SpudFiles

Decided to skip out on piston for my first Pneumatic, Simple going to do what I did for my first combustion, start simple then advance.

The barrel will be changed to sch 40 SDR 21 1.5" sleeved with schedule 80 2" pipe.

If you need more Info let me know =) I'm sure there will be, Drew pics best I could for paint, don't have CAD

Nice design for a beginner spudder like yourself.

Some questions though, to answer your question:
What pressure do you plan on using it at? i would suggest 60-80 until you get some more experience so u dont hurt yourself. And be sure to use pw pipe lol.

And what ammunition do u plan on using and what is its estimated weight?

I've made 3 Combustion cannons starting from hairspray up to my latest direct propane injection.

I Plan on using all presure rated PVC I plan on started at 60 and work my way up. Also If I can get SDR 21 1.5 I'll be usign golfballs if not

I take 1" PVC pipe and tape it with duck tape, Goes straight through 1/2 particle board

Yes, shooting a golfball 250 yrds is fairly easy to do, even without an optimized setup. The 5' barrel will assist getting your distance up some.

Use a modded sprinkler valve. I assume you'll use a 1" valve...not the most optimum setup because of flow restriction to the 1.5 golfball barrel. However, you should still see reasonable performance.

Ya I'll use 1 inch, you think I should make the barrel longer or shorter starman? I'm looking for maximum performance for this setup.

Why not use a burst disk? And I think you will want to double your barrel length.

jon_89 wrote:Why not use a burst disk? And I think you will want to double your barrel length.

I googled burst disk, Do you have a video/animation on the exact workings or a more detailed explanation than wikipedia.

They are pretty simple. What dont you get about them? Type in burst disk in the search section and there are a few of them there.

Burst Disks are easy to understand.

Do you know how you put a drum head on? Its the same concept. You stretch something ove your pipe and tighten it in place. Unions are easy for this if pressures arent too high.

You pressurize the chamber until the burst disk blows which makes all of the air behind it rush out.

If you use a home made one do you have to replace them on everyshot?

That question implies you still dont fully comprehend how a burst disk works.

A burst disk is exactly what its name implies.

it is a disk that ruptures at a certain pressure. Most people use layers of foil.

So to put it easier to understand... put a disc between the barrel and chamber, fill the chamber up with air till the disc gives out and then the air leaves through the barrel.

So yes, the disc needs to be replaced after each shot.

Ok, just confused due to the search online How many layers of foil for 100 or so PSI? I might just make a test chamber

I know for my one inch union one layer bursts about 20 psi. For my 1.5 inch union one layer bursts about 15 psi.

jon_89 wrote:And I think you will want to double your barrel length.

Agreed, with that chamber size you can afford to have a 20 foot barrel if you want. Longer barrel = more time during which the projectile is being accelerated, so if it's range you want then go for the longest barrel you're comfortable with carrying round/manourvering/forking out money for.

jmeyer1022 wrote:Ya I'll use 1 inch, you think I should make the barrel longer or shorter starman? I'm looking for maximum performance for this setup.

As others have said the longer the barrel the better, it's just a practicality issue for you how long...and of course the more PSI the better. Also, the talk of a burst disk for you here is really a moot point because of the fairly significant flow restriction you'll have through the 1" valve. It might help a little but it would be easier to make up the difference with a little longer barrel. Also burst disks on pneumatics are a little cumbersome to setup and get right.