Valveless Dump-valve Idea

[Xamllew]

Hey guys, I've been thinking about starting a small project based on an idea I had one day at work while bored. The concept is simple, an airgun with no valve, instead a round projectile is locked against the mouth of the air chamber to block air from reaching the barrel, the projectile is always pushed against but unable to move, when fired, the mechanism unlocks allowing the pressure to act against the ball.

Now there are probably a lot of cons to this idea, obvious drawback is this has to be loaded in order to be pressurized which is a major safety hazard, likely will have to be muzzleloader as the ball will have to be pushed past a strong locking lug inside of the barrel, it can never be more than a single shot dump valve...BUT on the other hand this would hypothetically allow for zero valve open time and a valve opening nearly the size of the projectile.

Here's an MS Paint masterpiece to clarify how this might be achieved

Green is the lock which slides up into the barrel after the ball to lock the ball in, further mechanisms would ensure that the only way this lock could ever move is a deliberate squeeze of the trigger, a large O-ring ensures a snug airtight fit. Let me know what you fellas think.

[jackssmirkingrevenge]

Now there are probably a lot of cons to this idea, obvious drawback is this has to be loaded in order to be pressurized which is a major safety hazard, likely will have to be muzzleloader as the ball will have to be pushed past a strong locking lug inside of the barrel, it can never be more than a single shot dump valve...BUT on the other hand this would hypothetically allow for zero valve open time and a valve opening nearly the size of the projectile.

The biggest drawback that maybe isn't so obvious is the amount of friction on the locking mechanism that would make it very difficult to open unless you're using very low pressure or a small diameter projectile.

Here's a 0.22" cartridge prototype I had made a while back:





Even at 100 psi, it took quite some effort to open:

[youtube][/youtube]

Here's an alternative configuration, somewhat more complex but built into a balanced spool that should cancel out the friction, never tried it though:

a large O-ring ensures a snug airtight fit

The way you drew it, it seems that the o-ring would blow out with the projectile, needs some thought

[Xamllew]

Now there are probably a lot of cons to this idea, obvious drawback is this has to be loaded in order to be pressurized which is a major safety hazard, likely will have to be muzzleloader as the ball will have to be pushed past a strong locking lug inside of the barrel, it can never be more than a single shot dump valve...BUT on the other hand this would hypothetically allow for zero valve open time and a valve opening nearly the size of the projectile.

The biggest drawback that maybe isn't so obvious is the amount of friction on the locking mechanism that would make it very difficult to open unless you're using very low pressure or a small diameter projectile.

Here's a 0.22" cartridge prototype I had made a while back:





Even at 100 psi, it took quite some effort to open:

[youtube][/youtube]

Here's an alternative configuration, somewhat more complex but built into a balanced spool that should cancel out the friction, never tried it though:

a large O-ring ensures a snug airtight fit

The way you drew it, it seems that the o-ring would blow out with the projectile, needs some thought

Those are interesting designs, do you have a link to where I can see more information and do you have any other valveless designs?

On the subject of friction being a problem with opening, this issue is solved in some machines with a huge amount of friction, for example, ye olde crossbows simply by having a long trigger which gives a lever advantage against the friction from an immensely strong bow, I'm wondering if the same could be done here.

Another option would be to have the locking piece pivot instead of slide into place, meaning when unlocked it would just be pushed aside by the projectile rather than have to slide out of the way.

And thanks for spotting that mistake with the O-ring.

[jackssmirkingrevenge]

Those are interesting designs, do you have a link to where I can see more information and do you have any other valveless designs?

Here are some threads you might want to scroll through:

http://www.spudfiles.com/forums/valvele ... t8912.html

http://www.spudfiles.com/forums/valvele ... 11954.html

http://www.spudfiles.com/forums/valvele ... 12569.html

http://www.spudfiles.com/pneumatic-cann ... c8702.html

http://www.spudfiles.com/forums/valvele ... 21364.html

On the subject of friction being a problem with opening, this issue is solved in some machines with a huge amount of friction, for example, ye olde crossbows simply by having a long trigger which gives a lever advantage against the friction from an immensely strong bow, I'm wondering if the same could be done here.

That would definitely be a solution, a perfect mechanism to imitate would be the trigger of a spring airgun: