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HPA pistol musings........

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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HPA pistol musings........

Unread postAuthor: High-PSI » Sun Apr 29, 2012 7:24 am

Hey Guys,

I am beginning to design (in my head) a 800-1,000 psi pistol. My innitial thoughts are a 3/4" bore barrel with a scratch built piston valve machined from a block of aluminum, and using the grip as the tank to keep the size of this thing down. The barrel would be 12 inches long. At this kind of pressure, even that short barrel shows muzzle energy up near 200 ft lbs. with relatively high muzzle velocity. Should have quite a kick.

Anyway, there is not a whole lot being done with pistols for obvious reasons. So, I wanted to maybe give it a shot (pun intended :wink: ).

I was hoping to mechanically pilot the valve with some sort of [extremely strong] trigger activated gate to keep the size of this thing down.

This is just in the thinking about it stage right now. I wanted to get your thoughts on this.

Matt
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Unread postAuthor: Brian the brain » Sun Apr 29, 2012 8:53 am

My first sawed-off was about that size.
It can be done but if you are going to get a block machined...I say there are easier ways.
I'd keep the amount of pressurised fittings/connections to a minimum as building compact means you'll need high pressure.

I have been planning to build my next project around a chamber sealing valve triggered by a hammervalve/ inline hammer.
An inner reservoir tube forms the seat for the piston.

With a rotating hammer you could keep it all quite compact and all the parts that hold pressure can be kept in a single tube.Barrel rides on top of that.
If you like you can have the breechblock machined/ fitted with attachment rails.

I prefer over/under in a tight configuration over a pressurised grip any day.
A long grip looks weird so there is only so much reservoir available.
A T-piston valve on top means the pilot is pointing away from your triggerfinger.
You'll have to work your way around the grip-reservoir to pilot the valve, either through a mechanical solution or by plumbing your way around.
Both methods result in some sort of bulk sticking out over the back of your hand.

Another way to get a powerful yet compact pistol is to use a hollow piston wich holds the air/gas running almost the entire reservoir length.
Sorta like a toolie piston but flipped inside out.

Pilotvalve will be positioned at the opposite (muzzle)end .
This means your seal is just a rubber disc on the breechside wich shortens the distance between the backend of the outside of the reservoirtube and the starting position of your ammo to an absolute minimum.

Air transfers from reservoir to the barrel very close to the rear of the gun effectively giving you the longest functional barrel versus practically no bulk in the back.

The path from triggerfinger to pilotvalve is unobstructed.
So either plumb back from the muzzle to the triggerfinger or solve it mechanically with a simple rod.
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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: jackssmirkingrevenge » Sun Apr 29, 2012 9:48 am

jesus tapdancing christ brian, I expect a link to this!

http://www.spudfiles.com/forums/high-po ... t6725.html

here's one I almost completed:

http://www.spudfiles.com/forums/12-bore ... 21346.html

some other pistols on here:

http://www.spudfiles.com/forums/el-bamb ... 16545.html

http://www.spudfiles.com/forums/coaxial ... 10937.html

http://www.spudfiles.com/forums/high-pr ... 17852.html

After seeing what you did with that rifle, certainly looking forward to what you do with this idea!
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Unread postAuthor: Brian the brain » Sun Apr 29, 2012 10:20 am

Out of all of the links you provided the only ones that are really compact are coaxials.
My pirate pistol was pretty compact but still, about half of the length consists of pilotvalve and handle.

I was hoping to offer some ideas to get rid of the bulk a breechside valve usually brings.

The idea in this picture puts the pilot at the muzzle end.
Simply replace the pop-off section by another valve to get single fill/single shot.
The grip can now be located to the far side of the breech end and the trigger can be hooked up to the pilot in a straight unobstructed line.

Image
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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 10:56 am

I considered a coaxial. That may indeed happen. The increased diameter would be strange for asthetics, though. But, you are correct that they are most compact.

Matt
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 29, 2012 11:02 am

High-PSI wrote:The increased diameter would be strange for asthetics, though.


Depends on your aesthetic inspiration ;)

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Unread postAuthor: Brian the brain » Sun Apr 29, 2012 11:17 am

A 3/4" bore kills compactness.

Perhaps you could do a semi-coax.
A reservoir tube over the barrel AND a T-off to the grip to provide enough volume.
If you would use some sort of slide over the outertube as the hammer.

think of a capped off tube ( with a cutout for the grip) that is sprung forward to hit the pilotvalve.
A trigger could then hold it in cocked position with a simple notch in the bottom of the slide.
A hammerspring could then be added somewehere in front of the grip aswell.

