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Discussion Starter · #1 ·
I'm planning to hang my CRT (Barco 808) from ceiling joists using unistrut but I have those joists that are made out of 3 separate pieces of wood ... they are not solid pieces of wood. I think they are known as "quiet" or "silent" joists.


Is this okay? The 3-piece joists seem a bit more frail than the solid kind.


And, has anyone done this? I'm not entirely sure what the best way to attach the unistrut to the joist actually is.


Thanks for any help you can give me.


c
 

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I hung my Barco 1208/2 from two engineered joists, sound like the same thing you have. They look like a wood I-beam. I used long lag screws that went through the bottom plate and into the vertical a bit. Details here.
 

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I believe for engineered floor joist you will need a couple of hangers that "top" load the joist. Difficult when your floor above is already installed.


Your PJ is maybe 180 pound dead load/point load. The softwood rail I don't believe was designed for anything more than drywall at
 

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Discussion Starter · #4 ·
Chris, that's *exactly* what I have...thanks for the pics! Helps tremendously. How far into the verticle part of the beam were you able to get the lag bolts?


AJF, thanks for the tip. I'll go check out their site.


c
 

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If anyone wants to transfer the load from the bottom chord of a wood I-beam to the top chord, you can use perforated steel strap. Pre-drill each side and use lag bolts or use a nut-and-bolt combination (if you drill all the way through, but the flooring above makes this difficult in the upper holes).


The same methods can be used at the bottom, and you can even use a single strap in a U-shape to go down one side, wrap under the bottom, and up the other side. If it's tight, you don't need lower bolts. A couple of L-brackets can even allow you to attach your strut to the strap itself as well as the wood.


Something like this (but I didn't include the L-brackets):

http://www.fineelectricco.com/Joist.jpg
 

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I used 3/8" x 3-1/2" lag bolts with washers, so they went into the vertical by about an inch. As I see it, I used two 4' lengths of powerstrut directly lagged to the bottom of the joist with 8 bolts each. The strut is pretty stiff and distributes the weight well. With a 160 lb projector, that works out to approximately 10lbs per lag bolt. Even if you say the bolts closest to the support points carry twice the load, that's only 20lbs per bolt.


Mine's been up for well over a year, without any signs of distress.


Larry's idea is a good one.
 

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Discussion Starter · #7 ·
Fantastic. I know just what to do now. AVSForum comes through again ;-)


One last question...I always see these nearly 200lb projectors held up by 3/8" threaded rod, and often just at four points. Is this stuff really that strong?


c
 

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Yes. Just don't use thin nuts.
 

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3/8" carbon steel threaded rod (Power-Strut brand) has a load rating of 610 lbs. For a 200lb projector suspended by 4 rods, each rod will carry 50 lbs, for a greater than 10x safety factor. If you go to 1/2" rod, the rating increases to 1,130lb.


I used lock nuts to back up all the rods and at the connection to the projector.


If I had to say what I think the weak point in the unistrut mounting method is, its the mounting bracket on the projector. The strut, lag bolts, rod, and hardware seem much beefier than the aluminum sheet stock used on the projector.
 

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Discussion Starter · #10 ·
610lbs each? Yeah, I guess that should do it ;-)


I'm hoping to put the PJ up next week so I'll let you guys know how it goes.
 

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BE CAREFUL!!!!! A few words of warnings about the engineered I-beams:


1. A majority of the load carried by the i-beam is done so by the lower flange (bottom of part of the beam). Be careful not to damage(cut/notch) this or a building inspector might make you replace the beam. There are a lot of "do's and don'ts" when altering this product. You should look at the manufacturer's website to see if your alterations are safe.


I would think twice about sinking lag bolts directly into the flanges... especially the one at the bottom. Splitting the bottom could potentially be very costly, as it would compromise the entire beam.


A better option would be attach some blocking/sheeting to both sides of the webbing (ie. the middle OSB portion of the beam) and make your additional connections there. (Preferably towards the middle, definitely not at the flange/web junctions). The manufacturer of my joists had recommendations on how to best do this (nailing pattern/spacing, and type/size of nail to use).


2. If your projector mount hangs on only one beam, make sure that there is not any induced-lateral rotational stress on the beam. It is better to brace this beam to prevent torque by blocking or headering to the neighboring beams. These critters can twist very easily if not properly braced.


3. These beams can carry a lot of weight. You should not be worried about the extra weight of the projector too much. Spread the load to the neighboring joists if you want to be cautious.


Good luck and be safe!

here's a link to a manufacturer's website-see installation pdfs for more info!
 
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