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"valveless" cartridge concept

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"valveless" cartridge concept

Unread postAuthor: jackssmirkingrevenge » Tue Jul 13, 2010 8:48 am

I've flirted with the idea of a "valveless" cartridge before, the performance benefits are obvious - zero opening time, instant full flow - however the projectile release mechanism would invariably be an intricate system which would not lend itself to mass production.

Here's conceptual alternative that might be more practical, the diagram represents the launcher seen from above. The cartridge is a simple tube with a seal on both ends (silicone tubing or similar) with the projectile being retained in the front seal.

The launcher itself has a blowback action, the bolt comprising a spring loaded needle-like tube which fits into the base of cartridge. The trigger is a ball valve or similar, feeding HPA through the injector into the cartridge until enough pressure is reached to "pop" the projectile out of the seal. Since the injector has a very small diameter, it will not take a very hard spring to keep it in place.

When the projectile pops, the rapid overpressure in the breech should be enough to blow the cartridge out, striking the ejector and exiting via the ejection port. This allows a new cartridge to feed from the magazine and so the cycle continues.

The benefits compared do this coaxial design include cheaper and easier construction due to the lack of internal barrel and filling valve, which also means lower weight as well as over 200% of the coaxial's internal volume for the same external dimensions. All of these factors give the design a much better chance of functioning effectively as a true blowback semi/auto design.

Any thoughts?
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Unread postAuthor: spudtyrrant » Tue Jul 13, 2010 9:16 am

hey you have a picture of me :lol: , but anyway.... the design looks good, it will just need to be really precise if you make it exactly like that, i would put a cone shaped seal on the back of the cartridge to insure it lines up correctly. also, WHERE'S THE EPOXY, IS THAT A BRASS CAP I SEE!?!?
:shock:
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Unread postAuthor: POLAND_SPUD » Tue Jul 13, 2010 9:41 am

no offence this is probably the most ridiculous design you posted...

I am getting the impression that you want to build it becasue you want to see flying brass :D
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Unread postAuthor: jackssmirkingrevenge » Tue Jul 13, 2010 10:03 am

spudtyrrant wrote:I would put a cone shaped seal on the back of the cartridge to ensure that it lines up correctly


That's the idea of the cone-shaped needle tip ;)

WHERE'S THE EPOXY, IS THAT A BRASS CAP I SEE!?!?


Hehe don't worry, the end caps would be epoxy, I just wanted the cartridge body to be one colour on the diagram for the sake of clarity.

POLAND_SPUD wrote:no offence this is probably the most ridiculous design you posted...


Any particular reason?
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Unread postAuthor: POLAND_SPUD » Tue Jul 13, 2010 10:16 am

Any particular reason?
in what way is it better than a valveless cloud ?? it's like a valve less cloud but it has lower mag capacity and a few extra parts that will increase the chance of it failing by a factor of 42

lol... don't tell me you got it on your 6th birthday... well at least that would explain a lot :D
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Unread postAuthor: ramses » Tue Jul 13, 2010 10:20 am

that would explain the brass cartridges...


It might be less work to put the seal on the needle, rather than the cartridges. This would allow you to use any handgun cartridge after adding the tube to the front to seal the projectile. Simply remove the primer for the back port!



you should probably have a sturdy needle with better support, because when the cartridge hits the ejector, it will want to push the needle off to one side (top in this drawing).


Nice Seal :D
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Unread postAuthor: inonickname » Tue Jul 13, 2010 10:48 am

Oh come on Jack..that filling needle at least needs to be machined...I'll do it for a nominal fee :P

In theory it's workable but could very well be a PITA.
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Unread postAuthor: jackssmirkingrevenge » Tue Jul 13, 2010 11:39 am

lol... don't tell me you got it on your 6th birthday... well at least that would explain a lot :D


5th actually, hours of fun for all the family :) you can imagine my disappointment later in life when I discovered that in the real world, they actually come in a very limited range of colours :roll: :D

In what way is it better than a valveless cloud ?? it's like a valve less cloud but it has lower mag capacity and a few extra parts that will increase the chance of it failing by a factor of 42


For starters, flying brass - One way to emphasize More Dakka, or at least how powerful a weapon, is showing all the bullet casings being ejected out of that gun. - that alone is a good enough reason for me :D I prefer a 10 round magazine and ejecting shells as opposed to a 1000 round hopper's worth of BRAAAAAAPPP!!!

