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What would you Guys build?

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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What would you Guys build?

Unread postAuthor: High-PSI » Sun Oct 30, 2011 2:54 pm

Hey Guys,

I have a couple brass Granzow diaphram (sprinkler style) valves lying around. One is a 1 inch pipe thread and one is 1 and 1/4 inch thread. I am considering building a 1/2 inch aluminum barrel gun with the 1 inch valve. This will keep the CV up beyond what is "Needed" for a 1/2 inch cannon. This will be an all metal cannon that will be running a minimum of 300 psi.

What I am curious from you guys is this;

Should I build a cool assault looking rifle with decent performance, or ignore the cool factor and push for the highest possible performance (super long barrel, high tank/barrel ratio, crazy high FPS)?

What would you guys build?

Matt
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Unread postAuthor: wyz2285 » Sun Oct 30, 2011 3:17 pm

What would you guys build?

I build what I need.
For a assault rifle it´s better multi shot at least.
If you get only one shot, I´d make it a cannon.
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Unread postAuthor: jrrdw » Sun Oct 30, 2011 3:17 pm

push for the highest possible performance (super long barrel, high tank/barrel ratio, crazy high FPS)


Gets my vote.
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Re: What would you Guys build?

Unread postAuthor: MrCrowley » Sun Oct 30, 2011 3:38 pm

High-PSI wrote:or ignore the cool factor and push for the highest possible performance (super long barrel, high tank/barrel ratio, crazy high FPS)?
Build a hybrid :D

IMO, small bore, high pressure pneumatics get pretty boring pretty fast, especially if they are just one-shots. Use the valves to pilot a much larger valve, like a 4" piston valve :wink:
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Unread postAuthor: High-PSI » Sun Oct 30, 2011 3:43 pm

OK, that is kind of what I was thinking.

This will still be a hand-held rifle. But, I am leaning toward making a couple different barrels and tanks that can easily be interchanged. I already have all the materials on-hand. The grip, pilot valve, and trigger will all be mounted to the vavle. That way the tank and barrel will be super easy to change and it will be easy to disassemble for service, and easy transport.

Hmm, It would be cool to make a super long barrel. Like 10 foot or more and see what kind of velocity I can achieve. I bet super-sonic would be possible with 300 PSI and a 7 or 8 gram light weight plastic slug.

Anyway, I am so used to making stuff that just looks cool. However, I really want something that will impress. It is tough to make a small bore cannon do much damage. I think this is a worthy challenge. Besides, I already own everything I need to do this.

Matt
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Unread postAuthor: MrCrowley » Sun Oct 30, 2011 3:47 pm

High-PSI wrote:It is tough to make a small bore cannon do much damage
Hybrid :wink:

You really have to try hard with a pneumatic to get them to transonic performance levels. With a hybrid, supersonic velocities are so easy to achieve it's the norm and mach 2 is the challenge :wink:
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Re: What would you Guys build?

Unread postAuthor: High-PSI » Sun Oct 30, 2011 3:47 pm

MrCrowley wrote:
High-PSI wrote:or ignore the cool factor and push for the highest possible performance (super long barrel, high tank/barrel ratio, crazy high FPS)?
Build a hybrid :D

IMO, small bore, high pressure pneumatics get pretty boring pretty fast, especially if they are just one-shots. Use the valves to pilot a much larger valve, like a 4" piston valve :wink:


I know, I know. My 2 inch cannon is a blast (pun intended). It disintigrates 4 inch concrete cinder blocks. It kicks the shoulder enough to border on painful, is impressive to look at, and is super loud! But, I think it is cool to have something that does not weigh 35 pounds and take 3 minutes to charge the tank.

Oh, also, I can always have a 1 inch barrel on-hand for some larger projectiles. It is, after all, a 1 inch valve........

Hmm, I have that 1 and 1/4 inch valve too. I should build two cannons while I am at it. I am very familiar with these valves and the particulars related to welding the tank together and everthing else. So, this should not take too much time to build.

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Re: What would you Guys build?

