Underwater FX With Oxy-Propane/MAPP

[ammosmoke]

Hey all, maybe some of you remember me. I haven't posted in a while.

Anyway, I got bored in English 102 today, and started doodling. This is what resulted.



I need a cheap way to get some loud booms in my 4th of July show, and loud booms are, well, spendy to say the least when it comes to consumer pieces. My show was 9 minutes long last year, and it rocked, but it lacked in boom if you ask me.

Now, I'm not sure how far underwater I want to place these. It has been my experience that water deadens sound significantly. I'm not sure how much noise one of these would make. The tin I had in mind is coated cardboard with a metal bottom and probably an LDPE lid. I could probably just put the top at the surface. Would make a great flash and kathunk sound.

My other idea was basically a thundermug, for all you who know what that is, but instead of using solid propellant, it would use the mix and it would be electronically ignited. My only question about that would be, is SCH40 steel enough, and should/how might I ground it to avoid accidental ignition?

BTW, the BLOCK is anchored so I can get it back, not the device.

Final question... What oxy:propane ratio should I use?

EDIT: The tins I have available are around 14oz and 32oz sizes.

[jrrdw]

Yes, we/I remember you... All I can say here is be very very careful because most of the time trapping gases less can be more.

Not only your safety is in concern here but there will be people with you and you have to think of them as well, also the property where you will be doing this if it's not your property.

Quietly waiting for the scientific math to appear...

[ammosmoke]

Yes, I'm being sure to be careful. That is why they are underwater and electronically ignited from a distance.

[psycix]

Why a tea tin?
I'd use PVC chambers, with an union to hold a burst disk.
This might will hold your gas better for a long time.
Heck, trow in metal pipe and make it a hybrid.

While you're at it you can throw in a few spudgun tricks like metering (you will only need one meter for multiple chambers) and multiple spark gaps.
Most important for a fast burn (thus loud bang) is a method to mix.
A fan will get wet, so you might try the "chamba chain" or something similar.


----

Propane: C3H8
Oxygen: O2

When propane is burned: 3 CO2 4 H2O
This requires one mol propane, and 5 mol O2.
So the ratio would be 1:5
Thus 1/6th propane, 5/6th oxygen or, 16.67%, 83.33%

[jeepkahn]

One concern would be the poor innocent fishies that will be collateral damage, if this is a pond or lake...

[ammosmoke]

Why a tea tin?
I'd use PVC chambers, with an union to hold a burst disk.
This might will hold your gas better for a long time.
Heck, trow in metal pipe and make it a hybrid.

While you're at it you can throw in a few spudgun tricks like metering (you will only need one meter for multiple chambers) and multiple spark gaps.
Most important for a fast burn (thus loud bang) is a method to mix.
A fan will get wet, so you might try the "chamba chain" or something similar.


----

Propane: C3H8
Oxygen: O2

When propane is burned: 3 CO2 4 H2O
This requires one mol propane, and 5 mol O2.
So the ratio would be 1:5
Thus 1/6th propane, 5/6th oxygen or, 16.67%, 83.33%

Wouldn't the PVC shatter? I was just thinking of cheap things that would be non-static conductive. I don't actually know how much of a concern static sparks are. But I don't want to have one go off near me. That would suck. I was going to meter them yeah. Probably use the meter system found here that homedepotpro made, and it was also used by starman. Thanks for the ratio!

One concern would be the poor innocent fishies that will be collateral damage, if this is a pond or lake...

Meh, it's all yellow perch that side of the lake anyways. I hate those things.

[starman]

You're going to lose some sound being underwater...anything magical about being underwater?

It's really hard to beat the noise trip thunder makes with 3" burst disks...and only with 1x MAPP mixes. If you were to go with some hybridization, you would have some really wicked booms....make sure the shooter wears hearing protection.

To get louder than that, you'll need to go to those black powder noise mortars or calcium carbonate cannons....yes they are all metal.

[CS]

Starman, I'm guessing something between a geyser-ish effect, and fire safety.

Floating a ThunderpipeFX1 type of launcher so that only a small amount of barrel is exposed would be neat. Watch the videos!

Somewhat unrelated, but anyways:
Used to dunk the ends of pneumatic launcher barrels in the pool and it makes a low-pitch thump. If you got enough pneumatic launchers and such you could synchronize the firings to the base line of music. Pool party!

Easily marketable to rappers.

(Psycix you will be resourced for music and shufflers, lol. Still recovering BTW. I look something like this.)

[starman]

Starman, I'm guessing something between a geyser-ish effect, and fire safety.

Yeah thought of that...he was just emphasizing booms in relation to music and not the water spewing possibilities.

[Moonbogg]

If you were to go with some hybridization, you would have some really wicked booms

You can sure as hell say that again. Large hybrid dry firing is friggin loud, even with a barrel, lol.

[ammosmoke]

Thanks for the response guys. I have revamped the idea, and it was actually similar to CS's. I think I'll make a small floating platform that has steel guns (3" sch40?) in it, and most of the chamber underwater. The reasoning is that this shoot location is owned by my friend's parents, who are safety freaks. That said, I'm not sure they would ever let me fire a thundermug. (Plus, I don't want to buy one because they are so darned expensive.) But, I could probably get their approval if the chambers were underwater, because even in the event of failure, nothing would happen to anyone. The guns would use a vinyl tape burst disk most likely. Or maybe a tea tin lid, who knows...

Starman, I was indeed looking to your triple thunder's for inspiration. My hat is off to you as far as those go. I'm vying for something a little more simple, because, well, they aren't going to be about looks, just noise. How would you guys suggest I fill these suckers? I don't want to have any weak points, such as fill valves, that would potentially pop off. I don't know if I'm just being paranoid, or if I have a legitimate concern...

[inonickname]

Rather than a combustion solution, why not a pneumatic one? Should be less of a problem if his parents are safety freaks.

Simply obtain 10 empty, clean coke bottles (and lids) and a handful of schrader valves. Drill holes in the caps and press fit in the valve (yes, you can use the opposite end of the bottle if you wish). Simply drive a spike through them to set them off. Extremely loud, though using them underwater would need adaption.

[ammosmoke]

Rather than a combustion solution, why not a pneumatic one? Should be less of a problem if his parents are safety freaks.

Simply obtain 10 empty, clean coke bottles (and lids) and a handful of schrader valves. Drill holes in the caps and press fit in the valve (yes, you can use the opposite end of the bottle if you wish). Simply drive a spike through them to set them off. Extremely loud, though using them underwater would need adaption.

Pneumatics is a valid solution.... I'm kinda leaning toward reusable. Perhaps an electronically fired (electronic pilot) valve of sorts.... A short barrel, and burst disk setup should be pretty darn loud. Especially if it were an HDPE container lid.

EDIT: About the thunderpipe thing... How exactly does that ignition work? Does it have a stungun gap or something on the same circuit as the valve release?