how do i make a loud cannon

[thebinderguy]

hello all. this is my first post, so thanks for having me. i want to make a loud cannon out of pvc, so i thought i would ask you guys rather than take a chance of blowing myself up. i really dont want to shoot anything, just have a loud noise maker. i attached a link from youtube of a loud cannon (if thats not allowed i apologize), but the result from his actions arent believable...unless there is an aresol plutonium i dont know about.
Anyway, any advice or instructions on building a loud noise cannon would be appreciated.
heres the link.

[jon_89]

My combustion has a 2 inch by 8 inch chamber with a 1 inch by 30 inch barrel and it is pretty loud using propane and firing blanks. You could use a burst disk.

[Combustion Monkey]

I recommend checking out Starmans Triple Thunder

[rp181]

That could easily be done. The place where he lives may offer a good place for echo.
A burst disk is you best bet for a loud noise, or some kind of horn.

[thebinderguy]

can you explain what a burst disk is?

[Combustion Monkey]

It is a disk of material, plastic, tape, or whatever that will break at a given pressure.

And Welcome to Spud Files!

[thebinderguy]

thanks for the welcome.
so this burst disk is applied on the outside?
or inside the chamber?
i dont want to do something dumb like seal it up and have it explode or anything.
as you have realized...i'm a first timer here.

[starman]

can you explain what a burst disk is?

Traditionally, it's configured with a plumbing union mounted inline with the barrel and several layers of aluminum foil tightened into the union. This effectively seals the chamber. Upon combustion, pressure is allowed to build up in the chamber before applying power to the projectile...until...the burst disk breaks and a large pressure wave is then applied to the barrel...very very quickly. This is also a very good thing.

As you may have seen in the triple thunder link, instead of a union, I used camlocks with the male element covered with 3 layers of masking tape. This provides a roughly 65 psi burst pressure.

In noise cannon mode, there is obviously no barrel, just the burst disk. It's like popping a very stiff balloon...and ear splittingly loud!

so this burst disk is applied on the outside?
or inside the chamber?

Read the write up at triple thunder....

i dont want to do something dumb like seal it up and have it explode or anything.

A properly built chamber will withstand and contain a full propane combustion. A burst disk does indeed effectively seal the chamber.

[Gippeto]

Anyone notice anything "unusual" in that video? Admittedly, I've very limited experience with combustions, but...

1) Really short fueling time. (I know this varies.)

2) No apparent burst disk setup.

3) No recoil. (Watch the relationship between the canon and the garbage can.) Maybe no projectile?

4) No projectile + no burst disk (should) = low combustion pressures.

5) Low combustion pressures = low noise.

6) There was a big noise.

Fabrication or is it plausible? Just curious.

Thanks.

[jon_89]

Gippeto I was kinda wondering the same thing. I put that much fuel in my mini. Just joking but really that is a huge pipe and very little fuel.

[Ragnarok]

Fabrication or is it plausible? Just curious.

I'm inclined to agree with you. It sounds too bassy for what it is (although there is clearly also a lot of echo - which in itself is a bit suspicious).

The sound quality is also surprisingly good for the cheap camera. To most cameras, all cannons sound pretty much the same because it overloads what they can record.

I'm guessing he took a stock "cannon" sound effect and layered it over it.

[Insomniac]

Although the dog did seem to react to the noise...
Still, sounds too loud for what it is.

[CasinoVanart]

Fake for sure. No way that amount of fuel can make that noise, period.

[starman]

I will cautiously say the noise heard is mildly plausible. Depending on the geographic location of other buildings, landmarks, etc., the echos could have had an additive effect in the camera. However, this doesn't seem very likely.

The thing that is big negative to me to relative high frequency pitch of the shot..sort of a snap shot sound. I would expect the sound from an open end cannon like that to have a much slower wooof type sound.

I also don't like that there was zero recoil. My cannons have a nice little snap back when they shoot in noise mode.

I discount the small fueling shot he gave it...he could have already fueled it and this was just giving a little topper off'r ... I don't believe that small amount of fuel would have ignited in that large a chamber.

[thebinderguy]

ok i'm going to try the masking tape burst disk. now if i can just find cam locks i'll be all set. i'm glad most of you agree the movie is a fake. i was starting to think i was losing it. Thanks a lot.