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Unread postAuthor: jackssmirkingrevenge » Sun Oct 30, 2011 11:48 pm

I'm with MrC on the hybrid comments.

If you want to stay pneumatic, make it a multishot. Seeing what you're crafted in the past you certainly have the tools and materials to pull it off neatly.
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Unread postAuthor: High-PSI » Sat Nov 05, 2011 5:57 pm

I have a basic 3 foot long barrel .6" bore cannon built (I have no pictures of it yet). I used my 1 inch bore brass diaphram valve pilotted by a 1/2 inch diaphram valve triggered by a small air trigger valve I picked up from McMaster. The tank is a .1 inch thick steel affare welded together. The tank is 3 inch diameter, 5 inches long. I have fired it a few times with pressures ranging from 200 to 300 PSI. It is loud, I can tell you that. It is, also, very powerful for a small bore cannon. I fired it through a few sheets of aluminum plate I had lying around. I need to fire it into some plywood sheets to see how much penetration power it has. All I have left is the grip and a simple shoulder stock to make. Oh, I have a 6 foot barrel for it too. It should freakin ROCK with that long barrel! But, it would be weird to carry around with such a long barrel.

Oh, my compressor can charge the cannon to 100 PSI in 5 seconds, 200 PSI in 12 seconds and 300 psi in about 25 seconds. Much better than waiting 3 minutes to charge like my big cannon. Of course, the big cannon is much more impressive to fire. :)

At any rate, I am pleased enough with this cannon that I am going to take my time making the grip and stock.

Hey, one interesting observation, I innitially installed the trigger air valve directly to the pilot chamber on the main valve. However, the performance was seriously lacking. I jsut could not dump the pilot volume nearly fast enough. So, I added the 1/2 inch bore pilot valve. Holy cow, that made a HUGE difference! I know pilotting a valve increases opening speed in most instances. That is a given. However, I had no idea it would make such a difference on a relatively small pilot volume valve. This thing rocks!

I cannot wait to setup a test rig with the 6 foot barrel and break out the chrony.

Matt
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Unread postAuthor: jakethebeast » Sat Nov 05, 2011 6:26 pm

i like the look on your 2" in cannon, if i was you i would make a "little brother" to it, just scale it smaller but stilla large enough to shoot comfy. with 1" barrel you dont need so large air tank so it will be faster to reload :)
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Unread postAuthor: High-PSI » Sat Nov 05, 2011 6:31 pm

Well, it does look like the little brother cannon by default because the system is pretty much identical, but scaled down.

It will look very similar to the big cannon in other respects too.

Speaking of the big cannon, I am dismantling it soon to have the barrel and other aluminum bits anodized and the steel parts powder coated. I may wrap the tank in carbon fiber too. We shall see.

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Unread postAuthor: High-PSI » Sun Nov 13, 2011 2:09 pm

Hey guys,

I have a 400 psi compressor coming and I was wondering if someone here could run the numbers on this for me.

My gun is a 1/2 inch pipe barrel, three feet long. The valve has a CV of 14. The tank to barrel ratio is 3 to 1. The PSI is 400 and there will be two different weight slugs I will be firing, 8 gram plastic slug or a 20 gram metal slug.

I am curious what the predicted FPS would be fore each and the power.

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Unread postAuthor: warhead052 » Sun Nov 13, 2011 2:13 pm

You forgot the chamber size. And will it be pneumatic or electric pilot?
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Unread postAuthor: jackssmirkingrevenge » Sun Nov 13, 2011 2:18 pm

warhead052 wrote:You forgot the chamber size.


High-PSI wrote:The tank to barrel ratio is 3 to 1


... so around 21 in<sup>3</sup> ;)
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Unread postAuthor: High-PSI » Sun Nov 13, 2011 3:01 pm

OK Guys,

This is a 3 inch diameter tank that is 5 inches long.

It uses a 1 inch pipe thread fast acting valve that is piloted by a 1/2 inch electric direct acting valve.

I actually got my GGDT running finally........

However, it asks for valve open time and dwell time. I assume the open time is how long the valve takes to open fully and the dwell is how long it stays open?

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