Creating Truss System with PVC pipe

Factual Questions
1

Hey Guys,

I’m currently in charge of production of a pro wrestling movie.

We are looking at cost efficient ways to create an truss system. After crunching the numbers this is what i came up with.

We have 4 - 20ft stands

Each stand would be ~ 30ft apart connected via 3 - 10ft sections of PVC pipe. Holes would be drilled, lights mounted…the amount of weight the lights would add would be about 60 pounds.

My question is, what would be the best way of spanning 30ft with PVC pipe? I have not worked with it too much, would it be rigid enough to not create noticeable bends along the way?

What thickness would be recommended?

I would also need this to be disassembled so gluing all pipes together is not an option, they would need to slide into a connector and be able to slide back out.

Thoughts? Opinions?

2

it won’t work. it will sag, it will break, it will fall down.

metal tubing is used for trusses because it works.

3

Don’t have anyone stand under that thing, much less climb on it.

4

If you want to try something really unconventional, see if you can find someone who knows how to build tensegrity structures. The PVC pipe could be used as the compression members with wire cable providing the tension.

5

You ‘could’ make a nice sturdy truss with PVC. But use metal.

6

Yeah, the PVC won’t even support it’s own weight without sagging, let alone lights.

7

Just rent it from a lighting company for the shoot. You can write it off and they’ll load in, set up, strike and load out for you.

8

The trouble with a “truss-bridge” is to do this:

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PVC pipe AFAIK does not have 3-way pipe joints at 60-degree angles,
SO where the 3 pipes meet, you actually have 2 pipes meet and then you glue that to the next triangle with a very very short pipe.
That very short connection is a serious failure point.
It’s worse than that, because the long flat truss would bow sideways and fail too.
You really need a box or triangle truss, like the long arm of those cranes on hi-rise buildings.

PVC six-way or 8-way connectors don’t exist for sure.

Here’s a different medium-tech suggestion -
A friend of mine built a house where the floor above the basement was “2x4 truss”.
Basically, that was a wood W-truss design, about 15 inches deep with top and bottom 2x4 plates.

On IIRC 18-inch centers he could span about 24 feet (no center posts or beam in the middle of the basement) and still have a normal floor.

He bought these pre-assembled, so I’m sure you could find these too. They should easily support 60lb along the length.
Just be sure
(a) no fire hazard on raw 2x4
(b) anchor securely at ends! (I would use sheet metal straps that wrap around are nailed securely multiple times.
(c) need at least a pair, in box beam configuration with lots of cross bracing, to prevent sidways bowing and failure.

9

This. Renting the real thing might actually work out cheaper than trying to make it out of plastic.

10

Don’t even think plastic.

Cheap steel tubing is known as EMT in the Electrician’s world. The number of end fittings made especially for EMT is limited; however, it is standard size tubing, so any fitting for 1" (my guess as optimal) tubing will work.
If you can find the fittings you need in EMT boxes, it will fulfill your dis-assembly requirements - they (the versions made for amateurs) use set screws.

For pieces loaded in tensions, drill a hole through the assembled pieces (GE EVERY UBE AND FITTING DRILLED EXACTLY HE SAME!!!) and slip a 8d nail (with the head up, duh) or a nolt and nut if the pin can’t be vertical.

By now you have spent the money required to hire real lighting trusses (those fittings add up quick and are heavy.

Learn how to weld Al and by a hole-saw jig to notch the ends with the saddles (“fish-mouth”) notches in the ends.
If want to write-off the learning curve, the cost of the equipment and welding rod, you may come out ahead of a pro rental, but it will be close.

Then again, if you were the type for whom welding is easy, you probably wouldn’t be trying to sonstruct a truss in which every member is loaded in compression and only compression (which your off-the-wall “slip sockets for everything” would require.

For a giggle, get prices:
Pro trusses, including delivery, rigging, strike/pack and removal
Call a local weld/fabrication shop and ask for a off-the-top-of-head estimate for what you want.

FLASH:
Something which might work - with the advent of cable, all those massive antenna masts are now eyesores - put an ad in Craigslist offering free removal of TV and HAM radio towers.
Then hire professional riggers to do the work - that is a tricky job, and no place for OJT - the first time you fall through someone’s roof or cause a mast to crush a kid. you’ll regret not asking the local tree-cutter if they’d like to use a recip instead of chain saw
Of course, those guys don’t work cheap, and you should have foreseen this need 20 years ago and scored them when they were still plentiful. Now you have a deadline.