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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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Unread postAuthor: jackssmirkingrevenge » Sat Dec 10, 2011 9:43 pm

Sexeh! Looking forward to seeing it finished :)
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Unread postAuthor: High-PSI » Sun Dec 11, 2011 7:56 pm

OK, I have been working with GGDT and I plugged in the weight of a 1/2 inch Delrin ball. That ball supposedly weighs 1.44 grams. At that weight, GGDT says it will travel over 2,200 fps at 600 psi. I know that may be optimistic (super-sonic numbers usually are). But, it seems obvious that it will be well over the 1,200 fps super-sonic threshold.

Now, that is not what I am curious about. What I am curious about is the muzzle energy that is listed. With a 8 gram slug, the muzzle energy is listed at 240 ft pounds, but with the light 1.44 gram slug, the muzzle energy is listed as 343 ft pounds.

Why would that be?

Matt
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Unread postAuthor: MrCrowley » Sun Dec 11, 2011 8:04 pm

High-PSI wrote:Now, that is not what I am curious about. What I am curious about is the muzzle energy that is listed. With a 8 gram slug, the muzzle energy is listed at 240 ft pounds, but with the light 1.44 gram slug, the muzzle energy is listed as 343 ft pounds.

Why would that be?

Matt

If I remember correctly, double the weight for the same velocity and you double the muzzle energy. Double the velocity for the same weight and you quadruple the muzzle energy.

OK, I have been working with GGDT and I plugged in the weight of a 1/2 inch Delrin ball. That ball supposedly weighs 1.44 grams. At that weight, GGDT says it will travel over 2,200 fps at 600 psi. I know that may be optimistic (super-sonic numbers usually are). But, it seems obvious that it will be well over the 1,200 fps super-sonic threshold.

Yeah definitely something strange with GGDT there. With 600PSI and a slightly better piston valve than in my hybrid, GGDT says 2500fps where HGDT says only 2300fps for my hybrid at a 10x mix (~1000PSI). Both outputs are optimistic, though GGDT more so than HGDT.

I think you will possibly get the delrin ball to go between 1100-1200fps but not much more than that as the ball would have slowed down significantly before it reaches the chrony. With a large (compared to an air rifle), high pressure muzzle blast, the chrony will have to be at least 3' away I imagine.

You really should build a hybrid if you want definitive supersonic results.
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Unread postAuthor: High-PSI » Sun Dec 11, 2011 8:16 pm

Yup, I totally agree.

Actually, my Chrony needs about 6 feet away to give a decent reading.

What I will be firing most often are chrome steel balls wrapped in small scraps of fabric as barrel seal/wadding. However, even those are listed at 1,100 fps in GGDT at 600 psi. I bet that is way off. But, then again, 600 psi is a lot of pressure and my valve CV is 14 (high for a 1/2 inch cannon).

I just want to make sure I am maximizing everything. I know my compressor is good for over 800 psi. I have a 1,500 psi guage coming to hydro test my tank. Once I test it and feel confident, I will test the gun at 800 psi.

I am not after ultimate power as much as maximizing what can be attained with a given technology. I am not against hybrids at all. I am just committed to seeing this through. It is so quick and easy to air this small cannon up that I want to stick with compressed air for now.

That being said, it may be that a year from now I am pushing for mach 2 with a hybrid and getting frustrated that it is not powerful enough. :)

At this point, I am having a hard time pushing for more power, though. It is getting difficult to stop the projectiles inside my shop when I test the cannons. :D

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Unread postAuthor: jackssmirkingrevenge » Mon Dec 12, 2011 12:55 am

MrCrowley wrote:If I remember correctly, double the weight for the same velocity and you double the muzzle energy. Double the velocity for the same weight and you quadruple the muzzle energy.


Yup.

Image

Usually pneumatics are more efficient and get less velocity but more muzzle energy with a heavier projectile though, so the GGDT predictions are rather odd.
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Unread postAuthor: pneumaticcannons » Mon Dec 12, 2011 7:26 am

dayum! thats really nice! know i'm too ashamed to post my 20 minute stock I made for my hybrid :?
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Unread postAuthor: High-PSI » Thu Dec 15, 2011 8:36 pm

Here is a picture for scale for you. I had to mount the scope a bit higher than I wanted to get the line of sight correct. But, as you can see from this picture (along with my bald head:)), the tank makdes a perfect cheek rest. The gun is very comfortable and easy to hold. Oh, the long aluminum barrel is a little flexible. So, I am ordering a 1/2 inch seamless, stainless barrel for it.

