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Solving pump-pistol issues

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 » Fri Jan 11, 2013 4:13 pm

wyz2285 wrote:Well, a hybrid you need to care about the fuel, for a solid pneumatic, you just have to keep pumping, specially we are talking about a intergrated pump, for a hybrid you need to carry around a bottle of fuel and a syringe.


True... but my projects rarely if ever leave the testing area, so I don't take portability into consideration that much. Still, *proper* HPA should give close performance.

Here's a GGDT/HGDT model comparison between a 3000 psi pneumatic and 20x hybrid with similar barrel and chamber sizes firing similar projectiles.

Note that the hybrid gets similar performace even though maximum chamber pressure is around 20% of the pneumatic.
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Unread postAuthor: Brian the brain » Sat Jan 12, 2013 2:52 pm

So...

My idea now is to make a bore-pump flintlock style coax..and make it look right!
If I was ever to try a double barrel...this would be the time..

It could look just like a percussion cap doublebarrel shotgun..
Not entirely sure though..

I started some testing...the borepump worked just fine...the improvised endcap leaked though..

I'll lathe some brass parts soon..

Then I started wondering...
Did anybody try this yet:
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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 » Sat Jan 12, 2013 3:56 pm

Why not this, that way you don't have to dismantle the cartridge and replace the burst disk every time.
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Unread postAuthor: Brian the brain » Sat Jan 12, 2013 4:39 pm

With one spring keeping the piston and poppet in place...I knew you'd say that. :D
The way you portrayed it will have the poppetthingy sqeeze off the O-ring..

I realised I should have drawn the hammervalve type in the first place after I uploaded it.
The reason I didn't change it is because with a sharp enough spike, you'd need less force to hammer it at 80 bar+

The "gun"that would fire the cartridge would also be evidently different from a firearm, wich would be smart to avoid a misunderstanding about it's legality.


It should also have a ridge to extract the cartridge from ., perhaps.a..breakaction doublebarrel?. 8)
..and the cartridge is then put into the bottom of the pump so the plunger can stay in..

It would be nice if the concept could be put together with mostly standard parts..
Hmm...what could we use...?
Poppetvalve would be a screw..piston could be solid neoprene...



:D
I'm more interested in learning if anybody has tried something like it...and if it worked well..

I'd like a 8-10mm projectile and still shoot clean through a steel can.
Assuming the cartrigde would just about fill up 3/4 length of a slightly fattened sawed-off...
What kind of pressure would it take if the cartridge would be 22-25mm O.D.?

I'll start on a muzzleloader-flintlock style musket first.
Hmm...High pressure, relatively low volume ( for a spudgun).
I'll make an O-ringed reservoirbaffle that I can space with different length barrel sleeves.
Pressure will force it against the muzzle-plug and O-ring friction will keep it there.

This way I can easily change the desired reservoirvolume and power versus number of pumpstrokes and determine the point of deminishing returns.

Essentially this will tell me what size cartridge will do what.
Yep....seems like I got work to do...
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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: jean » Sat Jan 12, 2013 6:30 pm

@ brian you will start on a muzzleloader-flintlock style musket?

think about this
with the right diameters say 12mm pump rod and 8mm barrel i think you can reach 80ml @80bar..

pull the pump rod out-load from the back-push the pump rod in- ready to fire
may you can preload it with a second pump in the stock to double the volume
@jsr or as a hybrid...

see also my first post and clides design
http://www.spudfiles.com/forums/coaxial ... 12190.html

http://www.spudfiles.com/spudtech_archi ... t=minipump
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 13, 2013 1:44 am

Here's a thought which came to me as I was trying to sleep, a slightly unbalanced spool valve cartridge. The rear o-ring is slightly less diameter than the front seat so the pressure keeps it shut, but it can be opened with a couple of kg of force. The "hammer" would push the whole cartridge forward, a bit likethis. The spool face would be pressed against the breech face, voila.

A higher flow version of the Brocock...
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Unread postAuthor: Brian the brain » Sun Jan 13, 2013 6:16 am

Thanks for the input.. but I'm going for the pumprod-coax.
Mainly because of symplicity of concept, ease of construction and durability....and it fits the style perfectly.
It;s a good platform to jump to the cartridges.

When I started fiddling with the idea yesterday I remembered why results where bad in my first attempt, the Pirate( pistol).

I had used a solid rubber piston, without eq. hole...
That worked fine when pressurised through the ballvalve..so I already had a filling method and never put in the effort to solve the problem of rodpumping it.




Jeans idea had crossed my mind ( probably seen it before) but the barrel can only be fixed in position by adding an flow-obstruction in the reservoir.
Not the usual coax spacer..it needs to be chunky enough to keep the barrel in safely at extreme pressures.