It will also make semi-auto much easier to achieve, and allow the use of non-spherical projectiles such as airgun pellets.

It might be less work to put the seal on the needle, rather than the cartridges. This would allow you to use any handgun cartridge after adding the tube to the front to seal the projectile. Simply remove the primer for the back port!


Interesting thought, though it will increase the diameter of the moving part, meaning more force on the needle (Injector needle, it's supposed to be a subtle reference :roll:) and a stronger spring will be needed to keep it in place...

Another option might be to use an actual syringe needle that pierces a rubber cartridge base, but I fear flow might be inadequate and cause too much lag between trigger pull and firing.

you should probably have a sturdy needle with better support, because when the cartridge hits the ejector, it will want to push the needle off to one side (top in this drawing).


With an adequate spring setup, and maybe a weighted injector, the hope is that the cartridge will stop while the injector will continue moving back under its own inertia.

Oh come on Jack..that filling needle at least needs to be machined...I'll do it for a nominal fee


If I could afford it, I would just have a bunch of 3000 psi coaxial cartridges machined...
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Unread postAuthor: ramses » Tue Jul 13, 2010 12:00 pm

By sturdy, I meant aluminum, steel, SS, something that is not epoxy.

The needle won't necessarily have more surface area exposed to the pressure. The rubber sealed against the outside of the cartridge wouldn't see the pressure. But if you want to double the amount of work required for each cartridge... well don't because I want a brass shower sooner rather than later.

The last time I visited that site you linked to, I crashed my browser by loading over 600 tabs. (or was it over 9000)
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Unread postAuthor: jackssmirkingrevenge » Tue Jul 13, 2010 12:59 pm

ramses wrote:By sturdy, I meant aluminum, steel, SS, something that is not epoxy.


I was thinking of the 2mm O/D 1mm I/D brass tubing I was using for my pico BBMG barrels.

ramses wrote:The last time I visited that site you linked to, I crashed my browser by loading over 600 tabs. (or was it over 9000)


So you said ;)

ramses wrote:The needle won't necessarily have more surface area exposed to the pressure. The rubber sealed against the outside of the cartridge wouldn't see the pressure.


How exactly?

I could go for a balanced injector:
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Unread postAuthor: ramses » Tue Jul 13, 2010 4:04 pm

jackssmirkingrevenge wrote:
ramses wrote:The last time I visited that site you linked to, I crashed my browser by loading over 600 tabs. (or was it over 9000)


So you said ;)



OMG search using FREAK :D :D :D
can I ask what keywords you used? And how you remembered them?


Anyway, if you think about it, if the rubber sealing face is doing it's job, it is not subjected to air pressure on the front. That's why we use the OD of a barrel port to calculate the area ratio, part of why floating O-rings actually seal, etc. Basically, if it's sealing, there is no room for the air pressure to push on it. Come to think of it, it may actually reduce the surface area, because if you used a tube in the cartridge to seal it, the front of the wall of the injector needle would be subjected to pressure, but if you sealed the face, you could have only a sliver of rubber
overlap the hole. If the hole in the rubber was too big, you would have more SA exposed.

The balanced injector would be a huge PITA to make for the cartridges.

Even if it did increase the required spring force, so what? (within reason)

Will you attempt to close the air supply to the injector needle, or just let it flow. I suppose airflow through a 1mm port is negligible :wink: . One of the advantages of working at that scale.

If you wanted to be really air efficient, you could construct a blow-forward bolt with the injector needle as the bolt. By designing the bolt (needle), you could use that as a spring. Spring force would be low when pressure in the cartridge is low, unless the flow restriction is the needle (which is probable).

with a 6mm maximum, diameter breech, you have a 35 lb spring force. Depending on upstream flow restrictions, the spring response will be fairly constant (not linear like a spring might be)

You might not need to seal the breech, but you will have to keep the gap to .785 mm^2, or you'll be wasting more air than before.
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Unread postAuthor: jackssmirkingrevenge » Tue Jul 13, 2010 11:18 pm

ramses wrote:OMG search using FREAK :D :D :D
can I ask what keywords you used? And how you remembered them?