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Unread postAuthor: evanmcorleytv » Thu Dec 15, 2011 8:39 pm

Looks GREAT!! And that grip looks madly comfortable! Would you let me mold the stock?
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Unread postAuthor: jackssmirkingrevenge » Thu Dec 15, 2011 9:58 pm

Looks great!

High-PSI wrote:Oh, the long aluminum barrel is a little flexible. So, I am ordering a 1/2 inch seamless, stainless barrel for it.


This is where I usually step in and suggest sleeving the barrel, and drilling a few holes in the muzzle end in order to have the sleeve take the edge off the muzzle crack ;)
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Unread postAuthor: High-PSI » Fri Dec 16, 2011 10:27 am

Not a bad idea.

I kind of like the muzzle crack, though. It is impressive to those who have no clue what a high power air gun can do.

Of course, the true test is absolute power. I have a feeling this thing will have similar power to a .45 handgun. We shall see.

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Unread postAuthor: jackssmirkingrevenge » Fri Dec 16, 2011 10:58 am

High-PSI wrote:I kind of like the muzzle crack, though. It is impressive to those who have no clue what a high power air gun can do.


Hehe don't worry, it won't be "mouse fart" quiet - besides, the destruction caused by a quiet weapon tends to leave a greater impression ;)

Of course, the true test is absolute power. I have a feeling this thing will have similar power to a .45 handgun. We shall see.


With a "perfect" valve and running at 800 psi with a 1/2" lead ball, GGDT suggests around 260 ft/lbs, not exactly 45 ACP but definitely in 38 special or 9x18mm makarov range ;)
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Unread postAuthor: High-PSI » Fri Dec 16, 2011 4:58 pm

OK, when I run GGDT, it shows 373 ft/lbs. I must be doing something wrong.......

Oh, one thing, remember, I am using a .622 inch barrel, not .5 inch. That may be the difference.

At any rate, I am excited to see how this thing will perform. I have 200 1/2 inch steel balls for it. I found the perfect fabric to use as wadding that makes the balls fit snug, but not tight into the barrel.

My schedule is busy for the next couple weeks. So, I am not sure how much work I will be able to do on it.

Matt

Edit by Mod: Double Post

Oh, wait till you see my next project. I have one of these valves in 1-1/4" bore (28CV) that I will be firing through a 1 inch bore barrel. That cannon will use everything I have learned from my big 2 inch and this little 1/2 inch gun to (hopefully) make a high velocity, high power pneumatic. My 2 inch has too much kick for my shoulder at high pressures, and this little gun will be fun, but not as impressive as a pneumatic can be. The 1 inch should be a good compromise of the two.

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Unread postAuthor: MrCrowley » Fri Dec 16, 2011 5:15 pm

Surely you wouldn't want to sink more money in to a design not that different from your other two? Unless it's not going to cost you much, I would advise you against it. The two launchers you have at the moment cover the ammo bases pretty well; your large cannon can fire anything from golf balls to tennis balls or larger and your small one handles the ball bearings and fishing sinkers etc,.

I don't think it will be long before you're looking for new targets to shoot, or new projectiles, anything that will stimulate your continued interest in the two cannons. After awhile you'll be wanting to make a combustion, hybrid or a radically different pneumatic cannon (perhaps a 3" porting piston valve?), you may as well save the money you would spend on the third pneumatic for a future design (that is, unless your third pneumatic wont cost much to make).

Then again, you could make it so the chamber and barrel of your new pneumatic could be used on a future hybrid design.

Just my $0.02.
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Unread postAuthor: Gun Freak » Fri Dec 16, 2011 6:28 pm

I totally agree with Crowley, you can do much better! Honestly this is just a simple pneumatic that uses high pressure and expensive things! Not saying it isn't kick ass though!
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Unread postAuthor: High-PSI » Fri Dec 16, 2011 6:36 pm

I agree it is a simple design. That is probably why I am having good success with them.

The only reason I would build another is because I have the other valve (already modded with a pilot valve and trigger) sitting there on the bench along with the tank, barrel, and even CNC machined barrel clamps (production items from my bike drive systems). So, I have 85% of what I need sitting there. It kind of seems like a waste to not build something with them. :)

However, I am totally open to building something new.

What are your thoughts on what I should build?

Matt
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Last edited by High-PSI on Fri Dec 16, 2011 7:48 pm, edited 1 time in total.
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