SpudFiles

This cannon was born out of curiosity. First off I wanted to play around with burst disks and secondly my Trinity cannon( seen @ the link in my signature ) has substantial dead space do to it's design. Knowing this I incorporated a union that I could put a burst disk in and also allows me to change barrels. The burst disk will work the same way it does in a combustion cannon, allowing the pressure in the dead space area to build before the projectile begains to move. Well I don't have access to a computer to use ggdt on so I have know idea how much power I will gain. That said... The only way to find out is to test it. Before I could start testing I need a way to test the burst pressure of different disks. So I made a simple 2" burst disk cannon out of spare parts I had laying around. It looks a little getto do to it's scrap bin origins, but to my surprise it is "VERY" loud and pretty powerful.

The cannon...

Chamber: 2" sch 40 about 85 ci
Barrel: 18" of 2" sch 40
Valve 2" union burst disk.


To trigger the disk I fill it to about 3/4 the burst pressure and top it off with a co2 tire inflator.

Nice! It really doesn't get more efficient than that.

What pressures are you using?

Well I tried some of that 20X "stronger" packing tape, but it didn't even burst at 150 psi! The only other disks I've had a chance to try were tin foil. I've taken the foil to 90 psi so far and it sounds like a gun shot. My Trinity cannon sounds like pop-wooosh, this one is just a metallic BANG! I have two grades of foil I still need to test and I will try some foil tape if I can find some. I will likely test up to maybe 150 psi but pvc and anything over 100 psi makes me nervous

I haven't had a chance to get up to my property ( 1/4 mi. square ) to test max range but the velocity out of this relatively short barrel is crazy!

You have a "valve" with near zero opening time, near instantaneous full flow and unlimited dwell time, it's as good as it gets for a pneumatic

My biggest problem now is I'm having illusions of grandeur daydreaming about a 10 gallon pressure chamber and a 40 ft barrel!!!

The worst part is I could probably build one for under a hundred bucks...

In fact I already have a name for it... "Pressure Sensitive"

Edit...
I just found a place near me that sells 3" unions for $22 and I just happen to have some 3" sch 40 looking for a new home. Looks like I might need to start a topic in the Build section in the near future.

Boomer58cal wrote:My biggest problem now is I'm having illusions of grandeur daydreaming about a 10 gallon pressure chamber and a 40 ft barrel!!!

The worst part is I could probably build one for under a hundred bucks...

What are you waiting for

To be honest, you would probably not gain much from supersizing, you might as well go hybrid.

Let's have a look at your delusion on GGDT, firing a one pound projectile at 150 psi:
Now let's look at a relatively modest hybrid, with a foot long 3" chamber and a barrel just one tenth the length of your pneumatic dreams:
... around 20% more energy, in a package compact enough to be fired from the hip taking it to an achievable 10x and with a 750 psi burst disk, HGDT predicts 8,000 ft lbs for this configuration, double what the ginormous pneumatic can do!

Once you go hybrid, you never go back...

Ahh yes...GGDT. I'm working from Ipad and smart phone so I can't use it. I really want to run my triple sprinkler valve gun through GGDT just to see what it say.

Hybrid. I think I'm going to stay low-pressure & hi-volume for the time being. I have black powder cannons for max energy. My current range only safely allows me to shoot about 13-1400 feet. So my goal is to toss the largest projectile possible 1300 feet. I can already get golf balls pretty close, but you only get a glimpse of the ball as it vanishes into the sky. I have to go wander around looking for the balls to see how far they went. I'd like to shot something big enough to see hit. You know, something like a pumpkin or small import car maybe

I have a 65 gallon air compressor so volume isn't a big deal.

Edit...

I just tested some "heavy duty" aluminum foil disks. Of course the results were not what I expected, but isn't that why we test. In the photo below the top row of disks are the heavy duty and the bottom row are made of the cheap-O super thin foil. Well the heavy duty foil holds about 20% more pressure for the number of disks, you can clearly see the heavy duty foil does not open nearly as much as the thin foil. So the heavy duty foil may hold more pressure, but it's restricted flow gives about the same ( or maybe even less ) performance as the thin foil at lower pressure. Interesting.