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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: waza8u » Tue Apr 24, 2012 9:22 am

could add some links of the parts you used on this awesome cannon or even some ebay links??? cheers
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Unread postAuthor: High-PSI » Wed Apr 25, 2012 5:36 pm

Hmm, not much to post in the way of links. The valve is made by Granzow. It is a one inch valve pilotted by a quarter inch direct acting valve with high wattage solenoid. The reducer from the valve to barrel is a simple black pipe reducer lightened and ported on the lathe. The barrel is an anodized aluminum sch 40 pipe. The scope is a basic muzzle loader scope I ordered from Bass Pro Shop. The rest of the gun was build from scratch including the tank.

Matt
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Unread postAuthor: High-PSI » Sat Apr 28, 2012 6:32 pm

I installed a diaphragm spring and that cured my valve issue. So, all is good. :D

The last minor bug to cure is the battery power. At 24 volts, the valve will not open above 550 psi. So, I will go to a 36 volt lithium pack. That should give it the power to open at 800 psi.

Anyway, this thing is quite shocking even at 500 psi. It is freaking LOUD and really packs a punch.

I am thrilled with how it turned out.

Here is a picture of the gun next to my 8 year old son for scale. It is a touch over 50 inches long and weighs a hair under 14 pounds.

Matt
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Unread postAuthor: HunterT » Sat Apr 28, 2012 7:47 pm

High-PSI wrote: The rest of the gun was build from scratch including the tank.


Just out of curiosity, how did you construct the tank?
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Unread postAuthor: High-PSI » Sat Apr 28, 2012 8:01 pm

The tank is MIG welded steel. The front and rear hemispheres are .120" thick as is the DOM (drawn over mandrel) tubing for the center of the tank. The front hemisphere was spun on the lathe to open up the front hole. Then the short steel pipe was chucked into the lathe and machined to literally snap onto the hemisphere. Once snapped together, the output pipe and hemisphere were welded from the inside, then the outside. Then the inside weld was ground to give a smotth transition for the air to exit the tank. The next step was to weld the entire tank together. Once welded together, the tank was pressurized and submerged to look for leaks (there is always one or two leaks in every tank I have ever welded). The leaks are found and drilled out. I have found it is FAR better to drill out a pinhole leak and weld the hole shut, than to surface weld the tank. After welding, the tank is repressurized to assure no leaks. Lastly, the tank was powder-coated flat black.

I still need to hydro test it. But, I have hydro tested tanks far larger than this with the same wall thickness to well over 600 psi without a problem. So, I am fine with this tank. However, once I get to the point of putting 800 psi into it, I want to make sure I test the tank and the valve to at least 1,200 psi to make sure everything will hold together.

It is wild working with HPA. Things that you take for granted with low pressure guns become an issue. For instance, the quick disconnects are more difficult to release up at 500+ psi that would normally release very easily at 100 psi........

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Unread postAuthor: HunterT » Sat Apr 28, 2012 8:27 pm

Ah, I figured that you had welded it. It seems to be pretty common thing to weld two hemispheres and a piece of tubing together to make a tank. I've considered welding up a tank similar to this one with a stick welder, but not knowing anything about welding pressure vessels, I decided against it.
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Unread postAuthor: jackssmirkingrevenge » Sat Apr 28, 2012 11:24 pm

That would be interesting to see in an advertising brochure, "smaller than a small child!" :D

Fantastic, but need videos!

High-PSI wrote:It is wild working with HPA. Things that you take for granted with low pressure guns become an issue. For instance, the quick disconnects are more difficult to release up at 500+ psi that would normally release very easily at 100 psi...


That's why HPA systems usually have a vent valve.
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Unread postAuthor: High-PSI » Sun Apr 29, 2012 6:07 am

I will get some videos when it is out being used at the range.

Matt
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Unread postAuthor: Brian the brain » Sun Apr 29, 2012 9:08 am

I ignored this topic as I thought you would've figured out what to build by now.
WOW.

Very well put together and superclean!
Love how you did the stock, that really shows your creativity.
And JSR is right, the off the shelf parts look right!

My only complaint could be..


NADA!
Can't even mind the muzzleloading!
Limits dead space while keeping your ammo options completely open.
Muzzleloaders are more fun per shot.
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Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: High-PSI » Sun Apr 29, 2012 12:24 pm

I appreciate the kudos.