JSR..I like the phantom breech effect.It doesn't move in far enough to touch anything yet magic somehow happens. LOL!

But I get it anyway...
My main objection is: where's the pop?

It's a blowgun in a pressurevessel...
If you'd make it longer to create more volume, your launcher becomes longer as well as the ammo is held at the tip.

I'm still convinced a coax piston type cartridge is best.
I might try the burst disk to pilot.
It will be less complex and very compact.

Only time will tell if it's too cumbersome to open the cartridge and drop in a precut aluminium disc.
( holepunch and redbullcan)

Piercing a burstdisc at high pressure isn't very hard
[youtube]http://www.youtube.com/watch?v=wAyjgpuuSD0[/youtube]
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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: jean » Sun Jan 13, 2013 7:19 am

Jeans idea had crossed my mind ( probably seen it before) but the barrel can only be fixed in position by adding an flow-obstruction in the reservoir.
Not the usual coax spacer..it needs to be chunky enough to keep the barrel in safely at extreme pressures.


sry for the hijacking
cant see the issue with the chamber
locking the barrel can be by a quick connect at the other (non chamber) end of the pump rod/tube like this
the chamber itself will be no longer than 1-2 cm no support for the barrel needed?!
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Unread postAuthor: jackssmirkingrevenge » Mon Jan 14, 2013 1:20 am

Brian the brain wrote:JSR..I like the phantom breech effect.It doesn't move in far enough to touch anything yet magic somehow happens. LOL!

But I get it anyway...
My main objection is: where's the pop?


Slammed hard enough, it would be effective - basically the same concept behind your brainchild :)

It's a blowgun in a pressurevessel...
If you'd make it longer to create more volume, your launcher becomes longer as well as the ammo is held at the tip.


The idea was to have it as a cartridge, still haven't given up on the idea :) my options on the table are either make a "proper" machined version of the valveless design which requires an external gas source, or focus on perfecting hybrid cartridges.

I'm still convinced a coax piston type cartridge is best.


The problem is that cartridges need to be small to be practical and "realistic", and a coax design automatically robs you of chamber volume for a given length and external diameter.

Piercing a burstdisc at high pressure isn't very hard


No doubt it will work well, it might just get annoying to have to change the disk every time. Still, a sawn off side by side uses much less ammo than a magazine fed "assault rifle" type launcher ;)
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Unread postAuthor: wyz2285 » Mon Jan 14, 2013 3:23 am

Anybody remembers larda's cannon size cartridge build? It's basically a coax piloted by a burst disc that gets pierced when firing, exactly like your idea btb. Can't find the link to the thread.
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Last edited by wyz2285 on Mon Jan 14, 2013 1:15 pm, edited 1 time in total.
CpTn_lAw wrote::D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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Unread postAuthor: jackssmirkingrevenge » Mon Jan 14, 2013 3:39 am

Damn you for bring it up, I can't fap at work :roll:

jean wrote:cant see the issue with the chamber
locking the barrel can be by a quick connect at the other (non chamber) end of the pump rod/tube like this
the chamber itself will be no longer than 1-2 cm no support for the barrel needed?!


Jean, are you suggesting that the barrel itself also move with the "pump", ie the yellow part of your diagram and the barrel are one piece?

My only problem with this concept is that it is single stroke, and therefore by definition low power.

The most powerful single stroke pneumatic I know of is the Parker Hale Dragon

This uses a lever for mechanical advantage and "only" manages 12 ft lbs of muzzle energy in 0.22".

If you want just want a fun little plinker like the HW40 that's fine, but personally I want to make deeper holes than that :)
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Unread postAuthor: jean » Mon Jan 14, 2013 12:48 pm

yes see the problem may
you can hgdt ggdt it for me i am in the hospital at th
e moment.

barrel 1m / 8mm
chamber 80 bar / 1cm2

why not preload the chamber?
on the other side 12ftp of energie are ok for me

maybe my next project

and yes barrel an pump rod one piece
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Unread postAuthor: jackssmirkingrevenge » Mon Jan 14, 2013 1:24 pm

jean wrote:why not preload the chamber?


It will work, but of course takes away the whole convenience of having a launcher with an integral pump...
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Unread postAuthor: jean » Mon Jan 14, 2013 2:28 pm

may a second pump in the muskets stock with one stroke and a diameter of 20-30mm
...only to double or tiple the volume pumping into the pump tube a volume of 80 ml up to only 1 bar seems easy

i will make a paint sketch if i am at home (3-4days)

edit ok 20-30mm isnt enough say 40mm and a strocke of 15cm
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Unread postAuthor: wyz2285 » Tue Jan 15, 2013 3:22 pm

40mm it's too large, you won't get high pressure with it.
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CpTn_lAw wrote::D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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