Connecting a short piece of truss using single truss poles

[Jamtastic3]

Hi BR,

 

Dilemma here. I have a piece of truss which is about 50 cm short of joining to the rest of an exisiting truss structure. Can I use single truss poles like this...

 

http://www.thomann.de/gb/stairville_traver...962b81f1c956da0

 

... to fill the short gap? It looks like I can add 3 of these onto the male end of the truss by pin attachment. The end of the poles (being female) doesn't matter as I can clamp this to the existing truss (being female at that end).

How would this affect weight loading on the piece of truss at the pole joins. Would it be safe for a few moving lights and some parcans for example?

This short truss spans the centre of the stage and is roughly around 8ft from stage level.

 

Thankoo!

[paulears]

There are two things to consider. Unless you can get the real specs from the supplier that will show clearly the strength of the tubing, you will have to either test it, or carry out some kind of assessment based on your knowledge and experience. It isn't clear from your post exactly how the 'wrong' end will be attached to the truss.

 

In the past (I couldn't find it) we had a topic about outriggers on truss, and the discussion as I remember it centred on the connection method of the new tube to the truss. Double doughty type clamps were favourites - allowing extension along the plan of the truss chords, or at 90 degree to them depending on where the clamps are placed.There was comment on the 'twising' of the truss, but this won't apply to your situation. Cheap, lightweight truss gains strength from the combination of multiple tubes with the cross bracing. A single piece of truss tube isn't that strong. If you need to hang mover style weight, I'd have a problem assuring myself it was safe. Why not just use a length of steel scaff pole. Heavy, but much stronger, and clamped properly to the truss would deem far safer than a bit of tube with probably 2mm wall thickness. A self-supported span of this can even split if the length is too great and the weight too much - and you'd have to break a bit to find out how strong it is - you can't guess. An over-stregth bodge is much better than a weak one.

[Bryson]

I'm confused about why you can't use a 50cm piece of truss?

[Jamtastic3]

Paulears, the truss that exists is the 3 pole (triangle) sort. I don't know the brand of it as I was only given the pieces to me. The top of the structure has created a sqaure 8ft above the stage yet somehow I've ended with this 50cm gap at one corner. So could you not say that using 3 poles and not just one to bridge this gap would be sufficiant?

Steel scaff is not an option and I need a pole that has truss holes in them so I could pin it up with the short piece of truss.

That's when I remembered Thomann do single truss poles.

[Andrew C]

As I see it, most of the strength in a truss comes from the 3 dimensional, braced structure. If you fill in the 500mm gap with single poles, this part will be weak, and your design calcs/loading tables will be worthless. You would need an engineer to calculate permissible loading. Much cheaper to find out a) why you have a gap and rectify the problem, or b) as Bryson suggests finding a matching piece of proper truss to fill in.

[Ynot]

Paulears, the truss that exists is the 3 pole (triangle) sort. I don't know the brand of it as I was only given the pieces to me. The top of the structure has created a sqaure 8ft above the stage yet somehow I've ended with this 50cm gap at one corner. So could you not say that using 3 poles and not just one to bridge this gap would be sufficiant?

Steel scaff is not an option and I need a pole that has truss holes in them so I could pin it up with the short piece of truss.

That's when I remembered Thomann do single truss poles.

I'm a little confused....

You say your truss forms a square, BUT unless you have different lengths of truss then there must be something putting that square out of true. And if the square is out of true, adding an extra half-meter of even pukka truss section is going to KEEP it out of true, thus putting undue stress on the sum of all joints.

If this were for just a handful of par cans, you MIGHT get away with the job, but as you mention 'a few moving lights' I for one wouldn't be happy to trust the truss....

 

If, however, you DO have unequal truss lengths, then I'd suggest you revisit the supplier and get a replacement length the right size.

[Jamtastic3]

Cool, thanks for the advice guys.

Yeah the truss I have been given is strangley unequal at one end though these were the pieces that originally existed, I was just adding the 4th edge on the square structure that were left lying around, however, plans can be altered so the shorter length can just come down now.

 

Cheers!