About as off topic as you can get - gory theatrical explosion; need technical advice.

Theater has become of my biggest non-car hobbies. I'm directing a show in December that's....offbeat, to say the least. The climax of the show is one of the actors exploding into a fine red mist as she stands behind a window (basically behind the set). She's supposed to be outside a bomb shelter, and radiation causes her to 'splode like a melon at a Gallagher show.

Ignore the fact that radiation can't really do that. I think I've developed a pretty good basic idea, but I need help fleshing it out (no pun intended). This show is supposed to be campy and over-the-top.

Non-negotiables: It's got to be a fairly large window- tentatively 4' tall by 3' wide by 4" thick. Budget is low. Like $150. It's got to be a satisfying splat and it's got to quickly obscure basically the whole window really quickly, so the audience can't see that the actor drops out of sight. I've got to be able to take it apart to clean it between shows. It only has to last eight shows. Figure three or four test blasts as well. I would prefer that it's completely (or almost completely) self contained, to minimize cleanup.

My idea is to use a 3'x4' sheet of quarter inch lexan for the front, screwed to a 2"x4" frame around the perimeter , with another sheet of lexan for the back (attachment TBD). A hopper underneath, full of fake blood and stewed tomatoes (or some other viscera substitute). At the bottom of the hopper, a large air line running back to an air tank with a valve. Here's a rough drawing

So - I think the basic idea is good. But here's what I need help brainstorming.

1) I need to put a lot of air into that space (which, by my calculations, measures right at four cubic feet of volume) in a hurry. I have a 21-gallon harbor freight air compressor(this guy) , and a couple of ~5-7 gallon air tanks. I'm not sure that the standard 3/8" connector will let the air out fast enough for what I want to do. I don't know exactly how much pressure I need. If I do need to upsize the air line, I can do that, but I can't butcher my compressor - so I'd have to do it to one of my air tanks. I want enough air to carry a couple of gallons of goop (mostly liquid) up and into the front sheet of lexan pretty quickly and splattily. I don't want to fire a soup of stewed tomatoes and fake blood through the window and into the front row of the audience. Any thoughts on where to start as far as pressure? Am I going to be able to do this with what I have?

2) A vent. Obviously if I can get the air in that fast the air has to go somewhere after it throws the goop at the window. I think a piece of pipe coming out the top of the frame and extending up about a foot, then making a right angle bend and going back away from the back of the set would work, and would hopefully not carry too much goop and liquid with it. The question is...how big? I don't want to spray fake blood out the vent if I can help it, but it wouldn't be the end of the world.

3) General durability. Is this thing going to hold up? Do I need to thicker with the Lexan? Do I need to make a crosspiece for the front/back to help reinforce the middle of the Lexan? I've never really worked with it before, so any tips or tricks regarding cutting it and using it are appreciated.

Any other ideas are welcome. I'm just trying to get the biggest possible bang for the buck.

This, then adjust pressure as required.

https://www.amazon.ca/Tooluxe-30007L-5-Gallon-Capacity-Pressure/dp/B007SWZ7EC

And yes, you need to catch the overspray somehow.

Second the cheetah

Can you build a perimeter around your window to do the catching, so you can have the whole thing sealed of? Sort of like a 6" or so in all dimensions wall that the window is framed into, so the spray has somewhere to go but can still be contained.

Firecracker inside a watermelon.

Would you be able to accomplish some equivalent by just dropping a splattered sheet of lexan like a window blind (or guillotine!) and using a sound effect?

It would be easier to clean up, and likely more repeatable.

Lighting will be important regardless, may take some tricks.

Instead of standard air tanks, look for confetti cannons. They have larger ports to move more volume of air more quickly.

I have no suggestions but am interested in what you do. I could see some uses for this around the house. Some Gallagher Ponchos for the first few rows might also be a good idea.

Streetwiseguy wrote: This, then adjust pressure as required. https://www.amazon.ca/Tooluxe-30007L-5-Gallon-Capacity-Pressure/dp/B007SWZ7EC And yes, you need to catch the overspray somehow.

Holy E36 M3. That's PERFECT. It breaks the budget (I'm already going to be into this for ~$100 just to build the window) but it's something I could keep around after the fact. I'm not sure how often I'd use it, but I have had use for it more than once in the past (and resorted to using the starting fluid trick).

Karacticus wrote: Would you be able to accomplish some equivalent by just dropping a splattered sheet of lexan like a window blind (or guillotine!) and using a sound effect? It would be easier to clean up, and likely more repeatable. Lighting will be important regardless, may take some tricks.

That's a thought. Repeatability will be nice, but I don't know there's any way to drop it in fast enough without it being obvious that we just dropped a sheet of lexan into the middle of the window. It's supposed to be very sudden and unexpected when she blows up, so I'm not sure how we'd light that to make it work. Also, I kind of like the idea of the goop splatting against the window.

Easier to sketch than explain:

cmcgregor wrote: Can you build a perimeter around your window to do the catching, so you can have the whole thing sealed of? Sort of like a 6" or so in all dimensions wall that the window is framed into, so the spray has somewhere to go but can still be contained.

It'll be contained, yeah, I've just got to have somewhere for the air to go, preferably while taking as little of the goop with it as possible. I can't go straight up with an exhaust, because the flats comprising the back wall of the set are only going to be 10' high.

Shotgun?

oh and we're gonna need pics/video

let me know if you can't read my chicken scratch.

In reply to bluej:

The more I think about it, I may be overthinking it on the vent. if I just have the vent come off the top , do a U-turn, and then drop into a trash can, that'll at least contain the overspray so it doesn't go anywhere, and I think we could even reuse it.

Good idea on the trap on the air line, though, and I like the idea for attaching the lexan to the frame.

Somebody check my math.

My window is (roughly) four cubic feet of volume inside.

One of those 5 gallon bead breakers @ 90 psi will hold 450 gallons of air at 1 psi. 1 gallon = 0.134 cubic feet. 0.134x450=60.3 cubic feet at 1 psi, or 4 cubic feet at 15.075 psi. This is all just simple math, right?

So at worst one of those would put a "shockwave" of ~15 psi into the box before some escaped out the vent, right? That seems like a workable amount.

Now, is it enough to throw all of the goop out of the hopper?

Oh, and you'll all get video. Whether it works or explodes, it's gonna be on Youtube.

This isn't your alibi for the missing homeless people investigation going on in your area is it?

Is your theater really small? I think you are going to need a bigger window to do this with, or only the people in the front will even see it.

psteav wrote: In reply to bluej: The more I think about it, I may be overthinking it on the vent. if I just have the vent come off the top , do a U-turn, and then drop into a trash can, that'll at least contain the overspray so it doesn't go anywhere, and I think we could even reuse it. Good idea on the trap on the air line, though, and I like the idea for attaching the lexan to the frame.

yeah, trashcan might be easier than the PVC tube I was thinking, but similar idea (open top cylinder). The thought w/ the lexan is that you'll be able to access the fasteners from the rear pretty easily to remove and clean the window chamber. I think you'll want a double row of fasteners for sealing purposes.