Well I happened to remember that the last time I linked to tvtropes was to the "Gatling good" article, et voila ;)


Anyway, if you think about it, if the rubber sealing face is doing it's job, it is not subjected to air pressure on the front. That's why we use the OD of a barrel port to calculate the area ratio, part of why floating O-rings actually seal, etc. Basically, if it's sealing, there is no room for the air pressure to push on it. Come to think of it, it may actually reduce the surface area, because if you used a tube in the cartridge to seal it, the front of the wall of the injector needle would be subjected to pressure, but if you sealed the face, you could have only a sliver of rubber
overlap the hole. If the hole in the rubber was too big, you would have more SA exposed.


Forgive me for being a bit thick but I still don't get it, peectures?

Even if it did increase the required spring force, so what? (within reason)


Moar spring force, less chance the cartridge will blow back, ergo moar spring force bad.

Will you attempt to close the air supply to the injector needle, or just let it flow. I suppose airflow through a 1mm port is negligible :wink:


Not as negligible as one might think at 800 psi, I figure the extra air input will help my blowback aspirations :D

If you wanted to be really air efficient, you could construct a blow-forward bolt with the injector needle as the bolt. By designing the bolt (needle), you could use that as a spring. Spring force would be low when pressure in the cartridge is low, unless the flow restriction is the needle (which is probable).


Food for thought, thanks :)

Edit: potential variation with a blow-forward injector, spring free but probably limited to semi-auto, unless the cartridge develops enough blow-back force to drive the injector back while the the air is still pushing on the piston from the feed side.
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Unread postAuthor: ramses » Wed Jul 14, 2010 9:31 am

jackssmirkingrevenge wrote:
ramses wrote:OMG search using FREAK :D :D :D
can I ask what keywords you used? And how you remembered them?


Well I happened to remember that the last time I linked to tvtropes was to the "Gatling good" article, et voila ;)


nice. :!:

Moar spring force, less chance the cartridge will blow back, ergo moar spring force bad.


fair enough.

Not as negligible as one might think at 800 psi, I figure the extra air input will help my blowback aspirations :D


true. you potentially loose that with the blow forward bolt.


Edit: potential variation with a blow-forward injector, spring free but probably limited to semi-auto, unless the cartridge develops enough blow-back force to drive the injector back while the the air is still pushing on the piston from the feed side.


I don't think it would eject in semi-auto. the pressure would be gone out the barrel, and the needle would just be dumping .785 mm^2 worth of air out the barrel by way of the cartridge.

Just so you know, the blow forward bolt you drew won't cut off air flow.


pictures soon.

Edit: pictures here.
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Unread postAuthor: Ragnarok » Wed Jul 14, 2010 9:51 am

ramses wrote:I don't think it would eject in semi-auto.

It should do. It's pretty much exactly a blow-back system.

In fact, I think it would probably eject very violently. If you look, after it starts moving back, the entire frontal area of the cartridge is exposed to pressure, which means there'll actually be more force on the cartridge than the projectile.

It may actually be necessary to add some mass to the injection needle to give it more inertia. Not only to slow the ejection, but also to slow the needle's return (to ensure that the next cartridge has moved into place in time).
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Unread postAuthor: ramses » Wed Jul 14, 2010 11:07 am

Ragnarok wrote:
In fact, I think it would probably eject very violently. If you look, after it starts moving back, the entire frontal area of the cartridge is exposed to pressure, which means there'll actually be more force on the cartridge than the projectile.


Exactly, but then it wouldn't be limited to semi auto. I was saying ( and this was not even stated by me, so I guess I was thinking) that if it was limited to semi auto like he said, it wouldn't cycle. Personally, I think it's work, and I demand videos as soon as it does :D
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