDs and movers - hung from each side arm. Looked fine. Everything was saftied of course. Doesn't account for the particular cheesborough in your install but the concept is not incorrect. For fun the Rose Brand fixed cheeseborough tech data suggests it up to the task - with minimal deflection at upwards 2000 pounds and perhaps failure in the 7000 pound range. http://www.rosebrand.com/downloads/cheeseboroughw1.pdf I have used rota-locks this way and have no hesitation.