The backpart of the slide could be cut out as you see fit to make it look nice and the cap could be replaced by a bolt running through the tube.
whatever it takes to hit that hammervalve.

As long as the travel of the slide is not too big it should look quite cool.
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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 11:24 am

Oh, lastly, as for my asthetic preference on handguns, I prefer the look of a decent semi-auto. I do not like the entire barrel and firing mech located ahead of the grip. Odds are, the entire gun would be about 14 inches long with the grip centered about 35 or 40% of the distance from the rear of the gun so the valve would be at the rear of my wrist area and the barrel would begin at my rear most thumb knuckle. This makes the gun far easier to handle and allows a longer barrel without being so unwieldy to use.

I hope I am articulating myself properly.

Oh, the entire valve and grip would be machined from aluminum billet in my shop. The concern I would have is sealing the tank from the barrel in a coaxial arrangement. No welding would be done as this is aluminum. I would machine an aluminum spacer to seal the nose of the tank to the nose of the barrel. At 800+ psi, sealing could be tough.

So, 200 ft lbs of muzzle energy would be awesome in a handgun. :D

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Unread postAuthor: High-PSI » Sun Apr 29, 2012 11:28 am

Brian the brain wrote:A 3/4" bore kills compactness.

Perhaps you could do a semi-coax.
A reservoir tube over the barrel AND a T-off to the grip to provide enough volume.
If you would use some sort of slide over the outertube as the hammer.

think of a capped off tube ( with a cutout for the grip) that is sprung forward to hit the pilotvalve.
A trigger could then hold it in cocked position with a simple notch in the bottom of the slide.
A hammerspring could then be added somewehere in front of the grip aswell.

The backpart of the slide could be cut out as you see fit to make it look nice and the cap could be replaced by a bolt running through the tube.
whatever it takes to hit that hammervalve.

As long as the travel of the slide is not too big it should look quite cool.


Agreed.

The main reason for a larger bore than .62 (1/2 inch pipe) would be muzzle energy. But, as you mentioned, it kills compactness.

Of course, this thing could be build as a freakin MEAN handgun, as in, a bit bigger and badder than a typical handgun. Howver, making something look crazy means it MUST perform crazy or people will be underwhelmed when they see it.

Hmm, the muzzle crack of 800+ psi coming out of a chort barrel will be plenty loud too.

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Unread postAuthor: High-PSI » Sun Apr 29, 2012 11:28 am

OOps, double post.........
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Unread postAuthor: Brian the brain » Sun Apr 29, 2012 11:49 am

Your pressurevessel welding skills could really come in handy.

Not many members could pull my proposed idea off..
As so happens it does need some part of it sticking out past the grip.
I'm quite sure there are numerous improvements possible but ...
Here is the basic idea:
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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 12:12 pm

Looks very good. I like it! Many of my thoughts are fleshed out in your design.

Hmm, I guess the only real question for me is firing mechanism. A purely pneumatic pilot system sure is easy to acheive and does not require cocking. But, it is not as compact and does not lend itself to pressures above 600 psi (or it becomes much more difficult to use reliably above that pressure) at least from my experience.

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Unread postAuthor: High-PSI » Sun Apr 29, 2012 12:40 pm

OK, I think I have a bit ironed out;

If I were to build this gun right now, I think I would go with a piston coaxial. A diaphragm coax is a touch shorter, but I do not want to trust a diaphragm with this much pressure. I think steel would be a good option. The tank face would be machined and welded. The rear would have a flange that would be welded with a series of holes drilled and tapped to bolt the rear of the chamber/piston valve housing to.

I think a 1 to 1 tank to barrel ratio would be best for this due to space constraints as well as efficiency. I like coaxes for the nrear zero dead space as well.

Hmm, I hate when I get a decent idea in my head while I have not finished other projects yet.........

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Unread postAuthor: jackssmirkingrevenge » Sun Apr 29, 2012 12:50 pm

High-PSI wrote:So, 200 ft lbs of muzzle energy would be awesome in a handgun


You would have to to have to go hybrid for that, and in a compact pistol package that would mean pretty high mixes.
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Unread postAuthor: Goats spudz » Sun Apr 29, 2012 2:08 pm

have you ever thought of 3000psi and valveless?
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