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Shooting Streamers, Home-made version


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Hi guys!

I'm currently in high school, and I'm working on some special effects for our up coming show, Little Shop of Horrors. Its coming along well, but I'm stuck at one part. For anyone who doesn't know what the shows about, it basically tells the tale of an alien plant and its conquest of the world via the manipulation of an insecure, love-sick botanist. In the end of the musical, the last song goes into a dramatic tale of the plant taking over the world, and after listing a couple of places, it hits a long minor chord on the words "and this theater!" The script calls for drop boxes above the audience to drop down vines at this point, but I want to take it a step further. Down the length of the theater, there are two ventilation ducts, I was planning on having, somehow, green streamers shoot out over the audience, in a rainbow like fashion, from on top of the ducts. I was planning on having a long tube of PVC running down each duct, with holes drilled into it, and mini-barrels sticking out, each packed with the streamers, then have each PVC pipe connected to an air-hose, which runs behind stage over to an air compressor outside.


Now, before I go out and start gathering the supplies for my crazy contraption, I was wondering if any of you guys have any suggestions, because I'm afraid I might just be wasting my time. For some reason, I feel like either I wont be able to generate enough PSI (maybe use two compressors?) or the streamer will get lodged into the "mini-barrels" and will fly out as wads. I know some of you guys have some experience working with streamers, and I'd love to hear your guys' thoughts, ideas and feedback!


Hope to be talking to you all soon!


(ohh, and by the way, do any of you know how much it'd be to rent some moving head lights? ** laughs out loud **)

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jaket, you're brave for posting something like that on the BR! But welcome anyway.


To summarise the following 5000 posts: It's unsafe, it'll cost more than you would spend hiring air cannons, do you really have any authorisation to make this happen, you'll have a hard time getting home made air cannons through a risk assessment, why don't you just hire them, why not go with the drop boxes, if you don't know you probably shouldn't be doing it, can you please add more information to your profile because we think you're a 14 year old with big plans.


Anyway with that out the way onto the technical.


First rule of designing things is to see if someone else has done it already and just go buy theirs. 99% of the time it will save you money. If you're dead keen then fair enough but don't say I didn't warn you. Second rule of design is that if someone else has done it, copy their design. Go and look at every scrap of information about air cannons and then copy all the common parts. How would I do it? Firstly, don't try to run it all centrally, it's not worth the trouble.


To get any sort of projection you're probably going to want a burst disk in each barrel to allow the pressure to build up before the streamers fire. Probably best to just buy them from a manufacturer otherwise you're going to have a hell of a time getting them consistent. Same goes with streamers.

Get one air tank for every 2 or three cannons, run the hose to a solenoid valve (it needs to be big bore), from there to your barrel with the burst disk and streamers. Fire them electrically and make sure you close the valves quickly otherwise it'll sound horrible. If you find that the barrels are firing inconsistently you'll need to mount one valve per barrel. Just make sure you have a decent receiver directly behind the valve so you're not trying to pull a huge flow through a small pipe. If you have big enough valves you can probably get away without the burst disks and mount the valve directly on the barrel (it needs to be direct and needs to be a very big valve, still needs a receiver behind the valve).


Once it's all built you're going to need to risk assess the hell out of it, get parts of it certified and then pay off the loan you took out to buy all the gear. I'll leave all the other safety related issues to the more knowledgeable members. For my money, just hire a couple and mount them on the stage and perhaps up the back.


Artistically do you actually want it to look like a rock concert? I haven't seen the show but I imagine you're trying to create a spooky or creepy effect. Having a heap of compressed air blasting away from the grid might just make the audience think that Justin Timberlake is about to bust out from DSR.


Good luck

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I did exactly this quite a few years ago, and there was a handy aircon duct running centre auditorium, front to back. I came up with clever systems, but in the end, we built some mdf trays, about 100mm wide and high, and 1.2m (for less cutting) long. These were hung either end so they could spin. We secured them with straps around the duct. Each had elastic that would spin them around to dump the contents, and they were held against the tension with a pin - with havy fishing twine leading to the follow spot gallery at the back. A hefty tug, and they all spun around, dropping the tendrils. Worked fine and very low tech.


Draw back was it took ages to put them back. Because of the seating, getting the ladder in, and resetting them was a nightmare, because you need to basically move the ladder about a row at a time, because you need to get to very specific locations around the tray. If I did it again, I'd make the trays removable, or have some kind of easily secured inner tray that could be reset at ground level, and then simply dropped in. The effect was really great, but spending nearly 3 hours each morning was not good use of our time.

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Sounds like it could be a great effect, also sounds expensive, and a lot of work to reset... but perhaps that is something which you can cope with for the result.

We kept this much simpler when we did LSOH, with a snap lighting cue to bathe everything in red on "and this theater", which I think worked really well. Perhaps not quite the wow factor you're looking for, but no nasty reset after every show!

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