I contemplated breach loading for obvious reasons. But, when all is said and done, I wanted to eliminate the complexity and possible air leaks from breach loading. I also wanted to maximize barrel length and minimize dead space (as you mentioned). Beyond all that, this was supposed to be a quick build. I had a target date to finish it. This limited my options for loading and for the trigger, hense the simple button trigger. Actually, the trigger feels very natural and correct. The grip to trigger distance feels spot-on.

Lastly, there is a certain element of "Theater" involved with muzzle loading. You set the gun on the rack, grab a steel ball, wrap it in some fabric wadding, stick it in the barrel, ram it all the way down...... Then there is the airing up; I attach the line and hit the compressor, I begin calling out "100 psi, 200 psi, 300, 400, 500, 600........). After that, I shut off a ball valve near the disconnect to reduce the line pressure blast. I pop the line off the gun and it is ready to fire. There are many steps involved. However, these steps actually go pretty quickly. I can refire this thing faster than my buddy can refire his muzzle loading hunting rifle. That being said, there is an anticipation involved in the reloading process of one of these guns. That is part of the fun, if you ask me. That is one reason I wanted to buld my own compressor from scratch as well. I was able to setup everything up exactly the way I want it.

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Unread postAuthor: High-PSI » Sat May 05, 2012 9:58 pm

Here is a video of the gan firing at 550 psi today.

http://youtu.be/JS4Htx21zIU

This shot was a 1/2 inch, 6 gram, chrome steel ball with terry-cloth wadding fired at a small refrigerator. It went clear through the entire fridge.

We fired the gun over and over and it was fine, until we went up to 600 psi. After repeated firing at that pressure, the main diaphragm blew. So, I replaced it and I will stay below 550 psi. To be honest, there was more noise, but no noticeable increase in muzzle energy at higher than 500 psi pressures. I think I am at the edge of what is possible with this style valve and gun layout that anything more than 500 psi is a waste anyway.

Enjoy the video!

Matt
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Unread postAuthor: jackssmirkingrevenge » Sat May 05, 2012 10:38 pm

Very nice :) some footage on target would be nice too, with these sort of muzzle energies you can do some impressive damage. Also interesting to explore different projectile options like shotgun rounds or sub-calibre penetrators.
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Unread postAuthor: High-PSI » Sun May 06, 2012 6:24 am

Yes, I agree.

The 1/2 inch bearing is smaller in diameter than the barrel (.622"). So, the wadding acts as a sabot. I have considered penetrating projectiles as well.

This thing is only a touch over 200 ft lbs of muzzle energy. My big 2 inch cannon is 2,600 ft lbs. So, the energy is low, but the muzzle velocity is very high.

The next thing is to experiment with heavier slugs. I will be machining a few projectiles that are twice the weight and try that. This thing is already penetrating every bit as far as I was hoping. The only shot that left me with any desire for more energy was one that hit the fridge at the very edge. The ball went through the front skin of the door, through the second sheet metal skin (door edge that has a wrap around metal skin), through the door gasket, and smashed the third layer of door skin at the very edge of the cabinet and sunk in aout 1/2 inch into the side metal. The metal at the edge of the fridge caught the ball and we recovered it. At that point, I was wishing it penetrated further. That being said, many handguns would have had roughly the same penetration.

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Unread postAuthor: jackssmirkingrevenge » Sun May 06, 2012 8:33 am

The fabric wadding is probably letting you down, UHMWPE, Nylon, Acetal or similar synthetic cups are a better idea if you have machining facilities.

Finding tubing which fits the barrel exactly and capping it with a heavy nosecone is another good way of making an ideal projectile, Petitlu shows a good example here.
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Unread postAuthor: High-PSI » Tue May 08, 2012 5:57 pm

OK, question;

Would you guys focus on accuracy and muzzle velocity (as far as doing work to improve this gun), or muzzle energy as in a larger bore?

This valve CV is 14. So, a 1 inch barrel is good with this valve and gun. GGDT shows a muzzle energy increase from my current 171 ft lbs to 428 ft lbs without making any additional changes other than going to a 1 inch barrel (even using the existing tank). The muzzle velocity will drop from 1,100 fps to 670 fps, though........

What are your thoughts?

Matt
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